Title: Media and ISUP Signaling Transition for IMS and Next-Gen Networks
1(No Transcript)
2Media and ISUP Signaling Transition for IMS and
Next-Gen Networks
- James Rafferty, Cantata Technology
- Jraff_at_cantata.com
3Agenda
- 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
4Introduction 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
5Network Evolution for Service Delivery
Network Traditional TDM Transition Hybrid Next-Gen IP
Architecture Centralized Integrated Design Open distributed TDM-IP Migration Open distributed Pure IP (IMS)
Signaling/Functions SS7, ISDN, CAS SS7-SIP ISDN-SIP CAS-SIP SIP-SIP H.323-SIP
Media/Functions TDM TDMcircuit to circuit TDM - IP conversion circuit to packet IP - IP packet to packet
Applications TDM enhanced services Discrete applications IP-based transport SS7 services over IP IP services over TDM IP-enable/extend TDM services Multimedia services on common service platform (IMS) Blended SIP services
6Needs 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 -
7Needs 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
8Needs 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
9How 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 -gt
- Integrated Media Gateway
10Typical VoIP Architecture
IMG 1010 Media Gateway
IMG 1010 Media Gateway
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
gtMedia gtSignaling gtRouting
End Users
End Users
11VoIP Using Softswitch Architecture
Softswitch
SIP - T
Softswitch
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
gtMedia
TDM / IMT
Signaling GW Functions TDM-to-IP connection
gtSS7 to SS7 over SIGTRAN
End Users
End User
12Voice over Broadband
SIP
Telco Class 5 Switch
RTP
IP Backbone
SIP
Media Gateway Functions PSTN-to-IP Connection
gtMedia gtSignaling gtRouting
RTP
TDM Phone
IP Phone
13VoIP Peering
Session Border
Controller
SIP
SIP / H.323
SS
7
TDM
IP Carrier 1
SIP
TDM Carrier
SIP / H.323
ISDN / CAS
RTP
IMG 1010 Media Gateway
Peering Fabric
Media Gateway Functions PSTN-to-IP Connection
gtMedia gtSignaling gtRouting IP to
IP Connection gtTranscoding gt ENUM address
translation
SIP
IP Carrier 2
SBC Functions IP-to-IP connection gtFirewall
and NAT traversal gtPolicy enforcement
gtSecurity gtSignaling Interwork (SIP, H.323)
Peering Fabric offers simpler connections among
carriers
14Whats 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
15IMS Architecture
16IMS 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
17IMS 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
18IMS 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
19State of the Standards
- SIP is a many splendored thing
- Core 3261 specification and many, many others
- Hitchhikers 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
20State 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
21The 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
22Resources
- Internet Engineering Task Force www.ietf.org
- Provides RFCs for SIP, RTP and some aspects of
SS7 / IP interworking - Hitchhikers 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
23Summary
- 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
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