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A Throughput Analysis of Reliable Multicast Protocols in an Active Networking Environment. M. MAIMOUR & C. PHAM ISCC’2001, Tunisia. Outline. Introduction Reliable multicast Active networks contribution Active reliable multicast protocols evaluation Conclusions. Source. Unicast.
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A Throughput Analysis of Reliable Multicast Protocols in an Active Networking Environment M. MAIMOUR & C. PHAM ISCC’2001, Tunisia
Outline • Introduction • Reliable multicast • Active networks contribution • Active reliable multicast protocols evaluation • Conclusions
Source Unicast • Separate copies are sent to multiple destinations
Source Multicast • Only one copy is sent at the common links
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
End-to-end Solutions • Sender-based (Acks) • Receiver-initiated (Nacks) • Receiver-initiated with local recovery: • Timer-based NACK suppression (SRM) • Hierarchical schemes (RMTP, TMTP,…)
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
NACK4 Active local recovery • routers perform cache of data packets • repair packets are sent by routers, when available data data data5 data1 data2 data1 data3 data2 data4 data3 data5 data4 data5 data4 data1 data2 data3 data5
NACK4 NACK4 data4 NACK4 NACK4 only one NACK is forwarded to the source NACK4 Global NACKs suppression
NACK NACK data NACK NACK NACK Local NACKs suppression
data4 NACK4 data4 NACK4 data4 data4 data4 NACK4 data4 data4 NACK4 data4 data4 data4 data4 Active subcast features • Send repair packet only to the relevant set of receivers
Network model F active routers among N. B receivers in a local group 2 kinds of receivers: linked and free
Active reliable multicast strategies S1 : global NACK suppression S2 : local NACK suppression S2S : + subcast from the source S3 : global NACK suppression subcast from the routers S3S : + subcast from the source
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
Main results • Benefit of active routers • Local vs global suppression • Benefit of the subcast • Active routers density and processing power
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
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