The MPLS WG Archive

[Mark Duffy <mduffy@quarrytech.com>]

Under what circumstances would an LSR expect to receive a packet with one 
of the explicit null labels?

Usually, LSRs only receive packets with labels that the LSR has itself 
distributed.  Is that true for these labels?  Presumably not or there would 
have been no need to reserve specific values for them.

So, I presume the idea is that an upstream LSR may apply these labels even 
though they weren't distributed by the downstream.  But under what 
circumstances would this be done?  Is there any reason to apply these 
labels today?  Does anyone have a product that is doing so?  Or were these 
just reserved because they sounded useful at the time and might be used by 
some future application of MPLS.

-- Mark