Re: [PWE3] PWE3 question

[Eric Rosen <erosen@cisco.com>]

John> Protocols should not dictate network architecture.

John> The choice of whether an operator desires to use a separate
John> label inside the network for each psuedo-wire, or to use a
John> label stack to improve scaling inside the network is a
John> network design issue.

John> It is not a protocol design issue.

It is  possible to use  a two-layer stack  and still design a  network which
lays  down state  for each  PW in  the core  routers, and  hence is  just as
unscalable  as an ATM  network.  The  protocol design  does not  dictate the
network design. 

The primary  issue is, do we really  need a protocol which  is optimized for
unscalable network designs (uhh, I mean for network designs in which each PW
has state in the core routers)?  Anyone who thinks so should make a proposal
and should  make it clear why  the use of one  rather than two  labels is so
important.

The secondary issue is whether  any particular protocol should be considered
to be universally mandatory (for conforming products to provide), or whether
each can just be implemented within its own scope of applicability.

There is also an issue as to whether there is some realistic set of service
characteristics which  cannot be provided  unless the core  routers maintain
state per PW.   It will be hard  to get consensus on a  "one label" protocol
unless one  can first get  consensus on this.   Since the use of  two labels
does  not rule  out the  creation of  per-pseudowire state  within  the core
routers, I'm not sure why folks even want to fight this battle. 









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