Re: [Idr] I-D Action: draft-ietf-idr-bgp-nh-cost-02.txt

iLya Varlashkin <ilya@nobulus.com> Mon, 18 May 2015 07:42 UTC

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From: iLya Varlashkin <ilya@nobulus.com>
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Date: Mon, 18 May 2015 08:46:14 +0100
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To: Nick Hilliard <nick@foobar.org>
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Subject: Re: [Idr] I-D Action: draft-ietf-idr-bgp-nh-cost-02.txt
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Hi Nick,

> On 17 May 2015, at 13:42, Nick Hilliard <nick@foobar.org> wrote:
> 
> On 16/05/2015 10:58, internet-drafts@ietf.org wrote:
>>   This draft augments BGPLS and defines a new extensions to exchange
>>   cost information to next-hops for the purpose of calculating best
>>   path from a peer perspective rather than local BGP speaker own
>>   perspective.
> 
> correct me if I'm wrong, but if a RR starts calculating best path from the
> point of view of its clients rather than from its own perspective, this
> will require best path calculation per client on the RR (ala what goes on
> with multiple ribs in bgp route servers).  If this is the case, it might be
> worth mentioning it in the draft, because it creates significant
> implementation issues.

Yes, RR will calculate best path per client, that’s the whole idea. This has been discussed with previous versions of this draft as well as in regards to draft-ietf-idr-bgp-optimal-route-reflection (ORR). In fact ORR draft provides the foundation (per client calculations) while this draft provides means of conveying next-hop cost information.

Also, section 3 of draft-ietf-idr-bgp-nh-cost-02 does say that NHIB information is used instead of speaker’s own IGP cost.

Kind regards,
iLya