Multicast Transport Protocols: A Survey and Taxonomy

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

2. Contents • Introduction • Taxonomy • Survey of Multicast Transport Protocols • Conclusion

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

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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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