[mpls] how does it work if ....

Loa Andersson <loa@pi.nu> Wed, 17 March 2021 14:18 UTC

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To: "mpls@ietf.org" <mpls@ietf.org>, Kireeti Kompella <kireeti.kompella@gmail.com>
From: Loa Andersson <loa@pi.nu>
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Date: Wed, 17 Mar 2021 22:18:25 +0800
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Subject: [mpls] how does it work if ....
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Kireeti,

I'm looking at your slides from the joint meeting, in particular slide 
#3, where you say at thye bottom:

   "Corollary: such labels MUST NOT reach the top of stack (by popping
    labels above them)"

How is that backwards compatible.

If you  have an old LSR, that don't know to look at the bSPL or eSPL 
underneath the top label. I assume that the top label will be swapped 
and the packet forwarded.

What is the pen-ultimate LSR is "old" and just pop the top label, how 
can the PE sort this out?

/Loa
-- 

Loa Andersson                        email: loa@pi.nu
Senior MPLS Expert                          loa.pi.nu@gmail.com
Bronze Dragon Consulting             phone: +46 739 81 21 64