Essay on SDH and SONET

SONET is a set of transport containers which allows for delivery of a variety of protocols for example telephony, Ethernet and TCP/IP traffic. Sonnet thus is not specifically meant for communication and should not be mistsken as being necessarily connection oriented.

This transmission method was developed to replace the plesiochronous digital hierarchy(PDH) used manily for transporting large ammoouts of data traffic and telephone calls within the same fiber under little or no synchronization problems. The differ from pdh because the exact rates use to transport dat on sonnet and sdh are tightly synchronized across the entire network by use of atomic clocks. This sytem allows networks across the country to interact sychromnously thus reducing buffering

The idea of SONET and SDH was originally to facilitate the transportation of circuit modes for transmitting information from different sources, however they were designed specifically to support uncompressed, real-time and circuit switched voice encoded in PCM format. SONET/SDH is not a communications protocol but a transport protocol that facilitates transmission.

Sdh is framed by a unit of transmission STM-1 (synchronous transport module, level 1) operationg at a speed of 155.520 (Mbits/s). SONET refers to this unit as STS-3C (Synchronous transport signal, concatenated). The speed of this signals is determined by the bandwith requirements of for encoded telephonic signals.

In synchronous optical networking the header is termed as the overhead which is interleaved during transmission. Part of the overhead is transmitted then part of the payload, followed by the next part of the overhead, then the next part of payload done until the entire frame has been transmitted. Structurally the internal frame of sonnet and sdh differs on the overhead and the payload.

SDH frame the synchronous transport module, level 1(STM-1) frame form the basic transmission format in SDH. This frames comprises of the overheads and pointers as well as information about pointers. The nine first column make the overhead section and the administrative pointers while the columns make up the information payload. THE STM frame is continuos transmitted byte by byte and row by row in a seral manner.Transport overhead is used for signaling and measuring transmitiion rates of error under different areas. These includes regenerator section overhead (RSOH) in sdh terminology and contains information about the frame structure required by the terminal equipment.Line overhead named ,multiplex overhead(MSOH) in SDH has 45 octets with data on error correction and automatic protection switching messages. Administrtative unit points to the locationof the J1 byte in the payload. Path virtual envelope involves transmitting data from one end to the other, payload overhead wher Nine octets are used for end to end signaling whether there is an error in the measuerement.Network management systems are used to configure SDH and SONET equipmet locally. Overall fcutions of the network management