1. OTN Overview & Update
Jean-Marie Vilain
Product Specialist

2. Agenda OTN Sonet Overview OTN Overview OTN update Ethernet over OTN
What’s next…

3. SONET-SDH structure
Sonet / SDH technologies have been out for a while now, the main goal was to transport digital information over fiber, but also support electrical lower rate communication signal
overhead
payload
overhead
payload

4. SONET / SDH supported transport rate
SONET-SDH structure
SONET / SDH supported transport rate

5. SONET-SDH structure VCAT/LCAS VCAT/LCAS and GFP offered
Automatic Flexible bandwidth and
Clear way to map Ethernet traffic
In to Sonet

6. Virtual Concatenation Bandwidth Efficiency
100%
Efficiency Increase
67%
This table shows the improvements in bandwidth efficiency that can be made by using virtual concatenation instead of contiguous concatenation.
For example, traditionally with contiguous concatenation an STS-3c or VC-4 will be used to transport 100 Mb/s fast Ethernet service. This equates to a bandwidth efficiency of 67%. By using virtual concatenation, we can use 2x STS-1s or VC-3s to carry the same service and the bandwidth efficiency rockets to 100%!
Even larger efficiency improvements can be made with some other data services.

7. GFP
VCAT/LCAS
Ethernet map into SDH/SONET
Using GFP

8. WDM Transmission Services Layer SDH/SONET Layer Optical layer
Delivery of services to
end customers.
SDH/SONET Layer
High-speed protection/restoration.
Time division multiplexing
ADM
ADM
ADM
DXC
ADM
ADM
ADM
ADM
ADM
ADM
ADM
WDM fiber
WDM
WDM
Optical layer
Wavelength division multiplexing
High level protection
Traditional DWDM networks are point to point and utilized in high capacity links.
The OTN enables DWDM ring and mesh networks, with the opportunity for dynamic payload provisioning and reconfiguration of traffic routing.
WDM fiber
WDM
WDM
WDM line system
WDM line system
for fiber saving

9. ITU G.709 is the OTN Standard
Why OTN
ITU G.709 is the OTN Standard

10. Why OTN

11. Why OTN

12. OTN mapping structure
We can see from the slide that the frame format is very similar to SONET/SDH and that should be no surprise, as G.709 attempts to take the best features of SONET/SDH.
It should be noted that the OTN frame is much smaller than the 10G SONET/SDH frame.

13. OTN Frame Format
We can see from the slide that the frame format is very similar to SONET/SDH and that should be no surprise, as G.709 attempts to take the best features of SONET/SDH.
It should be noted that the OTN frame is much smaller than the 10G SONET/SDH frame.

14. OTN Overhead structure
The FAS/MFAS provides frame alignment.
The Section Monitoring provides Error detection and communication
The ODU overhead brings TCM support, Communication channels and Automatic protection switching
The OPU overhead adapt the client signal to the optical channel, specifying the type of client signal in the payload

15. Why the use of OTN over SONET/SDH
OTN provide better TCM support Over-multiple Carriers.
SDH/SONET only support one TCM vs. 6 TCM for OTN

16. Forward Error Correction (FEC)
FEC provides the following benefits.
Improves the BER performance of an existing link
Increases the maximum span of a link can extend up to 20km and remove the need of regenerator
Improves the overall quality of the link by diagnosing link problems earlier
At 10Gb/s there is less optical margin in terms of BER for the same optical power at 2.5Gb/s. This can be compensated for by increasing the optical power or reducing the span.
Another approach is to use Forward Error Correction (FEC) in connection with 10Gb/s and above. FEC can increase the optical margin without boosting power margins or reducing the span.
RS(255,239). For the FEC processing a OUT row is separated into 16 sub-rows using byte-interleaving. Each FEC encoder/decoder processes one of these sub-rows. The FEC parity check bytes are calculated over the information bytes 1 to 239 of each sub row and transmitted in bytes 240 to 255 of the same sub-row.

17. ITU G.709 Sup 43 Over-Clocked OTN rates OTU1e – OTU2e
The goal here, is to combine multiple 10GE ports from the Core router directly into OTN.
Not to be confused with OTU1 which is a 2.7 Gbit/s signal, these are 10G rates
Not a big issue with 10GE Wan (9.953 Gb/s) where the signal can be directly map into an OPU2 container
This is more a problem with the 10GBASE-R 10GE LAN, where there’s a size mismatch between the containers.

18. Over-clocked OTU3 - OTU3e1
OTU3e1 OH
OPU3e1 = 41.56Gbps
FEC
Defined in ITU-T G.709 Sup43 Sec9.1
OTU3e1 supports nominal bit rate of 44.57Gbps +/- 20ppm
The OPU3e1 is divided into 16 x 2.5G tributary slots (TSs) interleaved within the OPU3e1 payload area
OTU3e1 is key for asynchronous bit-transparent mapping of 4 x ODU2e signals

19. Over-clocked OTU3 - OTU3e2
Defined in ITU-T G.709 Sup43 Sec9.2
OTU3e2 supports nominal bit rate of 44.58Gbps +/- 20ppm
The OPU3e2 is divided into 32 tributary slots (TS) of approximately 1.25Gbps; interleaved within the payload area
OTU3e2 uses Generic Mapping Procedure (GMP) for mapping 4 x ODU2e signals into OPU3e2 payload area
OTU3e2 OH
OPU3e2 = 41.61Gbps
FEC
ODU2e
ODTU3e2.8 x4
ODTUG3e2
PT=21 x1
ODU3e2
(H)
Mapping
MUXing
OTU3e2

20. Ethernet in Carrier Networks EoOTN
10/100M Ethernet link
OTU2
Access Routers
ODU MUX
Access Routers
OTU1
GigE link
OTU2 , OTU3
or even OTU4
MSPP
OTU1
ODU1 mux in ODU2
MSPP
OTU2
1GigE in ODU0 in OTU1
Access Routers
Access Network
OTU1 with ODU0
ENIU

21. Client Interface cards
100M/GbE
10GbE FC
SONET/SDH
10.7G OTN
(G.709)
DWDM
& OLA
Powerful
Unframed/ frame testing
SONET/SDH (10G)
OTN (OTU1/2/1e/2e) with FEC
10/100/1000BaseT, Gig-E & 10G Ethernet
1x/2x/4x/10x FC
8130NGE
Transponder cards
Proper provisioning
Power levels
Bit Error Rate tests
FEC (OTN)

22. New ODU 0 OTN container
ODU0 is a new container size that has been introduced in the G.709 to accommodate efficient transport of Gigabit Ethernet (1.25 Gb/s). OTU1 was not efficient for 1GbE signal with a payload rate of Gb/s
ODU0 is half the size of an ODU1 container i.e = Gb/s
Gigabit Ethernet does not fit in the OPU0 payload, GMP will be use to insert the Gigabit Ethernet rate inside OPU0 rate
Note: ODU0 does not have a physical instance (i.e. there is no OTU0), the signal needs to be multiplexed into a higher layer in order to be transported on the OTN network

23. ODU0 New ODU 0 OTN container
New multiplexing method1 that allows direct ODU0 multiplexing into ODUk (k=2,3,4) in a single stage
This multiplexer uses Generic Mapping Procedure (GMP) for ODU0 justification control
Where GMP will support various client signals and future new ones. It is a generic procedure for mapping a client signal with any bit rate less than the payload capacity to the ODU.

24. Technology Overview ODU
ODU0 mapping?
The mapping of a ODU0 into a ODU1 is done using ODTU01 (optical channel data unit tributary ) where the ODU1 structure is divided into two sections and where both ODU0 are map. Each needed ODU0 are mapped in to the payload using GMP to specific timeslot.

25. Technology Overview
Any client signal can be map into the payload using the below process, where each low order signal will mux into a timeslot and be insert in to the payload

26. ODUflex is a new OTN variable container introduce in October 2009
Allows for flexible ODU rates for transparent transport of any client signal, it used a similar process to VCAT except that there is no delay because the signal is map in to the same physical container
Adapted in 2 ways:
For Constant Bit Rate (CBR)client signals
Rate = 239/238 x CBR rate
For GFP-F mapped packet client signals
Rate = N x ~1.25Gbit/s (ODU0) with 1 ≤ N ≤ 80

27. 40GE/100GE Mapping into OTN
Wide-area Ethernet transport technologies are necessary to support, for example, the connection of Ethernet switches separated by more than 40 km (typical distance supported by Ethernet standards).
ITU-T SG15 is responsible for OTN standardization and IEEE 802.3ba is responsible for 40G/100G Ethernet standardization; both working closely to develop 40GE/100G transport capability over OTN

28. 40GE/100GE Mapping into OTN 40GE with 64B/66B Transcoding 41.25G
Using 1024B/1027B G
40.117G
100GE
40GE
GMP
GMP
ODU4 G OH G
ODU3
40.319G OH G 1x 1x
OTU4
OTU3
Standard 40GE runs at 41.25Gbps and OPU3 payload is only Gbps
Therefore, mapping 40GE over OTU3 requires 1024/1027B transcoding adaptation to reduce 40GE coded rate

29. OTN OTL (OTU3/OTU4) New OTUk & bit rate OTU3 = 43Gb/s OTU4 = 112Gb/s
Client
OTUk & bit rate
OTU3 = 43Gb/s
OTU4 = 112Gb/s
OPU OH
OCh Payload Unit (OPU) Payload
ODUOH
OCh Data Unit (ODU) Payload
OTU OH
OCh Transport Unit (OTU) Payload
FEC
OTUk signal is transmitted over n lanes
OTLk.n
OTLk.n
OTLk.n
OTL type & bit rate
OTL3.4 = 10.7Gb/s
OTL4.4 = 27 95Gb/s
OTL4.10 = 11.18Gb/s 1
 2
 n

30. Traditional OTN Structure

31. New OTN Structure