Fast Ethernet is Sometimes Faster than Gigabit Ethernet on LFN - Observation of Congestion Control of TCP Streams

M. Nakamura, M. Inaba, and K. Hiraki (Japan)


TCP, Congestion Avoidance, Packet Spacing, IPG


With the rapid progress of network technology, over 10Gbps domestic backbone network is ready to use, and Gigabit Ethernet is now quite common in ordinary envi ronment. On the other hand, it is well known that current congestion control mechanism of TCP/IP doesn't fit well to the network with long latency and wide bandwidth, called Long Fat Pipe Network (LFN). In this paper, we show our observation on TCP/IP 7500-mile data transfer between Maryland and Tokyo, where the bottleneck is OC-12 APAN line. Surprisingly, throughput of Fast Ethernet is sometimes much faster than Gigabit Ethernet whose throughput is very unstable. We inspect these strange phenomena in milli-second order and conclude that it's due to bursty transmission of Gigabit Eth ernet, and transmission rate control using Inter Packet Gap (IPG) is effective and improves its performance. We expect transmission rate control becomes more important when 10 Gigabit Ethernet is commonly used.

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