What is PT = 0x21 for OTN Applications?

This post discusses and describes the PT = 21 Method for Mapping and Multiplexing Lower-Speed ODUj signals into a Higher-Speed ODUk Signal.

Mapping/Multipllexing Lower-Speed ODUj Tributary Signals into a Higher-Speed ODUk Server Signal

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What is PT (Payload Type) = 0x21 for OTN Applications, and what does it Mean?

Whenever we are mapping/multiplexing lower-speed ODUj signals into a higher-speed ODUk signal, for up to the ODU3 rate, we have the following two options:

  • Use the PT = 20 (or 0x20) Method for Mapping/Multiplexing the ODUj tributary signals into the ODUk, or
  • Use the PT = 21 (or 0x21) Method for Mapping/Multiplexing the ODUj tributary signals into the ODUk.

If you wish to map/multiplex some lower-speed ODUj signals into an ODU4 signal, then you MUST use the PT  = 21 (ox21) approach.

NOTE:  We discuss the PT = 21 Approach (for mapping/multiplexing) some lower-speed ODUj tributary signals into an ODU4 in Lesson 5/ODU4 within THE BEST DARN OTN TRAINING PRESENTATION…PERIOD!!!

What is the PT = 21 Method?

Whenever we use the PT = 21 Method, we will set the PT byte (within the PSI Message) to the value 0x21 within this OPUk/ODUk signal.

The PT = 21 Method for Mapping/Multiplexing of ODUj signals into an ODUk signal has the following characteristics.

  • We do Mapping/Multiplexing with 1.25Gbps time-slots (instead of the 2.5Gbps time-slots for PT = 20).
  • In most cases, we use GMP to map the ODUj signal into the ODTUk.ts or ODTUjk structures.
  • However, we do use AMP as the mapping procedure in some cases.

Is the PT = 21 Method better than PT = 20 Method?

The PT = 21 Method is the newer standard and is (therefore) the preferred approach.

For example, for 2-Fibre/2-Lambda Shared-Ring Protection-Switching applications, ITU-T G.873.2 strongly recommends that the System Designer use the PT = 21 methods for combining the Working and Protection time-slots into a single ODUk signal.

Please see the 2-Fibre/2-Lambda Shared-Ring Protection-Switching post for more information on this topic.

What Mapping/Multiplexing Schemes can one use for the PT = 21 Method for Mapping/Multiplexing ODUj Signals into an ODUk Signal?

I summarize the Mapping/Multiplexing scheme information for each of the PT = 21 Cases (for Mapping/Multiplexing Numerous Lower-Speed ODUj signals into a Higher-Speed ODUk signal) in Table 1 below.

Table 1, Summary of Schemes for Mapping/Multiplexing Multiple Lower-Speed ODUj Signals into a Higher-Speed ODUk Signal, PT = 0x21

ODUj SignalMapping StructureMapping MethodNumber of ODUj SignalsIntermediate StructureODUk/OPUk Signal
ODU0ODTU2.1GMP8ODTUG2ODU2/OPU2
ODUflexODTU2.tsGMP1 to 8ODTUG2ODU2/OPU2
ODU1ODTU12AMP4ODTUG2ODU2/OPU2
ODU0ODTU3.1GMP32ODTUG3ODU3/OPU3
ODUflexODTU3.tsGMP1 to 32ODTUG3ODU3/OPU3
ODU1ODTU13AMP16ODTUG3ODU3/OPU3
ODU2ODTU23AMP4ODTUG3ODU3/OPU3
ODU2eODTU3.9GMP3ODTUG3ODU3/OPU3
ODU0ODTU4.1GMP80ODTUG4ODU4/OPU4
ODUflexODTU4.tsGMP1 to 80ODTUG4ODU4/OPU4
ODU1ODTU4.2GMP40ODTUG4ODU4/OPU4
ODU2ODTU4.8GMP10ODTUG4ODU4/OPU4
ODU2eODTU4.8GMP10ODTUG4ODU4/OPU4
ODU3ODTU4.31GMP2ODTUG4ODU4/OPU4

I have also drawn out these cases below as well.

  • ODU0 ⇒ ODTU2.1 ⇒ ×8 ⇒ ODTUG2 ⇒ OPU2 ⇒ ODU2

This scheme will map/multiplex as many as 8 ODU0 signals into an ODU2 signal.

ODU0 to ODU2 - Using PT = 21 Method

Figure 1, Simple Illustration of the ODU0 -> ODU2 Multiplexing/Mapping scheme

Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (COMING SOON).

 

  • ODU1 ⇒ ODTU12 ⇒ ×4 ⇒ ODTUG2 ⇒ OPU2 ⇒ ODU2

This scheme will allow one to map/multiplex as many as 4 ODU1 signals into an ODU2 signal.

ODUflex to ODU4 - Using PT = 21 Method

 

Figure 2, Simple Illustration of the ODU1 -> ODU2 Multiplexing/Mapping scheme.

Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (COMING SOON).

 

  • ODUflex ⇒ ODTU2.ts ⇒ ×8/ts ⇒ ODTU2G ⇒ OPU2 ⇒ ODU2

This scheme will allow one to map/multiplex anywhere from 1 to 8 ODUflex signals into an ODU2 signal.

ODUflex to ODU2 - Using PT = 21 Method

Figure 3, Simple Illustration of the ODUflex ⇒ ODU2 Multiplexing/Mapping scheme.

Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (COMING SOON).

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  • ODU0 ⇒ ODTU3.1 ⇒ ×32 ⇒ ODTUG3 ⇒ OPU3 ⇒ ODU3

This scheme will allow one to map/multiplex as many as 32 ODU0 signals into an ODU3 signal.

ODU0 to ODU3 - Using PT = 21 Method

Figure 4, Simple Illustration of the ODU0 ⇒ ODU3 Mapping/Multiplexing scheme

Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (COMING SOON).

 

  • ODU1 ⇒ ODTU13 ⇒ ×16 ⇒ ODTUG3 ⇒ OPU3 ⇒ ODU3

This scheme will allow one to map/multiplex as many as 16 ODU1 signals into an ODU3 signal.

ODU1 to ODU3 - Using PT = 21 Method

 

Figure 5, Simple Illustration of the ODU1 ⇒ ODU3 Mapping/Multiplexing scheme.

Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (COMING SOON).

 

  • ODU2 ⇒ ODTU23 ⇒ ×4 ⇒ ODTUG3 ⇒ OPU3 ⇒ ODU3

This scheme will allow one to map/multiplex as many as 4 ODU2 signals into an ODU3 signal.

ODU2 to ODU3 - Using PT = 21 Method

Figure 6, Simple Illustration of the ODU2 ⇒ ODU3 Mapping/Multiplexing scheme.

Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (COMING SOON).

 

  • ODU2e ⇒ ODTU3.9 ⇒ ×3 ⇒ ODTUG3 ⇒ OPU3 ⇒ ODU3

This scheme will allow one to map/multiplex as many as 3 ODU2e signals into an ODU3 signal.

ODU2e to ODU3 - Using PT = 21 Method

Figure 7, Simple Illustration of the ODU2e ⇒ ODU3 Mapping/Multiplexing scheme. 

Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (COMING SOON).

 

  • ODUflex ⇒ ODTU3.ts ⇒ ×32/ts ⇒ ODTUG3 ⇒ OPU3 ⇒ ODU3

This scheme will allow one to map/multiplex anywhere from 1 to 32 ODUflex signals into an ODU3 signal.

ODUflex to ODU3 - Using PT = 21 Method

Figure 8, Simple Illustration of the ODUflex ⇒ ODU3 Mapping/Multiplexing scheme.  

Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (COMING SOON).

 

  • ODU0 ⇒ ODTU4.1 ⇒ ×80 ⇒ ODTUG4 ⇒ OPU4 ⇒ ODU4

This scheme will allow one to map/multiplex as many 80 ODU0 signals into an ODU4 signal.

ODU0 to ODU4 - Using PT = 21 Method

Figure 9, Simple Illustration of the ODU0 ⇒ ODU4 Mapping/Multiplexing scheme.  

Click HERE or click on the figure above to learn more about this Mapping/Multiplexing scheme.

 

  • ODU1 ⇒ ODTU4.2 ⇒ ×40 ⇒ ODTUG4 ⇒ OPU4 ⇒ ODU4

This scheme will allow one to map/multiplex as many as 40 ODU1 signals into an ODU4 signal.

ODU1 to ODU4 - Using PT = 21 Method

Figure 10, Simple Illustration of the ODU1 ⇒ ODU4 Mapping/Multiplexing scheme.

Click HERE or Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (*).

 

  • ODU2 ⇒ ODTU4.8 ⇒ ×10 ⇒ ODTUG4 ⇒ OPU4 ⇒ ODU4

This scheme will allow one to map/multiplex as many as 10 ODU2 signals into an ODU4 signal.

ODU2 to ODU4 - Using PT = 21 Method

Figure 11, Simple Illustration of the ODU2 ⇒ ODU4 Mapping/Multiplexing scheme.

Click HERE or Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (*).

 

  • ODU2e ⇒ ODTU4.8 ⇒ ×10 ⇒ ODTUG4 ⇒ OPU4 ⇒ ODU4

This scheme will allow one to map/multiplex as many as 10 ODU2e signals into an ODU4 signal.

ODU2e to ODU4 - Using PT = 21 Method

Figure 12, Simple Illustration of the ODU2e ⇒ ODU4 Mapping/Multiplexing scheme.  

Click HERE or Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (*).

 

  • ODU3 ⇒ ODTU4.31 ⇒ ×2 ⇒ ODTUG4 ⇒ OPU4 ⇒ ODU4

This scheme will allow one to map/multiplex as many as 2 ODU3 signals into an ODU4 signal.

ODU3 to ODU4 - Using PT = 21 Method

Figure 13, Simple Illustration of the ODU3 ⇒ ODU4 Mapping/Multiplexing scheme.

Click HERE or Click on the figure above to learn more about this Mapping/Multiplexing scheme.  (*).

 

  • ODUflex ⇒ ODTU4.ts ⇒ ×80/ts ⇒ ODTUG4 ⇒ OPU4 ⇒ ODU4

This scheme will allow one to map/multiplex anywhere from 1 to 80 ODUflex signals into an ODU4 signal.

ODUflex to ODU4 - Using PT = 21 Method

Figure 14, Simple Illustration of the ODUflex ⇒ ODU4 Mapping/Multiplexing scheme.  

Click HERE or Click on the figure above to learn more about this Mapping/ Multiplexing scheme.  (*).

NOTE:  (*) – Indicates that you must be a member of the THE BEST DARN OTN TRAINING PRESENTATION…PERIOD!!  program to see this link.

In Conclusion

In this posting, we briefly listed the characteristic of a PT = 21 scheme for Mapping/Multiplexing multiple lower-speed ODUj tributary signals into a higher-speed ODUk server signal.

We have also listed out each of the 14 PT = 21 schemes for Mapping/Multiplexing multiple lower-speed ODUj signals into a higher-speed ODUk signal.

Please check out the relevant post for similar information on PT = 20 schemes on Mapping/Multiplexing multiple lower-speed ODUj signals into a higher-speed ODUk signal.

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Author: Darrell Smith

Darrell Smith has more than 30 years of experience as an Electrical Engineer. He has about 20 years of experience as an Applications Engineer and the remainder of his time was spent in Hardware Design and Product Marketing. He will now be sharing his wealth of knowledge on this blog.

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