North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: MAE West
> > > On Mon, Jul 14, 1997 at 07:27:15AM -0700, Owen DeLong wrote: > > > > To true. Would you care to cover the cost of replicating the 400Mbp/s > > [ quoting Bill ] > > > > to build in better reliability? It appears that the owners/operators of > > > > MAE-West are selecting an optimization path based on the assumption that > > > > outages are infrequent and can be quickly corrected. > > > > > Both assumputions have been repeatedly proven false BY MFS. > > > > Indeed. More importantly, Bill, he wasn't suggesting duplicating the > > 400Mbps aggregate, but _splitting_ it; it is, after all, _already_ 4 > > separate links. > > The underlying physical media may be four separate links, but at L2 > it's a single 400Mb/s aggregate. If it were split up into, say two > 200Mb/s aggregates: > > 1) assuming that costs favored intra-building connections, one of the > aggregates would be selected for pruning by the spanning tree > calculation. > > 2) assuming that costs favored having both aggregates in service, if > utilization on the two aggregates was 50% on (call it) A and 100% on B, > the 50% available on A would be wasted. Note that latency would go up, > because spanning tree would have pruned some intra-building link would > have been pruned in order to keep the inter-building link active. > > As the risk of belaboring the obvious, of course there are issues of > reliability and cost-effectiveness, only some of which are technical. > > With respect to economics, for instance: The cost to link two ports in > the same building (better yet, the same room) is essentially the FDDI > cable. The cost to link two ports over a wide area is that of a > DS3/OC3. L2 is not all that different from L3 in that once you've > spent real money on a circuit, you want to get as much use out of it > as you can. > > Stephen I think that the argument here is that there is a real need to have an aggregate 400Mbp/s "pipe" in service as opposed to 2 each 200Mbp/s "pipes". To gain the redunancy that Mr. Dave suggests, would actually encourage the deployment of -two- additional 400Mbp/s channels. Then the economics arguments kick in. -- --bill
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