[Tsvwg] Re: [e2e] What's the benefit of out-of-order processi

[Bob Braden]

  *> From end2end-interest-admin at postel.org  Mon Sep 17 18:46:27 2001
  *> From: Jacob Heitz <jheitz at lucent.com>
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  *> To: Sam Liang <sliang at dsg.stanford.edu>
  *> CC: "Naidu, Venkata" <Venkata.Naidu at Marconi.com>,
  *>    "'Qiaobing Xie'" <xieqb at cig.mot.com>, Craig Partridge <craig at aland.bbn.com>,
  *>    tsvwg at ietf.org, end2end-interest at postel.org
  *> Subject: Re: [Tsvwg] Re: [e2e] What's the benefit of out-of-order processi
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  *> Date: Mon, 17 Sep 2001 18:36:25 -0700
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  *> The urgent pointer does not point at a range, only at a single
  *> byte. It can only deliver a single byte of out-of-band data.
  *> 

This comment reflects a (common) misunderstanding of the urgent pointer
mechanism of TCP.  [It has amazed me for 20 years that people have had
so much trouble with this!]

OSI has an out-of-band data delivery mechanism, limited to a few bytes
of urgent data.  The researchers who designed TCP hated arbitrary
limits, so they DID NOT put an out-of-band delivery mechanism into
TCP.  People keep saying, "Oh, there is an urgent pointer, THAT must be
TCP's OOB delivery mechanism", without stopping to read the spec or
think about it.  It is not!   It does not send even one urgent byte; it
sends NO urgent bytes.

The TCP urgent pointer is an (are you listening?) OUT-OF-BAND
SIGNALING MECHANISM.

Bob Braden

(Why is this discussion taking place on two lists?)


  *> Sam Liang wrote:
  *> > 
  *> >   Also, doesn't TCP's urgent pointer offer a means to deliver out-of-band
  *> > data?
  *>