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www.tekelec.com | 1

SIP Signaling RouterApplication Handbook

The exclusive guide for solving next-gennetwork challenges with SIP

Upgrade Your Next-Gen Network Today


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The intent o this handbook is to provide operators with a useul reerence guide or

how they can use a SIP Signaling Router (SSR) to solve many o their next-generation

network challenges.

Found at the heart o most global networks, Tekelecs market-leading, mission-critical,high-perormance network solutions enable the secure and instant delivery o calls

and text messages or more than one billion mobile and ixed-line subscribers. The

companys signaling and session management solutions allow telecom operators to

manage diverse applications, devices, technologies and protocols, across existing and

evolving networks, to meet the demands o todays consumer. Tekelec ensures telecom

operators have a clear migration path to SIP-based IP networks, and whatever comes

next, with the exibility to deploy solutions at a pace dictated by their business needs.

For more inormation please call

888.628.5521 or +1.919.460.5500

Visit our web site at www.tkc.c

The inormation presented is or demonstration purposes only and is not intended to represent any particularcompany. Any similarities are purely coincidental. Actual perormance results depend on particular networkconfigurations, capacity and other technical requirements.


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Intrdctin

The beneits o next-generation, voice over Internet

protocol (VoIP) networks are compelling or operators

worldwide. Deployments cut across all types o telecomoperators rom the largest incumbents to the smallest

regional players. Providers see VoIP and session initiation

protocol (SIP)-based services as an opportunity to cut

their operating expenses and boost their bottom line

with new revenue. Delivering VoIP and SIP services to

consumer and enterprise customers enables providers

to expand their subscriber base. And, SIP acilitates theinterworking o real-time applications with voice and

video to create new, multimedia services.

However, as VoIP and SIP trac and applications grow, so

do the requirements placed on the network to support

them. Many operators are discovering that their current

next-generation networks (NGNs) are based on an out-

dated, voice-centric, sotswitch architecture, which does

not support multimedia services, access independence,

backward network compatibility or network growth.

www.tekelec.com | 3

Tbl of Contnts

Introduction 3

The Challenge 4

SIP Signaling Router 4

Use Case 1: Enhanced Application Server Selection 5

Use Case 2: SIP Trunking 9

Use Case 3: SIP Number Portability 14

Use Case 4: Centralized SIP Routing 18

Use Case 5: Specialized SIP Proxy 22

Summary 26

About Tekelec 27

Appendix-1: Acronyms 27


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Th Chng

Unlike signaling system 7 (SS7) and Internet protocol

multimedia subsystem (IMS) networks, which are

hierarchical, there is no separate signaling and session

control layer at the core o the NGN. From a signaling

perspective, each NGN network element must handle

all application-layer related tasks such as routing, traic

management, redundancy and service implementation.

All possible routes must be deined at each node,

creating a logical, mesh-network routing architecture.

Expanding the NGN without a ramework that ooads

session and signaling tasks rom the edge elements iscomplex and costly.

SIP Signing Rtr

Tekelecs SIP Signaling Router (SSR) solution, a SIP

proxy with enhanced routing capabilities, creates a

signaling and session control ramework or NGNs by

implementing SIP routing unctionality in the corenetwork. The SSR enhances routing capabilities and

increases service and network exibility by relieving

endpoints o session management duties. The resulting

architecture allows the NGN to grow systematically

in response to increasing demand or VoIP and

multimedia services.

The SSR solution is based on 3rd Generation Partnership

Project (3GPP) speciications and ofers adaptations or

interworking with non-3GPP-compliant IP environments.

It provides seamless interworking and creates an

evolution path to uture technologies such as IMS,

long term evolution (LTE) and WiMAX.

This handbook explores ive use cases that demonstrate

the applications and associated beneits o deploying

Tekelecs SSR in NGN networks. They include:

Enhancedapplicationserverselection

SIPtrunking

SIPnumberportability

CentralizedSIProuting SpecializedSIPproxy

4 | SSR Application Handbook


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USe CaSe 1:

eNHaNCeD aPPlICaTIoN SeRVeR SeleCTIoN

Problm:

The operator, Company A, provides VoIP services to small

enterprise customers, using a SIP enterprise application

server (AS) and SIP phones. The SIP AS provides voice

eatures such as ind-me, ollow-me and simultaneous

ring. Each subscriber must be identiied and registered

on the SIP AS platorm. Prior to shipping, Company A

conigures each SIP phone with the address o the SIP

AS, which is voipsvc.CompanyA.com. The SIP phone

uses this address or registration and to make voice calls.

Company A IP Network

VoIP AS

Hosting Subscriber

A through Z

Address =

voipsvc.CompanyA.com







Figr 1: Sscrirs r idntifid nd rgistrd n th SIP aS ptfr.


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Company A IP Network

voipsvc1.CompanyA.com




Sub A-F Sub G-M Sub N-S Sub T-Z

Company A has developed a solid reputation or its

service quality, and its subscriber numbers have grown

signiicantly. To support current and uture growth,

the company deploys three additional application

servers, each with its own address. Subscribers are

now distributed among our application servers.

Figr 2: Hw cn Cpn a si p sscrirs t th ppictin srvrs?


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www.tekelec.com | 7

This new coniguration poses a number o problems.

With our application servers in the network, how does

the SIP phone know which AS to request? And, since

the SIP AS address is conigured on the SIP phone,

each time a customer is assigned to another application

server, the address programmed on the SIP phone must

be reconigured.

From a technical perspective, the problem is the result

o a tight coupling between the SIP endpoints the SIP

phones and the SIP AS. Any changes to the physical

network, such as adding a new application server, have adirect impact on the way the SIP phones access a service.

As a result, complex provisioning is increasing operational

costs, and quality o service is being impacted by service

disruptions due to provisioning errors. Company A needs

a solution that will allow the company to:

Managegrowthwithoutsacrificingqualityofservice.

Makechangestoitsapplicationserverassignments

without reconiguring the phones that are already

in service.

Solution:

Company A deploys the SSR solution in its network to

shield the endpoints rom changes in the physical

network. Through a process called abstraction, the

phones are decoupled rom direct knowledge o the

complex and changing network. The SIP phones just

have to be conigured with a single abstract address

voipsvc.CompanyA.com. Endpoints send requests to

the SSR, which resolves the voipsvc.CompanyA.com

address to the appropriate SIP AS platorm and routes

the request to that platorm.Since the endpoint only deals with an abstract view

o the network, it is not impacted by changes in the

physical network such as adding a new application

server. Regardless o changes in the SIP AS topology,

the address on the SIP phone remains the same, and

no reconiguration is necessary.


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Bnfits:

By deploying the SSR solution, Company A:

Createsaexiblearchitecturefreeofendpoint

constraints. Savescapitalcostsbysimplifyingsubscriber

management and maximizing the eiciency

o application servers through load sharing

and exible subscriber management.

Canexploredierentbusinessmodelssuch

as using third-party, hosted services.

Createsafoundationformultimediaservices.

Sub A-F Sub G-M Sub N-S Sub T-Z

Request to voipsvc.CompanyA.com

SSR

Forward the requestto correct AS platformwhere Nick is assigned

Consult internal routingpolicy A numberdirected routing

Nick





Figr 3: endpints r shidd fr chngs in th phsic ntwrk.


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www.tekelec.com | 9

Company B

POP POP POP

Local Network

2

Local Network

3

Local Network

4

Local Network

1

POP

PBX

PBX

USe CaSe 2:

SIP TRuNKING

Problm:

Company B is a long-distance (LD) operator that

provides service to local phone companies. The

company has a number o points o presence (POPs)

conveniently located near the networks it serves. The

local phone companies provide service to enterprise

customers via primary rate interaces (PRIs) to private

branch exchanges (PBXs).

Figr 4: Cpn b prvids srvic t c phn cpnis.


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With deregulation, Company B decides to enter the local

service market and ofer ixed-line services directly to

enterprise customers. Company B can deliver substantial

savings by cutting out the middle men, the local phone

companies. With SIP trunking, Company B can enable

business customers with IP PBXs to use their Internet

connection to provide of-net service. In addition to

voice services, Company B wants to create a oundation

or delivering multimedia services to its enterprise

customers in the uture.

Company B aces several challenges and needs a solutionthat will enable the company to:

Provideenterprisevoiceserviceimmediatelywhile

laying the oundation or uture multimedia SIP

services.

Maintainlowstart-upcostwithoutcompromising

the long-term plan.

The company could implement a sotswitch-based

solution, but that alternative has a number o

disadvantages. Since it is based on a per connection

cost model, the approach can become costly very

quickly. The sotswitch-based model is voice centric

and may not be suited to delivering multimedia services.

Sotswitch implementations usually are deployed with

the switch vendors choice o application server, so it is

diicult to gain the economy o a best-o-breed solution.


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www.tekelec.com | 11

Figr 5: SIP trnking ns ntrpris cstrst s thir Intrnt cnnctin fr ff-nt srvics.

Company B

POP POP POP

Local Network

2

Local Network

3

Local Network

4

Local Network

1

POP

IP PBX

IP PBX

SIP Trunking directly

from Enterprise to

Company B


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Solution:

By implementing Tekelecs SSR solution, Company B can

use a session-based approach, which balances cost and

exibility. The SSR creates a SIP signaling and session

control layer that routes on-net calls (IP PBX to IP PBX)

over the VoIP network, of-net local calls (IP PBX to local

numbers), and of-net long-distance calls (IP PBX to

long-distance numbers). A public switched telephone

network (PSTN) gateway handles IP PBX to PSTN calls.

In the process, the company also creates a ramework

that is based on Internet Engineering Task Force (IETF)

and 3GPP standards or the delivery o multimedia

services. The solution enables Company B to create a

volume-based cost structure and reduces costs by

allowing the company to select best-o-breed

application servers.


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Figr 6: SSR crts SIP signing nd sssin r t rt n- nd ff-nt cs.

Bnfits:

With the SSR solution, Company B can compete

with local telephone companies by ofering

SIP trunking to enterprise customers. The

company receives additional beneits that include:

Layingthefoundationformultimediaservices.

Savingmoneybymaximizingthecapacityof

application servers through load sharing and

exible subscriber management.

CreatingaSIPpeeringpointtointerconnect

with other VoIP providers.

POP POP

Local Network

2

Local Network

3

Local Network

4

Local Network

1

POPIP PBX

IP PBX

Easily addbest-of-breedSIP AS fornew services

SIP AS

POP

PSTNGW

SSR


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USe CaSe 3:

SIP NumbeR PoRTabIlITy

Problm:

Company C, a long distance operator, entered the localcalling service market by deploying Tekelecs SSR solution

to build a SIP trunking inrastructure. Company C is an

operator in the call routing sequence immediately prior

to the terminating operator. So, its customary or

Company C to perorm number portability, or NP service,

or VoIP calls rom their SIP trunking service. The company

could simply dump calls onto the PSTN gateway anduse its existing time division multiplexing (TDM)-based,

number portability solution to route calls to the correctnetwork. However, to do so, there must be adequate

intelligent network capacity to handle the increased

traic, and the terminating network must be TDM. I the

terminating number is an IP PBX or belongs to another

VoIP provider, the call must be shuttled rom VoIP to TDM

and back to VoIP again. Running pure VoIP calls over the

TDM network to perorm NP wastes capacity on the PSTNgateway and degrades voice quality.


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Figr 7: Cs dstind fr VIP prvidr r IP PbX st rtd vr th TDm ntwrk.

POP POP

VoIPOperator

Local Network

2

Local Network

3

Local Network

4

Local Network

1

POP

IP PBX

IP PBX

919-460-5500POP

919-460-5500

NPDB

Ported in

from NW2

SSRPSTN

GW


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Solution:

Company C could replicate an NP solution in its SIP

domain, but that is an expensive approach. A more

cost-efective and eicient method is to make the

TDM-NP solution available to the SIP network. The

TDM-NP database can be accessed using the SSRs SS7

access eature. This capability allows the SSR to augment

its routing capabilities with data rom the SS7 domain.

The SSR provides NP services to the SIP domain in one

o three ways:

Numberportabilitycorrectedforwardingproxy:TheSSR receives a request rom an originating user agent

(UA) such as an IP PBX. The SSR perorms the NP

unction and then orwards the request to the

appropriate SIP endpoint or call completion.

Numberportabilitycorrectedredirectserver:The

originating UA sends a request to the SSR, which

perorms the NP unction to determine the end-

point destination. The SSR then sends a SIP redirect

message to the UA that instructs the UA to orward

the request to the appropriate destination.

Numberportabilitycorrectedforwardingapplication

server: Ater receiving a request rom the originating

UA, the SSR perorms the NP processing to locate

the called number. It modiies the request with thedestination inormation and sends it back to the

originating UA. The UA then proxies the call to the

appropriate SIP endpoint.


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Bnfits:

SinceNPisdeployedthroughastandardSIP

ramework, the approach can be used in the

next-gen network as well as a uture IMS network.

End-to-endmediatransparencyismaintained,so

the NP solution can be applied to voice service

AND any other type o multimedia service such as a

video or IPTV.

TheSS7-accessfeatureusedfortheNPapplicationalso

supports access to other SS7-based applications like

toll-ree and message-waiting indicator as well as HLRmobility inormation or wireless operators.

Figr 8: SSR ccsss TDm-NP dts sing SS7 ccss ftr.

SIP Domain

TDM Domain

SIPDevice

TDMDevice

SIPDevice

NPDB

SIP SIP

AIN/INAP

Media Transparency

AIN/INAP

SSR


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USe CaSe 4:

CeNTRalIZeD SIP RouTING

Problm:

Company D, a Southeast Asia hub provider, ofers

voice transit and signaling services to ixed-line

and mobile operators. The company deployed

sotswitch technology to take advantage o lower

IP transport costs. Sotswitches, which serve as

POPs, are installed throughout Southeast Asia

in a ully meshed ramework. Every switchmust be deined in the translation table o

every other switch.

Figr 9: Sftswitchs, srving s PoPs, fr f shd rchitctr.

TDM Client

TDM Client

TDM Client

TDM Client

TDM Client

TDM Client

TDM Client

TDM Client SIP Client

Company D Network

TDM Client

SS POP

SS POPSSPOP

SSPOP

SSPOP

SS POP SS POP

SS POP

POP

Voice

Text

Multimedia


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Company D would like to expand its network to serve

other Asian markets. The company also plans to enhance

its portolio by ofering transit services or text messaging

and multimedia applications. And, it would like to

provide SIP peering as an alternative to TDM to otherVoIP providers.

The new business plan presents a number o issues or

the meshed, sotswitch network. Expanding the network

requires the addition o new sotswitches to increase

capacity. Provisioning is complex as each new piece o

equipment must be provisioned with the routing entriesor all o the existing sotswitches. And, the existing

sotswitches must be updated with the routing entries

or the new equipment. Since routing is based on

pre-deined SIP trunks, route management becomes

increasingly complex as the network expands. Service

and subscriber data are tightly coupled with the

sotswitch, making it diicult to change an existingservice or add new applications uniormly.

Company D must address several complex issues related

to growing its network, including how to:

ExpanditsnetworkANDkeepnetworkoperation

costs low.

Oervoiceandnon-voiceservicesANDreduce

capital costs.

Preventdegradationasmediaowsthrough

its network.

Like many operators, Company D views these as three,

unrelated challenges. As a result, they deploy multiple,

point solutions, which increase long-term CAPEX andOPEX. However, i Company D took a holistic view o the

network, they would see that they are, in act, all related.

A piecemeal approach will not address the challenges

because solving one problem likely worsens another.


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Solution:

Company D creates a SIP-based reerence architecture

over its existing network by deploying the SSR as a

SIP proxy. With this approach, all calls are routed by

deault rom the sotswitch to the SSR. The SSR makes

layer-5 SIP routing decisions based on advanced routing

algorithms and orwards the request to the appropriate

SIP destination.

Bnfits:

The company now has a centralized SIP signaling

and session control ramework that:

Actsasaroutemanagerforallofthesoftswitches,

relieving them o routing unctions.

Eliminatesthemeshnetwork,sothereisnolonger

a need to provision translation tables on each and

every switch.

Maintainsend-to-endmediatransparencysothe

endpoints can communicate using any media

voice, text, video, or data streaming. Preservesmediaqualitybecausethereisno

decoding/encoding required in the network.

ProvidesacentralizedSIPmonitoringpoint.


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Figr 10: SSR crts SIP-sd rfrnc rchitctr.

Company D NetworkTDM Client

TDM Client

TDM Client

TDM Client

TDM Client

TDM Client

TDM Client

TDM Client

SIP ClientTDM Client

SIP Client

SS POP SS POP

SS POP

SS POP

SS POP

SIP SignalingRouter

SIP SignalingRouter

POP

SSPOP

SSPOP

SSPOP

POP


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USe CaSe 5:

SPeCIalIZeD SIP PRoXy

Problm:

Company E is a provider o ixed and mobile services.

The company maintains its operation as two, separate

businesses Company E Telecom and Company E

Mobile. The ixed and mobile networks are loosely

coupled through TDM peering. Each network views

the other as a oreign network.

Figr 11: Cpn es ntwrk fr cnsidtin.

HLR

MSC SMSC

SCP

Switch

Softswitch

Company E Mobile

Company E Telecom


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Company E wants to consolidate the networks and create

a single operating entity Company E to reduce its

operating costs. The company also plans to expand its

oferings with integrated mobile and ixed services,

mobility solutions or ixed-line enterprise customersand uture multimedia services.

Since Company E already has some SIP deployments in its

ixed-line network, it has decided to take the opportunity

to upgrade its underlying wireless network technology

to SIP as well. By doing so, the company can lower the

cost o network integration and create a uture pathor multimedia services. Company Es plan is to cap its

existing TDM-based mobile switching centers (MSCs)

and begin deploying SIP-capable mobile sotswitches.

Its strategy is to interconnect the mobile sotswitches

with the existing wireline SIP sotswitches.

Figr 12: Cpn e cnncts i nd

wirin sftswitchs with SIP tchng.

Company E


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However, Company E aces a problem common to many

operators: diferent vendors supply the mobile and

landline sotswitches. The sotswitches are unable to

establish sessions because the vendors use diferent

SIP implementations. The two vendors reuse torecognize the interoperability issue as a problem, but

they gladly will provide a customized solution to

Company E i the company is willing to pay or it.

Company E is caught in a situation called vendor lock-in.

As long as the company deploys equipment rom

a single vendor, there is no problem. But, whenit introduces equipment rom another vendor,

interoperability problems arise. This situation

creates signiicant challenges or the company.

Howcanitsolvetheinteroperabilityissuewithout

spending an excessive amount o money or a

customized solution or being orced to purchase

all o its equipment rom a single vendor?

Howcanthecompanyavoidthesameproblem

in the uture as it brings new elements rom other

vendors into the network?

Solution:Company E deploys the Tekelec SSR as a protocol

mediation point between the diferent vendor

products. This approach creates an architectural

solution that is independent o the endpoints and

eliminates interoperability problems. The SSR solution,

which is deployed in the signaling layer, can be

implemented in one o two ways: directly on the SSR,or by having the SSR proxy to an external application

which provides the protocol mediation.

With the SSR solution, Company E creates a SIP-based,

NGN reerence architecture over its existing network.

In this role, the SSR acts as a proxy server to route SIP

traic between the mobile and landline sotswitches.It also orms a mediation point that ixes protocol

variations on the y between the sotswitches.


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Bnfits:

Company E now has the SIP signaling and session control

ramework that solves its immediate interoperability

needs and:

Createsthefoundationforamulti-vendor

environment and uture multimedia services.

Enablesthecompanytochoosebest-of-breed

products, avoiding vendor lock-in.

ProvidesacentralizedSIPmonitoringpoint.

Figr 13: SSR cts s ditin pint twn sftswitchs nd rts trffic twn th.

Fix up Fix upSSREndpoint

Equipment

from Vendor 2

Not My Fault

Endpoint

Equipmentfrom Vendor 1

Not My Fault


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about Tklc

Found at the heart o most global networks, Tekelecs

market-leading, mission-critical, high-perormance

network solutions enable the secure and instant delivery

o calls and text messages or more than one billion

mobile and ixed-line subscribers. The companys

signaling and session management solutions allow

telecom operators to manage the diverse applications,

devices, technologies and protocols, across existing

and evolving networks, to meet the demands o todays

consumer. Tekelec ensures telecom operators have a

clear migration path to SIP-based IP networks, and

whatever comes next, with the exibility to deploy

solutions at a pace dictated by their business needs.

For more inormation, please visit www.tkc.c.

appndix-1: acrns sd in this dcnt

3GPP 3rd Generation Partnership Program

AS Application server

HLR Home location register

IETF Internet engineering task orceIMS Internet protocol multimedia subsystem

IP Internet protocol

IP PBX Internet protocol private branch exchange

LD Long distance

MSC Mobile switching center

NGN Next generation network

NP Number portability

POP Point o presencePRI Primary rate interace

SCP Service control point

SIP Session initiation protocol

SMSC Short message service center

SS7 Signaling session 7

SSR SIP signaling router

TDM Time division multiplexing

UA User agent

VM Voice messaging

VoIP Voice over Internet protocol


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Crprt inqiris:

Tekelec

5200 Paramount Parkway

Morrisville, North Carolina 27560 (USA)

Phone: 888.628.5521Phone: +1.919.460.5500

FAX: +1.919.460.0877

erp, midd est nd afric inqiris:

Tekelec

Katherine House

85 The High Street

Egham, SurreyTW20 9HF

United Kingdom

Phone: +44.1784.437000

FAX: +44.1784.477121

Singpr-asi-Pcific inqiris:

Tekelec Singapore Pte Ltd

15 Hoe Chiang Road

#06-06 Tower 15

Singapore 089316Phone: +65.6796.2288

FAX: +65.6796.2299

Crin nd ltin aric inqiris:

Tekelec Caribbean & Latin America (CALA)

5200 Paramount Parkway

Morrisville, North Carolina 27560 (USA)

Phone: +1.919.460.5500FAX: +1.919.460.0877

All sales related inquiries contact: [email protected]

www.tkc.c

2009 Tekelec. All rights reserved. Printed in U.S.A. TKLC-HB-001-NA-01-2009

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