RE: [RRG] Long term clean-slate only for the RRG?

["Tony Li" <tony.li@tony.li>]

Hi Bill, 

|Have I grossly misunderstood how MPLS works? What's the story?


You have one model of how MPLS operates.  However, another very common
deployment of MPLS is for TE purposes.  In this type of scenario, routing
protocols are deployed natively and their information is used for path
computation.  Note that path computation need not be (and frequently isn't)
simply just 'best effort'.  A signaling protocol is then used to go
hop-by-hop along the computed path and establish explicit state for each
LSP.  Again, this is significantly different than 'normal' tunneling (e.g.,
GRE) where only the endpoints hold tunnel state.

Now, obviously MPLS does meet the 'encap' requirement, and for any tunnel to
be effective, there is some mapping that directs traffic down the tunnel, so
to be liberal, one could say that 'map-and-encap' is fulfilled.

However, in a more strict interpretation, I would claim that map-and-encap
architectures require a global mapping function that maps destination
addresses to tunneled next hops and creates two namespaces: one inside the
tunneled virtual topology and one underneath the tunnels.

MPLS, when used in a TE scenario, is more general than that in that it does
not create a separate namespace and it need not map soley on destination
addresses.

As always, this is a subtle semantic distinction, and the result really
depends on your definition of 'map-and-encap'.  While I love arguing
semantics, I greatly prefer to simply select a common agreed on definition,
make it semantically clear, and then move on.  If further concepts need
clarification, adding to the terminology is typically not a significant
issue.

Regards,
Tony


--
to unsubscribe send a message to rrg-request@psg.com with the
word 'unsubscribe' in a single line as the message text body.
archive: <http://psg.com/lists/rrg/> & ftp://psg.com/pub/lists/rrg