Network Working Group C. Malamud Internet-Draft Memory Palace Press Expires: August 8, 2005 February 4, 2005 Attaching Meaning to Solicitation Class Keywords draft-malamud-keyword-discovery-01.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 8, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This Internet-Draft proposes a mechanism for finding information about solicitation class keywords which are defined in RFC 3865, the No Soliciting SMTP Service Extension. The mechanism uses a DNS NAPTR Resource Record to associate a URI with a solicitation class keyword. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", Malamud Expires August 8, 2005 [Page 1] draft-malamud-keyword-discovery No-Solicit Discovery February 2005 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, [RFC2119]. Table of Contents 1. Solicitation Class Keywords . . . . . . . . . . . . . . . . . 3 2. The No-Solicit NAPTR Application . . . . . . . . . . . . . . . 3 3. Example(Non-Normative) . . . . . . . . . . . . . . . . . . . . 4 4. DDDS Application Specification . . . . . . . . . . . . . . . . 7 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.1 Normative References . . . . . . . . . . . . . . . . . . . 8 8.2 Informative References . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 9 A. Intended Status and Discussion (TO BE REMOVED UPON PUBLICATION) . . . . . . . . . . . . . . . . . . . . . . . . . 9 B. Changes From Previous Draft (TO BE REMOVED UPON PUBLICATION) . . . . . . . . . . . . . . . . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . . 11 Malamud Expires August 8, 2005 [Page 2] draft-malamud-keyword-discovery No-Solicit Discovery February 2005 1. Solicitation Class Keywords [RFC3865] defines the concept of a "solicitation class keyword", which is an arbitrary string or label which can be associated with an electronic mail message and transported by the ESMTP mail service as defined in [RFC2821] and related documents. Solicitation class keywords are formatted like domain names, but reversed. For example, the registrant of "example.com" might specify a particular solicitation class keyword such as "com.example.adv" that could be inserted in a "No-Solicit:" header or in a trace field. [RFC3865] explicitly placed discovery of the meaning of a solicitation class keywords as outside of the scope of the basic ESMTP service extension. If that standard becomes widely deployed, a mail message might contain a large number of solicitation class keywords. The "No-Solicit:" header has keywords inserted by the sender of the message, which might include the sender's own keywords, as well as those mandated by regulatory authorities or recommended by voluntary industry associations. Likewise, the "received:" trace fields might contain a large number of keywords produced by message transfer agents (MTAs), filtering software, forwarding software in the message user agent (MUA), or any other system in the chain of delivery. As the number of keywords employed grows, it will be important to find a method for discovering the meaning behind the various labels. This draft specifies such a mechanism using the DNS NAPTR Resource Record, which is defined in [RFC3403]. An explicit design goal is to keep the system as simple as possible. Approaches such as defining an XML-based structure that would contain keyword meta-data or other approaches that define the format of the explanation were ruled out. Instead, the goal is to associate a solicitation class keyword with a URI, which in turn contains an explanation of the keyword. 2. The No-Solicit NAPTR Application The DDDS framework of [RFC3401] and related documents provides a powerful set of mechanisms that can yield sophisticated applications such as ENUM.[RFC3761] There is a simplification of the DDDS framework called the Straightforward-NAPTR (S-NAPTR) application [RFC3958]. Unfortunately, S-NAPTR does not permit the use of the "U" flag for terminal lookups and does not support the regular expression field of the NAPTR RR. Since a replacement field in a NAPTR record must contain only a domain name, and our goal is to find a URI, this draft does not use the S-NAPTR mechanism. This draft uses the NAPTR RR to do a single lookup from solicitation class keyword to URI. The fields of the NAPTR RR are used as Malamud Expires August 8, 2005 [Page 3] draft-malamud-keyword-discovery No-Solicit Discovery February 2005 follows: o The "ORDER" and "PREFERENCE" fields are to be processed as specified in [RFC3403]: if multiple records are returned, the one(s) with the lowest "ORDER" value that have a matching "SERVICE" field MUST be used. Of those with the lowest ORDER value, those with the lowest "PREFERENCE" SHOULD be used. o The "FLAGS" field MUST contain the character "U". o The "SERVICES" field MUST contain only the string "no-solicit". o The "REGEXP" field MUST contain a valid URI as further specified in this section. o The "REPLACEMENT" field MUST be empty. The "REGEXP" field is defined in [RFC3402] as consisting of a "delim-character", a POSIX Extended Regular Expression, another "delim-character", a replacement value, and a final "delim-character". For this application the following rules apply: o The "delim-character" MAY be any valid character as defined in section 3.2 of [RFC3402]. o The extended regular expression MUST be empty. o The replacement value MUST contain a valid URI as specified in [RFC2396]. o The replacement value SHOULD contain a URI limited to the "ftp", "http", and "https" schemes as specified in [RFC2396] and [RFC2660]. o The document that is retrieved at the URI SHOULD conform to [W3C.REC-html401-19991224], including the Accessibility Guidelines contained therein. 3. Example(Non-Normative) A set of NAPTR records have been installed in the "simians.net" subdomain and can be retrieved using "dig" or other DNS utilities: Malamud Expires August 8, 2005 [Page 4] draft-malamud-keyword-discovery No-Solicit Discovery February 2005 [carl@example.com]% dig 2795.simians.net naptr ; <<>> DiG 9.2.3 <<>> 2795.simians.net naptr ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 43494 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 2, ADDITIONAL: 1 ;; QUESTION SECTION: ;2795.simians.net. IN NAPTR ;; ANSWER SECTION: 2795.simians.net. 86400 IN NAPTR 1 1 "U" "iam+invalid" "!!http://invalid.simians.net/contact.html!" . 2795.simians.net. 86400 IN NAPTR 1 1 "U" "sip+invalid" "!!http://invalid.simians.net/contact.html!" . 2795.simians.net. 86400 IN NAPTR 1 2 "U" "no-solicit" "!!http://infinite.simians.net/keywordinfo.html!" . 2795.simians.net. 86400 IN NAPTR 2 1 "U" "no-solicit" "!!http://infinite.simians.net/keywordinfo.html!" . 2795.simians.net. 86400 IN NAPTR 1 1 "U" "no-solicit" "!!http://infinite.simians.net/keywordinfo.html!" . A simple utility written in PERL accepts a lookup key and returns a URL using the specifications in this document: Malamud Expires August 8, 2005 [Page 5] draft-malamud-keyword-discovery No-Solicit Discovery February 2005 #!/usr/bin/perl # This program accepts a solicitation class keyword and # returns a URL on success. It dies quietly on failure. use strict; # http://www.net-dns.org/ use Net::DNS; # reverse the label to create a domain name my $target = join( ".", reverse( split( /\./, $ARGV[0]) ) ); # create a resolver my $res = Net::DNS::Resolver->new; # find all naptr records my $query = $res->query( "$target", "NAPTR" ) || exit ; # Do your DNSSEC checks here, throw away all invalid RRs # get the answers, strip out non-matching services, # sort by order, preference my @rr = sort { # sort records numerically by order, preference $a->order <=> $b->order || $a->preference <=> $b->preference } grep { $_->service =~ /no-solicit/ } $query->answer; # print the first qualifying record, strip out the # regexp markers my $op = substr( my $answer = $rr[0]->regexp , 0, 1 ) || exit ; print split ( $op, $answer ) ; exit ; Running the code gives the following results: Malamud Expires August 8, 2005 [Page 6] draft-malamud-keyword-discovery No-Solicit Discovery February 2005 [carl@example.com]% lynx -source `./discover.pl net.simians.2795`