Internet Service Providers (ISP) and content providers exchange traffic using private and public Internet peering links. On these peering links, they rely on the Border Gateway Protocol (BGP) to exchange routing information. Various websites provide information about the peering links used by these ISPs, notably PeeringDB. Anurag Bhatia published on twitter an interesting list of the top 25 ISPs with the largest public peering capacity :

The top 5 are :

• Akamai, AS20940 with 41 Tbps
• Facebook, AS32934 with 38 Tbps
• Amazon Web services AS16509 with 35 Tbps
• Hurricane Electric AS6939 with 29 Tbps
• Microsoft AS8075 with 28 Tbps

Note that since this list is extracted from PeeringDB, it ignores the private peerings and the transit links. Some ISPs have more peering capacity that mentioned in this list.