Wisdom of Helios

Basics of Session Initiation Protocol (SIP) (part-1)

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It is a big topic . So I decided to publish it as a series. The intended  viewers are the beginners only who want to wet their feet with SIP, VoIP and IMS(Internet Multimedia SubSystem) based application development. So , Lets go ———

What is SIP and where it is ?

SIP (Session Initiation Protocol) is a signaling protocol used to create, manage and terminate sessions in an IP based network. A session could be a simple two-way telephone call or it could be a collaborative multi-media conference session.

It is an application-layer control protocol.

SIP sessions involve one or more participants and can use unicast or multicast communication. Borrowing from ubiquitous Internet protocols, such as HTTP and SMTP, SIP is text-encoded and highly extensible. SIP may be extended to accommodate features and services such as call control services, mobility, interoperability with existing telephony systems, and more.

Can and Can’t by SIP

The job of SIP is limited to only the setup and control of sessions. The details of the data exchange within a session e.g. the encoding or codec related to an audio/video media is not controlled by SIP and is taken care of by other protocols.

There are mainly 4 types of functions that a SIP performs –

  1. Establishment of user location (i.e. translating from a user’s name to their current network address).
  2. Negotiating the provided features among participants in a session.
  3. Call management – for example adding, dropping, or transferring participants.
  4. Changing the features of a session while in progress.

SIP is not a resource reservation protocol and it has nothing to do with quality of service (QoS).

SIP can work in a framework with other protocols to make sure these roles are played out – but SIP does not do them.

SIP can function with SOAP, HTTP, XML, VXML , WSDL, UDDI, SDP and others. Everyone has a role to play!

Other posts related to SIP –

Basics of Session Initiation Protocol  (part-2)

Basics of Session Initiation Protocol  (part-3)

Basics of Session Initiation Protocol  (part-4)

Basics of Session Initiation Protocol  (part-5)

Author: Munir

I'm good for nothing

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