[Contents] [Back] [<< Prev] [Next >>]

Gateway Services
Routers can handle interconnection of networks whose protocols function in similar ways. When the rules differ sufficiently on the two networks, however, a more powerful device is required.

A gateway is a device that can reconcile the different rules used on two different networks. Gateways commonly are required to connect LANs to mainframe networks, which have completely different protocol architectures. Mainframe networks, such as IBM’s SNA, for example, do not use the same device address schemes that LANs employ (these networks differ in many other ways as well). In these situations, you must fool the mainframe network into thinking that mainframe devices are on the LAN. This involves making the mainframe look like a LAN to devices on the LAN. Exercise 2.1, at the end of this chapter, explores Windows NT’s Gateway Services for NetWare, which provides a gateway from a Microsoft network to NetWare resources.


[note.gif]

Gateways can be implemented at the Network layer or at higher layers in the OSI model, depending on where the protocol translation is required.