Third generation SONET

Connectivity to Ethernet: Transporting IP voice and Ethernet traffic on SONET-equipped links wastes capacity on carriers' networks. This is because SONET carries traffic in "chunks" at 64 kilobits per second in fixed-size frames called cells. However, IP and Ethernet traffic bits are in variable-size packets. In addition, SONET cells have high overhead (nonuser data such as monitoring and addressing), which adds to its inefficiency because less customer traffic is carried in each cell. This mismatch between frame size results in carriers stuffing zeros into many SONET frames.

Some manufacturers have developed SONET equipment that handles packet traffic more efficiently. For example, newer multiplexers have Gigabit Ethernet ports and ports that can interface directly with telecommunications services used in storage area networks. These SONET multiplexers have the capability to pick up and drop off Ethernet and IP traffic more efficiently at Ethernet speeds. However, they transport traffic to older SONET devices in SONET frames, which wastes capacity.