Messages in this thread | | | Date | Sat, 27 Feb 1999 04:10:06 -0500 | From | Josip Loncaric <> | Subject | Re: Linux 2.2.2 TCP delays every 41st small packet by 10-20 ms |
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Our MPI-based applications involve communicating processes where message delivery times have to be on the order of 100-200 MICROseconds, not 200 milliseconds. Therefore, Nagle is turned off via the TCP_NODELAY socket option, and switched fast ethernet is used. Data aggregation suitable for a fast typist is an impediment to MPI, where delays must be 1000 times shorter.
Sincerely, Josip
Rogier Wolff wrote: > > David Miller wrote: > > > > 2) Even if your fix was to be the final one, we have to be careful, > > as just blindly ACK'ing immediately for small PSH packets is > > deadly and will kill Nagle immediately. Actually the effect is > > that nobody will be able to successfully perform Nagle to us. > >[...] > > I didn't look up RFC 896, but Richard steven says: > > We saw in 19.3 that the round trip time on an ethernet for a single > byte to be sent, acknowledged, and echoed averaged around 16 ms. To > generate data faster than this we would have to be typing more than 60 > characters per second. This means that we rarely encounter this > algorithm when sending data between two hosts on a LAN. > > (TCP/IP illustrated, (first or second edition) page 267. section 19.4)
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