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Internet Engineering Task Force (IETF)                        R. ClaytonRequest for Comments: 6692                       University of CambridgeUpdates:6591                                               M. KucherawyCategory: Standards Track                                Cloudmark, Inc.ISSN: 2070-1721                                                July 2012Source Ports in Abuse Reporting Format (ARF) ReportsAbstract   This document defines an additional header field for use in Abuse   Reporting Format (ARF) reports to permit the identification of the   source port of the connection involved in an abuse incident.   This document updatesRFC 6591.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6692.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Clayton & Kucherawy          Standards Track                    [Page 1]

RFC 6692                    ARF Source Ports                   July 2012Table of Contents1. Introduction ....................................................22. Keywords ........................................................23. Source-Port Field Definition ....................................24. Time Accuracy ...................................................35. IANA Considerations .............................................36. Security Considerations .........................................37. References ......................................................47.1. Normative References .......................................47.2. Informative References .....................................4Appendix A. Acknowledgements .......................................51.  Introduction   [ARF] defined the Abuse Reporting Format, an extensible message   format for Email Feedback Reports.  These reports are used to report   incidents of email abuse.  ARF was extended by [AUTHFAILURE-REPORT]   to enable the reporting of email authentication failures.  These   specifications provided for the source IP address to be included in a   report.  As explained in [LOG], the deployment of IP address sharing   techniques requires the source port values to be included in reports   if unambiguous identification of the origin of abuse is to be   achieved.   This document defines an ARF reporting field to contain this   information and provides guidance for its use.2.  Keywords   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described in [KEYWORDS].3.  Source-Port Field Definition   A new ARF header field called "Source-Port" is defined.  When present   in a report, it MUST contain the client port of the TCP connection   from which the reported message originated, corresponding to the   "Source-IP" field that contains the client address of that same   connection, thereby describing completely the origin of the abuse   incident.   Per, [ABNF], the formal syntax is:     source-port = "Source-Port:" [CFWS] 1*5DIGIT [CFWS] CRLFClayton & Kucherawy          Standards Track                    [Page 2]

RFC 6692                    ARF Source Ports                   July 2012   "CFWS", which represents email-style comments or folding white space,   is imported from [MAIL].   When any report is generated that includes the "Source-IP" field (see   Section 3.2 of [ARF]), this field SHOULD also be present, unless the   port number is unavailable.   Use of this field is RECOMMENDED for reports generated per   [AUTHFAILURE-REPORT] (seeSection 3.1 of that document).4.  Time Accuracy   [LOG] underscores the importance of accurate clocks when generating   reports that include source port information because of the fact that   source ports can be recycled very quickly in Internet Service   Provider environments.  The same considerations described there apply   here.   Report generators that include an Arrival-Date report field MAY   choose to express the value of that date in Universal Coordinated   Time (UTC) to enable simpler correlation with local records at sites   that are following the provisions of [LOG].5.  IANA Considerations   IANA has added the following entry to the "Feedback Report Header   Fields" registry:   Field Name:  Source-Port   Description:  TCP source port from which the original message was      received   Multiple Appearances:  No   Related "Feedback-Type":  any   Reference:  [RFC6692]   Status:  current6.  Security Considerations   This extension introduces no new security considerations not already   covered in [ARF].   Some security considerations related to the general topic of source   port logging can be found in [LOG].Clayton & Kucherawy          Standards Track                    [Page 3]

RFC 6692                    ARF Source Ports                   July 20127.  References7.1.  Normative References   [ABNF]     Crocker, D. and P. Overell, "Augmented BNF for Syntax              Specifications: ABNF", STD 68,RFC 5234, January 2008.   [ARF]      Shafranovich, Y., Levine, J., and M. Kucherawy, "An              Extensible Format for Email Feedback Reports",RFC 5965,              August 2010.   [AUTHFAILURE-REPORT]              Fontana, H., "Authentication Failure Reporting Using the              Abuse Reporting Format",RFC 6591, April 2012.   [KEYWORDS]              Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [MAIL]     Resnick, P., Ed., "Internet Message Format",RFC 5322,              October 2008.7.2.  Informative References   [LOG]      Durand, A., Gashinsky, I., Lee, D., and S. Sheppard,              "Logging Recommendations for Internet-Facing Servers",BCP 162,RFC 6302, June 2011.Clayton & Kucherawy          Standards Track                    [Page 4]

RFC 6692                    ARF Source Ports                   July 2012Appendix A.  Acknowledgements   The authors wish to acknowledge the following for their review and   constructive criticism of this proposal: Steve Atkins, Scott   Kitterman, John Levine, and Doug Otis.   The idea for this work originated within the Messaging Anti-Abuse   Working Group (MAAWG).Authors' Addresses   Richard Clayton   University of Cambridge   Computer Laboratory   JJ Thomson Avenue   Cambridge  CB3 0FD   United Kingdom   Phone: +44 1223 763570   EMail: richard.clayton@cl.cam.ac.uk   Murray S. Kucherawy   Cloudmark, Inc.   128 King St., 2nd Floor   San Francisco, CA 94107   US   Phone: +1 415 946 3800   EMail: superuser@gmail.comClayton & Kucherawy          Standards Track                    [Page 5]