Subject: BGP routes with label information

From: "Krishnan, Vijay G." <[email-masked]>
Date: Mon, 9 Dec 2002 11:01:45 -0500

Hi,

I have a question regarding multiple label advertisements for BGP route
(RFC-3107).

Suppose a BGP speaker receives in a single update message, a destination
prefix (p) with a nexthop (n) and multiple mpls labels (L1, L2 and L3). In
the next update, it receives prefix (p) and nexthop (n) but a different
label (L4). 

Will (p,n,L4) replace {(p,n,L1), (p,n,L2) and (p,n,L3)}. 
Or 
Will the new one be added to get {(p,n,L1), (p,n,L2), (p,n,L3) and
(p,n,L4)}. 

thanks
Vijay

---

From: "Krishnan, Vijay G." <[email-masked]>
Date: Mon, 9 Dec 2002 13:14:52 -0500

Sri,

I am sending my reply to IDR as well.

Should the label information be considered part of NLRI or an attribute.

According to section 3 of RFC3107, label is part of an attribute.
   "A BGP speaker can withdraw a previously advertised route (as well as
   the binding between this route and a label) by either (a) advertising
   a new route (and a label) with the same NLRI as the previously
   advertised route, or (b) listing the NLRI of the previously
   advertised route in the Withdrawn Routes field of an Update message.
   The label information carried (as part of NLRI) in the Withdrawn
   Routes field should be set to 0x800000."

In section 4, it says that we can withdraw a particular label (like an NLRI)
   "In the case where a BGP speaker advertises multiple routes to a
   destination, if a route is withdrawn, and a label(s) is specified at
   the time of withdrawal, only the corresponding route with the
   corresponding label is withdrawn."

So if we need to change the label mapping should we send the new set of
labels or withdraw it before sending the new update.

thanks
Vijay

-----Original Message-----
From: PamSri [mailto:[email-masked]]
Sent: Monday, December 09, 2002 11:48 AM
To: Krishnan, Vijay G.
Subject: Re: BGP routes with label information

Vijay ,
      Can you provide some more info on scenario which
causes 2 updates to be sent out back with different
label info ? Normally if you encounter a situation
whereby you send 2 different sets of path attribs
separately then you overwrite the path attribs with
the latest update. 

sri

--- "Krishnan, Vijay G."
> Will the new one be added to get {(p,n,L1),

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