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Peering is

a voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the customers of each network.[1]
A relationship established between two or more Internet Service Providers (ISP) for the purpose of exchanging traffic directly, rather than doing so through a backbone Internet provider.[2]


Peering has a number of distinctive characteristics. First, peering partners only exchange traffic that originates with the customer of one backbone and terminates with the customer of the other peered backbone. . . . The second distinctive characteristic of peering is that peering partners exchange traffic on a settlements-free basis. . . . Additional characteristics of peering relate to the routing of information from one backbone to another. Peering partners generally meet in a number of geographically dispersed locations. . . . A final characteristic of peering is that recipients of traffic only promise to undertake "best efforts" when terminating traffic, rather than guarantee any level of performance in delivering packets received from peering partners.[3]

The pure definition of "peering" is settlement-free or "sender keeps all," meaning that neither party pays the other for the exchanged traffic; instead, each derives revenue from its own customers.

Marketing and commercial pressures have led to the word "peering" routinely being used when there is some settlement involved, even though that is not the accurate technical use of the word. The phrase "settlement-free peering" is sometimes used to reflect this reality and unambiguously describe the pure cost-free peering situation.

Peering requires physical interconnection of the networks, an exchange of routing information through the Border Gateway Protocol (BGP) routing protocol and is often accompanied by peering agreements of varying formality, from "handshake" to thick contracts.

How peering works[]

The Internet is a collection of separate and distinct networks, each one operating under a common framework of globally unique IP addressing and global BGP routing.

The relationships between these networks are generally described by one of the following three categories:

Furthermore, in order for a network to reach any specific other network on the Internet, it must either:

The Internet is based on the principle of "global reachability" (sometimes called "end-to-end reachability"), which means that any Internet user can reach any other Internet user as though they were on the same network. Therefore, any Internet-connected network must by definition either pay another network for transit, or peer with every other network who also does not purchase transit.

Motivations for peering[]

Peering involves two networks coming together to exchange traffic with each other freely, and for mutual benefit. This "mutual benefit" is most often the motivation behind peering, which is often described solely by "reduced costs for transit services." Other less tangible motivations can include:

  • Increased capacity for extremely large amounts of traffic (distributing traffic across many networks).
  • Increased control over your traffic (reducing dependence on one or more transit providers).
  • Improved performance (attempting to bypass potential bottlenecks with a "direct" path).
  • Improved perception of your network (being able to claim a "higher tier").
  • Government regulations, or the desire to avoid the appearance of being a monopoly.


See also[]

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