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Understanding SIP: The Foundation of Modern Communication

This chapter explores the Session Initiation Protocol (SIP), a vital protocol for establishing, managing, and terminating voice, video, and messaging sessions over IP networks. It addresses how to locate users, manage device availability, and ensure secure communication across different platforms. Learn about the functionalities of SIP, its entities like User Agents and Proxy Servers, and how it interacts with existing telecommunication systems. We also delve into SIP's extensions for additional capabilities and integration with instant messaging and presence, setting the stage for seamless multimedia communications.

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Understanding SIP: The Foundation of Modern Communication

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Presentation Transcript

  1. Chapter 5 SIP Session Initiation Protocol

  2. How do we communicate? • Telephone (home, work, & cell phone) • Email • Text messaging • Data sharing (PowerPoint, applications, white board, desktop, etc.) • Audio/video • File transfer • Ink- tablet PC

  3. Questions? • …but how do we know where to find the person we want to communicate with • ...and given the availability of my resources, which of the persons devices do I want to communicate with • ..and what is the address of that device • ..and how does the person control his active/inactive devices • ..and how do we authenticate people • ..and how do we bridge this between organizations

  4. SIP Session Initiation Protocol • An emerging signaling protocol for: • Initiating, • Managing, and • Terminating messaging, voice, and video sessions • Internet Engineering Task Force (IETF) • Developed by the SIP Working Group • Published as IETF RFC 3261 • Connectivity using IP • May be extended for services such as: • call control services, • mobility, • interoperability with telephony systems, and more

  5. SIP and its Extensions • Presence • The willingness and ability of a user and their devices to communicate with other users on the network • SIP for Instant Messaging and Presence Leveraging Extensions (SIMPLE) • Authentication • Office integration

  6. SIP Functionality • SIP provides the following functionality: – User location (not geographical location) – User availability – User capabilities – Session set-up – Session management • SIP does not provide services – But it enables the system to provide services – It has been demonstrated that it is easy to provide services with SIP

  7. SIP Entities • User Agent – Initiates or Responds to SIP Transactions • User Agent Client (UAC) – Initiates SIP requests and accepts SIP responses • User Agent Server (UAS) – Accepts SIP requests and sends back SIP responses • Redirect Server – a UAS that generates 300 class SIP responses to requests it receives. Directs the UAC to contact an alternate set of URIs. • Proxy Server – An intermediate entity responsible for forwarding SIP requests to a target UAS or another proxy on behalf of the UAC. • Registrar – A UAS that accepts SIP REGISTER requests and updates the information from the request message into a location database.

  8. SIP Addressing • SIP uses Uniform Resource Identifiers (URIs). At least, SIP URIs and SIPS URIs are supported, although others (such as TEL URL) are commonly supported. – sip:Gonzalo.Camarillo@ericsson.com – sips:Gonzalo.Camarillo@ericsson.com – tel:+358-9-299-3371 – sip:proxy.atlanta.com:5060 – sip:another-proxy.biloxi.com;transport=UDP • SIP and SIPS URIs must include a host name, and may include username, may include port numbers, may include parameters • Address space is unlimited • Non SIP/TEL URIs are also valid under certain circumstances: HTTP, IM, PRES, MAILTO…

  9. SIP Session Establishment and Call Termination

  10. Call Redirection Using a Redirect Server

  11. Call Proxy Scenario

  12. Forking Proxy Example

  13. SIP Request Example

  14. SIP Response example

  15. Session Description Protocol • SDP is the protocol used to describe multimedia session announcement, multimedia session invitation and other forms of multimedia session initiation. • A multimedia session is defined, for these purposes, as a set of media streams that exist for a duration of time. • RFP 2327

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