Path: utzoo!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!ulysses!smb
From: smb@ulysses.homer.nj.att.com (Steven M. Bellovin)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: PUSH bit
Message-ID: <11309@ulysses.homer.nj.att.com>
Date: 13 Mar 89 15:12:28 GMT
References: <8903130939.AA05138@ucbvax.Berkeley.EDU>
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 19

In article <8903130939.AA05138@ucbvax.Berkeley.EDU>, BRUCE@UMDD.UMD.EDU (Bruce Crabill) writes:
> You could interpret the PUSH bit as a end of logical record marker.

That is definitely the wrong interpretation.  The spec says, many
times in many places, that the PUSH bit is *not* a record marker.
See, for example, the bottom of page 7 of RFC 1011:

         Push:  There are still some phrases in the document that give a
         "record mark" flavor to the push.  These should be further
         clarified.  The push is not a record mark.

> Or you could interpret is as simply a mechanism to make sure all the data
> that is currently in the pipe is pushed out to the client.

The proper interpretation is that at least all data up to the PUSH point
must be delivered promptly.  Whether or not more data is delivered is
entirely up to the implementation; any interpretation is in conformance
with the spec.  Applications that assume that the PUSH bit is an end-of-
record mark are non-conforming.