A Throughput Analysis of Reliable Multicast Protocols in

A Throughput Analysis of Reliable Multicast Protocols in an Active Networking Environment M. MAIMOUR & C. PHAM ISCC’ 2001, Tunisia

Outline n n n Introduction Reliable multicast Active networks contribution Active reliable multicast protocols evaluation Conclusions 2

Unicast Source n Separate copies are sent to multiple destinations 3

Multicast Source n Only one copy is sent at the common links 4

Reliable multicast n What is the problem of loss recovery? n n feedback (ACK or NACK) implosion repair duplication loss recovery isolation Design goals n n n reduce the feedback traffic reduce recovery latencies improve recovery isolation 5

End-to-end Solutions n n n Sender-based (Acks) Receiver-initiated (Nacks) Receiver-initiated with local recovery: n n Timer-based NACK suppression (SRM) Hierarchical schemes (RMTP, TMTP, …) 6

Active Routers contribution Use of a recovery tree = multicast tree, where intermediate nodes (active routers) perform : n Cache of data to allow local recovery n Nacks suppression n Global Local Subcast 7

Active local recovery n n routers perform cache of data packets repair packets are sent by routers, when available data 5 data 1 data 2 data 3 data 4 data 5 4 NA ta da data 1 data 2 data 3 data 4 data 5 4 CK data 1 data 2 data 3 data 5 8

Global NACKs suppression K 4 C A N data 4 NA CK NACK 4 4 4 CK NA only one NACK is forwarded to the source NACK 4 9

Local NACKs suppression K C NA data NACK NA CK 10

Active subcast features Send repair packet only to the relevant set of receivers 4 a K 4 t C a. A d. Na. AC ta. K 4 4 n d. Na. ACta K 44 4 4 data ta da 4 a t a d d. NAa. Ct. Ka 44 11

Network model F active routers among N. B receivers in a local group 2 kinds of receivers: linked and free 12

Active reliable multicast strategies S 1 : global NACK suppression S 2 : local NACK suppression S 2 S : + subcast from the source S 3 : global NACK suppression subcast from the routers S 3 S : + subcast from the source 13

The throughput analysis n n n For each node, compute the mean processing time per packet. Compute throughput achieved by each node. Deduce the overall throughput achieved by each protocol 14

A case study: the source in S 1 15

Main results n n Benefit of active routers Local vs global suppression Benefit of the subcast Active routers density and processing power 16

Benefit of active routers 17

Local vs global suppression (S 2/S 3 ratio) 18

Benefit of the subcast (S 2 S/S 2 ratio) 19

Active routers density 20

Conclusions n n 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 21

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/TR 01 -2001. ps. gz 22