WDIFF

draft-ietf-lemonade-profile-00.txt --> draft-ietf-lemonade-profile-01.txt

Lemonade
Internet Draft: Lemonade Profile S. H. Maes
Document: draft-ietf-lemonade-profile-00.txt draft-ietf-lemonade-profile-01.txt A. Melnikov
Expires: January August 2005 February 2005 July 2004

Lemonade Profile

Status of this Memo

This document is an Internet-Draft and is subject to all provisions
of Section 10 of RFC2026. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with
RFC 3668.

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.

Abstract

This document describes the Lemonade profile to allow clients to
submit new email messages incorporating content which resides on
locations external to the client ("forward without download") and to
optimize e-mail exchanges between clients and servers in a mobile
environment. download").

The Lemonade profile relies upon extensions to other protocols;
specifically URLAUTH, CATENATE, Lemonade Command Extensions in the
IMAP protocol [RFC 3501] and BURL in the SUBMIT protocol [RFC 2476].

It also provides optimization in a mobile setting, aimed at
delivering extended functionality for mobile devices with limited
resources by relying on Lemonade Server to Client Notifications to
support to push crucial changes actively to a client, rather then
requiring the client to initiate contact to ask for state changes.

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In addition, the Lemonade profile contains Lemonade Command
extensions for email filter management, message delivery, maintaining
up-to-date personal information and quick reconnect. reconnect and media conversion.

Conventions used in this document

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In examples, "C:" "M:", "I:" and "S:" indicate lines sent by the client
messaging user agent, IMAP e-mail server and submit server
respectively.

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 [RFC2119].

Table of Contents

Status of this Memo...............................................1
Abstract..........................................................1
Conventions used in this document.................................2 document.................................1
Table of Contents.................................................2
1. Introduction...................................................3 Introduction...................................................2
2. The Lemonade Pull Model........................................3 Forward without download.......................................3
2.1. Motivations...............................................3
2.2. Message Sending Overview..................................3
2.3. Traditional Strategy......................................4
2.4. Forward without download..................................4 Step by step description..................................4
2.5. Additional Considerations.................................6 Considerations.................................8
2.6. The fcc problem...........................................6 problem...........................................8
3. Mobile Optimization............................................7 Media Conversion...............................................9
3.1. Introduction..............................................7 Introduction..............................................9
3.2. Motivation................................................7 Static media conversion...................................9
3.3. The Poll Model vs. the Push Model.........................7 Conversion of streamed media..............................9
3.4. Synchronization Techniques................................8
3.4.1. State-Comparison-Based Synchronization...............9
3.4.2. Event-based Synchronization.........................10
3.5. The Server-Side Filtering in Lemonade Profile............11
3.6. Lemonade Command Extensions..............................11
3.7. Fast Reconnect...........................................12
3.8. HTTP Binding.............................................12
3.9. Revisions to IMAPv4 Rev1 Behavior........................12 Quick Reconnect scheme....................................9
4. Future work...................................................10
Security Considerations..........................................13
References.......................................................13
Acknowledgments..................................................15 Considerations..........................................10
References.......................................................10
Version History..................................................12
Acknowledgments..................................................12
Authors Addresses................................................15 Addresses................................................12
Intellectual Property Statement..................................15 Statement..................................12
Full Copyright Statement.........................................16

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1.
Introduction

Lemonade provides enhancements to Internet email to support diverse
service environments.

This document describes the lemonade profile that includes:
- The Lemonade Pull Model that describes exchanges between
Lemonade Agents to allow clients to submit new email messages
incorporating content which resides on locations external to
the client.
- Mobile optimizations that defines extensions to the IMAPv4 Rev1
protocol [RFC3501] aimed at delivering extended functionality
for mobile devices with limited resources including support to
push crucial changes actively to a client, rather then
requiring the client to initiate contact to ask for state
changes and extensions for email filter management, message
delivery, and maintaining up-to-date personal information and
quick reconnect. allow forward without download.
- Media conversion

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- Quick reconnect

The organization of this document is as follows. Section 2 describes
the Lemonade Pull Model. Section 3 Section 3 describes the Lemonade Mobile
Optimizations. Media
Conversion. Section 4 describes quick reconnect

2. The Lemonade Pull Model
Forward without download

2.1.
Motivations

The advent of client/server email using the [RFC3501] and [RFC2821]
protocols has changed what formerly were local disk operations to
become excessive and repetitive network data transmissions. This is
an onerous burden for clients operating over low-bandwidth and/or
high-latency links.

The Lemonade Pull Model makes use of the [BURL] SUBMIT extension to
enable access to external sources during the submission of a message.
In combination with the IMAP [URLAUTH] extension, inclusion of
message parts or even entire messages from the IMAP mail store is
possible with a minimal trust relationship between the IMAP and
SUBMIT servers.

Pull has the distinct advantage of maintaining one submission
protocol, and thus avoids the risk of having multiple parallel and
possible divergent mechanisms for submission. Furthermore, by
keeping the details of message submission in the SUBMIT server, the
Lemonade Pull Model can work with other message retrieval protocols
such as POP, NNTP, or whatever else may be designed in the future.

2.2.
Message Sending Overview

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The act of sending an email message is best thought of as involving
multiple steps: initiation of a new draft, draft editing, message
assembly, and message submission.

Initiation of a new draft and draft editing takes place on the MUA.
Frequently, users choose to save more complex and/or time-consuming
messages on an [RFC3501] server (via the APPEND command with the
\Draft flag) for later recall by the MUA and resumption of the
editing process.

Message assembly is the process of producing a complete message from
the final revision of the draft and external sources. At assembly
time, external data is retrieved and inserted in the message.

Message submission is the process of inserting the assembled message
into the [RFC2821] infrastructure, typically using the [RFC2476]
protocol.

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2.3.
Traditional Strategy

Traditionally, messages are initiated, edited, and assembled entirely
within an MUA, although drafts may be saved to an [RFC3501] server
and later retrieved from the server. The completed text is then
transmitted to an MSA for delivery.

There is often no clear boundary between the editing and assembly
process. If a message is forwarded, its content is often retrieved
immediately and inserted into the message text. Similarly, once
external content is inserted or attached, the content is usually
retrieved immediately and made part of the draft.

As a consequence, each save of a draft and subsequent retrieve of the
draft transmits that entire (possibly large) content, as does message
submission.

In the past, this was not much of a problem, because drafts, external
data, and the message submission mechanism were typically located on
the same system as the MUA. The most common problem was running out
of disk quota.

2.4. Forward without download
Step by step description

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The model distinguishes between a Messaging User Agent (MUA), an
IMAPv4Rev1 Server ([RFC3501]) and a submit server ([RFC2476]), as
illustrated in Figure 1.

+--------------------+ +--------------+
| | <------------ | |
| MUA (M) | | IMAPv4 Rev1 |

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| | | Server |
| | ------------> | (Server S1) I) |
+--------------------+ +--------------+
^ | ^ |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | v
| | +--------------+
| |------------------------->| |
| | Submit |
|-----------------------------| Server |
| (Server S2) S) |
+--------------+
Figure 1: Lemonade Pull Model

The Lemonade Pull Model allows a Messaging User Agent to compose and
forward an e-mail combining fragments that are located in an IMAP
server, without having to download these fragments to the server.

In the [BURL]/[CATENATE] variant of the pull strategy, messages are
initiated
initially composed and edited within an MUA. The [CATENATE]
extension to [RFC3501] is then used to upload the message to the IMAP
server and assemble it, and finally a [URLAUTH] format URL is given
to a [RFC2476] server with the [BURL] extension for submission.

The flow involved to support such a use case consists of:
M: {to S1 I -- Optional} The client uses connectects to the IMAP server
and IMAP Fetch of body structures and UIDs (See [RFC3501])

Example:
M: A0051 FETCH 161 (UID BODYSTRUCTURE)
I: * 161 FETCH (UID 25627 BODYSTRUCTURE (("TEXT" "PLAIN"
("CHARSET" "US-ASCII") NIL
NIL "7BIT" 1152 23)("TEXT" "PLAIN" ("CHARSET" "US-ASCII"
"NAME"
"cc.diff")
"<960723163407.20117h@washington.example.net>" "Compiler
diff"

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"BASE64" 4554 73) "MIXED"))
I: A0051 OK completed

M: {to S1} I} The client invokes CATENATE (See [CATENATE] for details
of the semantics and steps � this allows the MUA to create messages
on the IMAP using new data combined with body structure already
present on the IMAP server.
S1: {to M}

<<Editor�s note: Draft editing/catenation is omitted for now>>

M: A0052 CATENATE Sent FLAGS (\Seen $MDNSent) TEXT {738}
I: + Ready for literal data
M: Return-Path: <bar@example.org>
M: Received: from [127.0.0.2]
M: by rufus.example.org via TCP (internal) with
ESMTPA;
M: Thu, 11 Nov 2004 16:57:07 +0000
M: Message-ID: <419399E1.6000505@example.org>
M: Date: Thu, 12 Nov 2004 16:57:05 +0000
M: From: Bob Ar <bar@example.org>
M: X-Accept-Language: en-us, en
M: MIME-Version: 1.0
M: To: foo@example.net
M: Subject: About our holiday trip
M: Content-Type: multipart/mixed;
M: boundary="------------030308070208000400050907"
M:
M: --------------030308070208000400050907
M: Content-Type: text/plain; charset=us-ascii; format=flowed
M: Content-Transfer-Encoding: 7bit
M:
M: Our travel agent has sent the updated schedule.
M:
M: Cheers,
M: Bob
M: --------------030308070208000400050907
M: URL "imap://imap.example.org/INBOX;UIDVALIDITY=385759045/;
UID=25627;Section=1.2" TEXT {44}
I: + Ready for literal data
M: --------------030308070208000400050907--
M:
I: A0052 OK (See [CATENATE]). [APPENDUID 387899045 45] CATENATE Completed
M: A0053 UID STORE XXX +FLAGS.SILENT ($Forwarded)
I: A0053 OK STORE completed

<< Editor�s note: Recommend UIDPLUS extension � especially useful
when appending messages to a non-selected mailbox>>

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M: {to S1} I} The client uses GENURLAUTH command to request and
URLAUTH URL (See [URLAUTH]).
S1:
I: {to M} The IMAP server returns URLAUTH URL suitable for later
retrieval with URLFETCH (See [URLAUTH] for details of the semantics
and steps).

M: A0054 GENURLAUTH
"imap://bob.ar@example.org/Sent;UIDVALIDITY=387899045/;uid=45/;urla
uth=submit+bar" INTERNAL
I: * GENURLAUTH
"imap://bob.ar@example.org/Sent;UIDVALIDITY=387899045/;uid=45/;urla
uth=submit+bar:internal:91354a473744909de610943775f92038"
I: A0054 OK GENURLAUTH completed

M: {to S2} S} The client connects to the submission server and starts
a new mail transaction. It uses BURL to let the submit server fetch
the content of the message from the IMAP server (See [BURL] for
details of the semantics and steps � this allows the MUA to
authorize the submit server to access the message composed as a
result of the CATENATE step).

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S2:

M: EHLO potter.example.org
S: 250-owlry.example.com
S: 250-8BITMIME
S: 250-BURL imap
S: 250-AUTH PLAIN
S: 250-DSN
S: 250 ENHANCEDSTATUSCODES
M: AUTH PLAIN aGFycnkAaGFycnkAYWNjaW8=
S: 235 2.7.0 PLAIN authentication successful.
M: MAIL FROM:<bob.ar@example.org>
S: 250 2.5.0 Address Ok.
M: RCPT TO:<ron@gryffindor.example.com>
S: 250 2.1.5 ron@gryffindor.example.com OK.
M: BURL
imap://bob.ar@example.org/Sent;UIDVALIDITY=387899045/;uid=45/;urlau
th=submit+bar:internal:91354a473744909de610943775f92038 LAST

S: {to S1} I} The submission server uses URLFETCH to fetch the message
to be sent (See [URLAUTH] for details of the semantics and steps.
The so-called "pawn-ticket" authorization mechanism uses a URI
which contains its own authorization credentials.).
S1:
I: {to S2} S} Provides the message composed as a result of the
CATENATE step).

Submission server opens IMAP connection to the IMAP server:

I: * OK [CAPABILITY IMAP4REV1 URLAUTH] example.com IMAP
server ready

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S: a001 LOGIN submitserver secret
I: a001 OK submitserver logged in
S: a002 URLFETCH "
imap://bob.ar@example.org/Sent;UIDVALIDITY=387899045/;uid=45/;urlau
th=submit+bar:internal:91354a473744909de610943775f92038"
I: * URLFETCH "
imap://bob.ar@example.org/Sent;UIDVALIDITY=387899045/;uid=45/;urlau
th=submit+bar:internal:91354a473744909de610943775f92038" {15065}
...message body follows...
S: a002 OK URLFETCH completed

<< Editor�s note: The submission server may LOGOUT>>

S2: {to M} OK (2XX)

Submission server returns OK to the MUA:
S: 250 2.5.0 Ok.

The messaging user agent, mail server and submit server MUST support
IMAPv4 Rev1 [RFC3501], CATENATE [CATENATE] and URLAUTH [URLAUTH].

2.5.
Additional Considerations

The so-called "pawn-ticket" authorization mechanism uses a URI which
contains its own authorization credentials using [URLAUTH]. The
advantage of this mechanism is that the submit [RFC2476] server can
not access any data on the [RFC3501] server without a "pawn-ticket"
created by the client. The "pawn-ticket" grants acces only to the
specific data that the submit [RFC2476] server is authorized to
access, can be revoked by the client, and can have a time-limited
validity.

2.6.
The fcc problem

The "fcc problem" refers to a frequent need to deliver a copy of the
message to a "file carbon copy" recipient. By far, the most common
case of fcc is a client leaving a copy of outgoing mail in a "sent
messages" or "outbox" mailbox.

In the traditional strategy, the MUA duplicates the effort spent in
transmitting to the MSA by writing the message to the fcc destination
in a separate step. This may be a write to a local disk file or an
APPEND to a mailbox on an IMAP server. The latter is one of the
"excessive and repetitive network data transmissions" which
represents the "problem" aspect of the "fcc problem".

The [CATENATE] extension to [RFC3501] addresses the fcc problem. It
requires making several simplifying assumptions:

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(1a) there is one, and only one, fcc destination on a single
server
(2a) the server which holds the fcc is the same as the server
which stages the outgoing message for submission
(3a) it is desired that the fcc be a copy of the complete message
text with all external data inserted in the message

<<[POSTADDRESS]

<< Editor�s note: [POSTADDRESS] can be used to address issues (1a)
and (2a). To be done later>>

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3. Mobile Optimization
Media Conversion

3.1.
Introduction

The Lemonade profile provides optimizations

<<Editor�s note: To be done when agreed by WG>>

3.2.
Static media conversion

<<Editor�s note: To be done when agreed by WG>>

3.3.
Conversion of streamed media

<<Editor�s note: To be done when agreed by WG>>

3.4.
Quick Reconnect scheme

Mobile operators usually charge users for the exchanges between
a time their mobile
client and e-mail server by specifying additional
enhancements gets connected to the Internet and/or for optimization in a mobile setting. Thus, the client
devices in this profile are assumed to be mobile with limited
resources. This profile takes into account the limited resources of
mobile devices, as well as extra functionality desired.

Figure 2 illustrates the exchanges specified by the mobile
optimizations of the Lemonade Profile.

The e-mail server MAY comply with the Lemonade Pull Model described
in section 2.

+--------------------+ +--------------+
| Mobile | <------------ | |
| Lemonade | | Lemonade |
| E-mail Client | |E-mail Server |
| | ------------> | |
+--------------------+ +--------------+
Figure 2: Lemonade CS Profile Model

A disconnected mobile client should behave like a good disconnected
client [IMAP-DISC].

Additional requirements for optimization for Mobile access are
discussed in section 3.6.

3.2. Motivation

Today, most of the existing email clients have a polling model, where
the end user is notified of changes to an email account only after
his/her email client asks the server, called polling. How long it
takes a client to learn of a change on the server is thus dependent
on how often the client polls for changes. Many clients can poll at
high rates so that the client can quickly learn of changes and
reflect them on the client display to achieve a quasi-real time.

The mobile optimization of the Lemonade profile can support both Poll
and Push Models.

3.3. The Poll Model vs. the Push Model

Today, most of the existing email clients implement a polling model,
where the end user is notified of changes to an email account only
after the email client polls the server for changes. How long it

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takes a client to learn of a change on the server is thus dependent
on how often the client polls for changes. Many clients can poll at
high rates so that the client can quickly learn of changes and
reflect them on the client display to achieve a quasi-real time
synchronization experience for the end user. The periodic poll model
is used on conventional email clients. Because the client must
continuously poll the server for changes, the bandwidth requirements
can be quite high and the connection quality must be good in order to
provide a quasi-real time experience to the user. This also
generates additional load on the IMAP server. The periodic poll
model is illustrated in Figure 2.

+--------------------+ Poll +--------------+
| | <------------ | |
| Mail Server | | Email Client |
| | ------------> | |
+--------------------+ Response +--------------+

Figure 3: Periodic Poll Model

Another way to achieve synchronization is for the email server to
initiate a session with the client when a crucial change to an email
occurs, which is the push model. When important events happen to a
user�s email account, the server informs the client device about the
event, and then the client can respond to that event as necessary.
In this case, the client device does not need to periodically poll
the mail server, so the push model is particularly effective in the
mobile computing environment when the cost of constant polling is
high. [NOTIFICATIONS] defines the semantics for pushing events to a
client. The push model is seen in Figure 2.

Event +----------------+ Push +--------------+
--------> | Mail Server | ---------> | Email Client |
+----------------+ +--------------+

Figure 4: Push Model

3.4. Synchronization Techniques

After a client receives a notification that informs it that changes
have occurred to a mailbox, it needs to employ a synchronization
technique to reflect the server side changes onto the client device.
There are many techniques for determining what the changes between a
server and client are. In this section, two techniques are presented
that aim to keep a client device in sync with a given email account,
meaning that the set of messages on the client device is the same as
that in the given email account.

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3.4.1. State-Comparison-Based Synchronization

IMAPv4Rev1 clients use a state-comparison-based synchronization
technique to be in sync with an email account. This technique
requires the client to ask the server for information regarding all
the folders and all the messages in each folder stored on the server.
The client must then compute the difference between the server state
and the client device state, and make all necessary changes so that
the client device state matches the server state. An example of the
interaction between the client and server in the IMAPv4Rev1 protocol
for performing a state-comparison-based sync follows. This is
described in more details in [IMAP-DISC].

First, the client must retrieve the folders from the server. The
client should issue LIST to figure out which folders has to be
retrieved. It than uses LSUB to determine which folders are
subscribed. For example:

C: A002 LIST "" "%"
S: * LIST (\NoInferiors) "/" "Drafts"
S: * LIST () "/" "Friends"
S: * LIST (\NoInferiors) "/" "INBOX"
S: A002 OK completed
C: A003 LSUB "" "*"
S: * LSUB () "/" "Drafts"
S: * LSUB () "/" "Friends"
S: * LSUB () "/" "INBOX"
S: A003 OK LSUB completed

Note, that the client should not use LIST "" *, as it might cause too
much data to be returned. This is discussed in [RFC2683] in more
details.

The client must compare its folders with the responses of the command
above. If it does not have a folder, it must create that folder on
the client device. If there is a folder on the device that is not in
any of these responses, then the client must delete that folder. In
order to avoid loosing changes performed on the client, the client
should apply its changes first. In case when the client has changes
to a folder that was deleted on the server, it should ask the user
whether the changes should be uploaded to a different mailbox or be
discarded (or be configured to automatically do one of the two).

Next, the client needs to make sure that the emails in each of its
folders match the server. It performs a SELECT and then a FETCH
command for each folder. A sample of a SELECT and FETCH command for
the inbox is as follows:
C: A003 SELECT �INBOX"
S: * 60 EXISTS

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S: ... more untagged responses with information about the folder
S: A003 OK SELECT completed
C: A004 FETCH 1:* (FLAGS UID)
S: * 1 FETCH (FLAGS (\Answered) UID 120)
S: * 2 FETCH (FLAGS (\Seen) UID 121)
S: ... flags for messages with message sequence numbers 3-59
S: * 60 FETCH (FLAGS () UID 250)
S: A004 OK FETCH completed

The client must go through the full list of email messages in each
folder. It must download an email message from this list if it is
not already on the client. Any changes to the mutable flags a
message must be reflected on the server using IMAP STORE command.
Also, the client should remove any emails on the client device not in
this list. After performing these operations, the client is in sync
with the server.

<<Need to check if this matches [IMAP-DISC]>>

3.4.2. Event-based Synchronization

Another technique is event-based synchronization. Event-based
synchronization is used to keep the client device in sync with the
server. This method requires that the client has been fully
synchronized with the server at some earlier point. In the
IMAPv4Rev1 protocol, the client must perform a state-comparison-based
sync when it selects a folder, but then it can use event-based
synchronization to keep itself in sync after that. Although event-
based synchronization cannot totally replace state-comparison-based
synchronization, it is a faster alternative for the client to
maintain synchrony when the server is capable of change tracking for
a client.

In event-based synchronization, the server keeps track of what
changes have occurred to the email account that are not yet reflected
on the client device. Such a change is called an event. When the
client finishes processing all events since the last time it was in
sync with the server, it is again in sync with the server. Event-
based synchronization is particularly effective when the server can
push events to the client for immediate processing. In this case,
there are likely to be only a small number of events the client needs
to process at one time.

Also, when a Lemonade client drops a connection or accidentally
disconnects the server can retain the session and cache all events
during the time the client is disconnected. When the client
reconnects it does not need to perform a state-comparison-based
synchronization all over again, and the server sends the list of
pending events to the client..

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Lemonade Mobile Clients and Servers MUST support Lemonade Server to
Client Notifications as described in [NOTIFICATIONS].

3.5. The Server-Side Filtering in Lemonade Profile

The Lemonade server MUST support Server-side filtering as described
in [NOTIFICATIONS].

3.6. Lemonade Command Extensions

The Lemonade server MUST support the rich set of extra functionality
over the IMAP server to support extra features for a mobile client
described as Lemonade Command Extensions in [EXTENSIONS]. These
include:

[1] Compression � Lemonade CS Profile allows for compression of
responses to a command. Preliminary testing results shows
significant performance results when the response to FETCH FLAGS or
header information are compressed. Details are found in
[EXTENSIONS].

[2] Sending emails - The Lemonade server can be used to send email,
thus eliminating the need for the Lemonade client to connect to a
separate SMTP server. When interfacing with a server that supports
LEMONADEDELIVER as discovered via CAPABILITY commands as described
in [Extensions], this is the mechanism that SHOULD be used.
Otherwise, the client is expected to implement the Lemonade Pull
Model described in section 2.

[3] Support for unstable mobile connections � After a client drops
a connection, the Lemonade server can temporarily maintain the
session for the mobile client. During this time, the server caches
any events concerning the mobile repository while the client is
disconnected, which it can then send to the client upon
reconnection. This is described in more details in Section 3.7 of
this document.

[4] Longer periods of inactivity tolerated - A Lemonade server
should wait at least 24 hours before logging out an inactive mobile
client and ending its session. <<This may lead to Deny of Service.
To be investigated.>>

[5] Attachments forward/reply behavior - When forwarding/replying
to a message from the Lemonade client, the end user may choose to
reattach the original's message attachments by just specifying the
UID of the original message and specifiers for the required
bodyparts. The client need not download the attachments of the

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original message itself. This is an expected server behavior. It
MAY also be implemented following the Lemonade Pull Model.

[6] Attachments conversion - The Lemonade server can convert
attachments to other formats to be viewed on a mobile device. This
is an expected server behavior.

[7] PIM - The protocol also provides support for updating personal
information on a client device, even when these changes are
initiated from another client (i.e. a personal assistant connects
to an end user�s account from a desktop and changes contact
information.) These additional uses are especially useful for
mobile devices, where end users need up-to-date information on the
fly. <<This requires additional work to store calendaring and
address book informations.>>

3.7. Fast Reconnect

Mobile operators usually charge users for the time their mobile
client gets connected to the Internet and/or for the amount of
information sent/received. Thus the amount of
information sent/received. Thus a mobile client should minimize time
it stays connected to its mail server, which suggests that it should
disconnect and reconnect frequently.

Also, it is possible that the mobile client unexpectedly leaves area
of connectivity, which will require that the client reconnects when
connectivity returns.

<< Editor�s note: Discussion about voluntarily versa non-voluntarily
disconnects might go here>>

IMAP can be verbose. Usually, in order to synchronize a client with a
server after a disconnect, the client needs to issue at least the
following commands: LOGIN/AUTHENTICATE, SELECT and several FETCH
commands (see [IMAP-DISC] for more details).

Thus, there is a desire to have a quick reconnect facility in IMAP,
which will give a mobile client ability to resume a previously
abandoned session, without the need to perform the full
synchronization sequence as described above.

<<Note, we need an example here with and without the extension. To Be
Done.>>

3.8. HTTP Binding

For mobile clients, the Lemonade Profile exchanges MAY be transported
on HTTP as described in [HTTPBINDINGS].

3.9. Revisions to IMAPv4 Rev1 Behavior

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<< Editor�s note: Example is as per reconnect-02, syntax is subject
to change>>

S: * OK [CAPABILITY IMAP4REV1 STARTTLS AUTH=LOGIN CONDSTORE
X-DRAFT-W02-RECONNECT] imap.example.com IMAP4rev1 2001.315rh
at Thu, 15 Jul 2004

A 11:47:49 -0400 (EDT)
C: b0002 authenticate login (SID P1234567890 56789
20010715194045000
41,43:211,214:541)
S: + VXNlciBOYW1lAA==
C: dGVzdDg=
S: + UGFzc3dvcmQA
C: dGVzdDg=
S: * FOLDER INBOX
S: * 464 EXISTS
S: * 3 RECENT
S: * OK [UIDVALIDITY 3857529045] UIDVALIDITY
S: * OK [UIDNEXT 550] Predicted next UID
S: * OK [HIGHESTMODSEQ 20010715194045007]
S: * 1 FETCH (UID 1 FLAGS (\Seen))
S: b0002 OK [CAPABILITY IMAP4REV1 IDLE NAMESPACE MAILBOX-REFERRALS
SCAN
SORT THREAD=REFERENCES THREAD=ORDEREDSUBJECT MULTIAPPEND] User
test8 authenticated

4.
Future work

Future versions of the Lemonade server MUST responds profile are expected to all IMAPv4Rev1 commands. A
compliant Lemonade address
issues related to access of email form mobile devices, possibly
including:
- transport optimization for low or costly bandwidth and less
reliable mobile networks
- server must implement all to client notifications outside of the commands in IMAPv4
Rev1, traditional IMAP
band
- dealing with the revisions described in [NOTIFICATIONS] firewall and
[EXTENSIONS]. intermediaries
- compression
- filtering

Security Considerations

Security considerations on the Lemonade Pull Model are discussed
throughout section 2.

The mobile optimization of the Lemonade profile calls for the same
security requirements for an in-response and inband connectivity mode
as IMAP.

For the outband connectivity mode, servers should use encryption
methods for notifications if sensitive information is included in the
payload of that notification.

When an implementation of Lemonade Mobile Profile is proxy-based,
this may create new security issues. These issues are discussed in
detail in [EXTENSIONS], because the issues are dependent on the
implementation of this protocol rather than inherent to the protocol
itself.

<< Editor�s note: TBD (Reconnect, etc.)>>

References

[OMA-EN] Open Mobile Alliance Email Notification Version 1.0,

Maes Expires - August
2002. http://www.openmobilealliance.org/tech/docs/EmailNot/OMA-
Push-EMN-V1_0-20020830-C.pdf 2005 [Page 10]

<Lemonade Profile> February 2005

[IMAP-DISC] Melnikov, A. "Synchronization Operations For
Disconnected Imap4 Clients", IMAP-DISC, work in progress, draft-
melnikov-imap-disc-XX.txt

[RFC2119] Brader, S. "Keywords for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
http://www.ietf.org/rfc/rfc2119

[RFC2180] Gahrns, M. "IMAP4 Multi-Accessed Mailbox Practice", RFC
2180, July 1997.
http://www.ietf.org/rfc/rfc2180

[RFC2234] Crocker, D. and Overell, P. "Augmented BNF for Syntax
Specifications", RFC 2234, Nov 1997.
http://www.ietf.org/rfc/rfc2234

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[RFC2420] Kummert, H. "The PPP Triple-DES Encryption Protocol
(3DESE)", RFC 2420, September 1998.
http://www.ietf.org/rfc/rfc2420

[RFC2616] Fielding, R. et al. "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999.
http://www.ietf.org/rfc/rfc2616

[RFC2617] Franks, J. et al. "HTTP Authentication: Basic and Digest
Access Authentication", RFC 2617, June 1999.
http://www.ietf.org/rfc/rfc2617

[RFC2683] Leiba, B. "IMAP4 Implementation Recommendations", RFC 2683
Sep 1999.
http://www.ietf.org/rfc/rfc2683

[RFC2177] Leiba, B. "IMAP4 IDLE Command", RFC 2177, June 1997.
http://www.ietf.org/rfc/rfc2177

[RFC2818] Rescorla, E. "HTTP over TLS", RFC 2818, May 2000.
http://www.ietf.org/rfc/rfc2818

[RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001.

[RFC2822] Resnick, P. "Internet Message Format", RFC 2822, April
2001. http://www.ietf.org/rfc/rfc2822

[RFC3501] Crispin, M. "IMAP4, Internet Message Access Protocol
Version 4 rev1", RFC 3501, March 2003.
http://www.ietf.org/rfc/rfc3501

[RFC2476] Gellens, R. and Klensin, J., "Message Submission", RFC
2476, December 1998.

[CATENATE]Resnick, P., "Internet Message Access Protocol (IMAP)
CATENATE Extension", draft-ietf-lemonade-catenate-01, draft-ietf-lemonade-catenate-XX, (work in
progress), January 2004.
progress).

[BURL] Newman, C., "Message Composition", draft-newman-lemonade-
compose-00.txt draft-ietf-lemonade-
burl-xx (work in progress), June 2003. progress).

[URLAUTH] Crispin, M. and Newman, C., "Internet Message Access
Protocol (IMAP) - URLAUTH Extension", draft-crispin-imap-urlauth-
09.txt, (work in progress), July 2004.

[EXTENSIONS] Maes, S.H., Lima R., Kuang, C., Cromwell, R., Ha, V. and
Chiu, E., "Lemonade Command Extensions", draft-maes-lemonade-
command-extensions-00.txt, (work in progress), July 2004.

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<Lemonade Profile> July 2004

[NOTIFICATIONS] Maes, S.H. and Wilson C., "Lemonade Server to Client
Notifications", draft-ietf-lemonade-server-to-client-
notifications-00.txt, (work in progress), July 2004.

[HTTPBINDINGS] Maes, S.H., Lima R., Kuang, C., Cromwell, R., Ha, V.
and Chiu, E., "Lemonade HTTP Binding", draft-maes-lemonade-http-
binding-00.txt, draft-ietf-lemonade-urlauth-
XX.txt, (work in progress), July 2004. progress).

[POSTADDRESS] Melnikov, A., "IMAP4 POSTADDRESS extension", work in
progress, draft-melnikov-imap-postaddress-XX.txt

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[RECONNECT] Melnikov, A. and C. Wilson, " IMAP4 extension for quick
reconnect ", work in progress, draft-ietf-lemonade-reconnect-
XX.txt

Version History

[1] We removed the sections of the profile related to mobile e-mail
as well as discussion. This will be part of the next version of
the Lemonade profile work.
[2] We added detailed examples for the different steps included in
section 2.4.
[3] We added section 3 on media conversion
[4] We added examples on Quick reconnect schemes in section 4.
[5] We updated the security considerations
[6] We fixed references based on updates above
[7] We added a future work section
[8] We fixed the boiler plate statements on the �status of this memo�
and �Copriright�.

Acknowledgments

This document is based on the work in progress described in draft-
crispin-lemonade-pull-01.txt and draft-maes-lemonade-p-imap-03.txt.
crispin-lemonade-pull-xx.txt.

Authors Addresses

Stephane H. Maes
Oracle Corporation
500 Oracle Parkway
M/S 4op634
Redwood Shores, CA 94065
USA
Phone: +1-650-607-6296
Email: stephane.maes@oracle.com

Alexey Melnikov
Isode Limited
5 Castle Business Village
36 Station Road
Hampton, Middlesex
TW12 2BX
UK
Email: Alexey.melnikov@isode.com

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Maes Expires - January 2005 [Page 15]

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