<P> Data transmitted from end to end is referred to as path data . It is composed of two components: </P> <Dl> <Dd> <Dl> <Dt> Payload overhead (POH) </Dt> <Dd> 9 octets used for end - to - end signaling and error measurement . </Dd> <Dt> Payload </Dt> <Dd> User data (774 bytes for STM - 0 / STS - 1, or 2,430 octets for STM - 1 / STS - 3c) </Dd> </Dl> </Dd> </Dl> <Dd> <Dl> <Dt> Payload overhead (POH) </Dt> <Dd> 9 octets used for end - to - end signaling and error measurement . </Dd> <Dt> Payload </Dt> <Dd> User data (774 bytes for STM - 0 / STS - 1, or 2,430 octets for STM - 1 / STS - 3c) </Dd> </Dl> </Dd> <Dl> <Dt> Payload overhead (POH) </Dt> <Dd> 9 octets used for end - to - end signaling and error measurement . </Dd> <Dt> Payload </Dt> <Dd> User data (774 bytes for STM - 0 / STS - 1, or 2,430 octets for STM - 1 / STS - 3c) </Dd> </Dl>

Sonet/sdh can be used to carry signals from pdh atm b isdn