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Re: [Xen-devel] XenLoop - Inter-VM Network Loopback

  • To: "Daniel Stodden" <stodden@xxxxxxxxxx>
  • From: "Kartik Gopalan" <kartik@xxxxxxxxxxxxxxxxx>
  • Date: Mon, 11 Feb 2008 21:51:18 -0500
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Mon, 11 Feb 2008 18:51:39 -0800
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

The analogy, though not perfect, is that a loopback carries traffic
between different network endpoints within the same (virtual)
machine -- the endpoints may be in different processes, not just
the originator. XenLoop carries traffic between different network
endpoints resident in the same "physical" machine but in
different VMs. Your virtual crossover cable analogy is just how
it happens to be currently implemented. One could implement
XenLoop using other non-crossover-type designs, resulting in
more VM crosstalk or less security, but functionally what it does
would remain unchanged, which is to bypass the network
datapath through Dom0.

- Kartik

On Feb 10, 2008 2:41 PM, Daniel Stodden <stodden@xxxxxxxxxx> wrote:
> On Sat, 2008-02-09 at 21:07 -0500, Kartik Gopalan wrote:
> > We recently developed XenLoop -- a transparent inter-VM
> > network loopback mechanism. XenLoop allows unmodified
> > network applications to bypass the standard
> > network data path via Dom0 when talking with
> > other guest VMs on the same machine.
> I'm not yet through with it, and promise I'll try to deliver more useful
> comments soon. But here's the first thing which kinda bewilders me:
> A loopback sends packets back to the originator. Hence the name. You
> propose point-to-point links. A bunch of virtual crossover cables,
> similar to the original association between backends and frontends. So
> naming it 'XenLoop' is kinda misleading.
> kind regards,
> daniel
> PS: I hereby admit that XenCross sounds plain stupid. :)
> --
> Daniel Stodden
> LRR     -      Lehrstuhl für Rechnertechnik und Rechnerorganisation
> Institut für Informatik der TU München             D-85748 Garching
> http://www.lrr.in.tum.de/~stodden         mailto:stodden@xxxxxxxxxx
> PGP Fingerprint: F5A4 1575 4C56 E26A 0B33  3D80 457E 82AE B0D8 735B
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