Whitepaper Sip for Voip

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White Paper:

Advantages of SIP for VoIP

______________________________________________________________

October 2003



White Paper: Advantages of SIP for VoIP October 2003

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Definition

Voice over Internet Protocol (VoIP) defines a way to carry voice calls over an Internet Protocol (IP)

network including the digitisation and packetization of the voice streams. The VoIP standards

enable the creation of a telephony system where higher-level features such as advanced call

routing, voice mail, contact centres, etc., can be utilised.

How does it work?

Historically, telecommunications companies have relied on what is commonly referred to as circuit-

switched technology to transport telephone calls. This technology establishes a 'permanent'

connection between the calling and the called parties for the entire duration of the call. The

problem with circuit-switched technology is that it requires a significant amount of bandwidth

dedicated to each call, and it can only support certain types of calls (i.e. telephone to telephone).

Moreover, the hardware needed to run circuit-switched networks is very expensive, due in large

part to the fact that voice and data services must be carried on different wires and thus needseparate hardware to accommodate the two types of traffic. Naturally, the traditional telephone

companies pass along the costs of building and maintaining a circuit-switched network to the

consumer in the form of higher rates for their telephone services.

As the name implies, VoIP refers to calls that traverse networks using Internet Protocol. The voice

stream is broken down into packets, compressed, and sent toward their final destination by various

routes (as opposed to establishing a 'permanent' connection for the duration of the call),

depending on the most efficient paths given network congestion, etc. At the other end, the packets

are reassembled, decompressed, and converted back into a voice stream by various hardware and

software elements, depending on the nature of the call and its final destination.




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Advantages of VoIP

• New Integrated applications: Because VoIP is digital, it may offer features and services that

are not available with a traditional phone. (See section ‘Examples of additional functionality

made possible by using SIP for VoIP’ below)

• Cost Reduction: No call tolls as it uses your Internet connection. With VoIP you can talk for as

long as you want with anyone that has an Internet connection. You can also talk with many

people at the same time without any additional cost. – Low-cost conferencing.

• Single unified network: As voice is converted into data, it is transported on the data network

and negates the need for a voice network at all. • Open standards: VoIP embraces an open architecture (see below) and provides the flexibility

to integrate with backend systems

• User attributes move with you: As soon as you log on to any VoIP-capable device such as PC,

Mobile Phone, any IP Phone, Satellite Office system, or Home Office adapter.

Cost Reductions

VoIP systems increasingly demonstrate greater cost-effectiveness than traditional voice networks.

As VoIP technology evolves, the cost/benefit ratio, alongside efficiency and flexibility in

implementation, will continue to increase.

The following chart compares the cost of two deployment scenarios for an enterprise of 10,000

phone users, where 50 percent of employees are divided between two large locations and the

remainder among 12 branch offices. Analysis shows that replacing the current PBX with another

PBX increases the cost by approximately 48 percent. However, replacing the existing PBX with an IP

PBX saves approximately 11 percent of the overall replacement cost.

Savings apply not only to enterprises but also to consumers, because service providers can pass the

savings resulting from lower network deployment and maintenance costs on to subscribers.




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What Nokia mobile devices will it work on?

• Symbian 7.0 supports SIP

• Nokia phones that run Symbian 7.0

•

Nokia 6600• Nokia 6620

• Nokia 9300

• Nokia 9500

• Future devices that will support VoIP and VoWLAN

• Zeus – 6830 (Public Announcement: 2nd Nov 04)

• All IP 3G networks will also run VoIP to handset

Issues with VoIP

• Network Latencies / Quality of Service support in the Internet• Session handovers

• Reachablility through firewalls and VPN connections

• Convergence confusion

• Fixed/Mobile

• Wireless

• Call routing between IP, PSTN & GSM networks

• Regulatory issues, - currently unregulated

Open Architecture

Standards bodies

• IETF (Internet Engineering Task Force)

The community of engineers that

standardizes the protocols that define

how the Internet and Internet

protocols work. http://www.ietf.org/

• ITU (International Telecommunications

Union) an international organization

within the United Nations System

where governments and the private

sector coordinate global telecom

networks and services.

http://www.itu.int/home/index.html

Nokia Pro ect: So hia




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Protocols

• H.323 - An ITU Recommendation that defines “Packet-based multimedia communications

systems”. H.323 defines a distributed architecture for creating multimedia applications,

including VoIP

• SIP - Defined as IETF RFC 2543. SIP defines a distributed architecture for creating multimedia

applications, including VoIP

• MGCP - Defined as IETF RFC 2705. MGCP defines a centralized architecture for creating

multimedia applications, including VoIP

• H.248 - An ITU Recommendation that defines “Gateway Control Protocol”. H.248 is the result

of a joint-collaborate with the IETF. H.248 defines a centralized architecture, and is also

known as “Megaco”

H.323 vs. SIP

H.323 is actually a suite of protocols, and incorporates many individual protocols that have been

developed for specific applications.

H.323 Protocol Suite

Video Audio Data Transport

H.261

H.263

G.711

G.722

G.723.1

G.728

G.729

T.122

T.124

T.125

T.126

T.127

H.225

H.235

H.245

H.450.1

H.450.2

H.450.3RTP

X.224.0

Full implementation of H.323 requires a lot of overhead. SIP is a much more streamlined protocol,

developed specifically for IP telephony. Smaller and more efficient than H.323, SIP takes advantage

of existing protocols to handle certain parts of the process. For example, Media Gateway Control

Protocol (MGCP) is used by SIP to establish a gateway connecting to the PSTN system.

SIP allows two or more participants to establish a session consisting of multiple media streams

using text-based request and response messages. A user, termed a SIP endpoint, is addressed by a

SIP URL in the form of an e-mail address, such as sip:[email protected] or sip:[email protected]. The

application used for communication is called the user agent (UA). Call initiation and modification isdone through INVITE messages of SIP. Two endpoints can communicate with each other directly, or

they can make use of a SIP entity called the redirect server. The user first sends the request for call

initiation to this server, which queries a location service to retrieve the IP address and port of the

other user. The location service keeps track of the current location of the users.

Since the underlying elements of SIP are so much like HTTP, creating network-based services such

as time-dependent call forwarding is quick and straightforward. Developers can design and




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implement new SIP-based voice services just as quickly and easily as they develop web pages; and

by not requiring major hardware upgrades to application servers, but rather enabling new

software-based services using SIP, service providers can reduce the time associated with deploying

new features from months to days. For subscribers, this means ever-improving communications

service, plus lower initial and recurring telephone service costs.

Examples of additional functionality made possible by using SIP for VoIP

• Ringing tone and caller image is delivered within signaling (SIP transports MIME payload xxx)

• URLs can be passed within signaling, seamless email/media-on-demand integration (e.g. call

may be forwarded into rtsp URL: video mail answering service)

• Receive voicemail messages via email

• Possibility to create richer profiles "If caller is Bob, send soccer_results.html file to him (in SIP

payload or by mail)"

• Simple scripts: "If the time is past 4 p.m. and caller is boss, forward to voice mail."

• Another form of SIP extension work is to define the usage of SIP in new context. For example,

there is on-going work in IETF to use SIP to control networked appliances (e.g. “turn the lamp

on”). New method (DO) has been proposed for this idea. Similar ideas (using SIP for new kind of

services) will probably follow.

SIP is generic protocol for every IP capable access networks. There lies the opportunity for Nokia to

win more business in fast growing industry.

SIP and HTTP form a powerful architecture for application development community. The snowball

effect grows the market as already existing developer community finds it easy to implement

compelling services for terminal users.

Cisco Support

Cisco has broad support for SIP across its entire product line:

• IOS Gateways: 1751, 7200, 2600, 36x0,

AS5300, AS5350, AS5400 Series,

AS5850

• Call Agents/Soft switches: BTS 10200,

PGW2200

• Endpoints: ATA 186, 7940, 7960

• Infrastructure: Cisco SIP Proxy Server,

PIX Firewall, IOS NAT

Cisco-driven solutions are being deployed

today with Cisco SIP Global Long Distance

having been deployed by several carriers

including some with integrated H.323

gateways.




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Cisco-backed SIP IP Business Solutions are starting to emerge. SIP voice application solutions have

been deployed by 5+ carriers (including Windows Messenger PC-to-Phone support)

Microsoft Live Communication Server 2003

For years Microsoft has had computer telephony features embedded in its operating systems in

products such as NetMeeting, an H.323-videoconferencing application, and Exchange Conferencing

Server, for managing data, voice and videoconferencing.

Windows XP brought along Microsoft Windows Messenger, which turned some heads in the

telecom community for its use of SIP.

Speculation about what Microsoft will do in telephony grew when company representatives began

showing up at industry events such as Voice on the Net (VON), and later when it announced

development of its Real Time Communication (RTC) Server, code-named Greenwich. RTC is renamed

Live Communication Server 2003. The server acts as a control node for managing conferences

among SIP clients.

Windows CE 5.0 includes a greater VoIP focus so that IP phone

and other device makers, as well as service providers, can

expand their VoIP applications.

The Windows CE 5.0 SIP stack is interoperable with Microsoft

Windows XP and Microsoft Live Communications Server,

enabling collaboration and communication through instant

messaging and providing status information (presence)

between desktop computers and Windows CE–based IP phones.

In addition, Microsoft Visual Studio .NET for native Microsoft

Win32–based applications, or for managed applications builton the Microsoft .NET Compact Framework, provides an easy-to-

use tool to efficiently develop feature-rich IP phones and VoIP

devices.

Beyond the new feature, over the past 12 months Microsoft has

focused on expanding its VoIP partners for Windows CE. At VON,

it announced 13 new VoIP manufacturer partners focused on embedding Windows CE into IP

phones and other devices as well as a host of new system integrators.

Further reading

See the following resources for more information:

• RFC 3261: SIP: Session Initiation Protocol:

http://www.ietf.org/rfc/rfc3261.txt

• SIP Extensions for Presence:

http://search.ietf.org/internet-drafts/draft-rosenberg-impp-presence-00.txt




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• Nokia Sofia IP Telephony Software suite:

http://iptel.research.nokia.com/sofia/

• Microsoft Real-Time Communications: Protocols and Technologies:

http://www.microsoft.com/technet/prodtechnol/winxppro/plan/rtcprot.mspx

• Cisco SIP:http://www.cisco.com/warp/public/cc/techno/tyvdve/sip/




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About Nokia

Nokia is the world leader in mobile communications, driving the growth and sustainability of the broader

mobility industry. Nokia is dedicated to enhancing people's lives and productivity by providing easy-to-use

and secure products like mobile phones, and solutions for imaging, games, media, mobile network operators

and businesses. Nokia is a broadly held company with listings on five major exchanges.

For more information, please visit http://www.nokia.com/forbusiness .

AmericasNokia

313 Fairchild Drive, Mountain View, CA 94043Tel: 1 877 997 9199

Email: [email protected]

Europe, Middle East and AfricaNokia

Nokia House, Summit AvenueSouthwood, Hampshire, GU14 ONG, UK

Tel UK: +44 161 601 8908Tel France: +33 170 708 166

Email: [email protected]

Asia PacificNokia

438B Alexandra Road#07-00 Alexandra Technopark, Singapore 119968

Tel: +65 6588 3364Email: [email protected]

www.nokia.com

Copyright© 2004 Nokia. All rights reserved. Nokia and Nokia Connecting People are registered trademarks of Nokia Corporation.Other trademarks mentioned are the property of their respective owners. Nokia operates a policy of continuous development.Therefore we reserve the right to make changes and improvements to any of the products described in this document withoutprior notice. Under no circumstances shall Nokia be responsible for any loss of data or income or any direct, special, incidental,consequential or indirect damages howsoever caused. .

__________________________________________________________________________



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