Page 1126 - 5G Basics - Core Network Aspects

2 Transport aspects

Columns 1 to 14 of the ODU are dedicated to ODU overhead area.

NOTE – Columns 1 to 14 of row 1 are reserved for a frame alignment and OTU specific overhead.
Columns 15 to 3824 of the ODU are dedicated to OPU area.

12.2 ODU bit rates and bit-rate tolerances
ODUk signals may be generated using either a local clock, or the recovered clock of the client signal. In the
latter case the ODUk frequency and frequency tolerance are locked to the client signal's frequency and
frequency tolerance. In the former case the ODUk frequency and frequency tolerance are locked to the
local clock's frequency and frequency tolerance. The local clock frequency tolerance for the OTN is specified
to be 20 ppm.

ODUCn signals are generated using a local clock. The ODUCn frequency and frequency tolerance are locked
to the local clock's frequency and frequency tolerance. The local clock frequency tolerance for the OTN is
specified to be 20 ppm.
ODU maintenance signals (ODU AIS, OCI, LCK) are generated using a local clock. In a number of cases this
local clock may be the clock of a server ODU signal over which the ODU signal is transported between
equipment or through equipment (in one or more of the tributary slots). For these cases, the nominal
justification ratio should be deployed to comply with the ODU's bit-rate tolerance specification.
12.2.1 ODU0, ODU1, ODU2, ODU3, ODU4, ODUCn

The local clocks used to create the ODU0, ODU1, ODU2, ODU3, ODU4 and ODUCn signals are generated by
clock crystals that are also used for the generation of SDH STM-N signals. The bit rates of these ODUk
(k=0,1,2,3,4) and ODUCn signals are therefore related to the STM-N bit rates and the bit-rate tolerances are
the bit-rate tolerances of the STM-N signals.
The ODU0 bit rate is 50% of the STM-16 bit rate.
The ODU1 bit rate is 239/238 times the STM-16 bit rate.

The ODU2 bit rate is 239/237 times 4 times the STM-16 bit rate.
The ODU3 bit rate is 239/236 times 16 times the STM-16 bit rate.

The ODU4 bit rate is 239/227 times 40 times the STM-16 bit rate.
The ODUCn bit rate is n times 239/226 times 40 times the STM-16 bit rate.

ODU1, ODU2 and ODU3 signals which carry an STM-N (N = 16, 64, 256) signal may also be generated using
the timing of these client signals.

Refer to Table 7-2 for the nominal bit rates and bit-rate tolerances.

12.2.2 ODU2e
An ODU2e signal is generated using the timing of its client signal.
The ODU2e bit rate is 239/237 times the 10GBASE-R client bit rate.

Refer to Table 7-2 for the nominal bit rate and bit-rate tolerances.
12.2.3 ODUflex for CBR client signals

An ODUflex(CBR) signal is generated using the timing of its client signal.
The ODUflex bit rate is 239/238 times the adapted CBR client bit rate.

The client signal may have a bit-rate tolerance up to 100 ppm.

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