Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!pdn!larry
From: larry@pdn.paradyne.com (Larry Swift)
Newsgroups: comp.protocols.iso
Subject: Re: TP0-4 question (novice level)
Keywords: TP
Message-ID: <6670@pdn.paradyne.com>
Date: 18 Oct 89 12:54:08 GMT
References: <2549@hub.UUCP> <1989Oct16.173618.25068@agate.berkeley.edu> <46993@bbn.COM>
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Reply-To: larry@pdn.paradyne.com (Larry Swift)
Organization: AT&T Paradyne, Largo, Florida
Lines: 23

In article <1989Oct16.173618.25068@agate.berkeley.edu> cliff@violet.berkeley.edu (Cliff Frost) writes:
>If you have two ES's connected with X.25, what cost would TP4 add if
>you used it in place of TP0?  Wouldn't header prediction algorithms work
>100% of the time in that case?  So, the extra cost would be the
>checksumming and some timer maintanence.  But, Van Jacobson originally,
>and now a whole host of other folks have shown that this processing is
>NOT a bottleneck if your transport is properly implemented (and they've
>also shown how to implement it).

In article <46993@bbn.COM> mckenzie@labs-n.bbn.com (Alex McKenzie) writes:
>The cost people were trying to avoid is coding (and memory space) cost,
>not execution cost.  I won't argue whether or not people should have

Both of you seem to be saying that the TP4 flow control (over X.25's)
doesn't contribute a performance hit over a single L4 & L3 connection.
Since I have heard of contrary experiences, can you explain?  In
particular, what are "header prediction algorithms"?


Larry Swift                     larry@pdn.paradyne.com
AT&T Paradyne, LG-132           Phone: (813) 530-8605
8545 - 126th Avenue, North
Largo, FL, 34649-2826           She's old and she's creaky, but she holds!