This read-create Unsigned32 (0-65535) specifies a Port-set ID value to use in preference to the one derived from the Embedded Address bits, with only the high-order PSIDLength bits actually used and the parameter ignored entirely when PSIDLength is zero. An admin sets this when a subscriber's port-set needs to be explicitly assigned rather than algorithmically derived from their IPv6 prefix. For example, overriding the PSID lets an operator manually assign a specific port range to a subscriber whose EA-bits would otherwise compute a conflicting port-set.