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Transport aspects 2

Appendix II

Examples of functionally standardized OTU frame structures
(This appendix does not form an integral part of this Recommendation.)

This appendix provides examples of functionally standardized OTU frame structures. These examples are
for illustrative purposes and by no means imply a definition of such structures. The completely
standardized OTUk frame structure as defined in this Recommendation is shown in Figure II.1. Functionally
standardized OTUkV frame structures will be needed to support, e.g., alternative FEC. Examples of OTUkV
frame structures are:
– OTUkV with the same overhead byte allocation as the OTUk, but use of an alternative FEC as
shown in Figure II.2;
– OTUkV with the same overhead byte allocation as the OTUk, but use of a smaller, alternative FEC
code and the remainder of the OTUkV FEC overhead area filled with fixed stuff as shown in
Figure II.3;

– OTUkV with a larger FEC overhead byte allocation as the OTUk, and use of an alternative FEC as
shown in Figure II.4;

– OTUkV with no overhead byte allocation for FEC as shown in Figure II.5;
– OTUkV with a different frame structure than the OTUk frame structure, supporting a different OTU
overhead (OTUkV overhead and OTUkV FEC) as shown in Figure II.6;

– OTUkV with a different frame structure than the OTUk frame structure, supporting a different OTU
overhead (OTUkV overhead) and with no overhead byte allocation for FEC as shown in Figure II.7.

Column #
....... .......
1 14 15 16 17 3824 3825 4080
1 FA OH OTUk OH Row 1 RS (255, 239) FEC redundancy
Row # 2 3 OTUk payload = ODUk Row 2 RS (255, 239) FEC redundancy
Row 3 RS (255, 239) FEC redundancy
4 Row 4 RS (255, 239) FEC redundancy
G.709-Y.1331(12)_FII.1

Figure II.1  OTUk (with RS(255,239) FEC)

Column #
....... .......
1 14 15 16 17 3824 3825 4080
1 FA OH OTUk OH
Row # 2 ODUk OH OPUk OTUkV FEC
3
4
G.709-Y.1331(12)_FII.2

Figure II.2  OTUk with alternative OTUkV FEC (OTUk-v)

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