Window size negotiation for a telnet session

When a telnet connection is established with a switch, the switch always uses the default values of 80 columns by 24 lines for the window dimensions. The window can be resized by either dragging the corner of the window, or by executing the terminal length <x> width <y> CLI command and then configuring the telnet client with those dimensions. The new window dimensions are lost after that telnet session ends.

When the telnet connection is established with a switch, either the switch or the telnet client needs to initiate the inquiry about the availability of NAWS. If NAWS is available, you can resize the window by dragging the corner of the window to the desired size. The telnet software uses NAWS to tell the switch what the new window dimensions are. If the switch supports the requested window dimensions, it uses them for all future interactions. If the switch does not support those window dimensions, it refuses them and the telnet client requests an alternate set of window dimensions. The negotiation continues until the telnet client and the switch agree on the window dimensions.

The switch currently responds to a request from the remote telnet client to negotiate window size. However, some telnet clients do not request to negotiate window size unless the switch’s telnet server suggests that NAWS is available.

This feature allows window size negotiation to occur with telnet clients that support NAWS but do not try to use it unless it is suggested by the switch’s telnet server. The switch’s telnet server will suggest to the telnet client that NAWS is available.