From: David Clark (dclark@ccbootcamp.com)
Date: Wed Sep 17 2008 - 17:34:14 ART
Just adding to Scott's note. A LSR will definitely drop a packet with a
unknown label.
In normal operation, an LSR should receive only a labeled packet with a label
at the top of the stack that is known to the LSR, because the LSR should have
previously advertised that label. However, it is possible for something to go
wrong in the MPLS network and the LSR to start receiving labeled packets with
a top label that the LSR does not find in its LFIB. In such circumstances The
LSR will drop the packet, as the LSR did not assign the top label, and has no
knowledge what type of packet is behind the stack.
________________________________
From: nobody@groupstudy.com on behalf of Scott Vermillion
Sent: Wed 9/17/2008 12:59 PM
To: 'Patrick Laidlaw'; ccielab@groupstudy.com
Subject: RE: Labels recieved on an LSR
Hi Patrick,
I laid my SP studies aside some time back but I'm relatively confident that
the answer is necessarily "drop." The problem with trying to forward that
unlabeled/mislabeled traffic is that the MPLS core by design shouldn't have
the intelligence in any of the FIBs to accurately forward it. Consider that
there might be 100 customer VPNs at the edge all with overlapping RFC 1918
address space sourcing traffic towards the core. Or that the payload might
not even be L3...
Regards,
Scott
-----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 <http://www.ccie.net/>
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