Subject: Label operations question

From: "Nepple, Bruce" <[email-masked]>
Date: Wed, 8 Aug 2001 13:47:22 -0700

I have some questions about label operations given real
world networks.  If this is not the correct forum for this
question, please let me know.

I am trying to classify the label operations that can occur 
within a single LSR given real world networks.  In addition, 
I would like to distinguish between operations on unlabeled 
packets (edge) and already-labeled packets (non-edge).  

For example, an unlabeled packet entering an mpls-vpn domain and
immediately tunneling requires 3 label push operations. 
(VPN,FAR_END,TUNNEL). (I think this is the maximum operation
for an unlabeled packet in a pure mpls domain)

As another example:
A labeled packet being routed into a tunnel requires a swap
and a push. (FAR_END, TUNNEL) (Is this the maximum for a 
labeled packet?)

The main thrust of this question is to try and uncover
more complex operations that might be neccessary. (maybe
there should be a prize given for "discovering" the most 
complex set of real world label operations within a 
single LSR)

Also, I am wondering if Router_Alert labels are ever
used and if so, how widely. What sort of additional actions 
are generally taken as a result of a router alert label? 
Router_Alert labels require an additional operation 
in that one must operate on the second label, possibly 
popping two labels, or even popping, swapping and pushing.

Thank you for you time

Bruce Nepple
Network Elements, Inc