Re: Fwd: Re: Why martini over kompella

Irwin,

I'd like to get more information on this topic. Cheers... Tarek

>From: Irwin Lazar

>To: mpls-ops@mplsrc.com

>Subject: [MPLS-OPS]: Fwd: Re: Why martini over kompella

>Date: Wed, 15 May 2002 10:00:21 -0400

>FYI - From Kireeti Kompella himself:

>-------------

>>If one of the Kompellas may be allowed to answer ...

>>Several of you got it right (nearly), which is very comforting.

>>Mark's point re building p2p circuits vs. building VPNs is a good

>>high-level answer.

>>As Robert indicated, the bottom line is, do you want to signal your

>>VPNs with targeted LDP or with BGP? Many vendors think BGP is

>>really

>>hard to implement and LDP is a breeze, and thus go for implementing

>>martini. One can question the validity of this argument, but the

>>results are what you see.

>>However, there are a few vendors besides the company I work for who

>>aren't afraid of implementing BGP-based solutions; one of them

>>recently demonstrated interoperability with Juniper.

>>So, why BGP instead of LDP? BGP does auto-discovery; LDP doesn't.

>>This makes a huge difference to the task of provisioning VPNs.

>>BGP is also better suited to building largish VPNs -- with LDP, the

>>protocol state maintained in the network, the number of targeted

>>LDP

>>sessions, etc. all get pretty large pretty quickly [O(N**2)]. With

>>BGP, the protocol state in the network is O(N); and one can use

>>route

>>reflectors and/or confeds to keep the number of sessions at O(N).

>>Finally, if one is interested in building inter-AS/inter-provider

>>VPNs, BGP is a clear winner.

>>(Yes, I've heard people propose LDP route reflectors; also to endow

>>LDP

>>with communities. What next? eLDP and iLDP? LDP path attributes?)

>>Finally, if "network convergence" isn't just a pipe dream, and one

>>was to offer both 2547 VPNs and L2 VPNs, it makes sense to use one

>>methodology -- and BGP-based L2 VPNs are fairly close to 2547 VPNs,

>>simplifying provisioning, monitoring and maintenance.

>>Christopher is probably right that "over 80% of todays L2 networks

>>that use frame relay or ATM connections, the SP provided

>>connectivity

>>is not full mesh", but from what I've heard, this is primarily

>>because

>>it is so expensive to provision a full mesh ATM or FR VPN. BGP

>>makes provisioning a full mesh simple, and a hub-and-spoke almost

>>as simple. So, the real question is, what do VPN customers want?

>>Or does that not matter any more?

>>One of the SPs that has deployed BGP based L2 VPNs offers their

>>customers full mesh VPNs. The customer is then free to define

>>their

>>own topology on top of this. What this means is that the customer

>>can change their VPN topology without any changes on the part of

>>the SP -- pretty neat feature at a fairly low cost!

>>To respond to Daniel's comment:

>>"To answer the original question - vendors have chosen to implement

>> Martini because it's more or less finished and everyone can agree

>>on

>> what Martini VPN is and you get cross-vendor interoperability.

>> Multipoint VPNs are still in quite a bit of flus. In fact, if

>>you

>> look at the web page for the ppvpn group, you'll see that none of

>>the

>> various "Kompella drafts" are current."

>>it's worthwhile considering what the "finished" and "current"

>>states

>>of a draft mean. The martini drafts are very much in a state of

>>flux --

>>they were to be published as Informational RFCs, then as Proposed

>>Standards, then as Experimental. Finally, they were pulled out of

>>the

>>standards process, and are again *individual submissions* (i.e.,

>>not

>>WG documents in any WG). What Daniel probably meant is that the

>>drafts' *content* is stable, which is true.

>>The kompella drafts are current Internet Drafts, but are not PPVPN

>>WG

>>documents (nor any other WG documents). The contents have been

>>stable for a while now, and there are interoperable

>>implementations,

>>but not nearly as many as for martini.

>>Hope that helps,

>>Kireeti.

>-------

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Re: Fwd: Re: Why martini over kompella