Research On Multicast Technology For Large-scale Streaming Media Transmission

With the rapid development of Triple Play industries, more and more streamingmedia applications such as IPTV, Video-On-Demand and webcast, etc., arecontinuously emerging. These applications have immensely large users scale, and arevery suitable for point-to-multipoint transmission mode. Multicast is a technique used tofacilitate these types of one-to-many data delivery, by transmitting the same data fromone source to a potentially large number of destinations. So multicast can efficientlysave network resource and reduce the bandwidth stress of Internet. However, with thecontinued growth of streaming media applications, multicast confronts with adaptability,scalability and controllability challenges. Therefore, research on multicast transmissiontechnology is great significance for large-scale streaming media applications, and it hasbeen widely recognized by both global academia and industry today that how to designefficient multicast transmission technology is one of the hot research topics.In this thesis, we study some key problems of large-scale streaming mediamulticast transmission technologies, and argue the recent proposals of multicast routingprotocols, algorithms and architectures. We start our research from the proposedLabelcast based Media Transport Architecture, and then we focus on the research onneighbor gradient based multicast routing technology, a Bloom filter-based scalablemulticast forwarding engine and a service lever based edge-to-edge dynamic multicastflow control technology. We also design and implement a Labelcast switch nodeprototype, and deploy a Labelcast streaming media prototype system to validate ourwork.The major contributions of our work are as following:1. A Labelcast-based Media Transport Architecture (LMTA), which is verysuitable for large-scale streaming media transmission, is proposed. The IP accessnetwork and backbone network is isolated in LMTA. And the Backbone network isselected as Labelcast network or classical IP core network according to the flowcharacteristics. The main equipments in LMTA include: Local Media Center (LMC),Labelcast Switch Node(LSN), Core Router(CR), Client and Content Server. LMC is theimportant controlling and forwarding point between IP access network and backbonenetwork, and it has the integrated functions of Label Controller, Group Manager andEdge Router. Meanwhile, LMTA makes use of Labelcast Transport Protocol(LTP) todelivery data with label switching. LMTA could only adopt different backbone networkfor diverse flow types, but also has the adaptability and scalability in advance comparedwith other multicast architectures.2. Aiming at the adaptability problem of multicast routing in Labelcast networkand classical IP core network, we present a Policy-enabled Multicast Service Model(PMSM), which is divided into three planes: Policy Manage Plane, RoutingControl Plane and Data Forwarding Plane. In PMSM, policies can be embedded flexiblyinto this multicast service. Based on this model, the neighbor gradient definition andforwarding rule is defined, which is calculated based on the weighted sum of attributessuch as residual link capacity, normalized hop count, etc. Then two distributed multicastrouting algorithms which are neighbor Gradient-based Multicast Routing for Staticmulticast membership (GMR-S) and neighbor Gradient-based Multicast Routing forDynamic multicast membership (GMR-D), are proposed. Discovery message andfeedback message are used for discovering multicast routing path when establishing themulticast tree based on the neighbor gradient. GMR-S is suitable for static membershipsituation, while GMR-D can be used for the dynamic membership network environment.Experimental results demonstrate the effectiveness and efficiency of our proposedmethods.3. Aiming at the scalability problem of multicast routing in classical IP corenetwork, we present a Bloom filter-based Scalable Multicast—BSM. In BSM, themulticast information of the BSM router is setup, deleted and updated by membershipmanagement protocol. A multicast group is identified by a group tag(s,G), where s is thesource address and G is the D class IP multicast address. Bloom filter is used to presentthe multicast information in each interface of the routers. When a multicast packetarrives at the router, the group tag(s,G) in the header will be hashed by the hashfunctions. If the results are matched, the packet will be forwarded toward this interface.Simulation results show that BSM can not only support hundreds of thousands ofmulticast groups with long-lived membership, but can also support large multicastgroup size. Meanwhile, BSM can achieve high forwarding efficiency and lowbandwidth overhead.4. Aiming at the controllability problem of multicast transmission, a service leverbased Edge-to-Edge Dynamic Flow Control Multicast (E2E-DFCM), which isindependent from the backbone network, is proposed. The main idea of E2E-DFCM isas follows: The packets which have been labeled with Quality Effect Identifier (QEI) isgathered and remapped by Sending Video Gateway (SVG). Receiving Video Gateway(RVG) periodically sends multicast flow status information to SVG, including delay,loss rate, etc.; SVG dynamically remaps and classifies packets according to QEI andflow status information feedback from RVG, and reassigns each QoS level flow ratesbased on their utilities. Once the QoS of receivers can not be satisfied (i.e.,average delayand loss rate exceed the tolerable range), RVG even requests to down-grade its level,and SVG will reduce the sending rate. In the end, simulation results show thatE2E-DFCM can effectively adjust the sending rate dynamically and satisfy the diversityof user service lever for large-scale streaming media multicast transmission.5. Based on the above research work, a Labelcast switch node prototype based on NetMagic experimental platform is designed and implemented. There is a UserModule(UM) in NetMagic platform, which can provide hardware logic reconfigurablefunction. And the LTP packet processing is implemented by the design of UM. When aLTP packet is arriving at the Labelcast switch node, the packet processing includes:modifying the time and TTL field, recomputing the IP header checksum, looking up thelabel table, getting the next hop port, and replacing the label field, etc. Meanwhile, aLabelcast steaming media transmission prototype system is built and deployed. Thestreaming media flows are monitored in the real experimental environment, and thesuitable paths will be chosen according to the monitor results. The prototype systemvalidates the feasibility and effectiveness of LMTA. Labelcast steaming mediatransmission prototype system has already deployed in some commercial IPTVtransmission platform, and the implementation of key technologies has been achieved.In summary, we focus on the adaptability, scalability and controllability problemsfor large-scale streaming media transmission technologies. We believe that these workshave academic and practical value for advancing the theory and practicability of theabove research.