Internet Draft T. Hansen draft-ietf-msgtrk-model-00.txt AT&T Laboratories Valid for six months K. Lin Lotus Development Corporation September 8, 1999 Message Tracking Model Authors' version: 1.6 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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 memo and its companions are discussed on the MSGTRK working group mailing list, ietf-msgtrk[-request]@imc.org. Copyright Notice Copyright (C) The Internet Society (1999). All Rights Reserved. Abstract Customers buying enterprise message systems often ask: Can I track the messages? Message tracking is the ability to find out the path that a particular message has taken through a messaging system and the current routing status of that message. This document provides a model of message tracking that can be used for understanding the Internet-wide Hansen,Lin [Page 1] Internet Draft Message Tracking Model September 8, 1999 message infrastructure and to further enhance those capabilities to include message tracking. 1. Problem Statement Consider sending a package through a package delivery companys. Once you've sent a package, you would like to be able to find out if the package has been delivered or not, and if not, where that package currently is and what its status is. Note that the status of a package may not include whether it was delivered to its addressee, but just the destination. Many package carriers provide such services today, often via a web interface. Message tracking extends that capability to the Internet-wide mes- sage infrastructure, analogous to the service provided by package car- riers: the ability to quickly locate where a message (package) is, and to determine whether or not the message (package) has been delivered to its final destination. An Internet-standard approach will allow the development of message tracking applications that can operate in a multi-vendor messaging environment, and will encourage the operation of the function across administrative boundaries. 2. Definitions The following terms are relevant to message tracking. The terms Track- ing User Agent and Tracking Server are new, while all other terms have been collected here from other sources. Originating Mail User Agent (MUA) The originating mail user agent is the software used to compose and originate a message. It is the software sit- ting on a person's desktop. Originating Mail Submission Agent (MSA) The Mail Submission Agent accepts a message from a User Agent, adds or modifies whatever headers are appropriate for the message's traversal through the Internet, and injects the message into the network via a Message Transfer Agent. (The UA and MSA are often combined into the same program.) Message Transfer Agent (MTA) A Message Transfer Agent accepts a message and moves it forward towards its destination. That destination may be local or reached via another MTA. It may use a local queue to store the message before transferring it further. Any MTA may generate a Non-Delivery Notifica- tion. Hansen,Lin [Page 2] Internet Draft Message Tracking Model September 8, 1999 Intermediate Message Transfer Agent (MTA) An Intermediate MTA is an MTA that accepts a message for transfer somewhere else. Final Message Transfer Agent (MTA) A Final MTA is an MTA that accepts a message for local delivery. It is the final place that a message is accepted. The final MTA is what sends any Delivery Status Notificatons (DSNs). Foreign Message Transfer Agent A foreign MTA provides delivery of messages using other protocols than those specified for Internet mail, such as an X.400 mail system. Gateway Message Transfer Agent (GW-MTA) A gateway MTA accepts a message for transfer to a foreign MTA outside of the Internet protocol space. Local Delivery Agent (DA) The local Delivery Agent delivers the message to the local message store. (The MTA and DA are often combined into the same program.) Delivery Status Notification (DSN) A Delivery Status Notification [RFC-DSN] is produced by an MTA when a message is unsuccessfully delivered, either to its next hop or the final message store, or when it is successfully delivered, either to a foreign MTA or to a local delivery agent. Positive notifications are only performed [RFC-ESMTP-DSN] when specifically requested. Non-Delivery Notification (NDN) A non-delivery notification is a special form of DSN indicating unsuccessful delivery. Message Disposition Notification (MDN) A Message Disposition Notification is used to report the disposition of a message after it has been successfully delivered to a recipient. Tracking User Agent (TUA) A tracking user agent wants to find information on a mes- sage on the behalf of a user. It is the requestor or initiator of such a request. (The MUA and TUA could be combined into the same program.) Tracking Server Hansen,Lin [Page 3] Internet Draft Message Tracking Model September 8, 1999 A tracking server provides tracking information to a tracking client. It is the repository of the information about a message for the traversal through a particular MTA. (The tracking server and MTA may run on the same system.) 3. Entities The entities involved in message tracking are: message user agents, message submission agents, message transfer agents, tracking user agents and tracking servers. 4. Interaction Models There are several models by which messages can be tracked, and by which information can be requested and gathered. 4.1. Pre-Hoc Model The pre-hoc model, also known as the "passive or "ask now" models, requires the user agent to put into the message envelope an indication that some form of tracking is to be performed. The tracking information can be sent back immediately (as a form of telemetry) or stored for later retrieval. Forms of tracking information that could potentially be requested are as follow. Note that mechanisms already exist for requesting the information marked with a (+). The references for such mechanisms are listed at the end of each such entry. ** send a DSN of a message arriving at an intermediate MTA ** (+) send a DSN of a message being rejected while at an inter- mediate MTA [RFC-DSN] ** (+) send a DSN of a message leaving an intermediate MTA and going to another MTA [RFC-DELIVERY-BY] ** send a DSN of a message arriving at a final MTA ** (+) send a DSN of a message being rejected while at a final MTA [RFC-DSN] ** (+) send a DSN of a message being delivered to a user's mes- sage store [RFC-DSN] ** (+) send a DSN of a message being delivered to a foreign MTA [RFC-DSN] Hansen,Lin [Page 4] Internet Draft Message Tracking Model September 8, 1999 ** (+) send an MDN of a message being read by an end user [RFC- MDN] ** indicate that logging of the message's traversal should be performed for later retrieval ** indicate that logging of the message's traversal should be sent to a 3rd party 4.2. Post-Hoc Model The post-hoc model, also known as the "query" or "ask later" model, requires an active query by a user's user agent to either the intermedi- ate MTAs and final MTA, or to a third party, to find the message's status as known by that MTA. The responses might be something like: the message has been queued for later delivery, the message was delivered locally, the message was delivered to another MTA, ask a dif- ferent tracking server, I know but can't tell you, or I don't know. The post-hoc model may or may not require an earlier pre-hoc declaration that logging of the message's traversal should occur. (Note that no mechanisms currently exist for requesting such information.) 4.3. Hybrid Models A number of hybrid models exist. In a hybrid model, pre-hoc mechanisms are combined with post-hoc mechanisms to provide a total mes- sage tracking solution. The model would include existing pre-hoc mechanisms, possible new pre-hoc mechanisms, and new mechanisms for post-hoc tracking. A UA may be required to start the process by estab- lishing pre-hoc information which is then communicated with the MTAs. A tracking user agent would then use all possible information sources to answer the question of "what happened to message XX"? 5. Security The security aspects of message tracking revolve around the follow- ing areas: ** Who is permitted to request tracking information? ** How does a tracking user agent prove that they are permitted to request such information? ** How does the tracking user agent identify the messages being tracked? Hansen,Lin [Page 5] Internet Draft Message Tracking Model September 8, 1999 5.1. Who is Permitted to Request Tracking Information? Only the originators of messages are allowed to track their mes- sages. An originator may delegate this responsibility to a third party. 5.2. How Does a Tracking User Agent Prove that They are Permitted to Request Such Information? One possible mechanism to prove that a tracking request comes the originator is for the originator to calculate a one-way hash A from the message ID + time stamp + a per-user secret. The user then calculates another one-way hash B to be the hash of A. The user includes B in the submitted message, and retains A. Later, when the user makes a message tracking request to the messaging system or tracking entity, it submits A in the tracking request. The entity receiving the tracking request then uses A to calculate B, since it was already provided B, verifying that the requestor is authentic. In summary, A = H(message ID + time stamp + secret) B = H(A) This is similar in technique to the methods used for One-Time Passwords [RFC-OTP]. If the originator of a message were to delegate his or her tracking request to a third party by sending them A, this would be vulnerable to snooping over unencrypted sessions. The user can decide on a message- by-message basis if this risk is acceptable. 5.3. How does the tracking user agent identify the messages being tracked? Every [RFC-822]-compliant message is supposed to contain a Message-Id header. This header could be used to be the primary means of message identification. 6. References [RFC-DSN] Moore, K., and G. Vaudreuil, "An Extensible Message For- mat for Delivery Status Notifications", RFC 1894, Univer- sity of Tennessee, Octel Network Services, January 1996. [RFC-ESMTP-DSN] Moore, K., "SMTP Service Extension for Delivery Status Notifications", RFC 1891, University of Tennessee, Janu- ary 1996. Hansen,Lin [Page 6] Internet Draft Message Tracking Model September 8, 1999 [RFC-SMTP]Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821, USC/Information Sciences Institute, August 1982. [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet Text Messages", STD 11, RFC 822, UDEL, August 1982. [RFC-MDN] Fajman, R., "An Extensible Message Format for Message Disposition Notifications", RFC 2298, National Institutes of Health, March 1998. [RFC-DELIVER-BY] Newman, D., "Deliver By SMTP Service Extension", draft- newman-deliver-02.txt, Innosoft, January 1999. [RFC-OTP] Haller, N., Metz, C., Nesser, P., Straw, M., "A One-Time Password System", RFC 2289, Bellcore, Kaman Sciences Cor- poration, Nesser & Nesser Consulting, Bellcore, February 1998. 7. Acknowledgements This document is the product of input from many people and many sources. It owes much to earlier work by Gordon Jones, Bruce Ernst and Greg Vaudreuil. 8. Authors' Addresses Tony Hansen AT&T Laboratories Lincroft, NJ 07738 USA Phone: +1 732 576-3207 E-Mail: tony@att.com Ken Lin Lotus Development Corporation 640 Lee Road Wayne, PA 19087 Phone: +1 610 251-3380 E-Mail: ken_lin@lotus.com 9. Full Copyright Statement Copyright (C) The Internet Society (1999). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or Hansen,Lin [Page 7] Internet Draft Message Tracking Model September 8, 1999 assist in its implmentation may be prepared, copied, published and dis- tributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organisations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Stan- dards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. This document expires March 2000. Hansen,Lin [Page 8]