On Thu, 6 Apr 2006 21:37:49 -0400 (EDT),
jnc(_at_)mercury(_dot_)lcs(_dot_)mit(_dot_)edu (Noel
Chiappa) wrote:
> From: Joe Touch <touch(_at_)ISI(_dot_)EDU>
> TCPMUX doesn't 'handoff'. It expects that .. the service desired is
> served off of its port once opened after the initial exchange
> (in-band).
> .. The downside is that it then forces a two-step demultiplexing of
> incoming packets; there may be utility in a variant that allows the
> dest port to be unbound and later filled-in, or changed during the
> connection, so that services can be more efficiently demultiplexed.
I'm missing something here. A TCP connection is identified by the (srcaddr,
sport, dstaddr, dport) tuple. TCB's are looked up by this tuple. Connections
to TCPMUX will all have the same dstaddr/dport, but will presumably have
different srcaddr's, and (presumably) random sport's, and can be
distinguished that way.
Why can't the TCPMUX listener just bind the correct application to the TCB
(after figuring out what the appropriate application is), and then forget
about the connection, leaving it entirely to the application to deal with?
All packets which belong to that connection will automatically go to that
TCB, and thence to the application, with no second layer of demux needed.
Am I missing something?
No -- that's precisely how it works.
--Steven M. Bellovin, http://www.cs.columbia.edu/~smb
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