Final answer:
The Network ID in the Internet Protocol (IPv6) global unicast address format is 64 bits.
Step-by-step explanation:
The Network ID in the Internet Protocol (IPv6) global unicast address format is 64 bits.
In the IPv6 address format, the first 64 bits represent the network ID portion, while the remaining 64 bits represent the interface ID portion. The network ID identifies the network to which the device is connected, while the interface ID identifies the specific device on that network.
For example, in the IPv6 address 2001:0db8:85a3:0000:0000:8a2e:0370:7334, the first 64 bits (2001:0db8:85a3:0000:0000:0000:0000:0000) represent the network ID.