This article is the 4 agreements pdf how Internet networks exchange traffic with each other’s users. For information on peer-to-peer networks, see Peer-to-peer. In computer networking, peering is a voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the users of each network. Occasionally the word “peering” is used to describe situations where there is some settlement involved.

In the face of such ambiguity, the phrase “settlement-free peering” is sometimes used to explicitly denote pure cost-free peering. The Internet is a collection of separate and distinct networks referred to as autonomous systems, each one operating under a common framework of globally unique IP addressing and global BGP routing. Two networks exchange traffic between their users freely, and for mutual benefit. A network pays another network money to be provided with Internet access. Pay another network for transit service, where that other network must in turn also sell, peer, or pay for access. 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 which also does not purchase transit. 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”. Increased routing control over your traffic. Interconnection utilizing a multi-party shared switch fabric such as an Ethernet switch.

Interconnection utilizing a point-to-point link between two parties. 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. 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.

A few exchange points, particularly in the United States, are operated by commercial carrier-neutral third parties, which are critical for achieving cost-effective data center connectivity. 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. 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. Throughout the history of the Internet, there have been a spectrum of kinds of agreements between peers, ranging from handshake agreements to written contracts as required by one or more parties. The first exchange point to resemble modern, neutral, Ethernet-based exchanges was the Metropolitan Area Ethernet, or MAE, in Tysons Corner, Virginia.

As the Internet grew, and traffic levels increased, these NAPs became a network bottleneck. Internet exchange points due to the reduced cost and increased capacity offered. During the dot-com boom, many exchange point and carrier neutral colocation providers had plans to build as many as 50 locations to promote carrier interconnection in the United States alone. Essentially all of these plans were abandoned following the dot-com bust, and today it is considered both economically and technically infeasible to support this level of interconnection among even the largest of networks. By definition, peering is the voluntary and free exchange of traffic between two networks, for mutual benefit. If one or both networks believes that there is no longer a mutual benefit, they may decide to cease peering: this is known as depeering. A desire that the other network pay settlement, either in exchange for continued peering or for transit services.

A belief that the other network is “profiting unduly” from the no-settlement interconnection. Concern over traffic ratios, which is related to the fair sharing of cost for the interconnection. A desire to peer with the upstream transit provider of the peered network. Abuse of the interconnection by the other party, such as pointing default or utilizing the peer for transit. Instability of the peered network, repeated routing leaks, lack of response to network abuse issues, etc. The inability or unwillingness of the peered network to provision additional capacity for peering. The belief that the peered network is unduly peering with your customers.