Realm-Specific Internet Protocol

: RSIP also stands for Radar System Improvement Program , see E-3 Sentry.

Realm-Specific Internet Protocol is an IP address translation technique that is an alternative to Network address translation. RSIP lets an enterprise possess many private addresses behind a single public Internet address.

RSIP functions by leasing public IP addresses and ports to RSIP hosts located in private addressing realms. The RSIP client requests registration with an RSIP server, or gateway. The server in turn delivers either a unique public IP address or a shared public IP address and a unique set of TCP/UDP ports and attaches the RSIP host private address to this public address. The RSIP host uses this public address to send packets to public destinations. The packets contain both the public and private addresses, and the RSIP server strips off the private address header and sends the packet on with a public IP header.

RSIP can also be used to relay traffic between several different privately addressed networks by leasing several different addresses to reach different destination networks.

As of 2004, the protocol was in the experimental stage and was not yet in widespread use.

IETF activities: [RFC 3103] Realm Specific IP: Protocol Specification