Internet Engineering Task Force SIMPLE WG
Internet Draft J. Rosenberg
dynamicsoft
M. Isomaki
Nokia
draft-ietf-simple-data-req-01.txt
February 23, 2003
Expires: August 2003
Requirements for Manipulation of Data Elements in SIMPLE Systems
STATUS OF THIS MEMO
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress".
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html.
Abstract
In any presence application, it is frequently necessary for the user
to configure a number of pieces of information. Users will need to
manipulate their presentity list, adding and removing presentities,
and manipulate their authorization lists, which specify the set of
users that can subscribe to their presence. In this document, we
provide a framework and requirements for such data manipulations.
J. Rosenberg et. al. [Page 1]
Internet Draft Data Requirements February 23, 2003
Table of Contents
1 Introduction ........................................ 3
2 Terminology ......................................... 3
3 Framework ........................................... 4
4 Presentity Collection Manipulation Requirements ..... 6
5 Authorization Policy Manipulation ................... 8
5.1 Acceptance Policy Requirements ...................... 8
5.2 Notification Requirements ........................... 10
5.3 Content Requirements ................................ 10
5.4 General Requirements ................................ 11
6 Security Considerations ............................. 12
7 To Do ............................................... 13
8 Acknowledgements .................................... 13
9 Authors Addresses ................................... 13
10 Normative References ................................ 13
11 Informative References .............................. 13
J. Rosenberg et. al. [Page 2]
Internet Draft Data Requirements February 23, 2003
1 Introduction
Consumer-based instant messaging and presence applications typically
provide a rich set of features. In addition to being able to
subscribe to, and get notified of, changes in presence, users can
also configure the operation of the application.
Most systems allow the user to add or remove users from their "buddy
list", which we refer to here as a presentity collection. The
presentity collection is the set of presentities [1] that a user is
subscribed to. This list is frequently stored on the server, allowing
the user to generate a single subscription to the entire list. The
server then "fans out" that subscription too all the presentities on
the list. Subscription to presentity collections is supported through
the SIP event notification extension for collections [2]. However, no
automated means is currently defined to create these lists, add users
to them, remove users from them, or query for the set of users on the
list.
Similarly, most systems support user-defined authorization policies.
A user can specify which watchers are (or are not) allowed to
subscribe to their presence, and furthermore, what aspects of their
presence a watcher is able to see. While SIMPLE [3] systems can
support such authorization policies, besides human-driven techniques,
such as web or voice response, there is no automated way to specify
these policies.
In this document, we propose a framework and a set of requirements
for manipulation of presentity collections and authorization
policies.
2 Terminology
This document uses the following terminology:
Presentity Collection: A presentity collection is a set of
presentities, each of which is identified by a URI. The
collection itself is identified by a URI (for example,
sip:myfriends@example.com). Using the SIP event extension
for collections [2], a watcher can subscribe to the
presentity collection and learn about the presence state of
all the presentities in the set.
Presence Authorization Policy: Presence authorization policy
refers to the set of directives given to a presence agent
on what subscriptions to accept, when to generate
notifications for a subscription, and what information
should be placed in those notifications.
J. Rosenberg et. al. [Page 3]
Internet Draft Data Requirements February 23, 2003
Acceptance Policy: The component of presence authorization
policy that determines whether or not to accept a
subscription from a watcher.
Notification Policy: The component of presence authorization
policy that determines when a notification should be sent
to a watcher.
Content Policy: The component of presence authorization that
determines the content of the information provided to a
watcher in a notification.
SIMPLE Data Elements: SIMPLE data elements are user specified
data that determine the behavior of a presence agent. This
includes presentity collections and presence authorization
policy.
Data Manipulation Client: A data manipulation client is a
protocol agent that reads, writes, and receives
notifications of changes in SIMPLE data elements.
Data Manipulation Server: A data manipulation server is a
protocol agent that receives reads, writes, and sends
notifications of changes in SIMPLE data elements. The
server is responsible for the storage of the SIMPLE data
elements.
3 Framework
The framework for the the usage and manipulation of SIMPLE data
elements is shown in Figure 1.
The data manipulation client (just referred to as the client) uses
some protocol, whose requirements are specified here, to interact
with the data manipulation server. Those interactions include
requests to read a SIMPLE data element, write one, or receive
notifications in changes to one. The data manipulation server (just
referred to as the server) mananges a persistent store of the SIMPLE
data elements, and interacts with the client.
When a Presence Agent (PA) receives a SIP SUBSCRIBE request [3], it
may require access to SIMPLE data elements in order to process the
request. For example, if the subscription is for a presentity
collection, the PA will need to determine that this is the case, and
secondly, "expand" the collection, obtaining the list of URIs for
that collection.
J. Rosenberg et. al. [Page 4]
Internet Draft Data Requirements February 23, 2003
SUBSCRIBE +--------+
--------------->| | Read
| PA |<--+ //----\\
<---------------| | | || ||
NOTIFY +--------+ +--- \\----//|
| |
| Storage|
| |
+--------+ | |
| Server |------> | |
| | Write \ /
| | \------/
+--------+
^ |
| |
| | PC/Auth
| | Manipulations
| |
| |
| V
+--------+
| Client |
| |
| |
+--------+
Figure 1: Framework for Data Manipulation
If the SUBSCRIBE request is for a presentity, the PA will need to
obtain the presence authorization policy of that presentity in order
to process the SUBSCRIBE request.
In both cases, the PA requires only read access to the data. As a
result, it obtains it directly from the data store, rather than
interacting with the server. This, of course, is just a model of the
system; a real implementation might involve interaction with the
J. Rosenberg et. al. [Page 5]
Internet Draft Data Requirements February 23, 2003
server before reading the data.
Between the presentity collection and presence authorization policy,
the presence authorization policy is a far more complicated piece of
data. The authorization policy can be reasonably split into three
separate pieces. The first, which we call the acceptance policy,
determines whether or not to grant a subscription to the subscriber.
This policy results in a binary decision. The second piece, which we
call the notification policy, determines when that particular
subscriber should receive notifications. For example, a subscriber
might only be permitted to see when I log in or log out of IM, but
not receive notifications when my phone goes on hook. This is closely
related to the third piece, which we call the content policy. This
policy specifies the content of the information present in a
notification that is sent to a subscriber.
All of these policies are data that is manipulated by the data
manipulation protocol.
4 Presentity Collection Manipulation Requirements
The following are the set of requirements for the protocol between
the client and the server for the purposes of manipulation presentity
collections.
REQ 1: It MUST be possible for the client to create a presentity
collection and associate it with a URI.
REQ 2: It MUST be possible for the user to specify the URI for
the presentity collection when one is created. If the name
cannot be allocated (because it already exists, for
example), it MUST be possible to inform the client of the
failure, and the reason for it.
REQ 3: It MUST be possible for the server to provide the client
a URI for the list when one is created, in the case where
the client does not provide it.
REQ 4: It MUST be possible to add an entry to the presentity
collection. Each entry MUST consist of at least a URI, and
MAY include a display name. It MUST be possible for the
entry to be any URI that is meaningful in the context of a
presentity collection. Examples would include a SIP URI or
pres URI [4].
REQ 5: It MUST be possible for a presentity collection to
contain entries which are themselves presentity
collections.
J. Rosenberg et. al. [Page 6]
Internet Draft Data Requirements February 23, 2003
REQ 6: It MUST be possible to remove an entry from the
presentity collection. If the entry does not exist, it MUST
be possible for the server to inform the client of this
fact.
REQ 7: It MUST be possible to clear all entries from a
presentity collection.
REQ 8: It MUST be possible to delete a presentity collection. In
this context, deleted means that the name of the presentity
collection is no longer defined, so that subscriptions to
the list would fail.
REQ 9: It MUST be possible to query for the set of URIs in a
particular presentity collection, by providing the URI for
the presentity collection.
REQ 10: It MUST be possible for the presentity collection to be
associated with a list of authorized users. Those
authorized users are the only ones permitted to manipulate
the presentity collection.
REQ 11: It MUST be possible for the presentity collection to be
associated with a list of users that are authorized to
subscribe to the list.
REQ 12: It MUST be possible for a client to store a cached copy
of the list. This implies that it MUST be possible for the
server to notify the client of a change in the list. It
MUST be possible for the client to manipulate the local
cached copy even when there is no connectivity to the
server. It MUST be possible to synchronize the cached copy
with the master copy on the server, when connectivity is
re-established.
This particular requirement is crucial for wireless
systems, where a copy of the list resides ont he handset.
Without this requirement, a user would not be able to view
the list, or add a user to it, when they go out of
coverage.
REQ 13: It MUST be possible for there to be multiple clients
with cached copies of the list.
REQ 14: Manipulations of the presentity collection MUST exhibit
the ACID property; that is, they MUST be atomic, be
consistent, durable, and operate independently.
J. Rosenberg et. al. [Page 7]
Internet Draft Data Requirements February 23, 2003
REQ 15: It MAY be possible for the client to batch multiple
operations (add a presentity, remove a presentity) into a
single request that is processed atomically.
REQ 16: It MUST be possible for the server to authenticate the
client.
REQ 17: It MUST be possible to use the same database of client
credentials used with SIP and SIMPLE, with the data
manipulation protocol.
REQ 18: It MUST be possible for the client to authenticate the
server.
REQ 19: It MUST be possible for message integrity to be insured
between the client and the server.
REQ 20: It MUST be possible for confidentiality to be ensured
between the client and server. As a motivating example, an
eavesdropper on the protocol could ascertain the set of
people in my presentity collection, resulting in divulging
private information.
REQ 21: It MUST be possible for the protocol to operate through
an intermediary, such as a proxy.
REQ 22: It MUST be possible to modify an entry in the presentity
collection.
REQ 23: It MUST be possible for the protocol to operate with
devices with intermittent and low bandwidth connectivity,
such as wireless data devices.
5 Authorization Policy Manipulation
The following are the set of requirements for the protocol between
the client and the server for the purposes of manipulating presence
authorization policy. The requirements are divided between acceptance
policy, notification policy, and content policy.
5.1 Acceptance Policy Requirements
REQ 1: It MUST be possible for the acceptance policy to support
rejection of the subscription if the watcher is present on
a specified list of "blocked watchers". When a list is
checked in this fashion, its referred to as a blocked list.
REQ 2: It MUST be possible for the acceptance policy to support
J. Rosenberg et. al. [Page 8]
Internet Draft Data Requirements February 23, 2003
rejection of the subscription if the watcher is not present
on a specified list of "allowed watchers".
REQ 3: It MUST be possible for the acceptance policy to support
making a subscription pending if the watcher is present on
neither an explicit allowed or blocked list. In that case,
the watcherinfo package [5] can be used for reactive
authorization.
REQ 4: It MUST be possible for the acceptance policy to check
multiple blocked and allowed lists.
REQ 5: It MUST be possible for the acceptance policy to support
rejection of the subscription based on filter information
provided in the subscription. Filter information allows the
subscriber to be informed of specific pieces of information
and receive notifications at specific points in time [6].
REQ 5.1: It MUST be possible for the policy to be based on the
status types (for example, the basic status type as defined
in PIDF [7] requested in the filter.
REQ 5.2: It MUST be possible for the policy to be based on the
status values requested in the filter.
REQ 5.3: It MUST be possible for the policy to be based on
whether the subscriber has requested, using the filter, to
receive contact addresses.
REQ 6: It SHOULD be possible for the policy to be based on the
time of day.
REQ 7: It SHOULD be possible for the policy to be based on the
means by which the authenticated identity of the watcher
was determined (digest vs. s/mime, for example).
REQ 8: It SHOULD be possible for the policy to be based on
whether notifications can be sent encrypted to the
subscriber.
REQ 9: It MUST be possible for a subscription to be accepted or
rejected based on whether the subscriber is on the
presentity's own buddy list.
REQ 10: It MUST be possible for the user to manipulate any lists
that are checked by by the authorization policy (for
example, the allowed and denied lists). Manipulate means to
add, remove, modify, read, clear and create and delete.
J. Rosenberg et. al. [Page 9]
Internet Draft Data Requirements February 23, 2003
5.2 Notification Requirements
REQ 1: It MUST be possible for the user to specify that
notifications are to be sent only when the value of a
particular status type changes.
REQ 2: It MUST be possible for the user to specify that the
notifications are to be sent only when a particular status
type changes to a specified value or set of values.
REQ 3: It MUST be possible for the user to specify that the
notifications are to be sent only when a particular status
type changes from a specified value to a specified value
(i.e., from open to closed).
REQ 4: It MUST be possible for the user to specify that the
notifications are to be sent only when the value of the
contact address changes.
REQ 5: It SHOULD be possible for the user to specify that the
notifications are not, or should be sent on changes in the
state of the subscription (as opposed to the state of the
presentity).
REQ 6: It SHOULD be possible for the user to specify that the
notifications are to be sent based on the filter policy
present in the SUBSCRIBE request. In that case, the overall
filter policy would be the composition of the requested
filter and the filters explicitly specified by the
presentity.
5.3 Content Requirements
REQ 1: It MUST be possible for the user to specify that the
notification should or should not contain a contact
address.
REQ 2: It MUST be possible for the user to specify that the
notification should contain only specific status types
(such as basic).
REQ 3: The user MUST be able to specify the specific values of a
specific status type that the notification should or should
not contain. Values not permitted must result in the
omission of that status type. If all status is omitted, the
tuple must be omitted as well. As an example, a user can
specify that the notification should include tuples with
OPEN status, but suppress those with only CLOSED status.
J. Rosenberg et. al. [Page 10]
Internet Draft Data Requirements February 23, 2003
REQ 4: The user MUST be able to specify that the notification
should only contain information for particular tuples.
REQ 5: It SHOULD be possible for the user to specify that the
notifications are to be sent based on the filter policy
present in the SUBSCRIBE request. In that case, the overall
filter policy would be the composition of the requested
filter and the filters explicitly specified by the
presentity.
REQ 6: It SHOULD be possible for the user to specify that the
value of a status should be modified for a particular
subscriber (i.e., the user wants to lie).
REQ 7: It SHOULD be possible for the user to specify the
specific presence document to send to a watcher.
REQ 8: It SHOULD be possible for the user to specify that the
notifications should be encrypted using S/MIME.
5.4 General Requirements
These requirements apply to all of the three components of the
authorization policy.
REQ 1: It MUST be possible for a client to store a cached copy
of the policies. This implies that it MUST be possible for
the server to notify the client of a change in these data.
It MUST be possible for the client to manipulate the local
cached copy even when there is no connectivity to the
server. It MUST be possible to synchronize the cached copy
with the master copy on the server, when connectivity is
re-established.
REQ 2: It MUST be possible for there to be multiple clients with
cached copies of the data.
REQ 3: Manipulations of the data MUST exhibit the ACID property;
that is, they MUST be atomic, be consistent, durable, and
operate independently.
REQ 4: It MAY be possible for the client to batch multiple
operations (add a user to a list, change the script) into a
single request that is processed atomically.
REQ 5: It MUST be possible for the server to authenticate the
client.
J. Rosenberg et. al. [Page 11]
Internet Draft Data Requirements February 23, 2003
REQ 6: It MUST be possible to use the same database of client
credentials used with SIP and SIMPLE, with the data
manipulation protocol.
REQ 7: It MUST be possible for the client to authenticate the
server.
REQ 8: It MUST be possible for message integrity to be ensured
between the client and the server.
REQ 9: It MUST be possible for confidentiality to be insured
between the client and server. As a motivating example, an
eavesdropper on the protocol could ascertain the set of
people in my allowed list collection, resulting in
divulging private information.
REQ 10: It MUST be possible for the protocol to operate through
an intermediary, such as a proxy.
REQ 11: It MUST be possible for the protocol to operate with
devices with intermittent and low bandwidth connectivity,
such as wireless data devices.
6 Security Considerations
There are many security considerations associated with the protocol
whose requirements are defined here.
The protocol is used to manipulate data that has a signficiant impact
on the operation of a service provided to a user. In particular, if
the data is manipulated by an attacker, the attacker can:
o convey information to subscribers that the presentity wishes
to keep private;
o launch denial of service attacks by flooding a subscriber with
more presence information than they expected;
o deny service to subscribers or to presentities.
To prevent these attacks, the protocol has to ensure than only
authorized users can manipulate the data. Requirements for
authentication and authorization are defined above.
Information conveyed in the protocol represents sensitive data. It
can include the content of presentity collections and lists of
blocked users, both of which reveal personal preferences of a user
that they do not wish to convey. As a result, it is necessary that
J. Rosenberg et. al. [Page 12]
Internet Draft Data Requirements February 23, 2003
the client authenticate the server, to be sure it is passing this
information to a trusted entity. It is also necessary for the
protocol to provide encryption services, so that eavesdroppers cannot
inspect the data as it passes by.
7 To Do
o Align this with the ongoing filter work
o Make sure the requirements are consistent with the final
protocol mechanism.
8 Acknowledgements
The authors would like to thank Paul Kyzivat for his input.
9 Authors Addresses
Jonathan Rosenberg
dynamicsoft
72 Eagle Rock Avenue
First Floor
East Hanover, NJ 07936
email: jdrosen@dynamicsoft.com
Markus Isomaki
Nokia
Nokia House
Keilalahti, Espoo
Finland
email: markus.isomaki@nokia.com
10 Normative References
11 Informative References
[1] M. Day, J. Rosenberg, and H. Sugano, "A model for presence and
instant messaging," RFC 2778, Internet Engineering Task Force, Feb.
2000.
[2] A. B. Roach, J. Rosenberg, and B. Campbell, "A session initiation
protocol (SIP) event notification extension for collections,"
internet draft, Internet Engineering Task Force, Feb. 2003. Work in
progress.
J. Rosenberg et. al. [Page 13]
Internet Draft Data Requirements February 23, 2003
[3] J. Rosenberg, "A presence event package for the session
initiation protocol (SIP)," internet draft, Internet Engineering Task
Force, Jan. 2003. Work in progress.
[4] D. H. Crocker and J. Peterson, "Common profile: Presence,"
internet draft, Internet Engineering Task Force, Dec. 2002. Work in
progress.
[5] J. Rosenberg, "A watcher information event template-package for
the session initiation protocol (SIP)," internet draft, Internet
Engineering Task Force, Jan. 2003. Work in progress.
[6] H. Khartabil et al. , "Event notification filtering for
presence," internet draft, Internet Engineering Task Force, Jan.
2003. Work in progress.
[7] H. Sugano, S. Fujimoto, et al. , "Common presence and instant
messaging (cpim)presence information data format," internet draft,
Internet Engineering Task Force, Jan. 2003. Work in progress.
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
Full Copyright Statement
Copyright (c) The Internet Society (2003). All Rights Reserved.
J. Rosenberg et. al. [Page 14]
Internet Draft Data Requirements February 23, 2003
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
J. Rosenberg et. al. [Page 15]