Re: [Xen-users] port allocation on domU guest machine.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-01-08 at 10:38 +0000, Brendan Moynihan wrote:
> Hello,
> 
> I am running a tcp server process on a domU guest machine.
> Connections are established to the server, payload exchanged and the
> connection is closed in a non persistent(non keep alive) tcp manner.
> The client is external to the bare metal machine. 
> 
> Because the connections are ephemeral, 1000s of connections up to an
> observed peak of ~15500 connections go to TIMED_WAIT state.
> 
> This is expected behaviour from TCP kernel perspective.
> 
> However traffic throughput is adversely impacted with the kernel unable
> to accept connections.
> 
> 
> Does the VM (domU instance) have access to the full range of ports?

Each domU is a completely independent kernel with its own network stack
and IP address, so yes the full range of ports should be available.

Could it be possible that a firewall (e.g. in dom0 or further upstream)
is doing NAT (or something else) and thereby introducing a bottleneck on
the total number of ports flowing through it?

Ian.


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