Finally, the large IBPs moved away from public NAPs to private peering or maintained relatively small capacities like T3 in the NAPs and then placed themselves in a new hierarchy, so called top-tier IBPs (Jew and Nicolls, 1999).
It is indeterminate what the exact requirements for the private peering are since peering agreements are under non-disclosure.
Some of the Big 5 did not want to peer with PSINet, because some of PSINet's private peering partners are transit customers of the Big 5.
Or if performance is the top priority, they may prefer private peering or transit to public peering.
Both parties decide (1) how many interconnection points they have, (2) where to locate the interconnection points, (3) how they interconnect, private peering or public peering, (4) what line capacity they will use, (5) settlement free or settlement involved, etc.
In addition, to ensure that its customers' network traffic is always routed via the fastest, most resilient path, PIPEX has over 200 public and private peering
arrangements with large Internet backbone providers, including the London Internet Exchange,