Kommunikatsiooniteenuste arendus IRT0080

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Kommunikatsiooniteenuste arendusIRT0080

• Loeng 8Avo Otstelekommunikatsiooni õppetool,
• TTÜ raadio- ja sidetehnika inst.avo.ots_at_ttu.ee

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SIP (Session Initiation Protocol)

• A signaling protocol for setting up multimedia
  sessions between endpoints
• Fundamental shift from PSTN infrastructure
  consists of software on standard servers
• SIP designed in line with other Internet
  protocols by the IETF
• Uses overlay control network consisting of SIP
  Proxies to route SIP messages Media path
  (RTP/UDP) decoupled from signaling
• name_at_domain addressing message syntax similar to
  HTTP

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Protocols

• Session Initiation Protocol for signaling
• Reservation Protocol for reserving network
  resources
• Real-Time protocol Transporting real-time data
  and providing QoS feedback
• Real-Time Streaming protocol for controlling
  delivery of streaming media
• Session Advertising Protocol advertising
  multimedia sessions via multicast
• Session Description Protocol to describe
  multimedia sessions

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Session Initiation Protocol

• Application layer protocol for creating,
  modifying and terminating multimedia sessions
• Supports unicast, mesh and multicast conferences,
  and combination of these modes
• Similar to HTTP, Client-Server protocol, and
  text-based
• Provides reliability without assuming anything
  about the lower layer transport protocols

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Components

• User Agents
• User Agent Client
• User Agent Server
• Network Servers
• Registration Servers
• Proxy Servers
• Stateful Proxy Server
• Stateless Proxy Servers
• Redirect Servers

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Parser

• Sip messages are sent as text (Unicode
  characters)
• The Sip message grammar is given in the augmented
  BNF-form (RFC 2543)
• Syntax tree builder (JTBGJ)
• Parser Generator (Javacc)

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Protocol Building blocks
Location Server
Registration Server
Registration Server
User Agent A
User Agent B
Proxy Server
Bs current location
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Registration

• SIP Client sends REGISTER message to the
  Registration server.
• Indicates the physical location
• REGISTER messages can be multicast
  (sip.mcast.net 224.0.1.75)
• Serves as a simple locator service.
• REGISTER sipbelltell.com SIP/2.0
• Via SIP/2.0/UDP saturn.belltell.com
• From sipwatson_at_belltell.com
• To sipwatson_at_belltel.com
• CSeq 1 REGISTER
• Call-ID 70710_at_saturn.belltell.com
• Contact sipwatson_at_globe..belltell.com3890
• Expires 7200

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Name Translation, UserLocation

• SIP Addressing by a Sip URL (user_at_hostport)
• Resolves host name through
• DNS server
• Checks if domain name refers to a host
• Mail exchange host
• User at a specific host derived through zero or
  more translations
• If called party is not at SIP server, can be
  directed or proxied (personal mobility)

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Session invitation

• Caller sends the request directly to UAS or to
  the nearest proxy server
• Proxy server uses the locator service to
  determine the next hop server
• Proxy forwards the request towards the callee
• Redirect server simply returns the alternate
  addresses
• INVITE sipwatson_at_ieee.org SIP/2.0
• Via SIP/2.0/UDP c.belltell.com
• From sipa.g.bell_at_belltell.com
• To sipwatson_at_ieee.org
• Call-ID 23534_at_c.belltell.com
• Cseq 1 INVITE

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Session Invitation (cont.)

• If there are more than one locations to be
  contacted, the proxy forks the requests to all
  the locations.
• The callees response is propagated backwards the
  servers ( uses the Via header )
• Stateful Proxy maintains the state according to
  the Call-ID. So forwards responses accordingly
• The caller sends ACK request following the
  response.

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Feature negotiation

• Allows a group of end systems to agree on the
  media to exchange and their respective parameters
  such as encodings.
• INVITE request has a listing of media types and
  associated encodings that the calling party is
  willing
• Called party responds with a subset of media
  types and encodings that it is willing to use
• Feature changes
• Subsequent INVITE request
• OPTIONS request

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VoIP Call setup SIP message flow
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Motivation
Collaborative Apps
Web Browser
SameTime
VoIP infrastructure Enhancements (conferencing,
context)
Notes Calendar/email
VoIP enabled portals
Distributed application scenarios, e.g. networked
games
Corporate VoIP/data network (VoIP trial)
(SIP-enabled) Services/ Infrastructure
Client-side SIP service
In-house conferencing service (IP/ PSTN phones)
Game servers, IM servers
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LINGID

• http//www.wifi.ee/foorum2/viewtopic.php?t1083
• http//www.packetizer.com/voip/sip/
• http//www.tech-invite.com/

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Lingid (1)

• http//www.eventhelix.com/RealtimeMantra/Congestio
  nControl/queueing_theory.htm
• http//www.tmcnet.com/voip/conference/m05/sip-work
  shop.aspx
• http//en.wikipedia.org/wiki/SIP_trunking
• http//en.wikipedia.org/wiki/Session_Initiation_Pr
  otocol
• http//en.wikipedia.org/wiki/IP_Multimedia_Subsyst
  em

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Lingid (2)

• http//www.ietf.org/rfc/rfc4740.txt?number4740
• http//www.cisco.com/en/US/products/ps6638/product
  s_data_sheet09186a00804fe332.html
• http//www1.cs.columbia.edu/kns10/talks/belllabs.
  ppt
• http//www1.cs.columbia.edu/kns10/talks/