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The location of the host servers is known to the redirectors, which are specially equipped routers. They maintain information about host servers and the services currently installed on them. Each redirector maintains a redirector table, which lists the transport-level service access points (in our case pairs of IP addresses and port numbers) for which packets must be redirected, and the host server to which the packets must go.

When a redirector receives an IP packet, it checks the destination IP address and port in the header against the entries in the redirector table. If it finds a match, it forwards the packet to the appropriate server host. If there is no match, the packet is simply forwarded to the origin host. A packet is redirected to the appropriate host server by tunnelling it using IP-in-IP encapsulation. The host server is equipped to detect tunnelled packets and to forward them internally to the service gif.

Riccardo Bettati
Tue Jun 9 00:52:24 CDT 1998