SIMPLE E. Burger
Internet-Draft BEA Systems, Inc.
Expires: August 9, 2007 H. Khartabil
February 5, 2007
Instant Message Disposition Notification
draft-ietf-simple-imdn-03
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
Instant Messaging (IM) refers to the transfer of messages between
users in real-time. This document provides a mechanism whereby
endpoints can request Instant Message Disposition Notifications
(IMDN), including delivery, processing and read notifications, for
page-mode instant messages.
The Common Profile for Instant Messaging (CPIM) data format specified
in RFC 3862 is extended with new header fields that enable endpoints
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to request IMDNs. A new message format is also defined to convey
IMDNs.
This document also describes how SIP entities behave using this
extension.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Disposition Types . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Delivery . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. Processing . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3. Read . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6. New CPIM header fields . . . . . . . . . . . . . . . . . . . . 7
6.1. CPIM header field Namespace . . . . . . . . . . . . . . . 8
6.2. Disposition-Notification . . . . . . . . . . . . . . . . . 8
6.3. Message-ID . . . . . . . . . . . . . . . . . . . . . . . . 8
6.4. Original-To . . . . . . . . . . . . . . . . . . . . . . . 8
6.5. IMDN-Record-Route . . . . . . . . . . . . . . . . . . . . 8
6.6. IMDN-Route . . . . . . . . . . . . . . . . . . . . . . . . 9
7. Endpoint Behaviour . . . . . . . . . . . . . . . . . . . . . . 9
7.1. IM Sender . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1.1. Constructing Instant Messages . . . . . . . . . . . . 9
7.1.2. Matching IMs with IMDNs . . . . . . . . . . . . . . . 10
7.1.3. Keeping State . . . . . . . . . . . . . . . . . . . . 11
7.1.4. Aggregation of IMDNs . . . . . . . . . . . . . . . . . 11
7.2. IM Recipient . . . . . . . . . . . . . . . . . . . . . . . 12
7.2.1. Constructing IMDNs . . . . . . . . . . . . . . . . . . 12
8. Intermediary Behaviour . . . . . . . . . . . . . . . . . . . . 14
8.1. Constructing Processing Notifications . . . . . . . . . . 15
8.2. Aggregation of IMDNs . . . . . . . . . . . . . . . . . . . 16
9. Identifying Messages . . . . . . . . . . . . . . . . . . . . . 17
10. header fields Formal Syntax . . . . . . . . . . . . . . . . . 17
11. IMDN Format . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Structure of XML-Encoded IMDN Payload . . . . . . . . . . 18
11.1.1. The <message-id> Element . . . . . . . . . . . . . . . 19
11.1.2. The <datetime> Element . . . . . . . . . . . . . . . . 19
11.1.3. The <recipient-uri> Element . . . . . . . . . . . . . 19
11.1.4. The <original-recipient-uri> Element . . . . . . . . . 19
11.1.5. The <subject> Element . . . . . . . . . . . . . . . . 19
11.1.6. The <disposition> Element . . . . . . . . . . . . . . 19
11.1.7. The <status> Element . . . . . . . . . . . . . . . . . 19
11.1.8. The <note> Element . . . . . . . . . . . . . . . . . . 20
11.2. MIME Type for IMDN Paylaod . . . . . . . . . . . . . . . . 20
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11.3. The RelaxNG Schema . . . . . . . . . . . . . . . . . . . . 20
12. Transporting Messages using SIP . . . . . . . . . . . . . . . 24
12.1. Endpoint Behaviour . . . . . . . . . . . . . . . . . . . . 24
12.1.1. Sending Requests . . . . . . . . . . . . . . . . . . . 24
12.1.2. Sending Responses . . . . . . . . . . . . . . . . . . 24
12.1.3. Receiving Requests . . . . . . . . . . . . . . . . . . 24
12.2. Intermediary Behaviour . . . . . . . . . . . . . . . . . . 25
13. Transporting Messages using MSRP . . . . . . . . . . . . . . . 26
14. Security Considerations . . . . . . . . . . . . . . . . . . . 27
14.1. Forgery . . . . . . . . . . . . . . . . . . . . . . . . . 29
14.2. Confidentiality . . . . . . . . . . . . . . . . . . . . . 29
14.3. Non-Repudiation . . . . . . . . . . . . . . . . . . . . . 30
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
15.1. message/imdn+xml MIME TYPE . . . . . . . . . . . . . . . . 30
15.2. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:imdn . . . . . . . . . . . . . . . 31
15.3. Schema Registration . . . . . . . . . . . . . . . . . . . 31
15.4. Message/CPIM header field registration . . . . . . . . . . 31
15.5. Content-Disposition: notification . . . . . . . . . . . . 32
16. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 32
17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
17.1. Normative References . . . . . . . . . . . . . . . . . . . 32
17.2. Informative References . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
Intellectual Property and Copyright Statements . . . . . . . . . . 34
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1. Introduction
In many user-to-user message exchange systems, message senders often
wish to know if the human recipient actually received or read a
message.
Electronic Mail [10] deals with this situation with Message Delivery
Notifications [11]. After the recipient views the message, her mail
user agent generates a Message Delivery Notification, or MDN. The
MDN is an e-mail that follows the format prescribed by RFC2298 [11].
The fixed format ensures that an automaton can process the message.
Message/CPIM [2] is a message format used to generate instant
messages. SIP [8] can carry instant messages generated using
message/CPIM in SIP MESSAGE requests [9].
This document extends Message/CPIM message format (much like Message
Delivery Notifications [11] extends Electronic Mail [10]) to enable
Instant Message Senders to request, create and send Instant Message
Disposition Notifications (IMDN) for a page-mode as well as session
mode instant messages. IMDNs include positive delivery, negative
delivery (i.e. a message did not get delivered successfully), read
notifications as well as processed notifications. By using CPIM
header fields, the IMDN request and delivery are abstracted outside
the transport protocol allowing interoperability between different IM
systems. Likewise, the mechanism does not rely on session-mode
versus page-mode.
2. Conventions
In this document, the key words 'MUST', 'MUST NOT', 'REQUIRED',
'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',
and 'OPTIONAL' are to be interpreted as described in RFC 2119 [1] and
indicate requirement levels for compliant implementations.
3. Terminology
o IM: An Instant Message generated using the Message/CPIM format.
o IMDN: An Instant Message Disposition Notification generated using
the Message/CPIM format that carries a IMDN XML document.
o Message: an IM or an IMDN generated using the Message/CPIM format.
o IM Sender: An endpoint (User Agent) generating and sending an IM.
It is also the endpoint that requests IMDNs for an IM. Quite
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often, the IM Sender is the IMDN Recipient, but that is not always
true since an IM Sender's Address of Record (AoR) placed in the IM
and in turn used in the IMDN may in fact resolve to different User
Agents. This is a limitation due to the nature of page-mode IMs.
o IM Recipient: An endpoint (User Agent) that receives IMs. It is
also the endpoint that generates and sends IMDNs to IMs, if
requested by the IM Sender.
o Endpoint: An IM Sender or an IM Recipient.
o Intermediary: An entity in the network that is on the path of an
IM to its final destination.
o IMDN Payload: An XML document carrying the disposition
notification information. In this specification, it is of MIME
type "message/imdn+xml".
o Disposition type: the type of IMDN that can be requested. This
specification defines three, namely "delivery", "processing" and
"read" disposition types.
o Transport Protocol Message: A SIP or other protocol message that
contains an IM or IMDN.
4. Overview
The basic protocol flow is depicted in the diagram below. An IM
Sender creates an IM, adds IMDN request information the IM Sender is
interested in receiving, then sends IM. At a certain point in time,
the IM Recipient or an intermediary determines that the user or
application has received, did not receive, read, or otherwise
disposed the IM. The mechanism by which an IM Recipient determines
its user has read an IM is beyond the scope of this document. At
that point, the IM Recipient or intermediary automatically generates
a notification message to the IM Sender. This notification message
is the Instant Message Disposition Notification (IMDN).
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+--------------+ +--------------+
| IM Sender | | IM Recipient |
|IMDN Recipient| | IMDN Sender |
+--------------+ +--------------+
| |
| |
| 1. IM requesting IMDN |
|-------------------------------------->|
| |
| |
| 2. IMDN (disposition) |
|<--------------------------------------|
| |
| |
Note that the recipient of an IMDN, in some instances, may not be the
IM Sender. This is specifically true for page-mode IMs where the
Address of Record (AOR) of the IM Sender, that is present in the
IMDN, resolves to a different location or user agent to where the IM
originated. For simplicity, the rest of this document assumes that
the IM Sender and the IMDN Recipient are the same and therefore will
refer to both as the IM Sender.
5. Disposition Types
There are three broad categories of disposition states. They are
delivery, processing and read. Future extensions may introduce
others.
5.1. Delivery
The delivery notification type indicates whether the IM has been
delivered to the IM Recipient or not. The delivery notification type
can have the following states:
o "delivered" to indicate successful delivery.
o "failed" to indicate failure in delivery.
o "forbidden" indicate denial for the IM Sender to receive the
requested IMDN. The "forbidden" state can be sent by the IM
Recipient but is mainly sent by an intermediary that is configured
to do so. For example, the administrator has disallowed IMDNs.
o "error" to indicate an error in determining the fate of an IM.
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5.2. Processing
The processing notification type indicates that an IM has been
processed by an intermediary. The processing notification type can
have the following states:
o "processed" is a general state of the IM indicating that the
intermediary has performed its task on the IM.
o "stored" state indicates that the IM has been stored by the
intermediary for later delivery.
o "forbidden" indicate denial for the IM Sender to receive the
requested IMDN. The "forbidden" state is sent by an intermediary
that is configured to do so. For example, the administrator has
disallowed IMDNs.
o "error" to indicate an error in determining the fate of an IM.
5.3. Read
The read notification type indicates whether the IM Recipient
rendered the IM to the user or not. The read notification type can
have the following states:
o "read" is a state indicating that the IM has been displayed or
played to the user.
o "forbidden" indicate denial, by the IM Recipient, for the IM
Sender to receive the requested IMDN.
o "error" to indicate an error in determining the fate of an IM.
Some IMs may in fact be audio, video or still images. Therefore, the
state "read" includes playing the audio or video file to the user.
Since there is no positive acknowledgement from the user, one cannot
determine a priori that the user actually read the IM. Thus one
cannot use the protocol described here as a non-repudiation service.
6. New CPIM header fields
This specification extends the CPIM data format specified in RFC 3862
[2]. A new namespace is created as well as a number of new CPIM
header fields.
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6.1. CPIM header field Namespace
Per CPIM [2], this specification defines a new namespace for the CPIM
extension header fields defined in the following sections. The
namespace is:
urn:ietf:params:cpim-header fields:imdn
As per CPIM [2] requirements, the new header fields defined in the
following sections are prepended, in CPIM messages, by a prefix
assigned to the URN through the NS header field field of the CPIM
message. The remaining of this specification always assumes an NS
header field field like this one:
NS: imdn <urn:ietf:params:cpim-header fields:imdn>.
6.2. Disposition-Notification
The Disposition-Notification header field is used by the IM Sender to
indicate the desire to receive IMDNs, from the IM Recipient, for that
specific IM. This header field is not needed if the IM Sender does
not request an IMDN. The syntax is defined in Section 10.
6.3. Message-ID
The Message-ID header field contains a globally unique message
identifier that is used by the IM Sender to correlate received IMDNs
by comparing its value with the value of the <message-id> element
present in the IMDN payload. This header field is MANDATORY when
sending an IM and requesting an IMDN. IMDNs also carry this header
field. The syntax is defined in Section 10.
6.4. Original-To
The Original-To header field is sometimes added to an IM by an
intermediary and populated with the address of the IM Receiver. It
is used by the IM Recipient to indicate in the IMDNs (by populating
the <original-recipient-uri> element) the original address the IM was
sent to. This header field is mandatory if the intermediary changes
the CPIM To header field value. The header field MUST NOT appear
more than once in an IM. The header field value MUST NOT be changed
by an intermediary if it was already present. The syntax is defined
in Section 10.
6.5. IMDN-Record-Route
Intermediaries have the capability of indicating that IMDNs should be
sent through it (otherwise, IMDNs will not visit the intermediary).
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An intermediary that request IMDNs to be sent through itself adds an
IMDN-Record-Route header field to the IM. The value of the IMDN-
Record-Route header field is set to the address of that intermediary.
Multiple IMDN-Record-Route header fields can appear in an IM. The
syntax is defined in Section 10.
6.6. IMDN-Route
The IMDN-Route header field provides routing information by including
one or more addresses where an IMDN must be routed through. On
creating an IMDN, an IM recipient copies the contents of the IMDN-
Record-Route present in the IM into the IMDN-Route of the IMDN.
Multiple IMDN-Route header fields can appear in an IMDN. The syntax
is defined in Section 10.
7. Endpoint Behaviour
7.1. IM Sender
7.1.1. Constructing Instant Messages
An IM is constructed using CPIM Message Format defined in RFC 3862
[2].
7.1.1.1. Adding a Message-ID header field
If the IM sender requests the reception of IMDNs, the IM sender MUST
include a Message-ID header field. The Message-ID field is populated
with a value that is unique with 32 bits of randomness. This header
field enables the IM Sender to match any IMDNs with their
corresponding IMs.
7.1.1.2. Adding a DateTime header field
Some devices may not implement the concept of "Sent Items" box and
therefore no information about an IM is stored. It is therefore
necessary to add a time stamp in the IM to indicate when it was sent.
This time stamp is returned in the IMDN in order to enable the user
to correlate the IM with the IMDN at the human level. The DateTime
header field is used for this purpose. The IM MUST contain a
DateTime header field if an IMDN is requested.
7.1.1.3. Adding a Disposition-Notification header field
The Disposition-Notification conveys the type of disposition
notification requested by the IM sender. There are three types of
disposition notification: delivery, processing, and read. The
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delivery notification is further subdivided into failure and success
delivery notifications. An IM Sender requests failure delivery
notification by including a Disposition-Notification header field
with value "negative-delivery". Similarly, a success notification is
requested by including a Disposition-Notification header field with
value "positive-delivery". Both types of delivery notifications can
be requested for the same IM.
The IM Sender can request a processing notification by including a
Disposition-Notification header field with value "processing".
The IM Sender can also request a read notification. It is requested
by including a Disposition-Notification header field with value
"read".
The absence of this header field or the presence of the header field
with empty value indicates that the IM Sender is not requesting any
IMDNs. The Disposition-Notification header fields can be comma
separated. The IM Sender MAY request more than one type of IMDN for
a single IM.
Future extension may define other disposition notifications not
defined in this document.
The formal syntax of the Disposition-Notification header field can be
found in Section 10. The following is an example CPIM body of an IM
where the IM Sender requests positive and negative delivery
notifications, but not read notification nor processing
notifications:
From: Alice <im:alice@example.com>
To: Bob <im:bob@example.com>
NS: imdn <urn:ietf:params:cpim-header fields:imdn>
imdn.Message-ID: 34jk324j
DateTime: 2006-04-04T12:16:49-05:00
imdn.Disposition-Notification: positive-delivery, negative-delivery
Content-type: text/plain
Content-length: 12
Hello World
7.1.2. Matching IMs with IMDNs
An IM Sender matches an IMDN to an IM by matching the Message-ID
header field value in the IM with the <message-id> element value in
the body of the IMDN. If the IM was delivered to multiple
recipients, the IM Sender uses the <recipient-uri> element and the
<original-recipient-uri> element in the XML body of the IMDN it
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received to determine if the IM was sent to multiple recipients and
to identify the IM Recipient that sent the IMDN.
7.1.3. Keeping State
This specification does not mandate the IM Sender to keep state for a
sent IM.
Once an IM Sender sends an IM containing an IMDN request, it MAY
preserve the IM context, principally the Message-ID, and other user-
identifiable information such as the IM subject or content, and date
and time it was sent. Without preservation of the IM context, the IM
Sender will not be able to correlate the IMDN with the IM it sent.
The IM Sender may find it impossible to preserve IM state if it has
limited resources or does not have non-volatile memory and then loses
power.
There is, however, the concept of "Sent Items" box in an application
that stores sent IMs. This "Sent Items" box has the necessary
information and may have a fancy user interface indicating the state
of a sent IM. Unique Message-ID for this purpose proves to be
useful. The length of time for items to remain in the "Sent Items"
box is a user choice. The user is usually free to keep or delete
items from the "Sent Items" box as she pleases or as the memory on
the device reaches capacity.
Clearly, if an IM Sender loses its sent items state (user deletes
items from the "Send Items" box), the client may use a different
display strategy in response to apparently unsolicited IMDNs.
This specification also does not mandate an IM Sender to run any
timers waiting for an IMDN. There are no time limits associated with
when IMDNs may be received.
IMDNs may legitimately never be received. On the other hand, and
IMDN may simply take a very long time. Some clients may choose to
purge the state associated with the sent IM. This is the reason for
adding the time stamp in the IM and having it returned in the IMDN.
This gives the user some opportunity of remembering what IM was sent.
For example if the IMDN indicates that the IM the user sent at 2 p.m.
last Thursday was delivered, the user has a chance of remembering
that they sent an IM at 2 p.m. last Thursday.
7.1.4. Aggregation of IMDNs
An IM Sender may send an IM to multiple recipients in one Transport
Protocol Message (typically using a URI-List server) and request
IMDNs. An IM Sender that requested an IMDNs MUST be prepared to
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receive multiple aggregated or non-aggregated IMDNs. See Section 8.2
for details.
7.2. IM Recipient
7.2.1. Constructing IMDNs
IM recipients examine the contents of the Disposition-Notification
header field of the CPIM message to determine if an IMDN must be
generated for that IM. Disposition-Notification header fields of
CPIM messages can include one or more values. This implies that IM
recipients may need to generate zero, one, or more IMDNs for that IM,
for example a delivery notification as well as a read notification.
In this case the IM Recipient MUST be able to construct multiple
IMDNs per IM. An IM Recipient MUST NOT construct more than one IMDN
per disposition type. I.e. It must not, for example, generate a
delivery notification indicating "delivered" then followed by a
delivery notification indicating "failed" for the same IM. If the IM
Sender requested only failure notifications and the IM was
successfully delivered, then no IMDNs will be generated.
The IM Recipient MUST NOT generate "processing" notifications.
Disposition-Notification header field MUST NOT appear in an IMDN
since it does not make sense and is therefore forbidden to request an
IMDN for an IMDN. IM Sender MUST ignore it if present. The IM
Sender MUST NOT send an IMDN to an IMDN.
An IMDN MUST contain a Message-ID header field. The same rules of
uniqueness for the Message-ID header field that appears in an IM
apply to an IMDN. The Message-ID header field in the IMDN is
different and unrelated to the one in the IM.
An IM may contain a IMDN-Record-Route header field (see Section 8 for
details). If IMDN-Record-Route header fields appear in the IM, the
IM Recipient constructing the IMDN MUST copy the contents of the
IMDN-Record-Route header fields into IMDN-Route header fields in the
IMDN and maintain the order. The IMDN is then sent to the URI in the
top IMDN-Route header field. IMDN-Record-Route header fields do not
make sense in an IMDN and therefore SHOULD NOT be placed in an IMDN.
The CPIM Content-Disposition header field must be set to the value
"notification". This indicates to the IM Sender that the message is
an IMDN to an IM it has earlier sent.
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7.2.1.1. Constructing Delivery Notifications
A delivery notification is constructed in a similar fashion as an IM,
using a CPIM body [2] that carries a Disposition Notification XML
document formatted according to the rules specified in Section 11.
The MIME type of the Disposition Notification XML document is
"message/imdn+xml".
An example CPIM body of IMDN looks like the following:
From: Bob <im:bob@example.com>
To: Alice <im:alice@example.com>
NS: imdn <urn:ietf:params:cpim-header fields:imdn>
imdn.Message-ID: d834jied93rf
Content-type: message/imdn+xml
Content-Disposition: notification
Content-length: ...
<?xml version="1.0" encoding="UTF-8"?>
<imdn xlmns="urn:ietf:params:xml:ns:imdn">
<message-id>34jk324j</message-id>
<datetime>2006-04-04T12:16:49-05:00</datetime>
<recipient-uri>im:bob@example.com</recipient-uri>
<original-recipient-uri>
im:bob@example.com</original-recipient-uri>
<disposition>
<delivery/>
</disposition>
<status>
<delivered/>
</status>
<note lang="en">The IM was successfully Delivered</note>
</imdn>
7.2.1.2. Constructing Read Notifications
A read notification is constructed in a similar fashion as the
delivery notification. See Section 7.2.1.1 for details.
An example looks like the following:
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From: Bob <im:bob@example.com>
To: Alice <im:alice@example.com>
NS: imdn <urn:ietf:params:cpim-header fields:imdn>
imdn.Message-ID: dfjkleriou432333
Content-type: message/imdn+xml
Content-Disposition: notification
Content-length: ...
<?xml version="1.0" encoding="UTF-8"?>
<imdn xlmns="urn:ietf:params:xml:ns:imdn">
<message-id>34jk324j</message-id>
<datetime>2006-04-04T12:16:49-05:00</datetime>
<recipient-uri>im:bob@example.com</recipient-uri>
<original-recipient-uri>
im:bob@example.com</original-recipient-uri>
<disposition>
<read/>
</disposition>
<status>
<read/>
</status>
<note lang="en">The IM has been read</note>
</imdn>
There are situations where the IM Recipient cannot determine if or
when the IM has been read. The IM Recipient in this case generates a
read notification with a <status> value of "error" to indicate an
internal error by the server. An example of this is when a SIP stack
with built in IMDN support is talking to an IM application and the IM
application never returned indicating that it has displayed the IM to
the user.
8. Intermediary Behaviour
In this context, application servers (including URI-List servers and
Store-and-Forward server) and gateways are defined as intermediaries.
A gateway is a server the translates between different IM systems
that different protocols.
A URI-List server may change the IM Recipient address from its own to
the address of the final recipient of that IM for every copy it makes
to be sent to the list members (see [12] for details). In this case,
the intermediary MUST add an Original-To header field to the IM
populating it with the address that was in the CPIM To header field
before it was changed. I.e. The Original-To header field is
populated with the intermediary address. An intermediary MUST NOT
add an Original-To header field if one already exists.
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An intermediary MAY choose to remain on the path of IMDNs for a
specific IM. It can do so by adding a CPIM IMDN-Record-Route header
field as the top IMDN-Record-Route header field and populating it
with its own address. An intermediary that does not support this
extension will obviously not add the IMDN-Record-Route header field.
This allows IMDNs to traverse directly from the IM Recipient to the
IM Sender even if the IM traversed an intermediary not supporting
this extension.
An intermediary receiving an IMDN checks the top IMDN-Route header
field. If that header field carries the intermediary address, the
intermediary pops that value and forwards the IMDN to the address
indicated in the now top IMDN-Route header field. If no IMDN-Route
header fields are present, the IMDN is forwarded to the address in
the CPIM To header field.
An intermediary MUST remove any information about the final
recipients of a list if the list membership is not disclosed. The
intermediary does that by removing the <recipient-uri> element and/or
<original-recipient-uri> element from the body of the IMDN before
forwarding it to the IM Sender.
8.1. Constructing Processing Notifications
Intermediaries are the only entities that construct processing
notifications. They do so only if the IM Sender has requested a
"processing" notification by including a Disposition-Notification
header field with value "processing".
The intermediary can create and send "processing" notifications
indicating that an IM has been processed or stored. The intermediary
MUST NOT send more than one IMDN for the same disposition type. I.e.
It must not send a "processing" notification indicating that an IM is
being "processed" followed by another IMDN indicating that the same
IM is "stored".
A "processing" notification is constructed in a similar fashion as
the delivery notification. See Section 7.2.1.1 for details.
An example looks like the following:
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Content-type: Message/CPIM
From: Bob <im:bob@example.com>
To: Alice <im:alice@example.com>
Content-type: message/imdn+xml
Content-Disposition: notification
Content-length: ...
<imdn>
<message-id>34jk324j</message-id>
<datetime>2006-04-04T12:16:49-05:00</datetime>
<recipient-uri>im:bob@example.com</recipient-uri>
<original-recipient-uri>
im:bob@example.com</original-recipient-uri>
<disposition>
<processing/>
</disposition>
<status>
<processed/>
</status>
<note lang="en">The IM has been processed</note>
</imdn>
There are situations where the intermediary cannot know the fate of
an IM. The intermediary in this case generates a processing
notification with a <status> value of "error" to indicate so.
8.2. Aggregation of IMDNs
In this context, URI-List servers are defined as intermediaries.
An intermediary may choose to aggregate IMDNs using local policy for
making such a decision or it may send individual IMDNs instead. When
a URI-List server receives an IM and decides to aggregate IMDNs, it
waits for a configurable period of time or until all recipients have
sent the IMDN (whichever comes first) before the URI-List server
sends an aggregated IMDN. Note that some IMDNs, for example read
notifications, may never come due to user settings. It is an
administrator configuration and an implementation issue how long to
wait before sending an aggregated IMDN and before a URI-List server
removes state for that IM.
A URI-List server MAY choose to send multiple aggregated IMDNs. A
timer can be started and when it fires, the URI-List server can
aggregate whatever IMDNs it has so far for that IM, send the
aggregated IMDN and restart the timer for the next batch. This is
needed for scenarios where the IM Sender has requested more than one
IMDN for a specific IM, for example, delivery notifications as well
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as read notifications, or when the URI-List server is short on
resources and chooses to prioritise forwarding IMs over IMDNs.
A second timer can be running and when it fires, the state of the IM
is deleted. In this case, the URI-List server consumes any IMDNs
that might arrive after that time.
A URI-List server MAY aggregate IMDNs for the case where the list
membership information is not disclosed. There may be scenarios
where the URI-List server starts sending aggregated IMDNs and switch
to indivdual ones or visa versa. A timer firing so ofter may in fact
have that effect.
The aggregated IMDN is constructed using the multipart/mixed MIME
type and including all the received IMDNs as message/imdn+xml as
individual payloads.
There are scenarios where an intermediary needs to generate IMDNs,
see Section 12.2 for further details.
9. Identifying Messages
Messages are typically carried in a transport protocol like SIP [8].
The message is an IM if the content-type header field field present
in it has a value that is NOT "message/imdn+xml".
A message is identified as a delivery notification by examining its
contents. The message is a delivery notification if: the Content-
type header field present has a value of "message/imdn+xml", the
Content-Disposition header field field has a value of "notification",
and the <disposition> element in that xml body has a sub-element
<delivery>.
A message is identified as a processing notification or read
notification in a similar fashion as a delivery notification. The
difference is that the <disposition> element in that xml body has a
sub-element of <processing> and <read> respectively.
10. header fields Formal Syntax
The following syntax specification uses the message header field
syntax as described in Section 3 of RFC3862 [2].
header field syntax is described without a namespace qualification.
Following the rules in RFC3862 [2], header field names and other text
are case sensitive and MUST be used as given, using exactly the
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indicated upper-case and lower-case letters.
Disposition-Notification =
"Disposition-Notification" ": " [(notify-req *(COMMA notify-req))]
notify-req =
("negative-delivery" / "positive-delivery" /
"processing" / "read" / Token) *(SEMI disp-notif-params)
disp-notify-params = generic-param
Message-ID = "Message-ID" ": " Token
Original-To = "Original-To" ": " [ Formal-name ] "<" URI ">"
IMDN-Record-Route =
"IMDN-Record-Route" ": " [ Formal-name ] "<" URI ">"
IMDN-Route = "IMDN-Route" ": " [ Formal-name ] "<" URI ">"
11. IMDN Format
11.1. Structure of XML-Encoded IMDN Payload
An IMDN Payload is an XML document [7] that MUST be well-formed and
MUST be valid according to schemas, including extension schemas,
available to the validater and applicable to the XML document. The
IMDN Payload MUST be based on XML 1.0 and MUST be encoded using
UTF-8.
The namespace identifier for elements defined by this specification
is a URN [4], using the namespace identifier 'ietf' defined by [5]
and extended by [3]. This urn is: urn:ietf:params:xml:ns:imdn.
This namespace declaration indicates the namespace on which the IMDN
is based.
The root element is <imdn>. The <imdn> element has sub-elements,
namely <message-id>, <datetime>, <recipient-uri>, <original-
recipient-uri>, <subject>, <disposition>, <status>, and <note>.
Those elements are described in details in the following sections.
<disposition> and <status> can be extended in the future to include
new sub-elements not defined in this document. Those new elements
MUST be defined in an RFC.
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11.1.1. The <message-id> Element
The <message-id> element is mandatory according to the XML schema and
carries the message id that appeared in the Message-ID header field
of the IM.
11.1.2. The <datetime> Element
The <datetime> element is mandatory and carries the date and time the
IM was sent (not the IMDN). This information is obtained from the
DateTime header field of the IM.
11.1.3. The <recipient-uri> Element
The <recipient-uri> element is optional and carries the URI of the
final recipient. This information is obtained from the CPIM To
header field of the IM.
11.1.4. The <original-recipient-uri> Element
The <original-recipient-uri> element is optional and carries the URI
of the original recipient. It MUST be present if the IM carried the
Original-To header field. This information is obtained from the
Original-To header field of the IM.
11.1.5. The <subject> Element
The <subject> element is optional and carries the text that was in
the Subject header field, if any. This allows for a human level
correlation between an IM and an IMDN.
11.1.6. The <disposition> Element
The <disposition> element is mandatory and carries the disposition
type that the IM Sender requested and is being reported. It can
carry one of the sub-elements <delivery>, <processing>, <read> or any
other future extension.
11.1.7. The <status> Element
The <status> element is mandatory and carries the result of the
disposition request in the <disposition> element. For disposition
type <delivery>, it can carry one of the sub-elements <delivered>,
<failed>, <forbidden> or <error>. For disposition type <read>, it
can carry one of the sub-elements <read>, <forbidden> or <error>.
For disposition type <processing>, it can carry one of the sub-
elements <processed>, <stored>, <forbidden> or <error>. <forbidden>
means the disposition was denied. <error> means internal server
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error. It can also carry any other future extension.
11.1.8. The <note> Element
The <note> element is optional and carries a human readable text. It
has the "lang" attribute that indicates the language the text is
written in.
11.2. MIME Type for IMDN Paylaod
The MIME type for the IMDN Payload is "message/imdn+xml". The IMDN
MUST identify the payload as MIME type "message/imdn+xml" in the
Content-type header field.
11.3. The RelaxNG Schema
<?xml version="1.0" encoding="UTF-8"?>
<grammar
xmlns="http://relaxng.org/ns/structure/1.0"
xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes"
ns="urn:ietf:params:xml:ns:imdn">
<start>
<element name="imdn">
<element name="message-id">
<data type="token"/>
</element>
<element name="datetime">
<data type="string"/>
</element>
<optional>
<element name="recipient-uri">
<data type="anyURI"/>
</element>
<element name="original-recipient-uri">
<data type="anyURI"/>
</element>
<element name="subject">
<data type="string"/>
</element>
</optional>
<choice>
<ref name="deliveryNotification"/>
<ref name="readNotification"/>
<ref name="processingNotification"/>
<zeroOrMore>
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<empty/>
</zeroOrMore>
</choice>
<ref name="note"/>
<zeroOrMore>
<ref name="Extension"/>
</zeroOrMore>
<zeroOrMore>
<ref name="anyIMDN"/>
</zeroOrMore>
</element>
</start>
<define name="deliveryNotification">
<element name="disposition">
<element name="delivery">
<empty/>
</element>
</element>
<element name="status">
<choice>
<element name="delivered">
<empty/>
</element>
<element name="failed">
<empty/>
</element>
<ref name="commonDispositionStatus"></ref>
<zeroOrMore>
<ref name="Extension"/>
</zeroOrMore>
<zeroOrMore>
<ref name="anyIMDN"/>
</zeroOrMore>
</choice>
</element>
</define>
<define name="readNotification">
<element name="disposition">
<element name="read">
<empty/>
</element>
</element>
<element name="status">
<choice>
<element name="read">
<empty/>
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</element>
<ref name="commonDispositionStatus"></ref>
<zeroOrMore>
<ref name="Extension"/>
</zeroOrMore>
<zeroOrMore>
<ref name="anyIMDN"/>
</zeroOrMore>
</choice>
</element>
</define>
<define name="processingNotification">
<element name="disposition">
<element name="processing">
<empty/>
</element>
</element>
<element name="status">
<choice>
<element name="processed">
<empty/>
</element>
<element name="stored">
<empty/>
</element>
<ref name="commonDispositionStatus"></ref>
<zeroOrMore>
<ref name="Extension"/>
</zeroOrMore>
<zeroOrMore>
<ref name="anyIMDN"/>
</zeroOrMore>
</choice>
</element>
</define>
<define name="commonDispositionStatus">
<choice>
<element name="forbidden">
<empty/>
</element>
<element name="error">
<empty/>
</element>
<zeroOrMore>
<ref name="Extension"/>
</zeroOrMore>
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<zeroOrMore>
<ref name="anyIMDN"/>
</zeroOrMore>
</choice>
</define>
<define name="note">
<element name="note">
<optional>
<attribute>
<name ns="http://www.w3.org/XML/1998/namespace">
lang
</name>
<data type="language"/>
</attribute>
</optional>
<data type="string"/>
</element>
</define>
<define name="Extension">
<empty/>
</define>
<define name="anyIMDN">
<element>
<anyName>
<except>
<nsName ns="urn:ietf:params:xml:ns:imdn"/>
<nsName ns=""/>
</except>
</anyName>
<mixed>
<zeroOrMore>
<choice>
<attribute>
<anyName/>
</attribute>
<ref name="anyIMDN"/>
</choice>
</zeroOrMore>
</mixed>
</element>
</define>
</grammar>
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12. Transporting Messages using SIP
12.1. Endpoint Behaviour
12.1.1. Sending Requests
A SIP MESSAGE request is constructed using RFC 3428 [9]. The
Content-type header field indicates the MIME type of the request
payload. When using this extension, the Content-type header field
MUST be of MIME type "message/cpim" [2] for both IMs and IMDNs. The
payload is constructed according to Section 7.
A SIP MESSAGE request to multiple recipients is constructed in a
similar manner as a SIP MESSAGE request to a single recipient. The
differences are indicated in [12].
12.1.2. Sending Responses
An endpoint receiving a SIP MESSAGE request constructs a SIP response
according to RFC3428 [9]. Of course, an endpoint will send a
response to the MESSAGE request regardless of they type of message
(IM or IMDN) is has received, or the disposition type it has been
asked for.
12.1.3. Receiving Requests
12.1.3.1. Instant Message
A SIP MESSAGE request is identified as an IM by examining its
contents according to Section 9.
If an IM Recipient received a SIP MESSAGE request that is an IM that
requested a positive-delivery notification, and that IM Recipient has
constructed and sent a SIP 2xx class response, it MAY generate a
positive-delivery notification after making sure that the IM has been
delivered to the user or application (a gateway, for example, can
generate a 2xx response before it has been guaranteed that the final
recipient has actually received the IM). The positive-delivery
notification is constructed according to Section 7.2.1.1. The
message is then placed as the payload in a SIP MESSAGE request.
If an IM Recipient received a SIP MESSAGE request that is an IM that
requested a negative-delivery, and that IM Recipient has constructed
and sent a 2xx class response, it SHOULD generate a negative-delivery
notification if it learnt that the final recipient or application did
not receive the IM (a gateway, for example, can generate a 2xx
response before it has been guaranteed that the final recipient has
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actually received the IM). The negative-delivery notification is
constructed according to Section 7.2.1.1. The message is then placed
as the payload in a SIP MESSAGE request.
If an IM Recipient received a SIP MESSAGE request that is an IM that
requested a negative-delivery notification, and the IM Recipient has
constructed and sent an non-2xx final response, it MUST NOT generate
a negative-delivery notification.
If an IM Recipient received a SIP MESSAGE request that is an IM that
requested a read notification, and that IM Recipient has constructed
and sent a SIP 2xx class response, it MAY generate a read
notification after making sure that the IM has been presented to the
user or application. It is outside the scope of this document how
such determination can be made. Note that the option to send a read
notification or not can be left to the user. An application may
allow a user to configure such choice. The read notification is
constructed according to Section 7.2.1.2. The message is then placed
as the payload in a SIP MESSAGE request.
For IMDNs, the SIP Request-URI and the SIP To header field are
populated using the address that appeared in the SIP From header
field field in the IM.
12.1.3.2. Delivery Notification
A SIP MESSAGE request is identified as delivery notification by
examining its contents according to Section 9.
12.1.3.3. Read Notification
A SIP MESSAGE request is identified as read notification by examining
its contents according to Section 9.
12.2. Intermediary Behaviour
In this context, application servers (including URI-List servers and
Store-and-Forward server) and gateways are defined as intermediaries.
SIP Proxies MUST NOT generate IMDNs but MUST forward them like any
other sip request.
A SIP MESSAGE request to multiple recipients is forwarded according
to [12].
If an intermediary generates a SIP 2xx class response to a SIP
MESSAGE request it has received that is an IM, it examines if the
body was of type "message/cpim". If so, it checks if there is the
header field Disposition-Notification with a value "positive-
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delivery" and/or "negative-delivery". If so, it MUST send a delivery
notification after receiving a transactional final response for the
IM.
If the Disposition-Notification header field contains a value of
"positive-delivery", the intermediary MUST NOT generate a delivery
notification if it receives a SIP 2xx class response for the sent IM.
This is in anticipation of a failure downstream after a 2xx response
has been generated.
If the Disposition-Notification header field contains a value of
"negative-delivery", the intermediary SHOULD generate a delivery
notification if it receives a SIP 4xx, 5xx or 6xx class final
response for the sent IM. If it has received a SIP 2xx class
response followed by a negative-delivery notification, the
intermediary forwards that negative-delivery notification or
aggragates it.
If the Disposition-Notification header field contains a value of
"processing", the intermediary MAY generate a processing notification
after it has forwarded or stored the IM. The rest of the procedures
in Section 8.1 apply.
The procedure for generating such IMDN is the same as that of an IM
Recipient (Section 7.2.1.1).
The <recipient-uri> element of the XML body is populated with the URI
of the IM Recipient.
If an intermediary receives a SIP MESSAGE request carrying a positive
delivery notification or a read notification, it forwards it using
the rules in Section 8.
13. Transporting Messages using MSRP
MSRP already provides a built-in mechanism to supply positive and
negatie delivery reports.
While MSRP does not provide a built-in Read or Processing
notification dispositions, those are generally not considered as
useful information for session IM. This is because the assumption
behind MSRP is that SEND requests do not reach a mailbox where
incoming IMs have to be open, but to an application that renders
sequentially those incoming IMs, providing the session experience.
This kind of applications has no means of identifying when a user has
read the IM and therefore cannot be useful information for the
sender.
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IMDN use cases for MSRP have not been fully explored. If new
requirements arise in the future determining the need for IMDN in
MSRP, new specifications can be drafted.
14. Security Considerations
IMDNs provide a fine-grained view of the activity of the IM Recipient
and thus deserves particularly careful confidentiality protection so
that only the intended recipient of the IMDN will receive the IMDN
(in most cases, the intended recipient of the IMDN is the IM Sender).
Since IMDNs are carried by using the IM protocol itself, all security
considerations of the underlying IM protocol also apply to the IMDNs.
The threats in the IMDN system, over and beyond the threats inherent
to IM include the following:
o A malicious endpoint attempts to send messages to a user that
would normally not wish to receive messages from that endpoint by
convincing the IMDN system to "bounce" an IMDN from an
unsuspecting endpoint to the user.
o A malicious endpoint attempts to flood a IM Sender with IMDNs by
convincing a URI-List server to send IMDNs to an unsuspecting IM
Sender.
o A malicious node in the network that attempts to modify an IMDN
from a IM Recipient.
o A malicious intermediary attempts to forward an IMDN from an IM
Recipient to the IM Sender, where the IM Recipient would not
normally forward the IMDN to that IM Sender if the IM Recipient
knew the identity of the IM Sender.
o A malicious endpoint that attempts to fish for a Request-URI of an
endpoint beyond an intermediary , where the endpoint would
normally wish to keep its identity private from the malicious
endpoint.
o A malicious node in the network that attempts to eavesdrop on IMDN
traffic to, for example, learn Request-URI or traffic pattern
information.
o A malicious node in the network attempts to stage a denial of
service attack on an intermediary by requesting a large list
expansion.
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The protocol cannot protect against attacks that include the
following:
o A malicious intermediary directly revealing the identity of a
downstream endpoint that would not normally wish its identity
revealed. Keeping such information private is an intermediary
implementation issue.
o A malicious IM Recipient that alters the time of the IMDN. There
is no protocol mechanism for ensuring the IM Recipient does not
lie about the time or purposely holds an IMDN for transmission to
make it appear that the user read an IM later than they actually
did.
o A deletion attack on an IMDN. This is a trade-off between privacy
and security. The privacy considerations allow the IM Recipient
to silently ignore an IMDN request. Any mechanism that would
reliably indicate that a malicious node deleted a IM Recipient's
IMDN would also serve the purpose of detecting a IM Recipient that
chose not to issue an IMDN.
To combat eavesdropping, modification, and man-in-the-middle attacks,
we require some level of authentication and integrity protections.
That said, there are circumstances where strong integrity would be
overkill. The presumption is the IM Sender has and sets the
expectation for the level of protection. The procedures for
integrity protection are as follows.
o If the IM Recipient has a certificate, it MUST sign the IMDN.
o If the IM is encrypted, the IM Recipient or intermediary MUST
encrypt the IMDN body, as an attacker may attempt to discern the
user's activity profile and identity from sniffing IMDNs on the
network.
o The two above rules are cumulative.
The IM Recipient or intermediary MUST be capable of loading a user
certificate.
An attacker can mount a distributed denial of service attack on a
node by sending lots of IMs to the node with IMDN requests. Note
that this is the same problem as there is without IMDN; IMDN simply
linearly increases the load on the node under attack. One can
mitigate, but not eliminate this threat by the endpoint immediately
ignoring requests that are not authenticated.
Likewise, an attacker can mount a denial of service attack on an
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intermediary by asking the intermediary to explode a large list.
The following security considerations apply when using IMDNs:
14.1. Forgery
IMs can be forged. To protect against that, an IM can be signed. An
intermediary that receives a signed message and needs to modify any
part of it that is included in the signature (like adding an
Original-To header field to the CPIM header fields), MUST consume the
IM and create a new copy of it that the intermediary signs itself.
IMDNs may be forged as easily as ordinary IMs. Endpoints and
intermediaries that wish to make automatic use of IMDNs should take
appropriate precautions to minimize the potential damage from denial-
of-service attacks. Security threats related to forged IMDNs include
the sending of a falsified IMDN when the indicated disposition of the
IM has not actually occurred. For example, read notification could
be forged to indicate that a IM Recipient has read the IM.
Unsolicited IMDNs is also another form of forgery.
14.2. Confidentiality
There may be cases where an IM Recipient does not wish to reveal the
information that he has received or in fact read the IM. In this
situation, it is acceptable for the IM Recipient to silently ignore
requests for an IMDN. It is strongly RECOMMENDED that the IM
Recipient obtain the user's consent before sending an IMDN.
Circumstances where the IM Recipient does not ask for the user's
consent include IM systems that, for regulatory reasons, are required
to issue an IMDN, such as in the health care field or financial
community.
An IM Recipient can obtain such consent by a prompt or dialog box on
a per-IM basis, globally through the user's setting of a preference,
or other, user-configurable mechanism. The user might also indicate
globally that IMDNs are never to be sent or that a "forbidden" IMDN
status is always sent in response to a request for an IMDN.
There are situations where a user sends an IM and requests IMDNs to a
list who's member information is not disclosed. In this situation,
the user will learn of the list members. Therefore, in this case,
the URI-List server MUST remove any information about list members.
If the number of members in the list is also not disclosed, the URL-
List server MUST only deliver one aggregated IMDN. Alternatively,
the URI-list server MAY reject the IM.
An unencrypted IMDN could reveal confidential information about an
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encrypted IM. It is a MUST that the same level of security applied
to an IM to be applied to its IMDNs. For example, if an IM is signed
and encrypted, and IMDN must also be signed and encrypted.
14.3. Non-Repudiation
IMDNs cannot be relied on as a guarantee that an IM was or was not
seen by the user. Even if IMDNs are not actively forged, they may be
lost in transit. The IMDN issuing mechanism may be bypassed in some
manner by the IM Recipient.
15. IANA Considerations
15.1. message/imdn+xml MIME TYPE
This document registers a new MIME type "message/imdn+xml", and
registers a new XML namespace.
This specification follows the guidelines of RFC3023 [6].
MIME media type: message
MIME subtype name: imdn+xml
Mandatory parameters: none
Optional parameters: Same as charset parameter application/xml as
specified in RFC 3023 [6].
Encoding considerations: Same as encoding considerations of
application/xml as specified in RFC 3023 [6].
Security considerations: See section 10 of RFC 3023 [6] and
Section 14 of this document.
Interoperability considerations: none.
Published specification: This document.
Applications which use this media type: This document type is used to
support SIP based instant messaging.
Additional information: None
Magic number: None
File extension: .cl or .xml
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Macintosh file type code: "TEXT"
Personal and email address for further information: Hisham Khartabil
(hisham.khartabil@telio.no)
Intended Usage: COMMON
Author/change controller: The IETF .
15.2. URN Sub-Namespace Registration for urn:ietf:params:xml:ns:imdn
This section registers a new XML namespace, as per guidelines in the
IETF XML Registry [3].
URI: The URI for this namespace is urn:ietf:params:xml:ns:imdn.
Registrant Contact: IETF, SIMPLE working group, Hisham Khartabil
(hisham.khartabil@telio.no) .
15.3. Schema Registration
This section registers a new XML schema per the procedures in [3].
URI: urn:ietf:params:xml:ns:imdn
Registrant Contact: IETF, SIMPLE working group, Hisham Khartabil
(hisham.khartabil@telio.no)
The XML for this schema can be found as the sole content of
Section 11.3.
15.4. Message/CPIM header field registration
This document registers the following message/cpim header fields in
the cpim-header fields registry:
Disposition-Notification - [RFCXXXX]
Message-ID - [RFCXXXX]
Original-To - [RFCXXXX]
IMDN-Record-Route - [RFCXXXX]
IMDN-Route - [RFCXXXX].
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15.5. Content-Disposition: notification
This document registers one new Content-Disposition header field
"disposition-types": notification. The authors request that this
values be recorded in the IANA registry for Content-Dispositions.
Descriptions of this "disposition-types", including motivation and
examples, are given in Section 7.2.1.1 and Section 9. Short
descriptions suitable for the IANA registry are: notification the
body of the message is a notification according to an earlier request
for a disposition notification to an instant message
16. Acknowledgements
The authors would like to thank Paul Kyzivat, Ben Campbell, Adam
Roach, Gonzalo Camarillo, Sean Olson, Eva Leppanen, Miguel Garcia,
Eric McMurry and Jari Urpalainen for their comments and support.
17. References
17.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Klyne, G. and D. Atkins, "Common Presence and Instant Messaging
(CPIM): Message Format", RFC 3862, August 2004.
[3] Mealling, M., "The IETF XML Registry", RFC 3688, January 2004.
[4] Moats, R., "The URN Syntax", RFC 2141, May 1997.
[5] Moats, R., "The URN Namespace for IETF Documents", RFC 2648,
August 1999.
[6] Murata, M., "XML Media Types", RFC 3023, March 1997.
[7] Bray, T., "Extensible Markup Language (XML) 1.0 (Second
Edition)", W3C CR CR-xml11-20011006, October 2000.
17.2. Informative References
[8] Rosenberg et al., J., Shulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. Schooler,
"SIP: Session Initiation Protocol", RFC 3261, June 2002.
[9] Campbell, B., "SIP Extension for Instant Messaging", RFC 3428,
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December 2002.
[10] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001.
[11] Fajman, R., "An Extensible Message Format for Message
Disposition Notifications", RFC 2298, March 1998.
[12] Garcia-Martin, M. and G. Camarillo, "Multiple-Recipient MESSAGE
Requests in SIP", draft-ietf-sip-uri-list-message-01.txt,
January 2007.
Authors' Addresses
Eric Burger
BEA Systems, Inc.
4 Van de Graaff Dr.
Burlington, MA 01803
USA
Phone: +1 781 993 7437
Fax: +1 603 457 5933
Email: eric.burger@bea.com
Hisham Khartabil
Melbourne
Australia
Phone: +61 416 108 890
Email: hisham.khartabil@gmail.com
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Full Copyright Statement
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