More Questions of Exchange Points

    >> The difference between a peering exchange and a transit exchange is a much
    >> more easily technically-defined difference: a peering exchange is one
    >> across which, by and large, the participants just exchange peering routes.
    > Do you mean the participants just exchange BGP routing information? So the
    > traceroute data will only discover the peering point they exchange traffic?

The assumtion is that all ISPs exchange routes via BGP. What's at issue

  well, there are a fair number of exchanges built on a model
  developed by B.Greene, when BGP capability was not always there
  (often not a technology problem... :slight_smile: They are still a number of
  them in existence. The exchange routes using an IGP and fate
  share over the exchange. The BGP'ness occurs at each of their

is the degree of redundancy in the routes which they're exchanging. If
they're purchasing transit at or through a facility, it's to provide
reachability to things that they couldn't otherwise reach, either normally
or under conditions of failed peering. That makes the service much more
critical than peering, which is, by definition, an economic optimization
over transit. Thus, people are willing to spend much more money on a
facility through which they're putting transit, and they're willing to
tolerate a divided marketplace, as long as each facility is able to
maintain at least three sellers.

  I really need to read your paper. There appear to be a
  number of presumptions that are "cultural", for want of
  a better term, which bias your conclusions.

    > ISPs exchange their traffic at IXs or private peering points, so which
    > is more important to the ISPs (in term of traffic volume or other
    > measures)? Maybe I should also mention co-locators, then what's the
    > difference between co-locator and the "carrier hotel"? Are they like
    > "physical layer exchange points" (if there is such a concept)?

These aren't necessarily useful distinctions you're making. They're
distinctions of marketing positioning. What matters economically and
technically is how people use the facilities, not what they're called.