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
<draft-ietf-msgtrk-model-00.txt>
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]
