Subject: [Idr] Last Call: <draft-ietf-idr-ix-bgp-route-server-10.txt> (Internet Exchange BGP Route Server) to Proposed Standard

From: The IESG <[email-masked]>
Date: Tue, 24 May 2016 15:43:41 -0700

The IESG has received a request from the Inter-Domain Routing WG (idr) to
consider the following document:
- 'Internet Exchange BGP Route Server'
  <draft-ietf-idr-ix-bgp-route-server-10.txt> as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits
final comments on this action. Please send substantive comments to the
[email-masked] mailing lists by 2016-06-07. Exceptionally, comments may be
sent to [email-masked] instead. In either case, please retain the
beginning of the Subject line to allow automated sorting.

Abstract

   This document outlines a specification for multilateral
   interconnections at Internet exchange points (IXPs).  Multilateral
   interconnection is a method of exchanging routing information between
   three or more external BGP speakers using a single intermediate
   broker system, referred to as a route server.  Route servers are
   typically used on shared access media networks, such as Internet
   exchange points (IXPs), to facilitate simplified interconnection
   between multiple Internet routers.

The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-idr-ix-bgp-route-server/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-idr-ix-bgp-route-server/ballot/

No IPR declarations have been submitted directly on this I-D.

---

From: Marco Marzetti <[email-masked]>
Date: Wed, 25 May 2016 16:22:44 +0200

On 2016-05-25 00:43, The IESG wrote:
> _______________________________________________
> Idr mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/idr

All,

Beside i agree on the most part of this draft i would like to underline 
how bullet 2.2.2 breaks the the nature of BGP itself.

The exact part i am referring to is:
"""
  As a route server does not participate in the process of forwarding
    data between client routers, and because modification of the AS_PATH
    attribute could affect route server client BGP Decision Process, the
    route server SHOULD NOT prepend its own AS number to the AS_PATH
    segment nor modify the AS_PATH segment in any other way.
"""

I firmly think that it really has to state "MUST NOT" instead of "SHOULD 
NOT".

 From a route-server client point of view that breaks the natural BGP 
best selection process and forces you to purely rely on LOCAL_PREFERENCE 
which in turns breaks your traffic engineering because it forces you to 
prefer/not-prefer the prefixes learned over the route server in place of 
those learned, for instance, over a private session or another IXP.

Regards

-- 
Marco

---

From: Nick Hilliard <[email-masked]>
Date: Tue, 31 May 2016 16:40:16 +0100

> those learned, for instance, over a private session or another IXP.

It doesn't "break" the decision process mechanism.  Localpref might be
ugly, but using it doesn't violate the bgp protocol.

This statement needs to be "MUST NOT".  Technically you can run a route
server even if you insert the intermediate ASN into the path.  The only
absolute "MUST" is that you mustn't change the next-hop; otherwise you
end up with a router instead of a route server.

RFC2119 is a pain because there is no way of differentiating between
"SHOULD NOT", meaning "on balance it would be a better idea not to do X"
and "SHOULD NOT", meaning "if you even _think_ about doing X, you need
your head examined and the only reason we specified SHOULD NOT instead
of MUST NOT in this situation because of some technicality that
prevented us from doing so".  The text in 2.2.2 veers slightly in the
direction of the latter interpretation.

Nick