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 one's customers. Various external political factors (including personal conflicts between individuals at each network). In some situations, networks which are being depeered have been known to attempt to fight to keep the peering by intentionally breaking the connectivity between the two networks when the peer is removed, either through a deliberate act or an act of omission. The goal is to force the depeering network to have so many customer complaints that they are willing to restore peering. Examples of this include forcing traffic via a path that does not have enough capacity to handle the load, or intentionally blocking alternate routes to or from the other network. Some notable examples of these situations have included: BBN Planet vs Exodus Communications PSINet vs Cable & Wireless AOL Transit Data Network (ATDN) vs Cogent Communications Teleglobe vs Cogent Communications France Telecom vs Cogent Communications France Telecom (Wanadoo) vs Proxad (Free) Level 3 Communications vs XO Communications Level 3 Communications vs Cogent Communications Telecom/Telefónica/Impsat/Prima vs CABASE (Argentina) Cogent Communications vs TeliaSonera Sprint-Nextel vs Cogent Communications SFR vs OVH The French ISP 'Free' vs YouTube Modern peering Donut peering model The "donut peering" model describes the intensive interconnection of small and medium-sized regional networks that make up much of the Internet. Traffic between these regional networks can be modeled as a toroid, with a core "donut hole" that is poorly interconnected to the networks around it. As detailed above, some carriers attempted to form a cartel of self-described Tier 1 networks, nominally refusing to peer with any networks outside the oligopoly. Seeking to reduce transit costs, connections between regional networks bypass those "core" networks. Data takes a more direct path, reducing latency and packet loss. This also improves resiliency between consumers and content providers via multiple connections in many locations around the world, in particular during business disputes between the core transit providers. Multilateral peering The majority of BGP AS-AS adjacencies are the product of multilateral