|
North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Selfish routing
> > [email protected] wrote: > > Having capacity *always* makes a network better. > > True enough; given massive over-capacity, you'll have a hard time > finding any congestion. (Of course, you also won't find optimality > without applying some kind of measurement.) But curiously, adding some > incremental capacity to a network can, under some conditions, actually > make it worse! Oh, rubbish. When you are moving OC-12 worth of traffic you don't add new DS3 backbone links. When you are moving OC-48 worth of traffic, you don't add OC-3s i.e. any non-braindead network architect/engineer will see it. Of course, no one said that those getting out of Chub or CIT that companies hire have that ability, in which case the issue is caused by people with wrong set skill being hired to do the wrong job. Of course, the sales people of yet another equipment vendor trying to sell yet another useless technology that claims in a yet another way eliminate the need of people with a clue on staff in exchange for major $$$ do not want to admit it. > As Jeffrey observed, the assumptions in the model don't map well to the > Internet we all know and love, but results like Braess' paradox come up > again and again. If you want an optimal network, you can: > 1/ sit in the middle and play at being the God of TE > 2/ have the various actors optimize "selfishly" > 3/ count hops and assume that's close enough > (Oh, and if you're into that sort of thing, I suppose you can try > dropping some packets to speed things up.) Oh how about "fire those who are ordering wrong size of interconnects, order right sized interconnects, count the moneys that you did not waste". > And I wouldn't evangelize that faith, as stated. I do happen to believe > in "special" (or if you prefer, "selfish") technology that measures > problems in networks I do not control, and if they can be avoided (say by > using a different network or a different injection point), avoid them. In > practice, that extra "if" doesn't change the equation much, since: So, the brilliant technology costs money but does not provide excellent results under all circumstances? Simply not making stupid mistakes designing the network *already* achieves exactly the same result for no additional cost. Alex
|