Is anyone actually USING IP QoS?

Hank Nussbacher hank at
Wed May 19 16:23:53 UTC 1999

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
> <>.
> [2] The economics of the Internet:Utility, utilization, pricing, and
> Quality of Service, A. M. Odlyzko.Available at
> [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),
> Also available at
> 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                                    amo at
> AT&T Labs- Research                              voice:  973-360-8410 
>                  fax:    973-360-8178
> ************************************************************************

Hank Nussbacher

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