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  • G.709 7.3. Bit Rates and Capacity Q1/Q2

    From krishna G@21:1/5 to All on Tue Jan 5 00:21:26 2016
    Hi Hubb,

    Happy New Year again.

    I have 2 questions reg the sec 7.3 of G.709 (Bit rates and capacity)

    Q1 .

    When OTN was introduced , it is designed for STM16,STM64,STM256.

    Hence I can understand OPU1 is designed to be 2.488Gbps since STM16 is 2.488Gbps.

    But why is OPU2 238/237*9.953Gbps when STM64 is 9.953 Gbps ?? why not opu2 is 9.953gbps?? what is the need to use fixed stuff bytes for OPU2 and OPU3??

    Q2.

    Again when OPU0 is designed for 1Gbe.why is ODU0 considered as the base rate 1244160 kbps. and OPU0 is 238/239 * 1244160Kbps. which is unlike STM16/OPU1.

    I expect OPU0 to be designed for the payload rate and ODU0 to be considered accordingly.

    Thanks
    Krishna

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  • From Huub van Helvoort@21:1/5 to You on Fri Jan 8 12:51:17 2016
    Hello Krishna,

    You wrote:

    I have 2 questions reg the sec 7.3 of G.709 (Bit rates and capacity)

    Q1 .
    When OTN was introduced , it is designed for STM16, STM64, STM256.
    Hence I can understand OPU1 is designed to be 2.488Gbps since STM16
    is 2.488Gbps. But why is OPU2 238/237*9.953Gbps when STM64 is 9.953
    Gbps ?? why not opu2 is 9.953gbps?? what is the need to use fixed
    stuff bytes for OPU2 and OPU3??

    SDH uses 9 rows, OTN uses 4 rows and the mapping is per byte.
    The OPUk, ODUk and OTUk overhead remains the same for every value of k.
    This is different from SDH where the overhead increases with increased bit-rates.
    So to convert and map an SDH frame structure in the OTN frame structure
    the 238/237 factor had to be used.

    Q2.
    Again when OPU0 is designed for 1Gbe.why is ODU0 considered as the
    base rate 1244160 kbps. and OPU0 is 238/239 * 1244160Kbps. which is
    unlike STM16/OPU1. I expect OPU0 to be designed for the payload rate
    and ODU0 to be considered accordingly.

    ODU1 was defined long before the introduction of ODU0.
    ODU0 was (proposed by me) added to be able to support
    the increasing demand for transporting 1GbE efficiently.

    Best regards, Huub.


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  • From Michelot@21:1/5 to All on Sat Jan 9 03:45:48 2016
    Bonjour Huub and Krishna, gelukkig nieuwjaar


    So to convert and map an SDH frame structure in the OTN frame structure
    the 238/237 factor had to be used.

    I would also think that (in 2001) we could map 4 x ODU1 with STM-16 mapped inside an OPU2 payload.

    So we need to insert the 4 x 16 columns of ODU1 overhead together with the 4 x STM-16 bytes.

    This is done by adding in OPU2 payload 16 columns more than STM-64, due to support these ODU1.

    It would lead to the 238/237 factor.

    Cordialement,
    Michelot

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