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Browse Prior Art Database

SMTP on X.25 (RFC1090)

IP.com Disclosure Number: IPCOM000001899D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 3 page(s) / 5K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

R. Ullmann: AUTHOR

Abstract

The possibility of using the X.25 virtual circuit (ISO level 3) directly for SMTP is mentioned in RFC 821 ("SIMPLE MAIL TRANSPORT PROTOCOL"), in appendix D. It suggests that "a reliable end-to-end protocol such as TCP be used on top of X.25 connections". This was undoubtedly true considering the general reliability of the PSDNs at the time (1981). The service is now (in 1989) reliable enough to allow practical direct use of the virtual circuit service.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 56% of the total text.

Network Working Group R. Ullmann

Request for Comments: 1090 Prime Computer, Inc.

February 1989

SMTP on X.25

1. Status of this Memo

This memo proposes a standard for SMTP on the virtual circuit

facility provided by the X.25 standard of the CCITT.

Distribution of this memo is unlimited.

2. Introduction

The possibility of using the X.25 virtual circuit (ISO level 3)

directly for SMTP is mentioned in RFC 821 ("SIMPLE MAIL TRANSPORT

PROTOCOL"), in appendix D. It suggests that "a reliable end-to-end

protocol such as TCP be used on top of X.25 connections". This was

undoubtedly true considering the general reliability of the PSDNs at

the time (1981). The service is now (in 1989) reliable enough to

allow practical direct use of the virtual circuit service.

The procedures given here have proven to be successful in extensive

production use, involving 24 PSDNs in 22 different countries. The

resulting service is economical even using some of the more expensive

PSDNs. Operation over private X.25 connections and X.25 LANs has

also proven successful.

An X.25 virtual circuit (VC) is opened for each SMTP session. The

full duplex channel provided by the VC is used for the session. The

VC is then closed, normally by the calling side.

3. Protocol ID and Call User Data

The first four octets (bytes) of the Call User Data Field, which are

commonly used as a protocol identifier, or PRID, should be (hex)

C0F70000. (In decimal, 192 247 0 0.)

Implementations should, however, provide the ability to configure the

call user data on a per-address basis, including the protocol ID

field.

4. Data stream

The SMTP data is divided into (streamed into) packets in any way the

sending side prefers. Sequences with the M bit (more data) set are

encouraged, and may be up to 2048 bytes in total length.

It is recommended that SMTP commands and responses be sent as single

packets, or single more-data sequences, if only to facilitate

debugging the protocol. This is not a requirement.

5. Qualified data

Packets with the Q bit set and interrupt packets are not used, and

should be ignored if received.

6. Circuit resets

If a level 3 circuit reset is received, the VC should be cleared, and

the SMTP connection attempted again. The retry may be after some

delay, and may be with different call facilities.

7. Call facilities

Any negotiable features selected by the X.25 call request facilities

field may be used. Implementations should provide the ability to

specify facilities for each called address.

8. Character code

The character code used on X.25 is the full ASCII-8 code, with no

escapes or modifications. Lines are terminated by CRLF (13 10

decimal). Implementations should, if possible, recognize lines

terminated only by LF (10 decimal).

9. Closing the connection

...