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G.709

From Wikipedia, the free encyclopedia
ITU-T recommendation
Internet protocol suite
Application layer
Transport layer
Internet layer
Link layer
G.709
Interfaces for theOptical Transport Network (OTN)"
StatusIn force
Year started2001
Latest version6.0
June 2020
OrganizationITU-T
LicenseFreely available
Websitehttps://www.itu.int/rec/T-REC-G.709

ITU-T Recommendation G.709Interfaces for theOptical Transport Network (OTN) describes a means of communicating data over an optical network.[1] It is a standardized method for transparent transport of services over optical wavelengths inDWDM systems. It is also known as Optical Transport Hierarchy (OTH) standard. The first edition of this protocol was approved in 2001.[2]

The G.709 OTUk signal is positioned as a server layer signal for various client signals, e.g.SDH/SONET,ATM,IP,Ethernet,Fibre Channel andOTNODUk (where k=0, 1, 2, 2e, 3, 3e2, 4 or flex).[3] Work on support forInfiniBand andCommon Public Radio Interface client signals is currently[when?] in progress.

The frame structure defined in G.709 is constructed of 4 areas:

  1. OPUk[3] is the area in which payload is mapped.
  2. ODUk[3] contains the OPUk with additional overhead bytes (e.g. TTI,BIP8,GCC1/2, TCM etc.).
  3. OTUk[3] is the section and includes framing, TTI, BIP8 andGCC0 bytes.
  4. FEC – The standard FEC code (described inG.975) is aReed–Solomon coding calculated across the payload (OPU) columns. This allows detection and correction of bit errors due to signal impairments during transmission. The FEC code also extends the distance the optical signal can travel before requiring regeneration.

G.709 offers advancedOAM&P capabilities such asTandem Connection Monitoring (TCM), End to End performance monitoring, connectivity monitoring, signal quality supervision andGeneral Communication Channel (GCC).

Typical client signals and corresponding G.709 rates

[edit]
Client Signal TypeClient SignalOTN Line Signal (G.709)OTUk Line Rate (kbit/s)[4]OPUk Payload Rate (kbit/s)[4]OTUk frame period (μs)OTUk frequency accuracy (ppm)
SONET/SDHSTS-48/STM-16OTU12,666,0572,488,32048.971± 20
SONET/SDHSTS-192/STM-64OTU210,709,22510,037,62912.191± 20
Ethernet/Fibre Channel10GBASE-R/10GFCOTU2e11,095,72710,356,01211.766±100
SONET/SDH/EthernetSTS-768/STM-256/Transcoded40GBASE-ROTU343,018,41340,150,5193.034±20
EthernetUp to 410GBASE-ROTU3e244,583,35541,611,1312.928±20
Ethernet100GBASE-ROTU4111,809,973100,376,2981.167±20

Unlike SDH/SONET, the line rate is increased by maintaining the G.709 frame structure (4 rows x 4080 columns) and decreasing the frame period (in SDH/SONET the frame structure is increased and the frame period of 125 μs is maintained).

Notes and references

[edit]
  1. ^"ITU standards enhance capabilities of the Optical Transport Network".www.itu.int.Archived from the original on 2021-04-09. Retrieved2021-04-09.
  2. ^"G.709: Interfaces for the optical transport network".www.itu.int.Archived from the original on 2021-06-15. Retrieved2021-06-15.
  3. ^abcdThe letterk represents the ODUk data rate as follows:
    0 = ~1.24 Gbit/s
    1 = ~2.50 Gbit/s
    2 = ~10.04 Gbit/s
    2e = ~10.40 Gbit/s
    3 = ~40.32 Gbit/s
    3e2 = 41.79 Gbit/s
    4 = ~104.79 Gbit/s
    flex = a multiple of ~1.24 Gbit/s
  4. ^abFractional portion is truncated

See also

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External links

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