Network Working Group A. B. Roach
Internet-Draft J. Rosenberg
Expires: September 26, 2003 B. Campbell
dynamicsoft
March 28, 2003
A Session Initiation Protocol (SIP) Event Notification Extension for
Collections
draft-ietf-simple-event-list-01
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document presents an extension to the Session Initiation
Protocol (SIP)-Specific Event Notification mechanism for subscribing
to a homogenous collection of event packages. Instead of the
subscriber sending a SUBSCRIBE for each resource individually, the
subscriber can subscribe to an entire collection, and then receive
notifications when the state of any of the resources in the
collection changes.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of Operation . . . . . . . . . . . . . . . . . . . . 4
3. Operation of List Subscriptions . . . . . . . . . . . . . . . 5
3.1 Negotiation of Support for Resource Lists . . . . . . . . . . 5
3.2 Subscription Duration . . . . . . . . . . . . . . . . . . . . 6
3.3 NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . . . 6
3.4 Notifier Processing of SUBSCRIBE Requests . . . . . . . . . . 6
3.5 Notifier Generation of NOTIFY requests . . . . . . . . . . . . 6
3.6 Subscriber Processing of NOTIFY Requests . . . . . . . . . . . 8
3.7 Handling of Forked Requests . . . . . . . . . . . . . . . . . 8
3.8 Rate of Notifications . . . . . . . . . . . . . . . . . . . . 9
3.9 State Agents . . . . . . . . . . . . . . . . . . . . . . . . . 9
4. Using multipart/related to Convey Aggregate State . . . . . . 10
4.1 XML Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2 List Attributes . . . . . . . . . . . . . . . . . . . . . . . 11
4.3 Resource Attributes . . . . . . . . . . . . . . . . . . . . . 12
4.4 Instance Attributes . . . . . . . . . . . . . . . . . . . . . 12
4.5 Constructing Coherent Resource State . . . . . . . . . . . . . 13
5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6. Security Considerations . . . . . . . . . . . . . . . . . . . 28
6.1 Authentication . . . . . . . . . . . . . . . . . . . . . . . . 28
6.2 Risks of Improper Aggregation . . . . . . . . . . . . . . . . 28
6.3 Signing and Sealing . . . . . . . . . . . . . . . . . . . . . 29
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
7.1 New SIP Option Tag: eventlist . . . . . . . . . . . . . . . . 30
7.2 New MIME type for Resource List Meta-Information . . . . . . . 30
7.3 URN Sub-Namespace . . . . . . . . . . . . . . . . . . . . . . 31
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 33
Normative References . . . . . . . . . . . . . . . . . . . . . 34
Non-Normative References . . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 35
A. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
A.1 Changes since -00 . . . . . . . . . . . . . . . . . . . . . . 37
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 38
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1. Introduction
The SIP-specific event notification mechanism [2] allows a user (the
subscriber) to request to be notified of changes in the state of a
particular resource. This is accomplished by having the subscriber
generate a SUBSCRIBE request for the resource, which is processed by
a notifier that represents the resource. In many cases, a subscriber
has a collection of resources they are interested in.
For environments in which bandwidth is limited, such as wireless
networks, subscribing to each resource individually is problematic.
Some specific problems are:
o Doing so generates substantial message traffic, in the form of the
initial SUBSCRIBE requests for each resource, and the refreshes of
each individual subscription.
o The notifier may insist on low refresh intervals, in order to
avoid long lived subscription state. This means that the
subscriber may need to generate subscriptions faster than it would
like to, or has the capacity to.
o The notifier may generate NOTIFY requests more rapidly than the
subscriber desires, causing NOTIFY traffic at a greater volume
than is desired by the subscriber.
To solve these problems, this specification defines an extension that
allows for requesting and conveying notifications for collections of
resources. A resource list is identified by a URI and it represents
a list of zero or more URIs. Each of these URIs is an identifier for
an individual resource for which the subscriber wants to receive
information. In many cases, the URI will be a SIP URI [1]; however,
the use of other schemes (such as pres:) is also forseen.
The notifier for the collection is called a "resource list server",
or RLS. In order to determine the state of the entire list, the RLS
will act as if it has typically generated a subscription to each
resource in the list.
The resource list is not restricted to be inside the domain of the
subscriber. Similarly, the resources in the list are not
contstrained to be in the domain of the resource list server.
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2. Overview of Operation
This section provides an overview of the typical mode of operation of
this extension. It is not normative.
When a user wishes to subscribe to the resource of a list of
resources, they create a resource list. This resource list is
represented by a SIP URI. The list contains a set of URIs, each of
which represents a resource for which the subscriber wants to receive
information. The resource list can exist in any domain. Typically,
the user who creates the list (and subsequently subscribes to it)
will have a trust relationship with the domain that hosts the list.
The list could be manipulated through a web page, through a voice
response system, or through some other protocol. The specific means
by which the list is created and maintained is outside of the scope
of this specification.
To learn the resource state of the set of elements on the list, the
user sends a single SUBSCRIBE request targeted to the URI of the
list. This will be routed to an RLS for that URI. The RLS acts as a
notifier, authenticates the subscriber, and accepts the subscription.
The RLS may have direct information about some or all of the
resources specified by the list. If it does not, it could subscribe
to any non-local resources specified by the list resource.
Note that subscriptions to non-local resources may or may not be SIP
subscriptions; any mechanism for determining such information may be
employed. This document uses the term "back-end subscription" to
refer to such a subscription, regardless of whether SIP is used to
establish and service them.
As the state of resources in the list change, the RLS generates
notifications to the list subscribers. The RLS can, at its
discretion, buffer notifications of resource changes, and send the
resource information to the subscriber in batches, rather than
individually. This allows the RLS to provide rate limiting for the
subscriber.
The list notifications contain a body of type multipart/related. The
root section of the multipart/related content is an XML document that
provides meta-information about each resource present in the list.
The remaining sections contain the actual state information for each
resource.
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3. Operation of List Subscriptions
A list subscription acts, in many ways, like an event template
package. In particular, any single list subscription MUST be
homogenous with respect to the underlying event package. In other
words, a single list subscription cannot contain subscriptions to
different kinds of event packages.
The key difference between a list subscription and templates in
general is that support for list subscriptions indicates support for
arbitrary nesting of list subscriptions. In other words, elements
within the list may be atomic elements, or they may be lists
themselves.
The consequence of this is that subscription to a URI that represents
a list actually results in a virtual subscription to a tree of
resources. The leaf nodes of this tree are virtual subscriptions of
the event type given in the "Event" header; all other nodes in the
tree are list subscriptions that are serviced as described in this
section and its subsections.
It is important to keep in mind that these virtual subscriptions are
not literal SIP subscriptions (although they may result in SIP
subscriptions, depending on the RLS implementation).
3.1 Negotiation of Support for Resource Lists
This specification uses the SIP option tag mechanism for negotiating
support of the extension defined herein. Refer to RFC3261 [1] for
the normative description of processing of the "Supported" and
"Require" headers and the 421 (Extension Required) response code.
Any client that supports the event list extension will include an
option tag of "eventlist" in a "Supported" header of every SUBSCRIBE
message for a subscription for which it is willing to process a list.
If the subscription is made to a URI that represents a list, the RLS
will include "eventlist" in a "Require" header of the response to the
SUBSCRIBE, and in all NOTIFY messages within that subscription. Note
that including "eventlist" in a "Require" header in a SUBSCRIBE
request serves no purpose, and is consequently NOT RECOMMENDED.
As described in RFC3265 [2], a subscription to a particular state of
a resource is identified by the Request-URI and the event package
used. Because it is quite reasonable for an RLS to contain a
resource that is inherently a list (e.g.
"sip:buddylist@example.com"), it is perfectly reasonable to expect
that RLSes will return a 421 (Extension Required) response code if
the "eventlist" option tag is not indicated in a request to subscribe
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to that resource. Because of the forgoing situation, this
specification relaxes the "NOT RECOMMENED" provision described in
RFC3261 [1], section 8.2.4 for the extension described herein.
3.2 Subscription Duration
Since the primary benefit of the resource list server is to reduce
the overall messaging volume to a handset, it is RECOMMENDED that the
subscription duration to a list be reasonably long. The default,
when no duration is specified, is taken from the underlying event
package. Of course, the standard techniques [2] can be used to
increase or reduce this amount.
3.3 NOTIFY Bodies
An implementation compliant to this specification MUST support the
multipart/related and application/rlmi+xml MIME types. These types
MUST be included in an Accept header sent in SUBSCRIBE message, in
addition to any other types supported by the client.
3.4 Notifier Processing of SUBSCRIBE Requests
All subscriptions for resource lists SHOULD be authenticated. The
use of the SIP HTTP Digest mechanism [1] over TLS is RECOMMENDED.
Once the subscriber is authenticated, the RLS performs authorization
per its local policy. In many cases, each resource list is
associated with a particular user (the one who created it and manages
the set of elements in it), and only that user will be allowed to
subscribe. Of course, this mode of operation is not inherent in the
use of resource lists, and a notifier can use any authorization
policy it chooses.
3.5 Notifier Generation of NOTIFY requests
This specification leaves the choice about how and when to generate
NOTIFY requests at the discretion of the implementor. One of the
value propositions of the RLS is the means by which it aggregates,
rate limits, or optimizes the way in which notifications are
generated. As a baseline behavior, the RLS MAY generate a NOTIFY to
the RLS subscriber whenever the state of any resource on the list
changes.
See Section 4 for a detailed definition of the syntax used to convey
resource lists. For the purposes of the following discussion, it is
important to know that the overall list contains one or more
resources, and that the resources contains one or more instances of
the resource. Each instance of the resource has a state associated
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with it (pending, active, or terminating), representing the state of
the subscription.
Notifications contain a multipart document, the first part of which
always contains meta-information about the list (e.g. membership,
state of the virtual subscription to the resource). Remaining parts
are used to convey the actual state of the resources listed in the
meta-information.
The "state" attribute of each instance of a resource in the meta-
information is set according to the state of the virtual
subscription. The meanings of the "state" attribute are described in
RFC 3265 [2].
If an instance of a resource was previously reported to the
subscriber but is no longer available (i.e. the virtual subscription
to that instance has been terminated), the resource list server
SHOULD include that resource instance in the meta-information in the
first NOTIFY message sent to the subscriber following the instance's
unavailability. The RLS MAY continue to do so for future
notifications.
When sending information for a terminated resource instance, the RLS
indicates a state of "terminated" and an appropriate reason value.
Valid reason values and their meanings are described in RFC 3265 [2].
If the RLS will attempt to recover the resource state again at some
point in the future (e.g. when the reason in the meta-informaion is
"probation"), then the instance of the resource SHOULD remain in the
meta-information until the instance state is available, or until the
RLS gives up on making such state available.
When the first SUBSCRIBE message for a particular subscription is
received by a resource list notifier, the notifier will often not
know state information for all of the resources specified by the
resource list. For any resource for which state information is not
known, the corresponding "uri" attribute will be set appropriately,
and no <instance> elements will be present for the resource.
For an initial notification, sections corresponding to resources for
which the resource list notifier does have state will be populated
with appropriate data (subject, of course, to local policy
decisions). This will often occur if the resource list server is
colocated with the server for one or more of the resources specified
on the list.
Immediate notifications triggered as a result of subsequent SUBSCRIBE
messages SHOULD result in full meta-information about the list of
resources. The RLS SHOULD also include state information for all
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resources in the list for which the RLS has state, subject to policy
restrictions. This allows the subscriber to refresh their state, and
to recover from lost notifications.
Note that a consequence of the way in which resource list
subscriptions work, polling of resource state will often not be
particularly useful. While such polls will retrieve the resource
list (and potentially even some of the states if a resource on the
list is colocated with the resource list server), they will often not
contain state for some or all of the resources on the list.
3.6 Subscriber Processing of NOTIFY Requests
Notifications for a resource list can convey information about a
subset of the list elements. This means that an explicit algorithm
needs to be defined in order to construct coherent and consistent
state.
The XML document present in the root of the multipart/related
document contains a <resource> element for each resource in the list.
Each <resource> element contains a URI which uniquely identifies the
resource to which that section corresponds. When a NOTIFY arrives,
it can contain full or partial state (as indicate by the "fullState"
attribute of the top-level <list> element). If full state is
indicated, then the recipient replaces all state associated with the
list with the entities in the NOTIFY body. If full state is not
indicated, the recipient of the NOTIFY updates information for each
identified resource. Information for any resources that are not
identified in the NOTIFY are not changed, even if they were indicated
in previous NOTIFY mesages. See section Section 4.5 for more
information.
Note that the underlying event package may have its own rules for
compositing partial state notification. When processing data related
to those packages, their rules apply (i.e. the fact that they were
reported as part of a collection does not change their partial
notification semantics).
3.7 Handling of Forked Requests
Forking makes little sense with subscriptions to event lists, since
the whole idea is a centralization of the source of notifications.
Therefore, a subscriber MUST create just a single dialog as a result
of a single subscription request, using the techniques described in
RFC 3265[2].
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3.8 Rate of Notifications
One potential role of the RLS is to perform rate limitations on
behalf of the subscriber. As such, this specification does not
mandate any particular rate limitation, and rather leaves that to the
discretion of the implementation.
3.9 State Agents
Effectively, a resource list server is nothing more than a state
agent for the resource event type.
The usage of an RLS does introduce some security considerations. The
end user is no longer the direct subscriber to the state of the
resource. If the notifier for the resource demands end-to-end
authentication, the RLS will need to be provided appropriate
credentials to access those resources (e.g. shared secrets for
Digest authentication). This requires a certain level of trust
between the user and their RLS. This specification does not describe
any particular means of providing such credentials to the RLS (such
as uploading a shared secret). However, any such upload mechanism
MUST ensure privacy of the key data; using HTTPS to fill out a form
is a reasonable method.
If the notifier for the resource is using a transitive trust model to
validate the subscriber, then this works well with the RLS concept.
The RLS would authenticate the subscriber, and then MAY use the SIP
extensions for network asserted identity (see [6] and [7]) to provide
an authenticated identity to any downstream servers. It is even
conceivable that the subscriber may provide an authenticated ID in
its original subscribe request for use by the RLS for the dual
purpose of local authentication and use in any generated SUBSCRIBE
messages.
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4. Using multipart/related to Convey Aggregate State
In order to convey the state of multiple resources, the list template
package uses the "multipart/related" mime type. The syntax for
multipart/related is defined in "The MIME Multipart/Related Content-
type" [4].
4.1 XML Syntax
The root document of the multipart/related body is always a Resource
List Meta-Information (RLMI) document. It is of type "application/
rlmi+xml". This document containes the meta-information for the
resources contained in the notification. The schema for this XML
document is given below.
<?xml version="1.0" encoding="UTF-8" ?>
<xs:schema targetNamespace="urn:ietf:params:xml:ns:rlmi"
elementFormDefault="qualified"
xmlns="urn:ietf:params:xml:ns:rlmi"
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="list">
<xs:complexType>
<xs:sequence>
<xs:element ref="resource" minOccurs="0" maxOccurs="unbounded" />
</xs:sequence>
<xs:attribute name="uri" type="xs:anyURI" use="required" />
<xs:attribute name="version" type="xs:unsignedInt" use="required" />
<xs:attribute name="fullState" type="xs:boolean" use="required" />
<xs:attribute name="name" type="xs:string" use="optional" />
<xs:attribute name="cid" type="xs:string use="optional" />
<xs:anyAttribute />
</xs:complexType>
</xs:element>
<xs:element name="resource">
<xs:complexType>
<xs:sequence>
<xs:element ref="instance" minOccurs="0" maxOccurs="unbounded" />
</xs:sequence>
<xs:attribute name="uri" type="xs:anyURI" use="required" />
<xs:attribute name="name" type="xs:string" use="optional" />
<xs:anyAttribute />
</xs:complexType>
</xs:element>
<xs:element name="instance">
<xs:complexType>
<xs:sequence>
<xs:any minOccurs="0" maxOccurs="unbounded" />
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</xs:sequence>
<xs:attribute name="id" type="xs:string use="required" />
<xs:attribute name="state" type="xs:string" use="required" />
<xs:attribute name="reason" type="xs:string" use="optional" />
<xs:attribute name="cid" type="xs:string use="optional" />
<xs:anyAttribute />
</xs:complexType>
</xs:element>
</xs:schema>
An example of a document formatted using this schema follows.
<list uri="sip:adam-friends@lists.example.com" version="7"
name="Buddy List" fullState="true">
<resource uri="sip:bob@example.com" name="Bob Smith">
<instance id="juwigmtboe" state="active" cid="12345.aaa@example.com"/>
</resource>
<resource uri="sip:dave@example.com" name="Dave Jones">
<instance id="hqzsuxtfyq" state="active" cid="12345.aab@example.com"/>
</resource>
<resource uri="sip:jim@example.com" name="Jim">
<instance id="oflzxqzuvg" state="terminated" reason="rejected" />
</resource>
<resource uri="sip:ed@example.com" name="Ed">
<instance id="grqhzsppxb" state="pending"/>
</resource>
</list>
4.2 List Attributes
The <list> element present in a list notification MUST contain three
attributes.
The first mandatory <list> attribute is "uri", which contains the uri
that corresponds to the list. Typically, this is the URI to which
the SUBSCRIBE request was sent.
The second mandatory <list> attribute is "version", which contains a
number from 0 to 2^32-1. This version number MUST be 0 for the first
NOTIFY message sent within a subscription (typically in response to a
SUBSCRIBE request), and MUST increase by exactly one for each
subsequent NOTIFY sent within a subscription.
The third mandatory attribute is "fullState". The "fullState"
attribute indicates whether the NOTIFY message contains information
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for every resource in the collection. If it does, the value of the
attribute is "true" (or "1"); otherwise, it is "false" (or "0").
Note that the first NOTIFY sent in a subscription MUST contain full
state, as must the first NOTIFY sent after receipt of a SUBSCRIBE
request for the subscription.
The optional "name" attribute can contain a human readable
description or name for the resource list. This attribute is
somewhat analogous to the "Display Name" present in the SIP name-addr
element.
Finally, <list> elements may contain a "cid" attribute. If present,
the "cid" attribute identifies a section within the multipart/related
body that contains aggregate state information for the resources
contained in the list. The definition of such aggregate information
is outside the scope of this document, and will be defined on a per-
package basis as needed. The cid attribute is the Content-ID for the
corresponding section in the multipart body.
4.3 Resource Attributes
The resource list contains one <resource> element for each resource
being reported in the notification. These resource elements contain
attributes that identify meta-data assocated with each resource.
The "uri" attribute identifies the resource to which the <resource>
element corresponds. Typically, this will be a SIP URI which, if
subscribed to, would return the state of the resource. This
attribute must be present.
The optional "name" attribute can contain a human readable
description or name for the resource. This attribute is somewhat
analogous to the "Display Name" present in the SIP name-addr element.
4.4 Instance Attributes
Each resource element contains one or more instance elements. These
instance elements are used to represent a single notifier for the
resource. For event packages that allow forking, multiple virtual
subscriptions may exist for a given resource. Multiple virtual
subscriptions are represented as multiple instance elements in the
corresponding resource element. For subscriptions in which forking
does not occur, at most one instance will be present for a given
resource.
The "id" attribute contains an opaque string used to uniquely
identify the instance of the resource. The "id" attribute is unique
only within the context of a resource. Composition of this string is
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an implementation decision. Any mechanism for generating this string
is valid, as long as uniqueness within the resource is assured.
The "state" attribute contains the subscription state for the
identified instance of the resource. This attribute contains one of
the values "active", "pending", or "terminated". The meanings for
these values are as defined for the "Subscription-State" header in
RFC 3265 [2].
If the "state" attribute indicates "terminated", then a "reason"
attribute MUST also be present. This "reason" attribute has the same
values and meanings as given for the "reason" parameter on the
"Subscription-State" header in RFC 3265 [2]. Note that the reason is
included for informational purposes; the list subscriber is not
expected to take any automated actions based on the reason value.
Finally, the "cid" attribute, which must be present if the "state"
attribute is "active", identifies the section within the multipart/
related body that contains the actual resource state. This state is
expressed in the content type defined by the event package for
conveying state. The cid attribute is the Content-ID for the
corresponding section in the multipart body.
Note that the subscription durations of any back-end subscriptions
are not propagated into the meta-information state in any way.
4.5 Constructing Coherent Resource State
The resource list subscriber maintains a table for each resource
list. The table contains a row for each resource in the resource
list. Each row is indexed by the URI for that resource. That URI is
obtained from the "uri" attribute on each <resource> element. The
contents of each row contain the state of that resource as conveyed
in the resource document.
For resources that provide versioning information (which is mandated
by [2] for any formats that allow partial notification), each row
also contains a resource state version number. The version number of
the row is initialized with the version specified in the first
document received, as defined by the corrsponding event package.
This value is used when comparing versions of partial notifications
for a resource.
The processing of the resource list notification depends on whether
it contains full or partial state. If it contains full state,
indicated by the value of the <list> attribute "fullState", the
contents of the resource-list table are flushed. They are
repopulated from the document. A new row in the table is created for
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each "resource" element.
First, a check is made to ensure that no list notifications have been
lost. The value of the local version number (the "version" attribute
of the <list> element) is compared to the version number of the new
document.
o If the value in the new document is exactly one higher than the
local version number, the local version number is increased by
one, and the document is processed, as described below.
o If the version in the document is more than one higher than the
local version number, the local version number is set to the value
in the new document, and the document is processed as described
below. Further, if the notification does not contain full state
(as indicated by the "fullState" attribute of the <list> element),
the list subscriber SHOULD generate a refresh request to trigger a
full state notification.
o If the version in the document is less than or equal to the local
version, the document is discarded without any further processing.
If the resource list document contains partial state, the
notification is used to update the table. For each resource listed
in the document, the subscriber checks to see whether a row exists
for that resource. This check is done by comparing the Resource-URI
value with the URI associated with the row. If the resource doesn't
exist in the table, a row is added, and its state is set to the
information from that "resource" element. If the resource does
exist, its state is updated to be the information from that
"resource" element, as described in the definition of the event
package. If a row is updated or created such that its state is now
"terminated," that entry MAY be removed from the table at any time.
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5. Example
This section gives an example callflow. It is not normative. If a
conflict arises between this callflow and the normative behavior
described in this or any other document, the normative descriptions
are to be followed.
In this particular example, we request a subscription to a nested
presence list. The subscriber's address-of-record is
"sip:adam@example.com", and the name of the nested list resource that
we are subscribing to is called "sip:adam-buddies@pres.example.com".
The underlying event package is "presence", described by [5].
In this example, the RLS has information to service some of the
resources on the list, but must consult other servers to retrive
information for others. The implementation of the RLS in this
example uses the SIP SUBSCRIBE/NOTIFY mechanism to retrieve such
information.
1. We initate the subscription by sending a SUBSCRIBE message to
our local RLS. (There is no reason that the RLS we contact has
to be in our domain, of course). Note that we must advertise
support for application/rlmi+xml and multipart/related because
we support the eventlist extension, and we must advertise
application/cpim-pidf+xml because we are requesting a
subscription to a list.
Terminal -> Local RLS
SUBSCRIBE sip:adam-buddies@pres.example.com SIP/2.0
Via: SIP/2.0/TCP terminal.example.com;branch=z9hG4bKwYb6QREiCL
Max-Forwards: 70
To: <sip:adam-buddies@pres.example.com>
From: <sip:adam@example.com>;tag=ie4hbb8t
Call-ID: cdB34qLToC@terminal.example.com
CSeq: 322723822 SUBSCRIBE
Contact: <sip:terminal.example.com>
Event: presence
Expires: 7200
Supported: eventlist
Accept: application/cpim-pidf+xml
Accept: application/rlmi+xml
Accept: multipart/related
Accept: multipart/signed
Accept: multipart/encrypted
Content-Length: 0
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2. The Local RLS completes the SUBSCRIBE transaction. Note that
authentication and authorization would normally take place at
this point in the callflow. Those steps are omitted for
brevity.
Local RLS -> Terminal
SIP/2.0 200 OK
Via: SIP/2.0/TCP terminal.example.com;branch=z9hG4bKwYb6QREiCL
To: <sip:adam-buddies@pres.example.com>;tag=zpNctbZq
From: <sip:adam@example.com>;tag=ie4hbb8t
Call-ID: cdB34qLToC@terminal.example.com
CSeq: 322723822 SUBSCRIBE
Contact: <sip:pres.example.com>
Expires: 7200
Require: eventlist
Content-Length: 0
3. As is required by RFC 3265 [2], the RLS sends a NOTIFY
immediately upon accepting the subscription. In this example,
we are asserting that the local RLS is also an authority for
presence information for the users in the "example.com" domain.
The NOTIFY contains an RLMI document describing the entire buddy
list (initial notifies require full state), as well as presence
information for the users about which it already knows. Note
that, since the RLS has not yet retrieved information for some
of the entries on the list, those <resource> elements contain no
<instance> elements.
Local RLS -> Terminal
NOTIFY sip:terminal.example.com SIP/2.0
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bKMgRenTETmm
Max-Forwards: 70
From: <sip:adam-buddies@pres.example.com>;tag=zpNctbZq
To: <sip:adam@example.com>;tag=ie4hbb8t
Call-ID: cdB34qLToC@terminal.example.com
CSeq: 997935768 NOTIFY
Contact: <sip:pres.example.com>
Event: presence
Subscription-State: active;expires=7200
Require: eventlist
Content-Type: multipart/related;type="application/rlmi+xml";
start="<nXYxAE@pres.example.com>";boundary="50UBfW7LSCVLtggUPe5z"
Content-Length: 1560
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--50UBfW7LSCVLtggUPe5z
Content-Transfer-Encoding: 8bit
Content-ID: <nXYxAE@pres.example.com>
Content-Type: application/rlmi+xml;charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
<list uri="sip:adam-friends@pres.example.com" version="1"
name="Buddy List at COM" fullState="true">
<resource uri="sip:bob@example.com" name="Bob Smith">
<instance id="juwigmtboe" state="active" cid="bUZBsM@pres.example.com"/>
</resource>
<resource uri="sip:dave@example.com" name="Dave Jones">
<instance id="hqzsuxtfyq" state="active" cid="ZvSvkz@pres.example.com"/>
</resource>
<resource uri="sip:ed@example.net" name="Ed at NET" />
<resource uri="sip:adam-friends@example.org" name="My Friends at ORG" />
</list>
--50UBfW7LSCVLtggUPe5z
Content-Transfer-Encoding: 8bit
Content-ID: <bUZBsM@pres.example.com>
Content-Type: application/cpim-pidf+xml;charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
entity="sip:bob@example.com">
<tuple id="sg89ae">
<status>
<basic>open</basic>
</status>
<contact priority="1.0">sip:bob@example.com</contact>
</tuple>
</presence>
--50UBfW7LSCVLtggUPe5z
Content-Transfer-Encoding: 8bit
Content-ID: <ZvSvkz@pres.example.com>
Content-Type: application/cpim-pidf+xml;charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
entity="sip:dave@example.com">
<tuple id="slie74">
<status>
<basic>closed</basic>
</status>
</tuple>
</presence>
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--50UBfW7LSCVLtggUPe5z--
4. The terminal completes the transaction.
Terminal -> Local RLS
SIP/2.0 200 OK
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bKMgRenTETmm
From: <sip:adam-buddies@pres.example.com>;tag=zpNctbZq
To: <sip:adam@example.com>;tag=ie4hbb8t
Call-ID: cdB34qLToC@terminal.example.com
CSeq: 997935768 NOTIFY
Contact: <sip:terminal.example.com>
Content-Length: 0
5. In order to service the subscription, the local RLS subscribes
to the state of the resources. In this step, the RLS attempts
to subscribe to the presence state of the resource
"sip:ed@example.com". Since the local RLS knows how to receive
notifications for list subscriptions, it includes the
"Supported: eventlist" header in its request. Although the
linkage between this subscription and the one sent by the
terminal is left up to the application, this message
demonstrates some reasonable behavior by including "Accept"
headers for all of the body types it knows the subscriber
(Terminal) supports. This is safe to do, since the local RLS
will only pass these formats through to the subscriber, and does
not need to actually understand them.
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Local RLS -> Presence Server in example.net
SUBSCRIBE sip:ed@example.net SIP/2.0
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bKMEyGjdG1LH
Max-Forwards: 70
To: <sip:ed@example.net>
From: <sip:pres.example.com>;tag=aM5icQu9
Call-ID: Ugwz5ARxNw@pres.example.com
CSeq: 870936068 SUBSCRIBE
Contact: <sip:pres.example.com>
Event: presence
Expires: 3600
Supported: eventlist
Accept: application/cpim-pidf+xml
Accept: application/rlmi+xml
Accept: multipart/related
Accept: multipart/signed
Accept: multipart/encrypted
Content-Length: 0
6. The Presence Server in example.net completes the SUBSCRIBE
transaction. Note that authentication and would normally take
place at this point in the callflow. Those steps are omitted
for brevity.
Presence Server in example.net -> Local RLS
SIP/2.0 200 OK
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bKMEyGjdG1LH
To: <sip:ed@example.net>;tag=e45TmHTh
From: <sip:pres.example.com>;tag=aM5icQu9
Call-ID: Ugwz5ARxNw@pres.example.com
CSeq: 870936068 SUBSCRIBE
Contact: <sip:example.net>
Event: presence
Expires: 3600
Content-Length: 0
7. In this example, we assume that the server at example.net
doesn't have enough authorization information to reject or
accept our subscription. The initial notify, therefore,
contains a "Subscription-State" of "pending". Presumably, the
party responsible for accepting or denying authorization for the
resource is notified of this change; however, those steps are
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not included in this call flow for brevity.
Presence Server in example.net -> Local RLS
NOTIFY sip:pres.example.com SIP/2.0
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bKfwpklPxmrW
Max-Forwards: 70
From: <sip:ed@example.net>;tag=e45TmHTh
To: <sip:pres.example.com>;tag=aM5icQu9
Call-ID: Ugwz5ARxNw@pres.example.com
CSeq: 1002640632 NOTIFY
Contact: <sip:example.net>
Subscription-State: pending;expires=3600
Event: presence
Require: eventlist
Content-Length: 0
8. The local RLS completes the NOTIFY transaction. Note that, at
this point, the Local RLS has new information to report to the
subscriber. Whether it chooses to report the information
immediately or spool it up for later delivery is completely up
to the application. For this example, we assume that the RLS
will wait for a short period of time before doing so, in order
to allow the subscriptions it sent out sufficient time to
provide useful data.
Local RLS -> Presence Server in example.net
SIP/2.0 200 OK
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bKfwpklPxmrW
From: <sip:ed@example.net>;tag=e45TmHTh
To: <sip:pres.example.com>;tag=aM5icQu9
Call-ID: Ugwz5ARxNw@pres.example.com
CSeq: 1002640632 NOTIFY
Contact: <sip:pres.example.com>
Event: presence
Content-Length: 0
9. The Local RLS subscribes to the state of the other non-local
resource.
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Local RLS -> RLS in example.org
SUBSCRIBE sip:adam-friends@example.org SIP/2.0
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bKFSrAF8CZFL
Max-Forwards: 70
To: <sip:adam-friends@example.org>
From: <sip:pres.example.com>;tag=a12eztNf
Call-ID: kBq5XhtZLN@pres.example.com
CSeq: 980774491 SUBSCRIBE
Contact: <sip:pres.example.com>
Event: presence
Expires: 3600
Supported: eventlist
Accept: application/cpim-pidf+xml
Accept: application/rlmi+xml
Accept: multipart/related
Accept: multipart/signed
Accept: multipart/encrypted
Content-Length: 0
10. The RLS in example.org completes the SUBSCRIBE transaction.
Note that authentication and would normally take place at this
point in the callflow. Those steps are omitted for brevity.
RLS in example.org -> Local RLS
SIP/2.0 200 OK
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bKFSrAF8CZFL
To: <sip:adam-friends@example.org>;tag=JenZ40P3
From: <sip:pres.example.com>;tag=a12eztNf
Call-ID: kBq5XhtZLN@pres.example.com
CSeq: 980774491 SUBSCRIBE
Contact: <sip:example.org>
Event: presence
Expires: 3600
Content-Length: 0
11. In this example, we are asserting that the RLS in example.org is
also an authority for presence information for the users in the
"example.org" domain. The NOTIFY contains an RLMI document
describing the contained buddy list, as well as presence
information for those users. In this particular case, the RLS
in example.org has chosen to PGP sign [11] the body of the
NOTIFY message.
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RLS in example.org -> Local RLS
NOTIFY sip:pres.example.com SIP/2.0
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bKmGL1nyZfQI
Max-Forwards: 70
From: <sip:adam-friends@example.org>;tag=JenZ40P3
To: <sip:pres.example.com>;tag=a12eztNf
Call-ID: kBq5XhtZLN@pres.example.com
CSeq: 294444656 NOTIFY
Contact: <sip:example.org>
Event: presence
Subscription-State: pending
Require: eventlist
Content-Type: multipart/signed;protocol="application/pgp-signature";
micalc="pgp-md5";boundary="l3WMZaaL8NpQWGnQ4mlU"
Content-Length: 2038
--l3WMZaaL8NpQWGnQ4mlU
Content-Transfer-Encoding: 8bit
Content-ID: <ZPvJHL@example.org>
Content-Type: multipart/related;type="application/rlmi+xml";
start="<Cvjpeo@example.org>";boundary="tuLLl3lDyPZX0GMr2YOo"
--tuLLl3lDyPZX0GMr2YOo
Content-Transfer-Encoding: 8bit
Content-ID: <Cvjpeo@example.org>
Content-Type: application/rlmi+xml;charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
<list uri="sip:adam-friends@example.org" version="1"
name="Buddy List at ORG" fullState="true">
<resource uri="sip:joe@example.org" name="Joe Thomas">
<instance id="1" state="active" cid="mrEakg@example.org"/>
</resource>
<resource uri="sip:mark@example.org" name="Mark Edwards">
<instance id="1" state="active" cid="KKMDmv@example.org"/>
</resource>
</list>
--tuLLl3lDyPZX0GMr2YOo
Content-Transfer-Encoding: 8bit
Content-ID: <mrEakg@example.org>
Content-Type: application/cpim-pidf+xml;charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
entity="sip:joe@example.org">
<tuple id="7823a4">
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<status>
<basic>open</basic>
</status>
<contact priority="1.0">sip:joe@example.org</contact>
</tuple>
</presence>
--tuLLl3lDyPZX0GMr2YOo
Content-Transfer-Encoding: 8bit
Content-ID: <KKMDmv@example.org>
Content-Type: application/cpim-pidf+xml;charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
entity="sip:mark@example.org">
<tuple id="398075">
<status>
<basic>closed</basic>
</status>
</tuple>
</presence>
--tuLLl3lDyPZX0GMr2YOo--
--l3WMZaaL8NpQWGnQ4mlU
Content-Transfer-Encoding: 8bit
Content-ID: <K9LB7k@example.org>
Content-Type: application/pgp-signature
-----BEGIN PGP MESSAGE-----
Version: 2.6.2
iQCVAwUBMJrRF2N9oWBghPDJAQE9UQQAtl7LuRVndBjrk4EqYBIb3h5QXIX/LC//
jJV5bNvkZIGPIcEmI5iFd9boEgvpirHtIREEqLQRkYNoBActFBZmh9GC3C041WGq
uMbrbxc+nIs1TIKlA08rVi9ig/2Yh7LFrK5Ein57U/W72vgSxLhe/zhdfolT9Brn
HOxEa44b+EI=
=ndaj
-----END PGP MESSAGE-----
--l3WMZaaL8NpQWGnQ4mlU--
12. The Local RLS completes the NOTIFY transaction.
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Local RLS -> RLS in example.org
SIP/2.0 200 OK
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bKmGL1nyZfQI
From: <sip:adam-friends@example.org>;tag=JenZ40P3
To: <sip:pres.example.com>;tag=a12eztNf
Call-ID: kBq5XhtZLN@pres.example.com
CSeq: 294444656 NOTIFY
Contact: <sip:pres.example.com>
Event: presence
Content-Length: 0
13. At this point, the Local RLS decides it has collected enough
additional information to warrant sending a new notification to
the user. Although sending a full notification would be
perfectly acceptable, the RLS decides to send a partial
notification instead. The RLMI document contains only
information for the updated resources, as indicated by setting
the "fullState" parameter to "false".
Local RLS -> Terminal
NOTIFY sip:terminal.example.com SIP/2.0
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bK4EPlfSFQK1
Max-Forwards: 70
From: <sip:adam-buddies@pres.example.com>;tag=zpNctbZq
To: <sip:adam@example.com>;tag=ie4hbb8t
Call-ID: cdB34qLToC@terminal.example.com
CSeq: 997935769 NOTIFY
Contact: <sip:pres.example.com>
Event: presence
Subscription-State: active;expires=7200
Require: eventlist
Content-Type: multipart/related;type="application/rlmi+xml";
start="<2BEI83@pres.example.com>";boundary="TfZxoxgAvLqgj4wRWPDL"
Content-Length: 2862
--TfZxoxgAvLqgj4wRWPDL
Content-Transfer-Encoding: 8bit
Content-ID: <2BEI83@pres.example.com>
Content-Type: application/rlmi+xml;charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
<list uri="sip:adam-friends@pres.example.com" version="2"
name="Buddy List at COM" fullState="false">
<resource uri="sip:ed@example.net" name="Ed at NET">
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<instance id="sdlkmeopdf" state="pending"/>
</resource>
<resource uri="sip:adam-friends@example.org" name="My Friends at ORG">
<instance id="cmpqweitlp" state="active" cid="1KQhyE@pres.example.com"/>
</resource>
</list>
--TfZxoxgAvLqgj4wRWPDL
Content-Transfer-Encoding: 8bit
Content-ID: <1KQhyE@pres.example.com>
Content-Type: multipart/signed;protocol="application/pgp-signature";
micalc="pgp-md5";boundary="l3WMZaaL8NpQWGnQ4mlU"
--l3WMZaaL8NpQWGnQ4mlU
Content-Transfer-Encoding: 8bit
Content-ID: <ZPvJHL@example.org>
Content-Type: multipart/related;type="application/rlmi+xml";
start="<Cvjpeo@example.org>";boundary="tuLLl3lDyPZX0GMr2YOo"
--tuLLl3lDyPZX0GMr2YOo
Content-Transfer-Encoding: 8bit
Content-ID: <Cvjpeo@example.org>
Content-Type: application/rlmi+xml;charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
<list uri="sip:adam-friends@example.org" version="1"
name="Buddy List at ORG" fullState="true">
<resource uri="sip:joe@example.org" name="Joe Thomas">
<instance id="1" state="active" cid="mrEakg@example.org"/>
</resource>
<resource uri="sip:mark@example.org" name="Mark Edwards">
<instance id="1" state="active" cid="KKMDmv@example.org"/>
</resource>
</list>
--tuLLl3lDyPZX0GMr2YOo
Content-Transfer-Encoding: 8bit
Content-ID: <mrEakg@example.org>
Content-Type: application/cpim-pidf+xml;charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
entity="sip:joe@example.org">
<tuple id="7823a4">
<status>
<basic>open</basic>
</status>
<contact priority="1.0">sip:joe@example.org</contact>
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</tuple>
</presence>
--tuLLl3lDyPZX0GMr2YOo
Content-Transfer-Encoding: 8bit
Content-ID: <KKMDmv@example.org>
Content-Type: application/cpim-pidf+xml;charset="UTF-8"
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
entity="sip:mark@example.org">
<tuple id="398075">
<status>
<basic>closed</basic>
</status>
</tuple>
</presence>
--tuLLl3lDyPZX0GMr2YOo--
--l3WMZaaL8NpQWGnQ4mlU
Content-Transfer-Encoding: 8bit
Content-ID: <K9LB7k@example.org>
Content-Type: application/pgp-signature
-----BEGIN PGP MESSAGE-----
Version: 2.6.2
iQCVAwUBMJrRF2N9oWBghPDJAQE9UQQAtl7LuRVndBjrk4EqYBIb3h5QXIX/LC//
jJV5bNvkZIGPIcEmI5iFd9boEgvpirHtIREEqLQRkYNoBActFBZmh9GC3C041WGq
uMbrbxc+nIs1TIKlA08rVi9ig/2Yh7LFrK5Ein57U/W72vgSxLhe/zhdfolT9Brn
HOxEa44b+EI=
=ndaj
-----END PGP MESSAGE-----
--l3WMZaaL8NpQWGnQ4mlU--
--TfZxoxgAvLqgj4wRWPDL--
14. The terminal completes the NOTIFY transaction.
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Terminal -> Local RLS
SIP/2.0 200 OK
Via: SIP/2.0/TCP pres.example.com;branch=z9hG4bK4EPlfSFQK1
From: <sip:adam-buddies@pres.example.com>;tag=zpNctbZq
To: <sip:adam@example.com>;tag=ie4hbb8t
Call-ID: cdB34qLToC@terminal.example.com
CSeq: 997935769 NOTIFY
Contact: <sip:terminal.example.com>
Content-Length: 0
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6. Security Considerations
Note that the mechanisms for obtaining state information for
resources in a list are generally left to the RLS implementor. Some
of the security issues below are specific to the the circumstance
that a SIP back-end subscription is used for such a purpose. Non-SIP
mechanisms for obtaining state information of resources in a list
will typically have their own security issues associated with doing
so; however, exhaustively enumerating such access methods is not
possible in this document. Implementors using such mechanisms must
analyse their chosen access methods for relevant security issues.
6.1 Authentication
The usage of the RLS does introduce some security considerations. If
back-end subscriptions are required to retrieve resource state
information, the end user is no longer the direct subscriber to the
state of the resource. If the notifier for the resource demands end-
to-end authentication, the RLS will need to be provided appropriate
credentials to access those resources (e.g. shared secrets for
Digest authentication). This requires a certain level of trust
between the user and their RLS. This specification does not describe
any particular means of providing such credentials to the RLS (such
as uploading a shared secret). However, any such upload mechanism
MUST ensure privacy of the key data; using HTTPS to fill out a form
is a reasonable method.
If the notifier for the resource is using a transitive trust model to
validate the subscriber, then this works well with the RLS concept
and back-end subscriptions. The RLS would authenticate the
subscriber, and then MAY use the SIP extensions for network asserted
identity [6][7] to provide an authenticated identity to the notifiers
for the resource.
6.2 Risks of Improper Aggregation
A resource list server typically serves information to multiple
subscribers at once. In many cases, resources may be present in
several lists; additionally, it is quite possible that resource list
servers will have two users subscribe to the same list.
In these cases, misguided RLS implementations may attempt to minimize
network load by maintaining only one back-end subscription to a
resource in a list, and presenting the result of such a subscription
to more than one user. Of course, doing so circumvents any
authorization policy that the notifier for the resource maintains.
It is important to keep in mind that authorization is often much more
than a simple binary "allowed/not allowed" decision; resources may
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render very different -- and even conflicting -- resource states,
depending on the identity of the subscribing user.
Implementations MUST NOT attempt to perform this type of optimization
unless adequate access to complete authorizaton policy can be
guaranteed. Note that this is a very difficult problem to solve
correctly; even in the cases that such access is beleived possible,
this mode of operation is NOT RECOMMENDED.
6.3 Signing and Sealing
Implementors should keep in mind that any section of the MIME body
may be signed and/or encrypted as necessary. Resource List Servers
should take care not to modify any MIME bodies they receive from any
back-end subscriptions, and should not generally rely on being able
to read them.
In order to facilitate security, resource list servers SHOULD pass
along indication for support of "multipart/signed" and "multipart/
encrypted" content types to any SIP back-end subscriptions, if the
subscriber includes them in the initial SUBSCRIBE message. Not doing
so may actually result in resources refusling to divulge state (if
notifier policy requires encryption, but the RLS fails to convey
support), or subscribers discarding valid state (if subscriber policy
requires a signature, but the RLS fails to convey support).
Note that actual implemetation of encryption and signing by the RLS
is not necessary to be able to pass through signed and/or encrypted
bodies.
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7. IANA Considerations
7.1 New SIP Option Tag: eventlist
Option Tag Name: eventlist
Description: Extension to allow subscriptions to collections of
resources
Published specification: RFC xxxx [[Note to RFC editor: replace xxxx
with the RFC number of this document when published]]
7.2 New MIME type for Resource List Meta-Information
MIME Media Type Name: application
MIME subtype name: rlmi+xml
Required parameters: None
Optional parameters: charset
See RFC 3023 [10] for a discussion of the charset parameter on
XML-derived MIME types. Since this MIME type is used exclusively
in SIP, the use of UTF-8 encoding is strongly encouraged.
Encoding considerations: 8-bit text
Security considerations: Security considerations specific to uses of
this this MIME type are discussed in RFC xxxx [[Note to RFC
editor: replace xxxx with the RFC number of this document when
published]]. RFC 1874 [9] and RFC 3023 [10] discuss security
issues common to all uses of XML.
Interoperability considerations: The use of this MIME body is
intended to be generally interoperable. No unique considerations
have been identified.
Published specification: RFC xxxx [[Note to RFC editor: replace xxxx
with the RFC number of this document when published]]
Applications which use this media type: This media type is used to
convey meta-information for the state of collections of resources
within a Session Initiation Protocol (SIP) subscription.
Additional information:
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Magic Number(s): None.
File Extension(s): None.
Macintosh File Type Code(s): None.
Object Identifier(s) or OID(s): None.
Intended usage: Limited Use
Other Information/General Comment: None.
Person to contact for further information:
Name: Adam Roach
E-Mail: adam@dynamicsoft.com
Author/Change Controller: The specification of this MIME type is a
work product of the SIMPLE working group, and was authored by
Adam Roach, Jonathan Rosenberg, and Ben Campbell. The IETF has
change control over its specification.
7.3 URN Sub-Namespace
URI: urn:ietf:params:xml:ns:rlmi
Description: This is the XML namespace URI for XML elements defined
by [RFCXXXX] to describe information about subscriptions when such
subscriptions are aggregated within a single SIP subscription. It
is used in the application/rlmi+xml body type.
Registrant Contact:
Name: Adam Roach
E-Mail: adam@dynamicsoft.com
Author/Change Controller: The specification of this MIME type is a
work product of the SIMPLE working group, and was authored by
Adam Roach, Jonathan Rosenberg, and Ben Campbell. The IETF has
change control over its specification.
XML:
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BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type"
content="text/html;charset=utf-8"/>
<title>Namespace for SIP Event Resource List
Meta-Information</title>
</head>
<body>
<h1>Namespace for SIP Event Resource List Meta-Information</h1>
<h2>application/rlmi+xml</h2>
<p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
</body>
</html>
END
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8. Acknowledgements
Thanks to Sean Olson for a review of and corrections to the usage of
XML in this protocol.
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Normative References
[1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[2] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[3] Borenstein, N. and N. Freed, "MIME (Multipurpose Internet Mail
Extensions) Part One: Mechanisms for Specifying and Describing
the Format of Internet Message Bodies", RFC 1521, September
1993.
[4] Levinson, E., "The MIME Multipart/Related Content-type", RFC
2387, August 1998.
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Non-Normative References
[5] Rosenberg, J., "Session Initiation Protocol (SIP) Extensions
for Presence", draft-ietf-simple-presence-07 (work in
progress), May 2002.
[6] Watson, M., Peterson, J. and C. Jennings, "Private Extensions
to the Session Initiation Protocol (SIP) for Asserted Identity
within Trusted Networks", draft-ietf-sip-asserted-identity-02
(work in progress), August 2002.
[7] Peterson, J., "Enhancements for Authenticated Identity
Management in the Session Initiation Protocol (SIP)", draft-
peterson-sip-identity-01 (work in progress), July 2002.
[8] Olson, S., "A Mechanism for Content Indirection in Session
Initiation Protocol (SIP) Messages", draft-ietf-sip-content-
indirect-mech-01 (work in progress), November 2002.
[9] Levinson, E., "SGML Media Types", RFC 1874, December 1995.
[10] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
3023, January 2001.
[11] Elkins, M., Del Torto, D., Levien, R. and T. Roessler, "MIME
Security with OpenPGP", RFC 3156, August 2001.
[12] Galvin, J., Murphy, S., Crocker, S. and N. Freed, "Security
Multiparts for MIME: Multipart/Signed and Multipart/Encrypted",
RFC 1847, October 1995.
Authors' Addresses
Adam Roach
dynamicsoft
5100 Tennyson Pkwy
Suite 1200
Plano, TX 75024
US
EMail: adam@dynamicsoft.com
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Jonathan Rosenberg
dynamicsoft
72 Eagle Rock Ave.
First Floor
East Hanover, NJ 07936
US
EMail: jdrosen@dynamicsoft.com
Ben Campbell
dynamicsoft
5100 Tennyson Pkwy
Suite 1200
Plano, TX 75024
US
EMail: bcampbell@dynamicsoft.com
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Appendix A. Changes
Note that this section will be removed before publication as an RFC.
A.1 Changes since -00
o Removed text in several places which went into detail about
specific implementations which used SIP SUB/NOT for back-end
subscriptions. Some of this text will probably be published later
as part of an implementors' guide.
o Removed specific semantics for "Event" header parameters and
SUBSCRIBE bodies. These will be defined on a per-package basis,
probably by the filtering work.
o Added "cid" attribute to <list> elements.
o Reworked XML schema definition for meta-information.
o Added IANA registration for XML namespace.
o Minor editorial fixes
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Full Copyright Statement
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Acknowledgement
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