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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: What frame relay switch is causing MCI/Worldcom such grief?
> Yes. Not disagreeing with Sean, which whilst amusing is often unproductive: One of the higher clue arguments in favour of maintaining an L2 mesh (and 'routing' protocol) is that it converges quicker than than L3 as in theory it has less nodes. The normal counter arguments are: 1. that L1 (SONET/SDH) converges quicker still. 2. as MCI/Worldcom may well have aptly demonstrated, L2 routing protocols have their own problems. 3. L3 routing can be hierarchicalized (sp?) and tweaked to converge just as effectively - witness sending your loopback IP's round as next hops in BGP and running an underlying IGP such as OSPF/ISIS/EIGRP which cuts out many (though unfortunately not all) recomputations when the underlying fabric changes. 4. Implementation of L2 heavy protocols on routers is often poor. Witness how long it took Cisco to implement OAM management. So just how long does it take to notice a VC's gone down? A more convincing argument for buying ATM circuits is that they (are) / (used to be) dirt cheap. Recent experience suggests there may be a reason for this. -- Alex Bligh GX Networks (formerly Xara Networks)
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