A Unified Session Control Protocol for IPTV Services


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A Unified Session Control Protocol for IPTV Services

  1. 1. A Unified Session Control Protocol for IPTV Services Shanmugalingam Sivasothy, Gyu Myoung Lee, and Noel Crespi Wireless Networks and Multimedia Services Department Institut TELECOM SudParis 9 rue Charles Fourier, 91011, Evry, France {Shanmugalingam.Sivasothy, gm.lee, noel.crespi}@it-sudparis.eu Abstract  IPTV services are being and will continue to be a RTSP6 and SIP. One of the hurdles today to deliver the SIP main driver in the rollout of Next General Networks. In the services over corporate networks is firewall and NAT traversal. IPTV functional architecture, Service Control Functions and Opening the network other than HTTP/HTTPS 7 still is a Content Delivery Control Functions are most important question for a network administrator. In some cases, opening elements in realizing the IPTV services. SIP, RTP and RTSP the network for RTP and SIP is achieved using SIP and RTP protocols are commonly used in the IMS-based IPTV. Using many protocols in the implementation makes the system complex aware firewall or session border controller. Rather than one and proves less flexible in the integration and creation of new opening for RTSP, it is desirable to have one unified session services. Besides, SIP is a session protocol and can, with limited control protocol. In client side, having separate persistent impact on standards, extendable to carry RTSP messages. In this connectivity for RTSP, SIP and RTP is not advisable in terms paper, we propose a unified session control protocol based on SIP, of performance. Therefore, reducing the number of protocol is which can be used for control of sessions and media in IPTV a right option. At last in the context of IMS based IPTV services. Consequently, new features for services can be architecture, SIP is used to manage the session. Extending SIP developed using the proposed unified session control protocol. to manage the media control is a viable solution than For example, when a user interrupts IPTV services, deploying other protocol for media control. advertisement or recommendation of relevant video can be displayed on the screen. Furthermore, IMS provider is in the position of providing the context information and has more knowledge of the users than content providers. With unified session control protocol, Keywords  IPTV, IMS, SIP, Media Control Protocol. IMS gain more control over content delivery and become rich context provider that could allow network operators to play a 1. Introduction key role in providing IPTV services. In this paper, we propose the unified session control protocol for IPTV services, which Internet Protocol based Television services (IPTV) are can control session and media together. gaining popularity in telecom business circle specially telecom SIP is used along with UPDATE method to carry the vendors and telecom operators. This service gives high session–media states. At this moment, four defined revenue to telecom operators, in turn to telecom vendors, session-media states are defined such as started, paused, which lose revenue in the traditional voice services. In user restarted, and end. Once session is started using SIP INVITE, point of view, they are able to access high quality video easily session-media state becomes started. When user pauses the using IPTV. High penetration of broadband connectivity, media, session-media state is changed into paused by sending improvement of multimedia codecs, and deployment of UPDATE message with SIP-MEX header. UPDATE method flexible triple play service delivery architecture by the is used again to change the state from paused to restarted. operators contribute to the success of IPTV. Using SIP BYE message, session-media state is changed into The Standardization of IPTV services is being carried out end. Session layer control the media together brings a lot of by ITU-T 1 IPTV-global standard initiative (GSI) and ETSI advantages over having many different protocols. This unified TISPAN, etc. In particular architectural point of view, ETSI protocol approach is used to develop new advertisement/ TISPAN NGN release two specification adopts IMS 2 and recommendation service over IPTV services. This paper NGN3 to support IPTV services. contributes mainly the argument for using SIP for session and In order to realize the IPTV services based on IMS, IMS media control protocol. user deploys minimum four protocols such as HTTP4, RTP5, This paper is organized as follows. In Section 2, related work is discussed. Section 3 gives basic idea of IMS based IPTV architecture. The proposed unified session control 1 ITU-T:International Telecommunication Union -Telecommunication 2 IMS: IP Multimedia Subsystem 5 RTP: Real-time Transport Protocol 3 NGN-Next Generation Network 6 RTSP : Real-time Streaming Protocol 4 HTTP: Hypertext Transfer Protocol 7 HTTPS: Hypertext Transfer Protocol over Secure Socket Layer ISBN 978-89-5519-139-4 -961- Feb. 15-18, 2009 ICACT 2009
  2. 2. protocol is mentioned in the Section 4. The Section 5 is protocol. This proposed protocol supports new requirement, devoted to discuss the new added services over IPTV using which gets the details when trick function takes place, and unified session control protocol. The last section discusses used one of the possible solutions given in [3]. We will about conclusion and future works. propose relevant use case in Section 5, as an example for converged services. 2. Related Work Another Internet-Draft [4] defines the requirements for a media control protocol distinct from the session control Two different IPTV architectures are defined by TISPAN protocol for content on demand media streams. These efforts –IMS based IPTV system and IPTV subsystem. The session have influence on our unified protocol. Some requirements for and media control/delivery protocol are separated by different media control protocol are satisfied by our proposed protocol. protocols in IMS based IPTV architecture. While SIP is used In our proposal, importance of integrating the media control for general session for media control and delivery, RTP and protocol and session control protocol is presented with use RTSP are used for media delivery and control respectively. case. IMS based IPTV architecture is matured and provide more In [5], three approaches are taken into for video on demand flexibility in order to deliver converged services in services. imaginative ways and reuse many resources of NGN-IMS for 1. SIP and RTSP are in primitive stage. IPTV services [1][2]. 2. SIP for session and media setup signaling; RTSP for Combining the features of RTSP with SIP is discussed media signaling different papers [2][3][4][5]. There are some commonalties in 3. RTSP gateway (SIP to RTSP). RTSP and SIP, urgent needs of merging these two protocols in Approaches using SIP for session, media setup signaling are terms of the resource reservation is reported in [2]. presented. However, centralized control over media signaling Evaluation of SIP for use in streaming media applications using SIP is not discussed in details. In last, SDP is being are presented as Internet-Draft [3] in the context of converged defined for RTSP in [6]. In this approach SIP is used to media services. This document provides the requirement and negotiate the information of RTSP and RTP and possible solutions. One of possible solutions for SIP-only functionalities of RTSP remain same. approach is considered into our unified session control Note: SDF and SSF - Service Discovery and Selection Functions UPSF - User Profile Server Function SCF - IPTV Service Control Functions N-PVR - Network Personal Video Recorder NASS - Network Attachment Subsystem MCF & MDF - IPTV Media Control and Delivery Functions BC – Broadcast CoD - Content on Demand Figure 1. IMS based IPTV architecture (illustration from [7]) ISBN 978-89-5519-139-4 -962- Feb. 15-18, 2009 ICACT 2009
  3. 3. 3. Architectural Models plays and media control features can be mapped to the SIP as it is summarized in [3]. ITU-T has defined NGN as “A packet-based network is able 1. New SIP headers (SIP-MEX with new SIP headers in to provide telecommunication services and able to make use of INVITE/UPDATE) multiple broadband, Quality of Service (QoS)-enabled transport technologies and in which service-related functions This method is relatively simple and easy to adopt in the are independent from underlying transport related SIP environment. Necessarily, UE and SCF should technologies. It enables unfettered access for users to networks understand the SIP-MEX headers. Also controlling media and to competing service providers and/or services of their within a session is considered as a use case in this paper. choice. It supports generalized mobility which will allow consistent and ubiquitous provision of services to users.”[8] 2. New SIP bodies (new XML body in SIP INFO message). Consequently, ITU has developed the general architecture for NGN, which has two stratums: transport stratum, and This method can be used for this purpose as used SIP service control stratum. This well known this layered UPDATE. SIP INFO is used for communicating mid-session architecture provides much flexibility in service creation and signaling information along the signaling path for the session. convergence of access network. 3Generation Partnership Project (3GPP) has designed IMS 3. New SIP methods: This feature is less attractive since it from release 5, which is fulfilling the needs of service control stratum. 3GPP has adopted SIP from IETF for session needs more works and wider understanding. management in IMS. In IMS, SIP is used for user registration and messaging services also. 4. Additional extensions in existing SIP bodies (e.g.: SDP TISPAN–NGN proposes two different architectures for attribute). This idea could be used along with IPTV services: IMS based and IPTV subsystem based. Even INVITE/UPDATE headers. though each architecture has own strength and weakness, we consider IMS based IPTV architecture, which is shown in Even though, trick plays and media control features has to Figure 1. be handled by SIP, some information has to be passed back to Service eco-system on top of IMS is called Service delivery UE from SCF when some events happen such as pause. platform, which will be instrumental for delivery converge red Therefore, new header (SIP-MEX) in UPDATE method with services to an IMS user. new XML body is used in our proposed solution for tricks SPICE (Service Platform for Innovative Communication plays and media control features. This criteria is used to select Environment) [9] is an EU FP 6 project, which addresses the the right mechanisms out of four mentioned above. SIP-MEX still unsolved problem of designing, developing and putting is not standardized and is used for carrying the media event into operation efficient and innovative mobile service information. creation/execution platforms for networks beyond 3G . SIP session typically follows the cycle of many IMS users can create their services, can receive content session-media states. Session-media states are started, paused, using different modalities, context based services from SPICE restarted, and end. Restarted happens after media pauses. platform. SPICE project is aimed to enhance the service Mostly, UPDATE is used to change session media state. It delivery platform based on IMS. Therefore, our focus is based means when session is started, issuing an UPDATE command on IMS based IPTV architecture. can trigger the state from started to paused. Likewise, paused Core IMS as shown in Figure 1 is a key element to manage state can be trigged to restarted state by UPDATE command. the session. Important functional entity within Core IMS is These UPDATE will not change the session parameters S-CSCF. instead change session-media state of a session. In IMS based IPTV architecture, generally IPTV user UPDATE will contain SIP-MEX header with value: session takes place between user entity (UE) and IPTV service pause/restart. One important change is that content-type is control functions (SCF) through core IMS. The session is application/XML not SDP8. When UPDATE message is sent controlled between UE and IMS core by Gm interface. IMS from UAC9 to UAS10, it will carry new SIP header called as service control (ISC) interface is used between IMS core and SIP-MEX. The content type of the response message is XML, IPTV SCF. The session can be extended to IPTV media which is simple and flexible enough to change. In early stage control functions (MCF) via y2 interface in Figure 1. of session, UPDATE message can be sent in order to change IPTV media delivery function provides the content to a user session parameters. However, this aspect is not considered for via Xd interface. At same time, user can control the media changing the session-media state at this moment. delivery by interacting IPTV MCF via Xc interface. Main difficulty is how to identify that both ends support UPDATE message and understand session-media state. 4. Proposal for Unified Session Control Protocol According to RFC 3261, Allow header in the initial invite Unified session control protocol is used for session and media control purpose in the context of IMS. Some basic 8 SDP: Session Description Protocol solution is mentioned in favor of SIP to control the media 9 UAC:User Agent Client delivery [3]. In this unified session control protocol, trick 10 UAS: User Agent Server ISBN 978-89-5519-139-4 -963- Feb. 15-18, 2009 ICACT 2009
  4. 4. message and its response can be used to verify that both end Once SCF receive the INVITE message, SCF instruct the supports UPDATE message. Session-media state is media content delivery function to deliver the media. SCF may understandable by UAS if UAS insert SIP-MEX header into have one or two different interfaces to the media content the response of UPDATE message. delivery function. The fast forward and fast backward can be added into In Figure 2, SCF is connected to MCF using non-SIP session-media states. Parameters, which describe the fast protocol. When Pause happened in UE, UE directly send forward and fast backward, can be sent in XML via UPDATE UPDATE message to SCF. OK message is sent directly to UE message. In this paper, efforts are not devoted to discuss about with XML information. Since Figure 2 does not show full these cases. description of message flow, important message is shown in Our mechanisms mainly work within UE and SCF in the dotted line. IPTV services. When UE sends the UPDATE message with Alternatively, connectivity between SCF and MCF can be Pause details, SCF replies with information, which is going to SIP enabled. In this case, SCF can behave like B2BUA or be displayed. Information of trick functions is sent in SIP body. proxy mode, but we choose B2BUA. Because SCF needs to In reply, XML info is sent back to the UE. Based on the send some information as response to UE when pause event unified session control protocol, IPTV architecture as shown happened. In the proxy mode, MCF will generate the OK in Figure 1 will have one modification, which is removing the response and SCF cannot modify the SDP of the OK message. Xc interface between UE and IPTV media control function. This model can be used when MCF is responsible to deliver Based on the design, SCF behaves in UA mode and advertisement or information to UE. Alternative scenario, coordinates the MCF via y2 interface. Details of the interface where SCF is in B2BUA and SCF is connected to MCF via between SCF and MCF are not discussed here. Optionally, SIP interface, is clearly shown in Figure 3. SCF can perform in B2BUA11 mode between user and MCF. In this case, MCF should be SIP aware. These two options are used; because connectivity to MCF and MDF depends on content provider’s ability. SCF implements the function, which is responsible to send information (advertisement/recommendation) to the UE when Pause event arrived. Moreover, way the SCF finds the information is beyond the scope, SCF may use semantic web services and context enabler services. In the trick function, for example Pause event, UE will send the UPDATE message with SIP-MEX header, which contains of PAUSE event. In response, OK message will carry relevant information in XML format to UE. Figure 3. Sequence diagram when SCF connect to MCF through SIP protocol 5. New additional features for IPTV services with unified session control protocol Web 2.0 applications made a revolution on innovation by giving new services to increase the end user experience. One application is a YouTube, [10] which is related to IPTV VOD services. In YouTube, when a user watches a video clip, a list of relevant videos is shown in the same page. At the end of video casting, user is recommended with different videos on Figure 2. Sequence diagram when SCF connect to MCF through non-SIP screen of video display. You can see this feature as shown in protocol Figure 4. IPTV architecture is in a position to deliver high quality video, but is not supporting this kind of user In the context of on demand service, scenario can be experience. Main user case is to provide the recommendation explained as follows. User selects the corresponding the media of relevant videos or any useful information (advertisement/ content from UE, which is identified by URI. Let assume that recommendation) to a user when a user finishes watching or address of the media content is movie1@vod.ims.eu. pauses a particular video. There are many use cases, which argues that SIP should be used for session and media control. As we mentioned new 11 B2BUA –Back-to-Back User Agent services in this paper, these can be benefitted from this unified ISBN 978-89-5519-139-4 -964- Feb. 15-18, 2009 ICACT 2009
  5. 5. session control protocol. When IMS provider has knowledge of media control event, this context information can be used to REFERENCES push attentative information to screen of the UE. Our solution tries to push information to screen where already existing TV [1] Mikoczy, E., Sivchenko, D., Xu, B., and Rakocevic, V. 2007. IMS based is displaying the video. Therefore, we use same dialog IPTV services: architecture and implementation. In Proceedings of the (UPDATE/OK) to carry this push information. 3rd international Conference on Mobile Multimedia Communications (Nafpaktos, Greece, August 27 - 29, 2007). ACM International Conference Proceeding Series, vol. 329. ICST (Institute for Computer Sciences Social-Informatics and Telecommunications Engineering), ICST, Brussels, Belgium, 1-7. [2] Shiroor, R.G., "IPTV and VoD services in the context of IMS," IP Multimedia Subsystem Architecture and Applications, 2007 International Conference on , vol., no., pp.1-5, 6-8 December 2007. [3] Internet Draft, “An Evaluation of Session Initiation Protocol (SIP) for use in Streaming Media Applications,” work in progress, draft-whitehead-sip-for-streaming-media-00.txt, available on http://tools.ietf.org/html/draft-whitehead-sip-for-streaming-media-00.txt [4] Internet Draft, “Media Playback Control Protocol Requirements,” work in progress, draft-whitehead-mmusic-sip-for-streaming-media-05, http://tools.ietf.org/id/draft-whitehead-mmusic-sip-for-streaming-media- 05.txt [5] Riede, C., Al-Hezmi, A., and Magedanz, T. 2007. Session and media signaling for IPTV via IMS. In Proceedings of the 1st international Conference on Mobile Wireless Middleware, Operating Systems, and Applications (Innsbruck, Austria, February 13 - 15, 2008). ACM International Conference Proceeding Series, vol. 278. ICST (Institute for Computer Sciences Social-Informatics and Telecommunications Engineering), ICST, Brussels, Belgium, 1-6. [6] Marjou, X., Lindquist, J., RajaGopal, P.Said, M., and Ganesan, S., "Session Description Protocol (SDP) Format for Real Time Streaming Figure 4. YouTube interface recommending relevant video clips to a user Protocol (RTSP) Streams", draft-marjou-mmusic-sdp-rtsp-01, February at the end of the session. 2008. [7] ETSI TISPAN, “IPTV architecture; IPTV function supported by the IMS Alternatively, IMS provider can forward media control subsystem” TS 182.027 (2008-11) available on events to context enabler, which in turn, uses SIP push [SIP http://portal.etsi.org/docbox/tispan/Open/NGN_LATEST_DRAFTS/RE LEASE3/02070-ngn-r3v310.pdf Notify] mechanism to push information. This kind of [8] ITU-T Recommendation Y.2001, “General overview of NGN”,Dec 2004 architecture is realized in SPICE project [9]. However, in our [9] SPICE project, Available on http://www.ist-spice.org case, our solution is a light weight solution and can push the [10] Youtube website, Available on http://www.youtube.com information within a same SIP dialog. [11] RFC 2326, “Real Time Streaming Protocol (RTSP),” April 1998. [12] ITU-T IPTV-GSI, available on http://www.itu.int/ITU-T/gsi/iptv This use case can be developed using SIP for session [13] Friedrich, O.; Al-Hezmi, A.; Arbanowski, S.; Magedanz,, T., "Next management and RTSP for media signaling. When user pause Generation IPTV services for an extended IMS architecture," ISADS '07. the VOD service, client can pull information from web server Eighth International Symposium on Autonomous Decentralized Systems, according to currently watching video information. But on the 2007, vol., no., pp.429-436, 21-23 March 2007. other hand, using proposed unified session control protocol, one advantage is that both ends can send the information to each other compared to HTTP. It means that network enable pause is possible. Even if network enabled pause takes place, server can send information to client in UPDATE message. The delay in passing the information to client from server can be reduced when path for UPDATE message is optimized. 6. Conclusion and Future Work We have proposed new protocol to strongly support for session and media control protocol. SIP protocol has been extended to accommodate the media setup and media control using the UPDATE method. New headers within the UPDATE method and message body has used in the proposed unified session control protocol. Media control events are considered contextual information, based on context. The user is provided with value-added information or content recommendation, for example, similar videos, targeted advertisements or information. Realization of this proposed protocol is a challenging issue to be addressed in the future. ISBN 978-89-5519-139-4 -965- Feb. 15-18, 2009 ICACT 2009