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Re: Traffic locality and other questions
Sean Donelan <[email protected]> writes: > I have some questions whether it is better to aggregate traffic into > a single huge flow, or if it is better to have lots of > smaller paths. Ah, good question. What seems to scale better is aggregating things into large buckets which are switched together rather than merely filtering lots of small individually-switched buckets of data through single pieces of equipment. There are some assumptions driving this. Firstly, it is easier to move large numbers of symbols per second than it is to make large numbers of switching decisions. Secondly, it is possible to build a hierarchical routing scheme that can take advantage of aggregation opportunities to put similar traffic into big buckets along particular path segments. Thirdly, there are economies of scale which can be exploited when one uses large data pipes that reduce the cost of moving traffic intelligently. If all of these assumptions prove to be invalid, and in particular if it is cheaper to build equipment which are better at switching very small amounts of data across many diverse physical paths, if a routing scheme that can fully exploit this can be developed, and if it is more economical to use many small pipes than a few large pipes, then obviously one would be better off not aggregating traffic, and perhaps even deaggregating it and its complementary reachability information. > BGP isn't very good at showing 'other' transit paths to > networks. BGP is a distance vector protocol and not a map-exchanging protocol. You cannot build a completely accurate map of the Internet from a subset of BGP distance vectors. BGP routers will also only announce their paths of choice to their neighbours, and therefore any other paths they may know will be hidden. > What I find interesting is the rankings of traffic flows I see don't > match with what the pundits rank as the largest network providers. I > don't know what that means though. I suppose it depends on what people describe when they say "largest". Sean.