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Revised Telnet Status Option NIC 31154 (25 Oct. 74) Request for Comments: 651 D. Crocker (UCLA-NMC) 25 Oct. 74 RFC# 651 Online file: <[ISI]<DCROCKER>STATUS-OPTION-REVISION.RNO

                   Revised Telnet Status Option

1. Command name and code

 STATUS  5

2. Command meanings

 As described in the NAOL and NAOP option specifications, this option applies
 to a simplex connection.
    IAC DO STATUS 
       Sender of DO wishes to be able to send requests for status-of-options 
       information, or confirms that he is willing to send such requests.
    IAC WILL STATUS 
       Sender of WILL wishes or agrees to send status information, 
       spontaneously or in response to future requests.
    IAC DON'T STATUS 
       Sender refuses to carry on any further discussion of the current 
       status of options.
    IAC WON'T STATUS 
       Sender refuses to carry on any further discussion of the current 
       status of options.
    IAC SB STATUS SEND IAC SE
       Sender requests receiver to transmit his (the receiver's) perception 
       of the current status of Telnet options. The code for SEND is 1. (See 
       below.)
    IAC SB STATUS IS ... IAC SE 
       Sender is stating his perception of the current status of Telnet 
       options. The code for IS is 0. (See below.)

3. Default

 DON'T STATUS/WON'T STATUS. That is, the current status of options will not 
 be discussed.

4. Motivation for the option

 This option allows a user/process to verify the current status of Telnet 
 options (e.g., echoing) as viewed by the person/process on the other end of 
 the Telnet connection. Simply renegotiating options could lead to the 
 nonterminating request loop problem discussed in (NIC #16237). The changes 
 to the option, described in this paper, allow STATUS to fit into the normal 
 structure of Telnet options, by deferring the actual transfer of status 
 information to the SB command. Additionally, the numbers of bytes that must 
 be sent to describe the state of the options has been considerably reduced.

5. Description of the option

 WILL/DO are now used only to obtain and grant permission for future 
 discussion. The actual exchange of status information occurs within option 
 subcommands (IAC SB STATUS...).
 Once the two hosts have exchanged a WILL and a DO, the sender of the WILL 
 STATUS is free to transmit status information, spontaneously or in response 
 to a request from the sender of the DO. At worst, this may lead to 
 transmitting the information twice. Only the sender of the DO may send 
 requests (IAC SB STATUS SEND IAC SE) and only the sender of the WILL may 
 transmit actual status information (within an IAC SB STATUS IS ... IAC SE 
 command).
 IS has the subcommands WILL, DO and SB. They are used EXACTLY as used during
 the actual negotiation of Telnet options, except that SB is terminated with 
 SE, rather than IAC SE. Transmission of SE, as a regular data byte, is 
 accomplished by doubling the byte (SE SE). Options that are not explicitly 
 described are assumed to be in their default states. A single IAC SB STATUS 
 IS ... IAC SE describes the condition of ALL options.
 The following is an example of use of the option:
    Host1: IAC DO STATUS
    Host2: IAC WILL STATUS
       (Host2 is now free to send status information at any time. 
       Solicitations from Host1 are NOT necessary. This should not produce 
       any dangerous race conditions. At worst, two IS's will be sent.
    Host1 (perhaps): IAC SB STATUS SEND IAC SE
    Host2 (the following stream is broken into multiple lines only for 
    readability. No carriage returns are implied.):
       IAC SB STATUS IS
       WILL ECHO
       DO SUPPRESS-GO-AHEAD
       WILL STATUS
       DO STATUS
       WILL RCTE
       SB RCTE <11><1><24> SE
       DO NAOL
       SB NAOL DS <66> SE
       IAC SE
    Explanation of Host2's perceptions: It is responsible for echoing back 
    the data characters it receives over the Telnet connection; it will not 
    send Go-Ahead signals; it will both issue and request Status information;
    it will send instruction for controlling the other side's terminal 
    printer; it will discuss the line width for data it is sending.