Is there situation that multiple root servers installed behine multiple routers within one AS?
e.g.
/ ------ Router 1 ---- Root Server-F-1
AV8----- ASBR-------Router-P /
\
\ ----- Router 2 ---- Root Server - F-2
If router-P enables PPLB, would there be some problem with TCP based DNS requests?
Joe
-----Original Message-----
From: owner-dnsop@xxxxxxxxxxxxxxxxx [mailto:owner-dnsop@xxxxxxxxxxxxxxxxx] On Behalf Of Iljitsch van Beijnum
Sent: Friday, October 01, 2004 4:49 PM
To: Dean Anderson
Cc: dnsop@xxxxxxxxxxxxxxxxx; ietf@xxxxxxxx
Subject: Re: [dnsop] Re: Root Anycast (fwd)
On 1-okt-04, at 2:48, Dean Anderson wrote:
>> Note though that it's *very* hard to create a setup where packets are
>> delivered to different multicast instances, as it's hard to imagine
>> how any real-world anycast setup could match the criteria in
> Its quite easy for anycast: (real names used, but not real
> relationships)
> Av8
> / \
> sprint att
> \ /
> F-root
> If Av8 turns on PPLB, traffic to F-root will go through both sprint
> and att on a per-packet basis.
No, that won't happen because in order for BGP to install multiple
paths in the routing table, the following conditions must be met:
"To be candidates for multipath, paths to the same destination need to
have the following characteristics equal to the best path's
characteristics:
[...]
â One of the following:
â Neighboring AS or sub-AS (before the eiBGP Multipath feature was
added)
â AS-PATH (after the eiBGP Multipath feature was added)"
(From the URL I cited in my previous message.)
In this case either of the sub-conditions won't be met.
Per packet load balancing is inappropriate in cases where the entire
path is different, as the limitations of the inferior path are imposed
on the full set. BGP has enough knobs to distribute the load without
this anyway. FIB-based load balancing is only appropriate when a small
part of a single path is populated with more than one physical link.
And in most of those cases, load balancing mechanisms that make sure
one flow runs over one link are more desirable. Only in cases where
this leads to a significantly unbalanced traffic distribution, per
packet load balancing is a good idea. (But even then most people don't
enable it as they are (too, IMO) afraid of packet reordering.)
.
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