1 © 2001, Cisco Systems, Inc. Technology Overview - Voice Gateway SS7 Interconnect for Voice...

1© 2001, Cisco Systems, Inc. Technology Overview - Voice Gateway

SS7 InterconnectSS7 Interconnectfor Voice Gatewayfor Voice Gateway

Key Technologies for PSKey Technologies for PSProject and Program ManagersProject and Program Managers

Created and Presented by Steve WellsCreated and Presented by Steve Wells

2Technology Overview - Voice Gateway

What’s an SS7 Voice Gateway?

Why’s that important?

What’s it all about?

• Challenges

• Concepts

• Components

• Layout

SS7 Interconnect forSS7 Interconnect forVoice GatewayVoice Gateway


The Changing WorldThe Changing World

Telecommunications is undergoing rapid change.

The infrastructure is Old World.

The needs and opportunities areNew World.

POTS and PANSPlain Old Telephone Service

Pretty Amazing New Services


Old World InfrastructureOld World Infrastructure

Voice network and data networkon the same wires.

• Circuit switched lines.

• Voice traffic on voice lines.

• Packet data on voice lines.

• Optimized for voice.

• Voice calls average 6 minutes.


New World ChallengesNew World Challenges

1980’s and 90’s - traffic growth

• Voice grew linearly.

• Data grew exponentially.

• Now: data traffic = 5 × voice traffic.

• Data traffic: brief bursts, then quiet.

• Data on voice lines wastes bandwidth.

• Calls average 32 minutes.


New World ObjectivesNew World Objectives

Data on packet data lines.Voice as packet data (VoIP).Optimize for data.

Statistical multiplexing provides efficient bandwidth use.

Business NeedsConsolidate 2 networks (voice and data) into 1.Provide access for data calls.

Consumer MarketConsolidate entertainment (TV), telephone, and Internet access into one communications network.


Switching Network

Line Concentration

Digital Trunk Subsystem

Call ControlConnection Control

Features

Common ChannelSignaling Complex

AdministrationMaintenance

Billing

TDM Switchby SNALE TDM Switchby SNALE

Services PlaneIN Service Logic AAA, Address Resolution

ServiceLogic

Open Packet TelephonyOpen Packet TelephonyOpen Packet TelephonyOpen Packet Telephony

SCP Partners

VCO4K

UnifiedComm.

VSCSignaling Controller

Call Manager

IN / AIN / CTI

Call Control PlaneSignaling and Call ControlService Access FunctionSwitch-Based Service LogicEnd-to-End VoiceServices

DefinitionConversionSimulatorConfigurationAnalyzer

InterworkingTool Set

CallLogic

Full Access to Existing and New

IN/AIN Products

Flat Efficient Transport Layer

User Programmable

Call Control

Connection PlaneConnection NegotiationTranscodingBearer SwitchingMedia Control: RTP, PNNI, Etc.

SwitchingLogic

MGCP / SIP / H.323


Signaling System 7Signaling System 7

Out of Band Signaling

• More signal data at higher speeds.

• Signals sent anytime.

• Signals to network elements with no direct trunk connection.

• Circuit resources are not used until the connection can be completed.


Signaling System 7Signaling System 7

Voice as Packet Data

• More voice data on fewer lines.

• Non-voice data can share the line.

• A voice packet can go down any trunk.No tying up dedicated switches to keep calls connected.

• Phones and calls with special features.


SS7 ArchitectureSS7 Architecture

SSP Service Switch Point Starts/ends callAccess end points and controls.Bridge unmated pairs.Cross to mate for reliability.Diagonal to another network.Extended to non-home pair.Fully associated Service Points.

A-Links - F-Links

PSTN SS7Signaling Network

BB

B B

BB

F

F

EE A A

A

A A

AAA

A A

D

D

D

CCCC

SSP SSP

SSP SSP

STP

STP

STP

STP

STP

STP

STP

STP

SCP

SCP

STP Signal Transfer Point Routes call

SCP Service Control Point “Specials” database


The technical challenges are immense.

Voice over IPVoice over IP

Performance must be great. Users will: Demand a high Quality of Service. Assume calls will stay connected. Count on phones to work during power failures. Hold fully duplex conversations. Presume privacy and security. Dial in to the Internet. Send and receive Faxes.



Infrastructure Challenges

• Old wire.

• Existing electronics / hardware is getting old.Not state of the art.

Tired and failure prone.

• Huge investment and effort needed to install new lines and equipment.



Security and Reliability Challenges• Callers must send and receive only their own

voice packets.

• DES Security -- Data Encryption Standard.

• IP phones must have battery backup, e.g. 4 hours.

• Low power consumption components for usewhile self-powered.

• Non-volatile memory to maintain phone functions.



Latency (Delay) Challenges Accumulation Delay - to collect a frame of voice data.

Processing Delay - to convert a frame into packets.

Network Delay - to transmit packets across a network.

Polling Delay - till the head end asks for more packets.

Echo - must be cancelled with digital filtering.

Jitter - the packets don’t arrive at regular intervalsif they’re even in the right order!

Lost packets - must be interpolated or packets must have redundancy. Voice packets can’t be resent a few seconds later like lost internet data. (Think about it.)



Phone Billing Challenges

Billing is handled by software call agents, routing through a voice enabled cable modem, or a utility box Broadband Telephony Interface.

Recurring line charges.

Local, long distance, and international calls with varying rates based on day, time of day, and actual connect duration.

Per use charges: directory assistance or call return.

Special per minute services:C++ Programmers’ Psychic Hotline


What makes VoIP possible? Digital Signal Processing (DSP) Hardware is

incredibly fast and getting faster!

Talented engineers at Cisco are top 10% people!


Fax Challenges Precise timing is needed or the call will drop.

Lost data packets can drop the call, too.

Nobody said VoIP telephony was easy!


Solution ComponentsSolution Components

SLT

AS5x00

Signaling Controller

AKA: Cisco SC2200

Host

Signaling Link Terminal

AKA: SLT

Cisco Voice Gateway

Based on Sun Netra 1400s and

1800s

Based on 2611 w/ Special Cisco IOS Image for the SLT

Cisco IOS = 12.1(3)T

Based on AS5300 w/ 12.1(2a)T2 or Later

Supports over 60 Different ISUP Variants into

Q.931+ over IP

Supports Terminating A or F Links and

Encapsulating MTP 3 Layers and aboveover IP; Provides

Muxing F Links off E1s

H.323 Voice-over-IP Media Gateway Responsible for

Voice Packetization, H.323 Signaling

Diagram Description Details Purpose

Cisco SC2200

NodeCisco SC2200

Host


Universal Access ServersUniversal Access Servers

Low End Mid Range High End

Density

Cisco AS25008 or 16Async Ports

Cisco AS5300 (Access Server)4 or 8 T1/E1/PRI192/240 PortsAnalog/ISDN

CiscoAS5800(Access Server)48 T1/E1/PRI or2 CT3Up to 1440 PortsAnalog/ISDN

CiscoAccessPathTS3(Access Server)168 T1/E1/PRI4032/5040 PortsAnalog/ISDN


CPE Software Features

CPE Software Features

• PPP Multilink

• PPP extensions

DIAL ACCESS Software Features

DIAL ACCESS Software Features

• Integrated V.90 Modem & ISDN Support

• Dial Access Stacking Architecture (DASA)

• SS7 Integration

• AAA Support

• AAA

• Web Caching Via WCCP

• IGP Support/BGP Peering

• MPLS/Traffic Engineering

• IP QoS Support

• IGP Support/BGP Peering

• MPLS/Traffic Engineering

• QoS Support

POP Software Features

POP Software Features

CORE Software Features

CORE Software Features

Dial Internet Access Dial Internet Access Software FeaturesSoftware Features

DialPlatform

Cache

DistributionRouter

CoreRouter

IP CorePSTN

Layer 2Interconnect


SS7 Solutions ProvideSS7 Solutions Provide

• Opportunity for revenue sharing

• Service portfolio

A new interface for access servers

Allows selective acceptance of calls (white/black list screening)

• Target markets

Lower interconnect and capital costs enable down-market expansion

SS7 is often more readily available than PRI for faster time to market

• Geographic reach

Certain countries require SS7 interconnect

• Network scale

SS7 enables more revenue minutes per circuit (faster call setup time)

Cisco SC2200Cisco

SC2200

AS5X00AS5X00

VoIP Network

SS7Network

PSTN IMT

SS7 Links

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