RFC 2217 (rfc2217) - Page 2 of 14
Telnet Com Port Control Option
Alternative Format: Original Text Document
RFC 2217 Telnet Com Port Control Option October 1997 Many new business functions require a person to connect to remote services to retrieve or deposit information. By in large, these remote services are accessed via an async dial up connection. This new class of functions include: - dial up connections to the Internet - connecting to bulletin boards - connecting to internal and external databases - sending and receiving faxes. The general nature of this new class of function requires an interactive, character-oriented communications session via an async modem. This is typically known as outbound modem dialing. To help defer the cost of installing and maintaining additional phone lines which may be used very little per person, many equipment manufacturers have added the ability to establish a Telnet session directly to the outbound ports on many of the most popular access servers and routers, here after referred to as access servers. However, the current Telnet protocol definitions are not sufficient to fully support this new use. There are three new areas of functionality which need to be added to the Telnet protocol to successfully support the needs of outbound modem dialing. These are: - The ability for the client to send com port configuration information to the access server which is connected to the outbound modem. This is needed to ensure the data being transmitted and received by the modem is formatted correctly at the byte level. - The ability for the access server to inform the client of any modem line or signal changes such as RLSD changes (carrier detect). This information is vital, since many client software packages use this information to determine if a session with the remote service has been established. RLSD changes are also used for signaling in Class I faxing [6]. - The ability to manage flow control between the client and the access server which does not interfere with the flow control mechanisms used by the session between the client and the remote service. Unfortunately RFC 1372 "Telnet Remote Flow Control Option" [2] can not be used for this purpose because it relies on sending XON/XOFF style characters which maybe transmitted or received as a normal course of the client / remote service session. Clark Experimental
