1 IP Multicast Applications: Challenges & Solutions Bob Quinn Stardust Forums, Inc. IP Multicast Initiative

2 Agenda ID Motivation & Purpose ID Scope Multicast Application Taxonomy Primary Requirement Challenges –Heterogeneous Receivers –Reliable Delivery –Secure Multicast

3 Motivation for the Internet Draft IP Multicast Initiative - ipmulticast.com –What: Multi-vendor Forum Members are International and Cross-Industry –Why: Promote adoption of IP Multicast Overcome the Chicken-and-Egg problem –How: Education Evangelize its benefits, and describe its details Publish documentation and Host events Informational Internet Draft...

4 Purpose of the Internet Draft Informational – A Roadmap for Application Developers –An Orientation Tool –“You are here...” in terms of Application Type Application Requirements –“Here’s where to go now...”

5 Ultimate Goal of Internet Draft Help Application Developers to Avoid: –Reinventing Wheels –Spinning Wheels –Running Roughshod over IP Networks encourage “network-friendly” application designs “heads-up” when “you can’t get there from here”

6 Scope of Internet Draft Focus is on Applications –not Infrastructure or Mechanics Assumption: Multicast-Enabled Network: –Already Exists –Transparent to Applications Assumption: Developer aware of mechanics –Refer to Maufer/Semeria ID for details

7 Multicast Application Taxonomy Sender/Receiver Relationships –Differentiate Multicast from Unicast –Characterize all Multicast Applications All Multicast Apps are one of Three Types: –One-to-Many –Many-to-Many –Many-to-One

8 One-to-Many Applications Analogous to the TV/Radio Broadcast Model –Useful and valid analogy, but not all there is... Push Media: headlines, weather, sports... File Distribution and Caching Announcements: network time, session schedules, randoms, keys... Monitoring: stock prices, sensors, security, manufacturing...

9 Many-to-Many Applications Multimedia Conferencing: A/V and whiteboard Synchronized Resources: Database updates... Concurrent Processing: Distributed & Parallel Shared Editing and Collaboration Interactive Distance Learning Distributed Interactive Simulations (DIS) Multi-Player Gaming, Chat Groups Jam Sessions

10 Many-to-One Applications Many are request/response... Resource Discovery: Service Location, Anycast Data Collection Auctions Polling Juke Box

11 Multicast App Requirements Bandwidth, Delay and Jitter –Multicast Apps are no different from Unicast –Useful to characterize needs nonetheless... Multicast is a Special Case when Servicing: –Heterogeneous Receivers –Reliable Data Delivery –Security

12 Heterogeneous Receivers Adapting to receiver rates, delays and jitter –Difficult with unicast, but worse with multicast Strategies and Challenges: –Feedback loops - Danger of implosions –Forward Error Correction - Uses bandwidth –Shared Learning - Privacy Issues –Local Recovery - Management Issues No standards yet. Research effort informal.

13 Reliable Data Delivery Receivers tolerant of delay, but not loss –TCP model doesn’t translate (implosion) Strategies and Challenges: –NAKs - implosion potential still exists –FEC, Shared Learning, and Local Recovery are all also relevant No standards yet. RMRG in IRTF is defining the problem

14 Multicast Security Receivers and Senders are wary –Don’t trust data, or each other, or anyone else –Unicast is hard, and multicast is HARDER Challenges: authentication and key distribution Strategies: many and varied No standards yet. SMuG in IRTF is defining the problem

15 Observations Three Primary Requirements share many of the same Strategies & Challenges –Common issue is dealing with asymmetry in the sender/receiver relationship –e.g., Local Recovery - smarts in the net –Solutions may have cascade effect (?) Prevailing Consensus: we need more than one protocol to satisfy the varying application requirements in each category

16 Evaluation Is this of value? –Should this be a draft from MBoneD WG?? Any Questions? Comments? Suggestions? –Send to & mboned mail-list Also see