RFC 1571 (rfc1571) - Page 3 of 4

Telnet Environment Option Interoperability Issues

RFC 1571          Environment Option Interoperability       January 1994


   never exceed the sum of VARs and USERVARs, and the number of VARs
   will never exceed the sum of VALUEs and USERVARs.  Hence, this check
   is redundant and can be skipped.

   If things are still in doubt, the values of the VAR commands can be
   checked to see if they do indeed specify well known variables.  If
   any of them do, then the client is probably using the correct
   definitions for VAR and VALUE.  Otherwise, if any of the VALUEs
   contain well know variable names, then the client probably has
   reversed definitions for VAR and VALUE.

   If all the above heuristics fail, then the server has done all it can
   to determine what type of client it is, and it should just be assumed
   that the client is using the correct definitions for VAR and VALUe.

4.  Client Summary

       The SEND suboption contains only VAR and USERVAR commands.
           The server is ok.
       The SEND suboption contains VALUE commands.
           The server is reversed.
       No VAR or VALUE commands are found.
           Assume the server is ok.

5.  Server Summary

       IS/INFO is followed by VAR.
           The client is ok.
       IS/INFO is followed by VALUE.
           The client is reversed.
       There are two consecutive VARs.
           The client is ok.
       There are consecutive VALUEs.
           The client is reversed.
       There is an empty VALUE.
           The client is ok.
       There is an empty VAR.
           The client is reversed.
       The number of USERVARs and VARs is equal to the number of VALUEs.
           Assume the client is ok.
       The number of USERVARs and VALUEs is equal to the number of VARs.
           Assume the client is reversed.
       There are VARs with names that are well known.
           Assume the client is ok.
       There are VALUEs with names that are well known.
           Assume the client is reversed.
       Anything else.
           Assume the client is ok.



Telnet Working Group