Re: [Xen-devel] arp reply for migration

[Daniel Stodden <stodden@xxxxxxxxxx>]

On Sun, 2008-03-09 at 14:56 +0800, tgh wrote:
> hi
>   I read the live migration paper,and in the paper,"...generate an 
> unsolicited ARP reply from the migrated host",and which is the migrated 
> host? source physical node,or destination physical node,or VM?and i 
> guess ,it is destination physical node, is it right? if it is, then when 
> is the ARP reply generated ?after the guestOS has been resumed or when ? 
> i did not find the code for it ? could you help me

It is certainly sent fron the destination host, i.e. after migration.

The purpose is to let peers (i.e. hosts to which connections (e.g. on
the ip layer) are maintained across the migration phase) know that the
destination hardware address (i.e. on the mac layer) has changed. 

Even if you don't change the mac address, as the paper suggests, you
would still need to send -something- in order to let switches learn that
the migrated guest has been moved to a different physical port on that
switch.

If you don't understand this, I suggest to get yourself a book on the
topic. See e.g. page 62 in

http://books.google.com/books?id=-btNds68w84C

regards,
daniel

-- 
Daniel Stodden
LRR     -      Lehrstuhl fÃr Rechnertechnik und Rechnerorganisation
Institut fÃr Informatik der TU MÃnchen             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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