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Media and ISUP Signaling Transition for IMS and Next-Gen Networks

Media and ISUP Signaling Transition for IMS and Next-Gen Networks. James Rafferty, Cantata Technology Jraff@cantata.com. Agenda. Introduction: Networks in Transition Needs for Translation Signaling Media How Does it Work Now? How will it Work in the IMS? The Way Forward Summary.

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Media and ISUP Signaling Transition for IMS and Next-Gen Networks

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  1. Media and ISUP Signaling Transition for IMS and Next-Gen Networks James Rafferty, Cantata Technology Jraff@cantata.com

  2. Agenda • Introduction: Networks in Transition • Needs for Translation • Signaling • Media • How Does it Work Now? • How will it Work in the IMS? • The Way Forward • Summary

  3. Introduction: Networks in Transition • IP has excellent momentum in both carriers and enterprises • Voice and other services will run over IP in the future • The transition is underway… • But it will take many years • SIP has won the IP standards war • But it needs to interwork with the current networks • Traditional circuit based signaling is still prevalent for both landline and wireless networks • IP Multimedia Subsystem has won mind share as a next-gen service architecture • But implementations are still at the trial stage

  4. Network Evolution for Service Delivery

  5. Needs for Translation Signaling: • SIP is likely to be the protocol of choice for next generation IP communications • It will need to interwork with other signaling methods • Circuit: • SS7 network overlays for Intelligent Network services • ISDN User Part (ISUP) for call control • TCAP for Database Services like Caller ID • ISDN PRI • Channel Associated Signaling (tonal) • IP • H.323 was rolled out starting in 1998 • Still found in many carriers and enterprises • MGCP is the gateway protocol of choice for Cable networks • H.248 is used for gateway control in the IP Multimedia Subsystem

  6. Needs for Translation (2) Media: • Next generation IP architectures envision end-to-end trancoding-free voice operations • This is the ideal / Reality is messier • Why? • Most common VoIP voice codecs: • G.711, G.729A, G.723.1 • Up and coming • iLBC • Most common Wireless codecs: • CDMA, GSM-FR, GSM-EFR, AMR • Fax • Both T.38 and G.711 IP coding are common • Result: • Need to translate media across network boundaries

  7. Needs for Translation (3) • Situation is not much better for video • H.324-3G translates media between IP and first gen 3G phones • Special gateways needed to multiplex the media for transmission to the handset • A variety of different video codecs in use • H.263 (2000), H.263++ • MPEG-4 Advanced Simple Profile • H.264 (aka MPEG-4 Advanced Video Coding) • And more are being produced all the time…

  8. How Does it Work Now? • VoIP relies strongly on a variety of network elements • Media Gateways • Translate media and typically some signaling • Signaling Gateways • Usually translate from circuit signaling to IP signaling • Session Border Controllers • May translate between IP signaling protocols • For example, H.323 to SIP • Softswitches • Provide control over media and signaling gateways in a distributed architecture • Sometimes these elements are combined • For example, media + signaling -> • Integrated Media Gateway

  9. Typical VoIP Architecture IMG 1010 Media Gateway IMG 1010 MediaGateway SIP / H.323 SIP / H.323 IP Network SS7 ISDN / CAS SS7 ISDN / CAS Class 5 Switch Class 5 Switch Media Gateway Functions: PSTN-to-IP Connection >Media >Signaling >Routing End Users End Users

  10. VoIP Using Softswitch Architecture Softswitch Softswitch SIP - T SIP - T IP Network SS7 / M3UA Signaling GW H.248 / MGCP H.248 / MGCP SS7 Class 5 Switch Media GW Media GW IP Network RTP RTP TDM / IMT SS7 Media Gateway Functions: PSTN-to-IP Connection >Media TDM / IMT Signaling GW Functions: TDM-to-IP connection >SS7 to SS7 over SIGTRAN End Users End User

  11. Voice over Broadband SIP Telco Class 5 Switch RTP IP Backbone SIP Media Gateway Functions: PSTN-to-IP Connection >Media >Signaling >Routing RTP TDM Phone IP Phone

  12. VoIP Peering Session Border Controller SIP SIP / H.323 SS 7 + TDM SIP IP Carrier 1 TDM Carrier SIP / H.323 ISDN / CAS RTP IMG 1010 Media Gateway Peering Fabric Media Gateway Functions: PSTN-to-IP Connection >Media >Signaling >Routing IP to IP Connection >Transcoding > ENUM address translation SIP IP Carrier 2 SBC Functions: IP-to-IP connection >Firewall and NAT traversal >Policy enforcement >Security >Signaling Interwork (SIP, H.323) Peering Fabric offers simpler connections among carriers

  13. What’s Next: IMS • Wireless Vendors worked to produce standards for Multimedia Services over SIP • Design Criteria: • Provide common architecture for multiple services • IP at the core • Offer access to users on existing networks • Need to interwork between IP and circuit switched at the edges • Result: IP Multimedia Subsytem (IMS) • Developed by Third Generation Partnership Project (3GPP) • Endorsed by both wireless and wireline industry groups

  14. IMS Architecture

  15. SCIM S-CSCF HSS/HLR I-CSCF BGCF P-CSCF MGCF MRFP MGW IMS for the Rest of US Application Servers Key Elements: • AS – Application Server • SCIM - Service Capability Interaction Manager • MRFC - Multimedia Resource Function Controller • MRFP - Multimedia Resource Function Processor • MRF – Media Resource Function • CSCF- Call Session Control Function • BGCF - Breakout Gateway Control Function • MGCF - Media Gateway Control Function • MGW - Media Gateway • HSS - Home Subscription Server • HLR - Home Location Register SIP MRFC CSCF RTP MRF

  16. IMS and Signaling Translation • All signaling converted from circuit to IP at the edges • Integrated Approach: • Convert SS7 ISUP, PRI, CAS directly to SIP • Follows TS 29.163 which is based on ITU-T Q.1912.5 • Distributed Approach • Signaling GW: Convert SS7 ISUP and PRI to run over IP • Use the SIGTRAN suite of adaption layers that run over SCTP • For example, ISUP runs over M3UA • Media Gateway Control Function • Terminates SS7 over IP and converts to SIP

  17. IMS and Media Translation • Ideally, media is NOT converted from end to end • For example, use AMR codec for voice over entire 3G UTMS network from end to end • Conversions needed to connect to existing networks • Media Gateways • Landline Connection - Will convert G.711 to AMR or EVRC • 2G to 3G Wireless– Will convert GSM series to AMR • Voice over Broadband to Wireless IP • May need conversions such as G.729A, iLBC, or G.723.1 to AMR or EVRC

  18. State of the Standards • SIP is a many splendored thing… • Core 3261 specification and many, many others • Hitchhiker’s Guide to SIP outlines the “Core SIP” (draft) • IMS is standardized on SIP, But: • Several different versions, each offering its own profile of SIP and other related specifications • Release 5: First real specs for IMS in 2003; introduces the architecture • Release 6: More complete IMS specs in late 2004, but still incomplete • Release 7: Just being standardized now; Rollout probably 2 years away • More complete, but some areas are very immature • For example, no standard for media control between application servers and Media Resource Functions

  19. State of the Marketplace • VoIP Rollout is not waiting for IMS • SIP has overtaken H.323 for new VoIP deployments • SIP enabled Media Gateways very popular • H.323 mainly needed to tie into legacy deployments • Distributed Gateway model • Many of the large gateways use the distributed approach • Media Gateway controlled by Softswitch • Softswitch Protocols of choice are MGCP and H.248 • Usually have separate signaling gateways to terminate SS7 and convert to IP signaling • Integrated Media Gateway Model • Incorporate both signaling and media translation in GW • Include SS7 termination and conversion to SIP or SIP-T in one box for better economics

  20. The Way Forward • IMS will continue to mature and is well regarded by Tier 1 carriers • Pressures on Landline vendors such as BT will be the early IMS implementors • Wireless vendors have less incentive to make the investment except for new applications • Voice over Cable vendors start transition to IMS as well, but currently using SIP and MGCP • Tier 2 and below vendors will continue to use SIP and only convert to IMS if obvious advantages • Peer to Peer models will also compete with the IMS Client – Server approach • Skype is the 1st big success story • SIP PTP is being standardized • Slow transition from hybrid to all-IP networks

  21. 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-02.txt • International Telecommunications Union: www.itu.int • Develops H.248 / Megaco and SS7 series of recommendations • 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 and MGCP

  22. Summary • Transition underway from Circuit to IP communications networks • SIP is the IP Communications protocol of choice • Both Signaling and Media Conversion needed today and for years to come • IMS has good mind share, but still at early stage of deployments • In the meantime, a variety of network elements will fuel the transition to IP • Both distributed and integrated models popular methods for signaling and media translation

  23. Thank You!

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