Editing Peering (section)

==Physical interconnections for peering==
[[File:IXP Topology L1-L2.svg|thumb|Diagram of the Layer 1 (physical) and Layer 2 (Data Link) topology of an Internet Exchange Point (IXP).]]
[[File:IXP Topology L3.svg|thumb|Diagram of the Layer 3 (network) topology of an Internet Exchange Point (IXP).]]

The physical interconnections used for peering are categorized into two types:

* Public peering – Interconnection utilizing a multi-party shared switch fabric such as an [[Ethernet]] switch.
* Private peering – Interconnection utilizing a point-to-point link between two parties.

===Public peering===
'''Public peering''' is accomplished across a [[Layer 2]] access technology, generally called a ''shared fabric''. At these locations, multiple carriers interconnect with one or more other carriers across a single physical port. Historically, public peering locations were known as [[network access point]]s (NAPs). Today they are most often called [[Internet exchange point|exchange points]] or ''Internet exchanges'' ("IXP"). Many of the largest exchange points in the world can have hundreds of participants, and some span multiple buildings and [[Colocation centre|colocation]] facilities across a city.<ref>{{cite web |url=http://pch.net/ixpdir |title=Internet Exchange Directory|website = Packet Clearing House}}</ref>

Since public peering allows networks interested in peering to interconnect with many other networks through a single port, it is often considered to offer "less capacity" than private peering, but to a larger number of networks. Many smaller networks, or networks which are just beginning to peer, find that public peering exchange points provide an excellent way to meet and interconnect with other networks which may be open to peering with them. Some larger networks utilize public peering as a way to aggregate a large number of "smaller peers", or as a location for conducting low-cost "trial peering" without the expense of provisioning private peering on a temporary basis, while other larger networks are not willing to participate at public exchanges at all.

A few exchange points, particularly in the United States, are operated by commercial carrier-neutral third parties which often are data centers, which are critical for achieving cost-effective [[data center]] connectivity.<ref name=DRJ_Choosing>{{Citation | title = Choosing a Data Center  | url=http://www.atlantic.net/images/pdf/choosing_a_data_center.pdf | publisher = Disaster Recovery Journal | year = 2009 | author = Cosmano, Joe | access-date = 21 July 2012}}</ref>

===Private peering===
'''Private peering''' is the direct interconnection between only two networks, across a Layer 1 or 2 medium that offers dedicated capacity that is not shared by any other parties. Early in the history of the Internet, many private peers occurred across "telco" provisioned [[SONET]] circuits between individual carrier-owned facilities. Today, most private interconnections occur at [[Colocation centre|carrier hotel]]s data centers<ref>https://www.datacenterfrontier.com/colo/article/55125540/data-center-tours-equinix-dc12-ashburn-virginia</ref> or carrier neutral colocation facilities, where a direct crossconnect can be provisioned between participants within the same building, usually for a much lower cost than telco circuits.

Most of the traffic on the Internet, especially traffic between the largest networks, occurs via private peering. However, because of the resources required to provision each private peer, many networks are unwilling to provide private peering to "small" networks, or to "new" networks which have not yet proven that they will provide a mutual benefit.