Subject: Re: Comments on OSPF PC/CE Drafts

From: Acee Lindem <[email-masked]>
Date: Fri, 02 Aug 2002 11:53:50 -0400

Eric - sorry for the delay in responding.

Eric Rosen wrote:

> Acee> Here are my comments on draft-rosen-vpns-ospf-bgp-mpls-04.txt and
> Acee> draft-rosen-ppvpn-ospf2547-area0-00.txt:
> 
> Acee> General:
> 
> Acee> - It would seem that these two drafts could be combined since
> Acee>   draft-rosen-ppvpn-ospf2547-area0-00.txt only contains a couple
> Acee>   paragraphs of unique information. This would also avoid all
> Acee>   references in draft-rosen-vpns-ospf-bgp-mpls-04.txt
> 
> They  were separated  into two  drafts since  the "couple  of  paragraphs of
> unique information" in the area 0 draft  include a new use of one of the LSA
> options bits,  and hence needs discussion  by the OSPF WG.   The other draft
> does not require any new use of any OSPF protocol field.

True. There are a number of draft contending for this OSPF option bit (I
think this only one getting traction as far as implementation and deployment).
However, I think that draft-route-vpns-ospf-bgp-mpls-04.txt should be discussed by
the OSPF WG as well since it has impacts how OSPF does route redistribution.

> 
> Acee>  - The  PE router  doesn't really  have to  be an  ABR. It  is already
> Acee>    "faking" that  VPN redistributed  routes are inter-area  routes. It
> Acee>    can also set its router LSA  B bit accordingly. Oh well, maybe this
> Acee>    could be considered an implementation detail. 
> 
> Would it be more  accurate to say "the PE router acts,  to the CE router, as
> an ABR?"

That's good. Or you might say "The PE router presents itself to the CE router
as an ABR by setting the B bit in it's router LSA."

> 
> Acee> draft-rosen-vpns-ospf-bgp-mpls-04.txt:
> 
> Acee> - Page 4,  second list  item. Since the  VPN routes are  advertised as
> Acee>   type 3  LSAs, I  believe you should  say "inter-area  routes" rather
> Acee>   than "intra-network routes". 
> 
> Intra-network routes is the requirement, inter-area routes is the solution.
> 
> Acee> - Page 11 - Why is auto-configuration a "MUST"? 
> 
> I don't see where it says that.

This text could be interpreted in multiple ways.

4.2.3.2. Creating Sham Links

   Sham links may be manually configured, or they may be auto-
   configured.

   Each VRF that is associated with a PE-CE link on which OSPF is
   running MUST be configurable as to whether auto-configuration of sham
   links to/from that VRF is allowed.  The default MUST be "manual
   configuration".

> 
> Acee> - Page 12, last  paragraph -  Don't you mean  that the PE  should not
> Acee>   install the  route into  the VRF routing  table (since  there should
> Acee>   already be  a BGP  route). This will  insure it doesn't  replace the
> Acee>   route and that it is not redistributed. 
> 
> The route  has to  be in  the VRF  or won't be  used, but  it should  not be
> redistributed via BGP.

Ok - I agree that what is important is preventing redistribution of the route back
into BGP. However,the VRF should already have an iBGP route (if it doesn't, how
can you be sure the VPN backbone has the route?).

New comment:

   Discuss sham link MTU including the fact that the "Interface MTU" field in
   Database Description packets should be set to 0 similar to virtual links.

Thanks,
-- 
Acee