LC comments on considerations extranet section

[Eric Rosen <erosen at cisco.com>]

The section on extranet 3.3.6 is not accurate.

It suggests  that it  is not  known how extranet  could be  achieved without
using BGP-based C-multicast routing.  This is odd considering (a) a solution
providing this feature has been shipping  for years, and (b) the solution is
written up in draft-rosen-l3vpn-mvpn-mspmsi-02.txt.

It  also suggests  that all  it takes  to do  extranet with  BGP C-multicast
routing  is to  reuse the  "already defined  and well  understood  BGP route
target import/export  semantics".  In  fact, this is  not true.   To support
extranet you also  have to know which C-streams in which  PMSIs are the ones
you need to receive.  In the  PIM control plane, you make this determination
by associating each PMSI with a particular PIM interface.  I don't think the
corresponding functionality is specified for the BGP control plane.

I think it  is premature to make a recommendation  based upon which extranet
scheme  works best  until we  have  both extranet  schemes written  up in  a
standards track document.