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North American Network Operators Group

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  • From: Martin, Christian
  • Date: Wed Sep 04 08:58:45 2002

>BGP is not a bug-free protocol.
>BGP is the easiest protocol to *debug* when the problem shows up.
>BGP does not help to accidently affect *unaffected* paths when 
>a problem shows up.

While there is a recursion issue in the BGP<->IGP scenario, BGP would be
just as "broke" if the only path between two nodes (and whatever nodes are
behind them) had their BGP session removed.  Misconfigurations do not imply
bad network designs.  Bugs are bugs (whether they be OSPF or ISIS or BGP).
We have seen RSVP/SNMP/NTP/.*P bugs break routers.

I also would think that it is a bit of a stretch to criticize the design of
the largest networks in the world, which, were it not for bugs here and
there, are running just fine.

Further, and I think this is what is troubling people here, is how, without
IBGP mesh reduction mechanisms, you could build a non-fully meshed network
without an IGP and static routes?  The only way this is possible is via a
combination of meshing, confeds, and route-reflectors, the latter two which
are busted by design.  If you are building fully meshed networks, then they
are small.

And one last comment - ISIS is the easiest protocol to troubleshoot IMO.
Even RIP is harder because of all the silly holddowns and poison-reverses,
etc.  BGP is pretty straightforward as well, but there is a lot in the sauce
that you need to know from vendor to vendor, etc.  With ISIS, you have one
DB (or 2), 1 LSP per router, 1 decision  point.

Finally, you seem to have a problem with dependencies and recursion,
philosophically.  This surprises me from someone who I know writes code.  Do
you not use functions?  Pointers?  What you have said is that a program that
breaks because one function relied on another (that failed) is a broken

My .02

>It looks like everyone forgot the reason for this discussion 
>to begin with. It is the outage caused by a mistake on a 
>single router that affected parts of the network that were 
>*NOT* affected by the original mess.
>Please not that this discussion tends to get restarted 
>whenever we have a real OSPF (or ISIS) caused mess.

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