Re: [ftpext] Discouraging use of TCP "urgent data"

Fernando Gont <fernando@gont.com.ar> Sat, 25 September 2010 13:02 UTC

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Date: Sat, 25 Sep 2010 10:01:00 -0300
From: Fernando Gont <fernando@gont.com.ar>
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Cc: Alexey Melnikov <alexey.melnikov@isode.com>, ftpext@ietf.org
Subject: Re: [ftpext] Discouraging use of TCP "urgent data"
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Hi,

>> To avoid head-of-line blocking. If the user has e.g. already sent a
>> number of commands to the FTP server, and then issues an ABOR, you
>> don't really want the server to process all the commands that are
>> already in the pipeline, but want it to "jump" to your ABOR. -- and
>> that's what the TCP urgent mechanism is leveraged for.
> 
> So FTP client implementations actually "pipeline" commands like that
> without waiting for the responses? Isn't that pretty silly in case the
> first command gets an error back?

IIRC, they are allowed to do so. In some cases, it might make sense
(e.g. a large transfer between two remote sites)

Other protocols allow for the same sort of pipelining. e.g., I do recall
the POP3 specification explicitly mentioning this...

Thanks!

Kind regards,
-- 
Fernando Gont
e-mail: fernando@gont.com.ar || fgont@acm.org
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1

[ftpext] Discouraging use of TCP "urgent data" Alexey Melnikov
Re: [ftpext] Discouraging use of TCP "urgent data" William F. Maton
Re: [ftpext] Discouraging use of TCP "urgent data" Fernando Gont
Re: [ftpext] Discouraging use of TCP "urgent data" William F. Maton
Re: [ftpext] Discouraging use of TCP "urgent data" Daniel Stenberg
Re: [ftpext] Discouraging use of TCP "urgent data" Fernando Gont
Re: [ftpext] Discouraging use of TCP "urgent data" William F. Maton
Re: [ftpext] Discouraging use of TCP "urgent data" Daniel Stenberg
Re: [ftpext] Discouraging use of TCP "urgent data" William F. Maton
Re: [ftpext] Discouraging use of TCP "urgent data" Fernando Gont
Re: [ftpext] Discouraging use of TCP "urgent data" Fernando Gont