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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Thoughts on increasing MTUs on the internet
[email protected] wrote on 04/12/2007 04:05:43 PM: > > On Thu, 12 Apr 2007, Joe Loiacono wrote: > > > Large MTUs enable significant throughput performance enhancements for > > large data transfers over long round-trip times (RTTs.) The original > > This is solved by increasing TCP window size, it doesn't depend very much > on MTU. Window size is of course critical, but it turns out that MTU also impacts rates (as much as 33%, see below): MSS 0.7 Rate = ----- * ------- RTT (P)**0.5 MSS = Maximum Segment Size RTT = Round Trip Time P = packet loss Mathis, et. al. have 'verified the model through both simulation and live Internet measurements.' Also (http://www.aarnet.edu.au/engineering/networkdesign/mtu/why.html): "This is shown to be the case in Anand and Hartner's "TCP/IP Network Stack Performance in Linux Kernel 2.4 and 2.5" in Proceedings of the Ottawa Linux Symposium, 2002. Their experience was that a machine using a 1500 byte MTU could only reach 750Mbps whereas the same machine configured with 9000 byte MTUs handsomely reached 1Gbps." AARnet - Australia's Academic and Research Network > > Larger MTU is better for devices that for instance do per-packet > interrupting, like most endsystems probably do. It doesn't increase > long-RTT transfer performance per se (unless you have high packetloss > because you'll slow-start more efficiently). > > -- > Mikael Abrahamsson email: [email protected]
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