[libvirt-users] Live Migration UDP implementation

Eric Blake eblake at redhat.com
Mon May 23 18:48:49 UTC 2011

On 05/23/2011 11:51 AM, prakash hr wrote:
> Hi all,
> For my academic project to analyse the Performance of transport protocols in
> Live Migration of Virtual Machines.I have configured the live migration
> using tcp and I succeed the live migration.
> Now for my further remaining project work I need to do the same thing for
> the UDP implemataiton.When I changed the command in virsh, (My fianl command
> in TCP is virsh migrate --live ubuntu21 qemu+ssh://
> to udp it is not workng. It is given that qemu embeds user
> mode network stack which includes tcp,dhcp,udp.etc within the wemu process.
> Its giving the error no API found for UDP.
> ---Now i want to implement the patch file for migration using UDP if
> possible.

Why?  UDP is inherently unreliable, and live migration is something
where you want inherent reliability.  That is, you risk data loss if the
receiving end does not receive and act on every packet sent by the
sender, and the sender can't know whether the migration was successful
unless the receiver acknowledges receipt.  At which point, either you
are reinventing reliability on top of UDP, or you can use the
reliability already built into TCP.

> ---Is any patch file available so that modifying that patch file will
> perform the Live Migration using UDP.

No one has written a patch for this, for the above reasons.  Since this
is free software, you are welcome to do so yourself, but unless you can
prove that you can come up with significant speed improvements without
adding any risk of data loss, it's not likely to be accepted upstream.

Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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