North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical RE: Is anyone actually USING IP QoS?
On Wed, 19 May 1999, Andrew Odlyzko wrote: > > Before throwing in my two cents' worth of comments, let me state that > I used to believe in the need for QoS and usage-sensitive pricing > (which go hand in hand).However, extensive studies of the economics > of data networks and usage patterns have changed my mind, at least > when it comes to the backbones of the Internet. > > The exchanges of Hank Nussbacher and Steve Riley have brought up the > key issue that prices of transmission capacity play.However, some > crucial issues have not been discussed.I expect that (i) prices will > decrease, and that (ii) networks will be run at low utilization > levels, making QoS unnecessary.However, (ii) does not follow from > (i) directly.After all, how do we know that all those big new pipes > won't get filled as soon as they are put into service?It has been > pretty solidly established (see [1], for example) that on average > people spend a constant amount of time traveling.You build a > freeway, and now instead of driving 30 minutes over 10 miles of > congested city streets, people decide they will buy a bigger house > with more greenery in the suburbs and drive 30 minutes over 25 miles > of freeway.In the last 30 years, the average commute time in the > U.S. has not changed appreciably, but the distance traveled has gone > up.Complaints about road congestion have not gotten less, though, as > far as I can tell.It is not a priori inconceivable that this same > phenomenon will not operate on the Internet. In general, one does not build a large bridge between two distant land points based on the number of people who swim or go by boat currently between those 2 points. Or in film terms, "if you build it - they will come". -Hank > > My argument for why (ii) will follow from (i) is based on studies of > what people actually do.(The data and arguments are presented in > detail in [2].)In particular, on expensive trans-oceanic links, even > corporate private lines are congested.On the other hand, in the > U.S., private lines are in mostcases run at low fractions of their > capacity.University connections to the Internet vary all over the > lot in their utilization in the U.S., while in other countries they > tend to be congested.What that suggests is that what people value is > low transaction latency ("I want that Web page on my screen NOW," or > "I want my database query to be processed NOW"), and not lots of bits. > When prices are high, they put up with lousy quality, but when prices > are lower, at the level of U.S. domestic prices, they opt for the > quality they really want.That is what makes me think that the > Internet is not like freeways, and that indeed we will have uniformly > high quality IP transport without most of the QoS measures that are > being developed. > > The Internetevolving to avoid QoS should not be too surprising.The > computer industry was cited in these discussions by Steve Riley and > others.It is an instructive example. There were all sorts of > prioritization and pricing schemes for mainframes in computer centers. > (One of the most interesting ones was due to two of my former > colleagues [3].It not only had some nice theoretical optimality > properties, but was actually implemented at the Murray Hill Computer > Center of AT&T Bell Labs, and worked very well to produce essentially > full utilization of computing resources.)However, those guys aren't > famous.The reason is that we don't have computer centers any more. > They got displaced by PCs, which are run at ludicrously low fractions > of their capacity.This "waste" is tolerated because people want the > peak power of their 500 MHz Pentium III to bring up their PowerPoint > presentations, etc.The key issue is the utility that people get from > a resource (CPU power, transmission capacity, etc.)and their > willingness to pay for it.The evidence from data networks is that it > won't make much of a decrease in transmission prices to produce lower > utilization rates and better quality. > > Another argument I make against QoS is that it pretty much requires > usage-sensitive pricing.However, that is something that people > dislike, and are willing to pay quite a bit to avoid.(See [4] for > discussion, models, and references.) > > Finally, while I am skeptical of QoS, I should emphasize that I do see > important roles for some forms of it in certain situations.One is in > access networks, especially in the wireless area.It appears that > there will continue to be a huge mismatch between the bandwidth > available on fiber and over the air.Hence wireless bandwidth will be > a (relatively) scare resource, and so it probably makes sense to > ration it through QoS measures.The other role that I see for QoS is > in the core of the network, but in forms that do not require any > involvement on the part of the people at the edges of the network > (both end users and administrators).Nothing is ever free, and while > prices of transmission capacity are likely to plunge, total spending > is likely to go up.That is what happened with computers, printers, > etc.Thus there will still be an incentive to economize, but it will > have to be done in ways that do not burden too many people.(Hence > RED should be OK, since its operations are invisible to end users, > but asking those folks to prioritize their packets is not likely to > fly.)Again, we see that in other areas. Most folks could save at > least half of their disk space by compressing with any of the widely > available packages, but hardly any do.On the other hand, we do have > many highly trained experts workingon improvements to MPEG > compression algorithms. > > > References: > > [1] A. Schafer and D. Victor, The past and future of global mobility, > Scientific American, Oct. 1997.Available at > <http://www.sciam.com/1097issue/1097schafer.html>. > > [2] The economics of the Internet:Utility, utilization, pricing, and > Quality of Service, A. M. Odlyzko.Available at > http://www.research.att.com/~amo/doc/networks.html. > > [3] W. A. Gale and R. Koenker, Pricing interactive computer services, > Computer Journal, vol.27, no. 1 (1984), pp. 8-17. > > [4] Fixed fee versus unit pricing for information goods:competition, > equilibria, and price wars, P. C. Fishburn, A. M. Odlyzko, and R. C. > Siders, First Monday 2(7) (July 1997), http://www.firstmonday.dk/. > Also available at http://www.research.att.com/~amo/doc/eworld.html. > > > > Addendum:Current high prices are already less of a problem than many > folks claim.Hank Nussbacher cites as the extreme example of T3 > pricing the $400K/month that a Tokyo-LA link costs.Now a T3 running > at full capacity will transmit just about 15 TB (terabytes) in each > direction per month.Let's suppose that we run the LA to Tokyo > direction at 53% of capacity, so we will transport 8 TB. The quality > won't be the greatest, but many carriers tolerate even higher > utilizations on such high-cost links.That will give us a cost > (ignoring traffic in the other direction) of $0.05 per MB. Now in the > U.S., with the flat-rate modem access to the Internet at $20/month > (and no local callfees, which constrain usage in other countries), > the average customer downloads about 60 MB per month.(One way to > derive that type of estimate is to take the average 55 minutes per day > that AOL folks have been clocking recently, according to an AOL press > release, and factor in an average data transfer rate of about 5 Kbps, > about 20% of the maximal 28.8 modem rate.)Hence even if the Tokyo > residential modem customers behaved like AOL ones here in the U.S., > and all their Web surfing was in the U.S., the cost of transporting > their traffic across the Pacific would still be only $3/month. > > > ************************************************************************ > Andrew Odlyzko [email protected] > AT&T Labs- Research voice: 973-360-8410 > http://www.research.att.com/~amo fax: 973-360-8178 > ************************************************************************ > > Hank Nussbacher
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