SIP Communications for Dummies - Avaya

SIP Communications

FOR

DUMmIES‰

AVAYA 2ND CUSTOM EDITION

by Lawrence Miller, CISSP, andPeter H. Gregory, CISA, CISSP

Foreword by Alan B. Johnston

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SIP Communications For Dummies®, Avaya 2nd Custom EditionPublished byWiley Publishing, Inc.111 River StreetHoboken, NJ 07030-5774

Copyright © 2009 by Wiley Publishing, Inc., Indianapolis, Indiana

Published by Wiley Publishing, Inc., Indianapolis, Indiana

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Contents at a GlanceForeword............................................................v

Introduction.......................................................1

Chapter 1: SIP at a Glance .................................5

Chapter 2: The Case for SIP ..............................15

Chapter 3: How SIP Transforms Communications.............................................21

Chapter 4: SIP Interoperability .........................39

Chapter 5: SIP in the Contact Center .................47

Chapter 6: SIP and Intelligent Communications.............................................55

Chapter 7: Ten Reasons to Use SIP-Enabled Solutions by Avaya......................61

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Foreword

These days, in communications circles, Session InitiationProtocol, or SIP for short, is seemingly everywhere.

SIP is supported by practically every manufacturer of IPPhone, Gateway, Call Manager, and IP PBX. It is part of the IPMultimedia Subsystem (IMS). It is powering the fastest grow-ing VoIP (Voice over IP) residential and enterprise providers.It is a part of PC operating systems and has been enthusiasti-cally adopted by the open source movement. It is a key part offixed mobile convergence (FMC) and Unified communications.

Years ago, someone proposed a usage of SIP that was dubbed“SIP for Light Bulbs”! Don’t laugh, it may happen yet.

So what is SIP and why is the industry buzzing about it? Thisbook will tell you. What can you use SIP for? This book will tellyou that too. Why is SIP so important? You’ll find that here, too.

Before I leave you in the competent hands of the authors, I will add a few of my own answers here. SIP can be called a“rendezvous” protocol. That is, it allows endpoints on theInternet to discover, locate, negotiate, and establish sessions.What kind of sessions? Any kind of sessions. SIP is used toestablish VoIP (of course), video, gaming, text, call control,and others I’m sure I’ve left out. Recent extensions to SIP addin instant messaging and presence capability. What is pres-ence? This book will tell you, but presence stands ready torevolutionize enterprise communications the same way publicInstant Messenger networks have revolutionized consumercommunications.

Besides all these applications and uses, SIP is also generatingits own ecosystem. In the same way that the Internet openedup networking by displacing closed, proprietary networkingprotocols, SIP has opened up communications and displacedclosed and proprietary signaling protocols. It has created anentire ecosystem of interoperable and configurable devicesand services that is revolutionizing the way communicationsis done.

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Not bad for a little protocol developed in academia back inthe mid-1990s by such thinkers as Henning Schulzrinne andJonathan Rosenberg.

The authors have done an excellent job of explaining thewhat, why, and how of SIP in an understandable way. Enjoyyour read of SIP Communications For Dummies, Avaya 2ndCustom Edition!

Alan B. Johnston

September 2008

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Introduction

You’ve probably heard a lot about voice over IP (“VoIP”)or IP telephony in recent years. There’s a lot of industry

buzz and excitement about it, but you may be at a loss toexplain some of the benefits of VoIP for your business. Thereal advantage of VoIP and, more broadly, real-time IP commu-nications, is in the way it can transform your business com-munications architecture into an intelligent communicationssystem using a simple but powerful protocol, known as theSession Initiation Protocol, or SIP.

SIP makes it possible to easily connect the various compo-nents of an overall communications system, rapidly deployapplications, reduce costs, and improve customer service andemployee productivity by simplifying — or “SIP-fying” — yourorganization’s communications architecture.

Vendors are increasingly incorporating SIP into their variousIP communications products, including:

� Phones, gateways, proxies, and servers

� Softphones — software applications that provide voicecommunication capabilities on PCs, PDAs, and othermobile devices

� PBX (Private Branch Exchange) systems

� Instant messaging (IM) programs

� Videoconferencing systems

� Collaboration systems

SIP is an open protocol standard, with an active working groupon the Internet Engineering Task Force (IETF). Avaya and othermajor companies are active in the IETF SIP working group andin other industry groups, working to ensure that SIP-enabledsolutions work across businesses and enterprises with a variety of legacy, new, and evolving networking and telecommu-nications infrastructures and products to enhance and revolu-tionize the world of real-time business communications.

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SIP Communications For Dummies, Avaya 2nd Custom Edition 2

About This BookThis book explains SIP from both a business and a technicalperspective. You not only learn what SIP is and how it worksbut, more importantly, how SIP can benefit your entire organi-zation by transforming your real-time business communica-tions to gain a real competitive advantage.

Foolish AssumptionsWe assume that you have a keen interest in ensuring that yourcompany’s networking and telecommunications systems areup to the challenges of intelligent communications today andinto the foreseeable future. Regardless of your role withinyour organization, this book will help you quickly get up tospeed on how SIP can revolutionize real-time electronic com-munications for your business or enterprise.

How This Book Is OrganizedEach chapter of this book covers a different aspect of SIP. Youmay want to read the book cover to cover to gain a more com-plete understanding of SIP, or you may prefer to skip aroundto find out what you need, when you need it. But be fore-warned, we didn’t just save the best for last. This book ischock full of good information throughout!

� Chapter 1: SIP at a Glance provides a brief overview ofthe SIP protocol including some history about its develop-ment as an industry standard and its basic components.

� Chapter 2: The Case for SIP describes some of the keyfeatures of a SIP-enhanced IP communications infrastruc-ture and its potential benefits and advantages for busi-nesses and enterprises.

� Chapter 3: How SIP Transforms Communicationsexplains how SIP enhances customer service andemployee productivity, and how SIP scales from the

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smallest businesses to the largest enterprises. We covertopics such as presence, AORs, peer-to-peer SIP, SIPtrunking, the IP Multimedia Subsystem (IMS), and theservice-oriented architecture (SOA).

� Chapter 4: SIP Interoperability explains what vendorsare doing to make multi-vendor integration with SIP asstraightforward as possible. We also cover topics such ashybrid infrastructures, connection points, platforms andapplications, endpoints, the communications “ecosys-tem,” survivability, security, and federated presence.

� Chapter 5: SIP in the Contact Center describes how SIPtransforms your call center into a full-service contactcenter to help your business better serve its customers.

� Chapter 6: SIP and Intelligent Communications looks athow SIP continues to evolve and improve, incorporatingmore communications technologies and supporting moreenhanced communications capabilities.

� Chapter 7: Ten Reasons to Use SIP-Enhanced Solutionsby Avaya cuts straight to the chase — why your busi-ness needs SIP-enhanced communications and howAvaya can help!

Icons Used in This BookThroughout this book, we occasionally use icons to call atten-tion to material especially worth noting. Here is a descriptionof the icons you’ll encounter:

Some points bear repeating, and others bear remembering.When you see this icon, take special note of what you’reabout to read.

This icon highlights technical information that will eithermake your pocket protector curl or help you fall asleep!

If you see a tip icon, perk up — you’re about to find out howto save yourself some aggravation.

Introduction 3

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Where to Go from HereWhether you’re just hearing about SIP for the first time, con-sidering a SIP project, neck-deep in it, or looking to take yourexisting telecommunications infrastructure to another level,always keep your eye on the big picture. Avaya has keenvision and a strong commitment to SIP and unified communi-cations. Turn the page and discover for yourself why Avaya isa leader in intelligent communications.


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Chapter 1

SIP at a GlanceIn This Chapter� Defining SIP

� Playing nice with others . . . through standards

� Sketching out a simple SIP architecture

People have more options today for communicating witheach other than ever, yet we often have a harder time

getting through to anyone. We now have a dizzying array oftechnologies and communication devices, literally at our fin-gertips, that can deliver voice, text, and even video, in real-time. It seems everyone has too many devices, too manynumbers, and too little time.

Yet with more people more connected than ever before, anunintended and unexpected communications paradox hasemerged — in our quest to make it convenient for anyone toreach us anywhere, anytime, and any way, it has actuallybecome more difficult to simply communicate with eachother. Determining the best way to get in touch with your cus-tomers, clients, and partners at any given time can be a daunt-ing task, and letting people know how to get in touch with youat any given time is no easy feat, either. Simply put, communi-cation has become device-centric, not user-centric.

This chapter introduces SIP, a widely adopted industry stan-dard protocol that is helping businesses and enterprises of all sizes solve these issues and enhance communicationscapabilities.

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What Is SIP?Session Initiation Protocol (SIP, as in sipping from a fire hose ona hot day) is an open signaling protocol standard developedby the Internet Engineering Task Force (IETF) in cooperationwith many industry leaders, including Avaya, for establishing,managing, and terminating real-time communications overlarge IP-based networks, such as the Internet. Communicationsvia voice, video, or text (instant messaging), may take placeusing any combination of SIP-enabled devices, such as a soft-phone on a laptop computer, a wireless handheld device orPDA, a mobile phone, an instant messaging client on a desktopPC, or an IP phone with videoconferencing capabilities.

SIP is an application layer peer-to-peer communication pro-tocol for establishing, manipulating, and tearing down com-munication sessions. But, you can do a lot more with SIP thanjust setting up telephone calls. The protocol is extensible —meaning developers can easily write custom applications forSIP to accommodate video, instant messaging, and otheremerging communications media and features, using tools andprogramming languages, like Java, that are already familiar toInternet developers. Using SIP, simple-to-develop and quick-to-deploy custom applications can be easily integrated into yourcommunications sessions.

SIP is used to identify, locate, and enjoin parties who want tocommunicate using any peer-to-peer media type. However, SIPdoes not transport the media itself: That is handled by codecswithin the communications programs or devices.

SIP builds on a number of existing communications protocolsand has rapidly become the standard for service integration(how new services and applications are created and com-bined) within most large fixed and wireless carrier networks.Thus, SIP is positioned as a single unifying protocol that willtransform not only communications within an enterprise, butcommunications between an enterprise and its ecosystem ofcustomers, clients, partners, and suppliers. For businessesthat need to sort out and reconnect their current tangle of dis-parate communications protocols and programs, SIP is arefreshing solution that can simplify and enhance your com-munications capabilities.

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Setting the StandardAlthough you may not be familiar with SIP by name, it’s actu-ally based on many protocols that are widely used across theInternet and in many enterprise applications today. And, justas common standards and interoperability have been key tothe success of the Internet and IP networks, SIP is a widelyadopted standard that promotes interoperability and drivesdown costs in communications networks.

You’re probably already familiar with a protocol very similarto SIP — HTTP (HyperText Transfer Protocol) — yep, we affec-tionately refer to that bit before the “www” as “H-T-T-P, colon,slash, slash” when browsing to an Internet Web site. In effect,SIP is to intelligent, unified communications, as HTTP is to

Chapter 1: SIP at a Glance 7

What does SIP have to do with music?Absolutely nothing! But the originalIETF draft of the SIP protocol, pub-lished in February 1996, was titled“draft-ietf-mmusic-sip-00” — notquite as catchy as, say . . . SIP Com-munications For Dummies! Thosewild and crazy guys at the IETF gaveus “mmusic” instead — an acronymfor Multiparty MUltimedia SessIonControl.

Although SIP was originally the brain-child of the telephony industry, whichenvisioned a better way to set up andmanage telephone calls, the computerindustry saw the potential to revolu-tionize all real-time communicationswith SIP. Initially, SIP was developedas a means to invite people to largemultimedia broadcasts on theInternet’s multicast backbone, knownas “Mbone.” Mbone was used to

facilitate the distribution of streamingmultimedia content including educa-tional seminars, broadcasts of spaceshuttle launches, and riveting IETFmeetings.

Today, SIP enables a wide array ofservices and applications thatenhance real-time communicationsfor businesses and enterprises. Youcan find the latest core SIP specifi-cation in IETF RFC (Request forComments) 3261 (now simply titled“SIP: Session Initiation Protocol”),and it’s not just a one-hit wonder:Currently, some 289 RFCs related toSIP have been published, showingjust how much of a factor SIP is in thecommunications industry today —and will continue to be for tomorrowand beyond.

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information exchange on the World Wide Web (WWW) — itmakes the communications infrastructure transparent to end-users and enables ready access to many modes of communi-cation. Just as pointing your browser to an HTTP Web siteenables you to play a video, download a picture, or read text,SIP has been designed to support multimedia communica-tions in real-time.

SIP is modeled after HTTP, and in fact uses much of HTTP’ssemantics and syntax. Both SIP and HTTP use a plain text-based language. What does this mean for your business? SIP’smessages are easy to program and interpret, making it easierto achieve interoperability between disparate networks anddifferent vendor solutions, saving you money and enablingyou to rapidly deploy new applications to support your busi-ness and customer needs. SIP is also very modular and exten-sible (like XML, or the Extensible Markup Language), allowingfor integration with legacy systems and new and evolvingtechnologies. These properties make SIP an ideal protocol for implementing a standards-based unified communicationsnetwork.

Although the protocols are similar in their simplicity, SIP goeswell beyond the capabilities of HTTP, for example, by embed-ding intelligence in a communications session to sense themedia capabilities of an end device and the availability of auser to communicate.

The SIP standard is defined in RFC 3261 by the InternetEngineering Task Force (IETF). For anyone familiar with thebattle between Blu-Ray and HD DVD formats, the importanceof industry standards cannot be overstated. SIP has been awidely adopted industry standard for more than ten years.Additionally, several neutral consortiums, including SIP Forumand SIP Center, arrange meetings and events, such as SIPit,where companies with SIP-based hardware and software prod-ucts can test interoperability with other SIP-based products.This testing helps to promote smoother integration of SIP-based products in carrier and enterprise networks.

The IETF is a large, open, international community of networkdesigners, operators, vendors, and researchers concerned withthe evolution of the Internet architecture and its operation.


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Some vendors have gone above and beyond these efforts withactive SIP interoperability and ecosystem programs. In a well-run SIP ecosystem, devices and services obviously need towork together seamlessly, and the only way to absolutelyensure that they do is for vendors to test their SIP-based prod-ucts together. For example, Avaya has made a long-standingcommitment to establishing openness and interoperability for SIP through its Developer Connection program, which sup-ports software developers, systems integrators, and serviceproviders in testing interoperability and developing SIP-basedsolutions in conjunction with Avaya products and services.You can find more information about interoperability effortsin Chapter 4.

The potential impact of SIP goes beyond internal communica-tions within a business or enterprise. SIP has become a signal-ing standard for carrier networks. Service providers nowprovide SIP-based trunk services that can reduce costs andextend an enterprise’s SIP environment into the public net-work. The adoption of SIP for external connectivity will lead toa transformation in communications between an enterpriseand its ecosystem of partners, suppliers, and customers. SIPmay eventually become the unifying protocol for all real-timeIP-based communications. You can learn more about SIPtrunks, PSTN (Public Switched Telephone Network) and PBX(Private Branch Exchange) connectivity, and connecting dis-parate enterprise “islands” in Chapter 3.

SIP goes well beyond traditional telephony by facilitating anytype of peer-to-peer communication session, including instantmessaging, video gaming, voice and video conferencing, andcollaboration.

SIP is not designed to be a one-stop shop for all your protocolneeds. SIP is used to set up, manage, and tear down media ses-sions (for example, voice, text, and video). SIP works withother network protocols as well as application-layer technolo-gies to provide complete end-to-end functionality. One suchprotocol is the Session Description Protocol (SDP), which car-ries within it information about the session that you’re settingup (namely, the type of media, the codec to use, and the pro-tocol for actually transporting the media).


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Basic SIP ComponentsWhen you are ready to enhance your enterprise communica-tions with SIP, you’ll need to understand the basic buildingblocks that form the foundation of your new SIP-enabledenterprise.

User agentsUser agents (UAs) are applications installed on SIP endpoints,such as an IP phone, mobile phone, wireless device or PDA, ora laptop or desktop PC (see Figure 1-1), that interface betweenthe user and the SIP network. A UA can act as either a clientor a server. When sending SIP requests, the UA acts as a useragent client (UAC), and when servicing a request, it acts as auser agent server (UAS). A back-to-back user agent (B2BUA) isan application that acts as an intermediary between two par-ties, but appears as an endpoint to both parties — like a mid-dleman. It serves as both UAS and UAC simultaneously toprocess session requests.

Figure 1-1: Some typical SIP user agents.

[email protected]

Softphone

PDA

SIP Phone

Dual-ModeMobile Phone

Instant Messaging


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SIP devices can communicate directly if they know eachother’s URI (Uniform Resource Identifier) or IP address, butmore commonly, SIP servers are used in an enterprise net-work to provide an infrastructure for routing, registration, andauthentication and authorization services.

IP-based devices can identify and communicate with oneanother using IP addressing alone. However, in most cases,your network uses the Domain Name System (DNS) to estab-lish sessions with device names, which DNS translates into IPaddresses. Similarly, SIP devices frequently consult directoryservers (often by name), which provide endpoint addressesthat the devices then contact to set up a call.

SIP serversSIP servers provide centralized information and enablementservices in a SIP ecosystem. The core SIP servers and anoverview of their basic functions are described here.

� Registrar Server. When users come online, they need tomake sure that others are aware they’re available to takeand make calls. The Registrar authenticates and registersusers when they come online, and stores information onthe users’ logical identities and the communicationsdevices or physical entities (IP address) of the communi-cation devices they can use. The devices are identifiedby their URIs.

� Location Service. As users roam, the network needs tobe continually aware of their locations. The locationservice is a database that keeps track of users and theirlocations. The location service gets its input from theregistrar server and provides key information to theproxy and redirect servers. A SIP proxy or redirect serveruses this information to obtain the mapping from logicalSIP addresses to physical SIP addresses, so that commu-nication sessions can be properly established and maintained.

� Redirect Server. If users are not in their home domains,sessions need to be redirected to them. The redirectserver maps a SIP request destined for a user to the URI ofthe device “closest” to the user. For example, if a call isdestined for [email protected] and the user is


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on the road, the company’s redirect server may reply tothe caller’s UA (or to the requesting proxy server) with thecontact address of the user’s mobile phone, so that theincoming call can be redirected to the mobile phone.

� Proxy Server. A proxy server takes SIP requests,processes them, and passes them downstream whilesending responses upstream to other SIP servers ordevices. A proxy server may act as both a server and aclient, and may modify certain parts of a SIP requestbefore passing it along. A proxy is involved only in thesetup and teardown of a communication session. Afteruser agents establish a session, communications occurdirectly between the parties.

� Presence Server. Presence servers accept, store, anddistribute presence information that allows users to seethe availability of people they want to contact. The pres-ence server has two distinct sets of clients:

• Presentities (producers of information) providepresence information about themselves to theserver to be stored and distributed.

• Watchers (consumers of information) receive pres-ence information from the server. Watchers cansubscribe to certain users, much like instant mes-saging users choose which “buddies” to add totheir list.

Presence is a key feature in SIP-enabled communications net-works. Don’t worry if you don’t yet understand the concept:You can read more about it in Chapter 2.

Now, you may be saying to yourself, whew, that’s a lot ofservers! However, these functions can often be provided by asingle appliance, such as Avaya’s SIP Enablement Servicesplatform or the development environment provided by theAvaya SIP Application Server.

A Basic SIP Call ExampleThis section walks you through a basic SIP communicationsession — how it works, and how SIP supports it. Figure 1-2illustrates the session.


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In Figure 2-2, two people — [email protected] [email protected] — use SIP user agents (UAs) tomake a point-to-point call through a proxy server. Examples ofUAs could be an Avaya SIP Phone, a SIP softphone, or a PDAphone. The proxy server works to connect the two UAs. Thecommunication then follows these steps:

Figure 1-2: A typical SIP session’s ladder diagram.

1. [email protected] (the UAC) initiates a session by inviting [email protected] andsending this request to the proxy server at smallcompany.com.

Michelle’s UA generates an INVITE request, which issent to the proxy at smallcompany.com. The INVITEmessage contains Session Description Protocol (SDP)parameters that define the types of media she is capable of accepting and where she wants the mediato be sent.

2. The proxy at smallcompany.com performs a DNS SRVrecord lookup for SIP services at bigcompany.comsince bigcompany.com is a foreign domain. This

Michael’s softphone

Proxy server

John’s SIP phone

INVITE F1

100 Trying F3

200 OK F8

INVITE F2

100 Trying F4

180 Ringing F5

200 OK F7

ACK F9

180 Ringing F6

200 OK F11

BYE F10

Media Session

Dashboard

Profile:

Communications

Username:

Password:

Set Up:

Default

[email protected]

*****

Login

HistoryContacts


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record lookup returns proxy.bigcompany.com,which is then resolved to a physical IP address by DNS.Michelle’s INVITE request is then forwarded to theproxy server at bigcompany.com.

3. The bigcompany.com proxy server receives andprocesses the invitation, and looks up Tony’s contactin the location database of the Registrar (physical IPaddress of the UA).

4. The location database of the Registrar returns [email protected] where Tony is currently located.

5. The bigcompany.com proxy server forwards theINVITE request to Tony’s UA at [email protected].

6. The UAS at [email protected] asks Tony whetherhe wants to accept the call. Tony may hear a ring, seea text message, or see a blinking LED.

7. Tony’s acceptance is sent back through the bigcompany.com proxy, which forwards it to the smallcompany.com proxy, which forwards it to Michelle’sUA. The body of Tony’s acceptance includes SDPparameters defining the selected media chosen fromwhat Michelle had originally offered and where Tonywants the media to be sent.

8. Michelle’s UA responds to the acceptance with an ACK(acknowledgement) directly to Tony’s UA, which tellsTony’s UA that Michelle is ready to start the call.

9. At the end of the conversation, Tony hangs up hisphone. His UAC sends a BYE message directly toMichelle’s UA.

10. Michelle’s UAC responds with a 200-OK messagedirectly to Tony’s UA, which ends the session.

Though this call flow describes the initiation of a basic phonecall, that simple call flow would be the same for establishingvideo conferencing or other media sessions using SIP.


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Chapter 2

The Case for SIPIn This Chapter� Connecting people anywhere, anytime, on any device

� Introducing AORs — one convenient address for everything!

� Using voice, video, text, and more!

� Simplifying communications architectures for businesses large andsmall

� Preparing for a bold new future with SIP

What business initiatives are driving your organization’stechnology strategy? Perhaps it’s improving your cus-

tomers’ experience? Or, increasing the productivity of youremployees? Or, minimizing your operating costs? Gee, thoseall sound good! How about — all of the above!

SIP is one solution that can help your business achieve thesegoals. For example:

� Presence allows your employees and customers to com-municate more efficiently.

� User-centricity gives your users more flexibility andoptions while improving control of technology andgreatly simplifying device (and communications) management.

� Multi-modal capabilities provide a richer communicationsexperience and empower your business to better serveyour customers.

� Simplified architectures promote interoperability whilesimultaneously allowing your business to reduce costs,rapidly deploy new applications and solutions, and growwith your business.

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SIP Communications For Dummies, Avaya 2nd Custom Edition 16To illustrate the potential of SIP for your business or enter-prise, we examine some of these key features and advantagesand show you how SIP can help you address this myriad ofbusiness challenges!

The Presence Is Now!SIP supports a new model for communications through its useof the Extensible Messaging and Presence Protocol (XMPP, whichcan also be used for presence) and SIP for Instant Messagingand Presence Leveraging Extensions (or more simply, SIMPLE).Both are widely adopted open protocol standards defined bythe IETF.

In an intelligent communications network, people can specifytheir communications preferences and availability. This fea-ture is known as presence — an intelligent “network overlay”that makes it easier for a calling party to reach an availableand willing-to-be-called party. Presence enables people toinform others of their status, their availability, and how theycan be contacted before a communication session evenbegins, thereby increasing productivity by making it easier toreach people more efficiently. Many devices can provide pres-ence information, which is particularly powerful when inte-grated across all of a person’s communication devices, suchas IP phones, mobile phones, softphones, wireless devices,and PDAs.

Presence is not limited to a single person; it can also apply toa group of people (for example, “Finance”) or a device (forexample, Phone Status = “Off-hook” or “On-hook”).

Even more exciting, both people and applications can accesspresence information, providing the opportunity to createnext-generation converged communication applications. Forexample, your network can deliver new capabilities such aspolite calling (calls that are less disruptive for the party beingcalled) — based on information from her calendar applica-tion, calls to an executive can automatically be routed to anassistant if the executive is busy. This can eliminate the needfor the caller to leave a voice mail and allows the executive tostay focused on her current meeting.

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Making the World Revolvearound You with User-CentricCommunications

Over the last few years, business communications havebecome largely device-centric. The more devices you use, themore numbers and addresses others need to know in order toreach you. And without presence, as described in the previ-ous section, communication has become a guessing gamewhen trying to connect with people, wherever they may beand whatever they are doing.

Chapter 2: The Case for SIP 17

Is it a business card or a phone book?Like many busy people, you proba-bly have a number of ways forothers to get in touch with you andyou want a convenient way for themto know how to reach you withoutyour business card starting to lookmore like a phone directory! Forexample, you probably have somecombination of the following:

� At least four phone numbersincluding home, office (main anddirect), and mobile

� An SMS address for text mes-saging on your mobile phone

� Various instant messaging (IM)screen names or aliases

� A fax number

� Numerous corporate and per-sonal e-mail addresses andaliases (such as [email protected],[email protected], [email protected], [email protected])

Contacting you may have become aguessing game for your customers,clients, and partners. It shouldn’t bethis hard! The user now controlshow people communicate with you,and SIP can help by providing asingle address for all your communi-cation devices.

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With SIP, your business communication becomes user-centric,once again making it easier for you to reach your customersand for your customers to reach you. A SIP address of record(AOR) provides one unifying identifier that can be mappedacross multiple devices and media types. No more tracking ofmultiple phone numbers, e-mail addresses, and IM contactnames. You can think of an AOR as your “public address.”

One Protocol, Many Modes of Communication

New SIP-enabled converged communications solutions enableusers to interact with each other or with an application, in avariety of ways. Input can be via speech, keyboard, telephonekeypad, or mouse. Various modes of output may include syn-thesized speech, audio, plain text, motion video, and/or graph-ics. And best of all — you control how people reach you. Hereare some examples that SIP-enabled solutions can facilitate:

� Voice/IM/video: A common interface provides access toinstant messaging, voice, and video services, tiedtogether with presence. Initiating communications is thesame for all modalities, and users can switch from onecommunication method to another on the fly to bestmeet their needs.

� Inline translation services: A SIP request, originatingwith an English-speaking user, might contain a Web serv-ices request to translate a message into another languagefor a non-English-speaking recipient.

� Multimodal messaging: A SIP-enabled voice messagingsystem could provide features such as:

• Voice-mail headers to the end-user via text

• Display-enhanced voice-mail by delivering text orgraphics menus instead of voice-based menus

• Virtual business cards with every voice call so thatthe user can have the caller’s contact informationavailable

• Playback, skip, rewind, pause, slowdown, andspeedup buttons using a graphical user interface(GUI) in a screen phone


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� Speech-to-text translation: In situations where the calleronly has a phone and the called party only has a textdevice (PC, laptop, wireless device), a SIP-enabled trans-lation service could provide text-to-speech and speech-to-text translation.

� Web-based Interactive Voice Response (IVR): Usersmay surf the Web as opposed to working their waythrough IVRs. Such systems could be used from a hotelroom to order services, for example.

Because SIP uses the Session Description Protocol (SDP) todetermine what type of media stream the answering UA cansupport, SIP can make intelligent choices for modality.

SIP can also support multiple media types within a single com-munication session. This broad support creates a naturalsolution for providing communications that adapt to the userbased on the situation and the communication device beingused.

The term multimodality refers to the ability for a user (or deviceor application) to communicate through more than one mecha-nism. For example, a user may be able to input text via voice ortyping on a keyboard. An application such as the Avaya SIPsoftphone can deliver either a text or voice message.

Streamlining CommunicationsArchitecture

Communications networks today are complex and costly tooperate and maintain. By comparison, a SIP communicationsarchitecture consists primarily of SIP endpoints and SIPservers. This means that your business can simplify its commu-nications network and reduce associated costs. Endpoints arealso called user agents — the programs and devices that actu-ally perform the communications between end-users. In smallerbusinesses, the user agents can be smart enough to communi-cate with one another without servers. In larger enterprises, SIP servers such as proxies, registrars, and presence servers,facilitate user agent communications.

Chapter 2: The Case for SIP 19

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SIP scales well for even the smallest businesses, where SIP-enabled endpoints can be established in the absence of cen-tralized proxies and registrars. We discuss SIP for small officesin Chapter 3.

SIP offers a single unifying protocol for all real-time communi-cations. For example:

� With SIP being widely deployed in both service providerand enterprise networks, the need for gateways thattranslate one protocol to another (for example, IP toTDM, or Time Division Multiplexing) is minimized.

� Proprietary signaling protocols give way to a single stan-dard interface for all connectivity — whether for addingendpoints, deploying contact center adjunct services, oreven connecting to trunk services for external communi-cations.

� In addition to its forward-looking innovative uses, SIPsupports the legacy public switched telephone network(PSTN) and Private Branch Exchange (PBX) systems,which will be around for some time to come.

See Chapter 3 for more on SIP trunking.

An equally important foundation of SIP is the concept of dis-tributed intelligence. This concept, evident in peer-to-peer(P2P) architectures such as Avaya Quick Edition, creates anew paradigm in communications, requiring no PBX or com-munication server, only intelligent phones and other endpointdevices as the mechanism for establishing a working commu-nications system.

The Future Is Now!SIP, an extensible and versatile open protocol, has wide adop-tion throughout the industry. New solutions that will empoweryour business and employees to better serve your customersnow make intelligent communications routing and other deci-sions based upon interaction with users, such as a person'sknown physical location linked to presence.


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Chapter 3

How SIP TransformsCommunications

In This Chapter� Enhancing end-user communications with presence, preference,

user-centric communications, and mobile devices

� Understanding peer-to-peer SIP for small offices

� Taking a look at SIP trunking, federation, IMS, and SOA for the enterprise

SIP can revolutionize real-time IP communications in anyorganization, large or small. This chapter takes a look at

how SIP-enabled features like presence and addresses ofrecord can enhance the productivity and quality of communi-cations for end users. We also examine SIP for small andmedium businesses and discuss some of the unique challengesfor small and distributed business environments. Finally, wesee how SIP scales to even the largest enterprises and serviceprovider networks, providing the framework for new andevolving architectures such as IMS and SOA, and making SIP atruly universal solution for intelligent communications.

How SIP Transforms End-UserCommunications

Are you spending more time managing your communicationsdevices and looking up phone numbers or addresses thanactually communicating with others? If so, SIP is about to sim-plify your life and let you control your communicationsdevices, rather than having them control you.

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To Be or Not To Be . . . Available — with PresenceWhen a user activates a communications device (user agent,or UA), the device registers its presence on the network, indi-cating its ability to communicate. The concept of presence issomewhat analogous to the telephone network’s busy signal,signaling to a caller that you are unable to talk right nowbecause you’re already talking with someone else. But, SIPtakes presence a step further.

Presence distributes the following information:

� User status (that is, online or offline)

� User availability (such as Available, Away, In aMeeting, On the Phone, and Busy)

� User’s desired contact method (such as instant messag-ing, desk phone, mobile phone, pager, and so on)

SIP’s presence states also permit predictable rules-based rout-ing decisions to be made. These decisions are based on auser’s specific presence state, and on customizable prefer-ences that include any information the user wants to share.

Presence doesn’t just apply to people and need not only applyto a single entity; presence can also be associated with adevice or group. For example, a presence status might capturethe status of a device (Phone Status = Off-Hook) or thestatus of a user (User Status = Online). Presence forcomposite entities like contact center groups or shared docu-ments can be similarly represented.

Using presence to route communicationsSIP can make call-routing decisions based on presence infor-mation by enabling users to inform others of their status,availability, and how they can be contacted — before a com-munication session even begins. A user can communicatestatus and availability to others through multiple devices

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such as IP phones, mobile phones, softphones, instant mes-saging, pagers, video conferencing, e-mail, wireless devices,and even TDM phones connected to an intelligent IP PBX.

Presence can span a number of different communication chan-nels and provide an aggregate view of a user’s presence (thatis, availability across all of an individual’s SIP-enableddevices). Possibilities include:

� Setting the user’s status to Away when his phone andkeyboard are inactive for some time

� Making inferences about a user’s presence throughmobile device location information

� Checking a user’s calendar to see whether he is in ameeting or on vacation

� Checking a user’s e-mail to see whether he is reading orsending e-mail, or whether he has an Out of Officesetting

SIP uses presence to make routing decisions for a variety ofincoming communications including:

� Routing incoming calls from a desk phone to a mobilephone if the user has indicated that he is roaming andprefers calls routed as such

� Classifying non-urgent incoming communications aspolite calls that the user can choose to answer, forward,or ignore

� Routing urgent incoming calls and e-mail to others if theuser is on vacation or in an extended meeting

When a SIP proxy (a server that processes and forwards SIPrequests between calling and called parties) receives anINVITE (request to communicate), it uses the called party’spresence to make a routing decision, sometimes called forking. The forking decision may be to a specific party (an intelligent fork), or it may send several INVITEs to differ-ent addresses (parallel forking).

Forking is an old UNIX term where a process “clones” itselfinto two or more new processes. In the SIP context, forkingrefers to sending multiple simultaneous INVITEs to other par-ties to initiate a communication session.

Chapter 3: How SIP Transforms Communications 23

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AORs — 0ne address to rule them allAnother key feature of SIP is its ability to use an end-user’saddress of record (AOR) as a single unifying public address forall communications. With SIP-enhanced communications, auser’s AOR becomes her single address that links the user toall of the communication devices or services that she uses. Forexample, Eileen Dover’s AOR might be sip:[email protected]. Using this AOR, you can reach Eileen on any of her multiple communication devices (her UAs) withouthaving to know each of her unique device addresses or phonenumbers.


Presence means “being there” for your customers

Every successful company strives toprovide superior customer service,with call centers or contact centers(you can read more about contactcenters in Chapter 5), which are oftenthe first contact an upset customermay have with your company whendealing with a particular issue. Buthow can your customer serviceagents get to all the information theyneed to provide quick, accurateresponses for your customers?

A credit card company that providesongoing support for its customersthrough a contact center offers oneexample of how SIP presence canhelp you deliver superior customersupport. The names, places, andevents are fictitious, but the possibil-ities are real:

A customer planning an overseas tripcalls with a question about monetary

conversion rate policies. The cus-tomer service agent checks her“finance expert” presence tab andsees that an internal resident expertis off the phone and available for con-sultation. The agent clicks the IM taband is automatically routed to theavailable expert. The agent then gets,and quickly relays, the expert’sanswer to the customer. The cus-tomer then asks about a disputedtransaction with a merchant. Theagent brings up the merchant infor-mation, which displays the presenceand availability of the merchant’scustomer service agents for phonecalls or IM, and contacts an availableagent who can look up details of thetransaction and send it back via aWeb-page push. Complete customerservice with a smile (or maybe just asmiley face icon)!

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To complement AORs, SIP supports Uniform Resource Identifiers(URIs) that establish a common addressing scheme for all of anindividual’s user agents. A URI address follows the same basicformat as a Web or e-mail address: contact-address@domain. Using this format, SIP can map the unique addressesof a user’s multiple devices and services to a communicationdomain, and then link all the user agents to a user’s single AORfor that domain. Some examples of how a URI might be appliedinclude:

� A phone: sip:[email protected];user= phone

� A fax: sip: [email protected];user=fax

� An IM user: sip:[email protected]

A user typically has just one SIP AOR, such as sip:eileendover@domain. Each of the user’s devices then hasits own URI, such as sip:[email protected];user=fax.

Because a SIP URI supports both numeric (phone numbers)and alphanumeric (Internet-style addresses) formatted con-tact addressing, the public switched telephone network (PSTN)and the Internet can be seamlessly linked together. With SIP,users can potentially contact any user, whether they are onthe PSTN or the Internet.

As with e-mail addresses, users probably won’t memorizeother users’ SIP AORs. Instead, they’ll use address books andbuddy lists, just like they do on their e-mail systems, mobilephones, and IM clients today. A SIP AOR will be just anotherdata field associated with each person or group. When usedby a SIP device, the URI will be retrieved and used to commu-nicate with another party.

Better mobility with SIP and IMSBecause an AOR can be associated with any number ofdevices and/or applications, SIP can leverage all kinds ofmobile communications devices as part of a SIP-enabledenterprise. By applying intelligent forking , SIP can direct com-munications to any number of mobile UACs (user agent clientdevices) including mobile phones, wireless devices, and soft-phones or other applications installed on a laptop computer.


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Initial efforts to develop SIP-enabled mobility solutionsfocused on voice calls within wireless networks to lowerusage charges and require fewer phones. For example, Avayaand its partners pioneered the development of multimode SIPphones with both mobile and WiFi capability. These develop-ments served as an important step towards next-generationSIP-enabled communications applications.

Consider a business communications solution where SIP isthe common interface providing integration between enter-prise networks and service provider networks. While roamingin a service provider network, users can stay in touch withtheir virtual enterprise anywhere, anytime, any place — asthough they had never left the premises.

� Users can instantly receive enterprise voice messagenotifications while out of the office.

� Users working across multiple locations don’t have tocarry yet another phone, pager, or PDA.

� Services support improves because managers canquickly locate field technicians within a customer area toprovide better responsiveness.

� SIP-enabled user devices can respond to a phone call byresponding with a short text message that lets the callerknow the person’s availability.

SIP is well suited for mobile environments. SIP’s registrationfunction is similar to that in GSM and 3GPP networks. When auser turns on a SIP device, it registers the user and sends thedevice’s URI to the registrar server, which routes calls to andfrom the user. This system ties together multiple communica-tion silos (for example, e-mail, IM, desk phone, and mobilephone) using a single address that can reach the user regard-less of location.

What about customized options such as address lists, buddylists, and speed dials? SIP preference features can make thesecustomizations mobile. For example, Avaya’s Personal ProfileManager provides a centralized service that communicateswith SIP endpoints to receive, store, and distribute contactlists, access control lists for user presence, and device param-eters such as speed dials and feature button mappings — to


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the SIP endpoint currently in use. A Web-based interface, theSIP Personal Information Manager, allows users to securelymanage and view their profile and device information usingany standard Web browser. The user simply authenticatesthrough the endpoint and his stored data is securely down-loaded to create a customized user environment.

Native mobility is one of the reasons the Third-GenerationPartnership Project (3GPP) has adopted SIP as its primary sig-naling protocol for the IP Multimedia Subsystem (IMS). Otherreasons for using SIP as a core underlying technology for sup-porting IMS include simplicity, flexibility, extensibility, andfamiliarity — recall that SIP is a plain-text, open protocol stan-dard similar to HTTP that simply establishes, manages, andterminates real-time IP communications sessions over a widearray of mediums including voice, video, and text (refer toChapter 1).

IMS provides a framework for innovation within a serviceprovider network, enabling rapid development of new andinnovative multimedia applications and content over a mobilenetwork. SIP is the key to delivery of these innovations fromIMS to mobile networks and users.


Keeping up with mobile usersSIP enables seamless mobile com-munications — anytime, anywhere.For example, suppose a bank execu-tive adds a new contact to her per-sonal profile and assigns it a hotbutton or speed-dial. She initiates aSIP call through the internal networkusing her dual-mode mobile phone tocheck voice mail. While still listeningto messages, she walks out of theoffice to her car — and the callswitches on the fly to her mobileservice provider network. She thenarrives at the main office still on hermobile phone. The intelligent networkusing SIP detects her presence and

switches the call back to the com-pany’s wireless network automati-cally. The executive finds a mobileuser cubicle with a PC and softphoneapplication; upon authentication, herentire contact list and phone featuresare downloaded. She then checksher buddy list, sees via presence thather new contact is online and avail-able for a phone call, and she initi-ates a connection. Her contact is outin the operations center, so the net-work intelligently forks the connec-tion over to his PDA (which containsa SIP telephony client), and the callbegins.

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How SIP Transforms SmallOffice Communications

Small offices — including small or mid-sized businesses andsmall branches of large enterprises — are becoming moredynamic in form and function and are becoming increasinglydistributed. These work environments must address chal-lenges that although not unique, can be nonetheless dauntingfor small offices, including:

� Capital costs: As small offices seek to maintain a moredynamic form that focuses on the localized needs of theirmarkets, they often find themselves balancing the needfor adaptability with the upfront capital costs of commu-nications solutions.

� Operating and administrative costs: Communicationssolutions often require on-site technical installation andmaintenance services. Additional costs are incurredwhen local support is required to fix problems, addcapacity, or perform basic administrative tasks.

� Speed: For many small offices, competitive advantage isall about speed — time to deployment drives time tomarket. Developing new applications that integrate withcomplex communications architectures through openbut proprietary APIs (application programming interfaces)can be a time-consuming event requiring detailed plan-ning, staging, testing, and debugging.

� Business continuity: Small businesses are often moresensitive to disruptive events than larger businesses. Thesurvivability of a small business may be threatened byeven a relatively minor or short-term event lasting only afew days.

Peer-to-peer (P2P) SIP is one solution for small- and mid-sizedbusinesses. P2PSIP collapses some of the more complex serverfunctions into the phones (or other endpoints) themselves.P2PSIP relies on the core SIP philosophy that intelligence incommunications solutions should reside in the endpoint (referto Chapter 1 for more about the variety of available SIP end-points, or user agents). Contrast this approach with that ofold-fashioned analog telephones that do little more thanamplify voice signals and rely upon complex and fixed-costPBX switches to provide communications functionality.


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Peer-to-peer SIP communicationsoverviewIn large enterprises, SIP is most often implemented using cen-tralized services such as proxy servers, presence servers, gate-ways, and location servers yet with redundant edge devicesthat understand multiple home-proxies. But, SIP endpoints canalso function without all of these central services in small-officesettings bringing the advantages of SIP to small and mediumbusinesses, such as cost reduction, converged voice/video/data over SIP trunking, presence, and UC applications.

Avaya is an active member of the IETF P2PSIP working groupthat is working to define a P2PSIP protocol standard and toaddress issues such as security and privacy in a peer- to-peercommunications network.

P2PSIP effectively replaces the registration, location, andlookup steps of SIP. It handles three functions:

� Registering a phone or a user with the peer-to-peer over-lay network (when the phone or user joins the network)

� Looking up a phone or a user in the peer-to-peer overlaynetwork (when a call to the phone or user is made)

� Dynamically sharing information when peers join andleave, so that the load is balanced across peers, and sothat the sudden loss of one or more peers doesn’t causethe peer-to-peer network to lose track of its current registrants


Avaya IP OfficeIP Office is a highly modular IP tele-phone system designed to meet theneeds of home offices, standalonebusinesses, and networked branchand head offices for small and mid-size businesses. The award-winningIP Office gives growing companies a

complete solution for telephony, mes-saging, networking, conferencing,customer management, and unifiedcommunications, thereby helpingbusinesses reduce costs, increaseproductivity, and improve customerservice.

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With P2PSIP technology, you can drastically simplify tele-phone system setup and installation. Plug an IP telephone intoyour local area network, and it configures itself. In minutes, allusers have access to the most commonly used features,including voice mail, conferencing, and auto-attendant. Asimple PSTN gateway also acts as a peer to the phones andcan provide access to the PSTN. And a peer-to-peer solutioneasily grows with your business. As you add employees,simply add telephones.

How SIP Transforms EnterpriseCommunications

SIP fundamentally improves the efficiency of communicationsbetween enterprises and their partners, suppliers, and cus-tomers. The initial benefit of IP communications has been primarily limited to intra-enterprise communications.Communications between enterprises, even those that areVoIP-enabled, still largely require a circuit-switched handoffthat impacts voice quality, adds complexity, and introducesadditional expense through intermediate carriers. SIP changesall of that by interconnecting SIP communications architec-tures and the PSTN, and with SIP trunking and federation services.

Enterprises can benefit from the simplification of enterprisenetworks through SIP standardization for both internal andexternal communications. As SIP becomes ubiquitous in bothservice provider and enterprise networks, a single standardinterface for all connectivity is available for adding endpoints,deploying contact center adjunct services, or even connectingtrunk services for external communications. Proprietary sig-naling protocols, including variants of voice-centric T1 and E1standards, and hardware-intensive digital/analog interfacesgive way to a simple, logical SIP interface that connects appli-cation servers residing on industry-standard platforms. WithSIP as a unifying protocol, you can dramatically reduce theneed for dedicated hardware gateways and devices.


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Working together: SIP and the PSTNClearly, the telecommunications industry’s system of countrycodes, area codes, city codes, and telephone numbers willcontinue to serve many people around the world for sometime to come. So, how do you call SIP users with URIs from aplain old telephone system (POTS) using a dial-up telephone,and vice versa?

Fortunately, the mapping between SIP and telephony proto-cols has already been defined. Gateways that link the Internetwith the PSTN are widely deployed and used by VoIP usersevery day. SIP URIs can also be used to carry telephone num-bers. For example, sip:[email protected];user=phone contains the phone number for directory assis-tance in New York, New York.

By porting a PSTN telephone number to a SIP/PSTN gateway,incoming telephone calls can be routed to SIP phones, callmanagers, and PBXs.

Many service providers have already adopted SIP for theirinternal PSTN telephone call routing. With SIP-to-PSTN inter-working (providing connectivity between these two systemsthrough a defined interface standard) in place, carriersthroughout the world are working with SIP vendors like Avayato offer exciting new SIP trunk services to the enterprisemarket.

Trunking with SIPTrunking refers to the means used to transport inbound andoutbound calls between the enterprise and external entities(including branch offices and other remotely located partiessuch as business partners, customers, and suppliers). In thissection, we describe the differences between traditionaltrunks and SIP trunks, as well as some of the characteristics ofSIP trunks that are attractive to businesses.


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Before SIP and VoIP, enterprises connected their internal PBX-based telephone systems to carriers via dedicated TDM(Time Division Multiplexing) trunks. Companies paid for themwhether they were idle or busy, and incurred toll and tariffcharges, particularly expensive for long-distance calls.

Today, many companies integrate voice and data over IP net-works and link their sites using wide area networks to reducecommunications costs within the enterprise. However, tradi-tional PSTN circuits are still used to communicate with theircustomers and suppliers, partners, and the outside world.

SIP trunks enable enterprises to carry their voice data over apure IP connection to carrier clouds, rather than through sep-arate “voice-only” circuits. An enterprise SIP proxy peers witha carrier SIP proxy, with the appropriate federations and secu-rity protections established between them. The IP circuit con-tinues to carry e-mail, Web, data, and other corporate trafficas it does today, and voice is simply added to the mix asanother IP application. SIP sets up and tears down voice callsto and from the enterprise over this IP circuit.


How SIP trunking can help you improve customer service

SIP can improve the way a retail busi-ness services its customers. Supposea retailer with several store locationswants to offload the task of handlingphone calls from its store employeesso they can focus on in-store cus-tomers, but the retailer has no directconnectivity between its customerservice center and each store.

SIP-based trunking enables a recon-figuration of communications toaddress the problem. Through SIP-based DID (Direct Inward Dialing)mobility inbound service, the serviceprovider transports local calls to each

store over the SIP network directly tothe customer service center.

Without making any changes to thelocal stores, the retailer is now ableto free up store employees to servein-store customers, improve cus-tomer service over the phone byreducing hold times and busy signals,and still retain a local presence to itscustomers through a local accessnumber. And with SIP trunking, thecustomer service center can replacedozens of traditional TDM (Time-Division Multiplexing) trunk lines witha single SIP link!

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On-net calls traverse the carrier’s VoIP backbone (which istypically dedicated to voice so that voice quality can be guar-anteed). Off-net calls ride the carrier IP network until the “lastmile” where a gateway converts VoIP to TDM for calls to PSTNparties (see Figure 3-1).

Figure 3-1: SIP trunks change how you make connections to carriers.

SIP trunks offer a number of advantages, including:

� PSTN origination/termination and cost savings: ManySIP service providers support origination/terminationservices directly to the PSTN from their SIP networks.This allows the enterprise to reduce monthly recurringcosts associated with multiple TDM circuits by deployinga single IP pipe to the provider network.

� DID and Toll-free Number Mobility: These features takeadvantage of the fact that SIP is geographically agnostic.Calls destined to local or toll-free numbers can be auto-matically rerouted over the service provider SIP networkto another enterprise location. For enterprises, thissystem offers great flexibility in providing a local pres-ence in all their markets while routing calls to a central-ized call center for more efficient service.

Session Border Controllers (SBCs for short) are edge securitydevices that sit at the edge of a SIP enterprise network and acarrier or ISP network cloud. Among the multiple functions

Phones

SIP Proxy

Router

IP Data/Telephony

All Communications

ServiceProvider

SIP Network

PSTN LongDistance

PSTN LocalAccess

LAN


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these devices can provide, some SBCs have been designed tosupport both inward and outward translation of URIs to E.164(phone number addressing).

In a converged network, voice becomes an IP application,sharing the common network infrastructure and services.

Where no one has gone before —connecting enterprises to federated servicesA common concern for companies contemplating the switchto SIP is how quickly all these nifty advances are going tocome together in a truly comprehensive way. In particular,how can isolated enterprises exchange directory information?Sure, each step toward SIP is a step in the right direction, buthow do you get everyone marching in step? The answer: federation.

In recent years, businesses have enthusiastically adopted IPfor their internal communications. For example, today farmore IP PBXs are sold than TDM PBXs. However, most ofthese IP communication infrastructures stop at the enterpriseboundary. IP PBXs “fall back” to TDM and revert to phonecalls for communication outside of the enterprise. As a result,IP communications “islands” are growing, but they are notinterconnected. With SIP, interconnection of these islandsover the Internet is accomplished. The benefits of intercon-nection are enormous. For example, you can

� Extend SIP-enhanced services beyond the enterpriseboundary

� Make additional modes of communication available,including multimedia and instant messaging

� Establish higher-quality connections

� Reduce costs by bypassing TDM network interconnections

If two enterprises both use SIP, they can interconnect andenable SIP-to-SIP calling, interact via multimedia sessions andinstant messaging, and exchange presence information.


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What are the obstacles to interconnection? To enjoy the fullbenefits of SIP, you need to overcome three main barriers:

� Enabling SIP islands to discover the existence of oneanother

� Ensuring that the two islands interoperate

� Managing and controlling interconnections so that spamand abuse do not become rampant

One solution to these issues is federation. Federation builds anetwork of open communications within the ecosystem of SIPcommunications. Accomplishing this interconnectivity mayrequire one or more of the following:

� A federation service that provides discovery servicesenabling other SIP islands to be discovered from just atelephone number or address. A number of databasesand directories are available. One such database isENUM, described in the next section.

� A federation service built on top of SIP that providesinteroperability over a wide range of services and fea-tures such as voice, video, presence, and IM. A federationservice may also provide gateways for interoperabilitywith non-SIP devices.

� A federation service that authenticates users and setspolicies for acceptable use. A SIP equivalent of caller ID ispossible in this model, enabling users to trust a callingparty. This helps avoid the anarchy of e-mail in whichanyone can claim to be anyone else (spoofing).

An alternative to federation is direct peering. In this mode, twoenterprises get together, exchange directory and routing infor-mation between them, and set up policies and procedures forcommunication. Although this system may work among ahandful of enterprises, direct peering is cumbersome whenconnecting multiple enterprises and obviously does not scalelike a federation.

Mapping phone numbers to URIsTo interconnect SIP islands, your network needs a method ofdiscovering a SIP URI from a telephone number. The ENUMprotocol has been developed by the IETF Telephone Number


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Mapping working group for this purpose. ENUM has a DNS-based architecture and protocol by which standard telephonenumbers can be expressed as a Fully Qualified Domain Name(FQDN) in a specific Internet domain (e164.arpa). The resultof the ENUM query is a series of records (defined in RFC 3402)that gateways, proxy servers, and even SIP endpoints can useto contact one or more resources associated with that number.

As SIP continues to be adopted by service providers, ENUMwill become part of the suite of services that a serviceprovider connecting to a SIP enterprise network can deliverthrough the PSTN. On your SIP phone, you’ll be able to punchin a URI for your friend’s TDM landline or mobile phone, andthe carrier’s ENUM server will seamlessly connect you.

An alternative to ENUM is LDAP (Lightweight Directory AccessProtocol), which can store both a user’s URI and all associatedphone numbers (E.164 addresses). SIP applications can thenreference entries stored in LDAP to resolve and translatephone numbers to URIs. Many applications already supportLDAP interconnectivity. For example, Avaya CommunicationManager with either Avaya SIP Enablement Services or AvayaSIP Application Server development environment can inter-face with LDAP to send calls bound for SIP URIs to standardtelephones on the enterprise’s IP PBX.

Enterprise SOA and intelligentcommunications Service Oriented Architecture (SOA) is a methodology thatfocuses on three major objectives:

� Designing IT infrastructures that allow different applica-tions to interoperate and exchange data via a commoncommunications protocol

� Leveraging existing applications by exposing their capa-bilities as services that can be easily used by other applications

� Using these services to automate business operations


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SOA is possible in an advanced, intelligent communicationsinfrastructure based on a value proposition of strategic valueversus economic efficiency. At the heart of the strategic valueproposition is the promise that communications capabilities,when closely integrated with business processes and applica-tions, can greatly enhance the speed and ability of enterprisesto respond to changes in customer and market demands.

SIP-enabled communication services extend and simplify com-munications within enterprise processes with a portfolio oftelephony, messaging, speech, and contact center solutions.

SIP integrates easily with the Web service environments being developed for many business critical applications. Forenterprises, this means the introduction of powerful multi-modal communications, embedded as a service within theirbusiness applications. It also means that information on userpresence can be incorporated into application business logic.Communication becomes a tool not just for users, but also forthe enterprise’s critical business applications.


Avaya Unified CommunicationsAvaya Unified Communications com-bines SOA and SIP, along with busi-ness-intelligent technologies thatintegrate business-context knowl-edge and user communication con-text knowledge. The end vision is acomprehensive, multi-channel com-munication access architecture thathelps increase business agilitythrough rapid, intelligent responses to

business events that can find andconnect the right people, at the righttime, with the right devices. UnifiedCommunications has intelligent inte-gration that enables businesses tokeep their decision-making processesmoving towards resolution, whetherfor application-to-application, human-to-application, or application-to-human communications related tasks.

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Chapter 4

SIP InteroperabilityIn This Chapter� Getting acquainted with industry and vendor interoperability

initiatives

� Examining interoperability within the enterprise

� Looking at interoperability beyond the enterprise

� Appreciating SIP security and survivability

As previously discussed, SIP is an open and extensibleIETF protocol standard that has gained widespread

support and acceptance among a growing community of hardware and software vendors. In this chapter, we discussinteroperability within enterprises and among enterprises,including topics such as hybrid infrastructures, the communi-cations “ecosystem,” survivability, federated presence andsecurity.

Proving That We Can “All Just Get Along!”

SIP is an open protocol standard developed to help facilitatereal-time IP communications and other forms of peer-to-peerand group communications. Communications hardware andsoftware vendors have recognized the universal appeal of theSIP protocol and are adding SIP capabilities to a rapidly grow-ing number of products. Various interoperability initiativescurrently under way include:

� Development of a reference architecture of commonnetwork elements

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SIP Communications For Dummies, Avaya 2nd Custom Edition 40� Specification of the basic protocols (and protocol exten-

sions) that must be supported by each element of the reference architecture

� Specification of the exact standards associated withthese protocols

� Specification of standard methods for negotiating proto-cols, protocol extensions, and exchanging capabilityinformation between endpoints

� Definition of authentication methods to ensure usersecurity and accurate billing

Several organized groups and communities are actively work-ing to promote SIP interoperability, including:

� Developer Connection is Avaya’s program to promoteinteroperability between Avaya products and others inthe market. Go to http://devconnectprogram.com.

� SipCenter promotes the development of SIP-based products and interoperability. Go to http://www.sipcenter.com.

� SIP Forum promotes industry interoperability by hostinglive testing events, defining and creating compliancetests, and developing industry-wide technical recommen-dations. More information is available at http://www.sipforum.com.

� SIPconnect is a standards-based initiative of the SIPForum to promote direct peering between SIP-enabled IPPBX systems and VoIP service provider networks byensuring interoperability between SIP trunks and legacyTDM environments. Go to http://www.sipforum.com/sipconnect.

� SIPit (SIP Interoperability Tests) is a week-long semi-annual test event held at locations around the world forthe purpose of promoting global SIP interoperability. Moreinformation is available at http://www.sipit.net.

� SPEERMINT is an IETF working group established toaddress peering and operational issues in real-time IPcommunications sessions. Learn more at http://www.ietf.org/html.charters/speermint-charter.html.

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These are just a few examples of the interoperability initia-tives that are accelerating the already rapidly growing adop-tion and reliability of multi-vendor SIP environments.

Multi-Vendor IntegrationOne challenge many enterprises face is multi-vendor PBX net-working. Traditionally, interconnection has required the useof Q-interface Signaling protocol (QSIG) to enable support ofsupplementary services between systems. This does providelimited interoperability between systems, but it doesn’taddress the management issues caused by the duplication offeatures and systems, or the training complexity arising fromdifferent user experiences with each system.

Although SIP isn’t a silver bullet, it does provide enterpriseswith more options for multi-vendor integration within an IPtelephony environment based on open standards. For exam-ple, a variety of user agents (such as a softphone) can be con-nected to the PBX using SIP. And, with federated services(refer to Chapter 3), you can support basic connectivitybetween different vendors’ systems, devices, and applicationsusing SIP. Soon, SIP will enable enterprises to combine multi-ple PBXs into a single system, which reduces complexity forboth users and administrators. Interoperability within the SIPecosystem, which spans a wide range of telecommunicationsand networking technologies and services, is key to SIP’swidespread adoption and rapid growth.

Avaya is committed to fostering SIP interoperability, reflectedboth in its extensive portfolio of SIP products and applica-tions and its interoperability testing and certification pro-grams such as DevConnect, the SIP Ecosystem Partnerprogram, and the BusinessPartners program.

Avaya is clearly committed to SIP interoperability among vari-ous vendor products. At a recent industry interoperabilityevent (Interop 2007), Avaya was the only major telecommuni-cations vendor to successfully demonstrate basic SRTP inter-operability for both PBX’s and phones. We discuss SRTP inmore detail later in this chapter.

Chapter 4: SIP Interoperability 41

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SIP is designed to simply set up, manage, and tear down callsand sessions. Although the SIP protocol is expanding, otherprotocols are still necessary to address interoperability withsystems and applications such as:

� Interactive Voice Response (IVR) systems

� Firewalls

� Conferencing bridges

� Instant messaging platforms

In essence, these systems must rely on much more than SIP towork together today.

Internal to the EnterpriseEnterprise telecommunications infrastructures can often beclassified in one of three distinct phases in their evolution.

In the first, or traditional phase, enterprises have separateinfrastructures for voice and data networks. Time divisionmultiplexing (TDM) is used for voice, and Internet protocol (IP)is used for data.

This paradigm is sooo twentieth century (literally)! Prior to2000, ISDN and TDM voice networks used the Signaling System#7 (SS7) set of protocols to set up and tear down telephonecalls on the PSTN. Applications were developed to interfacedirectly with connection-management protocols, which inter-faced directly with ISDN- and TDM-based access protocols.


Avaya Intelligent Presence ServerWith the introduction of AvayaIntelligent Presence Server in early2008, Avaya became one of the firstSIP vendors to “crack the code” onfederated presence, providing a scal-able, high performance presenceaggregation service that collects anddisseminates rich presence from

Avaya and other third-party sources.Using rich presence, users gain theability to more effectively reach thepeople they need, leveraging the mul-tiple channels of communicationsavailable to them, no matter whatvendor applications, platforms, orend-devices they are using.

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In this phase, interoperability between voice and data sys-tems is largely non-existent. Your telecommunications circuitsand data circuits are separate and unable to share excesscapacity or offload excess traffic. Thus, your network may becrawling while your phones sit idle, or your Internet connec-tion may be blazing fast but your increasingly frustrated cus-tomers get continuous busy signals when trying to call you.And, you get to pay the same circuit rates whether they arebusy or idle!

This also means that your various devices and applicationsdon’t interoperate. Your office phone is just your office phoneand your mobile phone is just your mobile phone — two sepa-rate phone numbers to reach one person, and two separatevoicemail systems. And e-mail, instant messaging, video con-ferencing, and on and on!

In the second, or converged networks phase, enterprisesbuild out their IP networks to leverage a common infrastruc-ture that flattens, consolidates, and extends their voice and data networks. This enhances the IP network to meetenterprise-class criteria: improving quality of service (QoS)and increasing the reliability of real-time, mission-critical business and communication applications. Applications, builton the Computer Telephony Integration (CTI) overlay, interfacedirectly with connection management protocols, which inter-face with H.323 and IP-based access protocols.

“Ripping and replacing” everything in one step is often tooexpensive for organizations, particularly given their large cap-ital investments in legacy PBX equipment. Still, organizationscan attain significant cost savings now by implementing coreSIP routing (using a gateway if needed) and trunking, bydeploying selected SIP applications such as conferencing,mobility, and Unified Communications, and by taking advan-tage of SIP features such as centralized management of dial-plans and on-net calling.

Finally, in the third phase, enterprise communications capabil-ities are closely linked to business processes and applicationsto deliver real business advantage, allowing an organization to quickly adapt to changing customer needs and market situations.


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In this phase, interoperability of systems and applications isthe key to success. Peering and loose coupling promotesrapid development and deployment of applications with SIPas the unifying protocol between applications, connectionmanagement, and access-layer protocols. In this model, inno-vative uses of SIP include intelligent customer routing in contact centers (discussed in Chapter 5) and voice portals “at the edge” providing customers with self-service options.

External from the EnterpriseInteroperability with the PSTN is achieved through gateways,SIP trunking (explained in Chapter 3), and through SIP-T, aprotocol used mostly by service providers to carry ISDN sig-naling within SIP messages.

Many enterprise communications vendors, including Avaya,actively promote interoperability programs with carrier net-works. Avaya co-founded SIPconnect (now part of SIP Forum)to define interoperability specifications for the carrier-to-enterprise interface. Through its SIP certification program forservice providers, Avaya has tested and certified interoper-ability with a number of service providers.

SIP Security and SurvivabilityBecause SIP relies heavily on an IP-based network and utilizesa plain-text language similar to HTTP, SIP-enabled applicationsare potentially vulnerable to many of the same security threatsthat plague corporate networks and the Internet today. Theseinclude authentication, authorization, and privacy issues,denial of service and buffer overflow attacks, and SPIT (SPAMover Internet Telephony).

Fortunately, many of the same solutions to these problems areeffective for securing SIP implementations as well. These mayinclude:

� HTTP Digest Authentication using MD5 for challenge/response user authentication

� Signaling channel encryption using Transport LayerSecurity (TLS) for end-to-end session security


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� Certificate Authorities (CA) for authentication in networksusing SRTP and TLS

� Secure Real-Time Transport Protocol (SRTP) or IP Security(IPSEC) using Advanced Encryption Standard (AES)encryption to provide authentication, confidentiality, andintegrity for protection of the media (to prevent eaves-dropping, for example)

Other security concerns are not necessarily unique to SIP, butare nonetheless threats that must be addressed with innova-tive solutions. For example, spam has become an unfortunatepart of our modern e-mail lexicon, and SPIT may be an equallyvexing problem, if not even more ubiquitous than spam.

Another major concern for enterprises is survivability of theirtelecommunications and network systems. Traditional TDMtelephone equipment and the PSTN are commonly perceivedas highly reliable, dedicated networks and systems comparedto distributed, “best effort” networks such as the Internet.

Although a high degree of redundancy is built into the individ-ual components of expensive TDM PBX systems, havingredundant PBX systems in remote locations capable of provid-ing seamless failover during a major systems malfunction orfailure, or a catastrophic event is rather uncommon.

By comparison, IP-based communications systems and net-works, in addition to having built-in redundant components,are commonly deployed as duplexed systems or server farmsin multiple locations. SIP survivability and redundancyincludes benefits like re-routing DID’s and quickly redirectingcalls to alternate data centers (or having the Service Providerdo so after a specified timeout) — something traditional PSTNcircuits don’t provide. Even SIP endpoints can failover to thirdparty SIP gateways as part of the “survivable intelligent edge.”

Avaya is #1 in the industry for survivability and redundancyand is firmly committed to promoting interoperability amongall SIP-enabled vendor systems.


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Chapter 5

SIP in the Contact CenterIn This Chapter� Defining a contact center

� Using inbound, outbound, self-service, and blended centers

� Transforming the contact center with SIP

No company operates in a vacuum, devoid of contactwith customers or the general public. If you have the

need to communicate with others outside of your company(who doesn’t?), then you are a prime candidate for developingor using a contact center.

This chapter introduces contact centers — what they are andhow they benefit customers and companies, and how SIP cantruly transform your contact center into a world-class serviceorganization.

Call Center Versus Contact Center

You may be asking yourself “What’s the difference between acall center and a contact center?” You may think of a callcenter as a group of people sitting in neat rows beside theirphones, answering customer calls. But contact centers aremuch more than large rooms filled with headset-wearingswitchboard operators. The modern contact center handlesphone calls, e-mail, and online communication — includinginstant messaging.

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SIP Communications For Dummies, Avaya 2nd Custom Edition 48Traditionally, contact centers have been known as call cen-ters. The newer name — contact center, and even customerservice center — reflects the fact that more than just phonecalls are being handled, including e-mails, IM/chat, Web,video, and video kiosks.

Some companies choose to separate the handling of customercontacts by communication medium. For example, a companymay establish a department for inbound calls, one for out-bound calls, and another for e-mail. Some companies opt tocreate “universal” or “blended” agents who handle all contacttypes. Companies create universal contact agents for effi-ciency and service. Training agents to use multiple communi-cation methods to provide product or service information isoften more effective than training multiple agents to use asingle communication method to provide the same product orservice information.

Contact centers deal with almost any type of contact for acompany including phone calls, e-mails, online communica-tions (such as instant messaging or chat windows), Web, oneway and two-way video, and video kiosks.

Inbound and Outbound Contact Centers

Contact centers communicate with customers in a number ofways, but who initiates the contact defines the type of contactcenter. If the outside world initiates contact, then the contactcenter is said to be an inbound contact center. Conversely, ifthe contact center itself is responsible for initiating contact,then the contact center is said to be an outbound contactcenter.

Customers contact inbound centers to buy things, such as air-line tickets; to get technical assistance with their personalcomputer; to get answers to questions about their utility bill;to get emergency assistance when their car won’t start; or forany number of other reasons for which they might need totalk to a company representative.

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Increasingly, companies are looking to inbound call centersfor proactive customer service that could be used for cross-selling and up-selling opportunities.

In outbound centers, representatives from the company initi-ate the call to customers. Companies might call to notify acustomer that a product ordered has arrived, to collect anunpaid invoice, to follow up on a problem the customerreported, or to survey customer satisfaction or solicit ideasfor product or service enhancements.

Outbound contact centers are, most often, very telephone-centric because of tradition and perception. It is not unusualfor a company representative to call a customer on the phone;by contrast, simply sending the customer an e-mail may seemtoo impersonal and ineffective.

Self-Service Contact CentersA new breed of inbound contact center is starting to emerge —the self-service center. In traditional contact centers, all interac-tion between the customer and the center is done with humanagents. However, in self-service centers a good portion of theload is being shifted toward non-human automated responseor speech-enabled systems.

Automated response systems prompt customers to use theirphone keypads or voices to answer questions that help toroute their calls appropriately. Each button push or responsebrings the caller closer to the desired information. Automatedresponse systems have been around for years, giving the cus-tomer access to simple (and common) information, such asmailing addresses, driving directions, account balances, andprocedural instructions. These systems can also be used toroute calls to the most appropriate human agent able toanswer the call.

Transforming the Call CenterThere are many ways to transform your call center into aworld-class contact center and thereby gain efficiencies andgreatly improve your customer service capabilities.

Chapter 5: SIP in the Contact Center 49

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Many companies are adding more channels of contact tocreate an enhanced experience resulting in higher customersatisfaction. Market research indicates that the new standardfor contact centers includes a combination of phone, e-mail,self-service, and Web communications capabilities.

If your contact center is running separate call-handling groups(customer service and collections, for example), then by merg-ing these groups you can take advantage of the economies offull-service contact centers. You can continue to have call-handling groups logically separated, but with the ability foravailable agents in one area to handle overflow in anotherarea.

Implementing an IP contact center can help make your opera-tion more scalable, which means your company can grow with-out costly build-outs or investments. Instead, you can utilizeand manage remote agents — through your IP infrastructure —as if they were physically located in your office.

You can also benefit from improved agent occupancy byblending work into your contact-handling queue. A classicexample of blending is mixing outbound telemarketing into aninbound sales or service queue. In this case, you make use ofagent idle time — time agents spend waiting for incomingcalls — to do your outbound work. As a result, your agentsare busier (more occupied) overall. Should inbound volumesincrease or spike, your agents can stop making outbound callswhile they handle inbound calls. Other work such as e-mailand chat can also be blended.

SIP in the Contact CenterThe transformation from call centers to IP-based contact cen-ters has moved beyond the early adoption stage to the main-stream as IP communications matures and its benefits arerecognized.

Businesses are leveraging the power of open IP standards tosimplify application logic and to eliminate needless redun-dancy in the infrastructure and operations of their contactcenter. The result is that every agent and expert has full


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access to the required features, functionality, and informationneeded to serve customers better on each call or contact.

IP-based contact centers are simultaneously lowering net-working costs, distributing the agent workforce, and enhanc-ing agent productivity through multi-modal communications.Customers can reach agents by whatever means they choose(e-mail, instant messaging, Web chat, video, or phone call)and the agent can then route the request as appropriate.

SIP further extends these advantages by facilitating a moreefficient and collaborative communication model between theenterprise and its communications ecosystem.

For example, SIP allows agents to take advantage of presenceinformation to determine the status of enterprise subject-matter experts and then to easily connect with them. Withintegrated instant messaging, agents can communicate withsupervisors, peers, and experts while remaining on the callwith the customer. Bottom line: Customers make one phonecall and they’re done! No need for frustrating follow-up callsto get through to the right person.

The productivity gains can be immediate. When answers areneeded, an agent can contact an expert either within or out-side of the contact center via a choice of communicationoptions. The agent simply checks the availability of expertsfor phone consultation or instant messaging and contacts theexpert using either method. This capability allows enterpriseknowledge workers to become on-demand experts whoseavailability can be determined in real time and then easilylocated and contacted.

A common metric for assessing contact center efficiency andcustomer satisfaction is the number of first-call resolutions.Integrated SIP and presence helps raise this resolution ratebecause experts are now just a mouse click away. Agentsdon’t have to transfer customers to other agents, forcingcallers to repeat their questions or issues. Talk times are oftenreduced since the agent doesn’t have to hunt for experts.Overall call volumes can be lowered when customers get theiranswer on the first try and don’t have to call back. The con-tact center is more efficient, and customers are happier.


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Extending Customer ServiceBeyond the Contact Center

Many contact centers tend to operate as standalone opera-tions, separate from the rest of the enterprise. Expertisewithin the enterprise, and among its suppliers and partners,typically is not available as a resource to assist with customerinteractions.

The costs for contact centers to replicate knowledge, alreadypresent in the enterprise and its ecosystem, too often strainalready limited resources. The skills-based routing paradigmof transferring calls in search of expertise can result in longwaits, dropped connections, and customer frustration.

SIP presence facilitates a more efficient and collaborativecommunication model that will help merge not only enter-prise communications with contact center processes, but willalso integrate the enterprise ecosystem. Through a standardmechanism for communicating presence, contact centerresources across enterprises can also be linked.

SIP fundamentally changes the reach of the contact centercall-routing decision. In effect, everyone within the enterpriseand its ecosystem of partners and suppliers can become acontact center resource. The contact center no longer has torely solely on dedicated agents. No longer is the contactcenter an isolated business function, but an essential part of abusiness process that involves and leverages all resources toimprove the customer experience.

Building an Open, Modular, and Simplified Contact CenterArchitecture

Today, contact center and call center architectures reflect astrong hardware-centric model based on a PBX and ACD(Automatic Call Distributor) heritage. The current state-of-the-artcontact center includes a variety of applications such as skills-based routing, screen pops with CRM (Customer Relationship


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Management) applications, multimedia customer input chan-nels, and ICR (Intelligent Customer Routing).

Many companies have multiple contact centers located acrossthe country or around the world. While this approach providesa local presence for the business, it creates additional costsand introduces operational inefficiencies. Each locationrequires servers and applications: the switch, the contactcenter software, reporting, workforce management, and soon. When these components are replicated for each contactcenter site, the cost and complexity can be significant. Add therequirements for communications, call transfers and call cover-age between sites, and the cost and complexity rise even more.

Contact center solutions based on IP have been addressingthese issues by introducing a “flatten, consolidate, and extend”approach to consolidating multiple contact centers over an IPnetwork. A single central location (and perhaps a second forsurvivability) serves as the heart of the operation, providingthe intelligence and the contact center applications. Othersites serve as a gateway off of the centralized hub. Cost-effective communications between the central site and satel-lite locations is achieved by using IP for the communicationpath. With centralization, the network is flattened and costsassociated with multiple instances of each application aredrastically reduced. One consolidated contact center nowserves the business — eliminating the need for network pre-route solutions and their associated costs and complexities.

With Intelligent Customer Routing (ICR), the consolidated IPcontact center also provides a new paradigm for customerservice. ICR is a tool that provides businesses a new way totreat customers and respond to their specific, individual needsby leveraging customer data to route every customer interac-tion in the most efficient and cost-effective manner to providethe highest-touch, highest-value customer experience.

In addition, this approach becomes cost effective for extend-ing the contact center to areas of the business that previouslydid not have coverage. Companies gain a larger agent pool byeliminating the geographical constraints they’ve previouslyhad to consider. Providing consistent customer support and aconsistent brand image becomes easier. IP becomes anenabler of business transformation and saves real dollars.


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SIP can take this a step further by introducing a single standardinterface for all connectivity, including adding endpoints,deploying contact center adjunct services, or even connectingtrunk services for external communications. Proprietary signal-ing protocols and hardware-intensive digital/analog interfacesgive way to a simple, logical SIP interface that connects applica-tion servers residing on industry standard platforms. This newmodular server architecture can be software-centric, which willsimplify upgrades and promote greater flexibility by enablingthe rapid deployment of new services.


Session management with AvayaCommunication Manager and SIP

Enablement ServicesAvaya Communication Manager andSIP Enablement Services continuesto evolve as an open, highly reliable,and extensible real-time communi-cations platform that enables UnifiedCommunications and Contact Centerapplications. Reduced TCO, in theshort term, and increased ROI on the entire SIP investment, in the mid- and longer term, is achievedthrough expanded functionality,which includes

� Routing SIP sessions across thenetwork

� Centralizing SIP registration andlocation services

� Extending geographic redun-dancy with a distributed, highlyreliable, presence-enabled SIP

and SOA architecture thatenables massive scalability fromthe smallest deployments to morethan 250,000 users per system

� SIP trunk termination at theaccess point controlled by ses-sion management and redirectedto any application

� Adding session management,enhanced presence, commonmanagement and a standards-based software developmentenvironment to existing voiceand video features

� Enabling applications to bedecomposed and distributedacross the network and intro-ducing application sequencing

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Chapter 6

SIP and IntelligentCommunications

In This Chapter� Improving business applications with presence

� Increasing the ease and speed of multimodal communications

� Becoming smarter about prioritizing messages

� Roaming around with location-aware services

� Maintaining privacy

Internet-centric design allows SIP to integrate easily with the Web service environments being developed for many

business-critical applications. For enterprises, this means theintroduction of powerful multi-modal communications, embed-ded as a service within their business applications. It alsomeans that information on user presence can be incorporatedinto application business logic. Communications now becomesa tool not just for users, but also for the enterprise’s criticalbusiness applications.

This chapter looks at intelligent communications as part of unified communications and how SIP facilitates greater productivity for your business and customers.

Presence-Enabled BusinessApplications

Together with Web services and XML-based applications, SIP enables presence within business applications. Desktopprograms that have references to business contacts within

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SIP Communications For Dummies, Avaya 2nd Custom Edition 56them will be able to show the presence of those contacts, onthe screen, within the application. In other words, you don’thave to switch to another application, such as an IM client, toview the presence of a contact.

Applications do not need to be customized to take advantageof new and evolving SIP capabilities. Rather, common libraries(such as dynamic linked libraries — DLLs in Windows, andshared libraries in Linux) contain function calls that knowhow to query presence servers and return rich and meaning-ful information.

Here’s an example: A factory assembly line worker is viewingthe parts needed for an upcoming order in an inventory pro-gram, and notes that there is a shortage. He can immediatelyview the presence of the line manager and procurement man-ager of his own company, and possibly even that of the partssupplier, from within the inventory management applicationitself. Using this data, the worker can quickly determine theavailability of all of the individuals necessary to resolve theshortage issue.

Integration with BusinessApplications

Taking the scenario described in the previous section a stepfurther, SIP enables the line worker to click-to-conference withall the appropriate contacts that are available, initiating a col-laborative conference call to discuss the inventory problem.Open Web services will even allow the inventory applicationitself to check the presence of all relevant contacts, and inter-act with a SIP-enabled audio bridge to proactively out-call tothe parties. This bridge may also include Web or video confer-encing yet remove the need for a human to start the process.Each participant may have mini-applications operating withinhis collaboration software. These mini-applications can pro-vide views back into the inventory application, permittingparticipants to submit queries or make changes in the appli-cation. Cool huh!?

When coupled with unified communications across multipleaccess devices, presence will fundamentally change the waypeople communicate.

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Seamless Use of Multiple Devices

SIP presence can improve the productivity of businesspeopleby enabling them to seamlessly use multiple communicationdevices. Today, most users view the presence status of a con-tact, or “buddy,” only as it pertains to their IM/desktop status,resulting in inefficiencies in the way they communicate. Forexample, they waste time playing voice/e-mail tag and byinstant messaging someone simply to ask, “can u talk?”

SIP provides options to collect and advertise presence andpreferences in a contact list, but the presentity can now be alaptop computer, a mobile phone, or another PC application.With its unified approach, SIP shows the presence for the user,regardless of the device she happens to be using, rather thansimply being “idle” or “out-to-lunch” based only on the pres-ence status of a single application, such as IM.

Also, SIP-enabled devices are smarter and more aware of theirowners’ preferences, including which modes to communicatein depending on a variety of conditions. Regardless of whetheryou’re in the office or on the road, available by phone orIM/chat, or prefer to receive still images on your data-enabledlower-speed mobile phone instead of streaming video, callersonly need to know one “number” to reach you — your SIP AORor logical URI.

Presence refers to the ability for SIP-based communications tobecome smarter by facilitating communications (includingvoice, video, text, and Web) based on a user’s preferences andability to communicate.

Presence-PBX IntegrationWhen SIP/SIMPLE IM is integrated with an IP PBX, desktoppresence can include the on/off-hook status of a contact’sphone, all in the same contact list. This use of presencemeans that a caller can see whether or not someone is on thephone, eliminating blind phone calls or e-mails.

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Combining presence from multiple SIP devices informs thecaller that the user is present or not, but the caller does notneed to know on which number to call. He simply sends a mes-sage to sip: [email protected], and the SIP server startsthe session with the right device (mobile phone, desk phone,IM, video-enabled endpoint) at the right time using the pre-ferred mode of communication (voice, text, video, and so on).

Further OptimizationAs more applications, devices, and networks become SIPaware, real-time IP communications will be further optimized.

For example, presence-aware messaging servers could sensethat the called party is available on his IM client, but not onthe desktop phone that was being called. As a caller leaves avoice-mail message, instead of simply dropping the messagein an inbox, an IM may be sent telling the called party that amessage has arrived and to the calling party that the calledparty has been alerted.

A speech-to-text tool can convert the voice-mail message to atext-based IM or e-mail message (again, depending on thepresence of the recipient). Coupling presence servers withapplication servers adds much more decision-making intelli-gence about where the message should be delivered, improv-ing the speed at which users respond and communicate.

Not only can you convert voicemail messages to e-mail mes-sages with speech-to-text tools, but with Avaya’s DevConnectpartner tools you also can convert e-mails to voice messages.

Communication Systems That Learn

As users acquire more SIP-enabled means of communicationand as applications become SIP- and presence-aware, userscould be crushed under an avalanche of messages, some ofwhich are vital, and others of which are not. So SIP will helpdevices and applications become smarter about prioritizingcommunications.


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With more devices and applications using SIP, the rules forpresence will become increasingly complex. Software applica-tions for managing presence (and, what to do when users orapplications want to communicate at all times of the day andnight) will improve accordingly. More tools to manage andaggregate presence information from multiple sources likelywill emerge.

As presence management tools evolve, they may take on“learning” characteristics (that is, catching on to user habitsfrom heuristics or patterns of usage). Instead of relying on astatic set of business rules, they will adapt to changing condi-tions (such as volume and source of messages), user profiles,security settings, and software capabilities, to make changesto user preferences automatically.

Location-Based ServicesPresence enables new location-aware services for consumersand enterprises. Devices and SIP presence servers can inter-face with cellular carriers’ location-based services (which areused for emergency dialing and E911, among other things) toobtain and act on a user’s approximate geographic location.Also, presence-enabled wireless access points and micro-cellsites can sense that a user is “roaming” within his servicearea and inform SIP presence servers of a user’s approximatelocation.

For example, when a mobile user enters a conference roomwith a presence-enabled wireless access point or micro-cellsite, his presence can be sent to a SIP-enabled room-scheduling system. The system can check to see whether themeeting room is reserved. If it’s not, the system can IM theuser asking if he would like to reserve it and for how long. Ifthe room was already booked, an IM can be sent to the userinforming him that the room is booked and by whom, andoffering nearby alternate locations.

Ensuring PrivacyPrivacy is a major concern as presence is enabled on multipleuser devices. Users need ways to control their environmentsso as not to be buried by spam, spyware, or interruptions.

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With a personal profile manager, users can control presencesettings for all their devices from a secured personal portal.They can set preferences to allow or deny others to see theirpresence based on time of day, location, the device they’recurrently using, and other factors. Such control will help toaddress big-brother type privacy concerns.

Personal profile managers need to be “aware” of privacy lawsand regulations in various parts of the world, and alter theirbehavior accordingly.


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Chapter 7

Ten Reasons to Use SIP-Enabled Solutions by AvayaIn This Chapter� Simplifying communications for your users . . . and your customers

� Improving customer service

� Imagining the possib“ilities” — flexibility, scalability, productivityand more!

� Doing more with less (money)

SIP is a key enabling protocol that can revolutionize yourIP communications infrastructure. As more and more

organizations deploy SIP-enabled intelligent communicationsarchitectures, they are realizing very real and immediate ben-efits. This chapter gives you a quick overview of some of SIP’smost important benefits — and will help you explain thosebenefits to other decision-makers in your organization.

Easier ManageabilitySIP networks are relatively easy to set up and administer, yetinclude many advanced features, such as automated atten-dant, voice mail, and three-party conferencing.

Because SIP is modeled after HTTP as a text-based language, itis easy to learn, develop, troubleshoot, and support. Fromanalyzing network packets to developing custom applications,SIP’s structured language makes it easier for IT systems engi-neers and developers to understand and interpret it. The abil-ity to rapidly deploy new technologies and applications willgive your business a definite competitive advantage.

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SIP Communications For Dummies, Avaya 2nd Custom Edition 62As the industry continues to evolve, so will interoperabilityand manageability across third-party software, devices, andso on, and integrated management across the entire SIP envi-ronment will become even easier!

Turn to Chapters 1 and 2 to find out more.

User-Centric CommunicationsSIP works with the Extensible Messaging and Presence Protocol(XMPP), or presence, to intelligently connect communicatingparties based on their ability and willingness to participate in acommunications session, as well as their preference, based onparameters such as time of day, day of week, desired mode, andtype of caller.

Unified addressing, through the use of a SIP AOR (address ofrecord), provides a single URI (Uniform Resource Identifier)that can be used for routing all communications to a user.Simply put, an AOR allows for a single user identity to bemapped across multiple devices so that people connect withpeople, without needing to know which devices they have andare presently using. This eliminates the need for trackingusers’ multiple phone numbers, e-mail addresses, and IM contact names.

SIP also supports intelligent forking — that is, the ability toroute a communications session to the right person, using the right medium (voice, video, text), on the right device (or application), and at the right time. We explain all of thesekey features in more detail in Chapters 2 and 3.

Native MobilitySIP builds the foundation for native mobility in applicationsand devices for the (not-too-distant) future. As more devicesbecome SIP-capable, users will be able to pick up and go atwill, but still communicate as if they were in their office. Theirpresence and readiness to communicate will still be visible toeveryone.

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For example, SIP’s awareness of a user’s communication capa-bilities will aid international travelers who have to use differ-ent mobile phones and other messaging devices and protocolsin different countries. A caller trying to locate such a travelerneed not know the traveler’s availability or location: SIP willknow how a person can be reached and will facilitate the con-nection. Roam to Chapter 3 to find out more.

Unlimited ScalabilityNo matter the size of your business or the state of your cur-rent telecommunications infrastructure, Avaya has a solutionto fit your intelligent communications and your unified com-munications needs and budget.

SIP-enhanced communications solutions can easily scale froma small branch office deployment to carrier-class enterprisenetworks spanning multiple continents. Whether you’re look-ing to consolidate a mix of legacy TDM PBX telecommunica-tions equipment and evolve your IP communications networkincrementally, or “rip and replace” it all at once, SIP can easilyscale to any deployment scenario and support the futuregrowth of your business. See Chapters 3 and 4 for more infor-mation about the flexibility and scalability of SIP communica-tions architectures.

Better SurvivabilityThe ability to communicate is important to any business, butreal-time communications are critical to the survival of yourbusiness when disaster strikes. SIP-enhanced intelligent com-munications architectures help ensure that disaster recoveryand business continuity plans actually work.

Through SIP, enterprises can control their redundant plat-forms and fail-over paths and, with the advent of both User-to-User Information (UUI) and Network Call Redirect (NCR), SIPtrunks offer feature parity with transport mechanisms such asIntegrated Services Digital Network (ISDN). SIP trunking andsurvivability are covered in Chapters 3 and 4.

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Endpoint FlexibilityEnd users appreciate choice so they benefit from the fact thatthe SIP protocol works on a wide variety of communicationsdevices. Users preferring a desk phone, a unified communica-tions softphone on a PC, or a favorite mobile phone can con-nect to a SIP-based communications network seamlessly andeasily. This means that the same communication functionalityavailable in the office extends to a user via any device.

For example, your desk phone and mobile phone can ringsimultaneously. This enables you to remain in contact withcustomers and business associates no matter where you are.SIP also gives you “mobility within the office,” allowing you tosit down at any desk or in any office, log in, and automaticallydownload your communications profile to your current loca-tion — making it appear as if you were sitting at your owndesk! Call logs, conference calling, call transfer — and otherfeatures you use on your office phone are extended to yourother communication devices and your current location. WithSIP, you get endpoint flexibility without sacrificing endpointfunctionality. Learn more about SIP endpoints in Chapter 4.

Unprecedented InteroperabilitySIP is an open standard defined in RFC 3261 by the IETF, aninternational community of network designers, operators,vendors, and researchers, all concerned with the evolution ofthe Internet architecture and the development of standards toensure the smooth operation of the Internet.

Several working groups, including SIPit, SIPconnect, SIPFoundry, and the SIP Forum — the board of directors of whichincludes Avaya — arrange regular events where companieswith SIP hardware and software products can test interoper-ability with other SIP products. This process helps to promotesmoother integration of SIP products in enterprise networks.The SIPconnect Compliant designation helps customers iden-tify solutions that provide interoperability among multiplevendors. Avaya is one of the first five vendors to be certifiedas SIPconnect Compliant.


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SIP’s ability to work across a range of systems helps enter-prises enjoy more seamless integrations between platforms,devices, and applications, so that companies can rapidlydeploy new technologies, applications, and services. SeeChapter 4 for more information.

Lower Total Cost of OwnershipSIP-enhanced intelligent communications architecturesdeliver lower total cost of ownership (TCO) to businesses andenterprises through SIP trunks. SIP trunks are IP trunks fromservice providers that use SIP for call control and routing,enabling enterprises to create a single, pure IP connection tocarrier clouds. Voice traverses the network just like other IPapplications.

SIP trunks reduce operational costs by enabling the enterpriseto eliminate hardware, software, and recurring networkcharges associated with using traditional PSTN trunks forvoice communications. In fact, Avaya customers typically seea return on investment (ROI) of 6–12 months for their trunkingsolutions. If you’re keen on cutting costs, you can find outmore in Chapter 4.

Enhanced Customer ServiceMore than ever, customer service is a competitive differentia-tor for any successful business. Customers expect anddeserve more than just a call center that routes them to the“next available agent” or an impersonal interactive voiceresponse (IVR) system that routes them in circles until theyget frustrated and take their business elsewhere.

SIP has accelerated the migration from call center to contactcenter, allowing businesses to truly leverage the power of real-time IP communications, including voice, IM, chat, Web, andvideo, to ensure that customer service agents and technicalexperts all have the features, functionality, and informationnecessary to best serve their customers.

Get more information about contact centers and customerservice in Chapter 5.

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Increased ProductivityIt’s easy to imagine how any of the features and advantagesalready described in this chapter could increase individualproductivity just by simplifying your communications world.But SIP can actually do a lot more to improve productivity,increase efficiency, and save the whales! Well, that may be astretch, but SIP can help make your office “greener,” for exam-ple, by facilitating virtual meetings using multimedia collabo-ration tools (voice, video, and data through the Web) such asAvaya’s Meeting Exchange, Avaya Web Conference, and Avayaone-X portal together, thereby reducing the need for costlytravel. With rising fuel costs alone, many companies canexpect an ROI of six months or less using SIP’s conferencing/video conferencing and collaboration capabilities.

By deploying SIP-enabled intelligent custom applications,businesses can offer new services for their customers andimprove existing business processes. For example, we’vealready described the advantages of SIP in the contact centerin terms of customer service, but what about its implicationsfor employee productivity? With SIP-enabled applications, acustomer service agent can be more productive by improvinghis response and resolution times. Rather than simply escalat-ing calls to various technicians, sales reps, or supervisors, theagent can communicate with all the necessary parties over anumber of SIP-enabled applications and platforms while simul-taneously maintaining contact with the customer. This savesvaluable time (and frustration) for everyone involved sincethe customer doesn’t have to repeat the issue each time a callis “handed off” to someone else. You can read more aboutcontact centers in Chapter 5.

Here’s a good way to add the “green factor.” Meeting Exchangewith Avaya Web conferencing and Avaya one-X Portal enhanceemployee productivity, lower cost of travel, and provide amultimedia (voice, video and data through Web) experiencetoday. Or perhaps you simply want calls to automatically findthe device you’re using while working remotely to cut downon the commute. This is all possible today.


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