Download MM2001-Presentation - School of Computer Science

A Conference Gateway Supporting
Interoperability Between SIP and H.323
Jiann-Min Ho (Presenter)
Jia-Cheng Hu
Information Networking Institute
Peter Steenkiste
School of Computer Science
Dept. of Electrical and Computer Engineering
Carnegie Mellon University
Agenda
Overview
Target network and goal
Signaling protocols and comparison
Design
Implementation
Performance evaluation
Discussion
Related work
Conclusion
Overview Multi-party Media Conference
Media conference application drivers

Network bandwidth and endpoint capability
Signaling and media streaming protocols

Signaling protocols:


H.323 (ITU-T) vs. SIP (IETF)
Media transport protocol: RTP (RFC1889)
Target Network and Goal
Target network –


Packet switching network (e.g. IP), not PSTN
Future network infrastructure
Goal – two folds


Build a practical system allowing SIP and H.323
clients to participate in one video conferencing
session.
A set of recommendations and for developers and
standard bodies that would improve
interoperability issues.
Signal Protocols Generic H.323 Call Flow
Signal Protocols Generic SIP Call Flow
Signal Protocols Comparison of H.323 and SIP
Modularity

Synchronization of the mapping procedures during
operation
Message presentation

Translation of syntax
Mapping of an H.323 conference and a SIP
session


Map H.323 conference ID and SIP session ID
Map the H.245 capabilityDescriptor structure to SDP
syntax
Signal Protocols Comparison of H.323 and SIP(cont.)
Advertising

Conference information availability
Determination of conference media capability
Applicable solution:
 Central determination via an intermediate agent serving
as an H.323 mc
Control over membership

Generic admission control mechanisms and strategies
handling conference membership
Design – GCCG Functionality
Design - Functionality of GCCG
in SIP and H.323 perspective
On the H.323 side


Gatekeeper (GK), Multipoint Controller (MC) and
Multipoint Processor (MP) without transcoding
Independent conferencing components
On the SIP side

Proxy Server and Conferencing Server
Design – Key Design Decisions
Conference Call Messages Translation
H.323

Conference Create 

SIP
H.225 SETUP (? H.245 CapSet )
N/A (no SAP supported)


SDP message
SDP message
Conference Invite - depend on conferencing scenarios


H.225 SETUP
(? FastStart)
H.225 SETUP


INVITE (? SDP) message
+ OPTION (obtain/check SIP invitee Media Cap. - Invitable?)
INVITE (SDP) message


N/A (trigger IGMP message)
N/A (only IGMP message)
Conference Join 

H.225 SETUP
N/A
Design – Key Design Decisions
(Cont.)
Central Determination of Conference Media
Capability
Ongoing Conference Information
Conference Management: Membership
Control and Session Management
Design – Example: Conference
Invite and Join
• H.323 Client Invites SIP Client via Fast Connection Procedure
NOTE: Conference is created after the invitee’s media cap is received.
H.323 Endpoint (E1)
GCCG
SIP Client C1
ARQ
ACF
Setup (C1 {usrID@addr}, CID = N, invite,
FastStart {openLogicalChannel structures})
Option ( C1 {usrID})
Option_Reply(Media type)
Invite ( C1 {usrID}, Session Info)
SDP messages to M Bone cloud
Ringing
Alerting/Call Proceeding
Accept
Connect (GCCG H.245 TA)
No H.245 control channel…
Bye
Terminal Left Conference
Design – Example: Conference
Invite and Join (Cont.)
• A H.323 Endpoint joins an ongoing conference.
H.323 Endpoint (E2)
GCCG
H.323 Participants (E1)
ARQ
ACF
Setup (GCCG, CID = N or
session name, Join)
Alerting/Call Proceeding
Connect (GCCG H.245 TA)
terminalCapabilitySet Exchange
M aster/Slave Determination
M ultipointConference Indication
CommunicationM odeCommand
M ultipointConference Indication
CommunicationM odeCommand
Implementation
GCCG Internal Architecture
SIP
Receive
Handler
Translated Signal
FIFO Queues
SIP/SDP
M essage
Handler
Conference
Control
Logics/Functions
H.323
M essage
Handler
RAS
Signaling
Channel
Handler
Call Signaling
Routing
Handler
H.323 connection
per endpoint
H.225
Call Signal
Channel
Handler
M edia Data
Switching
SDP
Receive
Handler
SDP/SIP
Send
Handler
Internal
Conference
Control Data
H.245
Call Control
Channel
Handler
Internal Data Flow
Program Control Interaction
Active Thread
Internal Data Storage
Internal Message Queue
Implementation –
Operation and Status
Only video is available.
Simple Conference Media Mode
Determination
H.323 clients are lack of conference
information, LDAP is not supported.
Media streams (RTP) are forwarded via
GCCG; no support from media
mixing/transcoding components/gateways.
Performance Evaluation
Correctness of conferencing signaling flow
via GCCG
Testbed configuration


One GCCG Server (Linux PC) and Five PC Clients (NT)
Video Conferencing Software



MS NetMeeting version 3.01 and the MBone tools SDR v2.9 and VIC
v2.8.
Common communication mode - H.261
Network Configuration

10 Mbs shared Ethernet
Performance Evaluation (cont.)
H.323
client
H.323
client
Media Strea ms
RTP(H.261)
GCCG
Server
H.323
client
H.323
client
RTT
Measurement
H.323
client
SIP
client
SIP
client
SIP
client
SIP
client
Media Strea ms
RTP(H.261)
multicast
GCCG
Server
H.323
client
RTT
Measurement
Performance Evaluation (cont.)
Comparison of Average RTT
Average RTT(ms)
18
16
14
12
10
Scenario 1(H.323 clients)
8
Scenario 2(SIP clients)
6
1
2
3
4
Number of Participants
5
Discussion
Negotiation of Media Capabilities

Common conference media type (no transcoding GW)


H.323 – determined by MC via H.245 procedures
SIP – use a proxy server to query media capability information.
OPTION message can be applied. Standard? Draft?

Translation of message syntax between H.245 and SDP

Change of media stream codec gracefully?
Discussion (cont.)
Session Advertising

Conference information advertisement



SIP – operate with SAP (push)
H.323 – LDAP can be used (pull) if clients require this feature
Conference information mapping
Adaptation of Call Signaling Semantics

Reduce signaling overhead via H.323 FastConnect
Conference Control


H.323 – ITU-T T series, e.g. T.124, GCCP…
SIP – drafting, standards?
Discussion (cont.)
IP Multicast

Characteristic of the architecture – open conference




Authorization, authentication, encryption
Application level support – conference server (GCCG) and
clients (H.323/SIP)
IP multicast support – match application needs
Access media streaming multicast address



H.323 – determined by MC
SIP – from SAP messages
malloc
Related Work
Several active groups, e.g. aHIT! from IMTC,
ITU-T SG 16 and TIPHON, and …
H.323/SIP signaling gateway

- Columbia University
Our prototype implementation focus


Multi-party media conferencing signaling support
IP multicast efficiency
Conclusion
Completion of interoperability for H323 and
SIP in multiparty media conferencing
sessions
Recommendation for raised interoperability
issues.
Q&A