SIPPING D. Petrie
Internet-Draft Pingtel Corp.
Expires: November 15, 2004 May 17, 2004
A Framework for Session Initiation Protocol User Agent Profile
Delivery
draft-ietf-sipping-config-framework-03.txt
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 (2004). All Rights Reserved.
Abstract
This document defines the application of a set of protocols for
providing profile data to SIP user agents. The objective is to
define a means for automatically providing profile data a user agent
needs to be functional without user or administrative intervention.
The framework for discovery, delivery, notification and updates of
user agent profile data is defined here. As part of this framework a
new SIP event package is defined here for the notification of profile
changes. This framework is also intended to ease ongoing
administration and upgrading of large scale deployments of SIP user
agents. The contents and format of the profile data to be defined is
outside the scope of this document.
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Table of Contents
1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 Requirements Terminology . . . . . . . . . . . . . . . . . 3
2.2 Profile Delivery Framework Terminology . . . . . . . . . . 4
2.3 Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Profile Change Event Notification Package . . . . . . . . . 6
3.1 Event Package Name . . . . . . . . . . . . . . . . . . . . 6
3.2 Event Package Parameters . . . . . . . . . . . . . . . . . 6
3.3 SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . 9
3.4 Subscription Duration . . . . . . . . . . . . . . . . . . 9
3.5 NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . 9
3.6 Notifier processing of SUBSCRIBE requests . . . . . . . . 10
3.7 Notifier generation of NOTIFY requests . . . . . . . . . . 10
3.8 Subscriber processing of NOTIFY requests . . . . . . . . . 11
3.9 Handling of forked requests . . . . . . . . . . . . . . . 11
3.10 Rate of notifications . . . . . . . . . . . . . . . . . 11
3.11 State Agents . . . . . . . . . . . . . . . . . . . . . . 12
3.12 Examples . . . . . . . . . . . . . . . . . . . . . . . . 12
3.13 Use of URIs to Retrieve State . . . . . . . . . . . . . 13
4. Profile Delivery Framework Details . . . . . . . . . . . . . 13
4.1 Discovery of Subscription URI . . . . . . . . . . . . . . 13
4.2 Enrollment with Profile Server . . . . . . . . . . . . . . 15
4.3 Notification of Profile Changes . . . . . . . . . . . . . 15
4.4 Retrieval of Profile Data . . . . . . . . . . . . . . . . 15
4.5 Upload of Profile Changes . . . . . . . . . . . . . . . . 16
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . 16
5.1 SIP Event Package . . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . 16
6.1 Symmetric Encryption of Profile Data . . . . . . . . . . . 16
7. Differences from Simple XCAP Package . . . . . . . . . . . . 17
8. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . 17
9. Change History . . . . . . . . . . . . . . . . . . . . . . . 17
9.1 Changes from draft-ietf-sipping-config-framework-02.txt . 18
9.2 Changes from draft-ietf-sipping-config-framework-01.txt . 18
9.3 Changes from draft-ietf-sipping-config-framework-00.txt . 18
9.4 Changes from
draft-petrie-sipping-config-framework-00.txt . . . . . . . 18
9.5 Changes from draft-petrie-sip-config-framework-01.txt . . 19
9.6 Changes from draft-petrie-sip-config-framework-00.txt . . 19
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . 21
A. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 21
Intellectual Property and Copyright Statements . . . . . . . 22
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1. Motivation
Today all SIP user agent implementers use proprietary means of
delivering user or device profiles to the user agent. The profile
delivery framework defined in this document is intended to enable a
first phase migration to a standard means of providing profiles to
SIP user agents. It is expected that UA implementers will be able to
use this framework as a means of delivering their existing
proprietary user and device data profiles (i.e. using their existing
proprietary binary or text formats). This in itself is a tremendous
advantage in that a SIP environment can use a single profile delivery
server for profile data to user agents from multiple implementers.
Follow-on standardization activities can:
1. define a standard profile content format framework (e.g. XML
with name spaces [??] or name-value pairs [RFC0822]).
2. specify the content (i.e. name the profile data parameters, xml
schema, name spaces) of the data profiles.
One of the objectives of the framework described in this document is
to provide a start up experience similar to that of users of an
analog telephone. When you plug in an analog telephone it just works
(assuming the line is live and the switch has been provisioned).
There is no end user configuration required to make analog phone
work, at least in a basic sense. So the objective here is to be able
to take a new SIP user agent out of the box, plug it in or install
the software and have it get its profiles without human intervention
other than security measures. This is necessary for cost effective
deployment of large numbers of user agents.
Another objective is to provide a scalable means for ongoing
administration of profiles. Administrators and users are likely to
want to make changes to user and device profiles.
Additional requirements for the framework defined in this document
are described in: [I-D.ietf-sipping-ua-prof-framewk-reqs],
[I-D.sinnreich-sipdev-req]
2. Introduction
2.1 Requirements Terminology
Keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT" and
"MAY" that appear in this document are to be interpreted as described
in RFC 2119[RFC2119].
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2.2 Profile Delivery Framework Terminology
profile - data set specific to a user or device.
device - SIP user agent, either software or hardware appliance.
profile content server - The server that provides the content of the
profiles using the protocol specified by the URL scheme.
notifier - The SIP user agent server which processes SUBSCRIBE
requests for events and sends NOTIFY requests with profile data or
URI(s) point to the data.
profile delivery server - The logical collection of the SIP notifier
and the server which provides the contents of the profile URI(s).
2.3 Overview
The profile life cycle can be described by five functional steps.
These steps are not necessarily discrete. However it is useful to
describe these steps as logically distinct. These steps are named as
follows:
Discovery - discover a profile delivery server
Enrollment - enroll with the profile delivery server
Profile Retrieval - retrieve profile data
Profile Change Notification - receive notification of profile changes
Profile Change Upload - upload profile data changes back to the
profile delivery server
Discovery is the process by which a UA finds the address and port at
which it enrolls with the profile delivery server. As there is no
single discovery mechanism which will work in all network
environments, a number of discovery mechanisms are defined with a
prescribed order in which the UA tries them until one succeeds.
Enrollment is the process by which a UA makes itself known to the
profile delivery server. In enrolling the UA provides identity
information, name requested profile type(s) and supported protocols
for profile retrieval. It also subscribes to a mechanism for
notification of profile changes. As a result of enrollment, the UA
receives the data or the URI for each of the profiles that the
profile delivery server is able to provide. Each profile type (set)
requires a separate enrollment or SUBSCRIBE session.
Profile Retrieval is the process of retrieving the content for each
of the profiles the UA requested.
Profile Change Notification is the process by which the profile
delivery server notifies the UA that the content of one or more of
the profiles has changed. If the content is provided indirectly the
UA SHOULD retrieve the profile from the specified URI upon receipt of
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the change notification.
Profile Upload is the process by which a UA or other entity (e.g.
OSS, corporate directory or configuration management server) pushes a
change to the profile data back up to the profile delivery server.
This framework defines a new SIP event package [RFC3265] to solve
enrollment and profile change notification steps.
The question arises as to why SIP should be used for the profile
delivery framework. In this document SIP is used for only a small
portion of the framework. Other existing protocols are more
appropriate for transport of the profile contents (to and from the
user agent) and are suggested in this document. The discovery step
is simply a specified order and application of existing protocols.
SIP is only needed for the enrollment and change notification
functionality of the profile delivery framework. In many SIP
environments (e.g. carrier/subscriber and multi-site enterprise)
firewall, NAT and IP addressing issues make it difficult to get
messages between the profile delivery server and the user agent
requiring the profiles.
With SIP the users and devices already are assigned globally routable
addresses. In addition the firewall and NAT problems are already
presumably solved in the environments in which SIP user agents are to
be used. Therefore SIP is the best solution for allowing the user
agent to enroll with the profile delivery server which may require
traversal of multiple firewalls and NATs. For the same reason the
notification of profile changes is best solved by SIP.
It is assumed that the content delivery server will be either in the
public network or accessible through a DMZ. The user agents
requiring profiles may be behind firewalls and NATs and many
protocols, such as HTTP, may be used for profile content retrieval
without special consideration in the firewalls and NATs.
A conscious separation of user, device and local network profiles is
made in this document. This is useful to provide features such as
hoteling as well as securing or restricting user agent functionality.
By maintaining this separation, a user may walk up to someone else's
user agent and direct that user agent to get their profile data. In
doing so the user agent can replace the previous user's profile data
while still keeping the devices profile data that may be necessary
for core functionality and communication described in this document.
The local network profiles are relevant to a visiting device which
gets plugged in to a foreign network. The concept of the local
network providing profile data is useful to provide hoteling
(described above) as well as local policy data that may constrain the
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user or device behavior relative to the local network. For example
media types and codecs may be constrained to reflect the networks
capabilities.
3. Profile Change Event Notification Package
This section defines a new SIP event package [RFC3265]. The purpose
of this event package is to send to subscribers notification of
content changes to the profile(s) of interest and to provide the
location of the profile(s) via content indirection
[I-D.ietf-sip-content-indirect-mech] or directly in the body of the
NOTIFY. Frequently the profiles delivered to the user agent are much
larger (e.g. several KB or even several MB) than the MTU of the
network. These larger profiles will cause larger than normal SIP
messages and consequently higher impact on the SIP servers and
infrastructure. To avoid the higher impact and load on the SIP
infrastructure, content indirection SHOULD be used if the profile is
large enough to cause packet fragmentation over the transport
protocol. The user agent SHOULD specify the profile delivery means
and format via the MIME type in the Accepts header.
The MIME types or formats of profile to be delivered via this
framework are to be defined in other documents. These profile MIME
types specified in the Accepts header along with the profile types
specified in the Event header parameter "profile-name" MAY be used to
specify which profiles get delivered either directly or indirectly in
the NOTIFY requests. When content indirection is not used, it is
more important to specify the minimum set of profiles, as the entire
content for all of the profiles is included in the NOTIFY request.
3.1 Event Package Name
The name of this package is "sip-profile". This value appears in the
Event header field present in SUBSCRIBE and NOTIFY requests for this
package as defined in [RFC3265].
3.2 Event Package Parameters
This package defines the following new parameters for the event
header: profile-name, vendor, model, version, effective-by. The
effective-by parameter is for use in NOTIFY requests only. The
others are for use in the SUBSCRIBE request, but may be used in
NOTIFY requests as well.
The profile-name parameter is used to indicate the token name of the
profile type the user agent wishes to obtain URIs for or to
explicitly specify the URI to which it is to be notified of change.
Using a token in this parameter allows the URL semantics for
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retrieving the profiles to be opaque to the subscribing user agent.
All it needs to know is the token value for this parameter. However
in some cases the user agent may know the URI of the profile and only
wishes to know about changes to the profile. The user agent MAY
supply the URI for the profile as the value of the profile-name
parameter. This document defines three type categories of profiles
and their token names. The contents or format of the profiles is
outside the scope of this document. The three types of profiles
define here are "user", "device" and "local". Specifying device type
profile(s) indicates the desire for the profile(s) (URIs when content
indirection is used) and change notification of all profiles that are
specific to the device or user agent. Specifying user type
profile(s) indicates the desire for the profiles(s) or URI(s) and
change notification of all profile(s) that are specific to the user.
Specifying local type profiles indicates the desire for profile(s) or
URI(s) specific to the local network. The user, device or local
network is identified in the URI of the SUBSCRIBE request. The
Accept header of the SUBSCRIBE request MUST include the MIME types
for all profile content types that the subscribing user agent wishes
to retrieve profiles or receive change notifications.
The user, device or local token in the profile-name parameter may
represent a class or set of profiles as opposed to a single
profile. As standards are defined for specific profile contents
related to the user device or local network, it may be desirable
to define additional tokens for the profile-name header. This is
to allow a user agent to subscribe to that specific profile as
opposed to the entire class or set of user or device profiles.
The rational for the separation of user, device and local network
type profiles is provided in Section 2.3. It should be noted that
any of the types may indicate that zero or more profiles or URIs are
provided in the NOTIFY request. As discussed, a default user may be
assigned to a device. In this scenario the profile delivery server
may provide the URI(s) in the NOTIFY request for the default user
when subscribing to the device profile type. Effectively the device
profile type becomes a superset of the user profile type
subscription. That is the list of profile URIs (or MIME parts if
multiple profiles are provided directly in the NOTIFY) provided when
requesting profile type "device" includes the profiles provided when
subscribing for profile type "user" for the default user of that
device. The user type is still useful in this scenario to allow the
user agent to obtain profile data or URIs for a user other than the
default user. This provides the ability to support a hoteling
function where a user may "login" to any user agent and have it use a
user's profile(s).
The data provided in the three types of profiles may overlap. As an
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example the codecs that a user prefers to use, the codecs that the
device supports (and the enterprise wishes to use), the codecs that
the local network can support (and the management wishes to allow)
all may overlap in how they are specified in the three corresponding
profiles. Typically these should be applied in the order of the
least to most constraint (i.e. user, device then local network).
However this policy of merging the constraints across the multiple
profile types can only unambiguously be defined along with the
profile format and syntax. This is out of scope for this document.
The "vendor", "model" and "version" parameter values are tokens
specified by the vendor of the user agent. These parameters are
useful to the profile delivery server to affect the profiles
provided. In some scenarios it is desirable to provide different
profiles based upon these parameters. For example feature parameter
X in a profile may work differently on two versions of user agent.
This gives the profile deliver server the ability to compensate for
or take advantage of the differences.
The "network-user" parameter is used when subscribing for local
network profiles. If the value of the profile-name parameter is not
"local", the "network-user" parameter has no defined meaning. If the
user has special privileges beyond that of an anonymous user in the
local network, the "network-user" parameter identifies the user to
the local network. The value of this parameter is the user's address
of record. The SUBSCRIBE server may authenticate the subscriber to
verify this AOR.
The "effective-by" parameter in the Event header of the NOTIFY
specifies the maximum number of seconds before the user agent MUST
make the new profile effective. A value of 0 (zero) indicates that
the user agent MUST make the profiles effective immediately (despite
possible service interruptions). This gives the profile delivery
server the power to control when the profile is effective. This may
be important to resolve an emergency problem or disable a user agent
immediately.
SUBSCRIBE request example:
Event: sip-profile;profile-name=device;
vendor=acme;model=Z100;version=1.2.3
Event: sip-profile;profile-name=
"http://example.com/services/user-profiles/users/freds.xml";
vendor=premier;model=trs8000;version=5.5
NOTIFY request examples:
Event:sip-profile;effective-by=0
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Event:sip-profile;effective-by=3600
3.3 SUBSCRIBE Bodies
This package defines no new use of the SUBSCRIBE request body.
3.4 Subscription Duration
As the presence (or lack of) a device or user agent it not very time
critical to the functionality of the profile delivery server, it is
recommended that default subscription duration be 86400 seconds (one
day).
3.5 NOTIFY Bodies
The size of profile content is likely to be hundreds to several
thousand bytes in size. Frequently even with very modest sized SDP
bodies, SIP messages get fragmented causing problems for many user
agents. For this reason the profile delivery server MUST use content
indirection [I-D.ietf-sip-content-indirect-mech] in the NOTIFY body
for providing the profiles if the Accept header of the SUBSCRIBE
included the MIME type: message/external-body indicating support for
content indirection.
When delivering profiles via content indirection the profile delivery
server MUST include the Content-ID defined in
[I-D.ietf-sip-content-indirect-mech] for each profile URL. This is
to avoid unnecessary download of the profiles. Some user agents are
not able to make a profile effective without rebooting or restarting.
Rebooting is probably something to be avoided on a user agent
performing services such as telephony. In this way the Content-ID
allows the user agent to avoid unnecessary interruption of service as
well. The Content-Type MUST be specified for each URI.
Initially it is expected that most user agent implementers will
use a proprietary content type for the profiles retrieved from the
URIs(s). It is hoped that over time a standard content type will
be specified that will be adopted by implementers of user agents.
One direction that appears to be promising for this content is to
use XML with name spaces [??] to segment the data into sets that
the user agent implementer may choose to support based upon
desired feature set. The specification of the content is out of
the scope of this document.
Likewise the URL scheme used in the content indirection is outside
the scope of this document. This document is agnostic to the URL
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schemes as the profile content may dictate what is required. It is
expected that TFTP [RFC3617], FTP [??], HTTP [RFC2616], HTTPS
[RFC2818], LDAP [RFC3377], XCAP [I-D.rosenberg-simple-xcap] and other
URL schemes are supported by this package and framework.
3.6 Notifier processing of SUBSCRIBE requests
The general rules for processing SUBSCRIBE requests [RFC3265] apply
to this package. If content indirection is used for delivering the
profiles, the notifier does not need to authenticate the subscription
as the profile content is not transported in the SUBSCRIBE or NOTIFY
transaction messages. With content indirection only URLs are
transported in the NOTIFY request which may be secured using the
techniques in Section 6. If content indirection is not used, SIPS
and SIP authentication SHOULD be used.
The behavior of the profile delivery server is left to the
implementer. The profile delivery server may be as simple as a SIP
SUBSCRIBE UAS and NOTIFY UAC front end to a simple HTTP server
delivering static files that are hand edited. At the other extreme
the profile delivery server can be part of a configuration management
system that integrates with a corporate directory and IT system or
carrier OSS, where the profiles are automatically generated. The
design of this framework intentionally provides the flexibility of
implementation from simple/cheap to complex/expensive.
If the user or device is not known to the profile delivery server,
the implementer MAY accept the subscription or reject it. It is
recommended that the implementer accept the subscription. It is
useful for the profile delivery server to maintain the subscription
as an administrator may add the user or device to the system,
defining the profile contents. This allows the profile delivery
server to immediately send a NOTIFY request with the profile URIs.
If the profile delivery server does not accept the subscription from
an unknown user or device, the administer or user must manually
provoke the user agent to reSUBSCRIBE. This may be difficult if the
user agent and administrator are at different sites.
3.7 Notifier generation of NOTIFY requests
As in [RFC3265], the profile delivery server MUST always send a
NOTIFY request upon accepting a subscription. If the device or user
is unknown to the profile delivery server and it chooses to accept
the subscription, the implementer has two choices. A NOTIFY MAY be
sent with no body or content indirection containing the profile
URI(s). Alternatively a NOTIFY MAY be sent with URI(s) pointing to a
default data set. Typically this data set allows for only limited
functionality of the user agent (e.g. a phone user agent with data
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to call help desk and emergency services.). This is an
implementation and business policy decision.
A user or device known and fully provisioned on the profile delivery
server SHOULD send a NOTIFY with profile data or content indirection
containing URIs for all of the profiles associated with the user or
device (i.e. whichever specified in the profile-name parameter).
The device may be associated with a default user. The URI(s) for
this default user profiles MAY be included with the URI(s) of the
device if the profile type specified is device.
A user agent can provide Hoteling by collecting a users AOR and
credentials needed to SUBSCRIBE and retrieve the user profiles from
the URI(s). Hoteling functionality is achieved by subscribing to the
AOR and specifying the "user" profile type. This same mechanism can
be used to secure a user agent, requiring a user to login to enable
functionality beyond the default users restricted functionality.
The profile delivery server MAY specify when the new profiles MUST be
made effective by the user agent. By default the user agent makes
the profiles effective as soon as it thinks that it is non-obtrusive.
Profile changes SHOULD effect behavior all new sessions which are
created after the notification, but may not be able to effect
existing sessions. However the profile delivery server MAY specify a
maximum time in seconds (zero or more), in the effective-by event
header parameter, by which the user agent MUST make the new profiles
effective for all sessions.
3.8 Subscriber processing of NOTIFY requests
The user agent subscribing to this event package MUST adhere to the
NOTIFY request processing behavior specified in [RFC3265]. The user
agent MUST make the profiles effective as specified in the NOTIFY
request (see Section 3.7). The user agent SHOULD use one of the
techniques specified in [RFC3265] to securely retrieve the profiles.
3.9 Handling of forked requests
This event package allows the creation of only one dialog as a result
of an initial SUBSCRIBE request. The techniques to achieve this are
described in section 4.4.9 of [RFC3265].
3.10 Rate of notifications
It is anticipated that the rate of change for user and device
profiles will be very infrequent (i.e. days or weeks apart). For
this reason no throttling or minimum period between NOTIFY requests
is specified for this package.
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3.11 State Agents
State agents are not applicable to this event package.
3.12 Examples
SUBSCRIBE sip:00df1e004cd0@example.com SIP/2.0
Event: sip-profile;profile-name=device;vendor=acme;
model=Z100;version=1.2.3
From: sip:00df1e004cd0@acme.com;tag=1234
To: sip:00df1e004cd0@acme.com;tag=abcd
Call-ID: 3573853342923422@10.1.1.44
CSeq: 2131 SUBSCRIBE
Contact: sip:00df1e004cd0@10.1.1.44
Content-Length: 0
NOTIFY sip:00df1e004cd0@10.1.1.44 SIP/2.0
Event: sip-profile;effective-by=3600
From: sip:00df1e004cd0@acme.com;tag=abcd
To: sip:00df1e004cd0@acme.com;tag=1234
Call-ID: 3573853342923422@10.1.1.44
CSeq: 321 NOTIFY
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary=boundary42
Content-Length: ...
--boundary42
Content-Type: message/external-body;
access-type="URL";
expiration="Mon, 24 June 2002 09:00:00 GMT";
URL="http://www.example.com/devices/fsmith";
size=2222
Content-Type: application/z100-user-profile
Content-ID: <69ADF2E92@example.com>
--boundary42
Content-Type: message/external-body;
access-type="URL";
expiration="Mon, 24 June 2002 09:00:00 GMT";
URL="http://www.example.com/devices/ff00000036c5";
size=1234
Content-Type: application/z100-device-profile
Content-ID: <39EHF78SA@example.com>
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--boundary42--
3.13 Use of URIs to Retrieve State
The profile type specified determines what goes in the user part of
the SUBSRIBE URI. If the profile type requested is "device", the
user part of the URI is an identity that MUST be unique across all
user agents from all implementers. This identity must be static over
time so that the profile delivery server can keep a specific device
and its identity associated with its profiles. For Ethernet hardware
type user agents supporting only a single user at a time this is most
easily accomplished using its MAC address. Software based user
agents running on general purpose hardware may also be able to use
the MAC address for identity. However in situations where multiple
instances of user agents are running on the same hardware it may be
necessary to use another scheme, such as using a unique serial number
for each software user agent instance.
For example a device having a MAC address of 00df1e004cd0 might
subscribe to the device profile URI:
sip:00df1e004cd0@sipuaconfig.example.com. When subscribing to a
user profile for user Fred S. the user agent would subscribe to
the URI: sip:freds@sipuaconfig.example.com
If the profile type requested is "user", the URI in the SUBSCRIBE
request is the address of record for the user. This allows the user
to specify (e.g. login) to the user agent by simply entering their
known identity.
If the profile type specified in the profile-name parameter is
"local", the URI in the SUBSCRIBE request has the user ID: anonymous.
The host part of the URI is the local network name. This typically
is discovered as part of the DHCP request/response or provisioned as
part of the static IP configuration for the device. When subscribing
to the local network profile type the device should provide the
user's address of record in the "network-user" parameter, if the AOR
is known to the device. Example URI: sip:ananymous@example.com
4. Profile Delivery Framework Details
The following describes how different functional steps of the profile
delivery framework work. Also described here is how the event
package defined in this document provides the enrollment and
notification functions within the framework.
4.1 Discovery of Subscription URI
The discovery function is needed to bootstrap user agents to the
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point of knowing where to enroll with the profile delivery server.
Section 3.13 describes how to form the URI used to send the SUBSCRIBE
request for enrollment. However the bootstrapping problem for the
user agent (out of the box) is what to use for the host and port in
the URI. Due to the wide variation of environments in which the
enrolling user agent may reside (e.g. behind residential router,
enterprise LAN, ISP, dialup modem) and the limited control that the
administrator of the profile delivery server (e.g. enterprise,
service provider) may have over that environment, no single discovery
mechanism works everywhere. Therefore a number of mechanisms SHOULD
be tried in the specified order: SIP DHCP option [RFC3361], SIP DNS
SRV [RFC3263], DNS A record and manual.
1. The first discovery mechanism that SHOULD be tried is to
construct the SUBSCRIBE URI as described in Section 3.13 using
the host and port of out bound proxy discovered by the SIP DHCP
option as described in [RFC3361]. If the SIP DHCP option is not
provided in the DHCP response, no SIP response or a SIP failure
response other than for authorization is received for the
SUBSCRIBE request to the sip-profile event, the next discovery
mechanism SHOULD be tried.
2. The local IP network domain for the user agent, either configured
or discovered via DHCP, should be used with the technique in
[RFC3263] to obtain a host and port to use in the SUBSCRIBE URI.
If no SIP response or a SIP failure response other than for
authorization is received for the SUBSCRIBE request to the
sip-profile event, the next discovery mechanism SHOULD be tried.
3. The fully qualified host name constructed using the host name
"sipuaconfig" and concatenated with the local IP network domain
should be tried next using the technique in [RFC3263] to obtain a
host and port to use in the SUBSCRIBE URI. If no SIP response or
a SIP failure response other than for authorization is received
for the SUBSCRIBE request to the sip-profile event, the next
discovery mechanism SHOULD be tried.
4. If all other discovery techniques fail, the user agent MUST
provide a manual means for the user to enter the host and port
used to construct the SUBSCRIBE URI.
Once a user agent has successfully discovered, enrolled, received a
NOTIFY response with profile data or URI(s), the user agent SHOULD
cache the SUBCRIBE URI to avoid having to rediscover the profile
delivery server again in the future. The user agent SHOULD NOT cache
the SUBSCRIBE URI until it receives a NOTIFY with profile data or
URI(s). The reason for this is that a profile delivery server may
send 202 responses to SUBSCRIBE requests and NOTIFY responses to
unknown user agent (see Section 3.6) with no URIs. Until the profile
delivery server has sent a NOTIFY request with profile data or
URI(s), it has not agreed to provide profiles.
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To illustrate why the user agent should not cache the SUBSCRIBE
URI until profile URI(s) are provided in the NOTIFY, consider the
following example: a user agent running on a laptop plugged into
a visited LAN in which a foreign profile delivery server is
discovered. The profile delivery server never provides profile
URIs in the NOTIFY request as it is not provisioned to accept the
user agent. The user then takes the laptop to their enterprise
LAN. If the user agent cached the SUBSCRIBE URI from the visited
LAN (which did not provide profiles), when subsequently placed in
the enterprise LAN which is provisioned to provide profiles to the
user agent, the user agent would not attempt to discover the
profile delivery server.
4.2 Enrollment with Profile Server
Enrollment is accomplished by subscribing to the event package
described in Section 3. The enrollment process is useful to the
profile delivery server as it makes the server aware of user agent to
which it may delivery profiles (those user agents the profile
delivery server is provisioned to provide profiles to; those present
that the server may be provide profiles in the future; and those that
the server can automatically provide default profiles). It is an
implementation choice and business policy as to whether the profile
delivery server provides profiles to user agents that it is not
provisioned to do so. However the profile server SHOULD accept (with
2xx response) SUBSCRIBE requests from any user agent.
4.3 Notification of Profile Changes
The NOTIFY request in the sip-profile event package serves two
purposes. First it provides the user agent with a means to obtain
the profile data or URI(s) for desired profiles without requiring the
end user to manually enter them. It also provides the means for the
profile delivery server to notify the user agent that the content of
the profiles have changed and should be made effective.
4.4 Retrieval of Profile Data
The user agent retrieves its needed profile(s) via the URI(s)
provided in the NOTIFY request as specified in Section 3.5. The
profile delivery server SHOULD secure the content of the profiles
using one of the techniques described in Section 6. The user agent
SHOULD make the new profiles effective in the timeframe described in
Section 3.2.
The contents of the profiles SHOULD be cached by the user agent.
This it to avoid the situation where the content delivery server is
not available, leaving the user agent non-functional.
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4.5 Upload of Profile Changes
The user agent or other service MAY push changes up to the profile
delivery server using the technique appropriate to the profile's URL
scheme (e.g. HTTP PUT method, FTP put command). The technique for
pushing incremental or atomic changes MUST be described by the
specific profile data framework.
5. IANA Considerations
There are several IANA considerations associated with this
specification.
5.1 SIP Event Package
This specification registers a new event package as defined in
[RFC3265]. The following information required for this registration:
Package Name: sip-profile
Package or Template-Package: This is a package
Published Document: RFC XXXX (Note to RFC Editor: Please fill in
XXXX with the RFC number of this specification).
Person to Contact: Daniel Petrie dpetrie@pingtel.com
New event header parameters: profile-name, vendor, model, version,
effective-by
6. Security Considerations
Profiles may contain sensitive data such as user credentials. The
protection of this data depends upon how the data is delivered. If
the data is delivered in the NOTIFY body, SIP authentication MUST be
used for SUBSCRIPTION and SIPS and/or S/MIME MAY be use to encrypt
the data. If the data is provided via content indirection, SIP
authentication is not necessary for the SUBSCRIBE request. With
content indirection the data is protected via the authentication,
authorization and encryption mechanisms provided by the profile URL
scheme. Use of the URL scheme security mechanisms via content
indirection simplifies the security solution as the SIP event package
does not need to authenticate, authorize or protect the contents of
the SIP messages. Effectively the profile delivery server will
provide profile URI(s) to anyone. The URLs themselves are protected
via authentication, authorization and snooping (e.g. via HTTPS).
6.1 Symmetric Encryption of Profile Data
If the URL scheme used for content indirection does not provide
authentication, authorization or encryption, a technique to provide
this is to encrypt the profiles on the content delivery server using
a symmetric encryption algorithm using a shared key. The encrypted
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profiles are delivered by the content delivery server via the URIs
provided in the NOTIFY requests. Using this technique the profile
delivery server does not need to provide authentication or
authorization for the retrieval as the profiles are obscured. The
user agent must obtain the username and password from the user or
other out of band means to generate the key and decrypt the profiles.
7. Differences from Simple XCAP Package
The author of this document had an action item from the July 2003
IETF SIPPING WG meeting to consider resolving the differences of the
sip-profile and simple XCAP package [I-D.ietf-simple-xcap-package].
It is the author's opinion that XCAP [I-D.rosenberg-simple-xcap] can
be supported by the framework and event package defined in this
document and that this package provides a superset of the
functionality in the XCAP package. The following lists the
differences between the event packaged defined in this document vs.
the one defined in [I-D.ietf-simple-xcap-package].
The simple XCAP package requires that the relative path be known and
specified by the user agent when subscribing for change notification.
The event package in this document requires a token or complete URI
be known and specified when subscribing. The advantage of the token
is that bootstrapping is easier and well defined. It also leaves the
freedom of specifying and changing the entire path of the profile URL
up to the profile delivery server.
The event package defined in this document allows multiple URIs to be
provided in the NOTIFY request body as a result of a single token
specified in the SUBSCRIBE event parameter: profile-name. This
allows the profile delivery server to provide sets of profiles that
the user agent may not have enough information to specify in the
SUBSCRIBE URI (e.g. at boot strapping time the user agent may not
know the user's identity, but the profile delivery server may know
the default user for the device's identity) or the doc-component of
the simple XCAP package.
All other functional differences between
draft-ietf-sipping-config-framework-00 and
draft-ietf-simple-xcap-package-00 are believed to be resolved in this
version of this document.
8. Open Issues
9. Change History
Many thanks to those who contributed and commented on the many
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iterations of this document. Detailed input was provided by Jonathan
Rosenberg from Dynamicsoft, Henning Schulzrinne from Columbia U.,
Cullen Jennings from Cisco, Rohan Mahy from Cisco, Rich Schaaf from
Pingtel, Volker Hilt from Bell Labs.
9.1 Changes from draft-ietf-sipping-config-framework-02.txt
Added the concept of the local network as a source of profile data.
There are now three separate logical sources for profile data: user,
device and local network. Each of these requires a separate
subscription to obtain.
9.2 Changes from draft-ietf-sipping-config-framework-01.txt
Changed the name of the profile-type event parameter to profile-name.
Also allow the profile-name parameter to be either a token or an
explicit URI.
Allow content indirection to be optional. Clarified the use of the
Accept header to indicate how the profile is to be delivered.
Added some content to the Iana section.
9.3 Changes from draft-ietf-sipping-config-framework-00.txt
This version of the document was entirely restructured and re-written
from the previous version as it had been micro edited too much.
All of the aspects of defining the event package are now organized in
one section and is believed to be complete and up to date with
[RFC3265].
The URI used to subscribe to the event package is now either the user
or device address or record.
The user agent information (vendor, model, MAC and serial number) are
now provided as event header parameters.
Added a mechanism to force profile changes to be make effective by
the user agent in a specified maximum period of time.
Changed the name of the event package from sip-config to sip-profile
Three high level securityapproaches are now specified.
9.4 Changes from draft-petrie-sipping-config-framework-00.txt
Changed name to reflect SIPPING work group item
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Synchronized with changes to SIP DHCP [RFC3361], SIP [RFC3261] and
[RFC3263], SIP Events [RFC3265] and content indirection
[I-D.ietf-sip-content-indirect-mech]
Moved the device identity parameters from the From field parameters
to User-Agent header parameters.
Many thanks to Rich Schaaf of Pingtel, Cullen Jennings of Cisco and
Adam Roach of Dyamicsoft for the great comments and input.
9.5 Changes from draft-petrie-sip-config-framework-01.txt
Changed the name as this belongs in the SIPPING work group.
Minor edits
9.6 Changes from draft-petrie-sip-config-framework-00.txt
Split the enrollment into a single SUBSCRIBE dialog for each profile.
The 00 draft sent a single SUBSCRIBE listing all of the desired.
These have been split so that each enrollment can be routed
differently. As there is a concept of device specific and user
specific profiles, these may also be managed on separate servers.
For instance in a roaming situation the device might get its profile
data from a local server which knows the LAN specific profile data.
At the same time the user specific profiles might come from the
user's home environment profile delivery server.
Removed the Config-Expires header as it is largely superfluous with
the SUBSCRIBE Expires header.
Eliminated some of the complexity in the discovery mechanism.
Suggest caching information discovered about a profile delivery
server to avoid an avalanche problem when a whole building full of
devices powers up.
Added the User-Profile From header field parameter so that the device
can request a user specific profile for a user that is different from
the device's default user.
10 References
[I-D.ietf-simple-xcap-package]
Rosenberg, J., "A Session Initiation Protocol (SIP) Event
Package for Modification Events for the Extensible Markup
Language (XML) Configuration Access Protocol (XCAP)
Managed Documents", draft-ietf-simple-xcap-package-01
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(work in progress), February 2004.
[I-D.ietf-sip-content-indirect-mech]
Olson, S., "A Mechanism for Content Indirection in Session
Initiation Protocol (SIP) Messages",
draft-ietf-sip-content-indirect-mech-03 (work in
progress), June 2003.
[I-D.ietf-sipping-ua-prof-framewk-reqs]
Petrie, D. and C. Jennings, "Requirements for SIP User
Agent Profile Delivery Framework",
draft-ietf-sipping-ua-prof-framewk-reqs-00 (work in
progress), March 2003.
[I-D.rosenberg-simple-xcap]
Rosenberg, J., "The Extensible Markup Language (XML)
Configuration Access Protocol (XCAP)",
draft-rosenberg-simple-xcap-00 (work in progress), May
2003.
[I-D.sinnreich-sipdev-req]
Butcher, I., Lass, S., Petrie, D., Sinnreich, H. and C.
Stredicke, "SIP Telephony Device Requirements,
Configuration and Data", draft-sinnreich-sipdev-req-03
(work in progress), February 2004.
[RFC0822] Crocker, D., "Standard for the format of ARPA Internet
text messages", STD 11, RFC 822, August 1982.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A. and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
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RFC 2617, June 1999.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3261] 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.
[RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation
Protocol (SIP): Locating SIP Servers", RFC 3263, June
2002.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
[RFC3361] Schulzrinne, H., "Dynamic Host Configuration Protocol
(DHCP-for-IPv4) Option for Session Initiation Protocol
(SIP) Servers", RFC 3361, August 2002.
[RFC3377] Hodges, J. and R. Morgan, "Lightweight Directory Access
Protocol (v3): Technical Specification", RFC 3377,
September 2002.
[RFC3617] Lear, E., "Uniform Resource Identifier (URI) Scheme and
Applicability Statement for the Trivial File Transfer
Protocol (TFTP)", RFC 3617, October 2003.
Author's Address
Daniel Petrie
Pingtel Corp.
400 W. Cummings Park
Suite 2200
Woburn, MA 01801
US
Phone: "Dan Petrie (+1 781 938 5306)"<sip:dpetrie@pingtel.com>
EMail: dpetrie@pingtel.com
URI: http://www.pingtel.com/
Appendix A. Acknowledgments
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Petrie Expires November 15, 2004 [Page 23]
