1 An Overlay Scheme for Streaming Media Distribution Using Minimum Spanning Tree Properties Journal of Internet Technology Volume 5(2004) No.4 Reporter

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An Overlay Scheme for Streaming Media Distribution Using Minimum Spanning Tree Properties

Journal of Internet Technology Volume 5(2004) No.4

Reporter：Wei-Zhi Chen

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Outline

Introduction Problem description-background work Architecture overview Simulation Conclusion

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Introduction

Real-time content delivery requires high bandwidth availability and minimum jitter in order to enhance user perceived quality.

The primary goal of the simulation model propose is to demonstrate the effectiveness of the overlay scheme introduced for a large number of users.

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Problem description-background work

As point to point connections lead to excessive bandwidth consumption and server overload, the multipoint delivery model seems quite promising.

Three major issues. Group membership Routing Packet duplication

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Group membership A control protocol for the construction of

groups. An authentication mechanism for the potential

members of each group. Routing

Construction and maintenance of the distribution trees.

Elimination of redundant traffic on the network. Packet duplication

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IP multicast An architecture for multi-point packet delivery

at the network layer. Suffer some problems

Scalability Lack of effective access control polices. No globally Inter-Domain multicast routing

protocol.

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Application layer multicast Move functionality for multipoint data delivery

to the application layer for constructing overlay network .

Deployment of overlay networks offers Support different requirements Better use of the network infrastructure without

need for changes.

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Architecture overview

Modules NDM ( Network Distribution Manager) SAS ( Streaming Access Servers )

The basic module of the architecture At lowest level , a SAS is just a proxy : it forwards

incoming media streams to one or more clients.

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The distribution architecture

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Connection point decision

…(1)

Hierarchy level

00

11

22 101010 pppeweightvalu

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Proximity

RTT( Round Trip Time ) WatchdogTimer is the maximum time allowed

for the experiment . Clients Served …

(4))_/1(10 cilentsallclientsCl

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Simulation

Overlay tree construction In order to construct an efficient overlay tree,

each SAS reports its existence to the NDM node.

G(V,E) V: the number of SAS nodes

E=N * (N-1)/2 edges

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Simulation

Distributed mini spanning tree algorithm In the first phase, messages are exchanged

between all SAS nodes and measuring the Round Trip Time( RTT ) between them.

In the second phase each SAS starts forming a tree. At the end of distribution algorithm we have a minimum weight spanning tree.

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Simulation

Scenario 1 ( client only ) SASs are assigned to transit nodes, and the cl

ients use only their knowledge about client load on each SAS.

Stress which is an intuitive metric used in overlay topologies to evaluate the quality of the overlay tree built.

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Simulation

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Simulation( scenario 1)

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Simulation

Scenario 2 ( ping only ) We evaluate the system behavior using as

SAS selection criterion only the proximity parameter.

RAP( Relative Average Delay Penalty ) is reduced by 15%, but max stress is augment from 25% to 40%

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Simulation

Scenario 3 ( formula only ) Merging ping information, client load and

hierarchy level. RAP is reduced by 15% Max stress is bigger than scenario 1 but is sm

aller than scenario 2.

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Conclusions

RAP and average stress are reduced, since the clients are connected to nearby SAS.

In future plan, a more sophisticated algorithm for SAS selection.

Documents

1 An Overlay Scheme for Streaming Media Distribution Using Minimum Spanning Tree Properties Journal of Internet Technology Volume 5(2004) No.4 Reporter