Proposed Implementation of SIPv2

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Proposed Implementation of SIPv2

• J.Castillo, I. Ganigan, J. Perez, E. Villar, B.
  Zamora
• J. Ibabao, R. Villacorta
• Computer Networks Laboratory
• Department of Electrical Electronics
  Engineering
• University of the Philippines

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Outline

• Project Objective
• SIP Functionality and Architecture
• Related Work
• Design and Implementation
• Summary

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Project Objective

• Develop Linux-based SIPv2 servers and SIPv2
  client applications running on Linux Windows
  platforms
• Implement Registrar Server, Locator Server, Proxy
  Server and Redirect Server as described in RFC
  3261
• Develop client application with support for
  messaging, audio and video over SIP

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Session Initiation Protocol (SIP)

• Originally specified in RFC 2543 (March 1999)
• RFC 3261, new standards track released in June
  2002
• An application-layer control signaling protocol
  for creating, modifying and terminating sessions
  with one or more participants
• A component that can be used with other IETF
  protocols to build a complete multimedia
  architecture (e.g. RTP, RTSP, MEGACO, SDP)

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SIP Functionality

• Supports five facets of establishing and
  terminating multimedia communications
• User Location
• User Availability
• User Capabilities
• Session Setup
• Session Management 

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SIP Architecture

• Client-server in nature
• Main entities
• User Agent
• Proxy Server
• Redirect Server
• Registration Server
• Location Server

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Registrar and UA Behavior
SIP Registrar
SIP User Agent
SIP Request SIP Reply Non-SIP Protocol
SIP Location Service
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SIP Proxy/Redirect Servers and UA Behaviors
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Related Work

• Vovida Open Communication Application Library
  (VOCAL) http//www.vovida.org/
• open source project targeted at facilitating the
  adoption of VoIP in the marketplace
• includes a SIP based Redirect Server, Feature
  Server, Provisioning Server and Marshal Proxy

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Related Work

• RFC 2543
• First standard for SIP
• sessions include Internet multimedia
  conferences, Internet telephone calls, multimedia
  distribution
• multicast or a mesh of unicast
• use of session descriptors
• support for user mobility by proxying and
  redirecting requests to the user's current
  location
• mentioned a future charter for name lookup
• Names can be electronic mail addresses, telephone
  numbers
• Result of lookup is a list of attributes/character
  istics of the user or terminal associated with
  the name

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Related Work

• RFC 3261
• Mostly backwards compatible with RFC 2543
• 37 major and 10 minor functional changes
• Major functional changes
• SIP BNF converted to be RFC 2234 compliant
• SIP URL BNF made more general, allowing a greater
  set of characters in the user part
• Separation of CANCEL and INVITE transactions
• Separation of CANCEL and BYE transactions
• UA support for both UDP and TCP.
• Full support for IPv6 in URIs and in the Via
  header field

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Related Work

• RFC 3261
• Major functional changes (continued)
• Mandatory usage of tags as they are now the
  fundamental building blocks of dialog
  identification
• Addition of the Supported header field
• More detailed (and simpler) specification for
  handling Route and Record-Route
• Lines termination restricted to CRLF
• Disallowed multiple requests in a single UDP
  packet
• Removal of usage of absolute time in the Expires
  header field and parameter

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Related Work

• RFC 3261
• Major functional changes (continued)
• Well specified usage of Route in CANCEL and ACK
  if a request had a Route header field, its CANCEL
  or ACK for a non-2xx response to the request need
  to carry the same Route header field values.
  ACKs for 2xx responses use the Route values
  learned from the Record-Route of the 2xx
  responses
• Branch parameter of the Via header field value
  now a unique transaction identifier
• Protocol operation unaffected by usage of
  multicast

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Design and Implementation
Location Server
MySQL for database
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Design and Implementation
Registrar Server
C
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Design and Implementation

• Proxy Server
• acts on behalf of UA clients to facilitate
  session establishment
• can either be stateful or stateless
• stateless simple forwarding element
• stateful

C
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Design and Implementation

• Redirect Server
• used when the requested connection received by
  the Proxy Server is not within its network
  coverage

C
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Design and Implementation

• User Agents (Clients)

VIC
RAT
C, FOX toolkit
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Testing

• SIPNess Messenger
• http//www.ipness.com/products.htm
•  basic tool for learning how SIP sessions are
  performed
• initial testing and debugging of SIP terminals
• complete SIP session, including all the outgoing
  and incoming messages, can be viewed on the
  Message Monitor window
• includes the SDP fields

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Summary

• Project aims to implement SIP system of servers
  and UA as specified by (new) RFC 3261
• Implement using C and MySQL
• Test using SIPNess Messenger
• Target alpha version by end of March 2003