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Re: MPLS VPNs or not?

  • From: Thomas P. Brisco
  • Date: Tue Aug 07 08:46:28 2001

	I agree that the article sorts of wanders a bit, but seems to
try and focus on the RFC2547 style of L3VPNs.  While it seems clear that
the author does not have a firm grasp of the topic at hand, do you
honestly look for that in mass media? (I refer you to most publications
your typical "upper management" reads, if so).

	The remarks about RFC2547 is certainly salient.  Most people are
trying to figure out how to deal with BGP routing - why multiply and
obfuscate the problem unnecessarily?  Often I find myself in a position
where I fight to avoid implementing every trade-rag product/technology
du-jour on our network that well-meaning executives read about.  
Particularly ones that seem to be unmanageable (don't go into debugging)
for even your smarter-than-average operator.

	MPLS is falling into the same traps that ATM did.  Remember
those heated discussions of how IP was going to be made obsolete because
everyone was going to be running ATM to everywhere?  As I remember, MPLS
was originally done as a performance enhancement - controlling MPLS
wound up with the side-effect of being able to manage bandwidth.  The
telephone execs that control large portions of the Internet seem
hell-bent on re-implementing what they know and are familiar
with (circuit switching).  Ultimately it fails, because it is a flawed
model for data communications.

	We did not, however, throw out ATM altogether because the
Internet did not become a cross-stitch of ATM SVCs - we do, however, use
it where applicable.  The article fails miserably in that it appears to
condemn MPLS along with the L3VPN model proposed under RFC2547 (and its
successor).  I believe that RFC2547 and its ilk will ultimately collapse
under it's own lumbering weight - however I do remain a fan of MPLS when
used appropriately.  

	In the meantime it remains an irksome fact of life that I have
to continue to "explain" to people that L3VPNs (a la 2547) are a bad
idea to people that don't understand packet switching.  Too bad, I
would've liked to have used this article as part of that ammunition.  

	To date, my best ammunition has been vendor's "seminars" on how
to implement L3VPNs -- when they spend four hours giving "a brief
overview" of it, even the most clueless have to have concerns about the
operational aspects.

							- Tom

On Tue, 7 Aug 2001, Andy Walden wrote:
> On Tue, 7 Aug 2001, Hank Nussbacher wrote:
> >
> > Experts call MPLS bad for 'Net
> >
> >
> >
> I think its pretty well known that multiple routing tables, ala 2547-bis,
> is not scalable. Apparently the author was fed the story and doesn't have
> a clear understanding of the protocols of MPLS. To say MPLS is bad and write
> a story about 2547-bis is a bit short sited. No mention of martini or any
> other vendors besides the two exemplifies this even more.
> andy

--                                                                         --
Thomas P. Brisco                                           [email protected]
Senior Network Architect                                   212-625-7073
Globix Corp.

   Q: A priest, a rabbi, and RFC2547bis are on an airplane.  During
the flight, the plane encounters a storm and crashes.  How many people
   A: Only two.  Everybody knows that RFC2547bis will never fly.