ZIGZAG: An Efficient Peer-to-Peer Scheme for Media Streaming

Duc A. Tran, Kien A. Hua, Tai Do

University of Central FloridaINFOCOM 2003. Twenty-Second Annual Joint Conference

of the IEEE Computer and Communications Societies.

Chu Yi-Cheng

Outline

Issues of Peer-to-Peer Streaming Application-layered Structure

Administrative Organization Multicast Tree

Apply the Mechanism Control Protocol Join and Departure of a Client Split and Merge of Clusters

Experiment Results Conclusion

Issues of Peer-to-Peer Streaming

Bound the end-to-end delay

Deal with unpredictable users’ behavior

Efficient use of network resources

Administrative Organization

Cluster size: for any positive constant k in the bound [ k, 3k ]

LH-1

LH-2

LH-3

L0

S

Head

Multicast Tree -- Terms used

Subordinate: Non-head peers of cluster headed by X

Foreign head: Clustermates of X, X is the head of the peer at

layer j-1 Foreign subordinate:

Subordinates of clustermates Foreign cluster:

Clusters of clustermates

Multicast Tree -- Definition

Concept: Receive content from foreign heads instead of

its head. Rules:

If a peer isn’t at its highest layer, it cannot has a link.

A peer at its highest layer can only link to its foreign head.

The server links to each of its subordinates.

Example of Multicast Tree

Bound node degree to O((3k-1)*(3k-1)+(3k-1)) = O(k2)

Bound tree height to O(H) = (logkN)

k = 4, H (number of layers) = 3

Control Protocol

Maintain the positions and connections in the multicast tree and the administrative organization.

Periodically communicate with: Clustermates

- Subordinates: (position, degree) set of X- Head: (foreign cluster head, degree to foreign cluster) list of X

Parent- Reachable(X): exist a path from X to a layer-0 peer- Addable(X): X is reachable, and the cluster size of the layer-0 peer

is in [k, 3k-1] Children Y

- Receive Reachable(Yi), Addable(Yi) from children.

For a peer which highest layer is j,

Worst case: need O((j+1)*(3k-1)) + O(k2) = O(k*logkN)

Amortized worst-cast: )())19)13((/1(1

0

2 kOkkjkH

j

j

Control Protocol (cont.)

Node 2: send (2, 6) to 1, 3, 4

send {(1, 3), (3, 3)} list to head 4

send Reachable(2)=1, Addable(2)=1 to parent S

receive Reachable(), Addable() from children

k = 4, H (number of layers) = 3, size bound in [4,12]

Client Join

Client Join (cont.)

join request

Join overhead:

O(max degree × height of multicast tree) = O(k*logkN)

Client Departure

1. Peer X fail

2. Aware of failure of X

(i). Parent of X delete link of X.

(ii). Head of children of X select new parent with minimum degree for them.

(iii). Subordinates of X at layer 0~j-1 adapt new head

X’ selected from layer 0.

Failure recovery overhead:O(children number) + O(1) + O(1) = O(degree) = O(k2)

Should be O(k*logkN) considering control overhead of X’

XX’

X

X

X”Lj+1

Lj

Lj-1

L0

Z

Split overhead:

step 2:

step 4: O(degree of Y) = O(k2)

=> O(k2)

1. Split into U, V, where X U with

2. Delete links of layer j-1 whose parent and head are in different clusters in layer j.

3. Choose new parents other than X for 2.

4. Select head Y of cluster V with minimum degree.

(i). Choose new parent for children of Y.

(ii). Place Y into layer j+1 and link to X”.

Split Operation

))(min(,

VXUX liil

lixx

6kn ,))13((most at 1

knOx

n

i i

U

X

X”Lj+2

Lj+1

Lj

Lj-1

X’

V

Merge Operation

Merge overhead: step 2: O(2*(3k-1))

step 3: O(degree) = O(k2)

=> O(k2)

1. Choose new head between X, Y which are heads of two sets being merged.

(may use larger degree one)

2. Delete link from parent of lost head at layer j+1, and remove the node.

3. Select new parent of non-head members in U+V.

4. Delete links point to the same cluster at layer j+1.

5. Select new parent different from the new head with minimum degree.

Experiment Results -- Failure free

3240 node-transit-stub

2000 clients

K=5

Experiment Results -- Failure free (2)

Experiment Results -- Failure free (3)

Experiment Result -- Failure recovery

Experiment Result -- NICE comparison

NICE:

Adapt hierarchical peer clusters, but always receive content from head.

Conclusion

With O(logN) tree height, O(k2) nodes degree, the scheme maintains relative short end-to-end delay.

Obtain control overhead to O(k2) on average. Join a client can be accomplished within O(lo

gN) downward relay. Departure a client cost O(k2). Use merge, split to maintain efficient use of th

e network need O(k2) periodically invoked.