[Beowulf] automount on high ports

Carsten Aulbert carsten.aulbert at aei.mpg.de
Wed Jul 2 08:55:21 EDT 2008


Hi Perry,

Perry E. Metzger wrote:
> 
> Okay. In this instance, you're not going to run out of ports. Every
> machine might get 1341 connections from clients, and every machine
> might make 1341 client connections going out to other machines. None
> of this should cause you to run out of ports, period. If you don't
> understand that, refer back to my original message. A TCP socket is a
> unique 4-tuple. The host:port 2-tuples are NOT unique and not an
> exhaustible resource. There is is no way that your case is going to
> even remotely exhaust the 4-tuple space.

Well, I understand your reasoning, but that's contradicted to what we do see

netstat -an|awk '/2049/ {print $4}'|sed 's/10.10.13.41://'|sort -n

shows us the follwing:

665
666
667
668
669
670
671
672
673
674
675
676
677
[...]
1017
1018
1019
1020
1021
1022
1023

Which corresponds exactly to the maximum achievable mounts of 358 right
now. Besides, I'm far from being an expert on TCP/IP, but is it possible
for a local process to bind to a port which is already in use but to
another host? I don't think so, but may be wrong.

Cheers

Carsten
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