From: Luan Nguyen (luan@netcraftsmen.net)
Date: Wed Sep 17 2008 - 14:28:09 ART
Hi Patrick,
RFC 3031 - MPLS Architecture states in section 3.18 as follow:
3.18. Invalid Incoming Labels
What should an LSR do if it receives a labeled packet with a
particular incoming label, but has no binding for that label? It is
tempting to think that the labels can just be removed, and the packet
forwarded as an unlabeled IP packet. However, in some cases, doing
so could cause a loop. If the upstream LSR thinks the label is bound
to an explicit route, and the downstream LSR doesn't think the label
is bound to anything, and if the hop by hop routing of the unlabeled
IP packet brings the packet back to the upstream LSR, then a loop is
formed.
It is also possible that the label was intended to represent a route
which cannot be inferred from the IP header.
Therefore, when a labeled packet is received with an invalid incoming
label, it MUST be discarded, UNLESS it is determined by some means
(not within the scope of the current document) that forwarding it
unlabeled cannot cause any harm.
-Luan
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Patrick Laidlaw
Sent: Wednesday, September 17, 2008 12:51 PM
To: ccielab@groupstudy.com
Subject: Labels recieved on an LSR
Hello,
I was reading through some questions online and some of there answers when I
came across this questions which I think the answer is wrong but wasn't
sure. If you have a LSR and it recieves a packet with a Label that it does
not have a entry for what does it do? I thought that it strips the Label
and trys to look it up in its FIB but there answer says it drops it.
Could someone enlighten me?
Patrick
Blogs and organic groups at http://www.ccie.net
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