Functions of the RES and GCC bytes in the ASON domain

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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).

Other related questions:
Description on the GCC byte mode of NG WDM products
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 Answer: 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.

Whether multiple primary NEs can be managed like GNEs in an ASON domain
You can set only one primary NE and one secondary NE in an ASON domain. The NMS only needs to communicate with one NE on an ASON network. This NE is called the communication NE. It is the NE that represents the ASON network to communicate with the NMS. Usually, the communication NE is the primary NE. When the primary NE fails, the secondary NE becomes the communication NE. If both the primary and secondary NEs fail, the system automatically selects an ASON NE as the communication NE.

Reason why the recommended usage status of ASON overhead bytes is set to "Disabled" for tributary boards when electrical-layer ASON features are enabled on an ASON network
For electrical-layer ASON, tributary boards cannot transmit ASON management bytes. Therefore, you are advised to set the usage status of ASON overhead bytes to "Disabled" for the tributary boards.

Whether multiple primary NEs that function similar to gateway NEs can be created in an ASON domain
Only one primary NE and one secondary NE can be created in an ASON domain. The U2000 server needs to establish a connection with either the primary or secondary NE. The NE that establishes a connection with the U2000 is called the gateway NE and implements communication between the ASON network and the U2000 server. In normal cases, you are advised to configure the primary NE as the communication NE. When the primary NE fails, the secondary NE becomes the communication NE. If both the primary and secondary NEs fail, the system automatically selects an ASON NE as the communication NE.

Reason why CSPF is used on ASON networks
Constraint Shortest Path First (CSPF) is a routing algorithm that calculates the optimal route for a service, ensuring that the service is quickly restored after rerouting.

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