Omar A. AbouabdallaOmar A. Abouabdalla

Network Research GroupNetwork Research Group

(USM)(USM)

SIP – Functionality and Structure of the Protocol

SIP – Functionality and Structure of the Protocol

ByBy

SIP or Session Initiation Protocol is an application-level control protocol for setting up, changing and terminating multimedia sessions between participants on IP data networks.

SIP or Session Initiation Protocol is an application-level control protocol for setting up, changing and terminating multimedia sessions between participants on IP data networks.

What is SIP ?!What is SIP ?!What is SIP ?!What is SIP ?!

SIP is a text-based protocol, similar to HTTP and SMTP, for initiating interactive communication sessions between users. Such sessions include voice, video, chat, interactive games, and virtual reality.

SIP is a text-based protocol, similar to HTTP and SMTP, for initiating interactive communication sessions between users. Such sessions include voice, video, chat, interactive games, and virtual reality.

When it Starts ?!When it Starts ?!When it Starts ?!When it Starts ?!

The protocol's roots extend back to 1996.The protocol's roots extend back to 1996. SIP was first developed within the Multiparty SIP was first developed within the Multiparty

Multimedia Session Control (MMUSIC) working Multimedia Session Control (MMUSIC) working group at Internet Engineering Task Force (IETF). group at Internet Engineering Task Force (IETF).

IIn 1999 SIP was approved as an official standardn 1999 SIP was approved as an official standard.. In 1999 In 1999 RFC2543 was publishedRFC2543 was published . . Its real value has only recently been uncovered. Its real value has only recently been uncovered.

How it Works ?!How it Works ?!How it Works ?!How it Works ?!

SIP requires the use of user data gram protocol SIP requires the use of user data gram protocol (UDP), and TCP is optional.(UDP), and TCP is optional.

SIP contains its own retransmission mechanisms for SIP contains its own retransmission mechanisms for the purpose of establishing sessions.the purpose of establishing sessions.

Session Description Protocol (SDP), which is the Session Description Protocol (SDP), which is the encoded body of the SIP message contains encoded body of the SIP message contains information about what media types the parties can information about what media types the parties can and will use.and will use.

Destinations in SIP are represented with Uniform Destinations in SIP are represented with Uniform Resource Indicators (URI), which have the same Resource Indicators (URI), which have the same format as e-mail addresses. format as e-mail addresses.

SIP Advantages ?!SIP Advantages ?!SIP Advantages ?!SIP Advantages ?!

It is short, simple and flexible protocol.It is short, simple and flexible protocol. It needs only a small set of messages and responses.It needs only a small set of messages and responses. Can run over most fixed and wireless networks.Can run over most fixed and wireless networks. It uses the internet model and maps it onto telecom It uses the internet model and maps it onto telecom

world.world. It uses email-like addresses to identify users.It uses email-like addresses to identify users. SIP address to identify users rather than the devices SIP address to identify users rather than the devices

they happen to be using. they happen to be using.

How it Functions ?! How it Functions ?! How it Functions ?! How it Functions ?!

User Location:User Location: determination of the end system to be used for determination of the end system to be used for communicationcommunication..

User Availability: User Availability: determination of the willingness of the called determination of the willingness of the called party to engage in communicationsparty to engage in communications..

User Capabilities:User Capabilities: determination of the media and media determination of the media and media parameters to be usedparameters to be used..

Session Setup:Session Setup: "ringing", establishment of session parameters at "ringing", establishment of session parameters at both called and calling partboth called and calling party.y.

Session Management:Session Management: including transfer and termination of including transfer and termination of sessions, modifying session parameters.sessions, modifying session parameters.

SIP supports five facets of establishing and terminating multimedia communications: SIP supports five facets of establishing and terminating multimedia communications:

How it Functions ?! (cont’d..) How it Functions ?! (cont’d..) How it Functions ?! (cont’d..) How it Functions ?! (cont’d..)

Real-time Transport Protocol (RTP) for transporting real time Real-time Transport Protocol (RTP) for transporting real time data.data.

Real-time Streaming Protocol (RTSP) for controlling delivery of Real-time Streaming Protocol (RTSP) for controlling delivery of streaming media.streaming media.

The Media Gateway Control Protocol (MEGACO) for controlling The Media Gateway Control Protocol (MEGACO) for controlling gateways to Public Switched Telephone Network (PSTN). gateways to Public Switched Telephone Network (PSTN).

Session Description Protocol (SDP) for describing multimedia Session Description Protocol (SDP) for describing multimedia sessions.sessions.

SIP is a component that can be used with other IETF protocols to build a complete multimedia architecture. SIP is a component that can be used with other IETF protocols to build a complete multimedia architecture.

200 OK F14

BYE F13

Media Session

ACK F12

200 OK F11200 OK F11200 OK F10

200 OK F9180 Ringing F8180 Ringing F7

180 Ringing F6

100 Trying F3

100 Trying F5

INVITE F1

INVITE F2

INVITE F4

Tan’s SIP Client

Bob’s SIP Client

penang.com proxy

tokyo.com proxy

SIP MethodsSIP MethodsSIP MethodsSIP Methods

InviteInvite - Indicates that the user is invited to a - Indicates that the user is invited to a session.session.

AckAck - Used to confirm a session establishment. - Used to confirm a session establishment. ByeBye - Terminates the sessions. - Terminates the sessions. CancelCancel - Used to cancel a pending Invite. - Used to cancel a pending Invite. OptionsOptions - Used to query the server for its - Used to query the server for its

capabilities.capabilities. RegisterRegister - Used to bind a permanent address to - Used to bind a permanent address to

the current location of the user.the current location of the user.

SIP Responds CodesSIP Responds CodesSIP Responds CodesSIP Responds Codes

1## Informational Responses1## Informational Responses100 Trying100 Trying180 Ringing180 Ringing181 Call is being forwarded181 Call is being forwarded

2## Success2## Success200 OK200 OK

3## Redirection3## Redirection300 Multiple Choices300 Multiple Choices301 Moved Permanently301 Moved Permanently302 Moved Temporarily302 Moved Temporarily

SIP Responds Codes (cont’d..)SIP Responds Codes (cont’d..)SIP Responds Codes (cont’d..)SIP Responds Codes (cont’d..)

4## Client Error4## Client Error400 Bad Request400 Bad Request401 Unauthorized401 Unauthorized482 Loop Detected482 Loop Detected486 Busy Here486 Busy Here

5## Server Failure5## Server Failure500 Server Internal Error500 Server Internal Error

6## Global Failure6## Global Failure600 Busy Everywhere600 Busy Everywhere

SIP StructureSIP StructureSIP StructureSIP Structure

Syntax LayerTransport Layer

Transaction LayerClient

ComponentServer

Component

Transaction User (TU)

ConclusionConclusionConclusionConclusion

SIP is short, simple and flexible signaling SIP is short, simple and flexible signaling protocol for creating, modifying, and terminating protocol for creating, modifying, and terminating sessions with one or more participants.sessions with one or more participants.

Future work will be to bridge between SIP and Future work will be to bridge between SIP and other multimedia control protocols like RSW other multimedia control protocols like RSW control protocol. control protocol.

Thank YouThank You