The subnet mask parameter indicates the number of consecutive 1's in the subnet mask of the subnet to which the test set's sector belongs.
The subnet mask is a 128 bit number whose binary representation consists of "n" consecutive 1's followed by "128 - n" consecutive 0's. The subnet mask parameter sent by the access network indicates the number of consecutive 1's in the subnet mask; the access terminal can then determine the number of consecutive 0's in the subnet mask, and thus determine the 128 bit subnet mask value.
Subnet mask is sent in the Sector Parameters message (see TAP/ETAP Data Connection Call Flow ).
Subnet mask can be changed at any time.
GPIB Command: CALL[:CELL]:PARameter:SECTor:SMASk
Manual Operation: How Do I Change Cell Parameters?