FTP extension: XRSQ/XRCP (RFC0743)
Original Publication Date: 1977-Dec-01
Included in the Prior Art Database: 2019-Feb-14
Internet Society Requests For Comment (RFCs)
NWG/RFC# 743 KLH 30-Dec-77 08:39 42759 Network Working Group K. Harrenstien Request for Comments: 743 SRI-KL NIC: 42758 30 December 1977
FTP extension: XRSQ/XRCP
This RFC describes an extension to FTP which allows the user of an ITS FTP server (i.e. on MIT-(AI/ML/MC/DMS)) to mail the text of a message to several recipients simultaneously; such message transmission is far more efficient than the current practice of sending the text again and again for each additional recipient at a site.
Within this extension, there are two basic ways of sending a single text to several recipients. In one, all recipients are specified first, and then the text is sent; in the other, the order is reversed and the text is sent first, followed by the recipients. Both schemes are necessary becaue neither by itself is optimal for all systems, as will be explained later. To select a particular scheme, the XRSQ command is used; to specify recipients after a scheme is chosen, XRCP commands are given; and to furnish text, the usual MAIL or MLFL commands apply.
Scheme Selection: XRSQ
XRSQ is the means by which a user program can test for implementation of XRSQ/XRCP, select a particular scheme, reset its state thereof, and even do some rudimentary negotiation. Its format is like that of the TYPE command, as follows:
XRSQ [<SP> <scheme>] <CRLF>
<scheme> = a single character. The following are defined: R Recipients first. If not implemented, T must be. T Text first. If this is not implemented, R must be. ? Request for preference. Must always be implemented.
No argument means a "selection" of none of the schemes (the default).
Replies: 200 OK, we’ll use specified scheme. 215 <scheme> This is the scheme I prefer. 501 I understand XRSQ but can’t use that scheme. 5xx Command unrecognized or unimplemented. See Appendix A for more about the choice of reply codes.
Three aspects of XRSQ need to be pointed out here. The first is that
NWG/RFC# 743 KLH 30-Dec-77 08:39 42759 An Extension to FTP
an XRSQ with no argument must always return a 200 reply and restore the default state of having no scheme selected. Any other reply implies that XRSQ and hence XRCP are not understood or cannot be performed correctly.
The second is that the use of "?" as a <scheme> asks the FTP server to return a 215 reply in which the server specifies a "preferred" scheme. The format of this reply is simple:
215 <SP> <scheme> [<SP> <arbitrary text>] <CRLF>
Any other reply (e.g. 4xx or 5xx) implies that XRSQ and XRCP are not implemented, because "?" must always be implemented if XRSQ is.
The third important thing about XRSQ is that it always has the side effect of resetting all schemes to their initial state. This reset must be done no matter what the reply will be - 200, 215, or 501. The actions necessary for a reset will be explained when discussing how each scheme actually works.
Message Text Specification: MAIL/MLFL
Regardless of which scheme (if any) has been selected, a MAIL or MLFL with a non-nul...