rfc2447 - iCalendar Message-Based Interoperability Protocol (iMIP)

Network Working Group F. Dawson
Request for Comments: 2447 Lotus
Category: Standards Track S. Mansour
Netscape
S. Silverberg
Microsoft
November 1998

iCalendar Message-Based Interoperability Protocol
(iMIP)

Status of this Memo

This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.

Abstract

This document, [iMIP], specifies a binding from the iCalendar
Transport-independent Interoperability Protocol (iTIP) to Internet
email-based transports. Calendaring entries defined by the iCalendar
Object Model [iCAL] are composed using constructs from RFC-822">[RFC-822],
RFC-2045">[RFC-2045], RFC-2046">[RFC-2046], RFC-2047">[RFC-2047], RFC-2048">[RFC-2048] and RFC-2049">[RFC-2049].

This document is based on discussions within the Internet Engineering
Task Force (IETF) Calendaring and Scheduling (CALSCH) working group.
More information about the IETF CALSCH working group activities can
be found on the IMC web site at http://www.imc.org, the IETF web site
at http://www.ietf.org/html.charters/calsch-charter.html. Refer to
the references within this document for further information on how to
access these various documents.

Dawson, et. al. Standards Track [Page 1]

RFC 2447 iMIP November 1998

Table of Contents

1 INTRODUCTION........................................................2
1.1 RELATED MEMOS ...................................................2
1.2 FORMATTING CONVENTIONS ..........................................3
1.3 TERMINOLOGY .....................................................4
2 MIME MESSAGE FORMAT BINDING.........................................4
2.1 MIME MEDIA TYPE .................................................4
2.2 SECURITY ........................................................4
2.2.1 Authorization ...............................................4
2.2.2 Authentication ..............................................5
2.2.3 Confidentiality .............................................5
2.3 RFC-822">[RFC-822] ADDRESSES .............................................5
2.4 CONTENT TYPE ....................................................5
2.5 CONTENT-TRANSFER-ENCODING .......................................6
2.6 CONTENT-DISPOSITION .............................................6
3 SECURITY CONSIDERATIONS.............................................7
4 EXAMPLES............................................................8
4.1 SINGLE COMPONENT WITH AN ATTACH PROPERTY ........................8
4.2 USING MULTIPART ALTERNATIVE FOR LOW FIDELITY CLIENTS ............8
4.3 SINGLE COMPONENT WITH AN ATTACH PROPERTY AND INLINE ATTACHMENT ..9
4.4 MULTIPLE SIMILAR COMPONENTS ....................................10
4.5 MULTIPLE MIXED COMPONENTS ......................................11
4.6 DETAILED COMPONENTS WITH AN ATTACH PROPERTY ....................13
5 RECOMMENDED PRACTICES..............................................14
5.1 USE OF CONTENT AND MESSAGE IDS .................................14
6 BIBLIOGRAPHY.......................................................15
7 AUTHORS' ADDRESSES.................................................16
8 FULL COPYRIGHT STATEMENT...........................................18

1 Introduction

This binding document provides the transport specific information
necessary convey iCalendar Transport-independent Interoperability
Protocol (iTIP) over MIME as defined in RFC-822">[RFC-822] and RFC-2045">[RFC-2045].

1.1 Related Memos

Implementers will need to be familiar with several other memos that,
along with this memo, form a framework for Internet calendaring and
scheduling standards.

This document, [iMIP], specifies an Internet email binding for iTIP.

[iCAL] - specifies a core specification of objects, data types,
properties and property parameters;

Dawson, et. al. Standards Track [Page 2]

RFC 2447 iMIP November 1998

[iTIP] - specifies an interoperability protocol for scheduling
between different implementations;

This memo does not attempt to repeat the specification of concepts or
definitions from these other memos. Where possible, references are
made to the memo that provides for the specification of these
concepts or definitions.

1.2 Formatting Conventions

The mechanisms defined in this memo are defined in prose. In order to
refer to elements of the calendaring and scheduling model, core
object or interoperability protocol defined in [iCAL] and [iTIP] some
formatting conventions have been used.

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 RFC-2119">[RFC-2119].

Calendaring and scheduling roles are referred to in quoted-strings of
text with the first character of each word in upper case. For
example, "Organizer" refers to a role of a "Calendar User" within the
scheduling protocol defined by [iTIP].

Calendar components defined by [iCAL] are referred to with
capitalized, quoted-strings of text. All calendar components start
with the letter "V". For example, "VEVENT" refers to the event
calendar component, "VTODO" refers to the to-do calendar component
and "VJOURNAL" refers to the daily journal calendar component.

Scheduling methods defined by [iTIP] are referred to with
capitalized, quoted-strings of text. For example, "REQUEST" refers to
the method for requesting a scheduling calendar component be created
or modified, "REPLY" refers to the method a recipient of a request
uses to update their status with the "Organizer" of the calendar
component.

Properties defined by [iCAL] are referred to with capitalized,
quoted-strings of text, followed by the word "property". For example,
"ATTENDEE" property refers to the iCalendar property used to convey
the calendar address of a calendar user.

Property parameters defined by [iCAL] are referred to with lower
case, quoted-strings of text, followed by the word "parameter". For
example, "value" parameter refers to the iCalendar property parameter
used to override the default data type for a property value.

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RFC 2447 iMIP November 1998

1.3 Terminology

The email terms used in this memo are defined in RFC-822">[RFC-822] and [RFC-
2045]. The calendaring and scheduling terms used in this memo are
defined in [iCAL] and [iTIP].

2 MIME Message Format Binding

This section defines the message binding to the MIME electronic mail
transport.

The sections below refer to the "originator" and the "respondent" of
an iMIP message. Typically, the originator is the "Organizer" of an
event. The respondent is an "Attendee" of the event.

The RFC-822">[RFC-822] "Reply-To" header typically contains the email address
of the originator or respondent of an event. However, this cannot be
guaranteed as Mail User Agents (MUA) are not required to enforce iMIP
semantics.

2.1 MIME Media Type

A MIME entity containing content information formatted according to
this document will be referenced as a "text/calendar" content type.
It is assumed that this content type will be transported through a
MIME electronic mail transport.

2.2 Security

This section addresses several aspects of security including
Authentication, Authorization and Confidentiality. Authentication and
confidentiality can be achieved using RFC-1847">[RFC-1847] that specifies the
Security Multiparts for MIME. This framework defines new content
types and subtypes of multipart: signed and encrypted. Each contains
two body parts: one for the protected data and another for the
control information necessary to remove the protection.

2.2.1 Authorization

In [iTIP] messages, only the "Organizer" is authorized to modify or
cancel calendar entries they organize. That is, spoof@xyz.com is not
allowed to modify or cancel a meeting that was organized by
a@example.com. Furthermore, only the respondent has the authorization
to indicate their status to the "Organizer". That is, the "Organizer"
must ignore an [iTIP] message from spoof@xyz.com that declines a
meeting invitation for b@example.com.

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RFC 2447 iMIP November 1998

Implementations of iMIP SHOULD verify the authenticity of the creator
of an iCalendar object before taking any action. The methods for
doing this are presented later in this document.

RFC-1847">[RFC-1847] Message flow in iTIP supports someone working on behalf of
a "Calendar User" through use of the "sent-by" parameter that is
associated with the "ATTENDEE" and "ORGANIZER" properties. However,
there is no mechanism to verify whether or not a "Calendar User" has
authorized someone to work on their behalf. It is left to
implementations to provide mechanisms for the "Calendar Users" to
make that decision.

2.2.2 Authentication

Authentication can be performed using an implementation of RFC-1847">[RFC-1847]
"multipart/signed" that supports public/private key certificates.
Authentication is possible only on messages that have been signed.
Authenticating an unsigned message may not be reliable.

2.2.3 Confidentiality

To ensure confidentiality using iMIP implementations should utilize
RFC-1847">[RFC-1847]-compliant encryption. The protocol does not restrict a
"Calendar User Agent" (CUA) from forwarding iCalendar objects to
other users or agents.

2.3 RFC-822">[RFC-822] Addresses

The calendar address specified within the "ATTENDEE" property in an
iCalendar object MUST be a fully qualified, RFC-822">[RFC-822] address
specification for the corresponding "Organizer" or "Attendee" of the
"VEVENT" or "VTODO".

Because [iTIP] does not preclude "Attendees" from forwarding
"VEVENTS" or "VTODOS" to others, the RFC-822">[RFC-822] "Sender" value may not
equal that of the "Organizer". Additionally, the "Organizer" or
"Attendee" cannot be reliably inferred by the RFC-822">[RFC-822] "Sender" or
"Reply-to" values of an iMIP message. The relevant address MUST be
ascertained by opening the "text/calendar" MIME body part and
examining the "ATTENDEE" and "ORGANIZER" properties.

2.4 Content Type

A MIME body part containing content information that conforms to this
document MUST have an RFC-2045">[RFC-2045] "Content-Type" value of
"text/calendar". The RFC-2045">[RFC-2045] "Content-Type" header field must also
include the type parameter "method". The value MUST be the same as
the value of the "METHOD" calendar property within the iCalendar

Dawson, et. al. Standards Track [Page 5]

RFC 2447 iMIP November 1998

object. This means that a MIME message containing multiple iCalendar
objects with different method values must be further encapsulated
with a "multipart/mixed" MIME entity. This will allow each of the
iCalendar objects to be encapsulated within their own "text/calendar"
MIME entity.

A "charset" parameter MUST be present if the iCalendar object
contains characters that are not part of the US-ASCII character set.
RFC-2046">[RFC-2046] discusses the selection of an appropriate "charset" value.

The optional "component" parameter defines the iCalendar component
type contained within the iCalendar object.

The following is an example of this header field with a value that
indicates an event message.

Content-Type:text/calendar; method=request; charset=UTF-8;
component=vevent

The "text/calendar" content type allows for the scheduling message
type to be included in a MIME message with other content information
(i.e., "multipart/mixed") or included in a MIME message with a
clear-text, human-readable form of the scheduling message (i.e.,
"multipart/alternative").

In order to permit the information in the scheduling message to be
understood by MIME user agents (UA) that do not support the
"text/calendar" content type, scheduling messages SHOULD be sent with
an alternative, human-readable form of the information.

2.5 Content-Transfer-Encoding

Note that the default character set for iCalendar objects is UTF-8. A
transfer encoding SHOULD be used for iCalendar objects containing any
characters that are not part of the US-ASCII character set.

2.6 Content-Disposition

The handling of a MIME part should be based on its RFC-2045">[RFC-2045]
"Content-Type". However, this is not guaranteed to work in all
environments. Some environments handle MIME attachments based on
their file type or extension. To operate correctly in these
environments, implementations may wish to include a "Content-
Disposition" property to define a file name.

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RFC 2447 iMIP November 1998

3 Security Considerations

The security threats that applications must address when implementing
iTIP are detailed in [iTIP]. Two spoofing threats are identified:
Spoofing the "Organizer", and Spoofing an "Attendee". To address
these threats, the originator of an iCalendar object must be
authenticated by a recipient. Once authenticated, a determination can
be made as to whether or not the originator is authorized to perform
the requested operation. Compliant applications MUST support signing
and encrypting text/calendar attachments using a mechanism based on
Security Multiparts for MIME RFC-1847">[RFC-1847] to facilitate the
authentication the originator of the iCalendar object.
Implementations MAY provide a means for users to disable signing and
encrypting. The steps are described below:

1. The iCalendar object MUST be signed by the "Organizer" sending an
update or the "Attendee" sending a reply.

2. Using the RFC-1847">[RFC-1847]-compliant security mechanism, determine who
signed the iCalendar object. This is the "signer". Note that the
signer is not necessarily the person sending an e-mail message since
an e-mail message can be forwarded.

3. Correlate the signer to an "ATTENDEE" property in the iCalendar
object. If the signer cannot be correlated to an "ATTENDEE" property,
ignore the message.

4. Determine whether or not the "ATTENDEE" is authorized to perform
the operation as defined by [iTIP]. If the conditions are not met,
ignore the message.

5. If all the above conditions are met, the message can be processed.

To address the confidentiality security threats, signed iMIP messages
SHOULD be encrypted by a mechanism based on Security Multiparts for
MIME RFC-1847">[RFC-1847].

It is possible to receive iMIP messages sent by someone working on
behalf of another "Calendar User". This is determined by examining
the "sent-by" parameter in the relevant "ORGANIZER" or "ATTENDEE"
property. [iCAL] and [iTIP] provide no mechanism to verify that a
"Calendar User" has authorized someone else to work on their behalf.
To address this security issue, implementations MUST provide
mechanisms for the "Calendar Users" to make that decision before
applying changes from someone working on behalf of a "Calendar User".

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RFC 2447 iMIP November 1998

4 Examples

4.1 Single Component With An ATTACH Property

This minimal message shows how an iCalendar object references an
attachment. The attachment is accessible via its URL.

From: sman@netscape.com
To: stevesil@microsoft.com
Subject: Phone Conference
Mime-Version: 1.0
Content-Type:text/calendar; method=REQUEST; charset=US-ASCII
Content-Transfer-Encoding: 7bit

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
ORGANIZER:mailto:sman@netscape.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:sman@netscape.com
ATTENDEE;RSVP=YES:mailto:stevesil@microsoft.com
DTSTAMP:19970611T190000Z
DTSTART:19970701T210000Z
DTEND:19970701T230000Z
SUMMARY:Phone Conference
DESCRIPTION:Please review the attached document.
UID:calsvr.example.com-873970198738777
ATTACH:ftp://ftp.bar.com/pub/docs/foo.doc
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

4.2 Using Multipart Alternative for Low Fidelity Clients

This example shows how a client can emit a multipart message that
includes both a plain text version as well as the full iCalendar
object. Clients that do not support text/calendar will still be
capable of rendering the plain text representation.

From: foo1@example.com
To: foo2@example.com
Subject: Phone Conference
Mime-Version: 1.0
Content-Type: multipart/alternative;boundary="01BD3665.3AF0D360"

--01BD3665.3AF0D360
Content-Type: text/plain;charset=us-ascii

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Content-Transfer-Encoding: 7bit

This is an alternative representation of a TEXT/CALENDAR MIME Object
When: 7/1/1997 10:00AM PDT - 7/1/97 10:30AM PDT
Where:
Organizer: foo1@example.com
Summary: Phone Conference

--01BD3665.3AF0D360
Content-Type:text/calendar; method=REQUEST; charset=US-ASCII
Content-Transfer-Encoding: 7bit

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
ORGANIZER:mailto:foo1@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:foo1@example.com
ATTENDEE;RSVP=YES;TYPE=INDIVIDUAL:mailto:foo2@example.com
DTSTAMP:19970611T190000Z
DTSTART:19970701T170000Z
DTEND:19970701T173000Z
SUMMARY:Phone Conference
UID:calsvr.example.com-8739701987387771
SEQUENCE:0
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

--01BD3665.3AF0D360

4.3 Single Component With An ATTACH Property and Inline Attachment

This example shows how a message containing an iCalendar object
references an attached document. The reference is made using a
Content-id (CID). Thus, the iCalendar object and the document are
packaged in a multipart/related encapsulation.

From: foo1@example.com
To: foo2@example.com
Subject: Phone Conference
Mime-Version: 1.0
Content-Type: multipart/related; boundary="boundary-example-1";
type=text/calendar

--boundary-example-1

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RFC 2447 iMIP November 1998

Content-Type:text/calendar; method=REQUEST; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="event.vcs"

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
ORGANIZER:mailto:foo1@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:foo1@example.com
ATTENDEE;RSVP=YES;TYPE=INDIVIDUAL:mailto:foo2@example.com
DTSTAMP:19970611T190000Z
DTSTART:19970701T180000Z
DTEND:19970701T183000Z
SUMMARY:Phone Conference
UID:calsvr.example.com-8739701987387771
ATTACH:cid:123456789@example.com
SEQUENCE:0
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

--boundary-example-1
Content-Type: application/msword; name="FieldReport.doc"
Content-Transfer-Encoding: base64
Content-Disposition: inline; filename="FieldReport.doc"
Content-ID: <123456789@example.com>

0M8R4KGxGuEAAAAAAAAAAAAAAAAAAAAAPgADAP7/CQAGAAAAAAAAAAABAAAARAAAAAAA
AAAAEAAAQAAAAAEAAAD+////AAAAAEUAAAD/////////////////////////////////

--boundary-example-1--

4.4 Multiple Similar Components

Multiple iCalendar components of the same type can be included in the
iCalendar object when the METHOD is the same for each component.

From: foo1@example.com
To: foo2@example.com
Subject: Summer Company Holidays
Mime-Version: 1.0
Content-Type:text/calendar; method=PUBLISH; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="event.vcs"

Dawson, et. al. Standards Track [Page 10]

RFC 2447 iMIP November 1998

BEGIN:VCALENDAR
PRODID:-//ACME/DESKTOPCALENDAR//EN
METHOD:PUBLISH
VERSION:2.0
BEGIN:VEVENT
ORGANIZER:MAILTO:FOO1@EXAMPLE.COM
DTSTAMP:19970611T150000Z
DTSTART:19970701T150000Z
DTEND:19970701T230000Z
SUMMARY:Company Picnic
DESCRIPTION:Food and drink will be provided
UID:CALSVR.EXAMPLE.COM-873970198738777-1
SEQUENCE:0
STATUS:CONFIRMED
END:VEVENT
BEGIN:VEVENT
ORGANIZER:MAILTO:FOO1@EXAMPLE.COM
DTSTAMP:19970611T190000Z
DTSTART:19970715T150000Z
DTEND:19970715T230000Z
SUMMARY:Company Bowling Tournament
DESCRIPTION:We have 10 lanes reserved
UID:CALSVR.EXAMPLE.COM-873970198738777-2
SEQUENCE:0
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

4.5 Multiple Mixed Components

Different component types must be encapsulated in separate iCalendar
objects.

From: foo1@example.com
To: foo2@example.com
Subject: Phone Conference
Mime-Version: 1.0
Content-Type:multipart/mixed;boundary="--FEE3790DC7E35189CA67CE2C"

This is a multi-part message in MIME format.

----FEE3790DC7E35189CA67CE2C
Content-Type:text/calendar; method=REQUEST; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="event1.vcs"

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RFC 2447 iMIP November 1998

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
ORGANIZER:mailto:foo1@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:foo1@example.com
ATTENDEE;RSVP=YES;TYPE=INDIVIDUAL:mailto:foo2@example.com
DTSTAMP:19970611T190000Z
DTSTART:19970701T210000Z
DTEND:19970701T230000Z
SUMMARY:Phone Conference
DESCRIPTION:Discuss what happened at the last meeting
UID:calsvr.example.com-8739701987387772
SEQUENCE:0
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

----FEE3790DC7E35189CA67CE2C
Content-Type:text/calendar; method=REQUEST; charset=US-ASCII
Content-Transfer-Encoding:7bit
Content-Disposition: attachment; filename="todo1.vcs"

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VTODO
DUE:19970701T090000-0700
ORGANIZER:mailto:foo1@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:foo1@example.com
ATTENDEE;RSVP=YES:mailto:foo2@example.com
SUMMARY:Phone Conference
DESCRIPTION:Discuss a new location for the company picnic
UID:calsvr.example.com-td-8739701987387773
SEQUENCE:0
STATUS:NEEDS ACTION
END:VEVENT
END:VCALENDAR

----FEE3790DC7E35189CA67CE2C

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4.6 Detailed Components With An ATTACH Property

This example shows the format of a message containing a group meeting
between three individuals. The multipart/related encapsulation is
used because the iCalendar object contains an ATTACH property that
uses a CID to reference the attachment.

From: foo1@example.com
MIME-Version: 1.0
To: foo2@example.com,foo3@example.com
Subject: REQUEST - Phone Conference
Content-Type:multipart/related;boundary="--FEE3790DC7E35189CA67CE2C"

----FEE3790DC7E35189CA67CE2C
Content-Type: multipart/alternative;
boundary="--00FEE3790DC7E35189CA67CE2C00"

----00FEE3790DC7E35189CA67CE2C00
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

When: 7/1/1997 10:00PM PDT- 7/1/97 10:30 PM PDT
Where:
Organizer: foo1@example.com
Summary: Let's discuss the attached document

----00FEE3790DC7E35189CA67CE2C00

Content-Type:text/calendar; method=REQUEST; charset=US-ASCII;
Component=vevent
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="event.vcs"

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
PROFILE:REQUEST
PROFILE-VERSION:1.0
VERSION:2.0
BEGIN:VEVENT
ORGANIZER:foo1@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:foo1@example.com
ATTENDEE;RSVP=YES;TYPE=INDIVIDUAL:mailto:foo2@example.com
ATTENDEE;RSVP=YES;TYPE=INDIVIDUAL:mailto:foo3@example.com
DTSTAMP:19970611T190000Z
DTSTART:19970621T170000Z
DTEND:199706211T173000Z
SUMMARY:Let's discuss the attached document
UID:calsvr.example.com-873970198738777-8aa

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RFC 2447 iMIP November 1998

ATTACH:cid:calsvr.example.com-12345aaa
SEQUENCE:0
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

----00FEE3790DC7E35189CA67CE2C00

----FEE3790DC7E35189CA67CE2C
Content-Type: application/msword; name="FieldReport.doc"
Content-Transfer-Encoding: base64
Content-Disposition: inline; filename="FieldReport.doc"
Content-ID: <calsvr.example.com-12345aaa>

R0lGODdhTAQZAJEAAFVVVd3d3e4AAP///ywAAAAATAQZAAAC/5yPOSLhD6OctNqLs94XqAG
4kiW5omm6sq27gvH8kzX9o1y+s73/g8MCofEovGITCoxKMbyCR16cNSq9YrNarfcrvdriIH
5LL5jE6rxc3G+v2cguf0uv2Oz+v38L7/DxgoOKjURnjIIbe3yNjo+AgZWYVIWWl5iZnJY6J.

----FEE3790DC7E35189CA67CE2C

5 Recommended Practices

This section outlines a series of recommended practices when using a
messaging transport to exchange iCalendar objects.

5.1 Use of Content and Message IDs

The [iCAL] specification makes frequent use of the URI for data types
in properties such as "DESCRIPTION", "ATTACH", "CONTACT" and others.
Two forms of URIs are Message ID (MID) and Content ID (CID). These
are defined in RFC-2111">[RFC-2111]. Although RFC-2111">[RFC-2111] allows referencing
messages or MIME body parts in other MIME entities or stores, it is
strongly recommended that iMIP implementations include all referenced
messages and body parts in a single MIME entity. Simply put, if an
iCalendar object contains CID or MID references to other messages or
body parts, implementations should ensure that these messages and/or
body parts are transmitted with the iCalendar object. If they are not
there is no guarantee that the receiving "CU" will have the access or
the authorization to view those objects.

Dawson, et. al. Standards Track [Page 14]

RFC 2447 iMIP November 1998

6 Bibliography

[CHST] Character Sets, ftp://ftp.isi.edu/in-
notes/iana/assignments/character-sets

[iCAL] Dawson, F. and D. Stenerson, "Internet Calendaring and
Scheduling Core Object Specification - iCalendar", RFC
2445, November 1998.

[iTIP] Silverberg, S., Mansour, S., Dawson, F. and R. Hopson,
"iCalendar Transport-Independent Interoperability Protocol
(iTIP): Scheduling Events, Busy Time, To-dos and Journal
Entries", RFC 2446, November 1998.

RFC-822">[RFC-822] Crocker, D., "Standard for the Format of ARPA Internet
Text Messages", STD 11, RFC 822, August 1982.

RFC-1847">[RFC-1847] Galvin, J., Murphy, S., Crocker, S. and N. Freed,
"Security Multiparts for MIME: Multipart/Signed and
Multipart/Encrypted", RFC 1847, October 1995.

RFC-2045">[RFC-2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) - Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.

RFC-2046">[RFC-2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) - Part Two: Media Types", RFC 2046,
November 1996.

RFC-2047">[RFC-2047] Moore, K., "Multipurpose Internet Mail Extensions (MIME) -
Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996.

RFC-2048">[RFC-2048] Freed, N., Klensin, J. and J. Postel, "Multipurpose
Internet Mail Extensions (MIME) - Part Four: Registration
Procedures", RFC 2048, January 1997.

RFC-2111">[RFC-2111] Levinson, E., "Content-ID and Message-ID Uniform Resource
Locators", RFC 2111, March 1997.

RFC-2119">[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

Dawson, et. al. Standards Track [Page 15]

RFC 2447 iMIP November 1998

7 Authors' Addresses

The following address information is provided in a vCard v3.0,
Electronic Business Card, format.

BEGIN:VCARD
VERSION:3.0
N:Dawson;Frank
FN:Frank Dawson
ORG:Lotus Development Corporation
ADR;TYPE=WORK,POSTAL,PARCEL:;;6544 Battleford
Drive;Raleigh;NC;27613-3502;USA
TEL;TYPE=WORK,MSG:+1-919-676-9515
TEL;TYPE=WORK,FAX:+1-919-676-9564
EMAIL;TYPE=INTERNET:fdawson@earthlink.net
URL:http://home.earthlink.net/~fdawson
END:VCARD

BEGIN:VCARD
VERSION:3.0
N:Mansour;Steve
FN:Steve Mansour
ORG:Netscape Communications Corporation
ADR;TYPE=WORK,POSTAL,PARCEL:;;501 East Middlefield Road;Mountain
View;CA;94043;USA
TEL;TYPE=WORK,MSG:+1-650-937-2378
TEL;TYPE=WORK,FAX:+1-650-937-2103
EMAIL;TYPE=INTERNET:sman@netscape.com
END:VCARD

BEGIN:VCARD
VERSION:3.0
N:Silverberg;Steve
FN:Steve Silverberg
ORG:Microsoft Corporation
ADR;TYPE=WORK,POSTAL,PARCEL:;;One Microsoft Way;
Redmond;WA;98052-6399;USA
TEL;TYPE=WORK,MSG:+1-425-936-9277
TEL;TYPE=WORK,FAX:+1-425-936-8019
EMAIL;TYPE=INTERNET:stevesil@Microsoft.com
END:VCARD

Dawson, et. al. Standards Track [Page 16]

RFC 2447 iMIP November 1998

The iCalendar Object is a result of the work of the Internet
Engineering Task Force Calendaring and scheduling Working Group. The
chairmen of that working group are:

BEGIN:VCARD
VERSION:3.0
N:Ganguly;Anik
FN:Anik Ganguly
ORG:Open Text Inc.
ADR;TYPE=WORK,POSTAL,PARCEL:;Suite 101;38777 West Six Mile Road;
Livonia;MI;48152;USA
TEL;TYPE=WORK,MSG:+1-734-542-5955
EMAIL;TYPE=INTERNET:ganguly@acm.org
END:VCARD

BEGIN:VCARD
VERSION:3.0
N:Moskowitz;Robert
FN:Robert Moskowitz
EMAIL;TYPE=INTERNET:rgm-ietf@htt-consult.com
END:VCARD

Dawson, et. al. Standards Track [Page 17]

RFC 2447 iMIP November 1998

8. Full Copyright Statement

This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, 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 organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards 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.

Dawson, et. al. Standards Track [Page 18]