Michael Dillon michael at
Fri Aug 21 17:30:47 UTC 1998

On Fri, 21 Aug 1998, Goodwin, Dustin wrote:

> Both companies get payed for providing a
> service. Where is the problem? Why should BBN get a cut of what Exodus's
> cutomers pay? BBN is trying to get payed to provide something it needs to
> from Exodus. If BBN needs it, why would Exodus pay for it? Isn't BBN trying
> to get payed twice?

You are asking about specifics and I have no idea what the answers are.
Unless somebody speaks to both Exodus and BBN and gets around the NDAs
that they have signed, I don't think anyone can know. 

However, there is a more general issue here. If a company primarily hosts
websites, then their traffic will be asymmetric with many more bytes going
out than coming in. They must engineer their network to handle this
asymmetry and any transit providers they have must also do so.
Traditionally, peering only occurred between providers with a national
network with at least 4 points of contact, spread out geographically. This
requirement is so that each provider carries a roughly equal load of the
traffic across expensive national longhaul circuits. It is this balanced
transit load that makes them peers.

In the case of a web hosting company, the bulk of the traffic is outgoing
and if they do the standard shortest-exit routing with their peers, then
the peer will be carrying a much larger transit load than the webhosting
company. Of course, this could be solved by both parties doing
longest-exit which places the largest transit load on the webhosting
provider. But there is more.

When the webhosting network touches down at only a few exchange points to
peer with a provider who has an extensive network you will have a
situation in which the peer is providing regional transit for free and
must engineer their regional networks to deal with an asymmetric traffic
pattern. For instance, if a webhosting provider touches down at San Jose,
Chicago, DC and Dallas then they appear to meet the eligibility
requirements for peering. But these peers end up providing full transit
from Boston to DC, LA to San Jose, Denver to Dallas, and St. Louis to
Chicago. This arises because one provider hosts lots of equipment close to
an exchange point and the other provider interconnects many POPs in many

Somehow we need a way to quantify and measure the traffic and establish
what peering is in terms of measurable quantities. A certain amount of
asymmetry should be allowable but it can get out of hand. One way to deal
with great asymmetry is to deny peering. Another way is to accept peering
but measure the asymmetry and have a pricing structure for regional
transit that applies after a certain point. Note that this is *NOT* the
same as demanding that the webhosting peer become a transit customer.
Since they are only using regional transit I would expect that the prices
on the transit portion would be less than on a pure transit arrangement.

However, for this to happen we would need some way to measure and quantify
this regional transit. To date I don't think anyone has attempted to do
anything like this except some Australian ISPs who have mapped the IPv4
address space geographically so that they can manage their routing
according to the cost of various intercontinental links without relying on
somebody else's BGP announcements. I'm sure that we could use some sort of
similar geographical mapping of IPv4 addresses to quantify how much
regional transit a peer uses and thus establish a sliding scale between
a pure transit customer and a pure peer.

Michael Dillon                 -               Internet & ISP Consulting
Memra Communications Inc.      -               E-mail: michael at
Check the website for my Internet World articles -        

More information about the NANOG mailing list