The MPLS WG Archive

[Shahram Davari <Shahram_Davari@pmc-sierra.com>]

Hi James,

 One of the reasons that per-interface label spaces 
> were introduced is
> so that ATM and FR interfaces would only allocated label 
> values for LSPs that
> it was going to use.  Thus allowing them to stretch there 
> limited number of
> VCs or DLCIs farther.  By doing as you suggest your "wasting" 
> label values.
>

ATM and FR don't need per-platform label space, because there is no hierarchy in ATM/FR.
 
> When allocating an N level label (where N is > 1) it should 
> be allocated from
> the same label space as all of the N-1 labels that may 
> possible tunnel this
> label.  When N = 1, the value should be allocated from the label space
> associated with the set of possible interfaces that will receive this
> label. 
> This assumes that any service allocating N level labels MUST 
> know the set of
> LSPs in which it's label values will have meaning.  When N = 
> 1 the service
> MUST know what set of interfaces its label values will have meaning.
> 

All levels of hierarchy use the same label space. There is no notion of a separate label space per hiererchy level.

Regards,
-Shahram