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 <ras@e-gerbil.net> 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)