A Throughput Analysis of Reliable Multicast Protocols in an Active Networking Environment

M. MAIMOUR & C. PHAMISCC’2001, Tunisia

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Outline

Introduction Reliable multicast Active networks contribution Active reliable multicast protocols

evaluation Conclusions

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Unicast

Separate copies are sent to multiple destinations

Source

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Multicast

Only one copy is sent at the common links

Source

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Reliable multicast

What is the problem of loss recovery? feedback (ACK or NACK) implosion repair duplication loss recovery isolation

Design goals reduce the feedback traffic reduce recovery latencies improve recovery isolation

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End-to-end Solutions

Sender-based (Acks) Receiver-initiated (Nacks) Receiver-initiated with local recovery:

Timer-based NACK suppression (SRM) Hierarchical schemes (RMTP, TMTP,…)

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Active Routers contribution

Use of a recovery tree = multicast tree, where intermediate nodes (active routers) perform :

Cache of data to allow local recovery Nacks suppression

Global Local

Subcast

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Active local recovery

routers perform cache of data packets repair packets are sent by routers,

when available

data1data2data3data4data5

datadatadata5

NACK4data4

data1data2data3data4data5

data1data2data3data5

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Global NACKs suppression

NACK4NACK4

NACK4

NACK4data4

NACK4

only one NACK is forwarded to the source

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Local NACKs suppression

data

NACK

NACK

NACK

NACK

NACK

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Active subcast features

Send repair packet only to the relevant set of receivers

NACK4

NACK4

NACK4

NACK4

data

4

data4

data4

data4

data4

data4

data4data4

data

4

data4

data4

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Network model

F active routers among N.B receivers in a local group2 kinds of receivers: linked and

free

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Active reliable multicast strategies

S1 : global NACK suppression

S2 : local NACK suppressionS2S : + subcast from the source

S3 : global NACK suppression subcast from the routers

S3S : + subcast from the source

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The throughput analysis

For each node, compute the mean processing time per packet.

Compute the throughput achieved by each node.

Deduce the overall throughput achieved by each protocol

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A case study: the source in S1

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Main results

Benefit of active routers Local vs global suppression Benefit of the subcast Active routers density and processing

power

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Benefit of active routers

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Local vs global suppression (S2/S3 ratio)

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Benefit of the subcast (S2S/S2 ratio)

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Active routers density

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Conclusions

Active networking can really help enhancing the reliable multicast performances

Global NACK suppression is easier to implement, and allows subcast from routers

Local NACK suppression performs well for high loss rates but is difficult to tune

Subcasting is very interesting when the number of receivers is large

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Reference

M. Maimour, C. Pham. A Throughput Analysis of Reliable Multicast Protocols in an Active Networking Environment. TR.

http://www.ens-lyon.fr/~mmaimour/ Paper/TR/TR01-2001.ps.gz