Port-block allocation (deterministic NAT)
termISP & telecomgovernance & risk
Assigning each subscriber a fixed, predictable block of source ports for the duration of a session, and logging that assignment - rather than logging every individual translation as it happens.
It is the difference between a retention obligation that is affordable and one that is not: logging moves from per-flow to per-session, and attribution becomes arithmetic rather than a search through a flow database. That matters most where the output is a name given to a court, because a defensible answer requires address, port and timestamp together. The trade is that block size caps a subscriber's simultaneous connections, and an undersized block produces failures users report as random network faults.
Also known as: deterministic nat, port block, pba, log reduction