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 Signal | Mapping Structure | Mapping Method | Number of ODUj Signals | Intermediate Structure | ODUk/OPUk Signal |
|---|---|---|---|---|---|
| ODU0 | ODTU2.1 | GMP | 8 | ODTUG2 | ODU2/OPU2 |
| ODUflex | ODTU2.ts | GMP | 1 to 8 | ODTUG2 | ODU2/OPU2 |
| ODU1 | ODTU12 | AMP | 4 | ODTUG2 | ODU2/OPU2 |
| ODU0 | ODTU3.1 | GMP | 32 | ODTUG3 | ODU3/OPU3 |
| ODUflex | ODTU3.ts | GMP | 1 to 32 | ODTUG3 | ODU3/OPU3 |
| ODU1 | ODTU13 | AMP | 16 | ODTUG3 | ODU3/OPU3 |
| ODU2 | ODTU23 | AMP | 4 | ODTUG3 | ODU3/OPU3 |
| ODU2e | ODTU3.9 | GMP | 3 | ODTUG3 | ODU3/OPU3 |
| ODU0 | ODTU4.1 | GMP | 80 | ODTUG4 | ODU4/OPU4 |
| ODUflex | ODTU4.ts | GMP | 1 to 80 | ODTUG4 | ODU4/OPU4 |
| ODU1 | ODTU4.2 | GMP | 40 | ODTUG4 | ODU4/OPU4 |
| ODU2 | ODTU4.8 | GMP | 10 | ODTUG4 | ODU4/OPU4 |
| ODU2e | ODTU4.8 | GMP | 10 | ODTUG4 | ODU4/OPU4 |
| ODU3 | ODTU4.31 | GMP | 2 | ODTUG4 | ODU4/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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 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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