Internet DRAFT - draft-ma-h323-sip-conf-requirement
draft-ma-h323-sip-conf-requirement
SIPPING Working Group Y. Ma
H.Ikeda
H.Deng
Internet-Draft Hitachi (China)
Expires: January 11, 2006 July 10, 2005
Requirements for the interworking between IPv4-based H.323 system and
IPv6-based SIP conference system
draft-ma-h323-sip-conf-requirement-00.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
H.323 conference system is well defined and widely deployed today.
It is important for SIP UA, both IPv4 and IPv6, to access H.323
conference system. This document defines an architecture for a SIP
UA to access H.323 conference system. The requirements for the
elements in this architecture are examined. Also the transition
scenario for IPv6 SIP UA to access IPv4 H.323 conference system is
discussed.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. General architecture . . . . . . . . . . . . . . . . . . . . . 5
4. Signaling Layer . . . . . . . . . . . . . . . . . . . . . . . 6
4.1 Alias Mapping . . . . . . . . . . . . . . . . . . . . . . 6
4.2 Message Mapping . . . . . . . . . . . . . . . . . . . . . 6
4.3 Conference Control . . . . . . . . . . . . . . . . . . . . 6
4.4 Floor control . . . . . . . . . . . . . . . . . . . . . . 7
4.5 IPv4/IPv6 transition . . . . . . . . . . . . . . . . . . . 7
5. The Media Layer . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 IPv4/IPv4 . . . . . . . . . . . . . . . . . . . . . . . . 8
5.2 IPv4/IPv6 transition . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1 Normative References . . . . . . . . . . . . . . . . . . . 11
8.2 Informative References . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . 13
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1. Introduction
H.323 conference system is well defined and widely deployed today.
SIPPING WG is also defining tightly coupled SIP conferencing
now[CONFFM][CCCONF]. It is important for the two conference system to
interoperate with each other. In addition, H.323 conference system
deployed today is IPv4 only. As for SIP, both IPv4 and IPv6 elements
have been implemented. It is necessary for IPv6 SIP system to
communicate with IPv4 H.323 conference system.
There are two scenarios for the two systems to communicate with each
other depending on the location of the conference control unit. One
is that the conference control unit locates in H.323 network, a SIP
UA joins the conference through some methods. The other is that the
conference control unit locates in SIP network. H.323 terminal joins
a SIP conference defined in [CONFFM].
This document will focus on the scenario where the conferenceing
control function locates in H.323 conference system. This document
defines an architecture for a SIP UA, both IPv4 and IPv6, to access
H.323 conference system. The requirements for the entities in this
architecture are examined.
For the two conference system to interoperate with each other the
signaling needs to be translated. Further more, for IPv6 SIP UA to
access IPv4 H.323 system media layer also needs to be manipulated.
Section 3 describe the architecture for the interoperation. Section
4 discusses the signalig layer. Section 5 disscusses the media
layer.
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2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in BCP 14, [RFC2119] and indicate requirement levels for
compliant implementations.
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3. General architecture
The requirement for SIP-H.323 interworking is defined in [RFC4123].
Common architectures involving an IWF are introduced int the domument.
For the two conference system to interoperate with each other, the
architecture is shown in Figure 1. The IWF is the interworking
unit for the two systems. The MCU is the conference control unit in
H.323 system. The IWF communicates with MCU through H.323 GK. The
SIP UA communicates with IWF through SIP proxy. With the help of IWF
a SIP UA can join an H.323 conference maintained in MCU.
The IWF is interworking function unit. It is in charge of signaling
layer interoperation.
_____ ________ ____
-->| SIP |<->| IWF |<->| |<---
/ |Proxy| | | | GK | \
| |_____| |________| |____| |
| |^ ^| | _____________
| || || \->| MCU within |
| || || |H.323 domain|
______ | || || |____________|
| |<-/ _v|____|v_ |
| | | | ______|_____
|SIP UA|<-------------->| NAT |<-------------->| media |
| | |__________| | server |
|______|<------------------------------------------>|__________|
Fig.1 Interworking architecture
The SIP UA needs to transmit media with media server. If both use
global reachable IPv4 address, the media can be transmitted directly
after the negotiation process in the call set up procedure. If the
SIP UA is IPv6 only and MCU is IPv4 only they need to communicate
through a NAT.
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4. Signaling Layer
The IWF works for signaling interoperation. In H.323 domain the IWF
registers to the GK as a GW end point. In SIP domain it is a focus
UA as defined in [CONFFM][CCCONF].
The floor control server is the H.323 MCU. The floor chairs also
reside in the H.323 domain. The SIP UA in this conference is just
common participant. Other scenarios are out of the scope of this
document.
4.1 Alias Mapping
There are different formats of alias addresses in H.323 and the
corresponding addresses in SIP.
H.323 supports different types of alias addresses. The IWF should
support all the types of alias addresses.
The IWF MUST support alias mapping. It MUST have means to map SIP
URI to H.323 alias address and vice versa.
4.2 Message Mapping
The IWF MUST map SIP messages to H.323 messages and vice versa.
4.3 Conference Control
In SIP domain the IWF behaves as a focus. A focus, as defined in
[CONFFM], maintains a SIP signaling relationship with each
participant in the conference.
The IWF SHOULD support the conference package, behave as a
notifier for that package, and indicate its support in the Allow-
Events header fields in requests and responses.
A globally routable Conference Factory URI can be allocated and
published for the IWF. When the UA calls the conference factory URI,
a new conference is created through interaction with MCU.
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When other URI is called, the call is routed to GK to find
correspondent conference.
4.4 Floor control
Floor control is well defined in H.323 system[H.323]. [H.248.19]
defines the floor control package between MC and MP. The IWF MUST
support floor control protocol in H.323.
In XCON [BFCP] is defined. The SDP for BFCP[SDPBFCP] is defined in
MMUSIC. The IWF MUST support floor control in SIP message.
The IWF MUST map H.323 floor control to BFCP in SIP message and vice
versa.
4.5 IPv4/IPv6 transition
The IPv4/IPv6 transition in signaling layer is done by the IWF. all
the signaling should be transmitted through the IWF.
The IWF should understand the format of both IPv4 and IPv6 address.
For address translation it SHOULD support NAT traversal[NAT].
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5. The Media Layer
The media layer has two cases. In the first case both SIP UA and
H.323 MCU have IPv4 addresses. In the second case the SIP UA is in
IPv6 network while the H.323 MCU is in IPv4 network. In the second
case a NAT is needed to translate media stream.
5.1 IPv4/IPv4
In this scenario the SIP UA and H.323 MCU can exchange RTP stream
directly after SDP/H.245 negotiation. The IWF MUST support SDP/H.245
mapping.
If NAT exists in the media path the UA can use STUN or other means to
traverse the NAT.
5.2 IPv4/IPv6 transition
In this scenario a NAT is necessary to translate IPv4 address to IPv6
address and vice versa.
For terminals to communicate with each other the IWF should support
MIDCOM[RFC3303]. It behaves as a MIDCOM agent. With the information
extracted from SDP/H.245 it MUST notify the NAT to enable media
transmission through NAT device.
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6. IANA Considerations
There are no IANA considerations associated with this specification.
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7. Security Considerations
As an interworking entity the IWF should be compliant to the security
requirements defined in [RFC4123].
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8. References
8.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[H.323] International Telecommunication Union, "Packet based
multimedia communication systems", Recommendation H.323,
July 2003.
[RFC4123] Schulzrinne, H., C. Agboh, "Session Initiation Protocol
(SIP)-H.323 Interworking Requirements",
RFC 4123, July 2005.
8.2 Informative References
[BFCP] Camarillo, G., "The Binary Floor Control Protocol (BFCP)",
draft-ietf-xcon-bfcp-04 (work in progress), May 2005.
[SDPBFCP] Camarillo, G., "Session Description Protocol (SDP) Format
for Binary Floor Control Protocol (BFCP) Streams",
draft-ietf-mmusic-sdp-bfcp-01 (work in progress),
May 2005.
[CCCONF] Johnston, A. and O. Levin, "Session Initiation Protocol
Call Control - Conferencing for User Agents",
draft-ietf-sipping-cc-conferencing-07 (work in progress),
June 2005.
[CONFFM] Rosenberg, J., "A Framework for Conferencing with the
Session Initiation Protocol",
draft-ietf-sipping-conferencing-framework-05 (work in
progress), May 2005.
[NAT] Boulton, C. and J. Rosenberg, "Best Current Practices for
NAT Traversal for SIP",
draft-ietf-sipping-nat-scenarios-02 (work in progress),
February 2005.
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[RFC3303] Srisuresh, P., Kuthan, J., Rosenberg, J., Molitor, A., and
A. Rayhan, "Middlebox communication architecture and
framework", RFC 3303, August 2002.
[H.248.19] International Telecommunication Union, "Gateway control
protocol: Decomposed multipoint control unit, audio, video
and data conferencing packages", Recommendation H.248.19,
March 2004.
Author's Address
Yuanchen Ma
Hitachi (China) R&D
No. 5 Dong San Huan Bei Lu Road
Chaoyang District
Beijing 100004
China
Phone: +86 10 6590 8111
Email: ycma@hitachi.cn
Hiroki Ikeda
Hitachi (China) R&D
No. 5 Dong San Huan Bei Lu Road
Chaoyang District
Beijing 100004
China
Phone: +86 10 6590 8111
Email: hikeda@hitachi.cn
Hui Deng
Hitachi (China) R&D
No. 5 Dong San Huan Bei Lu Road
Chaoyang District
Beijing 100004
China
Phone: +86 10 6590 8111
Email: hdeng@hitachi.cn
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