Transcript Interworking Between SIP/SDP and H.323

Interworking Between SIP/SDP and H.323
Kundan N. Singh,
Dept. of Computer Science, Columbia University
[email protected]
Agenda
•
•
•
•
•
July 20, 2000
Compare SIP/H.323
Problems in interworking
Possible solutions
Conclusion
Q/A
H.323/SIP
1
What is H.323 ?
Multimedia Communication Protocol
Terminal/
User Agent
Q931
H245
RTP
RAS
H450
Gatekeeper
MCU
(Conferencing)
H323 Box
Terminal/
User Agent
Gateway
(Bridge to another
network)
H323 Network
July 20, 2000
H.323/SIP
2
What is SIP ?
Session Initiation Protocol for Internet
Servers
UserAgent
Registrar
Redirect
Proxy
UAS/UAC
July 20, 2000
H.323/SIP
3
H.323 vs SIP
Typical UserAgent Protocol stack for Internet
Terminal Control/Devices
Q.931
H.245 RAS RTCP
TPKT
TCP
Terminal Control/Devices
Codecs
Codecs
SIP
RTP
RTCP
RTP
UDP
Transport Layer
IP and lower layers
July 20, 2000
SDP
H.323/SIP
4
SIP vs H.323
• Text based request
response
• SDP (media types and
media transport
address)
• Server roles: registrar,
proxy, redirect
• Binary ASN.1 PER
encoding
• Sub-protocols: H.245,
H.225 (Q.931, RAS,
RTP/RTCP),
H.450.x...
• H.323 Gatekeeper
Both use RTP/RTCP over UDP/IP
July 20, 2000
H.323/SIP
5
Interworking Problems
Call setup translation
H.323
Q.931 SETUP
Q.931 CONNECT
SIP
Destination address
([email protected])
200 OK
Terminal Capabilities
Terminal Capabilities
Open Logical Channel
Open Logical Channel
INVITE
Media capabilities
(audio/video)
ACK
Media transport address
(RTP/RTCP receive)
• Multi-stage dialing
• H.323v2 Fast-start is optional
July 20, 2000
H.323/SIP
6
Interworking Problems
User Registration
?
H.323
H.323 Gatekeeper
SIP
SIP registrar
H.323 terminal
SIP user agent
Alias: Henry
E164: 7040
sip:[email protected]
sip:[email protected]
• Location independent user identifier ?
• Use information from both networks
July 20, 2000
H.323/SIP
7
Interworking Problems
Media Description
SIP/SDP (dynamically choose from listed modes)
List of alternative set of algorithms.
audio G.711 Mu law, G.723.1, G.728
video H.261
H.323/H.245 (declare your exact modes)
Supports inter-media constraints
{ [G.711 Mu law, G.711 A law][H.261 video]}
{ [G.723.1] [no video] }
• Translation in both directions
• Algorithm selection by end-systems
July 20, 2000
H.323/SIP
8
Interworking Problems
Call Services
• H.323 Conferencing:
centralized signaling
control, MC (Multipoint Controller)
• Supplementary
services, like call
transfer: H.450.x
July 20, 2000
• SIP Conferencing:
centralized bridged +
decentralized
distributed
• New headers : Also,
Requested-By,
Replaces
H.323/SIP
9
Interworking Problems
Security and QoS
• H.323 uses H.235, whereas SIP uses Basic,
Digest, PGP
• Media Traffic end-to-end; QoS ?
July 20, 2000
H.323/SIP
10
What we want ?
•
•
•
•
Transparent translation
Minimum modification in SIP or H.323
Use features from both SIP and H.323
Direct RTP/RTCP traffic; end-to-end
July 20, 2000
H.323/SIP
11
User registration
Registration info to foreign network
REGISTER
[email protected]
Contact:pc1
H.323 Gatekeeper + SGW
home.com
SIP registrar server
INVITE [email protected]
pc1.office.com
3xx Moved
Contact:pc1
RRQ
[email protected]
Contact:128.59.19.200
SIP user agent
H.323 terminal
[email protected]
128.59.19.200
use SIP REGISTER and/or H.323 RRQ/RCF
July 20, 2000
H.323/SIP
12
User registration
Registration info from foreign network
LRQ/LCF
H.323 Gatekeeper
home.com
SIP registrar server + SGW
INVITE [email protected]
pc1.office.com
200 OK
RRQ
[email protected]
Contact:128.59.19.200
SIP user agent
H.323 terminal
[email protected]
128.59.19.200
use SIP OPTIONS and/or H.323 LRQ/LCF
July 20, 2000
H.323/SIP
13
User registration
Different Architectures
• SGW co-located with H.323 gatekeeper
• SGW co-located with SIP registrar/proxy server
• Independent SGW
July 20, 2000
H.323/SIP
14
Call Setup
with H.323v2 Fast Start
(Almost) One-to-one mapping between SIP and H.323 messages.
H323
SIP
Setup/FastStart
INVITE
Connect/FastStart
200 OK.
ACK
RTP/RTCP
Reverse direction is similar
July 20, 2000
H.323/SIP
15
Call Setup
without Fast Start
H.323
Q.931 SETUP
Q.931 CONNECT
SIP
Destination address
([email protected])
200 OK
Terminal Capabilities
Terminal Capabilities
Media capabilities
(audio/video)
Open Logical Channel
Open Logical Channel
INVITE
ACK
Media transport address
(RTP/RTCP receive)
Accept the call from H.323, forward to SIP after OLC ?
Not desirable.
July 20, 2000
H.323/SIP
16
Call Setup
without Fast Start, SIP to H.323
H323
SIP
Setup/Q931
Connect/Q931
INVITE
Signaling
Gateway
Capabilities/H245
Capabilities/H245.
Open Logical Channel/ H245
Acknowledgement
Media Transport
Address
200 OK.
ACK
Open Logical Channel / H245
Acknowledgement
RTP/RTCP
July 20, 2000
H.323/SIP
17
Call Setup
without Fast Start, H.323 to SIP
H323
SIP
Setup/Q931
Connect/Q931
INVITE
Signaling
Gateway
ACK
Capability Exchange
Open Logical Channel
200 OK
Media Transport
Address
Re-INVITE/SIP+SDP
Acknowledgement
Open Logical Channel
Acknowledgement
RTP/RTCP
July 20, 2000
H.323/SIP
18
Media Capability
• Modify SIP/SDP : multiple capability sets, or...
• Let the SGW choose a sub-set of capabilities for
SIP side
• Re-INVITE or change in H.323 mode or logical
channels, whenever it changes
July 20, 2000
H.323/SIP
19
Conclusion
What can be done ? What can’t ?
• Basic audio/video call
• Transparency of User registration
• Advanced calls with complex sessions
• Conferencing
• SIP centered, H.323 centered
• Other supplementary services
• ...
July 20, 2000
H.323/SIP
20
Conclusion
Status
• IETF mailing list “[email protected]”.
Finalizing requirements document
• IMTC and ETSI TIPHON
• Convergence between SIP and H.323 in newer
versions
July 20, 2000
H.323/SIP
21
Conclusion
Implementation - sip323
• Prototype (free download) system at
http://www.cs.columbia.edu/~kns10/software/gw
•Other information at
http://www.cs.columbia.edu/~kns10/research/gw
• My contact info: [email protected]
July 20, 2000
H.323/SIP
22