This read-write OCTET STRING (0 to 20 bytes) is relevant only for inter-network gateway ports, used to replace the calling party number when egress address translation is configured to the appropriate mode, coded as 1-15 ASCII octets for E.164 or 20 binary octets for ATM-endsystem addresses. This lets an admin present a different (e.g., network-owned gateway) calling address to the far network rather than exposing the original internal caller's real address, similar in purpose to NAT for telephony/ATM signaling. An engineer configuring calling-party privacy at a network boundary would set svcPrefixLocalGatewayAddress to the gateway's own published number so outbound calls appear to originate from the gateway rather than revealing internal caller addresses.