Network Virtual Terminal
figure concept of NVT
To accommodate heterogeneity TELNET defines how data command sequence are sent across the internet. the defines on is known as the network virtual terminal. As figure illustrates the client software translate keystrokes and command sequences form the user terminal into NVT format and sends them to the server. Server software translates systems incoming data and command from NVT format into the format the remote systems requires. For data returning the remote server translates from the remote machine format to NVT and the local translate form NVT to the local machines format.
NVT Character set: The definition of NVT is straight forward NVT uses tow sets for characters one for data and the other for control. Both are 8 bits. For data NVT is an 8 bit character set in which the 7 lowest order bits are the same as ASCII and the highest order is 0. To send control characters between computers (From client to server or vice versa).NVT uses an 8 bit characters set which the highest order bit is set to 1. Some of the control character and their meaning are.