SIMPLE WG J. Rosenberg
Internet-Draft Dynamicsoft
Expires: December 26, 2003 M. Isomaki
Nokia Research Center
June 27, 2003
Requirements for Manipulation of Data Elements in Session Initiation
Protocol (SIP) for Instant Messaging and Presence Leveraging
Extensions (SIMPLE) Systems
draft-ietf-simple-data-req-03
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.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on December 26, 2003.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
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.
Rosenberg & Isomaki Expires December 26, 2003 [Page 1]
Internet-Draft Data Manipulation Requirements June 2003
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Resource List Manipulation Requirements . . . . . . . . . . . 6
6. Authorization Policy Manipulation . . . . . . . . . . . . . . 8
6.1 Acceptance Policy Requirements . . . . . . . . . . . . . . . . 8
6.2 Notification Requirements . . . . . . . . . . . . . . . . . . 9
6.3 Content Requirements . . . . . . . . . . . . . . . . . . . . . 10
6.4 General Requirements . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
9. Changes from version 02 . . . . . . . . . . . . . . . . . . . 13
Informative References . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . . 15
Rosenberg & Isomaki Expires December 26, 2003 [Page 2]
Internet-Draft Data Manipulation Requirements June 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 resource list. The resource list
is the set of presentities [2] 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 to all the presentities on the list.
Subscription to resource lists is supported through the SIP event
notification extension for resource lists [6]. 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 resource lists and authorization policies.
Further data manipulation requirements may be defined in the future,
but they are out of the scope of this document.
2. Conventions
In this document, the key words 'MUST', 'MUST NOT', 'REQUIRED',
'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',
and 'OPTIONAL' are to be interpreted as described in RFC 2119 [1]
and indicate requirement levels for compliant implementations.
3. Terminology
This document uses the following terminology:
Resource list: A resource list is a set of presentities, each of
which is identified by a URI. The list itself is identified by a
URI (for example, sip:myfriends@example.com). Using the SIP event
extension for resource lists [6], a watcher can subscribe to the
resource list and learn about the presence state of all the
Rosenberg & Isomaki Expires December 26, 2003 [Page 3]
Internet-Draft Data Manipulation Requirements June 2003
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.
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
resource lists 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.
4. Framework
The framework for the usage and manipulation of SIMPLE data elements
are shown in Figure 1.
SUBSCRIBE |--------|
------------->| |<---| //-----\\
<-------------| PA | | || ||
NOTIFY |--------| |---|\\-----//|
| |
| Storage |
| |
|->|---------|
Rosenberg & Isomaki Expires December 26, 2003 [Page 4]
Internet-Draft Data Manipulation Requirements June 2003
|--------| |
| |<----|
| Server | Read/Write
|--------|
^ |
| | RL/Auth manipulations
| v
|--------|
| |
| Client |
|--------|
Figure 1: Framework for Data Manipulation
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) manages 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 resource list, the
PA will need to determine that this is the case, and secondly,
'expand' the resource list, obtaining the list of URIs for that
resource list.
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
server before reading the data.
Between the resource list 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
Rosenberg & Isomaki Expires December 26, 2003 [Page 5]
Internet-Draft Data Manipulation Requirements June 2003
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.
5. Resource List Manipulation Requirements
The following are the set of requirements for the protocol between
the client and the server for the purposes of manipulation resource
lists. It is obvious that similar requirements would apply to lists
used by other applications than presence as well, but those are
outside the scope of this document.
REQ PC-1: It MUST be possible for the client to create resource
lists and associate each of them with a distinct URI.
REQ PC-2: It MUST be possible for the user to specify the URI for
the resource list 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 PC-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 PC-4: It MUST be possible to associate a display name with a
resource list.
REQ PC-5: It MUST be possible to add an entry to the resource list.
Each entry MUST be able to include at least a URI, and a display
name. It MUST be possible for the entry to be any URI that is
meaningful in the context of a resource list. Examples would
include a SIP URI or pres URI [7].
REQ PC-6: It MUST be possible to extend the set of information
associated with the entries in the resource list and with the list
itself. An example would be a filtering document associated with
the list.
Rosenberg & Isomaki Expires December 26, 2003 [Page 6]
Internet-Draft Data Manipulation Requirements June 2003
REQ PC-7: It MUST be possible for a resource list to contain entries
which are themselves resource lists.
REQ PC-8: It MUST be possible to remove an entry from the resource
list. If the entry does not exist, it MUST be possible for the
server to inform the client of this fact.
REQ PC-9: It MUST be possible to modify an entry in the resource
list.
REQ PC-10: It MUST be possible to clear all entries from a resource
list.
REQ PC-11: It MUST be possible to query for the set of URIs and
other possible information related to a particular resource list
by providing the URI for the resource list.
REQ PC-12: It MUST be possible to delete a resource list. In this
context, deleted means that the name of the resource list is no
longer defined, so that subscriptions to the list would fail.
REQ PC-13: It MUST be possible for a user to retrieve the list of
resource lists that they have created.
REQ PC-14: It MUST be possible for the resource list to be
associated with a list of authorized users who are able to query
for the set of URIs and other possible information related to the
list.
REQ PC-15: It MUST be possible for the resource list to be
associated with a list of authorized users who are the only ones
permitted to manipulate the resource list.
REQ PC-16: It MUST be possible for the resource list to be
associated with a list of authorized users who are authorized to
subscribe to the list.
REQ PC-17: It MUST be possible for a client to store a cached copy
of 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 on the 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.
Rosenberg & Isomaki Expires December 26, 2003 [Page 7]
Internet-Draft Data Manipulation Requirements June 2003
REQ PC-18: It MUST be possible multiple clients to manipulate a
resource list without knowing of each other's actions. This
implies that it MUST be possible for the server to notify each
client of the changes if the client has indicated the need for the
change notifications.
REQ PC-19: Manipulations of the resource list MUST exhibit the ACID
property; that is, they MUST be atomic, be consistent, durable,
and operate independently.
REQ PC-20: It SHOULD be possible for the client to batch multiple
operations (add a presentity, remove a presentity) into a single
request that is processed atomically.
REQ PC-21: It MUST be possible for the server to authenticate the
client.
REQ PC-22: It SHOULD be possible to use the same database of client
credentials used with SIP and SIMPLE, with the data manipulation
protocol.
REQ PC-23: It MUST be possible for the client to authenticate the
server.
REQ PC-24: It MUST be possible for message integrity to be insured
between the client and the server.
REQ PC-25: 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 resource list, resulting in divulging private information.
REQ PC-26: It MUST be possible for the protocol to operate through
an intermediary, such as a proxy, to allow easier firewall
traversal.
6. 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. It is obvious that
these requirements would apply to other SIP event packages than
presence as well, but those are outside the scope of this document.
6.1 Acceptance Policy Requirements
Rosenberg & Isomaki Expires December 26, 2003 [Page 8]
Internet-Draft Data Manipulation Requirements June 2003
REQ AP-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, it is referred to as a blocked list.
REQ AP-2: It MUST be possible for the acceptance policy to support
rejection of the subscription if the watcher is not present on a
specified list of 'allowed watchers'.
REQ AP-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 watcher
info package [5] can be used for reactive authorization.
REQ AP-4: It MUST be possible for the acceptance policy to check
multiple blocked and allowed lists.
REQ AP-5: 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 AP-6: It SHOULD be possible for the policy to be based on
whether notifications can be sent encrypted to the subscriber.
REQ AP-7: It MUST be possible for authorized users to create, read,
modify and delete lists that are checked by the authorization
policy (e.g., the allowed and blocked lists).
REQ AP-8: It MUST be possible for authorized users to read, add,
remove and modify entries of the lists.
REQ AP-9: It MUST be possible for the lists to contain entries with
wildcards, e.g., allow everyone in a certain domain.
6.2 Notification Requirements
REQ N-1: It SHOULD be possible for the user to specify that
notifications are to be sent only when the value of a particular
status type changes.
REQ N-2: It SHOULD 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 N-3: It SHOULD 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 (e.g., from
Rosenberg & Isomaki Expires December 26, 2003 [Page 9]
Internet-Draft Data Manipulation Requirements June 2003
open to closed).
REQ N-4: It SHOULD be possible for the user to specify that the
notifications are to be sent only when the value of the contact
address changes.
REQ N-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).
6.3 Content Requirements
REQ C-1: The user MUST be able to specify that the notification
should only contain information for particular tuples. It SHOULD
be possible to use any presence attribute within a tuple as
criteria for this selection.
REQ C-2: It MUST be possible for the user to specify that the
notification should or should not contain a contact address.
REQ C-3: It MUST be possible for the user to specify that the
notification should contain only specific status types (such as
basic).
REQ C-4: 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.
REQ C-5: It MUST be possible for the user to specify different
values of the semantically identical presence information, such as
status attribute, to different watchers. It MUST be possible for
the user to give different level of detail of information to
different watchers.
The assumption is that the presentity also publishes the different
values separately (e.g. in separate tuples), so that the
authorization rules can simply select which (level of) information
to give to each watcher.
REQ C-6: It SHOULD be possible for the user to specify the specific
presence document to send to a watcher.
Rosenberg & Isomaki Expires December 26, 2003 [Page 10]
Internet-Draft Data Manipulation Requirements June 2003
REQ C-7: It SHOULD be possible for the user to specify that the
notifications should be encrypted using S/MIME.
REQ C-8: It SHOULD be possible for the user to specify that a
particular tuple be added, removed or modified based on the value
of another tuple. As an example, a user might want to include
their IM tuple when their phone is busy, but not include it when
the phone is not busy.
6.4 General Requirements
These requirements apply to all of the three components of the
authorization policy.
REQ G-1: It MUST be possible for a client to store a cached copy of
the policies. 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 G-2: It MUST be possible for multiple clients to manipulate the
same policies without knowing of each others' actions. This
implies that it MUST be possible for the server to notify each
client of the changes if the client has indicated the need for the
change notifications.
REQ G-3: Manipulations of the data MUST exhibit the ACID property;
that is, they MUST be atomic, be consistent, durable, and operate
independently.
REQ G-4: It MUST be possible to ensure that the authorization
policies are always consistent as a whole when transitioning from
one policy state to another. To enable this, it MUST be possible
for the client to batch multiple operations (remove a user from
one list, add the same user to another list) into a single request
that is processed atomically, or to otherwise ensure that the
policies are never left in an inconsistent state.
REQ G-5: It MUST be possible for the server to authenticate the
client.
REQ G-6: It SHOULD be possible to use the same database of client
credentials used with SIP and SIMPLE, with the data manipulation
protocol.
Rosenberg & Isomaki Expires December 26, 2003 [Page 11]
Internet-Draft Data Manipulation Requirements June 2003
REQ G-7: It MUST be possible for the client to authenticate the
server.
REQ G-8: It MUST be possible for message integrity to be ensured
between the client and the server.
REQ G-9: 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 allowed list, resulting in divulging private information.
REQ G-10: It MUST be possible to extend the authorization policies
with new types of rules.
REQ G-11: It MUST be possible for a client to discover the types of
authorization policies the server can handle.
7. 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 significant impact
on the operation of a service provided to a user. In particular, if
an attacker manipulates the data, 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 resource lists 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 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.
Rosenberg & Isomaki Expires December 26, 2003 [Page 12]
Internet-Draft Data Manipulation Requirements June 2003
8. Acknowledgements
The authors would like to thank Paul Kyzivat, Ben Campbell, Krisztian
Kiss and Eva Leppanen for their input.
9. Changes from version 02
o Conventions chapter added.
o To-Do list removed.
o Presentity collection renamed resource list.
o Ordering of requirements 'rationalized'.
o References updated.
o Defined the scope to be explicitly limited to only resource list
and presence authorization policy requirements.
o Several requirements modified based on SIMPLE WG last call
comments by Ben Campbell and Krisztian Kiss.
Informative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Day, M., "A model for presence and instant messaging", RFC 2778,
February 2000.
[3] Rosenberg, J., "Session Initiation Protocol (SIP) Extensions for
Presence", draft-ietf-simple-presence-10.txt, January 2003.
[4] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[5] Rosenberg, J., "A Watcher Information Event Template-Package for
the Session Initiation Protocol (SIP)",
draft-ietf-simple-winfo-package-05.txt, January 2003.
[6] Rosenberg, J., "A Session Initiation Protocol (SIP) Event
Notification Extension for Resource Lists",
draft-ietf-simple-event-list-03.txt, May 2003.
[7] Peterson, J., "Common profile for presence (CPP)",
draft-ietf-impp-pres-03.txt, May 2003.
Rosenberg & Isomaki Expires December 26, 2003 [Page 13]
Internet-Draft Data Manipulation Requirements June 2003
Authors' Addresses
Jonathan Rosenberg
Dynamicsoft
72 Eagle Rock Avenue
First Floor
East Hanover, NJ 07936
USA
Phone:
EMail: jdrosen@dynamicsoft.com
Markus Isomaki
Nokia Research Center
Itamerenkatu 11-13
00180 Helsinki
Finland
Phone:
EMail: markus.isomaki@nokia.com
Rosenberg & Isomaki Expires December 26, 2003 [Page 14]
Internet-Draft Data Manipulation Requirements June 2003
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.
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 assignees.
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
Rosenberg & Isomaki Expires December 26, 2003 [Page 15]
Internet-Draft Data Manipulation Requirements June 2003
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Rosenberg & Isomaki Expires December 26, 2003 [Page 16]
