The MPLS WG Archive

["David Allan" <dallan@nortelnetworks.com>]

Hi Eric:

> David> If  you want  to offer  a common  label for  all FECs  
> to a  peer 
> David> for whatever reason, it does not need to be a reserved label.
> 
> Using a reserved label  eliminates the need to look up the  
> label in a large table; instead  you can spend  your time 
> looking  up the label  (or address) beneath it. 

OK, you want to come as close to PHP as possible via some extra gates... ;-)


As the recevier controls the labels it hands out, you could pick any value
and optimize the hell out of it or for that matter make any implementation
choice. You don't need an explicit reserved value except for historical
reasons. 
 
<snipped>

> David> We  seem to be  going down  the road  where the  first 
> nybble  of 
> David> the payload is  becoming significant and permits v4/v6 
>  and other 
> David> traffic to  be  distinguished without  requiring  unique  
> David> reserved labels  to identify the traffic.
> 
> If you're  suggesting that we only need  one value of "IP  
> explicit null", I think that is worth considering. 

Yes, I'd like to reduce the number of ways of doing the same thing.
Presumably any good implementation not only handles the label, but also
checks that the payload is a real v4 or v6 packet.  IMO we can condense two
labels into one, or as noted above potentially eliminate them entirely.

cheers
Dave