Transcript 投影片 1
RFC-4123
SIP-H.323 Interworking Requirements
Speaker: Yan-Shiang Wang
Adviser: Quincy Wu
Date: 2005/12/22
H.323 Introduction
Terminal
Gateway
Translation services between the h.323 and others
Gatekeeper
Endpoint that offers real-time communications with
other h.323 endpoint
Controller
MCU (Multipoint Control Unit)
Endpoint that manages multipoint conferences
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H.323 Zone
Terminal
Gateway
PSTN
Terminal
Gatekeeper
MCU
Gateway
SIP
Terminal
Terminal
Router
H.323
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H.323 Protocol
H.225.0
RAS: Registration, Admission, Status
Q.931: ISDN Layer 3 signaling protocol
Between endpoints and gatekeepers
Between endpoints
H.245
Establish and control media streams
Between two or more endpoints
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H.323 Protocol Stack
Audio/Video
Application
Audio/Video
Codecs
Terminal/Application Control
RTCP
RTP
H.225.0
RAS
Signaling
UDP
H.225.0
Call (Q.931)
Signaling
H.245
Control
Signaling
TCP
Network Layer
Data Link Layer
Physical Layer
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H.323 Protocol (cont.)
Gatekeeper
Q.931
udp or tcp port 1720
Audio codec
Discovery: udp port 1718
RAS: udp port 1719
G.711, G.722, G.723, G.728, G.729
Video codec
H.261, H.263
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RAS Signaling - Discovery
Terminal
GRQ
Gatekeeper
GK discovery
multicast address
Gatekeeper
GRQ
GRQ
GRJ
GCF
GRQ: Gatekeeper Request
GRJ: Gatekeeper Reject
GCF: Gatekeeper Confirm
Terminal sends just one GRQ to the Gatekeeper discovery multicast address.
Therefore, the Terminal will now proceed to register with which Gatekeeper.
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RAS Signaling - Registration
Terminal
Gatekeeper
RRQ
RCF
／／
／／
URQ
UCF
RRQ: Registration Request
URQ: Unregistration Request
RCF: Registration Confirm
UCF: Unregistration Confirm
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RAS Signaling - Admission
Terminal
Gatekeeper
Terminal
ARQ
ACF
Setup
ARQ
ACF
／／
／／
／／
DRQ
DRQ
DCF
DCF
ARQ: Admission Request ACF: Admission Confirm
DRQ: Disengage Request DCF: Disengage Confirm
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Q.931 Signaling
Terminal
Terminal
Setup
Call Proceeding
Alerting
Connect
H.245 Session Establishment
Media Exchange
H.245 Session Release
Release Complete
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Direct Endpoint Call
Gatekeeper
Terminal
Terminal
Gatekeeper
ARQ
ACF
Setup
Call Proceeding
ARQ
ACF
Alerting
Connect
H.245 Session Establishment
Media Exchange
H.245 Session Release
Release Complete
DRQ
DCF
DRQ
DCF
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H.245 Signaling
TCS: Terminal Capability Set
MSD: Master Salve Determination
TCSA: TCS Ack
MSDA: MSD Ack
OLC: Open Logical Channel
OLCA: OLC Ack
OLCC: OLC Confirm
ESC: End Session Command
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H.245 Procedure
Terminal
Terminal
TCS MSD
TCS MSD
TCSA MSDA
TCSA MSDA
OLC
Both Terminal send
information signalling
at the same time, they
don’t need to wait
Ack signalling.
OLC
OLCA
OLCA
OLCC
RTP
RTCP
ESC
ESC
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H.245 Procedure - Fast Connect
Terminal
Terminal
Setup (faststart [logical channel info])
Call Proceeding
Alerting
Connect (faststart [logical channel info])
Media Exchange
Release Complete
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H.323 detailed header info
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H.225 - Q.931 header
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H.245 - Master Slave Determination
Terminal Type Value
Status Determination Number
General terminal = 50
Gateway = 60
MCU = 190
MCU (currently managing a conference) = 240
Random
Largest one is master
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H.245 - MSD (cont.)
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H.245 - OLC, OLCA, OLCR
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SIP-H.323 Interworking
IWF (Interworking Function)
interworking between H.323 and SIP
MSF (Media-Switching Fabric)
optional entity within the IWF
switches media such as voice, video, or
fax from one network association to
another
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SIP-H.323 IWF
H.323
Endpoint
H.323
Gatekeeper
H.323
MCU
H.323
Terminal
SIP
User
Agent
SIP
User Agent
SIP
Server
MCF
SIP-H.323 IWF
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SIP-H.323 IWF (cont.)
May be integrated into an H.323 GK or SIP
server
Simply forwards media packets without
modification
Should not process media
MSF - Convert media from one encoding or
format to another
Out of scope for SIP-H.323 protocol translation
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General Interworking Requirements
Opening of logical channels
Should support the seamless exchange
Should support open media channels
IWF H.323 features
The channel can be opened at the MSF of the IWF
When endpoints can’t open media channels themself
Should support fast connect
Should support pre-granted ARQ (IWF in GK)
Overlapped sending
Follow RFC3578 (from H.323)
Q.931 (from SIP)
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Overlap Signalling
Modern switches use en-bloc signalling
Some parts of the PSTN still use overlap
signalling
Sending only some digits of the callee's
number in the first signalling message
Further digits are sent in subsequent
signalling messages
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Interworking Analysis
simple call setup
mapping addresses
finding a subset of capabilities described by
H.245 and SDP
conferencing and call services
security and authentication
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Register (IWF colocated with SIP server)
H.323 Terminal
Gatekeeper
IWF/GW
SIP UA
RRQ
RCF
RRQ
RCF
REGISTER
RRQ
RCF
200 OK
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RRQ (IWF colocated with H.323 GK)
H.323 Terminal
IWF/GW
SIP Server
SIP UA
RRQ
REGISTER
200 OK
RCF
REGISTER
200 OK
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Invite (IWF colocated with SIP server)
H.323 Terminal
Gatekeeper
IWF/GW
SIP UA
INVITE
100 Trying
ARQ
ACF
Setup
Call Proceeding
ARQ
ACF
Alerting
Connect
H.245
180 Ringing
Signaling
200 OK
ACK
RTP RTCP
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Setup (IWF colocated with H.323 GK)
H.323 Terminal
IWF/GW
SIP Server
SIP UA
ARQ
ACF
Setup
Call Proceeding
H.245
INVITE
INVITE
100 Trying
180 Ringing
180 Ringing
Alerting
200 OK
200 OK
Connect
negotiate between 200 OK and ACK
Signaling
ACK
RTP RTCP
ACK
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Call from SIP to H.323
H.323 Terminal
IWF/GW
SIP UA
INVITE
Setup
Connect (no faststart)
TCS (g711Ulaw)
TCSAck
TCS (g711Alaw & g711Ulaw)
TCSAck
200 OK
OLC (g711Ulaw)
c=IN IP4 1.2.3.4
OLCAck(1.2.3.4:5000)
m=audio 5000 RTP/AVP 0
ACK
OLC (g711Ulaw)
OLCAck(5.6.7.8:9000)
RTP RTCP
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Call from SIP to H.323 (with faststart)
H.323 Terminal
IWF/GW
Setup
faststart={g711Ulaw,Tx},
{g711Ulaw,Rx,5.6.7.8:9000}
Connect
faststart=
{g711Ulaw,Tx,1.2.3.4:5000}
{g711Ulaw,Rx}
SIP UA
INVITE
To:[email protected]
c=IN IP4 5.6.7.8
m=audio 9000 RTP/AVP 0
200 OK
c=IN IP4 1.2.3.4
m=audio 5000 RTP/AVP 0
RTP RTCP
ACK
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Call from H.323 to SIP
H.323 Terminal
IWF/GW
Setup (no faststart)
Connect
TCS (g711Alaw)
SIP UA
INVITE
180 Ringing
200 OK
TCSAck
TCS (g711Alaw & g711Ulaw)
TCSAck
ACK with updated SDP
OLC (g711Alaw)
c=IN IP4 1.2.3.4
OLCAck(1.2.3.4:5000)
m=audio 5000 RTP/AVP 8
OLC (g711Alaw)
OLCAck(5.6.7.8:9000)
RTP RTCP
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Call from H.323 to SIP (with faststart)
H.323 Terminal
IWF/GW
SIP UA
Setup
destination:[email protected] INVITE
To:[email protected]
faststart={g711Ulaw,Tx},
c=IN IP4 1.2.3.4
{g711Ulaw,Rx,1.2.3.4:5000}
m=audio 5000 RTP/AVP 0
Connect
faststart=
{g711Ulaw,Tx,5.6.7.8:9000}
{g711Ulaw,Rx}
200 OK
c=IN IP4 5.6.7.8
m=audio 9000 RTP/AVP 0
RTP RTCP
ACK
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Mapping Addresses
SIP address format
SIP-Address
name-addr
addr-spec
SIP-URL
= (name-addr j addr-spec)
= [display-name] ”<” addr-spec ”>”
= SIP-URL
= ”sip:” [ userinfo ”@” ] hostport url-parameters
[headers]
userinfo
= user [ ”:” password ]
hostport
= host [ ”:” port ]
host
= hostname j IPv4address
url-parameters = *(”;” url-parameter)
url-parameter = user-param j . . .
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Mapping Addresses (cont.)
H323 address format
{
e164
h323-ID
url-ID
transport-ID
email-ID
partyNumber
IA5String (SIZE(1..128)) (FROM("0123456789\#*,")),
BMPString (SIZE (1..256)), ...,
IA5String ( SIZE(1 .. 512)),-- URL Style address
TransportAddress, -- IPv4, IPv6, IPX etc.,...
IA5String (SIZE(1..512)),
PartyNumber
}
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SIP to H323
h323-ID
e164
exceeds 512 characters -> 414 (Address Too Long)
email-ID
“+”, “-” are removed
“p” -> “,”
url-ID
SIP-Address -> addr-spec
exceeds 256 characters -> 414 (Address Too Long)
exceeds 512 characters -> 414 (Address Too Long)
transport-ID
If host is indicated as a dotted quad
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SIP to H323 - examples
SIP - “sip:[email protected]” is converted to an
H.323 - { h323-ID=”sip:[email protected]”,
url-ID=”sip:[email protected]”, email-ID=“[email protected]” }
SIP - “sip:+1-212-555-1212:[email protected]; user=phone”
H.323 – { e164=”12125551212”,
h323-ID=”sip:+1-212-555-1212:[email protected]”,
url-ID=”sip:+1-212-555-1212:[email protected]”,
email-ID=“+1-212-555-1212:[email protected]” }
SIP - ”sip:[email protected]”
H.323 - { h323-ID=”sip:[email protected]”,
url-ID=”sip:[email protected]”, tranport-ID= IPAddress
10.1.2.3:1720, email-ID=“[email protected]” }
SIP - “A. Bell <sip:[email protected]>”
H.323 - { h323-ID=”A.Bell <sip:[email protected]>”, urlID=”sip:[email protected]”, email-ID=“A. Bell
<[email protected]>” }
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Mapping Addresses - H323 to SIP
If a url-ID is present and it is a SIP-URL
If an h323-ID is present and it can be parsed as a
valid SIP-Address, it is used
If the transport-ID is present and it does not identify
the IWF, then it forms the hostport portion of the SIP
URL and the user portion is constructed using
h323-ID or e164
If the email-ID is present, then it is used in the SIPURI
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Security Considerations
Signaling security for H.323 is described in
H.235
The IWF terminates not only the signaling
protocols but also the security in each
domain
Users at endpoints have to trust the IWF
The IWF must not indicate the identity of a
user on one side without first performing
authentication
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Reference
SIP-H.323 Signaling Gateway
Interworking Between SIP/SDP and H.323
http://www.cs.columbia.edu/~kns10/publication/draftsingh-sip-h323-01.pdf
Mapping of ISUP Overlap Signalling to SIP
http://www1.cs.columbia.edu/~kns10/research/gw/
http://www.ietf.org/rfc/rfc3578.txt
Carrier Grade Voice Over IP
Chapter 4, 5
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