SIP-based Media Server Controlling Protocols

Ilkka Kiiskinen22.04.2008

Supervisor: Prof. Joerg Ott

Instructor: M.Sc. Kari Haapala

Table Of Contents• Background for the evaluative research

– Background– Research tools

• Terminology and environment– Terminology & Environment

• Underlying protocols• Media server control protocols

– Media Server Control Markup Language and Protocol (MSCML)– Media Server Markup Language (MSML)– Media Server Control Protocols (MSCP)

• Analysis and evaluation– High level protocol analysis and evaluation– Protocol analysis for purposes of a company– Alternative solutions

• Conclusion

Background for the evaluative research - what is this about?

Background• Real-time multimedia applications require media processing, such as

audio and video rendering, conference services and interactive voice response services. Current intelligent endpoint terminals can execute media processing but in some cases centralized media processing provide more efficiency.

• The devices that execute centralized media processing are called media servers. The efficiency of the media servers has boosted the demand and the interest of the media servers gaining common market acceptance to them.

• Media servers’ media processing resources are available to external servers via different kind of control channels. Currently there are none single standardized protocols for media server control but many similar protocols compete on the same field. This consumes development resources both from protocol development and service applications development.

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Background and research tools

• This thesis studies SIP- (Session Initiation Protocol) and XML-based (eXtensible Markup Language) media server control protocols on market year 2007.

• The examined protocols - Media Server Control Markup Language (MSCML), Media Server Markup Language (MSML) and Media Server Control Protocol (MSCP) - are evaluated both on common level and from Tecnomen Corporation perspective.

• Additionally some research work and evaluation of existing alternative media server control solutions have been done.

• The thesis represents the strengths and weaknesses of each protocol, and it proposes the best suitable protocol standard candidate on common level and for a specific company’s purposes.

Terminology and environment

PSTN

Terminal

Gateway

Gateway

PC

Switch

3G Cell phone

Application Server

Media Server

Laptop Tablet Computer

Media Database

SIP/H.323RTP/RTCP

SIP/H.323RTP/RTCP

SS7/ISDNTDM

SIP/H.323RTP/RTCP

Media Streaming + SignalingSIP/H.323RTP/RTCP

Media StreamingRTP/RTCP

Connection Control+ SignalingSIP/H.323

Connection control + Media Control

SIP/Media Server Control Protocol

Storage Access + MediaHTTP/FTP/NFS

Access Network

Other IMS Elements

SIPRTP/RTCP

IP-Network

IMS

CIRCUIT-SWITCHED NETWORK

(PSTN)

Media Service Network

Architecture

SIP/H.323RTP/RTCP

PACKET-SWITCHED NETWORK

(IP-NETWORK)

•Media•Media Session•Terminals•Media Server•Application Server•Media Database•Gateway•Media Control

Underlying Protocols

Underlying Protocols• SIP

– An example about SIP message (SIP INFO) with some common headers and MSCML payload:

INFO sip:ilkka@172.17.2.33 SIP/2.0Via: SIP/2.0/UDP 172.80.2.100:5060From: Ivr <sip:ivr@172.80.2.100>;tag=43To: Ilkka <sip:ilkka@172.17.2.33>;tag=9753.0207Call-ID: 984072_15401962@172.80.2.100CSeq: 25635 INFOContent-Type: application/mediaservercontrol+xmlContent-Length: 287<MediaServerControl version="1.0"> <response id="332985001" request="playcollect" code="200" text="OK" playduration="5200ms" playoffset="5200ms" digits="2543"/></MediaServerControl>

• RFC4240, “Basic Network Media Services with SIP”. (Netann; Network Announcement)

• VXML & CCXML

Media Server Control Protocols

Media Server Control Protocols

• To extend RFC4020 for advanced IVR and advanced conferencing

• Media Server Control Markup Language and Protocol (MSCML)

• Media Server Markup Language (MSML)• Media Server Control Protocol (MSCP)

Media Server Control Markup Language and Protocol (MSCML)

• Media Server Control Markup Language (MSCML) [RFC5022] is made to fill the needs that Netann misses.

• Not a self standing specification. It is always used in conjunction with Netann. Netann carries the basic SIP-network media services: basic conferencing service, announcement service and prompt and collect service. MSCML carries out the others.

• MSCML reached RFC status on November 2006, RFC4722. RFC4722 has been obsolete by RFC5022 since September 2007. [RFC5022]

• Two broad classes of MSCML functionality: advanced conferencing and IVR. There is also a small subset of fax processing features which can be seen as the third, scarce, class of functionality.

• MSCML carries out IVR and advanced conference requests and responses (only) over SIP, and VXML carries out HTTP interface for IVR requests and responses.

Media Server Control Markup Language and Protocol (MSCML)

• MSCML uses combined, fixed operands to execute the most common operations

• Poor flexibility and extensibility• Only one request, response or notification allowed per message• Uses Call Control Leg for conference management (dedicated SIP

session)• The most mature (in protocol status)• Good market acceptance

Media Server Markup Language (MSML)

• Like MSCML, MSML has capabilities to serve IVR and enhanced conference services.

• MSML complements RFC4240 (Netann)• Current draft for MSML is built from two separate internet drafts, Media

Sessions Markup Language and Media Objects Markup Language (MSML/MOML).

• MSML can be used for interactive dialogs, but it also can be used to invoke other IVR languages, such as VXML.

• MSML has an object oriented perspective for the media server system architecture. – The three classes of media objects defined by MSML: network connection,

conference and dialog

Media Server Markup Language (MSML)

• Payload transaction with SIP or preferebly with dedicated transport channel (such as TCP)

• MSML defines a concept “package” for language structure. “A package is an integrated set of one or more XML schemas that define additional features and functions via new or extended use of elements and attributes.” Defined rules to create a new, extensive package.

Dialog Speech

Dialog Group

Dialog Transform

Dialog Fax Detect

Dialog Base

Dialog Fax Send/Receive

Audit Connection

Audit Dialog

Audit Conference

Audit Stream

MSML Core

Dialog Core Audit Core Conference Core

Dialog Base

Media Server Markup Language (MSML)

• Scripted language– Flexible and easy to extend (packages)

– A bit complex just for most common and simple operations

• The most extensive feature set

• The modular basis for protocol enables also modular implementation development, and lets every implementer to decide themselves what to develop and what is important to them.

• MSML has defined support for multiple request, response or notification elements in a single control message.

• Fairly good market acceptance

• During the work of this document The Internet Engineering Steering Group (IESG) has given to the MSML document status “Dead” (24.9.2007), and IETF has focused the work to the MEDIACTRL.

Media Server Control Protocol (MSCP)

• The third and the latest developed of these SIP-based proposals for media server control interface protocol at hand.

• MSCP is (was) IETF’s internet-draft for an application server to control interactive media and conferencing functions on media server and notifications related to these functions.– MSCP has been already removed from IETF Internet-Draft database

since it has expired the maximum lifetime of unrevised documents. • The protocol messages are modeled on W3C (World Wide Web Consortium)

CCXML 1.0 elements for interactive dialog and conferencing. • MSCP can rely working with SIP messages, but the description encourages

using dedicated channel for message transportation.• Leans to VXML+CCXML• 3GPP had MSCP on their candidate lists• Flexible design• Incomplete protocol description• Overrun by MediaCtrl’s Media Server Control Protocol

Analysis and evaluation

Analysis and evaluation

• High level analysis• Protocol analysis for a specific company’s

purposes• Alternative solutions

High level analysis• The criterions (evaluative questions) for every graduation keys were

created:• Capabilities: How many different kinds of functions the protocol

supports (existing, mentioned in the protocol description, conjunctive protocols or tools are taken into account)? How the functions meet the needs? Architectural design: How solid and practical is the structure of the architecture? How complex is the architectural design?

• Protocol status: What is the status of the protocol?• Progress (in development): Is protocol development in active

progress or is it stagnant? • Extensibility: Can the protocol be extended with vendor specific

functions?• Flexibility: Is the protocol flexible? Can the protocol be modified if

needed?

High level analysis• Implementation drive: Who are driving the protocol? Are there big players

as background for the protocol? Commercial implementations and markets: Are there commercial (successful) implementations? (Do these implementations give first comer’s advantage?) What are the current/future estimations for market shares? Are there any trends on view?

• Position in IMS: Does the protocol have any role in IMS? (can be seen as market potential)

• Intellectual Property statements: Are there any restrictions from IPR?• Capacity bottlenecks: Are there any capacity limitations in the protocol

itself?• Security: Have attention been paid to the security features?

High level analysisResults (suggestive)

Protocol analysis from a specific company’s purposes

The specific criterions and explanations for every graduation keys are:

• Strategic Fit: Does the protocol fit to the company strategy and roadmap?

• Market potential: Does some protocol provide a higher market potential than others and why?

• Channel Partner Requirements: How well the protocol suits for channel partner deals? Can it be sold to partners as a solution for Media Server Control interface? (partners’ opinion)

• Former tendency and current resources: Are there ready (partial) solutions? Does the former tendency support the development of the protocol? Is there know-how and resources available? When is the expected time-to-market?

• Continuity: Does the protocol complement current product? How well it suits in existing product?

Alternative solutions

• Megaco/H.248• MRCPv2• VXML+CCXML• MediaCtrl Working Group

Conclusion

Conclusion• MSCML, MSML & MSCP: MSML and MSCP have more or less dried

out, the future for those does not seem to be very promising. MSCML has gained some foothold in the markets, but it seems not be a far-reaching solution. There may never be one standard that is universally accepted to control all media servers, however, a clear trend is emerging — the use of the web model based on an XML language and the use of SIP for session establishment.

• VXML & CCXML: VXML complemented with CCXML is the emerging call control and media server control interface. CCXML is becoming a defacto standard to be supported by media servers.

• MediaCtrl Protocol: upcoming strong candidate as universal standard

Possible future work

• The work of this study could be continued by making a market study about the IMS’ MRF current market shares, market forecasts and estimates.

• Also the implementation of a media server control protocol can be seen as a potential assignment and challenge.

• This study has also only an overview about CCXML. Since the interest of the markets towards CCXML has been raised a lot, it could be studied in more detailed.

• The progress and gained results of the MediaCtrl Working Group could also be evaluated and studied.

Thank you!

Questions?