More appropriately then, peering means the exchange of an equitable and fair amount of data-miles between two networks, agreements of which do not preclude any pay-for-transit contracts to exist between the very same parties. On the subject of routing, settlement-free peering involves conditions disallowing the abuse of the other's network by sending it traffic not destined for that network (i.e. intended for transit). Transit agreements however would typically cater for just such outbound packets. Tier 1 providers are more central to the Internet backbone and would only purchase transit from other Tier 1 providers, while selling transit to providers of all tiers. Given their huge networks, Tier 1 providers often do not participate in public Internet Exchanges but rather sell transit services to such participants and engage in private peering.
More appropriately then, peering means the exchange of an equitable and fair amount of data-miles between two networks, agreements of which do not preclude any pay-for-transit contracts to exist between the very same parties. On the subject of routing settlement-free peering involves conditions disallowing the abuse of the other's network by sending it traffic not destined for that network (i.e. intended for transit). Transit agreements however would typically cater for just such outbound packets. Tier 1 providers are more central to the Internet backbone and would only purchase transit from other Tier 1 providers, while selling transit to providers of all tiers. Given their huge networks, Tier 1 providers often do not participate in public Internet Exchanges but rather sell transit services to such participants and engage in private peering.