The MPLS WG Archive

[Abhijit <gabhijit@ee.iitb.ernet.in>]

Hi all

I have a doubt abt the implicit NULL label. 

The draft says 

========================================================================
 value of 3 represents the "Implicit NULL Label".
                 This is a label that an LSR may assign and distribute,
                 but which never actually appears in the encapsulation.
                 When an LSR would otherwise replace the label at the
                 top of the stack with a new label, but the new label is
                 "Implicit NULL", the LSR will pop the stack instead of
                 doing the replacement.  Although this value may never
                 appear in the encapsulation, it needs to be specified          
		 in the Label Distribution Protocol, so a value is
                 reserved.                          

=======================================================================

I didn't get the exact use of the Implicit Null Label. 

1. What I can infer is that this binding could be given by Egress LSR to
its Upstream so that when the outgoing label value is 3 as specified here,
the Penultimate LSR will Pop the Label entry. 

Is this correct? 

Thanks and Regards 

-abhijit