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Re: [Xen-devel] TCP state between domU and client

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] TCP state between domU and client
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Tue, 24 Apr 2007 17:28:31 +0100
Cc: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
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> I have a query.
> How is a TCP connection state maintained across domUs and a remote client?
> Any pointers to the code will be really helpful.

In general, Xen is well out of the way of this as Mats explained.  Xen 
provides virtual network devices and normal TCP mechanisms operate over the 
top of this.

I believe Xen arranges for an ARP advertisement to be sent to the network 
(actually, the guest's driver does this) when a live migration is completed.  
This is not strictly necessary, but it ensures that the other entities on the 
network know that the guest has moved so that the TCP connection doesn't hang 
until the VM is rediscovered...

I imagine this is primarily so that switched networks can change their 
knowledge of the topology; don't know if there are any other issues involved.

Cheers,
Mark

> Second question ,Can I run a Xen hypervisor inside a domU, making this domU
> as the host and subsequent domUs  as guests running over this guest domU ?
> Just asking this out of curiosity.
>
> Thank you
>
> ~psr



-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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