Peering is the physical interconnection of separate networks for the purpose of exchanging traffic between the customers of each network.
Here’s a video that explains Peering in non-technical terms:
Immediately after Hurricane Sandy, we noticed massive packet loss between Verizon and Comcast. The most obvious example is loss of VPN and Remote Desktop connectivity between Verizon and Comcast sites. Another example: If you’re on Comcast and are trying to go to a Web site hosted on Verizon’s network, it may be slow or you might not be able to connect.
Tata Communications appears to handle Peering for Verizon and Comcast in our area. I can’t say for sure, but I believe this used to be done at Tata’s Matawan, NJ Data Center for the Northeast. In the screen shot below, you can see that traffic for Delaware and Pennsylvania is being routed through Ashburn, Virginia. One possible explanation is that traffic is now being routed through VA due to problems in New Jersey and New York after Hurricane Sandy. Whatever the cause, packet loss is massive, and connectivity between Comcast and Verizon is lousy right now. We tested multiple examples in both directions all with the same result.