SIP & SS7 James Rafferty, Cantata Technology September 10-12, 2007 Los Angeles Convention Center Los...

SIP & SS7

James Rafferty, Cantata Technology

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September 10-12, 2007 • Los Angeles Convention Center • Los Angeles, California

www.ITEXPO.com

Agenda

• Overview• SS7 + SIP in the Converged Network• SIP and SS7

– Applicable Standards– Use Cases– Challenges– What’s Ahead?

• Resources • Summary

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Overview

• SIP (Session Initiation Protocol) has won the IP Standards Wars

• SIP is an important part of the current and emerging IP Networks

– Most new deployments use SIP– SIP is the key protocol for the IP Multimedia Subsystem

(IMS)

• SS7 is the dominant signaling protocol used on Landline and Wireless networks

– It has been particularly successful for 2nd generation wireless networks

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SS7 + SIP in Converged Network

• SS7 will typically be found on the edge of the converged network

– ISUP (ISDN User Part) used for Call Control– TCAP (Transaction Capabilities Application Part) used

for various database lookups such as Local Number Portability (LNP) and Caller Name Lookup (CNAM)

• SIP used for backhaul of signaling or in the core between gateways

• SS7 can either be converted to SIP or transported via SIP-T

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SIP and SS7 - Applicable Standards

• Key SS7 Standards are from ITU, ETSI and ANSI– Country specific variants are very common; usually based on ITU

or ANSI

• Latest SIP Standard is RFC 3261– Many additional RFCs which document additional methods

• Several standards for SIP – SS7 interworking– IETF RFC 3372 – SIP-T

• Transfer ISUP elements via SIP with MIME body parts

– IETF RFC 3398: SIP – SS7 Mapping• Map ISUP parameters to SIP headers (where available)

– ITU-T Q.1912.5: More extensive SIP-SS7 Mapping with “SIP-I” • SIP-I extends beyond SIP-T ; includes more SS7 fields

– 3GPP TS 29.163: Similar to Q.1912.5• This is part of the IMS suite of standards

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Use Case: SS7 to SIP Conversion

Signal Transfer

Point

IPNetwork

PLMNSS7ISUP

SIP

IPPhone

SIP CellPhone

SS7ISUP

SS7ISUP

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Use Case: SS7 Bridging via SIP-T

Signal Transfer

Point

IPNetwork

PLMN/RAN

CellPhone

CellPhone

SS7ISUP

RAN

Protocols

SIP - T

PLMN/RAN

SS7ISUP

SS7ISUP

SS7ISUP

Signal Transfer

Point

RAN

Protocols

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Use Case: Privacy of Identity

Signal Transfer

Point

IPNetwork

PLMNSS7ISUP

SIP

IPPhone

SIP CellPhone

SS7ISUP

SS7ISUP

CLIP/CLIR service on Privacy of

Identity

Enforce CLIP/CLIR setting

onSIP Identity Headers

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Challenges

• Tremendous amount of SS7 based infrastructure in place

– Transition strategies for using SS7 and SIP together are critical to manage capital expenditures

• SS7 variants require switches and gateways which support the variants

• Non-standard uses of SIP are common and hard to eliminate once in the network

• Interop between equipment from different vendors is a “way of life” for the converged network

– Best of Breed Enabling Technology Components– Creates opportunities for System Integrators

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What’s Ahead?

• Lots of momentum behind IMS, which uses both SIP and SS7

– More formal model for SIP use at core– SS7 used at the edges and converted to SIP or SIP-I

IMS Architecture Example• Many operators not waiting for IMS

– Wireline vendors making extensive use of SIP “as is” – SS7 network in place and working; easier to add SIP for

backhaul or new services

• SS7 is well entrenched for services and will remain in place for years to come

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IMS Architecture

P-CSCF

S-CSCFMGCFHSS

Cx

IP Multimedia Networks

IM-MGW

CS Network

Mc

Mb

Mg

Mm

MRFP

Mr

Mb

Legacy mobile signalling Networks

I-CSCF

Mw

Mw

Gm

BGCFMjMi

BGCF

Mk Mk

C, D, Gc, Gr

UE

Mb

Mb

Mb

MRFC

SLFDx

Mp

CS

CS

IMS Subsystem

Cx

Mm

AS

ISCSh

Ut

Mb

Dx

3GPP TS 23.228 V7.2.0 (2005-12)

SS7 signaling converted at edge

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Resources

• Internet Engineering Task Force: www.ietf.org– Provides RFCs for SIP, RTP and some aspects of SS7 / IP

interworking– Hitchhiker’s Guide to SIP:

• http://www.ietf.org/internet-drafts/draft-ietf-sip-hitchhikers-guide-03.txt

• International Telecommunications Union: www.itu.int– Develops SS7 series of recommendations and NGN

• Third Generation Partnership Program (3GPP): www.3GPP.org

– Develops IP Multimedia Subsystem and related standards

• Cablelabs: www.cablelabs.org– Develops standards for Cable use of IMS

• Article: Integration of SIP and SS7 for Voice over IP– http://www.tmcnet.com/sip/0307/

feature_articles_integration_of_sip_ss7_for_voip.htm

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Summary

• SS7 remains the dominant signaling protocol in today’s network

• SIP is the key next generation VoIP Protocol• Integration of SS7 and SIP critical to leverage

existing operator investments• Several strategies possible for transition to more IP

centric infrastructure• Many vendors using SIP to build new services on

their existing SS7 network• IMS is coming, but not the only way forward for

operators making IP investments

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Thank You!

SIP & SS7 James Rafferty, Cantata Technology September 10-12, 2007 Los Angeles Convention Center Los...

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