Cisco ONS 15454 - C2 Byte; Figure 4-1 Three SONET Layers; Table 4-2 C2 Byte Common Values

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Cisco ONS 15454 SONET/SDH ML-Series Multilayer Ethernet Card Software Feature and Configuration Guide, R4.0
78-15224-02
Chapter 4 Configuring Interfaces
POS on the ML-Series card
Figure 4-1 Three SONET Layers
C2 Byte
One of the overhead bytes in the SONET frame is the C2 Byte. The SONET standard defines the C2 byte
as the path signal label. The purpose of this byte is to communicate the payload type being encapsulated
by the SONET framing overhead (FOH). The C2 byte functions similarly to EtherType and Logical Link
Control (LLC)/Subnetwork Access Protocol (SNAP) header fields on an Ethernet network; it allows a
single interface to transport multiple payload types simultaneously. C2 byte hex values are provided in
Table 4-2.
B7 Byte3 Bytes
9 Rows
Section
Overhead
Line
Overhead
STS
Transport
Overhead
Payload Envelope
Payload
Capacity
83123
P
a
t
h
O
v
e
r
h
e
a
d
Table 4-2 C2 Byte Common Values
Hex Value SONET Payload Contents
00 Unequipped
01 Equipped non specific payload
02 Virtual Tributaries (VTs) inside (default)
03 VTs in locked mode (no longer supported)
04 Asynchronous DS3 mapping
12 Asynchronous DS-4NA mapping
13 Asynchronous Transfer Mode (ATM) cell mapping
14 Distributed Queue Dual Bus (DQDB) protocol cell mapping
15 Asynchronous Fiber Distributed Data Interface (FDDI) mapping
16 IP inside PPP with scrambling
CF IP inside PPP without scrambling
FE Test signal mapping (see ITU-T G.707)