Description: 
Forwarding port list
1. OLT
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It is presented by member port list. Each member port is identified
by 4-byte format, same as TC of EponDeviceIndex. The actual length of
this string depends of the number of member ports in the port list.
The relationship is:
Length of the string = 4 * (NUM of member ports)  
For example, if device 1, port 1/2 and 2/3 is the member ports, 
then this object will be presented as:
01 01 02 00 01 02 03 00

2. ONU
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It is presented by member port list. Each member port is identified
by 2-byte format, One for slot ID, the last for port ID. The actual 
length of this string depends of the number of member ports. If the 
ONU is fixed (not modulized), set slot ID to 0, the NMS could ignore 
the slot info.
Note that, slot here shall follow the last byte definition of 
EponCardIndex to indicate the main-slot and sub-slot index.  
The relationship is:
Length of the string = 2 * (NUM of member ports)  
For example, if port 1/2 and 3/4 is the member ports of the group, 
then the object is presented as:
01 02 03 04