An asynchronous transfer mode (ATM) optical carrier (OC)–3c does not have the structure with the VTs, described earlier. It is simply filled with cells. The c stands for concatenated and means that the truck trailers on the OC–3 are seen as one. Data equipment using SONET rates greater than 155 Mbps tend to require concatenated containers. Backbone network elements at 2.5 and 10 Gbps must support this type of data structure (see Figure 9).

Figure 9. ATM OC–3c Data Structure