The MPLS WG Archive

[Jack Brennen <John.Brennen@marconi.com>]

What action should an LSR take when it receives an LDP Label Request
for a FEC which is prohibited from label switching by a policy rule?

Here are my alternatives:

   - Return a Notification, with an error code other than one
     of those listed in RFC 3036.  This would be my preferred
     mode of operation, but I'd prefer a standardized error
     code rather than inventing my own.

   - Return a Notification, with an error code listed in RFC 3036.
     Possibilities include "No Route" or "Unknown FEC", but those
     are somewhat misleading; in the case of "No Route", the
     upstream LSR may retry the Label Request indefinitely, which
     is an undesirable result.

   - Give an implicit NULL label.  This may be a bad option;
     implicit NULL doesn't exist on ATM, for example, and the
     upstream ATM LSR may do a poor job of receiving such a
     label (See RFC 3031, 4.1.5).

   - Give a "fake" label (one which drops all traffic) or an
     implicit NULL label, and then immediately Withdraw it.
     This seems too contrived and silly to be a serious alternative.

   - Ignore the Label Request.  Not a good solution for obvious
     reasons.

Any advice?  Are there any drafts which address this issue?

   Jack