North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: packet reordering at exchange points
On Mon, Apr 08, 2002 at 02:18:52PM -0700, Paul Vixie wrote: > > > packet reordering at MAE East was extremely common a few years ago. Does > > anyone have information whether this is still happening? > > more to the point, does anybody still care about packet reordering at > exchange points? we (paix) go through significant effort to prevent it, > and interswitch trunking with round robin would be a lot easier. are > we chasing an urban legend here, or would reordering still cause pain? Setup a freebsd system with a dummynet pipe, do a probability match on 50% of the packets and send them through a pipe with a few more bytes of queueing and 1ms more delay than the rest. Then test the performance of TCP across that link. There is a good paper on the subject that was published by ACM in Janurary: http://citeseer.nj.nec.com/450712.html So just how common is packet reordering today? Well I did a quick peak at a few machines which I don't have any reason to believe are out of the ordinary, and they all pretty much come out about the same: 32896155 packets received 9961197 acks (for 2309956346 bytes) 96322 duplicate acks 0 acks for unsent data 17328137 packets (2667939981 bytes) received in-sequence 10755 completely duplicate packets (1803069 bytes) 19 old duplicate packets 375 packets with some dup. data (38297 bytes duped) 53862 out-of-order packets (75435307 bytes) 0.3% of non-ACK packets by packet were received out of order, or 2.8% by bytes. -- Richard A Steenbergen <[email protected]> http://www.e-gerbil.net/ras PGP Key ID: 0x138EA177 (67 29 D7 BC E8 18 3E DA B2 46 B3 D8 14 36 FE B6)
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