Simon Leinen <simon@limmat.switch.ch> writes:

There are many of these small links over the pond.

One of the reasons there are so many trans-oceanic links between Europe and North America is that the cost of a trans-oceanic full-circuit is almost infinitely cheaper than inter-country circuits at PNO tariffs, thanks to inexpensive U.S. half-circuits. This is changing, largely due to E.U. telecomms liberalization.

I'd be interested in whether (and if so: how) different providers manage to save costs by sharing fast transcontinental lines among themselves.

Hm, I wonder if I can put enough value into answering this question to have people forgive me for talking about my (European) employer on an ostensibly North American mailing list? :-) Ebone is a customer-owned trans-continental backbone provider that functions as a buyers' cooperative with respect to inter-country (and in some cases intra-country) capacity. The not-marketing-person designed web page describing this can be found at http://www.ebone.net/structure/objectives.html This largely works in part because of the origins of Ebone and the people who have worked with it since then, and because Ebone focuses principally on large ISPs. That leads to the assumption that customers aggregate enough traffic that they will use all the capacity they pay for at all times, which also leads to Ebone's no-overbooking design, and consequently to Ebone's rather large cost-based prices relative to its competitors which target vastly different markets, or do massive loss-leading, or do massive cross-subsidy, or all three. One way of looking at the Ebone backbone is as a large TDM network, much as one could build with ATM and CBR VCs, only without the drawbacks of ATM or a big VC mesh (and with the drawbacks of a complicated router-based network). There are of course several other pan-European providers such as Unisource's UBN, BT's CIP, UUNET, EUNET, Compuserve, Global -1, and IBM Advantis, each of which appears to function much like their counterparts or analogues in the U.S.A. This, however, is not exactly "line sharing" per se. Finally, there may be people sharing lines bilaterally or multilaterally among a small group of organizations. Some alternative capacity providers are offering decent rates on STM-1s among large cities; pulling VC3s or VC4s out of an STM-1 and paying proportionately has some economic attraction, particularly in cases where competition among providers doing this isn't quite as cutthroat as it is in North America. A "how" diagram following a model other than something closely mirroring the Ebone approacj would be: City A City B provider 1-----\ /-------provider 1 | | provider 2-----ADM===========ADM------provider 2 | | provider 3-----/ \-------provider 3 Where the single-stroke lines represent 45Mbps or 34Mbps circuits, whether through a local bandwidth provider (like the PNO) or using cables or something across a colocation facility like Telehouse, and the double-stroke line represents an international STM-1 provided by a bandwidth carrier. This kind of thing tends to bring the per-bit-per-second-per-month price down quite a bit compared to three individual E3s or DS3s, assuming that pricing is done relative to ordinary PNO tariffs. There are cost and complexity issues for all largeish ISPs to consider when choosing among various approaches for moving traffic around, obviously, so there is certainly on One True Approach to sharing really expensive bandwidth. One observation, however, is that aggregating providers appear to be popular choices when dealing with very expensive lines or high levels of complexity, and unpopular choices when they don't actually solve either problem (like when a large ISP can't use much of its flat-rate paid-for bandwidth because of massive overbooking or other design issues, or when routing and other things break alot). Finally, returning to the question of how many small pipes there are and how much trans-oceanic bandwidth there is, it is worth noting that a large number (but not most) of Ebone's customers have their own circuits across the Atlantic ocean, in spite of Ebone's pricing discounts on people who use Ebone'e trans-atlantic capacity. (Our trans-atlantic capacity is vastly less expensive than our trans-European capacity, and across a full customer pipe, a customer who is receiving U.S.-sourced traffic (or sending U.S.-bound traffic) through Ebone typically uses enough traffic that the cost incurred by meeting that customer's traffic needs is less than the cost incurred if the pipe was full of only European-to-European traffic). In essence, the reason there are lots of trans-Atlantic pipes is that in order to have sufficient capacity one would have to connect with a relatively large pipe to a trans-Atlantic traffic aggregator, which tends to be alot more expensive than a smaller pipe within Europe and a separate pipe across the ocean. This will probably remain the case, price-wise, until intra-European bandwidth prices fall to less than inter-continental prices, or to the point where the cost of connecting to a provider (or multiple providers) within Europe is perceived as less than the cost of maintaining a more complicated network. Sean.