The MPLS WG Archive

["David Allan" <dallan@nortelnetworks.com>]

I meant painful from the point of view of the number of places it could appear in the MIBs (which might not actually be that bad and looks like it could be confined to the XCTable).  I'd assume the most useful definition would be configurable per LSP with a default LSR setting. (per LSP default is default specified for the LSR).

 

cheers

Dave.

-----Original Message-----
From: Thomas Nadeau [mailto:tnadeau@cisco.com]
Sent: Monday, November 26, 2001 3:00 PM
To: Allan, David [CAR:NS00:EXCH]
Cc: mpls
Subject: RE: MIBs and TTL

Pipe or uniform is the terminology adopted in the MPLS diffserv draft and carried forward into
http://www.ietf.org/internet-drafts/draft-agarwal-mpls-ttl-01.txt

        Sorry, from the original context, I wasn't sure.

The short story is:
- for uniform model TTL is independent of MPLS level. You copy TTL values up and down the stack as you push and pop.
- for pipe model, TTL is unique to each MPLS level.
So configuring this looks painful (get it from incoming label before x-connect entry, or get it from incoming IP payload, or set it to fixed value at ingress) :-(.

        It looks painful, but is flexible as to support different implementations.

As to how to handle non-TTL capable links, an unsigned object added to InterfaceConfEntry (InterfaceTTLDec?) with a default value of 1 should be all that is required. The only wrinkle being that I don't fully grok pop and swap to be sure that a non-ttl link label under the top label would work correctly.

        This is certainly an option.

        --Tom
        

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