SIP-H.323 Interworking Requirements

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SIP-H.323 Interworking Requirements
draft-agrawal-sip-h323-interworking-reqs-00.txt
Hemant Agrawal - GlobeSpan Inc, Radhika R. Roy -
ATT, Vipin Palawat - Opuswave Networks Inc, Alan
Johnston - MCI WorldCom, Charles Agboh - Global
TeleSystem Group, David Wang - Nuera
Communications Inc, Kundan Singh and Henning
Schulzrinne - Columbia University
IETF-48
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Content

• Roadmap for SIP-H.323 Interworking - VG 3
• Architecture and Functionalities - VG 4
• General Interworking Requirements
• Pre-Call Requirements - VG 5
• Basic Call Requirements- VG 6
• Transport Requirements - VG 7
• State Machine Requirements - VG 8
• Service Interoperability Requirements - VG 9
• Security Requirements - VG 10
• Activities Planned for Next Phase - VG 11

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Roadmap for SIP-H.323 Interworking

• SIP-H.323 Interworking Requirement RFC
• Requirement draft (draft-agrawal-sip-h323-interwor
  king-reqs-00.txt)
• Two phases of the interworking standard
• Phase 1 Basic call establishment and termination
  RFC
• Phase 2 Optional, advanced features, and
  services RFC
• Both phases have to meet the general requirements
• Specified in the requirement document
  (draft-agrawal-sip-h323-interworking-reqs-00.txt)

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Architecture and Functionalities

• Interworking function (IWF) will allow the
  interworking between the SIP and H.323 networks
• Architecture
• Can be architected in a variety of ways
• Co-existence with H.323 gatekeeper (GK) and/or
  SIP server, or stand-alone
• Location of IWF is a matter of implementation,
  not a protocol issue
• Interworking solution shall work for a minimum
  configuration required for the mandatory features
  of both H.323 and SIP
• Functionalities
• Call sequence mapping, Address resolution,
  Terminal Capability transactions, Opening and
  closing of media channels, Mapping media
  algorithms for H.323 and SIP network, Call
  resource reservation and release, Ability to
  provide the state of a call, Call state machine,
  Mid Call signal processing, and Service
  Interoperability Logic
• No processing of media data

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General Interworking RequirementsPre-Call
Requirements

• General
• May have a table of reference for lookup to
  resolve H.323 and SIP addresses to IP addresses
• May use the capabilities of either H.323 GK or
  SIP server
• May keep the address resolution information to
  itself if H.323 GKs or SIP servers not available
• Registration with H.323 Gatekeeper
• Can register with only one GK to provide
  information about SIP side extension to the GK
• Registration with more that one GK is for further
  study
• SIP user agent (UA) may register with the GK via
  the IWF
• Creates an H.323 alias address for the SIP UA and
  binds its own transport address to the alias
  address
• Registration with SIP Server
• Can register itself with the SIP server using
  TRIP to provide information about H.323 side
  extension to the SIP server
• How an IWF can register directly with one or many
  SIP servers is for further study

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General Interworking RequirementsBasic Call
Requirements

• Shall use all mandatory features of H.323 version
  2.0 and SIP version 2.0 (RFC-2543)
• Basic call requirements
• Provide default settings and release any call
  related resources on the direction of the call
  deactivation
• Address resolution for all addressing schemes of
  H.323 and SIP
• Capability negotiation
• No assumption about the capabilities of either
  SIP UA or H.323 terminal may indicate a default
  capability default capability follows the
  mandatory capability requirements
• Shall send the best possible way all the
  capability descriptors (e.g., H.245 for H.323,
  SDP for SIP) to each other
• Support opening and closing of logical channels
  unidirectional, symmetric bi-directional, and
  asymmetric bi-directional opening of channels as
  needed
• Shall support for H.323 fast connect procedures,
  H.245 tunneling, pre-granted ARQ
• Shall support of overlapped sending

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Transport Requirements

• Shall support both reliable (e.g., TCP) and
  non-reliable (e.g., UDP) transport for delivery
  of messages
• Shall not provide priority of signaling messages
  over other messages
• Support of H.323 signaling over UDP is optional
• Network does not assure quality-of-service (QOS)
• SIP and H.323 network can be anywhere
• Media transport requirements
• RTP is used for carrying media by both H.323 and
  SIP network
• If not, a media gateway is required
• Support for large fan-out

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State Machine Requirements

• Treatment of messages
• Unexpected messages as error messages
• Messages that do not change state as
  Non-triggering or Informational messages
• Messages that are expected to change states as
  Triggering messages
• Provide guidelines that classify all possible
  messages into above three categories
• Specify actions that to be taken on the content
  of the messages in the state machine

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Service Interoperability Requirements

• Define scenarios and application priorities from
  a service providers point of view
• Resulting solution to be used in a globally
  deployable network that accommodates both SIP and
  H.323

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Security Requirements

• Enable a simple security scheme
• Accept requests only from SIP EPs, SIP servers,
  H.323 EPs, or H.323 GKs
• Reject all requests other than the SIP or H.323
  entities
• All EPs trying to use the IWF for calls or other
  purpose needs to be authorized by SIP servers or
  H.323 GKs as appropriate, if present
• Need to prevent denial of service security
  attacks
• Maintain persistent data for authorized endpoints
  for future verifications

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Activities Planned for Next Phase

• Call supplementary services like call forwarding,
  call hold, and call transfer Extensions of H.245
  and SDP for ATM and other transport trunking
  between SIP/H.323 networks registration with
  multiple GKs/SIP servers Support of early H.245
  in H.323 by the IWF Sovereignty over the IWF
• Audio and video conferencing Session change
  (re-invite, mode request)
• QOS signaling Security - authentication,
  authorization and privacy Billing
• Network management Redundancy Support for
  clearing house
• The algorithm and list of messages for finding
  out the maximum mapping of capability descriptors
  with corresponding SDP by the IWF

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