|
North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Thoughts on increasing MTUs on the internet
mark does not have posting privs and has asked me to post the following for him: --- To: Gian Constantine <[email protected]> From: Mark Allman <[email protected]> cc: NANOG list <[email protected]> Subject: Re: Thoughts on increasing MTUs on the internet Date: Thu, 12 Apr 2007 11:47:35 -0400 Folks- > I agree. The throughput gains are small. You're talking about a > difference between a 4% header overhead versus a 1% header overhead > (for TCP). This does not begin to reflect the gain. Check out the model of TCP performance given in: M. Mathis, J. Semke, J. Mahdavi, T. Ott, "The Macroscopic Behavior of the TCP Congestion Avoidance Algorithm", Computer Communication Review, volume 27, number3, July 1997. (number 35 at http://www.psc.edu/~mathis/papers/index.html) The key point is that performance is directly proportional to packet size. So, an increase in the packet size is much more than a simple lowering of the overhead. In addition, the newly published RFC 4821 offers a different way to do PMTUD without relying on ICMP feedback (essentially by trying different packet sizes and trying to infer things from whether they get dropped). A good general reference to the subject of bigger MTUs is Matt Mathis' page on the subject: http://www.psc.edu/~mathis/MTU/ allman -- Mark Allman -- ICIR/ICSI -- http://www.icir.org/mallman/
|