RFC 1090 (rfc1090) - Page 2 of 4
SMTP on X
Alternative Format: Original Text Document
RFC 1090 SMTP on X.25 February 1989 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 Unlike TCP, X.25 does not provide for synchronous delivery of data in transit when a clear request is in progress; any packets in transit are discarded when the VC is cleared. Therefore, on X.25, the SMTP session layer is closed by the calling side when the Service Closing message is received, either in response to a QUIT command, or because the service must shut down. 10. Timeouts SMTP does not normally provide for timing out a session. On X.25, the following has proven to be effective: 10.1. call request If a call accept is not received within 100 seconds, or the Service Ready message is not received within (another) 120 Ullmann
