Agilent Technologies J3919A Installation & User Manual page 170

Path Overhead
The Path Overhead (POH) is a 1 byte field in a DS3 PLCP frame that provides
specific functions. The Z bytes (Z1-Z6) are reserved for future functions. The B1
byte is used for Bit Interleaved Parity (BIP-8) which checks for errors and
performance conditions. The G1 byte is used for the PLCP Path Status which
controls error conditions. The C1 byte provides for bit stuffing.
Path Overhead Identifier (POI)
The Path Overhead Identifier (POI) is the label for the function of each Path
Overhead byte in a PLCP frame.
POI - POI Value (8 bit)
P11- 00101100
P10- 00101001
P9 - 00100101
P8 - 01000000
P7 - 00011100
P6 - 00011001
P5 - 00010101
P4 - 00010000
P3 - 00001101
P2 - 00001000
P1 - 00000100
P0 - 00000001
Payload
The payload of an ATM cell is the 48 bytes available for data. This field is also
called the Cell Payload or Data Payload.
Payload Type (PT)
A field in the header of an ATM cell used to identify the type of information being
transported that may require different handling by the network or terminating
equipment.
150
POH
Z6
Z5
Z4
Z3
Z2
Z1
X
B1
G1
X
X
C1