MPLS VPNs or not?

Tue Aug 7 15:35:59 UTC 2001

On Tue, Aug 07, 2001 at 10:18:30AM -0500, Andy Walden wrote:
> On Tue, 7 Aug 2001, Christian Kuhtz wrote:
> 
> > I really wanted to reply... "Logic says you need to check the facts before
> > posting such nonsense." .. but that would be a flame.  Let's try this instead:
> 
> So good of you to show restraint. Your awfully assuming that no one else
> has as much MPLS knowledge and experience as you. Try to maintain the
> conversation without "asserting yourself" at the beginning of each
> response.

There is such a thing as sarcasm. Geez. ;)

> Scaling is looking ahead and considering how it could grow. Your going to
> have to do *something* on each PE, I think signalling a tunnel and being
> done with it is better.

If all you're building is a small amount of point to point VPNs, sure.. At a
large number of VPNs and complex VPN topologies (better than p2p), I think
there are some very distinct advantages.

> > So, you're going to try to tell us next that n^2 tunnels scale better
> > and are less of an operational nightmare at scale than the connectivity
> > provided inside of an MPLS-VPN?
> 
> I think so. I'm sure either will work in its element. Obviously you don't
> agree, we can leave it at that.

I think the point I'm trying to make is this.  People keep saying that 
RFC2547(bis) implementations won't scale, when the funny part is that they 
really don't become terribly useful unless used at scale.  Many of the
advantages aren't realized at small scale.

And, I'd rather have a thousand prefixes than a thousand tunnels across my 
network.  But, that's also with the premise that I'm working on building a
very large, complex customer topology VPN infrastructure from the outset.

But, the point you're hitting on is absolutely appropriate.  MPLS-VPNs aren't
a solution for everything, and neither are tunnels.  It very much depends on
your customer's needs, on your topology etc.  Global bashing of either is 
inappropriate.  

And at very large SP scale, I think the overhead and inflexibility of tunnels 
isn't acceptable.  If that's all I want, I might just as well buy tons of 
FR/ATM.

Tunnels will always happen.  It's something any customer can do on their own.
In my opinion, if what they're looking for is a large scale managed VPN, the 
options of topology & traffic management in MPLS-VPNs outweigh those of 
tunnels.

> > Have you ever actually used the code yourself?
>
> "the code"? Assuming you mean have I setup L3 VPNs, yes, but you can
> refer to my first comment.

Please don't be ridiculous.  The point was that it is incomprehensible to
me how some of the statements are made about MPLS-VPNs if you've actually 
touched the stuff and worked with it.  All too many people comment on this 
stuff with mere book knowledge.  That was the point, and no more.

Cheers,
Chris

-- 
Christian Kuhtz <ck at arch.bellsouth.net> -wk, <ck at gnu.org> -hm
Sr. Architect, Engineering & Architecture, BellSouth.net, Atlanta, GA, U.S.
"I speak for myself only."