542 CHAPTER 29: CPOS INTERFACE CONFIGURATIONThe two TU-12s are called adjacent, if they have the same TUG-3 number andTUG-2 number but different TU-12 numbers with a discrepancy of 1.n The numbers in the aforementioned formula refer to the location numbers in aVC-4 frame. TUG-3 can be numbered in the range 1 to 3; TUG-2 in the range 1 to7 and TU-12 in the range 1 to 3. TU-12 numbers indicate the order in which the63 TU-12s in a VC-4 frame are multiplexed, that is, E1 channel numbers.Figure 153 Order of TUG-3s, TUG-2s, and TU-12s in a VC-4 frameYou can calculate TU-12 numbers in the same way when the AU-3 path is used.When 63 E1 channels or 84 T1 channels are configured on a CPOS interface, youcan reference E1 or T1 channels by referencing the numbers in the range 1 to 63or 1 to 84. When connecting your device to channelized STM-1 interfaces ondevices of other vendors, you should consider the possible numbering differencesresult from different channel referencing approaches.Overhead Byte SDH provides layered monitoring and management of precise division.It provides monitoring at section and channel levels, where sections are subdividedinto regenerator and multiplex sections, and channels are subdivided intohigher-order and lower-order paths. These monitoring functions are implementedusing overhead bytes.n SDH provides a variety of overhead bytes, but only those involved in CPOSconfiguration are discussed in this section. For more information about overheadbytes, refer to related books.■ SOHSection overhead (SOH) consists of regenerator section overhead (RSOH) andmultiplex section overhead (MSOH).The regeneration section trace message J0 is included in RSOH to send the sectionaccess point identifier repeatedly. Based on the identifier, the receiver can makesure that it is in continuous connection with the sender. This byte can be anycharacter in the network of the same operator. If networks of two operators areVC-4 TUG-3TUG-3TUG-3TUG-2TU-12TU-12TU-12TUG-2TU-12TU-12TU-12TUG-2TU-12TU-12TU-12123127...123123123
