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Versions: 00                                                            
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

Status of this Memo

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   This Internet-Draft will expire on June 7, 2006.

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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