Cell Relay Archive

[fahad@cs.pitt.edu (Fahad A Hoymany)]

Rick Jones (raj@cup.hp.com) wrote:

: I think that maybe it si time to re-visit the Nagle algorithm. When it
: was first proposed, I'm *guessing* that there was essentially one
: common TCP MSS (Ethenret's?) and it was relatively small. So basing

  Ethernet's MTU is 1500 bytes which is relatively large.

: the send decision (in part) on the size of the send relative to the
: MSS was pretty well a fixed decision point that apps could code to if
: needed.

: Today, we have a plethora of MSS's out there - Ethernet, Token Ring,
: FDDI, ATM, Fibre Channel, ad nauseum. Moving a fixed application
: among these networks means that it is moving through a wide range of
: MSS values, and the one value it picked will almost certainly be
: wrong.

  The MSS value is based on the smaller of the two MSS's advertized by
  the two ends. When connection is established a smaller MSS may be
  used if fragmentation occurs.

: What if... (can't work for HP unless you say that from time to time :)
: instead of working off of the MSS, which varies, the send decision
: worked off of the header (which varies less) - that is to say, the
: send/wait decision would be based on the ratio of the send size to the
: size of the TCP header?  That way, we could say that you always send
: when efficiency (from TCP's standpoint) is > 88% or some other value.

   I am not sure I undestand what you are trying to do here. The MSS has
   nothing to do with the window size. It is used, though, for the slow 
   start window, but that's a different story.

: I think that this is better than the alternative I've heard requested
: by folks emailing me on performance questions - enabling immediate
: ACK's... I've even heard (unsubstatiated) that one "latest, hottest
: thing" in OSes from the Pacific Northwest may be doing this already.

: rick jones


Take care
Fahad