1. P2PC AST : A Peer-to-Peer Multi-Cast Scheme for Streaming Data Antonio NICOLOSI {nicolosi,siddhart}@cs.nyu.edu New York University Siddhartha ANNAPUREDDY August 10 th, 2003 Cambridge, MA, USA 1 st IRIS Student Workshop

2. August 10, 2003ISW '03 — Antonio Nicolosi — NYU2 Motivation: Streaming media unfair! Multicast with homogeneously limited bandwidth –Stream 256- kbps audio to 1000’s of users –Typical DSL/cable out-bandwidth: 384 kbps   Need a forest of multicast trees

3. August 10, 2003ISW '03 — Antonio Nicolosi — NYU3 Striping the Data 2 3 4 6 1 5 7 3 1 2 7 4 5 6 Each stripe carries a fraction of the stream Peers occur once in each tree Maintenance doesn’t disrupt data delivery (fault-tolerance) –Path independence 1 3 4 5 2 6 7

4. August 10, 2003ISW '03 — Antonio Nicolosi — NYU4 (Most) Related Work SplitStream: Stripes content over multiple trees Exploits heterogeneous bandwidth scenarios Limitations –Trade-off: link stress vs. path independence –Can achieve both only with “[…] sufficient excess forwarding capacity” (unsuitable for our DSL scenario) –Number of stripes in the multicast forest bound to Pastry/Scribe’s parameters

5. August 10, 2003ISW '03 — Antonio Nicolosi — NYU5 Design Guidelines, or: the P2PC AST cookbook Stripe the content over a forest of multicast trees Build a multicast forest with a regular structure –Upstream link stress should never exceed 1 –Path independence (fault tolerance) Join by contacting an arbitrary peer Correlate peer reliability with its position(s) in the forest Trees are repaired locally upon node failures

6. August 10, 2003ISW '03 — Antonio Nicolosi — NYU6 The P2PC AST Protocol The Multicast Forest Goal: build forest with a regular structure –Use f complete trees of arity f (every node has either f children or none) 1 3 4 5 2 6 7 2 3 4 6 1 5 7 3 1 2 7 4 5 6 But … that’s too rigid!

7. August 10, 2003ISW '03 — Antonio Nicolosi — NYU7 The P2PC AST Protocol The Multicast Forest (cont’d) SplitStream: uses arbitrary (irregular) trees P2PC AST : confines “anomalies” to bottom of trees 6 1 2 3 127 4 1 345 6 7 2 346 5 7 5  Gains flexibility while preserving a regular structure 2 2 8 1 1 8 6 6 8 8

8. August 10, 2003ISW '03 — Antonio Nicolosi — NYU8 proper vs. improper peers Proper peers are leaves in all trees but one (e.g., 1 ) –In each stripe, a proper peer can occur as complete node, regular leaf or lonely leaf Improper peers have a single leaf-child in each tree (e.g., 5 ) The P2PC AST Protocol Terminology 1 3 4 52 2 1 4 53 3 2 4 51

9. August 10, 2003ISW '03 — Antonio Nicolosi — NYU9 New users join as improper peers, in the next-to-last level of each tree If a (distinct) regular leaf is given in each tree, then can join as shown before The P2PC AST Protocol Insertion — joining the system 6 1 2 3 127 4 1 345 6 7 2 346 5 7 5 1 1 8 6 6 8 2 2 8

10. August 10, 2003ISW '03 — Antonio Nicolosi — NYU10 71 17 1 7 The P2PC AST Protocol Consolidation — lazy fix-up of the multicast trees 6 3 127 109 8 54 1 45 9 7 8 3 62 2 946 5 3 8 3 3 What if there are not enough regular leaves?

11. August 10, 2003ISW '03 — Antonio Nicolosi — NYU11 2 8 The P2PC AST Protocol Deleting an improper peer 3 127 4 1 345 7 2 346 5 7 5 8 2 6 Deleting node 8 8 2 1 8 8 1 8 1 6 8 8 6 8 6

12. August 10, 2003ISW '03 — Antonio Nicolosi — NYU12 The P2PC AST Protocol Deleting a proper peer 3 127 4 1 345 6 7 2 36 5 7 2 8 1 85 6 8 6 2 6 2 8 2 8 2 2 8 2 8 2 8 8 2 Deleting node 2 4 Back to the previous case

13. August 10, 2003ISW '03 — Antonio Nicolosi — NYU13 Details left uncovered in this talk –How joining peer finds out f regular leaves –How improper peers find each other before running consolidation –How deletion completes if no children of failed node is improper peer (“expansion”) See the paper for full algorithms The P2PC AST Protocol The devil is in details

14. August 10, 2003ISW '03 — Antonio Nicolosi — NYU14 Conclusions Participants join/leave dynamically Users donate as much bandwidth as they take Fault Tolerance Regular structure  Scale to 1000’s of peers—work in progress  Security—future work

15. August 10, 2003ISW '03 — Antonio Nicolosi — NYU15 Any questions? Thank you! Sources available at: http://www.cs.nyu.edu/~nicolosi/P2PCast/