Membership and Media Management in Centralized Multimedia Conferences based on

Internet Engineering Task Force Protocol Building Blocks

Author: Ritu MittalSupervisor: Prof. Jörg Ott

Instructor: Gonzalo CamarilloOy LM Ericsson AB Finland

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Contents

• Objectives• Introduction• Conferencing frameworks• Conference control protocol• Conference control protocol proposals over IETF• Conference control protocol proposal in this

thesis• Prototype implementation• conclusion

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Objective• Theoretical Part of this thesis

• Analysis of different Conference Control Protocol proposals over Internet Engineering Task Force (IETF) Centralized Conferencing (XCON) Working Group.

• Proposing a conference control mechanism

• Practical part of this thesis

• Implementation of the Conference Server using Session Initiation Protocol (SIP) on the existing Session Border Gateway (SBC) for establishing signaling connection between the conference clients and the server itself.

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Introduction

• Session Initiation Protocol (SIP) is the most widely used telephony standard

• Multimedia conferencing using SIP is becoming popular• But offering conference control services which means that

managing members and their media in a conference session is out of the scope of SIP.

• There are some non-SIP Conference control protocol Proposals over IETF XCON WG for the conference control.

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Conferencing ModelsFully-distributed

tightly-coupled

Loosely-coupled

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Conferencing Frameworks (1)

• There are two conferencing frameworks defined by IETF• The frameworks defines the logical entities and terminology

used for conferencing

1. The SIPPING Conferencing framework2. The XCON Conferencing framework

• SIPPING uses SIP as the signaling protocol• XCON framework is independent of the signaling protocol

used e.g. Can use H.323 , SIP or PSTN• the XCON framework is compatible with SIPPING framework

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Conferencing Frameworks (2)• The central component in the conferencing framework is a

conference server called focus– A participant contact to the Focus by using a unique Conference URI e.g. Sip:

myconference@sip.com – It maintains a signaling relationship with each conference participant– Responsible for media streams in the session– Responsible for conference policies, notifications about the state changes in a

conference– It contains common conference information about signaling, members, media

streams etc. known as conference object– Common conference Information is represented by data elements and their

attributes known as components– Only the authorized participants can access and manipulate those

components– Needs a non-SIP conference control protocol to access and manipulate it.

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Conferencing Frameworks (3)

• General arrangement of different entities for a conference call

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SIP

Media

Conference Object (contains common Conference Information)

Conference server/ Focus

Media server

Media control Protocol

Conference Control Protocol

Elements and their attributes

Conference Client

Conference policy

Sip:myconference@sip.com

Networking Laboratory

Conferencing Frameworks (4)

• Conference policy: A complete set of rules for a particular conference, includes– Membership Policy (rules about participation in a conference)

– Media Policy (multiple media types e.g. Audio,video etc.)

– An participant becomes authorized if conference policy allows him to make the changes in the common conference information

– Conference policy is an integral pat of the conference object

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Conference Control Protocol (CCP)

• It defines an interface between the conferencing client and the conference server to access and manipulate common conference information.

• Provides overall control over the members and media of a conference– For example: add, delete and modify members and their media in a

conference

• Performs advaced conference control services e.g. Mute a noisy participant, change the size of video display, increase/decrease the volume of the conference session etc.

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Conference Control Protocol (2)

Conferencing Client

Conference Server / Focus

Conference Object

CPCP/CSCP/CCMP/CCCP

Or CCOMP

Conferencing Client

Conferecning System

Conference Policy =

Membership Policy + Media

Policy

Conference Control Protocol (CCP)

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Conference control Protocol Proposals over IETF XCON (1)

• Conference policy control protocol (CPCP)• Conference state change protocol (CSCP)• Centralized Conference Manipulation Protocol (CCMP)• Centralized Conference Control Protcol (CCCP)

– Every protocol has its own way to access and modify (manipulate) the common conference information represented by conference object.

– We analyse them on the basis of their syntactic vs. Semantic properties.

– CPCP and CSCP uses syntactic approach– CCMP and CCCP used semantic approach

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Semantic Vs. Syntactic Approach

Syntactic• A client performs add/delete/modify

operations on the elements and their attributes of conference information.

• The client should have an complete understanding of the format used by the server to store the information.

• Modifying too many separated elements at the same time needs more network resources e.g. Bandwidth

• Scope is wide and can be used for multiple applications.

• a client have to define the whole path to modify the small information

Semantic• a client sends pre-defined or

dedicated primitives, e.g. <adduser>, <modifymedia>, <increaseConferenceVolume> etc.

• The server can store the conference information in any format.

• The confernce server should support all the primitves used by the client

• Scope is limited to only one application

• A client can extend or define new primitives even to modify small information

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Conference control protoocol Proposal in this thesis(1)

• We proposed a Centralized Conference Object Manipulation Protocol (CCOMP) – It is not a new protocol– Have features of CCMP and CCCP– Uses conference control operations in the request

• E.g. OPTIONS, GET, CREATE, MODIFY, DELETE• Conveys to the server about the operation a client wants to perform.

– Based on their semantic properties• Used pre-defined and dedicated primitives• Primtives can be extended

– Client-server model• Client send a request towards the server• Server responds with the response code of ”Success or Failure”• this maintains transparency bewteen them

– Independent of underlying transport protocol • e.g can use HTTP or SOAP

– Uses multiple primitives inside a single request– Saves network bandwidth

– Conferencekeys: confEntity=sip:conf123@sip.com identifies directly a particular conference

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Conference control protoocol Proposal in this thesis(2)

• CCOMP Operation=CREATE

CCOMP Request:<Operation=CREAT, requestId=1>

<adduser><ConfObjID

confEntity=sip:conf123@example.com>

CCCP Response:<Code= Success, requestId=1>

Conference Client

Conference Server

Conference l Client

Conference Server

Conference BluePrints

CCOMP Request:<Operation:CREATE

requestId><adduser, modifymedia, modifyVideoDisplay....>

ConfUserID

CCOMP Response:<requestId,

code=Success><ConfObjID, ConfID>

John Conferencing System

Conference Reservation/ Conference

Object

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Practical part

Prototype Implementation

•The objective of the practical part is to implement the conference server (foucs) functionality on an existing Session Border Controller.•SBC is used to manage signaling and media streams in a Voice-over-IP network.•It supports small-scale multimedia conference calls.

Session gatewary controller (SGC)

Media Proxy (MP)

H.248 Protocol

SIP

RTP

SIP

RTP

SIP Client(Caller) SIP Client

(Callee)

SBC

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Session setup Example SIP Message:

INVITE sip:conference@131.160.36.20:5060 SIP/2.0Via: SIP/2.0/UDP 127.0.0.2:5064From: sipp <sip:sipp@127.0.0.2:5064>;tag=1To: <sip:conference@131.160.36.20:5060>Call-ID: 1-11355@127.0.0.2CSeq: 1 INVITEContact: sip:sipp@127.0.0.2:5064Max-Forwards: 70Subject: Performance TestContent-Type: application/sdpContent-Length: 134 v=0o=user1 53655765 2353687637 IN IP4 127.0.0.1s=-c=IN IP4 131.160.36.20t=0 0m=audio 30105 RTP/AVP 0a=rtpmap:0 PCMU/8000

Conference Client

Session Gateway Controller

Media Proxy

(1) INVITE

(2) 100 Trying (3) H.248 Add Request

(4) H.248 Add Reply

(5) 200 OK

(6) ACK

Media

SBC

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Conclusion• Theoreical part

– Analysis of various conference control protocol proposals over IETF XCON WG.

– Proposed semantic-based CCOMP, combination of two of existing protocol proposals i.e. CCMP and CCCP.

• Practical Part– The implemenation of SIP Conference server over existing SBC is

successfully implemented.• Future Work

– Interface between the conference server and media server which is known as media control protocol

– Implementing conference control fuctionality into SBC– One CCP for the interface between the client and conference server, and

between the conference server and the media server

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