hich can be partitioned into a series of subnet- tions, termination functions and the chain of subnetwork and link works. (See Figure 42.30.) These subnetworks are connected connections in the VC12 layer have succeeded in transporting this together by 'link connections', and can, if necessary, be further 2Mbit/s circuit between the two end points of a single 2Mbit/s link subdivided into yet smaller subnetworks. The logical place to stop connection. (See Figure 42.31.) From this point, the above analysis this process is where a whole subnetwork is completely contained can now be repeated in the 2Mbit/s layer, where the particular within one network element. As an example consider a VC12 cross 2Mbit/s circuit cited above will probably be found to be serving as connect. The switching matrix (connectivity function) within this part of a link connection for a number of 64kbit/s circuit (see Figure element could be considered as a subnetwork, which is capable of 42.27). Plesio- Plesio- chronous chronous chronous 64kbit/s primary 34 & 45M Services layers layers layers VC1 syn VC1 asyn VC3 asyn VC2.nc LOWER ORDER PATH LAYER 140Mbit/s Network 149.92Mbit/s Layer cellstream Adaptation: VC1, VC2 and VC3 in VC4 VC4 async VC4 byte sync HIGHER ORDER PATH LAYER Adaptation: VC4 in STM-1 STM SECTION LAYER Adaptation Optical Interface Parameters OPTICAL SECTION LAYER Figure 42.28 Layering in an SDH transport network 42/22 The Synchronous Digital Hierarchy (SDH) Link connection in client layer CLIENT LAYER SERVER LAYER Adaptation function ie. server layer adapts client layer information to server layer format Path terminations ie. server layer adds overheads to adapted info Path in server layer Figure 42.29 Handling a link connection in a client layer by a path in a server layer This formal description of an SDH network opens up the prospect greatly facilitates management of the all important traffic flexibility of real control and management of large networks consisting of points i.e. those subnetworks which consist of an electroni