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Splitting messages into packets

The length of a message is not limited; it is determined by the application process. Messages must be communicated by exchanging packets. Using large packets in wormhole routed networks results in a performance penalty in both network latency and available network throughput due to network congestion. The impact of the packet size on the available network throughput has been shown in [6]: the maximum network throughput in a 512 end-node Clos network drops by 22 % if packet size 1024 is used instead of 16. Section 5.4 presents more detailed network performance measurements that are related to the characteristics of the DSNIC protocol. To avoid the performance penalty which occurs if each message is transmitted as a single packet, we have decided to split up each message into a number of limited-size packets. Each message is sent as a number of maximum size packets, and one last packet, which is smaller than or as large as the maximum size.



Marcel Boosten
Wed Mar 11 14:25:07 MET 1998