LEMONADE Architecture - Supporting Open Mobile Alliance (OMA) Mobile Email (MEM) Using Internet Mail
draft-ietf-lemonade-architecture-04
The information below is for an old version of the document that is already published as an RFC.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 5442.
|
|
|---|---|---|---|
| Authors | Eric Burger , Glenn Parsons | ||
| Last updated | 2015-10-14 (Latest revision 2008-11-03) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Informational | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | (None) | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 5442 (Informational) | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Chris Newman | ||
| Send notices to | alexey.melnikov@isode.com |
draft-ietf-lemonade-architecture-04
LEMONADE Working Group E. Burger
Internet-Draft This Space for Sale
Intended status: Informational G. Parsons
Expires: May 7, 2009 Nortel Networks
November 3, 2008
LEMONADE Architecture - Supporting Open Mobile Alliance (OMA) Mobile
Email (MEM) using Internet Mail
draft-ietf-lemonade-architecture-04
Status of this Memo
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Abstract
This document specifies the architecture for mobile email, as
described by the Open Mobile Alliance (OMA), using Internet Mail
protocols. This architecture was an important consideration for much
of the work of the LEMONADE (Enhancements to Internet email to
Support Diverse Service Environments) work group in the IETF. This
document also describes how the LEMONADE architecture meets the OMA's
requirements for their Mobile Email (MEM) service.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. OMA Mobile Email (MEM) . . . . . . . . . . . . . . . . . . . . 3
2.1. OMA MEM Requirements . . . . . . . . . . . . . . . . . . . 3
2.2. OMA MEM Architecture . . . . . . . . . . . . . . . . . . . 3
2.2.1. OMA MEM logical Architecture . . . . . . . . . . . . . 3
2.2.2. OMA MEM Deployment Issues . . . . . . . . . . . . . . 5
2.3. OMA MEM Technical Specification . . . . . . . . . . . . . 6
3. IETF LEMONADE Architecture . . . . . . . . . . . . . . . . . . 6
3.1. Relationship between the OMA MEM and LEMONADE logical
architectures . . . . . . . . . . . . . . . . . . . . . . 8
3.2. LEMONADE realization of OMA MEM with non-LEMONADE
compliant servers . . . . . . . . . . . . . . . . . . . . 9
3.2.1. LEMONADE realization of OMA MEM with non-LEMONADE
IMAP servers . . . . . . . . . . . . . . . . . . . . . 9
3.2.2. LEMONADE realization of OMA MEM with non-IMAP
servers . . . . . . . . . . . . . . . . . . . . . . . 10
4. Filters and server to client notifications and LEMONADE . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 13
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
8. Informative References . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . . . . 16
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1. Introduction
This document describes the architecture of OMA mobile email (MEM)
using Internet Mail protocols defined by the IETF. The LEMONADE work
group has enhanced many of these protocols for use in the mobile
environment. The LEMONADE profile [PROFILE] and its revision
LEMONADE profile bis [PROFILE-bis] summarize such protocols and
protocol use. This document shows how the OMA MEM Requirement
document [MEM-req], OMA MEM Architecture [MEM-arch], and OMA MEM
Technical Specification [MEM-ts] relate to the work of LEMONADE in
the IETF.
2. OMA Mobile Email (MEM)
The OMA Mobile Email (MEM) sub-working group has spent some time
studying the requirements and architecture of mobile email. IETF
LEMONADE has been liaising with them and has based much of our
Internet Mail enhancements based on their input. This section
summarizes the output of the OMA.
2.1. OMA MEM Requirements
The OMA MEM activity collected a set of use cases and derived
requirements for a mobile email enabler (MEM). The OMA MEM
Requirements [MEM-req] summarizes this work. 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.
2.2. OMA MEM Architecture
This section introduces the OMA MEM Architecture.
2.2.1. OMA MEM logical Architecture
The OMA MEM activity has derived a logical architecture from the
requirements and use cases described in [MEM-req]. A simplification
for illustrative purposes is shown in Figure 1, where arrows indicate
content flows.
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__________
| Other |
+---| Mobile |<--+
| | Enablers | |
| |__________| |
|ME-4 |ME-3
_v____ ___v____ ________
| |ME-1 | | | |
| MEM |-------->| MEM | I2 | Email |
|Client| ME-2| Server |<---->| Server |
|______|<--------|________| |________|
^
|ME-5
|
Figure 1: Basic OMA MEM logical architecture
Figure 1 identifies the following elements:
o The MEM client that 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 that 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 in-band data exchanges 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.
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 out-of-band notification, where out-of-
band notifications that are server to client event exchanges
not transported by the MEM protocol but via other channels, and
* Billing, charging, and so on.
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
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o ME-3: Out-of-band MEM server interfaces, for example to support
generation of server to client notifications.
o ME-4: Out-of-band 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.
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 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 IMAP and Submit servers. However, we
also discuss the relationship to other cases. The I2 interface is an
OMA notation to designate protocol / interfaces that are not
specified by the MEM enabler but may be standardized elsewhere.
2.2.2. OMA MEM Deployment Issues
The OMA MEM Architecture document [MEM-arch] further identifies
deployment models.
2.2.2.1. OMA MEM proxy
The OMA MEM Architecture document [MEM-arch] identifies OMA MEM
server proxies as server components that may be deployed ahead of
firewalls to facilitate firewall traversal.
2.2.2.2. OMA MEM deployment cases
OMA MEM identifies that each component (MEM client, MEM servers,
other enablers, and the 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 targets support of configurations where:
o All components are within the same domain, such as in a mobile
operator
o MEM client and other enablers are in the mobile operator domain,
there is a MEM proxy, and the 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
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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
The e-mail service provider can be a third-party service provider, a
network service provider, or an enterprise e-mail service.
2.3. OMA MEM Technical Specification
The OMA MEM activity will conclude with a specification for a mobile
email enabler (MEM). The ongoing work is in OMA MEM Technical
Specification [MEM-ts]. LEMONADE is a basis for the mechanism.
However, some additional details that are outside the scope of IETF
will also be included.
OMA provides ways to perform provisioning via OMA client provisioning
and device management. Other provisioning specifications are
available (e.g., SMS based).
OMA provides enablers to support out-of-band notification mechanisms,
as well as filter specifications (such as XDM), remote device
deactivation, and other, non-Internet activities.
3. IETF LEMONADE Architecture
This section introduces the LEMONADE Architecture.
The IETF LEMONADE activity has derived a LEMONADE profile
[PROFILE-bis] with the logical architecture represented in Figure 2,
where arrows indicate content flows.
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______________
| |
_________| 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 [PROFILE] assumes:
o IMAP protocol [RFC3501] including LEMONADE profile extensions
[PROFILE]
o SUBMIT protocol [RFC4409], including LEMONADE profile extensions
o LEMONADE profile compliant IMAP store connected to MTA (Mail
Transfer Agent) via ESMTP [EMAIL]
o LEMONADE profile compliant Submit server connected to an MTA,
often via ESMTP
o Out-of-band 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 out-of-band
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 protocol stack and architecture can
be found in [MAIL]
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3.1. 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 3, 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
mobile enablement of email provided by the LEMONADE profile is
directly provided in these servers. Mapping to the OMA MEM logical
architecture, for the case considered and specified by the LEMONADE
profile, we logically combine the MEM server and email server.
However, in lemonade we split them logically into a distinct LEMONADE
message store and a LEMONADE submit server. ME-2 consists of two
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interfaces. ME-2a is IMAP extended according to the LEMONADE
profile. ME-2b is SUBMIT extended according to the LEMONADE profile.
The MUA is part of the MEM client.
The external notifications mechanism is part of OMA enablers
specified by the OMA.
3.2. 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 back-
ends. This is, of course, outside the scope of the IETF Lemonade
activity.
3.2.1. LEMONADE realization of OMA MEM with non-LEMONADE IMAP servers
Figure 4 illustrates the case of IMAP servers that are not LEMONADE
compliant. In such case, the I2 interface between the MEM server
components and the IMAP store and submit server are IMAP and SUBMIT
without Lemonade extensions.
It is important to note the realizations are of a schematic nature
and do not dictate actual implementation. For example, one could
envision collocating the LEMONADE MEM Enabler Server and the Submit
Server shown in Figure 4 in a single instantiation of the
implementation. Likewise, we consciously label the LEMONADE MEM
Enabler as neither an IMAP Proxy nor an IMAP back-to-back user agent.
LEMAONDE leaves the actual implementation to the developer.
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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 IMAP servers with a
LEMONADE realization of an OMA MEM enabler
3.2.2. 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 back-ends.
4. Filters and server to client notifications and LEMONADE
OMA MEM RD [MEM-req] and AD [MEM-arch] emphasize the need to provide
mechanisms for server to client notifications of email events and
filtering. Figure 6 illustrates how notification and filtering works
in the LEMONADE profile [PROFILE].
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______________
| |
_________| 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, we define four categories of filters:
o AF: Administrative Filters - The e-mail service provider usually
sets administrative filters. The user typically does not
configure AF. AF applies policies covering 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 [SIEVE]. They can
include vacation notices [RFC5230]. As SIEVE filters, one can
administer them using the SIEVE management protocol [MANAGESIEVE].
o VF: View Filters - Filters that define which emails are visible to
the MUA. View filters can be performed via IMAP using the
facilities described in [NOTIFICATIONS].
o NF: Notification Filters - Filters that define for what email
server event an out-of-band notification is sent to the client, as
described in [NOTIFICATIONS].
Refer to the aforementioned references for implementation and
management of the respective filters.
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5. Security Considerations
We note there are security risks associated with:
o Out-of-band 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 Measures to address the need to traverse firewalls
We refer the reader to the relevant Internet Mail, IMAP, SUBMIT, and
Lemonade documents for how we address these issues.
6. IANA considerations
None.
7. Acknowledgements
The authors acknowledge and appreciate the work and comments of the
IETF LEMONADE working group and the OMA MEM working group. We
extracted the contents of this document from sections of
draft-ietf-lemonade-profile-bis-05.txt by Stephane Maes, Alexey
Melnikov and Dave Cridland, as well as sections of
draft-ietf-lemonade-notifications-04.txt by Stephane Maes and Ray
Cromwell.
8. Informative References
[MEM-arch]
Open Mobile Alliance, "Mobile Email Architecture
Document", June 2007, <http://
member.openmobilealliance.org/ftp/public_documents/mwg/
MEM/Permanent_documents/
OMA-AD-Mobile_Email-V1_0_0-20070614-D.zip>.
[MEM-req] Open Mobile Alliance, "Mobile Email Requirements
Document", OMA http://www.openmobilealliance.org/,
Oct 2005.
[MEM-ts] Open Mobile Alliance, "Mobile Email Technical
Specification", OMA (Work in Progress),
http://www.openmobilealliance.org/, Oct 2007.
[PROFILE] Maes, S. and A. Melnikov, "Internet Email to Support
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Diverse Service Environments (Lemonade) Profile",
RFC 4550, June 2006.
[PROFILE-bis]
Cridland, D., Melnikov, A., and S. Maes, "The Lemonade
Profile", draft-ietf-lemonade-profile-bis-11 (work in
progress), September 2008.
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, March 2003.
[EMAIL] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
October 2008.
[RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail",
RFC 4409, April 2006.
[RFC5230] Showalter, T. and N. Freed, "Sieve Email Filtering:
Vacation Extension", RFC 5230, January 2008.
[SIEVE] Guenther, P. and T. Showalter, "Seive: An Email Filtering
Language", RFC 5528, January 2008,
<ftp://ftp.isi.edu/in-notes/rfc5528.txt>.
[NOTIFICATIONS]
Gellens, R. and S. Maes, "Lemonade Notifications
Architecture", draft-ietf-lemonade-notifications-10 (work
in progress), July 2008.
[MAIL] Crocker, D., "Internet Mail Architecture",
draft-crocker-email-arch-11 (work in progress),
October 2008.
[MANAGESIEVE]
Melnikov, A. and T. Martin, "A Protocol for Remotely
Managing Sieve Scripts", draft-ietf-sieve-managesieve-01
(work in progress), November 2008.
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Authors' Addresses
Eric W. Burger
This Space for Sale
New Hampshire
USA
Phone:
Fax: +1 530-267-7447
Email: eburger@standardstrack.com
URI: http://www.standardstrack.com
Glenn Parsons
Nortel Networks
3500 Carling Avenue
Ottawa, ON K2H 8E9
Canada
Phone: +1 613 763 7582
Email: gparsons@nortel.com
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