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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Sonet protection usage
> Are many ISPs taking advantage of SONET APS protection > to provide port or router redundancy on short (metro-area) > circuits? Or is it more typical to get two circuits and > load-share? Or just not bother? I know of a few providers that use inter-router APS to protect against router and ADM trib port (mainly router) failures in the core. The optical network side is protected by BLSR or the like. The optical protection options still seem to be much more cost-effective then simply provisioning parallel (but presumably diverse) links between two locations, not to mention that if some load-balancing schema is employed one needs to consider accommodating additional propagation delay incurred on the less optimal path (an ideal application for CoS & TE, perhaps). Inter-router APS proves itself especially useful on trans-oceanic circuits where simply acquiring additional capacity often isn't a viable option, nor is allowing some really expensive circuit to sit idle for 5 or 10 minutes while a router boots and becomes synchronized. As you can imagine, there are lots of interesting issues with inter-router APS and IGP interaction, most of which seem to cast a considerable shadow on its value when considering network availability and convergence in the event of failures. Intra-router APS is much more appealing, assuming stateful port mirroring is implemented, though it doesn't address the main concern of protecting against router failures. Of course, it's definitely better than simply selecting an alternative, presumably less optimal network path simply because a local router becomes unavailable. -danny
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