Re: [Isis-wg] Re: IS-IS as PE/CE routing protocol in BGP/MPLS/VPN

On Thursday 15 May 2003 13:44, Manav Bhatia wrote:
> Lidefeng,
> Just a general observation:
> 
> - Whenever a PE router receives a MP-BGP UPDATE, it must execute the BGP
> Decision Process to decide the best path to the prefix contained in the
> UPDATE. When this decision process completes, the *best* route is passed
> onto the IS-IS selection process for import into any relevant VRFs. Because
> multiple UPDATEs for the same prefix might be received, and because IS-IS
> has its own selection process for differing metric types, the BGP Decision
> Process IMHO should be modified to prefer routes with internal metrics over
> the routes with external metrics. The Decision process will be based on the
> ISIS metric type that will be conveyed within the IS-IS Route Type Extended
> Community Attribute that accompanies the ISIS VPN-IPv4 route.

If I understand correctly the concept of the sham-link, the 
PE will receive a mp-bgp route containing the other end of 
the sham-link and the extComm describing it. This route need 
to be the best among other (possible) mp-bgp routes (with 
same RD) for the same prefix. If such route is best, then you 
won't really import it into the vrf but rather you will "use 
it" in order to add a (fake) adjacency into the isis lsp the 
PE will originate. Then you run spf as part of the isis 
instance running in the vrf and compute your routes. After 
spf computation you'll find that the prefixes of the remote 
site are reachable through the sham link (according to the 
metric of your links of course). So I don't believe you 
really need to change the bgp selection process.

Btw, I don't see any reference to TLVs 22 and 135 in the 
draft...

s.

> 
> There seems to be no mention of this in the draft.
> 
> - Is there a reason why you're not sending any metrics (wide/narrow) info
> in the extended community?
> 
> Regards,
> Manav
> 
> ----- Original Message ----- 
> From: "lidefeng" <[email protected]>
> To: <[email protected]>
> Cc: <[email protected]>; <[email protected]>
> Sent: Tuesday, May 13, 2003 10:19 AM
> Subject: [Isis-wg] A new draft,IS-IS as PE/CE routing protocol in
> BGP/MPLS/VPN
> 
> 
> > Hi,all,
> >
> > In deploying BGP/MPLS VPN,there are sites that CE run IS-IS protocol with
> > PE,and the corresponding customer is reluctant to change the routing
> > protocol they used in the sites,to accomodate this situation, it is
> better
> > to run isis protocol between PE and CE,however,ther isn't any draft to
> > specify the scenario in the BGP MPLS VPN. This draft addresses this
> > scenario,the abstract is as following:
> >
> >  IS-IS protocol, which is specified in [1], can be used as IGP between
> >    the Customer Edge (CE) router and the Provider Edge (PE) router in
> >    BGP/MPLS VPNs as per [1]. This document provides a detailed solution
> >    for IS-IS working as PE/CE Protocol in VPN services specified in [1].
> >
> 
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