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.