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Re: Trans-Atlantic Traffic

  • From: Sean M. Doran
  • Date: Thu Aug 21 16:45:32 1997

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.




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