OC48 and OC192 cross-country links interconnect backbone nodes in 27 major cities, while a series of OC3 circuits link 100 additional cities to the backbone. High reliability is provided by a multiple-ring design that allows for Layer 3 rerouting between nodes in the event of a facility failure. All equipment is deployed in a redundant configuration.
All backbone routers have redundant power supplies and route switch processors.
In addition, backbone routers are paired for additional reliability so that a path is always available out of a backbone node. The result is a solid core network architecture in which there is virtually no single point of failure. A comprehensive testbed network environment is utilized for controlled introduction of new features and capabilities to maximize network performance and reliability even as the backbone is being upgraded. Today, private peering agreements, also known as direct connections, are increasingly used by most providers, enabling them to directly exchange IP traffic without having to go through a Public peering location, a potential bottle-neck as traffic increases. Modifications of route advertisements could possibly result in network unreachability, thus causing disruptions in service.