1 / 27

IP Multicast Channels: EXPRESS Support for Large-scale Single-source Applications

IP Multicast Channels: EXPRESS Support for Large-scale Single-source Applications. Authors: Hugh W. Holbrook and David R. Cheriton Presenter: Mridul Sharma. Contents. Introduction IP Multicast Channels ECMP Multi-source Multicast Applications Cost and Scalability

duena
Download Presentation

IP Multicast Channels: EXPRESS Support for Large-scale Single-source Applications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. IP Multicast Channels: EXPRESS Support for Large-scale Single-source Applications Authors: Hugh W. Holbrook and David R. Cheriton Presenter: Mridul Sharma

  2. Contents • Introduction • IP Multicast Channels • ECMP • Multi-source Multicast Applications • Cost and Scalability • Costing Overhead and Proactive Counting • Conclusion

  3. Focus Provide explicit support for large-scale multicast applications by extending the IP Multicast service model to support multicast channels

  4. IP Multicast: Group Model • Hosts aggregated into groups with single address • Good for multicast discovery & small scale meetings over the internet

  5. Problems • Strained for very large scale multicast applications such as Internet TV • Violates common ISP billing models • Provides no indication of group size • No restriction on allowed senders • World-wide unique multicast address • Scaling IP multicast routing for conventional group semantics remains an issue

  6. IP Multicast Channels • A multicast channel is a datagram delivery service identified by a tuple (S, E) where S is the sender’s source address and E is a channel destination address. • Only the source host S may send to E.

  7. S S Channel vs. Group Addressing (S,E) G

  8. 224 class D addresses allocated by IANA Routers identify a channel multicast datagram by its destination address Same service interface as IP Multicast for packet transmission to, and reception on, a channel Single-source IP Multicast Addresses 222.0.0.0 239.255.255.255 IP Multicast addresses Single-source multicast Addresses (232.*.*.*)

  9. EXPRESS Service Interface Extensions • Source service interface • Count = CountQuery(channel, countId, timeout) • channelKey(channel, K(S, E) ) • Subscriber service interface • Result = newSubscription(channel [, K(S, E) ]), • Count(channel, countId, count)

  10. Advantages • Source • 224 channels per source • Address management is simplified • Authenticated subscription option • CountQuery mechanism (number of subscribers or subscriber vote)

  11. Advantages (Contd.) • Subscriber • Receives traffic only from the source it designates • Ability to provide feedback

  12. Advantages (Contd.) • ISP • Provides basis for charging • Counting facility increases revenue • EXPRESS is relatively simple to implement and manage

  13. EXPRESS Count Management Protocol • A single common management protocol • Maintains both the distribution tree and supports source-directed counting and voting • RPF is used to route subscriptions and unsubscriptions towards the source

  14. ECMP • Generic Counting Operation • CountQuery • Count • CountResponse • A router can initiate a query without source co-operation

  15. ECMP (Contd.) • Distribution Tree Maintenance • New subscription • Unsubsciption • Router can use either TCP or UDP mode for ECMP

  16. ECMP: Subscription

  17. ECMP (Contd.) • Neighbor Discovery • Periodic CountQuery message • countId: neighbors; all channels • EXPRESS Packet Forwarding • Forwarding Information Base entries at each router • Forwarding procedure is nearly identical to IP Multicast

  18. ECMP (Contd.) • Authenticated ECMP vs. End-to-end Encryption • Authentication provides restricted access while encryption provides confidentiality

  19. ECMP Advantages • Simple integrated protocol • Supports subscription, multicast channel maintenance and counting • No change in host OS if it supports IP Multicast • Multicast traffic travel only along paths from source to subscribers

  20. Multi-source Multicast Applications • Multiple channels, one per source • Applicable when new source is going to transmit for extended period of time • Several sources sharing a channel using higher level relaying through the channel’s source host • Supported by middleware layer for session management

  21. The Session Relay Approach

  22. Advantages of SR Approach • Appropriate placement of SRs to minimize communication is under application control • Applications can have additional backup SRs for fault tolerance, placement, switching over etc • “Hot” and “cold” standby • SR can provide application-specific functionality

  23. Session Relaying • As an ISP Service • For other applications • Cost/ Performance

  24. Cost and Scalability • Cost of router FIB memory for channels • Cost of management-level router state • Cost of maintaining this state

  25. Counting Overhead & Proactive Counting • Counting Overhead • Small for large-scale channels if approximated over long time periods • Excessive use of counting is expensive • Proactive Counting • Receivers and routers proactively send count messages upstream

  26. Related Work • Service Models and Routing • Accounting • Counting

  27. Conclusions • Straightforward extension to the conventional IP multicast • Simple implementation • Additional capabilities like access control, accounting and local-to-host multicast address allocation • Almost single source and truly multi source multicast applications can be implemented

More Related