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Re: [dhcwg] netboot load balancing (was: draft-ietf-dhc-dhcpv6-opt-netboot-05 - how to proceed?)

Thomas Huth <THUTH@de.ibm.com> Fri, 23 October 2009 08:47 UTC

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From: Thomas Huth <THUTH@de.ibm.com>
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Subject: Re: [dhcwg] netboot load balancing (was: draft-ietf-dhc-dhcpv6-opt-netboot-05 - how to proceed?)
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Thomas Narten <narten@us.ibm.com> wrote on 22/10/2009 20:14:29:

> I am opposed to relying on DNS round robin as the
> default/best/recommended approach to do load balancing when booting.
>
> Round Robin DNS load balancing is not officially supported in the IETF
> because the only way you can get it to work properly is to disable DNS
> caching (i.e, use TTLs of 0) so that a query always goes back to a
> server than can explicitely modify the ordering. But disabling caching
> has negative implications for DNS performance, reliability, etc. You
> then also have to have specially modified servers (that reorder
> results based on various criteria) that are again not officially
> blessed by the IETF.

I don't think that DNS caching is an issue when we're talking about
netbooting. The firmware normally lives for just some few seconds, so it
will not use the IP address of the server for a very long time.

Another possibility to do some kind of load balancing might be to use HTTP
as download protocol and then to use the HTTP-Redirect mechanism to point
the client to another server. Or maybe to use anycast, as Jarrod suggested?
Anyway, there seem to be a couple of other possibilities to do load
balancing (and I guess also failover handling), so we do not urgently need
this at the DHCP level already. So we will definitely remove the
multi-option approach from our draft and submit a new version soon.

Mit freundlichen Grüßen / Kind regards,
   Thomas Huth
                                                                           
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