[samdcbu]

Most of Comcast’s internet is exchanged through transit-free peering agreements, so only about 1% of Comcast’s outbound traffic requires them to pay for IP transit. And that traffic is mainly overseas, so Comcast is effectively a Tier 1 network in the US. Which means their customers’ outbound traffic doesn’t cost them anything.

For most last-mile ISPs, peering isn’t a revenue source. Small ISPs have to pay for peering and IP transit, and large ISPs have transit-free peering agreements with most, if not all, of the internet.

However, large ISPs that enjoy regional monopolies can refuse to upgrade connections with peered networks in an attempt to force the content providers sending traffic over the peered network to instead peer directly with the ISP.

This tactic is really only feasible for ISPs who have captive customers that are unable to switch to another ISP, as the negotiation process requires the ISP to allow the service it is providing to its actual customers to degrade to such an extent that the content provider is forced to peer directly with the ISP.