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RFC 587 UNKNOWN TERMINAL · TELNET

Announcing New Telnet Options

Two new options let Telnet sessions agree on display size

On rfc-editor.org ↗
PUBLISHED
November 1973
AUTHORS
J. Postel
STREAM
Legacy
NAOL NIC DOCUMENT
20196
NAOP NIC DOCUMENT
20197
DOI
10.17487/RFC0587

RFC text

Original text · RFC Editor View on rfc-editor.org ↗ 
Network Working Group                                         Jon Postel
Request for Comments: 587                                          MITRE
                                                           November 1973


                     Announcing New Telnet Options

   This is to announce that two new TELNET options have been specified.

      Negotiate About Output Line Width (NAOL)  NIC#20196

      Negotiate About Output Page Size (NAOP)  NIC#20197

   These were prepared by Dave Walden (BBN-NET) and put on-line by Anita
   Coley (UCLA-NMC) and Dave Crocker (UCLA-NMC).






























         [ This RFC was put into machine readable form for entry ]
           [ into the online RFC archives by Rich Bowen 11/97. ]

AI ELI5

On this page
PROBLEMWhen a user connected via Telnet from a remote terminal to a network host, neither side knew the width and height of the user's screen, making it hard to format output properly.
MECHANISMTwo new Telnet options were specified: NAOL (Negotiate About Output Line Width) and NAOP (Negotiate About Output Page Size), allowing the server to ask the client about its screen dimensions during connection.
THE FEATUREHosts could now discover and adapt to the user's terminal dimensions, making interactive sessions work better across different terminal types.

§1Two New Telnet Options Announced

This RFC announces the specification of two new Telnet options, the protocols that allow a Telnet client and server to negotiate capabilities during connection. The two options are NAOL (Negotiate About Output Line Width, NIC#20196) and NAOP (Negotiate About Output Page Size, NIC#20197).

These options were prepared by Dave Walden at BBN-NET and put online by Anita Coley and Dave Crocker at UCLA-NMC.

Two new settings for the Telnet remote-login tool were documented and made official.

§2Line Width and Page Size Options

The NAOL option (Negotiate About Output Line Width) allows a Telnet server to negotiate with the client (the user's terminal) to discover the maximum width of the display. This lets the host format output so lines do not wrap unexpectedly.

The NAOP option (Negotiate About Output Page Size) handles the vertical dimension, allowing the server to learn how many lines the user's terminal can display before it scrolls. This is useful for pagination and interactive screen formatting.

NAOL lets computers talk about how wide a screen is. NAOP talks about how many lines tall it is.

§3Terminal Negotiation During Connection

With these options, when a Telnet session begins, the server can use the Telnet option negotiation mechanism to ask the client for its display dimensions. Both the line width and page size become known to the host, which can then format interactive output—menus, forms, and line-wrapped text—to fit the user's actual terminal size.

This is especially important in the ARPANET era, when terminals vary widely in their capabilities and users might be connecting from many different terminal types over the network.

When you log in via Telnet, the host computer can now ask your terminal 'how wide are you?' and 'how tall are you?' and adjust what it sends accordingly.