Subject: Re: Last Call comments on draft-ietf-l3vpn-virtual-hub

From: Eric Rosen <[email-masked]>
Date: Fri, 07 Dec 2012 09:50:36 -0500

Thanks for addressing most of my comments, and sorry for the delay getting
back to you.  There are just a few comments that I want to discuss further.

1. Section 7.9, "Use of Ingress Replication with I-PMSI A-D routes".

   The document should make it clear that these procedures are required to
   be implemented (by all the PEs of a given MVPN) ONLY under the following
   conditions:
   
   - At least one of those PEs is a V-hub or V-spoke PE for the given MVPN. 

   - The given MVPN is configured to use the optional procedure of using
     Ingress Replication to instantiate an I-PMSI.

2. Abstract

   I continue to think that the second paragraph of the abstract is
   misleading in its claim that "the approach described in this document may
   allow to reduce bandwidth inefficiency", given that the approach may also
   allow an increase in bandwidth inefficiency.  Maybe replace "may" with
   "may under certain circumstances".

   (I also continue to think that the abstract would be improved if it
   mentioned that the draft uses "hub and spoke" procedures to provide
   any-to-any service, but that's just a suggestion.)

3. Multi-level hierarchy outside the scope of the document

   When I pointed out that the procedures don't appear to generalize easily
   to support of a multi-level hierarchy, you replied "multi-level hierarchy
   is outside the scope of this document".  That's fine, but the document
   should have a statement to that effect.

4. Installation of default route in a V-hub VRF

   I'm still having trouble understanding the point of the following
   paragraph:

        When a V-hub of a given VPN originates a VPN-IP default route for
        that VPN, the V-hub MUST NOT install in its VRF of that VPN a
        default route, unless this route has been originated either (a) as a
        result of the V-hub receiving an IP default route from one of the
        CEs of that VPN connected to it, or (b) as a result of the V-hub
        receiving (and importing) a VPN-IP default route from some other PE,
        or (c) the VRF being provisioned with a default route pointing to
        the routing table on the same PE that maintains the Internet routes.

   Could you give an example to show that this restriction is necessary?

5. E/IBGP Load Balancing at a V-hub for packets whose label corresponds to
   the VPN-IP default route.

   This is an optimization that may be useful under certain circumstances,
   but not others.  The draft should make it clear that this behavior is
   optional.

---

From: Yakov Rekhter <[email-masked]>
Date: Fri, 7 Dec 2012 07:20:51 -0800

Eric,

>      Ingress Replication to instantiate an I-PMSI.

Will do.

>    "may under certain circumstances".

Will do.

>    should have a statement to that effect.

Will do.

>    Could you give an example to show that this restriction is necessary?

Consider the example described in the first 5 paragraphs of section
8.1 of the draft (no Internet connectivity). If PE-3 (which is one
of the V-hubs) would install in its VRF a default route, then what
would be the next hop of that route ?

>    but not others.  The draft should make it clear that this behavior is

I think the draft already does this - from section 4:

   When a multi-homed site is connected to a V-hub and a V-spoke, then
   the V-hub uses the following OPTIONAL procedures to support IBGP/EBGP
                                ^^^^^^^^ 
   load balancing for the site's inbound traffic that has been
   originated by some other V-spoke associated with the V-hub.

Yakov.