# Description on the GCC byte mode of NG WDM products

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Question:
In the OTN architecture, the ESC mode is adopted. Sometimes, the GCC byte mode needs to be set using the :cm-set-fiberport command. The last parameter of this command indicates the channel rate. 13 denotes three-byte GCC0, 14 denotes the GCC12_9 byte, and 15 denotes the GCC12_18 byte. How are three-byte GCC0, GCC12_9, and GCC_18 calculated?
Root cause:
None
1. The channel rate is an equivalent rate. Three-byte GCC0 indicates that the bandwidth provided by GCC0 is 3 x 64K, and GCC12_9 indicates that the total bandwidth provided by GCC1 and GCC2 is 9 x 64K. In the OTN architecture, GCC0 is of two bytes, and the frame structure is always 4 x 4080 bytes.
2. At the 2.5G rate, the bandwidth of GCC0 is calculated using the following formulas:
Frame frequency = 2.5G/(4 x 4080 x 8)
Bandwidth of GCC0 = 2x frame frequency x 8
Therefore, the approximate bandwidth is as follows: 320K = 5 x 64K
Likewise, at the 5G and 10G rates, the approximate bandwidths are 10 x 64K and 20 x 64K respectively. (The length of an OTN frame is fixed, whereas the frame frequency varies.) Due to the limit on CPU channels, the bandwidth provided by GCC0 must be reduced so that the equipment can be used like the previous equipment. That is, GCC0 is used as three bytes only. To be specific, the supervisory bandwidth provided by GCC0 is 3 x 64K.
3. According to the preceding method, at the 2.5G rate, GCC1 and GCC2 together provide 10 x 64K bandwidth. That is, GCC1 and GCC2 are used as nine bytes. GCC1 and GCC2, which are always bound together when used, provide 20 x 64K bandwidth at the 5G rate and 40 x 64K bandwidth at the 10G rate.
Suggestion and conclusion:
The OTN-framed OTU board supports DCC types GCC0, GCC12_9, and GCC12_18. The OTN 2.5G board supports GCC0 and GCC12_9, and the OTN 5G and OTN 10G boards support GCC0 and GCC12_18.

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Querying of the reset records of NG WDM devices
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Product series of the WDM product family
Huawei WDM/OTN series end-to-end intelligent optical transport platforms are applicable to the backbone core layer, metro core layer, metro convergence layer, and metro edge access layer. These series platforms support universal switching and flexible grooming for OTN, SDH, and packet services, coherent technology-based, large-capacity, and ultra-long 100G and 40G transmission, WSS-based dynamic optical-layer grooming at ROADM sites, and the ASON/GMPLS control plane. Facilitated by these platforms, carriers can enjoy more flexible transmission, quicker service provisioning, more reliable network, and easier maintenance, therefore ensuring better services and generating more profits. OTN-based new-generation WDM products have the following product series: OptiX OSN 1800: It is mainly applicable to the metro edge layer, including the metro convergence layer and metro access layer. On small-capacity networks, it is also applicable to the core layer. OptiX OSN 3800: It is mainly applicable to the metro convergence layer and metro access layer. OptiX OSN 6800: It is applicable to long-haul backbone networks, regional backbone networks, local networks, the metro convergence layer, and the metro core layer. OptiX OSN 8800: It is mainly applicable to the backbone core layer, and is also applicable to the metro core layer and metro convergence layer. OptiX OSN 9800: It is developed to satisfy the requirements for ultra large capacities and bandwidth.

Whether Huawei NG WDM products support 16 CWDM wavelengths
Huawei NG WDM products support only eight CWDM wavelengths, but some optical-layer boards such as CMR2 and CMR4 support up to 16 wavelengths. Among the 16 wavelengths, eight are provided by NG WDM products and the other eight are provided by third-party equipment.

Functions of the RES and GCC bytes in the ASON domain
The OSPF and RSVP protocols transmit messages through the GCC or RES bytes in OTN overhead. Control links and control channels for the ASON are created in OTN overhead (electrical-layer ASON uses RES_ODU or GCC bytes) and DCC channels (optical-layer ASON uses D4 to D12 bytes).

Method used to check the condition of NG WDM service channels
A meter can be used to check the condition of NG WDM service channels. A PRBS test can also be used to check the condition at deployment.

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