Deliver Multimedia Streams with Flexible QoS via a Multicast DAG Yu Cai 02/26/2004

Paper Deliver Multimedia Streams with Flexible QoS via a Multicast DAG Jiong Yang, UIUC ICDCS 03 DAG (Directed Acyclic Graph)

Introduction Main idea: Deliver Multimedia Streams through multiple paths with QoS requirements. Contribution: –Stream partition scheme –Multi-path algorithm

Background Multimedia signals can be encoded into a number of layers (like MPEG). Layer can be combined to incrementally refine the video quality. Multicast are used for streams delivery.

Stream partition scheme The author proposed a concept called “share” as stream transmission unit. Based on share, the author proposed a stream partition scheme Example: a stream of 620 kbps, 5 layers, –Based on experiments, 10kbps per share (overhead vs flexibility), so totally 62 shares Layer 1: 2 shares, 20 k Layer 2: 4 Layer 3: 8 Layer 4: 16 Layer 5: 32

Stream partition scheme Share has shareID. Based on ShareID, you know the layer and the content. Share support QoS requirement. Why sequence ID and share ID ??? – no need ???

Stream delivery

Multicast Tree V:4 get poorer quality than its capacity because of single path delivery

Multi-path algorithm Greedy algorithm: deliver higher layer first, then lower layer; use max bandwidth path first. –More other nodes can provide lower layer than that of higher layer. –Deliver lower layer first may cause a lot of waste. –Pre-examination to prevent from delivering useless higher layer ??? not enough ??? Max for r = =500 k => 50 shares => layer 4 at most.

Greedy algorithm: example 1: s -> t 2: s -> y 3. t-> y 4. y – w – x 5. s – u – x 6. t – z – v 7. x -v

Why greedy ? Greedy algorithm has better adaptability to changing environment - robustness. –Bursty traffic –Inaccurate estimation of network bandwidth –Dynamic join and leave –Greedy  local, local changes won’t affect the result in other areas

My question What if there are congestions in the middle of the network, and you deliver a lot of useless higher layer shares? The author claim “ it happens rarely” ??? The author’s solution is to give up the useless higher layer, and retransmit the lower layer.

Learned Multipath transmission unit ? How to design a good package partition scheme ? Greedy algorithm? Heuristic algorithm? … how to design a good multipath algorithm? Solid work on simple idea can generate good paper.