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Telnet Environment Option Interoperability Issues (RFC1571)

IP.com Disclosure Number: IPCOM000002405D
Original Publication Date: 1994-Jan-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 3 page(s) / 8K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

D. Borman: AUTHOR

Abstract

Status of this Memo

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 36% of the total text.

Network Working Group D. Borman

Request for Comments: 1571 Cray Research, Inc.

Updates: 1408 January 1994

Category: Informational

Telnet Environment Option Interoperability Issues

Status of this Memo

This memo provides information for the Internet community. This memo

does not specify an Internet standard of any kind. Distribution of

this memo is unlimited.

1. Overview

RFC 1408 [1], the specification for the Telnet Environment Option,

specifies definitions for VAR and VALUE that are reversed from the

BSD implementation of the Telnet Environment option. Since the BSD

implementation was the reference implementation that the RFC was

supposed to document, and is the base for many existing

implementations, there exists an interoperability problem between

implementations with conflicting definitions for VAR and VALUE.

This document describes a method for allowing implementors to ensure

that their implementation of the Environment option will be

interoperable with as many other implementations as possible, by

providing a set of heuristics that can be used to help identify which

definitions for VAR and VALUE are being used by the other side of the

connection.

2. Client Telnet: Parsing a SEND

The SEND suboption should only contain VAR and USERVAR commands. It

should never contain a VALUE. If while parsing a SEND suboption, a

VALUE is encountered, the client should assume that the server has

reversed values for VAR and VALUE, and from that point on the client

should reverse those values, both in parsing the rest of the SEND

suboption, and when generating an IS or INFO suboption. If both

VALUE and VAR commands are encountered, the SEND command is not well

formed, and it is implementation dependent as to what will happen.

If there are not VAR or VALUE commands in the SEND suboption, then

the client cannot know what values the server is expecting for VAR

and VALUE. In this case, it should just assume that the server has

the correct definitions, and use the correct values for VAR and

VALUE.

3. Server Telnet: Parsing an IS or INFO

The IS or INFO in a suboption can only be legally followed by either

a VAR or a USERVAR. If an IS or INFO is immediately followed by a

VAR, then it can be assumed that the client has the correct

definitions for VAR and VALUE. If the IS or INFO is immediately

followed by a VALUE, then it can be assumed that the client has

reversed definitions for VAR and VALUE, and from that point on the

server sho...