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2 Transport aspects

20.5 Mapping ODUk into ODTUCn.ts

The mapping of ODUk (k = 0, 1, 2, 2e, 3, 4, flex) signals (with up to 100 ppm bit-rate tolerance) into the
ODTUCn.ts (ts = M) signal is performed by means of a generic mapping procedure as specified in Annex D.
The OPUCn and therefore the ODTUCn.ts signals are created from a locally generated clock (within the
limits specified in Table 7-3), which is independent of the ODUk signal.
The ODUk signal is extended with a frame alignment overhead as specified in clauses 15.6.2.1 and 15.6.2.2
and an all-0s pattern in the OTUk overhead field (see Figure 19-22, read "j" by "k").
The extended ODUk signal is adapted to the locally generated OPUCn/ODTUCn.ts clock by means of a
generic mapping procedure (GMP) as specified in Annex D. The value of n in cn and Cn(t) and CnD(t) is
specified in Annex D. The value of M is the number of tributary slots occupied by the ODUk; ODTUCn.ts =
ODTUCn.M.

A group of M successive extended ODUk 16-byte (128-bit) words is mapped into a group of M successive
ODTUCn.M 16-byte (128-bit) words.

NOTE 1 – The 16-byte word alignment of the extended ODUk is preserved through the mapping procedure; e.g., the
position of the first 16 OH bytes of the ODUk is always located after an integer number of 16-byte words from the
start of the ODTUCn.M structure.

The generic mapping process generates for the case of ODUk signals once per ODTUCn.M multiframe the
Cm(t) and CnD(t) information according to Annex D and encodes this information in the ODTUCn.ts
justification control overhead JC1/JC2/JC3 and JC4/JC5/JC6. The de-mapping process decodes Cm(t) and
CnD(t) from JC1/JC2/JC3 and JC4/JC5/JC6 and interprets Cm(t) and CnD(t) according to Annex D. CRC-6 shall
be used to protect against an error in bits 3 to 8 of the JC1,JC2,JC3 signals. CRC-9 and Odd Parity shall be
used to protect against an error in bits 1 and 2 of JC1, JC2, JC3 and bits 1 to 8 of JC4,JC5, JC6 signals.

During a signal fail condition of the incoming ODUk signal, this failed incoming signal will contain the ODUk-
AIS signal as specified in clause 16.5.1. This ODUk-AIS is then mapped into the ODTUCn.M.

For the case where the ODUk is received from the output of a fabric (ODU connection function), the
incoming signal may contain (in the case of an open matrix connection) the ODUk-OCI signal as specified
in clause 16.5.2. This ODUk-OCI signal is then mapped into the ODTUCn.M.
NOTE 2 – Not all equipment will have a real connection function (i.e., switch fabric) implemented; instead, the
presence/absence of tributary interface port units represents the presence/absence of a matrix connection. If such a
unit is intentionally absent (i.e., not installed), the associated ODTUCn.M signals should carry an ODUk-OCI signal. If
such a unit is installed but temporarily removed as part of a repair action, the associated ODTUCn.M signal should
carry an ODUk-AIS signal.

A group of M successive extended ODUk 16-byte words is de-mapped from a group of M successive
ODTUCn.M 16-byte blocks.

NOTE 3 – For the case where the ODUk signal is output as an OTUk signal, frame alignment of the extracted extended
ODUk signal is to be recovered to allow frame synchronous mapping of the ODUk into the OTUk signal.
During a signal fail condition of the incoming ODUCn/OPUCn signal (e.g., in the case of an ODUCn-AIS
condition) the ODUk-AIS pattern as specified in clause 16.5.1 is generated as a replacement signal for the
lost ODUk signal.
The values of M, m, Cm,min, Cm,max, n, Cn,min and Cn,max for ODUk into ODTUCn.ts are as follows:

 ODUk _ nom _bit _ rate  1( ODUk _bit _ rate _tolerance  00006.0  ) for ODUk with k ≠ flex(GFP) (20-1a)
M  ceiling    
 (ODTUCn 1 . _ nom _bit _ rate  1( ODTUCn .ts _bit _ rate _tolerance  )
 ODUk _bit _ rate 
M  ceiling   for ODUk with k = flex(GFP) (20-1b)


 ODUk .ts _bit _ rate 4 
m 128  M (20-2)

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