Multicast Transport Protocols: A Survey and Taxonomy Author: Katia Obraczka University of Southern California Presenter: Venkatesh Prabhakar

Contents Introduction Taxonomy Survey of Multicast Transport Protocols Conclusion

Introduction Earlier mechanisms General solutions to the group communication problem Recent trends focus on Multipoint interactive applications Data Dissemination applications

Taxonomy Data Propagation Reliability Mechanism Repair request Feedback Control Retransmission Flow and Congestion Control Locus of Control Ordering Group Management Target Application

Taxonomy Data Propagation Multicast, some work with unicast too Reliability Mechanism Receiver initiated through NACKs Special site for feedback control Avoiding losses Forward Error Correction Hybrid approach

Taxonomy Repair request and Retransmission Point to Point or to the whole group NACK suppression Local recovery Feedback Control Structure based - designated site or control structure Timer based – probabilistic feedback suppression

Taxonomy Flow and Congestion Control Rate, window and token based schemes Layered Multicast – Encoding to different layers Forward Error Correction techniques Representative based congestion control Control Distributed Vs Centralized Ordering Assigning sequence numbers

Taxonomy Group Management Implicit or Explicit Variation: Authorization only while joining Target Application Generic ones Delay sensitive real time services Reliable transfers Resilience as opposed to reliability

General Purpose Protocols Reliable Broadcast Protocol Multipoint communication between sites connected by a local broadcast network Messages multicast through a token site Token site multicasts ACKs NACKs sent to Token site upon Packet loss Token site rotated among group members

General Purpose Protocols Multicast Transport Protocol Reliable and globally ordered delivery Group Master coordinates members Transmits tokens which provide ordering, congestion control Group membership allowed only when all transmit tokens are with the master Retransmission NACK based Uses fixed size transmission window

General Purpose Protocols Reliable Multicast Protocol Name service advertises multicast groups, and flow and congestion control schemes Dynamic group updation TCP-like congestion control – Timers, ACKs and NACKs used to control window size Reliability through multicasting NACKs

General Purpose Protocols Xpress Transport Protocol Designed to support a wide range of applications Explicit multicast group management protocol (MGM) TCP-like fully reliable delivery, UDP-like best effort delivery and Fast NACK modes. Sender can select ACK frequency Window and rate based flow control

General Purpose Protocols Uniform Reliable Group Communication Protocol Reliable ordered communication though a coordinator All sites keep history and coordinator knows the most up-to-date site Reliable Multicast Framework Provide framework to develop multicast protocols for various applications

Support for Multipoint Interactive Applications Multicast Transport Protocol-2 Immediate joins Master recovery Dynamic group parameter adjustment Real-Time Transport Protocol Does not assure ordered reliable delivery RTCP used for control information Avoids packet losses using probabilistic polling of set of receivers to compute rates

Support for Multipoint Interactive Applications Scaleable Reliable Multicast Distributed protocol Group management by join and session messages Log Based Receiver-Reliable Multicast Logging server (LS) logs all packets LS ACKs senders and Receivers NACK LS Secondary logging servers used as proxies and for local recovery

Support for Multipoint Interactive Applications Reliable Adaptive Multicast Protocol NACK based reliable delivery Burst and idle modes Rate based flow control Transport Protocol for Reliable Multicast Interactive Multimedia applications Group membership handled by application Multicasting NACKs and probabilistic NACK suppression

Support for Data Dissemination Services Muse Posting multicast news articles Uses cryptographic checksums and signatures on data for authentication Keep-alive messages Multicast Dissemination Protocol Fragments files to MDUs Recovery by source asking receivers for retransmission requests at end of transmission

Support for Data Dissemination Services Adaptive File Distribution Protocol Group management done by a designated group secretary No recovery mode for site failures or network partitions Tree-Based Multicast Transport Protocol Control Tree Structure – Domain manager Max tree degree defined ACKs and NACKs limited in scope

Support for Data Dissemination Services Reliable Multicast Transport Protocol Control Tree – Designated Receivers Reclaim buffers on ACKs from children Window based flow control Multicast File Transfer Protocol Modes: Unicast, Broadcast and Multicast Two pass Data Transmission protocol Open and closed Group Management

Interactivity Vs Reliabilty Resilient multicast delivery model Structure Oriented Resilient Multicast Dynamic distribution graph Unicasts NACK to each parent Extended Ring Search (ERS) to look for parents Nodes measure parents performance and react to it Mechanism to avoid loops provided

Conclusion Summary Survey and Classification of most Multicast Transport Protocols presented Multicast Congestion Control – big research area My Opinion Provides good pointers to the existing protocols Emphasizes the Application Level Framing trend in Multicast Transport Protocols