Re: [9fans] telnet vs. godaddy whois

[Bakul Shah <bakul+plan9@bitblocks.com>]

On Wed, 16 Apr 2008 21:49:26 BST Charles Forsyth <forsyth@terzarima.net>  wrote:
> > Er... "correct" seems a bit strong. Why is Plan9 sending one
> > byte of data when it knows the receiver's window is closed?
>
> read the section of the rfc i mentioned earlier.  it probably ought to probe
> only after a retransmission timeout period, but that's not a predetermined va
> lue,
> and can be short. very short. and plan 9 is positively curt, so it's just
> typical that others should then complain.

RFC1122 page 92 says

 The transmitting host SHOULD send the first zero-window
 probe when a zero window has existed for the retransmission
 timeout period (see Section 4.2.2.15), and SHOULD increase
 exponentially the interval between successive probes.

Implementations other than Plan 9's certainly seem to wait
much longer than 19ms before the first probe.  RFC1122
suggests initializing RTO to 3 seconds and then adjusting it.

Anyway, what I really wanted to say was that somehow
"correctness" is not what comes to mind first when thinking
about TCP!  The important question is whether your
implementation interoperates with the ones your users care
about (or must deal with even if buggy).