The interoffice network interconnects the telephone central offices (COs). For the most part, COs are interconnected by fiber optic cables. Typically, each cable contains many fibers. Each fiber has a very large capacity and can potentially support data rates of hundreds of gigabits per second.
Ring-Based Interoffice Networks
The physical architecture of interoffice networks is mesh-based. However, traffic flows through current interoffice networks along interlocking SONET rings. These rings provide resiliency in the presence of network failures. If a failure occurs along one side of the ring, traffic can be re-routed along the opposite side of the side of the ring.
Mesh-Based Interoffice Networks
Compared to ring-based networks, mesh-based interoffice networks provide: more flexibility, higher protection efficiency, and robustness against a wider range of network failures.
Click here to read a paper comparing ring-based versus mesh-based interoffice networks and describing how protection and fast restoration could be implemented in a mesh-based network. This paper was originally published in the Proceedings of the Design of Reliable Communication Networks (DRCN) 2003 in October 2003.
Aggregation of Traffic
User traffic is backhauled through the access network and aggregated in the interoffice network. Click here to read a paper describing how aggregation reduces the burstiness of the traffic, which makes circuit switching efficient for transporting aggregated traffic. This paper was originally published in the Proceedings of the 8th International Conference on Signal Processing Applications and Technology in September 1997. Note that I no longer favor the all-optical backbone described in the paper.
Interoffice Network Architecture
Click here to read a paper describing an architecture for interoffice network that supports telecom convergence.