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Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

The Internet is made up of independently managed but interconnected networks called autonomous systems or ASs. Lower-level service providers need to use the routes across higher-level service providers. Many national service providers also need to exchange routes with one another. Peering refers to a relationship between two service providers that agree to exchange traffic and routing policies, usually across a direct link that the two service providers establish. An analogy is the way that states allow the free exchange of traffic across their highway systems.

Peering agreements may take place between local ISPs or ISPs that provide the major backbone networks of the Internet.

Peering also involves the exchange of routing information among networks. The information is in aggregated form and describes only the prefixes. See "Route Aggregation" and "Routing Registries."

This topic continues in "The Encyclopedia of Networking and Telecommunications."

A useful document is RFC 2650 (Using RPSL in Practice, August 1999), which discusses the RPSL language and peering policies. See Section 2.1 on common peering policies for information. Other RFCs of interest are RFC 1786 (Representation of IP Routing Policies in a Routing Registry, March 1995), RFC 1787 (Routing in a Multi-provider Internet, April 1995), and RFC 2260 (Scalable Support for Multi-homed Multi-provider Connectivity, January 1998).

A form of peering also takes place between ISPs and the carriers. An ISP will peer with a CLEC-for example, to gain access to its SS7 network connections and, therefore, access to the public-switched network. This allows the ISP to route VoIP (Voice over IP) calls to and from the traditional telephone network.

Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.
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