Internet DRAFT - draft-ietf-lemonade-oma-mem-realization
draft-ietf-lemonade-oma-mem-realization
LEMONADE Working Group S. Maes
Internet-Draft Oracle
Expires: June 7, 2006 G. Parsons
Nortel
December 4, 2005
Realization of OMA Mobile Email (MEM) Architecture using Internet Mail
draft-ietf-lemonade-oma-mem-realization-00.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document specifies a realization of the architecture for the
mobile email enabler (MEM) as specified by the OMA, using Internet
Mail protocols.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. OMA MEM Requirement document . . . . . . . . . . . . . . . . . 4
2.1. OMA MEM use cases . . . . . . . . . . . . . . . . . . . . 4
2.2. OMA MEM requirements . . . . . . . . . . . . . . . . . . . 6
3. OMA MEM Architecture . . . . . . . . . . . . . . . . . . . . . 8
3.1. OMA MEM logical Architecture . . . . . . . . . . . . . . . 8
3.2. OMA MEM Deployment Issues . . . . . . . . . . . . . . . . 10
3.2.1. OMA MEM proxy . . . . . . . . . . . . . . . . . . . . 10
3.2.2. OMA MEM deployment cases . . . . . . . . . . . . . . . 11
3.3. OMA MEM Required Technical Capabilities . . . . . . . . . 11
4. IETF LEMONADE Architecture . . . . . . . . . . . . . . . . . . 12
5. Realization of OMA MEM Architecture with LEMONADE . . . . . . 14
5.1. Relationship between the OMA MEM and LEMONADE logical
architectures . . . . . . . . . . . . . . . . . . . . . . 14
5.2. LEMONADE realization of OMA MEM with non-LEMONADE
compliant servers . . . . . . . . . . . . . . . . . . . . 15
5.2.1. LEMONADE realization of OMA MEM with non-LEMONADE
enhanced IMAP servers . . . . . . . . . . . . . . . . 15
5.2.2. LEMONADE realization of OMA MEM with non-IMAP
servers . . . . . . . . . . . . . . . . . . . . . . . 16
6. Filters and server to client notifications and LEMONADE . . . 18
7. Analysis of Lemonade Technology Support of OMA MEM enabler . . 20
8. Security considerations . . . . . . . . . . . . . . . . . . . 28
9. IANA considerations . . . . . . . . . . . . . . . . . . . . . 29
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 30
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32
Intellectual Property and Copyright Statements . . . . . . . . . . 33
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1. Introduction
This document describes a realization of OMA mobile email enabler
(MEM) using Internet Mail protocols defined by the IETF. Many of
these protocols have been enhanced by the LEMONADE work group for use
in the mobile environment and are summarized in the LEMONADE profile
[4]. This document shows how the requirements captured in OMA MEM
Requirement document [3] and mechanisms of the OMA MEM Architecture
[2] are satisfied.
This document contains the current view of the work. It refers to
stable specifications and work in progress. As the work progress, it
is expected that this document will evolve and be updated
accordingly.
<Editor's note: As a result some of the statements about some
specification may not yet supported by the references. When it is
the case, these specifications are expected to be be updated.>
<Editor's note: Caveat to be removed when work stabilizes.>
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2. OMA MEM Requirement document
The OMA MEM activity has collected a set of use cases and derived
requirements for a mobile email enabler (MEM). the resulting work is
summarized in OMA MEM Requirement document [3]. Some requirements
relates to email protocols, some involve other OMA technologies
outside the scope of IETF and some relate to implementations and
normative interoperability statements for clients and servers.
In the OMA MEM RD, Mobile email is scoped as an email enabler (i.e.
an OMA specification) optimized to support email usage in mobile
devices and wireless networks. The RD focuses on requirements for
the enabler specifications rather than for particular implementations
of those. The RD also does not design the solution.
So, mobile email is defined as the set of enabling technologies that
facilitate end-to-end application level interoperable email
transactions (e.g. submission, retrieval, notification etc) to and
from mobile devices. It targets both consumer and corporate mobile
e-mail. The focus of the OMA MEM enabler is between the client and
the server; not beyond. Interworking / interoperability among email
clients is ensured by ensuring interworking with the internet email
[8] as defined by IETF.
2.1. OMA MEM use cases
OMA RDs do not expect an exhaustive list of use cases. The one
covered in the OMA MEM Requirement document [3] include:
o Receiving an Email on the go. Some highlights:
* This use case describes a situation where new e-mail arrives in
e-mail servers
* It is received on mobile client quasi-instantaneously based on
settings preferences (whole e-mail or portions of e-mail;
adapted or not)
* The use case targets enterprise and Non-enterprise users
>
o Receiving a email server event on the go. Some highlights:
* The use case describes a situation where email events are
received from the server
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o Viewing email attachments on the go. Some highlights:
* This use case describes a situation involving attachment
adaptation and transcoding (known by server or requested by
client)
* It also discusses viewing the attachment (in whole or portion
by portion)
o Sending emails on the go. Some highlights:
* This use case describes a situation where the user sends an
e-mail from teh correct SMTP server
* It also discusses offline and intermittent connectivity
o Filtering rule changes while mobile. Some highlights:
* This use case describes a situation where the user dynamically
changes a filter (e.g. adds a sender from who notifications /
new e-mails should be received)
o Data synchronization between clients. Some highlights:
* This use case analyzes a situation of 3-way pair wise
synchronization (e.g. Phone, laptop and server)
o Email with Attachment. Some highlights:
* This use cases provides details about attachments manipulation
including:
+ Selectively downloading part or all of attachments if not
yet downloaded
+ Downloading more
o Forwarding Email without Downloading Attachments. Some
highlights:
* This case discusses forwarding without download with server-
side re-composition including edits
* It includes selection of what attachment to forward
o Configuring additional email accounts to be accessed. Some
highlights:
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* This case discusses supporting multiple e-mail accounts
possibly from different e-mail service providers.
o Replying to messages that are retrieved from different accounts.
Some highlights:
* This case discusses determining what account / server to use to
send e-mail
o Client Email Events. Some highlights:
* This use case describes a situation where e-mail client events
are reflected to the server
* It also discusses offline and intermittent connectivity
o Filtering Rules. Some highlights:
* It discusses filtering rules on emails and events.
o Replying or Forwarding to Emails 'On the Go'. Some highlights:
* This use cases describes how the user can edit text and
attachments
* It includes editing any email portion including addresses
* It considers sending to teh server only the edit differences
o Configuring Auto-Reply Message. Some highlights:
* This use case describes setting auto-reply for accounts while
mobile.
2.2. OMA MEM requirements
The OMA MEM Requirement document [3] contains requirements about:
o High-Level Functional Requirements
o Security Requirements
o Charging Requirements
o Administration and Configuration Requirements
o Usability Requirements
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o Interoperability Requirements
o Privacy Requirements
o Overall System Requirements
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3. OMA MEM Architecture
This section gives a brief introduction to the OMA MEM Architecture.
3.1. OMA MEM logical Architecture
The OMA MEM activity has derived a logical architecture from the
requirements and use cases described in [3]. It is represented in
Figure 1, where arrows indicate content flows.
__________
| Other |
----| Mobile |<---
| | Enablers | |
| |__________| |
|ME-4 |ME-3
_v____ ___v____ ________
| | | | | |
| MEM |ME-1 | MEM | I2 | Email |
|Client|<------->| Server |<---->| Server |
|______| ME-2|________| |________|
^
|ME-5
|
Figure 1: OMA MEM logical architecture
It identifies the following elements:
o The MEM client which implements the client-side functionality of
the OMA Mobile Email Enabler. It is also responsible for
providing the mobile email user experience and interface to the
user and storing the email and data to be sent to the MEM server
when not connected.
o The MEM server which implements the server-side functionality of
the OMA Mobile Email Enabler (MEM).
o The MEM protocol between the MEM Client and MEM Server. It is
responsible for all the data exchanges other than server to client
event notifications that take place between the MEM client and
server in order to update the MEM client with email server
changes, the email server with changes in the MEM client and to
send new email from the email server. Server to client
notifications of email server events can be transported via the
MEM protocol. We then speak of inband notifications. Note that
there are no client to server notifications.
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o Other OMA enablers are needed to directly support the mobile email
enabler. They are out of scope of IETF but they may include
support for:
* Client provisioning and management for over the air
installation of the MEM client on the device, provisioning of
its settings and revocation
* Messaging enablers for outband notification, where outband
notifications that are server to client event exchanges not
transported by the MEM protocol but via other channels. Such
channels may involve:
+ SMS including GSMSMS or WAP WDP a la EMN
+ MMS
+ WAP Push
+ SIP Push
+ Additional outband notifications like SIP push or SIP event
notify
+ UDP notifications
+ ...
OMA identifies different interfaces:
o ME-1: MEM client interface to interact via the MEM protocol with
the MEM server
o ME-2: Corresponding interface of the MEM server
o ME-3: Outband MEM server interfaces (e.g. to support generation of
server to client notifications).
o ME-4: Outband MEM client interfaces (e.g. to receive server to
client notifications).
o ME-5: Interface for management of MEM enabler server settings,
user preferences and filters (globally and per account). <Editor's
note: ME-5 is proposed in input contribution and not yet agreed by
OMA. Mention of ME-5 will be removed or updated based on the
disposition of teh proposal.>
It should be noted a single logical MEM server is identified. OMA
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MEM activity may support realizations not based on Internet Mail
protocols defined by the IETF that may not require distinguishing
email submissions from other MEM server functions.
In addition, the MEM server and MEM client may interfaces to other
mobile enablers.
Non-intrinsic functions can be provided by other enablers to enforce
service providers policies like:
o Charging for the traffic or usage
o Content conversion / transcoding
The MEM server enables an email server. In a particular
implementation, the email server may be packaged with (internal to
it) the MEM server or be in a separate component. In such cases,
interfaces to the email server are out of scope of the OMA MEM
specifications. In the present document, we focus on the case where
the backend consists of IETF LEMONADE enhanced IMAP and Submit
servers. However, relationship to other cases are also discussed.
The I2 interface is an OMA notation to designate protocol /
interfaces that are not specified by the MEM enabler but may be
standardized elsewhere.
3.2. OMA MEM Deployment Issues
The OMA MEM Architecture document [2] further identifies deployment
models.
Certain of these deployment models are not what IETF has
conventionally modeled. They require special attention to end-to-end
security aspects and may warrant introduction of additional security
measures (e.g. object level encryption).
3.2.1. OMA MEM proxy
The OMA MEM Architecture document [2] identifies OMA MEM server
proxies as server components that may be deployed ahead of firewalls
to facilitate traversal of firewalls.
Both IMAP and SMTP generally are compatible with proxies between the
client and the server. Such proxies may disrupt end-to-end
encryption, with the transport-level encryption ending at the proxy
and re-generating from the proxy to the server. Again this may
require additional security measures like object level encryption.
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3.2.2. OMA MEM deployment cases
OMA MEM identifies that each component (MEM client, MEM servers,
Other enablers and email server) may be deployed in different
domains, possibly separated by firewalls and other network
intermediaries. MEM proxies may be involved in front of firewall
that protects the MEM server domain.
OMA MEM target support of configurations where:
o All components are within a same domain (Mobile operator)
o MEM client and other enablers are in the mobile operator domain.
A MEM proxy is involved, deployed by the email service provider
(in front of its domain)and MEM server and email server are in the
domain of the email service provider
o MEM client and other enablers as well as a MEM proxy are in the
mobile operator domain, MEM server and email server are in the
domain of the email service provider
o MEM client and other enablers are in the mobile operator domain, a
MEM proxy is in a third party service provider domain and MEM
server and email server are in the domain of the email service
provider
o MEM client, other enabler and MEM server are in the mobile
operator domain and email server is in the domain of the email
service provider
o MEM client and other enablers are in the mobile operator domain,
MEM server is in a third party service provider domain and the
email server is in the domain of the email service provider
3.3. OMA MEM Required Technical Capabilities
The OMA MEM Architecture document [2] analyzes the OMA MEM
requirement [3] and presents a list of technical capabilities
required to satisfy them.
In Section 7 of this document, after review of how OMA MEM can be
realized with OMA and the resulting architecture, we describe how
each technical feature within scope of IETF are supported. We also
identify items left to OMA for specification
<Editor's note: Support of some of this is based on work in progress.
The document tracks the current thoughts on how features will be
supported. This may change as works evolves.>
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4. IETF LEMONADE Architecture
This section gives a brief introduction to the LEMONADE Architecture.
The IETF LEMONADE activity has derived a LEMONADE profile [4] with
the logical architecture represented in Figure 2, where arrows
indicate content flows.
______________
| |
_________| Notification |
| | Mechanism |
| |______________|
|Notif. ^
|Protocol |
| ___|______
| | | _____
__v__ IMAP | LEMONADE | ESMTP | |
| |<----------->| IMAP |<---------------| MTA |
| MUA |- | Store | |_____|
|_____| \ |__________|
\ |
\ |URLAUTH
\SUBMIT |
\ ____v_____
\ | | _____
\ | LEMONADE | ESMTP | |
---->| Submit |--------------->| MTA |
| Server | |_____|
|__________|
Figure 2: LEMONADE logical architecture
The LEMONADE profile [4] assumes:
o IMAP protocol [5] including LEMONADE profile extensions [4]
o SUBMIT protocol (SMTP [7], ...) including LEMONADE profile
extensions
o LEMONADE profile compliant IMAP store. connected to MTA (Mail
Transfer Agent) via ESMTP [6]
o LEMONADE profile compliant Submit server. connected to MTA via
ESMTP
o Lemonade profile message store / submit server protocols (URLAUTH)
(see [4]).
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o Outband server to client notifications relying on external
notification mechanisms (and notification protocols) that may be
out of scope of the LEMONADE profile.
o A LEMONADE aware MUA (Mail User Agent). While use of outband
notification is described in the LEMONADE profile, support for the
underlying notifications mechanisms/protocols is out of scope of
the LEMONADE specifications.
Further details on the IETF email protcol stack and architecture can
be found in [8]
Note that in Figure 2 the IMAP server and Submit server are
represented connected to MTAs (Mail Transfer Agents) via ESMTP [6].
This is not really essential. It could as well be X.400 so long as
the message is in the store in an onternet form.
OMA MEM identifies other functionalities. These are considered as
out of scope of the LEMONADE work and will need to be specified by
OMA MEM.
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5. Realization of OMA MEM Architecture with LEMONADE
This section details the use of the LEMONADE profile [4] to support
the OMA MEM Architecture.
5.1. Relationship between the OMA MEM and LEMONADE logical
architectures
Figure 3 illustrates the mapping of the IETF LEMONADE logical
architecture on the OMA MEM logical architecture.
_____________________
| Other_Mob. Enablers |
| |--------------| |
_________| Notification | |
| | | Mechanism | |
| | |______________| |
|Notif. |____________^________|
|Protocol ______|__________
ME-4 | | ___|_ME-3_ |
___|____ | | | | _____
| __v__ | IMAP | | LEMONADE | | ESMTP | |
|| |<----------->| IMAP |<-----------| MTA |
|| MUA || ME-2a | | Store | | |_____|
||_____||\ME-1 | |__________| |
| MEM | \ | | |
| Client| \ | |URLAUTH |
|_______| \SUBMIT | |
\ | ____v_____ |
\ | | | | _____
\ | | LEMONADE | | ESMTP | |
---->| Submit |----------->| MTA |
ME-2b | | Server | | |_____|
| |__________| |
|MEM Email |
|Server Server|
|_________________|
^
|ME-5
|
Figure 3: Mapping of LEMONADE logical architecture onto the OMA MEM
logical architecture.
As described in Section 4, the LEMONADE profile assumes LEMONADE
profile compliant IMAP stores and Submit servers. Because the
LEMONADE profile extends the IMAP store and the submit server, the
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mobile enablement of email provided by the LEMONADE profile is
directly provided in these server. Mapped to OMA MEM logical
architecture, for the case considered and specified by the LEMONADE
profile, the MEM server and email server logically combined. They
are however split into distinct LEMONADE message store and LEMONADE
submit server. ME-2 consists of two interfaces ME-2a and ME-2b
associated respectively to IMAP extended according to the LEMONADE
profile and SUBMIT extended according to the LEMONADE profile.
The MUA is part of the MEM client.
External notifications mechanism can be part of the other OMA enabler
specified by OMA (or other activities).
5.2. LEMONADE realization of OMA MEM with non-LEMONADE compliant
servers
The OMA MEM activity is not limited to enabling Lemonade compliant
servers. It explicitly identifies the need to support other
backends.
5.2.1. LEMONADE realization of OMA MEM with non-LEMONADE enhanced IMAP
servers
Figure 4 illustrates the case of IMAP servers that are not (yet)
LEMONADE compliant / enhanced with LEMONADE. In such case, the I2
interface between the MEM server components and the IMAP store and
submit server are IMAP and SUBMIT.
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______________
| |
_________| Notification |
| | Mechanism |
| |______________|
|Notif. ^
|Protocol |
| ___|______ _____________
| | LEMONADE | | | _____
__v__ IMAP | MEM | IMAP |NON-LEMONADE | ESMTP | |
| |<--------->|Enabler |<------>|IMAP |<----->| MTA |
| MUA |\ ME-2a | Server | |Store | |_____|
|_____| \ |__________| |_____________|
\ |
\ |URLAUTH
\SUBMIT |
\ ____v_____ _____________
\ | | | | _____
\ | LEMONADE | SUBMIT |NON-LEMONADE | ESMTP | |
-->| MEM | |Submit | | |
| Enabler |------->|Server |------>| MTA |
ME-2b | Server | | | |_____|
|__________| |_____________|
Figure 4: Architecture to support non-LEMONADE enhanced IMAP servers
with a LEMONADE realization of OMA MEM enabler.
5.2.2. LEMONADE realization of OMA MEM with non-IMAP servers
Figure 5 illustrates the cases where the message store and submit
servers are not IMAP store or submit servers. They may be POP3
servers or other proprietary message stores.
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______________
| |
_________| Notification |
| | Mechanism |
| |______________|
|Notif. ^
|Protocol |
| ___|______ _____________
| | LEMONADE | | | _____
__v__ IMAP | MEM | I2 |Proprietary | ESMTP | |
| |<--------->|Enabler |<------>|Message |<----->| MTA |
| MUA |\ ME-2a | Server | |Store | |_____|
|_____| \ |__________| |_____________|
\ |
\ |URLAUTH
\SUBMIT |
\ ____v_____ _____________
\ | | | | _____
\ | LEMONADE | I2 |Proprietary | ESMTP | |
-->| MEM | |Submit | | |
| Enabler |------->|Server |------>| MTA |
ME-2b | Server | | | |_____|
|__________| |_____________|
Figure 5: Architecture to support non-IMAP servers with a LEMONADE
realization of OMA MEM enabler.
I2 designates proprietary adapters to the backends. They may invoved
functions performed in the message stores or submit server as well as
in the MEM enabler server.
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6. Filters and server to client notifications and LEMONADE
OMA MEM RD [3] and AD [2] emphasize the need to provide mechanisms
for server to client notifications of email events and filtering.
Figure 6 illustrates how notification and filterings are introduced
in LEMONADE profile [4].
______________
| |
_________| Notification |
| | Mechanism |
| |______________|
|Notif. ^
|Protocol -------\ _|_
| ______| ___\>|NF|____
| | | ---- | _____
__v__| IMAP |__ LEMONADE |___ ESMTP __| |
| |<-------->|VF| IMAP |DF |<--------|AF| MTA |
| MUA |\ ME-2a |-- Store |-^- --|_____|
|_____| \ |_____________| |
\_\_______________|_______|
\ |URLAUTH
\SUBMIT |
\ ____v_____
\ | | _____
\ | LEMONADE | ESMTP | |
---->| Submit |--------------->| MTA |
ME-2b | Server | |_____|
|__________|
Figure 6: Filtering mechanism defined in LEMONADE architecture
In Figure 6, four categories of filters are defined:
o AF: Administrative Filters - Set up by email service provider. AF
are typically not configured by the user and set to apply policies
content filtering, virus protection, spam filtering etc...
o DF: Deposit Filters - Filters that are executed on deposit of new
emails. They can be defined as SIEVE filters [9]. They can
include vacation notices.
o VF: View Filters - Filters that define which emails are visible to
the MUA. View filters can be defined as virtual folders [10] as
described in [11].
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o NF: Notification Filters - Filters that define for what email
server event an outband notification is sent to the client.
The filters are manageable from the MUA:
o NF and DF: via SIEVE management protocol <Editor's note: Still to
be defined>
o VF: via LFILTER as virtual folder as defined in [11]
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7. Analysis of Lemonade Technology Support of OMA MEM enabler
The OMA MEM AD [2] analyzes the technical features needed to support
its requirements [3].
In the present section we explain how these features extracted from
the OMA MEM AD are supported with a LEMONADE realization.
Items maked as ** indicate how it is currently thought that this is
addressed by LEMONADE. ++ refers to OMA aspects. -- refers to issues
that are not within the scope of LEMONADE specifications or that are
still unresolved at the level of LEMONADE.
1. Mechanisms to align, fetch and update email messages between the
MEM client and the email server via the MEM server. The mobile
email enabler focuses solely on the interaction between the MEM
client and MEM server.
* ** This is supported by IMAP base capabilities.
2. Mechanisms for event-based server to client alignment:
* Defines the relationship between notification mechanisms and
MEM protocol.
* ** This is supported by server to client notifications [11]
+ To minimize the latency observed for email events on the
email server to be reflected in the MEM client.
+ To avoid unnecessary polling and requests from the MEM
clients:
- To reduce the total amount of data to be exchanged
between MEM server and client, e.g. by allowing the MEM
client to select which messages to align.
- To reduce the amount of transactions.
* Needs to cope with possible lost or delayed notifications
* ** This is supported by ensuring that the LEMONADE protocol
does not require that the notification have been received by
the MUA.
* Support in-band (ME-1/ME-2 exchanges) and out-band
notifications (Exchanged via ME-3/ME-4 via other enablers).
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* ** In-band notifications are supported by IMAP IDLE [12]
acting on the virtual folder defined by VF
* ** Outband notifications are generated by SIEVE bound to
message store events [13] and acting on the virtual folder
defined by VF.
+ Specified in ways that are network transport independent
but may contain some bindings to particular notification
channels (e.g. SMS binary, WAP Push, SIP Notification,
...)
+ When the MEM client is connected to the MEM server, only
inband notifications shall take place
* Defines notification payload for inband and outband
mechanisms.
* ** For inband this is defined by IMAP IDLE
* ++ For outband this is specified by server to client
notifications [11]. It is expected to be based on OMA EMN
server to client notifications [14] plus possible extensions.
* Server-side filtering to decide which messages will be
accessible by the MEM client.
+ Filtering results into the following logical types:
+ ** This is achieved by usage of view filters defined as
virtual folders, SIEVE binding to message store events.
- Type A: Messages filtered out and not accessible by the
MEM client (no notification, no header access, no
access)
- ** Achieved via VF as view filter defined as virtual
folder. No notification will affect events related to
these messages by restricting that NF applies only on
the view. Otherwise, NF and VF must be synchronized.
- Type B: Messages that are accessible by the MEM client
but no outband notification takes place. Inband
notification might however take place if MEM client is
already connected to MEM server.
- ** Achieved via VF as view filter defined as virtual
folder. NF is then set to suppress (i.e. not produce)
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notifications even when tehse messages are made
available by VF.
- Type C: Messages that are accessible by the MEM client
for which notifications (outband or inband) are always
sent to the MEM client.
- ** Achieved via NF using SIEVE and bindings to messages
store events.
+ Notions of Filters:
- View filters: Filters that determine which email
messages are of type B and C or A
- ** VF is defined as as virtual folder. This may be
updated from the client via LFILTER mechanisms [11].
- Notification filters: Filters that determine which
email messages are of type C or B
- Event filters: Filters that determines what events are
to be notified to the client
+ Mechanisms to allow the user to update the filters from
the MEM client
+ ** This can be achieved by LFILTER.
3. Client-side download and storage preferences:
* Manage which of the accessible messages are maintained on MEM
client
* ** This is achieved via the view filter defined as virtual
folder.
* -- From a LEMONADE point of view, client specific additional
aspects are left to specifications of the MEM client
implementations or to OMA MEM specifications (out of scope of
LEMONADE): the user may set local client preferences to cache
less than their view filter. For example, the client may
cache only the last N days while receiving view updates on
all messages within the "urgent" view.
* Manage which parts are maintained on MEM client
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* ** This is achieved by IMAP
* -- Aspects are left to specifications of the MEM client
implementations or to OMA MEM specifications (out of scope of
LEMONADE).
* Configurable by user
* -- This is left to specifications of the MEM client
implementations or to OMA MEM specifications (out of scope of
LEMONADE).
* MEM client may support encrypting and password protecting the
messages.
* -- This is left to specifications of the MEM client
implementations or to OMA MEM specifications (out of scope of
LEMONADE).
4. Client-side event filtering:
* Local message store delete: ability to delete email message
from the MEM client view while retaining the message on the
email server. Some information may be passed to the MEM
server.
* -- This is left to specifications of the MEM client
implementations (out of scope of LEMONADE).
* Attachment local delete: Ability to delete from the MEM
client the attachment while maintaining the view that an
attachment is available for download from the email server.
* -- This is left to specifications of the MEM client
implementations (out of scope of LEMONADE).
* Remote delete: ability to delete email messages both on the
MEM client and on the email server.
* ** Support by IMAP
5. Mechanisms for media conversion
* ** This is supported by CONVERT [15].
* Allows the MEM client to request conversion - including
transcoding - of a body part or attachment from the MEM
server when the email message part is fetched from the
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server.
+ The client may request conversion to a specific format/
size, or
+ The client may request conversion to a server-selected
format/size - where the server decides the format/size
credentials based on any knowledge (e.g. client
capabilities, user preferences) it may have.
* Conversion does not alter the messages in the email server.
6. Mechanisms for MEM client to submit email to the MEM server.
* ** This is achieved by SMTP - Submit
* Mechanism to support remote message assembly on the MEM
server based on email parts (body, address fields and
attachments) that may not have been downloaded and others
that may have been locally created or may have been
downloaded and edited.
* This is supported by LEMONADE profile trio: BURL, CATENATE,
URLAUTH [4]
* It may be desirable to support just uploading the differences
of the body parts (e.g. address fields).
* -- This may be achievable by IMAP URL extended with byte
range (partial) [16].
* -- Differences on address fields may require SMTP extensions.
This is under discussion.
7. Mechanisms to allow configuration and exchange of settings
between the client and the server inband or outband:
* Server to client: e.g. server ID, account name, policies, ...
* ++ This is achievable by OMA DM / CP <Editor's note: Add
references>
* ** Most configuration beyond bootstrap is also achievable via
mailbox annotations <Editor's note: Add references>
* Client to server: e.g. rules filters vacation notices,
notification channel, ...
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* ** A remote management protocol is to be defined for DF and
NF that provide SIEVE management.
* ** SETPREFS/GETPREFS for server to client notifications [11]
8. Mechanisms to optimize bandwidth and/or delays on any data
exchanges
* ** This is addressed by IMAP BINARY, TLS Compression and LZIP
compression. Exact usage guidelines are still under
development
9. Mechanisms for encryption of the email data exchanged between
the email server and the MEM client.
* ** This is supported by TLS. Note TLS just protects between
the MEM client and the MEM server (or may be just to the MEM
proxy in front of the MEM server if there is one).
* The enabler shall support data remaining encrypted at all
times even if the MEM server is deployed outside the email
server domain.
* -- This may require object level encryption under some
circumstances (e.g. to support deployment models where proxy
/ MEM server outside email service provider domain). This is
still under discussion.
* The mechanism should also be applicable to notifications if
they carry information worth protecting.
* ** The current thought is to reduce the notifications to the
exchange of information that may not have to be encrypted.
This is still work in progress.
10. Mechanisms for the MEM client to determine the capabilities of
the server.
* ** This can be supported by CAPABILITY, Mailbox annotations.
The notion of Sieve Capabilities description is also work in
progress.
11. Mechanisms to manage sessions:
* ** Covert by Quick Reconnect [17]
* Handling connectivity issues
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+ E.g. dealing with IP address changes
+ E.g. re-establish secure connection
* E.g. suspend and resume minimizing data exchange duplication
12. Capability to support the different deployment models in
appendix of OMA MEM AD [2]
* Mobile email must be usable in the presence of firewalls and
intermediaries found in mobile networks.
* ** This is discussed in [20]
* ** Best practices exist [19].
* -- This may require presence of LEMONADE proxy MEM servers
(i.e. Lemonade enhanced IMAP or Submit proxies)
* -- This may require the use of HTTP binding [18]
13. Mechanisms to ensure integrity of the email data exchanged
between the email server and the MEM client.
* ** This is supported by TLS with the TLS limitations pointed
out above for confidentiality <Editor's note: Add
references>.
14. Mechanisms for mutual authentication of the MEM client and the
MEM server.
* ** This is supported by TLS <Editor's note: Add references>.
15. Mechanism to allow the MEM client to send recall request to the
email server via the MEM server.
* -- This is a feature that we believe can not easily be
satisfied for internet email. We note that some proposals
have been made for addressing this with extensions to the
MSGTRAK work <Editor's note: Add references>.
16. Mechanisms to sign data exchanged between MEM client and MEM
server.
* ** This is supported by TLS with the TLS limitations
mentioned above <Editor's note: Add references> and providing
that having a signature of the MEM server or MEM proxy is
somehow meaningful.
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17. Mechanisms to allow the MEM client to work off line or in
intermittent connectivity:
* ** This is already built in IMAP
* ** This is addressed by QuickReconnect <Editor's note: Add
references>
* -- This are also aspects left to specifications of the MEM
client implementations (out of scope of LEMONADE).
* Store email and client email event
* Detect network availability
* Send emails and email client events when network connectivity
is available
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8. Security considerations
This specification provides no security measures beyond those in the
referenced Internet Mail and LEMONADE documents.
We note however the security risks associated to:
o Outband notifications
o Server configuration by client
o Client configuration by server
o Presence of MEM proxy servers
o Presence of MEM servers as intermediaries
o In general the deployment models considered by OMA MEM that are
not conventional IETF deployment models.
o Measures to address the need to traverse firewalls
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9. IANA considerations
No specific IANA considerations have been identified that are not
covered by the different drafts and RFCs included in the realization
described in this document.
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10. Acknowledgements
The authors acknowledge and appreciate the work and comments of the
IETF LEMONADE working group and the OMA MEM working group.
This text was partially co-authored with G. Vaudreuil (Lucent) and
Eric Burger (Excel) and reviewed in detail by them as well as by Fan
Xiaohui (China Mobile - CMCC).
11. References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirements Levels", RFC 2119, BCP 14, March 1997.
[2] "Mobile Email Architecture Document", OMA (Work in Progress),
http://www.openmobilealliance.org/, October 2005.
[3] "Mobile Email RequirementS Document", OMA http://
www.openmobilealliance.org/release_program/docs/RD/
OMA-RD-MobileEmail-V1_0_20051018-C.pdf, Oct 2005.
[4] Maes, S. and A. Melnikov, "LEMONADE profile",
draft-ietf-lemonade-profile-0x (work in progress).
[5] Crispin, M., "IMAP4, Internet Message Access Protocol Version 4
rev1", RFC 3501, March 2003.
[6] Klensin, J., "SMTP Service Extensions", RFC 1861,
November 1995.
[7] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001.
[8] Crocker, D., "Internet Mail Architecture",
draft-crocker-email-arch-0x (work in progress).
[9] "SIEVE WG", http://www.ietf.org/html.charters/sieve-
charter.html.
[10] Maes, S. and et Al., "Persistent Search Extensions and Virtual
Folder to the IMAP Protocol", draft-maes-lemonade-vfolder-0x
(work in progress).
[11] Maes, S. and et Al., "Server to Client Notifications and
Filtering",
draft-maes-lemonade-notifications-server-to-client-0x (work in
progress).
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[12] Leiba, B., "IMAP4 IDLE command", RFC 2177, June 1997.
[13] Newman, C., "Internet Message Store Events",
draft-newman-lemonade-msgevent-0x (work in progress).
[14] "Open Mobile Alliance Email Notification Version 1.0",
OMA http://www.openmobilealliance.org/tech/docs/EmailNot/OMA-
Push-EMN-V1_0-20020830-C.pdf, August 2002.
[15] Maes, S. and et Al., "CONVERT", draft-ietf-lemonade-convert-0x
(work in progress).
[16] Melnikov, A. and et Al., "IMAP URL Scheme",
draft-ietf-lemonade-rfc2192bis-0x (work in progress).
[17] Melnikov, A. and et Al., "IMAP4 extension for quick reconnect",
draft-ietf-lemonade-reconnect-0x (work in progress).
[18] Maes, S. and et Al., "Lemonade HTTP Binding",
draft-maes-lemonade-http-binding-0x (work in progress).
[19] Freed, N., "Behavior of and Requirements for Internet
Firewalls", RFC 2979, October 2000.
[20] Maes, S., "Lemonade and the challenges of Intermediaries",
Internet-Draft ddraft-smaes-lemonade-intermediary-challenges-
0x.
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Authors' Addresses
Stephane H. Maes
Oracle
MS 4op634, 500 Oracle Parkway
Redwood Shores, CA 94539
USA
Phone: +1-203-300-7786
Email: stephane.maes@oracle.com
Glenn Parsons
Nortel
3500 Carling Avenue
Ottawa, ON K2H 8E9
CA
Phone: +1 613 763 7582
Email: gparsons@nortel.com
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