North American Network Operators Group

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Re: MPLS VPNs or not?

  • From: Vijay Gill
  • Date: Tue Aug 07 11:54:01 2001

--On Tuesday, August 07, 2001 08:29 -0700 Robert Raszuk <[email protected]> wrote:


I am not defending IOS bugs or any particular implementation - I am
defending the architecture.


the point here being that software is a complex beast that is fairly hard to get right and often has very subtle failure modes. The interactions between various small bugs in subsystems often result in catastrophic failures when they interact as a part of a much larger whole. The architecture is fine, and in fact like all Powered By PowerPoint (tm) architectures, looks good in labs and papers, runs extremely well on slide projectors and will probably run fine in the real world for a while too.

However, there are real life operations folks who have to run these things on large networks with lots of interactions among various components that are hard to duplicate in a lab setting (else we'd have bug free code on FCS).

There was no singling out of IOS or any other implementation, I was just pointing out two fairly recent failure modes in code paths that has been exercised for years and deal with a "well known" RIB and adjacency maintenance issues. It is entirely possible that there are no bugs in current implementations; I just won't bet my day job on that possibility.

> Besides for those individuals who have problems with  maintaining a
> sinlge RIB with IGP routes I would higly advise a caution in deploying
> an mpls-vpn service or even touching the routers :).
That was uncalled for. We do have problems maintaining a single RIB with IGP routes sometimes, mostly they are due to buggy implementations.