The MPLS WG Archive

["Sumit Garg" <garg@torrentnet.com>]

> I have some questions on RFC 3031, MPLS Architecture.
>
> Section 3.12 says
>     "If the FTN maps a particular label to a set of NHLFEs that
> contains
>     more than one element, exactly one element of the set must be
> chosen
>     before the packet is forwarded.  The procedures for choosing
> an
>     element from the set are beyond the scope of this
> document.Having
>     the FTN map a label to a set containing more than one NHLFE
> may be
>     useful if, e.g., it is desired to do load balancing over
> multiple
>     equal-cost paths."
>
>
> 1. Here actually we should be talking about the FEC to  NHLFE
> mapping rather than Label to NHLFE mapping. Isn't that correct?


FTN = FEC to NHLFE
ILM = Incoming Label Map (Label to NHLFE)

Yes, you are correct


> 2. Have these procedures to identify one of the multiple entries
> been defined as of now? If yes, wonder if I could get some
> pointers for them.


No, nothing has been standardised (atleast I'm not aware).  This where
vendor value add comes in.


> 3. Are there other scenarios also wherein it's useful to map an
> FEC to multiple NHLFEs?


Fast re-route/ backup LSPs.  Specialized handling where one may want to
send packets belonging to a special category (incoming i/f, src IP, dest
port or other such information) on a special LSP i.e. the FEC is now
more than just the dest IP, it is augmented with more information.


Cheers
-- Sumit Garg