One document matched: draft-tschofenig-sipping-spit-policy-01.txt
Differences from draft-tschofenig-sipping-spit-policy-00.txt
SIPPING H. Tschofenig
Internet-Draft Nokia Siemens Networks
Intended status: Standards Track D. Wing
Expires: January 9, 2008 Cisco
H. Schulzrinne
Columbia University
T. Froment
Alcatel-Lucent
G. Dawirs
University of Namur
July 8, 2007
A Document Format for Expressing Authorization Policies to tackle Spam
and Unwanted Communication for Internet Telephony
draft-tschofenig-sipping-spit-policy-01.txt
Status of this Memo
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This Internet-Draft will expire on January 9, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2007).
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Abstract
SPAM, defined as sending unsolicited messages to someone in bulk,
might be a problem on SIP open-wide deployed networks. The
responsibility for filtering or blocking calls can belong to
different elements in the call flow and may depend on various
factors. This document defines an authorization based policy
language that allows end users to upload anti-SPIT policies to
intermediaries, such as SIP proxies. These policies mitigate
unwanted SIP communications. It extends the Common Policy
authorization framework with additional conditions and actions. The
new conditions match a particular Session Initiation Protocol (SIP)
communication pattern based on a number of attributes. The range of
attributes includes information provided, for example, by SIP itself,
by the SIP identity mechanism, by information carried within SAML
assertions.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Generic Processing . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Structure of SPIT Authorization Documents . . . . . . . . 5
3.2. Rule Transport . . . . . . . . . . . . . . . . . . . . . . 5
4. Condition Elements . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Identity . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1.1. Acceptable Forms of Authentication . . . . . . . . . . 6
4.1.2. Computing a URI for the Sender . . . . . . . . . . . . 7
4.2. Sphere . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. SPIT Handling . . . . . . . . . . . . . . . . . . . . . . 9
4.4. Media List . . . . . . . . . . . . . . . . . . . . . . . . 9
4.5. Method List . . . . . . . . . . . . . . . . . . . . . . . 10
4.6. MIME List . . . . . . . . . . . . . . . . . . . . . . . . 10
4.7. Presence Status . . . . . . . . . . . . . . . . . . . . . 10
4.8. Rule Deactivated . . . . . . . . . . . . . . . . . . . . . 10
4.9. Time Period Condition . . . . . . . . . . . . . . . . . . 10
5. Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1. Execute Action . . . . . . . . . . . . . . . . . . . . . . 18
5.2. Forward To . . . . . . . . . . . . . . . . . . . . . . . . 18
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8. XCAP USAGE . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.1. Application Unique ID . . . . . . . . . . . . . . . . . . 27
8.2. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . 27
8.3. Default Namespace . . . . . . . . . . . . . . . . . . . . 27
8.4. MIME Type . . . . . . . . . . . . . . . . . . . . . . . . 27
8.5. Validation Constraints . . . . . . . . . . . . . . . . . . 27
8.6. Data Semantics . . . . . . . . . . . . . . . . . . . . . . 27
8.7. Naming Conventions . . . . . . . . . . . . . . . . . . . . 28
8.8. Resource Interdependencies . . . . . . . . . . . . . . . . 28
8.9. Authorization Policies . . . . . . . . . . . . . . . . . . 28
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
9.1. Anti-SPIT Policy XML Schema Registration . . . . . . . . . 28
9.2. Anti-SPIT Policy Namespace Registration . . . . . . . . . 28
9.3. XCAP Application Usage ID . . . . . . . . . . . . . . . . 29
10. Security Considerations . . . . . . . . . . . . . . . . . . . 29
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 29
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
13.1. Normative References . . . . . . . . . . . . . . . . . . . 30
13.2. Informative References . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34
Intellectual Property and Copyright Statements . . . . . . . . . . 36
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1. Introduction
The problem of SPAM for Internet Telephony (SPIT) is an imminent
challenge and only the combination of several techniques can provide
a framework for dealing with unwanted communication, as stated in
[I-D.jennings-sip-hashcash].
One important building block is to have a mechanism that can instruct
SIP intermediaries to react differently on incoming requests based on
policies. Different entities, such as end users, parents on behalf
of their children, system administrators in enterprise networks,
etc., might create and modify authorization policies. The conditions
in these policies can be created from many sources but some
information elements are more important than others. For example,
there is reason to believe that applying authorization policies based
on the authenticated identity is an effective way to accept a
communication attempt to deal with unsolicited communication.
Authentication based on the SIP identity mechanism, see [RFC4474], is
one important concept.
The requirements for the authorization policies described in this
document are outlined in [I-D.froment-sipping-spit-requirements]. A
framework document is available at
[I-D.tschofenig-sipping-framework-spit-reduction].
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
This document reuses the terminology from RFC 4745 [RFC4745]:
Rule maker:
The RM is an entity that creates the authorization policies that
react to unwanted connection attempts. The rule maker might be an
end user that owns the device, a VoIP service provider, a person
with a relationship to the end user (e.g., the parents of a child
using a mobile phone). A standardized policy language is needed
when the creation, modification and deletion of authorization
policies are not only a local matter.
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Authorization policy:
An authorization policy is given by a rule set. A rule set
contains an unordered list of rules. Each rule has a condition,
an action and a transformation component. The terms
'authorization policy', 'policy', 'rule set', 'authorization
policy rule', 'policy rule' and 'rule' are used interchangeably.
Authorization policies can be applied at the end host and/or by
intermediaries.
Permission:
The term permission refers to the action and transformation
components of a rule.
We use the term 'Recipient' for the entity that is target of the
communication attempt of a sender.
3. Generic Processing
3.1. Structure of SPIT Authorization Documents
A SPIT authorization document is an XML document, formatted according
to the schema defined in RFC 4745 [RFC4745]. SPIT authorization
documents inherit the MIME type of common policy documents,
application/auth-policy+xml. As described in [RFC4745], this
document is composed of rules which contain three parts - conditions,
actions, and transformations. Each action or transformation, which
is also called a permission, has the property of being a positive
grant to the authorization server to perform the resulting actions,
be it allow, block etc . As a result, there is a well-defined
mechanism for combining actions and transformations obtained from
several sources. This mechanism therefore can be used to filter
connection attempts thus leading to effective SPIT prevention.
3.2. Rule Transport
Policies are XML documents that are stored at a Proxy Server or a
dedicated device. The Rule Maker therefore needs to use a protocol
to create, modify and delete the authorization policies defined in
this document. Such a protocol is available with the Extensible
Markup Language (XML) Configuration Access Protocol (XCAP) [RFC4825].
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4. Condition Elements
This section describes the additional enhancements of the conditions-
part of the rule. This document inherits the Common Policy
functionality, including <identity>, <validity>, and <sphere>
conditions.
Note that, as discussed in [RFC4745], a permission document applies
to a translation if all the expressions in its conditions part
evaluate to TRUE.
4.1. Identity
Although the <identity> element is defined in [RFC4745], that
specification indicates that the specific usages of the framework
document need to define details that are protocol and usage specific.
In particular, it is necessary for a usage of the common policy
framework to:
o Define acceptable means of authentication.
o Define the procedure for representing the identity as a URI or IRI
[RFC3987].
This sub-section defines those details for systems based on
[RFC3856].
4.1.1. Acceptable Forms of Authentication
When used with SIP, a request is considered authenticated if one of
the following techniques is used:
SIP Digest:
The proxy has authenticated the sender using SIP [RFC3261] digest
authentication [RFC2617]. However, if the anonymous
authentication described on page 194 of RFC 3261 [RFC3261] was
used, the sender is not considered authenticated.
Asserted Identity:
If a request contains a P-Asserted-ID header field [RFC3325] and
the request is coming from a trusted element, the sender is
considered authenticated.
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Cryptographically Verified Identity:
If a request contains an Identity header field as defined in
[RFC4474], and it validates the From header field of the request,
the request is considered to be authenticated. Note that this is
true even if the request contained a From header field of the form
sip:anonymous@example.com. As long as the signature verifies that
the request legitimately came from this identity, it is considered
authenticated.
An anonymous From header field with RFC 4474 [RFC4474] is considered
authenticated, while anonymous digest is not considered
authenticated, because the former still involves the usage of an
actual username and credential as part of an authentication operation
in the originating domain.
4.1.2. Computing a URI for the Sender
For messages that are authenticated using SIP Digest, the identity of
the sender is set equal to the address of record (AoR) for the user
that has authenticated themselves. The AoR is always a URI, and can
be either a SIP URI or tel URI [RFC3966]. For example, consider the
following "user record" in a database:
SIP AOR: sip:alice@example.com
digest username: ali
digest password: f779ajvvh8a6s6
digest realm: example.com
If the proxy server receives an INVITE, challenges it with the realm
set to "example.com", and the subsequent INVITE contains an
Authorization header field with a username of "ali" and a digest
response generated with the password "f779ajvvh8a6s6", the identity
used in matching operations is "sip:alice@example.com".
For messages that are authenticated using RFC 3325 [RFC3325], the
identity of the sender is equal to the URI in the P-Asserted-ID
header field. If there are multiple values for the P-Asserted-ID
header field (there can be one sip URI and one tel URI [RFC3966]),
then each of them is used for the comparisons outlined in [RFC4745],
and if either of them match a <one> or <except> element, it is
considered a match.
For messages that are authenticated using the SIP Identity mechanism
[RFC4474], identity of the sender is equal to the SIP URI in the From
header field of the request, assuming that the signature in the
Identity header field has been validated.
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In SIP systems, it is possible for a user to have aliases - that is,
there are multiple SIP AoRs "assigned" to a single user. In terms of
this specification, there is no relationship between those aliases.
Each would look like a different user. This will be the consequence
for systems where the sender is in a different domain than the
recipient. However, even if the sender and recipient are in the same
domain, and the proxy server knows that there are aliases for the
sender, these aliases are not mapped to each other or used in any
way.
SIP also allows for anonymous identities. If a message is anonymous
because the digest challenge/response used the "anonymous" username,
the message is considered unauthenticated and will match only an
empty <identity> element. If a message is anonymous because it
contains a Privacy header field [RFC3323], but still contains a
P-Asserted-ID header field, the identity in the P-Asserted-ID header
field is still used in the authorization computations; the fact that
the message was anonymous has no impact on the identity processing.
However, if the message had traversed a trust boundary and the
P-Asserted-ID header field and the Privacy header field had been
removed, the message will be considered unauthenticated when it
arrives at the proxy server. Finally, if a message contained an
Identity header field that was validated, and the From header field
contained a URI of the form sip:anonymous@example.com, then the
sender is considered authenticated, and it will have an identity
equal to sip:anonymous@example.com. Had such an identity been placed
into a <one> or <except> element, there will be a match.
It is important to note that SIP frequently uses both SIP URI and tel
URI [RFC3966] as identifiers, and to make matters more confusing, a
SIP URI can contain a phone number in its user part, in the same
format used in a tel URI. The sender's identity that is a SIP URI
with a phone number will not match the <one> and <except> conditions
whose 'id' is a tel URI with the same number. The same is true in
the reverse. If the sender's identity is a tel URI, this will not
match a SIP URI in the <one> or <except> conditions whose user part
is a phone number. URIs of different schemes are never equivalent.
4.2. Sphere
The <sphere> element is defined in [RFC4745]. However, each
application making use of the common policy specification needs to
determine how the policy server computes the value of the sphere to
be used in the evaluation of the condition.
To compute the value of <sphere>, the proxy server interacts with a
presence server who knows whether at least one of the published
presence documents includes the <sphere> element [RFC4480] as part of
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the person data component [RFC4479], and all of those containing the
element have the same value for it, that is the value used for the
sphere in policy policy processing. If, however, the <sphere>
element was not available to the presence server (and hence not for
the proxy server), or it was present but had inconsistent values, its
value is considered undefined in terms of policy processing.
4.3. SPIT Handling
The <spit-handling> element is a way to react on the execution of
certain SPIT handling mechanisms. For example, a rule might indicate
that a CAPTCHA has to be sent to the sender and the sender
subsequently has to return the result. Depending on the outcome of
the robot test the rules might enforce different actions. This
element provides such a condition capability.
The <spit-handling> condition evaluates to TRUE if any of its child
elements evaluate to TRUE, i.e., the results of the individual child
element are combined using a logical OR.
The <spit-handling> element MAY contain zero or more <challenge>
elements. The <challenge> elements has an attribute 'result' that
either contains "SUCCESS" or "FAILURE".
4.4. Media List
The <media-list> condition evaluates to TRUE if any of its child
elements evaluate to TRUE, i.e., the results of the individual child
element are combined using a logical OR.
The <media-list> element SHOULD include either
o an <all-media-except> element or;
o a list of one or more >media> elements selected from the list of
possible media elements below.
List of possible media elements:
o The <message-session> media element indicating session based
messaging as defined in [I-D.ietf-simple-message-sessions];
o The <pager-mode-message> media element indicating pager mode
message requests as defined in [RFC3428];
o The <file-transfer> media element indicating file transfer as
defined in [I-D.ietf-mmusic-file-transfer-mech];
o The <audio> media element indicating a streaming media type as
defined in [RFC3840];
o The <video> media element indicating a streaming media type as
defined in [RFC3840];
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o Any elements from any other namespaces defining a media element.
The <all-media-except> element MAY include a list of one or more
>media> elements selected from the list of possible >media> elements
above.
The <audio>, <video> and <message-session> elements:
o MAY include the <full-duplex> element indicating that media can be
exchanged in both directions simultaneously;
o MAY include the <half-duplex> element indicating that media can be
exchanged in only one direction at a time.
4.5. Method List
The <method-list> element contains one or more child elements
<method> in order to provide matching capabilities of any SIP method
invoked by the user can be used to filter incoming messages.
The <method-list> condition element evaluates to TRUE if any of its
child elements evaluate to TRUE, i.e., the results of the individual
child element are combined using a logical OR.
4.6. MIME List
The <mime-list> element contains one or more child <mime> child
elements
The <mime-list> condition element evaluates to TRUE if any of its
child elements evaluate to TRUE, i.e., the results of the individual
child element are combined using a logical OR.
4.7. Presence Status
This condition evaluates to TRUE when the called user's current
presence activity status is equal to the value in the <presence-
status> element. Otherwise the condition evaluates to FALSE.
4.8. Rule Deactivated
The <rule-deactivated> condition always evaluates to FALSE. This can
be used to deactivate a rule, without loosing information. By
removing this condition the rule can be activated again.
4.9. Time Period Condition
The <time-period> element allows to make decisions based on the time,
date and timezone. The <time> element may contain the following
attributes:
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tzid:
RFC 2445 [RFC2445] Time Zone Identifier
tzurl:
RFC 2445 [RFC2445] Time Zone URL
dtstart:
Start of interval (RFC 2445 [RFC2445] DATE-TIME)
dtend:
End of interval (RFC 2445 [RFC2445] DATE-TIME)
duration:
Length of interval (RFC 2445 [RFC2445] DURATION)
freq:
Frequency of recurrence ("secondly", "minutely", "hourly",
"daily", "weekly", "monthly", or "yearly")
interval:
How often the recurrence repeats
until:
Bound of recurrence (RFC 2445 [RFC2445] DATE-TIME)
count:
Number of occurrences of recurrence
bysecond:
List of seconds within a minute
byminute:
List of minutes within an hour
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byhour:
List of hours of the day
byday: List of days of the week
bymonthday:
List of days of the month
byyearday:
List of days of the year
byweekno:
List of weeks of the year
bymonth:
List of months of the year
wkstv:
First day of the work week
bysetpos:
List of values within set of events specified
The <time-period> is based on the description in CPL [RFC3880] and
furthemore based closely on the specification of recurring intervals
of time in the Internet Calendaring and Scheduling Core Object
Specification (iCalendar COS), RFC 2445 [RFC2445].
This allows policies to be generated automatically from calendar
books. It also allows us to re-use the extensive existing work
specifying time intervals.
If future standards-track documents are published that update or
obsolete RFC 2445 [RFC2445], any changes or clarifications those
documents make to recurrence handling apply to CPL time-switches as
well.
An algorithm to determine whether an instant falls within a given
recurrence is given in Appendix A of RFC 3880 [RFC3880].
The <time-period> element takes two optional attributes, "tzid" and
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"tzurl", both of which are defined in Sections 4.8.3.1 and 4.8.3.5 of
RFC 2445 [RFC2445]. The "tzid" is the identifying attribute by which
a time zone definition is referenced. If it begins with a forward
slash (solidus), it references a to-be-defined global time zone
registry; otherwise it is locally-defined at the server. The "tzurl"
attribute gives a network location from which an up-to-date VTIMEZONE
definition for the timezone can be retrieved.
While the content of the "tzid" attribute does not begin with a
forward slash are locally defined, it is RECOMMENDED that servers
support at least the naming scheme used by the Olson Time Zone
database [OTZ]. Examples of timezone databases that use the Olson
scheme are the zoneinfo files on most Unix-like systems, and the
standard Java TimeZone class.
Servers SHOULD resolve "tzid" and "tzurl" references to time zone
definitions at the time the policy is uploaded. They MAY
periodically refresh these resolutions to obtain the most up-to-date
definition of a time zone. If a "tzurl" becomes invalid, servers
SHOULD remember the most recent valid data retrieved from the URL.
If a script is uploaded with a "tzid" and "tzurl" which the CPL
server does not recognize or cannot resolve, it SHOULD diagnose and
reject this at script upload time. If neither "tzid" nor "tzurl" are
present, all non-UTC times within this time switch should be
interpreted as being "floating" times, i.e., that they are specified
in the local timezone of the CPL server.
Because of daylight-savings-time changes over the course of a
year, it is necessary to specify time switches in a given
timezone. UTC offsets are not sufficient, or a time-of-day
routing rule which held between 9 am and 5 pm in the eastern
United States would start holding between 8 am and 4 pm at the end
of October.
The developers of tools used creating policy documents should be
careful to handle correctly the intervals when local time is
discontinuous, at the beginning or end of daylight-savings time.
Note especially that some times may occur more than once when clocks
are set back. The algorithm in Appendix A of RFC 3880 [RFC3880] is
believed to handle this correctly.
The <time> element specifies a list of periods. They have two
required attributes a:
o "dtstart", which specifies the beginning of the first period of
the list,
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o and exactly one of "dtend" or "duration", which specify the ending
time or the duration of the period, respectively.
The "dtstart" and "dtend" attributes are formatted as iCalendar COS
DATE-TIME values, as specified in Section 4.3.5 of RFC 2445
[RFC2445]. Only floating or UTC times can be used with time zones.
The "duration" attribute is given as an iCalendar COS DURATION
parameter, as specified in section 4.3.6 of RFC 2445 [RFC2445]. Both
the DATE-TIME and the DURATION syntaxes are subsets of the
corresponding syntaxes from ISO 8601 [ISO8601].
For a recurring interval, the "duration" attribute MUST be small
enough such that subsequent intervals do not overlap. For non-
recurring intervals, durations of any positive length are permitted.
Zero-length and negative-length durations are not allowed.
If no other parameters are specified, a <time> element indicates only
a single period of time. More complicated sets of period intervals
are constructed as recurrences. A recurrence is specified by
including the "freq" attribute, which indicates the type of
recurrence rule. Parameters other than "dtstart", "dtend", and
"duration" SHOULD NOT be specified unless "freq" is present, though
servers SHOULD accept rules with such parameters present, and ignore
the other parameters.
The "freq" parameter takes one of the following values: "secondly",
to specify repeating periods based on an interval of a second or
more, "minutely", to specify repeating periods based on an interval
of a minute or more, "hourly", to specify repeating periods based on
an interval of an hour or more, "daily", to specify repeating periods
based on an interval of a day or more, "weekly", to specify repeating
periods based on an interval of a week or more, "monthly", to specify
repeating periods based on an interval of a month or more, and
"yearly", to specify repeating periods based on an interval of a year
or more. These values are not case-sensitive.
The "interval" attribute contains a positive integer representing how
often the recurrence rule repeats. The default value is "1", meaning
every second for a "secondly" rule, every minute for a "minutely"
rule, every hour for an "hourly" rule, every day for a "daily" rule,
every week for a "weekly" rule, every month for a "monthly" rule, and
every year for a "yearly" rule.
The "until" attribute defines an iCalendar COS DATE or DATE-TIME
value which bounds the recurrence rule in an inclusive manner. If
the value specified by "until" is synchronized with the specified
recurrence, this date or date-time becomes the last instance of the
recurrence. If specified as a date-time value, then it MUST be
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specified in UTC time format. If not present, and the "count"
parameter is not also present, the recurrence is considered to repeat
forever.
The "count" attribute defines the number of occurrences at which to
range-bound the recurrence. The "dtstart" attribute counts as the
first occurrence. The "until" and "count" attribute MUST NOT occur
in the same <time> element.
The "bysecond" attribute specifies a comma-separated list of seconds
within a minute. Valid values are 0 to 59. The "byminute" attribute
specifies a comma-separated list of minutes within an hour. Valid
values are 0 to 59. The "byhour" attribute specifies a comma-
separated list of hours of the day. Valid values are 0 to 23.
The "byday" attribute specifies a comma-separated list of days of the
week. "MO" indicates Monday, "TU" indicates Tuesday, "WE" indicates
Wednesday, "TH" indicates Thursday, "FR" indicates Friday, "SA"
indicates Saturday, and "SU" indicates Sunday. These values are not
case-sensitive.
Each "byday" value can also be preceded by a positive (+n) or
negative (-n) integer. If present, this indicates the nth occurrence
of the specific day within the "monthly" or "yearly" recurrence. For
example, within a "monthly" rule, +1MO (or simply 1MO) represents the
first Monday within the month, whereas -1MO represents the last
Monday of the month. If an integer modifier is not present, it means
all days of this type within the specified frequency. For example,
within a "monthly" rule, MO represents all Mondays within the month.
The "bymonthday" attribute specifies a comma-separated list of days
of the month. Valid values are 1 to 31 or -31 to -1. For example,
-10 represents the tenth to the last day of the month.
The "byyearday" attribute specifies a comma-separated list of days of
the year. Valid values are 1 to 366 or -366 to -1. For example, -1
represents the last day of the year (December 31st) and -306
represents the 306th to the last day of the year (March 1st).
The "byweekno" attribute specifies a comma-separated list of ordinals
specifying weeks of the year. Valid values are 1 to 53 or -53 to -1.
This corresponds to weeks according to week numbering as defined in
ISO 8601 [ISO8601]. A week is defined as a seven day period,
starting on the day of the week defined to be the week start (see
"wkst"). Week number one of the calendar year is the first week
which contains at least four (4) days in that calendar year. This
parameter is only valid for "yearly" rules. For example, 3
represents the third week of the year.
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Note: Assuming a Monday week start, week 53 can only occur when
January 1 is a Thursday or, for leap years, if January 1 is a
Wednesday.
The "bymonth" attribute specifies a comma-separated list of months of
the year. Valid values are 1 to 12.
The "wkst" attribute specifies the day on which the work week starts.
Valid values are "MO", "TU", "WE", "TH", "FR", "SA" and "SU". This
is significant when a "weekly" recurrence has an interval greater
than 1, and a "byday" parameter is specified. This is also
significant in a "yearly" recurrence when a "byweekno" parameter is
specified. The default value is "MO", following ISO 8601 [ISO8601].
The "bysetpos" attribute specifies a comma-separated list of values
which corresponds to the nth occurrence within the set of events
specified by the rule. Valid values are 1 to 366 or -366 to -1. It
MUST only be used in conjunction with another byxxx attribute. For
example, "the last work day of the month" could be represented as:
<time dtstart="19970105T083000"
freq="monthly"
byday="MO,TU,WE,TH,FR"
bysetpos="-1"
/>
Each "bysetpos" value can include a positive (+n) or negative (-n)
integer. If present, this indicates the nth occurrence of the
specific occurrence within the set of events specified by the rule.
If byxxx attribute values are found which are beyond the available
scope (i.e., bymonthday="30" in February), they are simply ignored.
Byxxx attribute modify the recurrence in some manner. Byxxx rule
parts for a period of time which is the same or greater than the
frequency generally reduce or limit the number of occurrences of the
recurrence generated. For example, freq="daily" bymonth="1" reduces
the number of recurrence instances from all days (if the "bymonth"
attribute is not present) to all days in January. Byxxx attribute
for a period of time less than the frequency generally increase or
expand the number of occurrences of the recurrence. For example,
freq="yearly" bymonth="1,2" increases the number of days within the
yearly recurrence set from 1 (if "bymonth" parameter is not present)
to 2.
If multiple Byxxx attribute are specified, then after evaluating the
specified "freq" and "interval" attribute, the Byxxx attribute are
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applied to the current set of evaluated occurrences in the following
order: "bymonth", "byweekno", "byyearday", "bymonthday", "byday",
"byhour", "byminute", "bysecond", and "bysetpos"; then "count" and
"until" are evaluated.
Here is an example of evaluating multiple Byxxx attribute.
<time dtstart="19970105T083000"
duration="10M"
freq="yearly"
interval="2"
bymonth="1"
byday="SU"
byhour="8,9"
byminute="30">
/>
First, the interval="2" would be applied to freq="yearly" to arrive
at "every other year." Then, bymonth="1" would be applied to arrive
at "every January, every other year." Then, byday="SU" would be
applied to arrive at "every Sunday in January, every other year."
Then, byhour="8,9" would be applied to arrive at "every Sunday in
January at 8 AM and 9 AM, every other year." Then, byminute="30"
would be applied to arrive at "every Sunday in January at 8:30 AM and
9:30 AM, every other year." Then the second is derived from
"dtstart" to end up in "every Sunday in January from 8:30:00 AM to
8:40:00 AM, and from and 9:30:00 AM to 9:40:00 AM, every other year."
Similarly, if the "byminute", "byhour", "byday", "bymonthday", or
"bymonth" parameter were missing, the appropriate minute, hour, day,
or month would have been retrieved from the "dtstart" parameter.
The iCalendar COS RDATE, EXRULE, and EXDATE recurrence rules are not
specifically mapped to components of the <time-period> element.
Equivalent functionality to the exception rules can be attained by
using the ordering of rules to exclude times using earlier rules.
Section 4.4.1 of [RFC3880] provides some background of the
differences to iCalendar and implementation issues.
5. Actions
As stated in [RFC4474], conditions are the 'if'-part of rules,
whereas actions and transformations form their 'then'-part. The
actions and transformations parts of a rule determine which
operations the proxy server MUST execute on receiving a connection
request attempt that matches all conditions of this rule. Actions
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and transformations permit certain operations to be executed.
5.1. Execute Action
The <handling> element allows a couple of actions to be triggered,
namely
Block Action:
The block action states that this specific connection request MUST
NOT be forwarded and a "403" forbidden message MUST be sent to the
sender of the message.
Allow Action:
The Allow action states that this specific connection request MUST
be forwarded.
Furthermore, a couple of further mechanisms, such as computational
puzzles mechanism (described in [I-D.jennings-sip-hashcash]), the
consent framework (described in [I-D.ietf-sip-consent-framework])
etc. can be executed. Each mechanism needs to register a URI and the
value of URI is placed in this field.
[Editior's Note: For editorial purposes the schema currently lists a
few examples but in a non-URI format. When solution documents define
these URIs then they can be used with this document.]
5.2. Forward To
The action supported in this section is forwarding of calls with the
<forward-to> element that contains the following child elements:
target:
Specifies the address of the forwarding rule. It should be a
valid SIP URI (RFC 3261 [RFC3261]) or TEL URI (RFC 3966
[RFC3966]).
6. Examples
This section provides a few examples for policy rules defined in this
document. The example policy shows three rules with the rule id r1 -
r4.
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Rule r1 matches for authenticated identities from the domain
"example.com", "example.org" and the single identity
"sip:bob@good.example.net". For these conditions SIP messages are
forwarded to the SIP UA as indicated with the <handling> element.
Rule r2 indicates that for SIP messages where the identity has not
been verifiable the hash cash mechanism
[I-D.jennings-sip-hashcash] and CAPTCHAs
[I-D.tschofenig-sipping-captcha] are applied (see the 'hashcash'
and the 'captcha' token in the <execute> element).
Rule r3 contains the <spit-handling> element with the <challenge>
child element. This rule evaluates to TRUE if the sender returned
a valid hash cash or a valid CAPTCHA result. The action part of
the rule indicates that the call is then forwarded to the
answering machine, namely sip:answering-machine@home.foo-bar.com.
Rule r4 blocks the call if sender provided a wrong hash cash or
CAPTCHA result.
Rule r1 and r2 are valid only from 2007-01-01T01:00:00+01:00 to 2007-
07-01T24:00:00+01:00.
<?xml version="1.0" encoding="UTF-8"?>
<ruleset xmlns="urn:ietf:params:xml:ns:common-policy"
xmlns:spit="urn:ietf:params:xml:ns:spit-policy"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<rule id="r1">
<conditions>
<identity>
<one id="sip:bob@good.example.net"/>
<many domain="example.com"/>
<many domain="example.org"/>
</identity>
<validity>
<from>2007-01-01T01:00:00+01:00</from>
<until>2007-07-01T24:00:00+01:00</until>
</validity>
</conditions>
<actions>
<spit:execute>allow</spit:execute>
</actions>
<transformations/>
</rule>
<rule id="r2">
<conditions>
<validity>
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<from>2007-01-01T01:00:00+01:00</from>
<until>2007-07-01T24:00:00+01:00</until>
</validity>
</conditions>
<actions>
<spit:execute>hashcash</spit:execute>
<spit:execute>captcha</spit:execute>
</actions>
<transformations/>
</rule>
<rule id="r3">
<conditions>
<spit:spit-handling>
<challenge result="SUCCESS">hashcash</challenge>
<challenge result="SUCCESS">captcha</challenge>
</spit:spit-handling>
</conditions>
<actions>
<spit:forward-to>
<target>sip:answering-machine@home.foo-bar.com
</target>
</spit:forward-to>
</actions>
<transformations/>
</rule>
<rule id="r4">
<conditions>
<spit:spit-handling>
<challenge result="FAILURE">hashcash</challenge>
<challenge result="FAILURE">captcha</challenge>
</spit:spit-handling>
</conditions>
<actions>
<spit:execute>block</spit:execute>
</actions>
<transformations/>
</rule>
</ruleset>
7. XML Schema
This section contains the XML schema that defines the policies schema
described in this document. This schema extends the Common Policy
schema (see [RFC4474]) by introducing new members of the <condition>
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and <action> elements.
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema targetNamespace="urn:ietf:params:xml:ns:spit-policy"
xmlns:spit="urn:ietf:params:xml:ns:spit-policy"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<!-- This import brings in the XML language attribute xml:lang-->
<xs:import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/2001/xml.xsd"/>
<xs:import namespace="urn:ietf:params:xml:ns:common-policy"/>
<!-- Conditions -->
<xs:element name="method-list">
<xs:complexType>
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:sequence>
<xs:element name="method" type="spit:method-type"
minOccurs="0" maxOccurs="unbounded"/>
<xs:any namespace="##other" processContents="lax"
minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:element name="spit-handling">
<xs:complexType>
<xs:sequence>
<xs:element name="challenge" type="spit:challenge-type"
minOccurs="0" maxOccurs="unbounded"/>
<xs:any namespace="##other" processContents="lax"
minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="result" use="required">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="SUCCESS"/>
<xs:enumeration value="FAILURE"/>
</xs:restriction>
</xs:simpleType>
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</xs:attribute>
</xs:complexType>
</xs:element>
<xs:element name="mime-list">
<xs:complexType>
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:sequence>
<xs:element name="mime" type="spit:mime-type"
minOccurs="0" maxOccurs="unbounded"/>
<xs:any namespace="##other" processContents="lax"
minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:element name="media-list">
<xs:complexType>
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:sequence>
<xs:element name="media" type="spit:media-type"
minOccurs="0" maxOccurs="unbounded"/>
<xs:any namespace="##other" processContents="lax"
minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:element name="rule-deactivated"
type="spit:empty-element-type"/>
<xs:complexType name="empty-element-type"/>
<xs:element name="presence-status"
type="spit:presence-status-activity-type"/>
<xs:simpleType name="presence-status-activity-type">
<xs:restriction base="xs:string"/>
</xs:simpleType>
<xs:simpleType name="media-type">
<xs:restriction base="xs:string"/>
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</xs:simpleType>
<xs:simpleType name="challenge-type">
<xs:restriction base="xs:string"/>
</xs:simpleType>
<xs:simpleType name="mime-type">
<xs:restriction base="xs:string"/>
</xs:simpleType>
<xs:simpleType name="method-type">
<xs:restriction base="xs:string"/>
</xs:simpleType>
<xs:element name="time-period" type="spit:TimeSwitchType"/>
<xs:simpleType name="YearDayType">
<xs:union>
<xs:simpleType>
<xs:restriction base="xs:integer">
<xs:minInclusive value="-366"/>
<xs:maxInclusive value="-1"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType>
<xs:restriction base="xs:integer">
<xs:minInclusive value="1"/>
<xs:maxExclusive value="366"/>
</xs:restriction>
</xs:simpleType>
</xs:union>
</xs:simpleType>
<xs:simpleType name="DayType">
<xs:restriction base="xs:NMTOKEN">
<xs:pattern value="[m|M][o|O]"/>
<xs:pattern value="[t|T][u|U]"/>
<xs:pattern value="[w|W][e|E]"/>
<xs:pattern value="[t|T][h|H]"/>
<xs:pattern value="[f|F][r|R]"/>
<xs:pattern value="[s|S][a|A]"/>
<xs:pattern value="[s|S][u|U]"/>
</xs:restriction>
</xs:simpleType>
<xs:complexType name="TimeType">
<xs:annotation>
<xs:documentation>Exactly one of the two attributes
"dtend" and "duration" must occur. None of
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the attributes following freq are meaningful
unless freq appears. </xs:documentation>
</xs:annotation>
<xs:attribute name="dtstart" type="xs:string" use="required">
<xs:annotation>
<xs:documentation>RFC 2445 DATE-TIME</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="dtend" type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>RFC 2445 DATE-TIME</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="duration" type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>RFC 2445 DURATION</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="freq" type="spit:FreqType" use="optional"/>
<xs:attribute name="interval"
type="xs:positiveInteger" default="1"/>
<xs:attribute name="until" type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>RFC 2445 DATE-TIME</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="count"
type="xs:positiveInteger" use="optional"/>
<xs:attribute name="bysecond"
type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>Comma-separated list of
seconds within a minute. Valid values are 0 to
59.</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="byminute"
type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>Comma-separated list of
minutes within an hour. Valid values are 0 to
59.</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="byhour" type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>Comma-separated list of
hours of the day. Valid values are 0 to
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23.</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="byday" type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>Comma-separated list of days of the week.
Valid values are "MO", "TU",
"WE", "TH", "FR", "SA" and "SU". These values are
not case-sensitive. Each can be preceded
by a positive (+n) or negative (-n) integer.
</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="bymonthday" type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>Comma-separated list of days of the month.
Valid values are 1 to 31 or -31
to -1.</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="byyearday" type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>Comma-separated list of days of the year.
Valid values are 1 to 366 or
-366 to -1.</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="byweekno" type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>Comma-separated list of ordinals
specifying weeks of the year. Valid
values are 1 to 53 or -53 to -1.</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="bymonth" type="xs:string" use="optional">
<xs:annotation>
<xs:documentation>Comma-separated list of months of the year.
Valid values are 1 to
12.</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="wkst" type="spit:DayType" default="MO"/>
<xs:attribute name="bysetpos" type="spit:YearDayType"/>
<xs:anyAttribute namespace="##any" processContents="lax"/>
</xs:complexType>
<xs:simpleType name="TZIDType">
<xs:restriction base="xs:string"/>
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</xs:simpleType>
<xs:simpleType name="TZURLType">
<xs:restriction base="xs:anyURI"/>
</xs:simpleType>
<xs:complexType name="TimeSwitchType">
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:sequence>
<xs:element name="time" type="spit:TimeType"
minOccurs="1" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="tzid" type="spit:TZIDType"/>
<xs:attribute name="tzurl" type="spit:TZURLType"/>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
<xs:simpleType name="FreqType">
<xs:restriction base="xs:NMTOKEN">
<xs:pattern value="[s|S][e|E][c|C][o|O][n|N][d|D][l|L][y|Y]"/>
<xs:pattern value="[m|M][i|I][n|N][u|U][t|T][e|E][l|L][y|Y]"/>
<xs:pattern value="[h|H][o|O][u|U][r|R][l|L][y|Y]"/>
<xs:pattern value="[d|D][a|A][i|I][l|L][y|Y]"/>
<xs:pattern value="[w|W][e|E][e|E][k|K][l|L][y|Y]"/>
<xs:pattern value="[m|M][o|N][n|N][t|T][h|H][l|L][y|Y]"/>
<xs:pattern value="[y|Y][e|E][a|A][r|R][l|L][y|Y]"/>
</xs:restriction>
</xs:simpleType>
<!-- Action -->
<xs:element name="execute">
<xs:simpleType>
<xs:restriction base="xs:string">
</xs:restriction>
</xs:simpleType>
</xs:element>
<xs:element name="forward-to" type="spit:forward-to-type"/>
<xs:complexType name="forward-to-type">
<xs:sequence>
<xs:element name="target" type="spit:target-type"/>
<xs:any namespace="##other" processContents="lax"
minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
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<xs:simpleType name="target-type">
<xs:restriction base="xs:anyURI"/>
</xs:simpleType>
</xs:schema>
8. XCAP USAGE
The following section defines the details necessary for clients to
manipulate SPIT authorization documents from a server using XCAP.
8.1. Application Unique ID
XCAP requires application usages to define a unique application usage
ID (AUID) in either the IETF tree or a vendor tree. This
specification defines the "Spit-policy" AUID within the IETF tree,
via the IANA registration in Section 9.
8.2. XML Schema
XCAP requires application usages to define a schema for their
documents. The schema for Anti-SPIT authorization documents is
described in Section 7.
8.3. Default Namespace
XCAP requires application usages to define the default namespace for
their documents. The default namespace is
urn:ietf:params:xml:ns:spit-policy.
8.4. MIME Type
XCAP requires application usages to defined the MIME type for
documents they carry. Anti-SPIT privacy authorization documents
inherit the MIME type of Common Policy documents, application/
auth-policy+xml.
8.5. Validation Constraints
This specification does not define additional constraints.
8.6. Data Semantics
This document discusses the semantics of Anti-SPIT authorization.
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8.7. Naming Conventions
When a SIP Proxy receives a SIP message to route it towards to a
specific user foo, it will look for all documents within
http://[xcaproot]/spit-policy/users/foo, and use all documents found
beneath that point to guide authorization policy.
8.8. Resource Interdependencies
This application usage does not define additional resource
interdependencies.
8.9. Authorization Policies
This application usage does not modify the default XCAP authorization
policy, which is that only a user can read, write or modify his/her
own documents. A server can allow privileged users to modify
documents that they do not own, but the establishment and indication
of such policies is outside the scope of this document.
9. IANA Considerations
There are several IANA considerations associated with this
specification.
9.1. Anti-SPIT Policy XML Schema Registration
URI: urn:ietf:params:xml:schema:spit-policy
Registrant Contact: Hannes Tschofenig
(hannes.tschofenig@siemens.com).
XML: The XML schema to be registered is contained in Section 7. Its
first line is
<?xml version="1.0" encoding="UTF-8"?>
and its last line is
</xs:schema>
9.2. Anti-SPIT Policy Namespace Registration
URI: urn:ietf:params:xml:ns:spit-policy
Registrant Contact: Hannes Tschofenig
(hannes.tschofenig@siemens.com).
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XML:
9.3. XCAP Application Usage ID
This section registers an XCAP Application Usage ID (AUID) according
to the IANA procedures defined in [RFC4825].
Name of the AUID: spit-policy
Description: The rules defined in this documents describe ways to
react on unwanted and unsolicted communication (including Spam).
10. Security Considerations
This document aims to make it simple for users to influence the
behavior of SIP message routing with an emphasis on SPIT prevention.
This document proposes a strawman proposal for conditions and actions
that might be useful when it comes to allowing a UA to tell its
proxies which messages it wants to receive and what tasks it wants
those proxies to perform before sending a SIP request to the UA.
A couple of requirements are described in
[I-D.froment-sipping-spit-requirements] and a general discussion
about the available solution mechanisms is available with
[I-D.ietf-sipping-spam]. This document offers the ability to glue
the different solution pieces together.
Since this document uses the Common Policy framework it also inherits
its capabilities, including the combining permission algorithm that
is applied when multiple rules fire. Unauthorized access to the
user's Anti-SPIT rules must be prevented to avoid the introduction of
security vulnerabilities.
11. Contributors
We would like to thank Mayutan Arumaithurai
(mayutan.arumaithurai@gmail.com) for his work on this document.
12. Acknowledgments
We would like to thank
o Jonathan Rosenberg, David Schwartz and Dan York for sharing their
thoughts with us before the first version of this document was
written.
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o Miguel Garcia and Remi Denis-Courmont for their review comments to
the -00 version.
o Mayutan Arumaithurai for his editing help with the -00 version.
o Poikselka Miikka, Isomaki Markus, Jari Mutikainen, Jean-Marie
Stupka, and Antti Laurila for their comments and for pointing us
to specifications outside the IETF.
This document intentionally re-uses concept from existing documents.
In particular, we reused
o ideas from SIEVE [RFC3028], a mail filtering language.
o the text in Section 4.9 from the Call Processing Language (CPL)
[RFC3880]. The difference between CPL and this document is that
CPL has a more procedural approach, while this proposal is
matching-based.
o text in Section 4.1 from [I-D.ietf-simple-presence-rules].
o content of Section 5.2, Section 4.8 and Section 4.7 is reused from
[ETSI-TS-183-004].
o text of Section 4.4 from [OMA-TS-XDM_Shared_Policy]
13. References
13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[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.
[RFC3323] Peterson, J., "A Privacy Mechanism for the Session
Initiation Protocol (SIP)", RFC 3323, November 2002.
[RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private
Extensions to the Session Initiation Protocol (SIP) for
Asserted Identity within Trusted Networks", RFC 3325,
November 2002.
[RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
and D. Gurle, "Session Initiation Protocol (SIP) Extension
for Instant Messaging", RFC 3428, December 2002.
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[RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
"Indicating User Agent Capabilities in the Session
Initiation Protocol (SIP)", RFC 3840, August 2004.
[RFC3856] Rosenberg, J., "A Presence Event Package for the Session
Initiation Protocol (SIP)", RFC 3856, August 2004.
[RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
RFC 3966, December 2004.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[RFC4412] Schulzrinne, H. and J. Polk, "Communications Resource
Priority for the Session Initiation Protocol (SIP)",
RFC 4412, February 2006.
[RFC4474] Peterson, J. and C. Jennings, "Enhancements for
Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 4474, August 2006.
[RFC4479] Rosenberg, J., "A Data Model for Presence", RFC 4479,
July 2006.
[RFC4480] Schulzrinne, H., Gurbani, V., Kyzivat, P., and J.
Rosenberg, "RPID: Rich Presence Extensions to the Presence
Information Data Format (PIDF)", RFC 4480, July 2006.
[RFC4745] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J.,
Polk, J., and J. Rosenberg, "Common Policy: A Document
Format for Expressing Privacy Preferences", RFC 4745,
February 2007.
[RFC4825] Rosenberg, J., "The Extensible Markup Language (XML)
Configuration Access Protocol (XCAP)", RFC 4825, May 2007.
13.2. Informative References
[ETSI-TS-183-004]
ETSI, "TS 183 004, Telecommunications and Internet
converged Services and Protocols for Advanced Networking
(TISPAN); PSTN/ISDN simulation services: Communication
Diversion (CDIV); Protocol specification", 2007.
[I-D.froment-sipping-spit-requirements]
Froment, T., "Requirements for Authorization Policies to
tackle Spam for Internet Telephony and Unwanted Traffic",
draft-froment-sipping-spit-requirements-00 (work in
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progress), June 2007.
[I-D.ietf-ecrit-service-urn]
Schulzrinne, H., "A Uniform Resource Name (URN) for
Services", draft-ietf-ecrit-service-urn-06 (work in
progress), March 2007.
[I-D.ietf-mmusic-file-transfer-mech]
Garcia-Martin, M., "A Session Description Protocol (SDP)
Offer/Answer Mechanism to Enable File Transfer",
draft-ietf-mmusic-file-transfer-mech-03 (work in
progress), June 2007.
[I-D.ietf-simple-message-sessions]
Campbell, B., "The Message Session Relay Protocol",
draft-ietf-simple-message-sessions-19 (work in progress),
February 2007.
[I-D.ietf-simple-presence-rules]
Rosenberg, J., "Presence Authorization Rules",
draft-ietf-simple-presence-rules-09 (work in progress),
March 2007.
[I-D.ietf-sip-consent-framework]
Rosenberg, J., "A Framework for Consent-Based
Communications in the Session Initiation Protocol (SIP)",
draft-ietf-sip-consent-framework-02 (work in progress),
July 2007.
[I-D.ietf-sipping-spam]
Jennings, C. and J. Rosenberg, "The Session Initiation
Protocol (SIP) and Spam", draft-ietf-sipping-spam-04 (work
in progress), February 2007.
[I-D.jennings-sip-hashcash]
Jennings, C., "Computational Puzzles for SPAM Reduction in
SIP", draft-jennings-sip-hashcash-05 (work in progress),
June 2007.
[I-D.mahy-iptel-cpc]
Mahy, R., "The Calling Party's Category tel URI
Parameter", draft-mahy-iptel-cpc-06 (work in progress),
March 2007.
[I-D.rosenberg-sipping-service-identification]
Rosenberg, J., "Identification of Communications Services
in the Session Initiation Protocol (SIP)",
draft-rosenberg-sipping-service-identification-02 (work in
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progress), May 2007.
[I-D.schubert-sipping-saml-cpc]
Schubert, S., "Conveying CPC using the SAML",
draft-schubert-sipping-saml-cpc-02 (work in progress),
July 2006.
[I-D.schwartz-sipping-spit-saml]
Schwartz, D., "SPAM for Internet Telephony (SPIT)
Prevention using the Security Assertion Markup Language
(SAML)", draft-schwartz-sipping-spit-saml-01 (work in
progress), June 2006.
[I-D.tschofenig-sipping-captcha]
Tschofenig, H. and E. Leppanen, "Completely Automated
Public Turing Test to Tell Computers and Humans Apart
(CAPTCHA) based Robot Challenges for the Session
Initiation Protocol (SIP)",
draft-tschofenig-sipping-captcha-00 (work in progress),
July 2007.
[I-D.tschofenig-sipping-framework-spit-reduction]
Tschofenig, H., "A Framework for Reducing Spam for
Internet Telephony",
draft-tschofenig-sipping-framework-spit-reduction-00 (work
in progress), June 2007.
[ISO8601] ISO (International Organization for Standardization),
""Data elements and interchange formats -- Information
interchange -- Representation of dates and times", ISO
Standard ISO 8601:2000(E), International Organization for
Standardization, Geneva, Switzerland,", December 2000.
[OMA-TS-XDM_Shared_Policy]
Open Mobile Alliance, "Shared Policy XDM Specification",
2007.
[OTZ] Eggert, P., "Sources for Time Zone and Daylight Saving
Time Data, available at
http://www.twinsun.com/tz/tz-link.htm", 2007.
[RFC2445] Dawson, F. and Stenerson, D., "Internet Calendaring and
Scheduling Core Object Specification (iCalendar)",
RFC 2445, November 1998.
[RFC3028] Showalter, T., "Sieve: A Mail Filtering Language",
RFC 3028, January 2001.
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[RFC3266] Olson, S., Camarillo, G., and A. Roach, "Support for IPv6
in Session Description Protocol (SDP)", RFC 3266,
June 2002.
[RFC3880] Lennox, J., Wu, X., and H. Schulzrinne, "Call Processing
Language (CPL): A Language for User Control of Internet
Telephony Services", RFC 3880, October 2004.
Authors' Addresses
Hannes Tschofenig
Nokia Siemens Networks
Otto-Hahn-Ring 6
Munich, Bavaria 81739
Germany
Email: Hannes.Tschofenig@nsn.com
URI: http://www.tschofenig.com
Dan Wing
Cisco
Phone:
Email: dwing@cisco.com
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
Email: hgs@cs.columbia.edu
URI: http://www.cs.columbia.edu
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Thomas Froment
Alcatel-Lucent
1, rue Ampere - BP 80056
Massy, Paris 91302
France
Email: Thomas.Froment@alcatel-lucent.fr
Geoffrey Dawirs
University of Namur
21, rue Grandgagnage
Namur B-5000
Belgique
Email: gdawirs@gdawirs.be
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Tschofenig, et al. Expires January 9, 2008 [Page 36]
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