What is the difference between SONET and SDH?
A. To begin with there is no STS-1. The first level in the SDH hierarchy is STM-1 (Synchronous Transport Mode 1) is has a line rate of 155.52 Mb/s. This is equivalent to SONET’s STS-3c. Then would come STM-4 at 622.08 Mb/s and STM-16 at 2488.32 Mb/s. The other difference is in the overhead bytes which are defined slightly differently for SDH. A common misconception is that STM-Ns are formed by multiplexing STM-1s. STM-1s, STM-4s and STM-16s that terminate on a network node are broken down to recover the VCs which they contain. The outbound STM-Ns are then reconstructed with new overheads.
A. There is no STS-1. The first level in the SDH hierarchy is STM-1 (Synchronous Transport Mode 1) has a line rate of 155.52 Mb/s. This is equivalent to SONET’s STS-3c. Then comes STM-4 at 622.08 Mb/s and STM-16 at 2488.32 Mb/s. The other difference is in the overhead bytes which are defined slightly differently for SDH. A common misconception is that STM-Ns are formed by multiplexing STM-1s. STM-1s, STM-4s and STM-16s that terminate on a network node are broken down to recover the virtual circuits (VCs) they contain. The outbound STM-Ns are then reconstructed with new overheads.
