Line Rates and Hierarchy in SDH & SONET

The first hierarchy level for SDH is set at 155,520 kbit/s/s.

This is known as a Synchronous Transport Module 1 (STM-1).

Higher levels are simply multiples of the first level.

SDH allows for various PDH input rates to be mapped into containers as shown below:

• Container C11:      1544 kbit/s                  (1.5 Mbit/s) 
  Container C12:      2048 kbit/s                  (2 Mbit/s)
  Container C2:        6312 kbit/s                  (6 Mbit/s)
  Container C3:        49,536 kbit/s               (45 & 34 Mbit/s)
  Container C4:        139,264 kbit/s             (140 Mbit/s) 
  
  
  As can be seen from this chart, the only PDH rate that is not supported by SDH is 8 Mbit/s.