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

To: "Mark Williamson" <mark.williamson@xxxxxxxxxxxx>

From: "pradeep singh rautela" <rautelap@xxxxxxxxx>

Date: Wed, 25 Apr 2007 11:46:24 +0530

Cc: "Petersson, Mats" <Mats.Petersson@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx

Delivery-date: Tue, 24 Apr 2007 23:14:57 -0700

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List-id: Xen developer discussion <xen-devel.lists.xensource.com>

On 4/24/07, Mark Williamson <mark.williamson@xxxxxxxxxxxx> wrote:

> 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...

Thanks Mark, that was perfectly what i was looking for.
Can i have a pointer to code? That will be really helpful.

Thank a lot once again.

~psr

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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