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

From: [email-masked]
Date: Sat, 16 May 2015 02:58:28 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.
 This draft is a work item of the Inter-Domain Routing Working Group of the IETF.

        Title           : Carrying next-hop cost information in BGP
        Authors         : Ilya Varlashkin
                          Robert Raszuk
                          Keyur Patel
                          Manish Bhardwaj
                          Serpil Bayraktar
	Filename        : draft-ietf-idr-bgp-nh-cost-02.txt
	Pages           : 10
	Date            : 2015-05-16

Abstract:
   BGPLS provides a mechanism by which Link state and traffic
   engineering information can be collected from internal networks and
   shared with external network routers using BGP.  BGPLS defines a new
   Address Family to exchange this information using BGP.

   BGP Optimal Route Reflection (ORR) provides a mechanism for a
   centralized BGP Route Reflector to acheive requirements of a Hot
   Potato Routing as described in Section 11 of [RFC4456].  Optimal
   Route Reflection requires BGP ORR to overwrite the default IGP
   location placement of the route reflector; which is used for
   determining cost to the nexthop contained in the path.

   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.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-idr-bgp-nh-cost/

There's also a htmlized version available at:
https://tools.ietf.org/html/draft-ietf-idr-bgp-nh-cost-02

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-ietf-idr-bgp-nh-cost-02

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

---

From: Nick Hilliard <[email-masked]>
Date: Sun, 17 May 2015 13:42:50 +0100

>    path from a peer perspective rather than local BGP speaker own

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.

Nick

---

From: Robert Raszuk <[email-masked]>
Date: Sun, 17 May 2015 17:18:43 +0200

Hi Nick,

draft-ietf-idr-bgp-nh-cost is just a helper and companion document
to draft-ietf-idr-bgp-optimal-route-reflection.

The observation you make is already described in the latter one.

Moreover as of the current version of the draft there are three modes of
optimality from the perspective of RR:

-A- per RR logical placement
-B- per (peer/update) group logical placement
-C- per client logical placement

See section 2 of draft-ietf-idr-bgp-optimal-route-reflection for more
details.

draft-ietf-idr-bgp-nh-cost helps with all three cases eliminating the need
for remote SPF computation(s) which to some folks was the fundamental
concern in moving further with ORR :).

As of today I am aware of one large implementation which did all -A-, -B- &
-C- options as well as other implementation which did only -A-.

As far as your concern about implementation issues let's observe that
finnaly RRs are moving to x86 compute blades (where they always really
belonged). With that scalability of their processing does significantly
increses.

Best,
r.

On Sun, May 17, 2015 at 2:42 PM, Nick Hilliard <[email-masked]> wrote:

> _______________________________________________
> Idr mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/idr
>

---

From: iLya Varlashkin <[email-masked]>
Date: Mon, 18 May 2015 08:46:14 +0100

Hi Nick,

> On 17 May 2015, at 13:42, Nick Hilliard <[email-masked]> wrote:
> 

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

---

From: Nick Hilliard <[email-masked]>
Date: Fri, 22 May 2015 12:44:29 +0100

On 18/05/2015 08:46, iLya Varlashkin wrote:
> 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.

ok cool. this addresses any concerns I have about the draft.

Nick

---

From: "John G. Scudder" <[email-masked]>
Date: Fri, 22 May 2015 09:50:07 -0400

I notice this version is a big update compared to previous versions – you've abandoned NH-SAFI and are using BGP-LS instead. I personally have no problem with this change, but considering it's a working group draft, I think it would be a good idea for the authors to provide the WG with a summary of the motivation for the change.

Thanks,

– John