I just left the carrier side of the house. We were migrating to all Soft Switchs. Santera's, which got bought out by some other company about 1 year after they came out. The soft switch has a ton of issues, especially on dynamic T1 and dynamic PRI. They emulate the different protocols for L2 PRI. The main reason Carriers are migrating is cost and space saving. Avg 5e expansion is hundreds of thousands of dollars, and a SM takes up quite a lot of space. You can feed the same amount of circuits out of a soft switch in one rack space equivalent to I believe 4 SMs for about 300K, versus 2 million for 4 SMs.
