Re: What is the limit? (was RE: multi-homing fixes)
Leo - Draw two curves, the first y=x/2, the second y=x^2 Move the value of x for y=1 for the first curve left by 2, 5 or 10 and it will still be surpassed by the second curve. You will even see this for a second curve of y=x*2 or y=x. The global routing table size HAS grown exponentially in the past. Rationalize it any way you want, blame whatever you like, but there is no known way to construct a router that can handle that kind of growth in anything but a short term, and the trend for the components in the router growth curve is simply not going to increase to a long term superlinear rate. A 10x system performance boost today just moves the x point for y=1 of fundamental curve claimed by Moore's Law to the left a few notches. Or are you claiming that routing equipment will have a fundamentally different, and larger, growth curve than other computing systems? (I think there is a basis for claiming that there are some reasons which would support a _shallower_ growth curve for routing equipment, actually). In short: are you claiming that the caeteris paribus assumption in comparing Moore's Law to global routing table size is clearly false? It would be nice to see even a partial proof of such a claim.
From anyone.
Sean. (today's insult-free posting)
On Wed, Aug 29, 2001 at 08:05:51AM -0700, Sean M. Doran wrote:
The global routing table size HAS grown exponentially in the past. Rationalize it any way you want, blame whatever you like, but there is no known way to construct a router that can handle that kind of growth in anything but a short term, and the trend for the components in the router growth curve is simply not going to increase to a long term superlinear rate.
Ah, but exponential growth can't happen forever, and we can build a system to handle the largest possible Internet (with v4, anyway). If you had a router that could handle 2^32 prefixes, it will handle the IPv4 Internet. Forever. The whole growth curve argument is gone. The global routing table cannot grow exponentially forever. There are upper bounds all around, including but not limited to the number of addresses. Over time the growth curve must change to be linear, and then logarithmic.. For reference, there are approximately 10^80 electrons in the universe (per several physics sources I found on the net). At doubling every year that gives us an absolute upper bound of 265 years, if every route could be stored in a single electron. Figuring we can probably only do one per atom, and averaging 4 electrons per atom (is that high or low?) that gives us 106 years. We're 30 years into this IP thing, roughly, so we're 1/3 of the way there. Not to minimze the short term issue, but to hand wave and say "it's exponential and we'll never get ahead of it" is crap. It won't be forever, so let's get ahead of it. -- Leo Bicknell - bicknell@ufp.org Systems Engineer - Internetworking Engineer - CCIE 3440 Read TMBG List - tmbg-list-request@tmbg.org, www.tmbg.org
Draw two curves, the first y=x/2, the second y=x^2 Move the value of x for y=1 for the first curve left by 2, 5 or 10 and it will still be surpassed by the second curve. You will even see this for a second curve of y=x*2 or y=x.
[deleted]
In short: are you claiming that the caeteris paribus assumption in comparing Moore's Law to global routing table size is clearly false? It would be nice to see even a partial proof of such a claim. From anyone.
sorry to get pedantic here, but i'd be happy to. when there is a fixed, finite, upper bound on the curve's growth (because, as you well know, there is a fixed, finite, upper bound on the number of prefixes that could be announced [say, in ipv4]), it may assume exponential behavior at the beginning of its growth, but it won't continue to be exponential until it reaches its maximum. what happens is that there will be an inflection point, and a tailing off of the approach to the limit point. which is quite easy to get ahead of technologically. the difference with moore's law is that the fixed, finite, upper bound on the route table curve's growth is already technologically FEASIBLE to handle, in it's ENTIRETY. so your example functions above just don't cut it. there is no infinite amount of prefix space that we need to worry about. it's very finite, and currently (ipv4) not even terribly large (if people allowed even /24's instead of /19's (say), and EVERYBODY split ALL of their address space down to /24 announcements, we'd still only have on the order of 2^24 ~ 10^8 prefixes, which is quite reasonable). i mean, is anyone really trying to argue that it's difficult computationally to update 10^8 entries at the rate that BGP updates occur? arguments along the lines of, "nobody should do anything until we can guarantee that we can handle multihoming every host on the net" are really just inappropriate rationales for enforcing restrictive filtering policies. i'll say it again: a /24 content provider might need to multihome for good reachability to all of its clients, whereas a /16 provider might need to multihome for reachability to remote locations (along with reliability), and the /24 might very likely be attached to a much larger sized pipe than the /16. prefix length != need for multihoming. so filtering on it is a pretty ham-handed way to keep prefix table size down. s.
participants (3)
-
Leo Bicknell -
smd＠clock.org -
steve uurtamo