Gateways

One way to avoid using redundant protocols on end systems is to use a gateway. Gateway is a generic term for any device that provides a translation function between two dissimilar networking, or computing, mechanisms. In the case of a routed protocol, a single device could be installed in the network that can communicate with other end systems, regardless of which routed protocol they use. An IP-only end system that needed to communicate with an IPX-only host, for example, would forward its datagrams to the gateway. The gateway would convert the IP datagram to IPX, complete with addressing, and forward the new datagram to its destination. Responses from the host to the end system would function in a similar manner, albeit in reverse.

Figure 14-3 demonstrates use of a protocol-converting gateway in a small network. In this illustration,

Internetworking with Dissimilar Protocols both protocols are used simultaneously in the same LAN environment, but each LAN-attached device is only configured for one of the protocols.

Figure 14-3: Using a gateway to translate between dissimilar routed protocols.

Figure 14-3: Using a gateway to translate between dissimilar routed protocols.

Gateways can be almost any type of computer. The only criterion is that the gateway device be capable of translating between the two protocols' address architectures and data structures. This requires that the gateway computer have the necessary NICs, device drivers, and conversion software to function as a gateway. Of course, it would also be beneficial if this computer also had the processing power needed to accommodate the loads that will be placed on it!

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