Gateway operates at all 7 layers of the OSI model. It is a device, which connects two different dissimilar n/w which have same function of communication. Situation where gateways are necessary for different n/w like Ethernet, Token Ring, and FDDI etc. It can communicate if they are using same protocol for communication like TCP/IP 08 Apple talk if they are using different protocol from a gateway cash forward packet across different n/w s that may also use different protocol. Eg: if n/w A is a Token Ring network using TCP/IP & network B is a Novell Network, a gateway can relay frames between two. This means that a gateway has not only had, but also between different protocols. In certain situations the only changes required are to the frame header. In other cases, the gateway must take case of different frame sizes, data rates, format, acknowledgement schemes, and priority schemes tec.