One document matched: draft-ietf-sipcore-info-events-01.txt
Differences from draft-ietf-sipcore-info-events-00.txt
SIPCORE E. Burger
Internet-Draft NeuStar, Inc.
Obsoletes: RFC 2976 H. Kaplan
(if approved) Acme Packet
Expires: April 2, 2010 C. Holmberg
Ericsson
September 29, 2009
Session Initiation Protocol (SIP) INFO Method and Package Framework
draft-ietf-sipcore-info-events-01
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
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Abstract
This document provides new semantics for the SIP INFO method of RFC
2976. These new semantics defined here are fully backwards
compatible with the old semantics. Core to the new semantics is a
mechanism for defining, indicating support of, and exchanging Info
Packages that use the INFO method. Applications that need to
exchange application information within a SIP invite usage dialog
(RFC 5057), can use these Info Packages. This document replaces RFC
2976 but still allows existing legacy INFO usages as defined in RFC
2976.
Conventions Used in this Document
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].
The terminology in this document conforms to the Internet Security
Glossary [RFC4949].
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Info Package Support . . . . . . . . . . . . . . . . . . . . . 7
3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. User Agent Behavior . . . . . . . . . . . . . . . . . . . 7
3.3. Package Versioning . . . . . . . . . . . . . . . . . . . . 8
3.4. REGISTER Processing . . . . . . . . . . . . . . . . . . . 8
3.5. OPTIONS Processing . . . . . . . . . . . . . . . . . . . . 8
3.6. Example . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. The INFO Method . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. INFO Request . . . . . . . . . . . . . . . . . . . . . . . 10
4.3. INFO Request Message Body . . . . . . . . . . . . . . . . 11
4.4. INFO Response . . . . . . . . . . . . . . . . . . . . . . 12
4.5. INFO Response Message Body . . . . . . . . . . . . . . . . 12
4.6. Order of Delivery . . . . . . . . . . . . . . . . . . . . 12
5. Formal INFO Method Definition . . . . . . . . . . . . . . . . 13
5.1. INFO Method . . . . . . . . . . . . . . . . . . . . . . . 13
5.2. INFO Header Fields . . . . . . . . . . . . . . . . . . . . 14
5.2.1. Info-Package header field . . . . . . . . . . . . . . 15
5.2.2. Recv-Info header field . . . . . . . . . . . . . . . . 15
6. Legacy INFO Usage . . . . . . . . . . . . . . . . . . . . . . 15
7. Info Package Requirements . . . . . . . . . . . . . . . . . . 16
7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 16
7.3. Info Package Name . . . . . . . . . . . . . . . . . . . . 17
7.4. Info Package Parameters . . . . . . . . . . . . . . . . . 17
7.5. SIP Option Tags . . . . . . . . . . . . . . . . . . . . . 17
7.6. INFO Message Bodies . . . . . . . . . . . . . . . . . . . 17
7.7. Info Package Usage Restrictions . . . . . . . . . . . . . 17
7.8. Rate of INFO Requests . . . . . . . . . . . . . . . . . . 18
7.9. IANA Registrations . . . . . . . . . . . . . . . . . . . . 18
7.10. Security Considerations . . . . . . . . . . . . . . . . . 18
7.11. Application Procedures . . . . . . . . . . . . . . . . . . 19
7.12. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 19
8. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
9.1. Update to Registration of SIP INFO Method . . . . . . . . 20
9.2. Registration of the Info-Package Header Field . . . . . . 20
9.3. Registration of the Recv-Info Header Field . . . . . . . . 20
9.4. Creation of the Info Packages Registry . . . . . . . . . . 20
9.5. Registration of the Info-Package Content-Disposition . . . 21
9.6. SIP Response Code 469 Registration . . . . . . . . . . . . 21
10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
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10.1. Simple Info Package . . . . . . . . . . . . . . . . . . . 21
10.2. Multipart INFO Example . . . . . . . . . . . . . . . . . . 22
11. Modifications to SIP Change Process . . . . . . . . . . . . . 23
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
12.1. Normative References . . . . . . . . . . . . . . . . . . . 24
12.2. Informative References . . . . . . . . . . . . . . . . . . 25
Appendix A. Info Package Considerations . . . . . . . . . . . . . 27
A.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 27
A.2. Appropriateness of Info Package Usage . . . . . . . . . . 27
A.3. Dialog Fate Sharing . . . . . . . . . . . . . . . . . . . 27
A.4. INFO Request Rate and Volume . . . . . . . . . . . . . . . 27
A.5. Alternative Mechanisms . . . . . . . . . . . . . . . . . . 28
A.5.1. Alternative SIP signaling plane mechanisms . . . . . . 28
A.5.2. Media Plane Mechanisms . . . . . . . . . . . . . . . . 29
A.5.3. Non-SIP related mechanisms . . . . . . . . . . . . . . 29
Appendix B. Legacy INFO Usages . . . . . . . . . . . . . . . . . 29
B.1. ISUP . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
B.2. QSIG . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
B.3. MSCML . . . . . . . . . . . . . . . . . . . . . . . . . . 30
B.4. MSML . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
B.5. Video Fast Update . . . . . . . . . . . . . . . . . . . . 30
Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 30
Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
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1. Introduction
[RFC3261] defines a mechanism to setup and tear down SIP sessions. A
SIP User Agent (UA) can use the re-INVITE and UPDATE methods during a
session to change characteristics of the session, including media
properties, target information or properties related to the SIP
session timer mechanism [RFC4028].
The purpose of the INFO message [RFC2976] is to carry application
level information between endpoints, using the SIP session signaling
path. Note that the INFO method is not used to update
characteristics of the SIP session, but to allow the applications
which use the SIP session to exchange information.
While the INFO method has been widely adopted for specific
application use cases, such as ISUP and DTMF exchange, [RFC2976] does
not define a mechanisms for SIP UAs to indicate what usages of INFO
they support. In addition, [RFC2976] does not provide a mechanism to
explicitly indicate the type of application for which the INFO
message is used. In some cases it can be determined by the INFO
message body content, but not in a general way.
Example: If the Content-Type is "image/jpeg", the MIME-attached
content is a JPEG image. Still, there are many useful ways a UA can
render an image. The image could be a caller-id picture, a contact
icon, a photo for sharing, and so on. The sender does not know which
image to send to the receiver if the receiver supports an image
content type. Likewise, the receiver does not know the context of an
image the client is sending if the receiver supports receiving more
than one image content type.
Due to the problems described above, the usage of INFO often requires
static configuration about what INFO usages the UAs support, and the
way the handle application information transported in INFO messages.
That has caused a big risk interoperability problems in the industry,
due to undefined content syntax, semantics and UA support of the INFO
messages. Therefore, there is a need for a well defined and
documented description of what the information sent in the INFO is
used for. This situation is identical to the context issue in
Internet Mail [RFC3458].
This document defines a mechanism, using Info Packages, which
provides the possibility for UAs to indicate what INFO usages they
support, and to define content syntax and semantics for the data
transported in the INFO messages. The mechanism allows existing
legacy INFO usages as defined in RFC 2976. New INFO usages MUST use
the mechanism defined in this document.
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Event Packages [RFC3265] perform the role of disambiguating the
context of a message for subscription-based events. The Info Package
mechanisms provides similar functionality for application information
exchange using invite dialog usages [RFC5057].
Note that while Info Packages may be similar to subscription-based
events, there is no formal relationship between this mechanism and
the subscription mechanism.
The Info Package mechanism does not create a separate dialog usage.
INFO messages are always part of, and share the fate of, an invite
dialog usage. INFO message can not be sent as part of other dialog
usages, and they can not be sent outside an existing session.
If a UA supports the Info Package mechanism it indicates, using the
Recv-Info header field which Info Packages it is willing to receive,
on a per-session basis. A UA can indicate a new set of Info Packages
at any time during the lifetime of the invite dialog usage of the
session. A UA can use a "nil" value to indicate that it is not
willing to receive any Info Packages at a certain moment, but that
the UA still supports the Info Package mechanism.
When a UA sends an INFO request, it uses the Info-Package header
field to indicate which Info Package is associated with the request.
Section 3 describes the mechanism to indicate support of Info
Packages.
Section 4 describes the usage of INFO messages.
Section 6 describes legacy usage of INFO, as defined in [RFC2976].
Section 7 describes guidelines on how to define Info Packages. This
document does not define any specific Info Packages.
Annex A provides guidelines and issues to consider when deciding if
usage of Info Packages is the most appropriate mechanism for a
specific use-case.
2. Applicability
This document extends [RFC2976] to include a mechanism to in SIP
messages explicitly indicate the supported Info Packages, and to
explicitly indicate what Info Package is associated with an INFO
request. The mechanism is backward compatible with legacy usage of
INFO, as defined in [RFC2976], and allows such usage. New INFO
usages MUST use the mechanism defined in this document.
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3. Info Package Support
3.1. General
This section describes how SIP UAs indicate which Info Packages they
are willing to receive.
3.2. User Agent Behavior
A UA which supports the Info Package mechanism MUST indicate the set
of Info Packages it is willing to receive, using the Revc-Info header
field. A UA can list multiple Info Packages in a single Recv-Info
header field, and the UA can use multiple Recv-Info header fields.
The indication of Info Packages can take place during the session
establishment, and during a target refresh. This includes INVITE,
UPDATE, PRACK, ACK, and their non-failure responses (101-199 and 2xx
only). Note that the UAC is not required to indicate its set of Info
Packages in the initial INVITE request.
Once a UA has indicated that it is willing to to receive a specific
Info Package, and a dialog has been established, the UA MUST be
prepared to receive INFO request associated with that Info Package.
A UA MUST NOT send INFO request associated with Info Packages until
it has received an indication of which Info Packages the remote UA is
willing to receive.
If a UA indicates that it is willing to receive of multiple Info
Packages, which provide similar functionality, it is not possible to
indicate that the UA wishes to receive only one of them. It is up to
the application logic associated with the Info Packages, and specific
Info Package descriptions to describe application behavior in such
cases.
If a UA is not willing to receive any Info Packages, during session
establishment or later during the session, the UA MUST indicate this
by including a Recv-Info header field with a header value of 'nil'.
This enables other UAs to detect that the UA still supports the Info
Package mechanism.
Example: If a UA has previously indicated support of Info Packages
foo and bar, and the UA during the session wants to indicate that it
does not want to receive any Info Packages anymore, the UA sends a
target refresh request with a Recv-Info header field with a header
value of 'nil'.
For backward compatibility purpose, even if a UA indicates support
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the Info Package mechanism, it is still allowed to enable legacy
usages of INFO.
This document does not define a SIP option tag [RFC3261] for the Info
Package mechanism. However, Info Package specifications MAY define
option-tags associated with the specific Info Package, as described
in Section 7.5.
Note that, for backward compatibility purpose, if a UA indicates
support of the INFO method, it does not implicitly indicate support
of the Info Package mechanism. A UA MUST use the Recv-Info header
field to indicate support of the Info Package mechanism. Likewise,
even if a UA uses the Recv-Info header field to indicate that it
support the Info Package mechanism, in addition the UA MUST still
also explicitly indicate support of the INFO method.
3.3. Package Versioning
The Info Package mechanism does not support package versioning.
Specific Info Package payloads MAY contain version information, which
is handled by the applications associated wit the Info Package, but
that is outside the scope of the Info Package framework.
Note: Even if an Info Package name contains version numbering (e.g.
foo_v2), the Info Package mechanism does not distinguish a version
number from the rest of the Info Package name.
3.4. REGISTER Processing
When a UA registers, it SHALL include Recv-Info header field in the
REGISTER request, and list the Info Packages that it supports. The
registrar MAY later use the information e.g. for forking decisions.
3.5. OPTIONS Processing
If a UA sends an OPTIONS request, or a response, the UA SHALL include
Recv-Info header field in the message, and list the Info Packages
that it supports.
A UA MUST NOT send INFO requests with Info Packages based on the
information the UA received in an OPTIONS request. The Info Packages
MUST be negotiated for each session.
3.6. Example
The UAC sends an INVITE request, where the UAC indicates that it is
willing to receive Info Packages P and R.
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INVITE sip:bob@example.com SIP/2.0
Via: SIP/2.0/TCP pc33.example.com;branch=z9hG4bK776
Max-Forwards: 70
To: Bob <sip:bob@example.com>
From: Alice <sip:alice@example.com>;tag=1928301774
Call-ID: a84b4c76e66710@pc33.example.com
CSeq: 314159 INVITE
Recv-Info: P, R
Contact: <sip:alice@pc33.example.com>
Content-Type: application/sdp
Content-Length: ...
...
The UAS sends a 200 OK response back to the UAC, where the UAS
indicates that it is willing to receive Info Packages R and T.
SIP/2.0 200 OK
Via: SIP/2.0/TCP pc33.example.com;branch=z9hG4bK776;received=192.0.2.1
To: Bob <sip:bob@example.com>;tag=a6c85cf
From: Alice <sip:alice@example.com>;tag=1928301774
Call-ID: a84b4c76e66710@pc33.example.com
CSeq: 314159 INVITE
Contact: <sip:alice@pc33.example.com>
Recv-Info: R, T
Content-Type: application/sdp
Content-Length: ...
...
Since the UAS does not support Info Package P, the UAC decides to
indicate in the ACK request that it is only willing to receive Info
Package R, which the UAS also indicated support of.
ACK sip:ngw1@a.example.com SIP/2.0
Via: SIP/2.0/TCP pc33.example.com;branch=z9hG4bK776
To: Bob <sip:bob@example.com>;tag=a6c85cf
From: Alice <sip:alice@example.com>;tag=1928301774
Call-ID: a84b4c76e66710@pc33.example.com
CSeq: 314163 ACK
Recv-Info: R
Content-Length: 0
4. The INFO Method
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4.1. General
This section describes how the UA handling of INFO requests and
responses, and message bodies carried in INFO messages. It also
describes how an UA can indicate support of Info Packages in OPTIONS
requests and during registration.
The INFO method provides additional, application level information
that can further enhance a SIP application. Annex A gives more
details on the types of application for which the usage of INFO is
seen as appropriate.
The rules and procedures in this Section apply to implementations and
applications which support this. Existing implementations of, and
applications using, [RFC2976], may not follow the rules in this
Section. Because of backward compatibility purpose such cases MUST
NOT be regarded as error behavior, or wrong protocol usage, but
simply part of legacy INFO usage.
4.2. INFO Request
A UA MUST include a Info-Package header field, which indicates the
Info Package contained in the request, when it sends an INFO request
carrying an Info Package. An INFO request can contain only a single
Info Package. A UA MUST NOT send INFO requests associated with Info
Packages for which the remote entity has not indicated willingness
(using the Recv-Info header filed) to receive for the session.
A UA MAY send an INFO in a legacy usage context. In such case there
is no Info Package associated with the usage, and the INFO request
does not contain an Info-Package header field. In addition, the
support of the legacy usage has not been negotiated using the Recv-
Info header field. See Appendix B for examples of legacy usages.
The INFO method MUST NOT be used outside an INVITE dialog usage. The
INFO method has no lifetime or usage of its own. Supported Info
Packages are negotiated on a per session basis, and the negotiation
result MUST NOT be used for other sessions. If a UA receives an INFO
request outside an existing dialog, the UA MUST response with a 481
Call Does Not Exist error response.
Due to the possibility of forking, a UAC which during the early
dialog phase indicates support of one or more Info Packages (using
the Recv-Info header field) MUST be prepared to receive INFO requests
from multiple remote entities. Note that different remote entities
can indicate different sets of Info Packages which they are willing
to receive.
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The construction of the INFO request is the same as any other request
within an existing INVITE dialog usage. A UA can send INFO requests
both on early and confirmed dialogs.
The INFO request MUST NOT contain a Recv-Info header field. The UA
can only indicate the Info Packages that it is willing to receive
using the messages listed in Section 3.
4.3. INFO Request Message Body
The purpose of the INFO request is to carry application level
information between SIP UAs. The application data associated with an
Info Package SHOULD be carried as a payload in the message body of
the INFO request, unless the information can be retrieved from a SIP
header field.
Info Package specifications MUST describe the application level
information associated with the Info Package. Message body payloads
MUST have a MIME type value defined.
If a UA indicates that it is willing to receive a specific Info
Package, it means that the UA also supports any associated message
body MIME type associated with the Info Package. However, the UA
MUST still indicate support of those MIME types also in the Accept
header filed, according to the procedures in [RFC3261].
Some SIP extensions, which are orthogonal to INFO, MAY insert body
parts unrelated to the Info Package. UAs MUST conform to [RFC3261]
as updated by body-handling [I-D.ietf-sip-body-handling] to support
multipart MIME handling.
Each message body (or body part in the case of multipart MIME) MUST
contain a Content-Disposition header with an 'Info-Package' header
value, in order to in an easy way distinguish payloads associated
with the Info Package from other payloads.
If the whole message body is associated with the Info Package, the UA
MUST insert a Content-Disposition header with an 'Info-Package'
header value in the SIP part of the message. In that case, if
multipart MIME is used, the UA does not need to insert an 'Info-
Package' header value for the individual body parts.
NOTE: To avoid corner cases with legacy INFO usage, the Info-Package
header field is used to indicate the Info Package name, rather than
to use a Content-Disposition header field parameter in order to
indicate the name.
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4.4. INFO Response
If a UA receives an INFO request, associated with an Info-Package
that the UA has indicated willingness to receive, and the INFO
request contains data associated with that Info-Package, the UA MUST
send a 200 OK response.
If a UA receives an INFO request, associated with an Info Package
that the UA has not indicated willingness to receive, the UA MUST
send a 469 Bad INFO Package response. In the terminology of Multiple
Dialog Usages [RFC5057], this represents a Transaction Only failure.
If a UA receives an INFO request for legacy usage, for which no Info-
Package is associated (the INFO request does not contain an Info-
Package header filed), the UA must send a 200 OK response.
If a UA receives an INFO request, which does not match any existing
INVITE dialog usage, the UA MUST send a 481 Call Leg/Transaction Does
Not Exist response.
If a UA receives an INFO request, which carries a message body that
the UA does not support, and support of the message body is required
in the Content-Disposition header field, the UA MUST send a 415
Unsupported Media Type response. If support of the message body is
optional, the UA MUST send a 200 OK response even if the UA does not
support the message body.
The UAS MAY send other responses, such as Request Failure (4xx),
Server Failure (5xx) and Global Failure (6xx) as appropriate for the
request.
4.5. INFO Response Message Body
The response to the INFO request is normally generated by the SIP
stack before the Info Package application data has been provided to
the application associated with the Info Package. Therefore, an Info
Package MUST NOT define the inclusion of a message body in an INFO
response.
If the application that received the information needs to send some
information in the other direction, it MUST trigger a new INFO
request, rather than using the response of the received INFO request.
4.6. Order of Delivery
The Info Package framework relies on the CSeq header field to detect
if an INFO request is received out of order.
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If specific applications need additional mechanisms for order of
delivery, those mechanisms, and related procedures, MUST be specified
as part of the associated Info Package, and possible sequence numbers
etc MUST be defined as application data.
5. Formal INFO Method Definition
5.1. INFO Method
This document describes one new SIP method: INFO. This document
replaces the definition and registrations found in [RFC2976].
This table expands on Tables 2 and 3 in [RFC3261].
Header Where INFO
------ ----- ----
Accept R o
Accept-Encoding R o
Accept-Encoding 2xx o
Accept-Encoding 415 c
Accept-Language R o
Accept-Language 2xx o
Accept-Language 415 c
Alert-Info -
Allow R o
Allow 200 -
Allow 405 o
Authentication-Info 2xx o
Authorization R o
Call-ID c m
Call-Info o
Contact -
Content-Disposition o
Content-Encoding o
Content-Language o
Content-Length o
Content-Type *
CSeq c m
Date o
Error-Info 3xx-6xx o
Expires -
From c m
Geolocation R o
Max-Breadth R -
Max-Forwards R o
MIME-Version o
Min-Expires -
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Organization o
Priority R -
Privacy R o
Proxy-Authenticate 407 o
Proxy-Authorization R o
Proxy-Require R o
Reason r o
Record-Route R o
Record-Route 2xx,18x o
Require o
Retry-After R -
Retry-After 404,480,486 o
Retry-After 503 o
Retry-After 600,603 o
Route R o
Security-Client R o
Security-Server 421,494 o
Security-Verify R o
Server r o
Subject R o
Supported R o
Supported 2xx o
Timestamp o
To c m (w/ Tag)
Unsupported 420 o
User-Agent o
Via m
Warning r o
WWW-Authenticate 401 m
WWW-Authenticate 407 o
Figure 1: Table 1: Summary of Header Fields
5.2. INFO Header Fields
This table expands on tables 2 and 3 in [RFC3261].
Header field where ACK BYE CAN INV OPT REG PRA INF MSG UPD SUB NOT RFR
------------------------------------------------------------------------
Info-Package R - - - - - - - m* - - - - -
Recv-Info R o - - o o o o - - o - o o
Recv-Info 2xx o - - o o - o - - o - o -
Recv-Info 1xx o - - o o - o - - o - - -
Recv-Info r o - - - o - o - - o - - -
* The Info-Package header field is MANDATORY for INFO requests
associated with Info Packages. The Info-Package header field is not
applicable for legacy usage INFO requests [RFC2976].
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Table 2: INFO-related Header Fields
5.2.1. Info-Package header field
This document adds Info-Package to the definition of the element
"message-header" in the SIP message grammar. Section 4 describes the
Info-Package header field usage.
For the purposes of matching Info Package types indicated in Recv-
Info with those in the Info-Package header field value, one compares
the Info-package-name portion of the Info-package-type portion of the
Info-Package header field octet-by-octet with that of the Recv-Info
header field value. That is, the Info Package name is case
sensitive. Info-package-param is not part of the comparison-checking
algorithm.
This document does not define values for Info-Package types.
Individual Info Package specifications define these values. Such
specifications MUST register the values with IANA. These values are
Specification Required [RFC5226].
5.2.2. Recv-Info header field
This document adds Recv-Info to the definition of the element
"general-header" in the SIP [RFC3261] message grammar. Section 3
describes the Recv-Info header field usage.
6. Legacy INFO Usage
A number of applications, standardized and proprietary, make use of
INFO messages as defined in [RFC2976], without defined Info Packages
the and a possibility to use SIP to indicate what INFO usages UAs are
willing to use. For backward compatibility purpose, this document
does not deprecate such usage, and does not mandate to define Info
Packages for existing usages. However, any new usage of INFO SHALL
use the Info Package mechanism defined in this specification.
Since legacy INFO usages to not have associated Info Packages, it is
not possible to use the Recv-Info and Info-Package header fields for
legacy INFO usages. That is, a UA can not use the Recv-Info header
filed to indicate for which legacy usages it is willing to receive
INFO requests, and a UA can not use the Info-Package header to
indicate for which legacy INFO usage an INFO request is associated
with.
NOTE: For legacy INFO usages, static configuration is often used to
define what specific legacy INFO usages UAs support.
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An INFO request associated with an Info Package MUST contain a Info-
Package header field. An INFO request without an Info-Package header
field MUST NOT contain an Info-Package header field, and the request
SHALL be interpreted as being a legacy INFO usage request.
UAs are allowed to enable both legacy INFO usages and Info Package
usages as part of the same session.
7. Info Package Requirements
7.1. General
This Section provides guidance on how to define an Info Package, and
what information needs to be provided.
If an Info Package extends or modifies the behavior described in this
document, it MUST be described in the definition for that Info
Package. Info Package definitions SHOULD NOT repeat procedures
defined in this specification, unless needed for clarification or
emphasis purpose.
Info Packages MUST NOT weaken any behavior designated with "SHOULD"
or "MUST" in this specification. However, Info Packages MAY
strengthen "SHOULD", "MAY", or "RECOMMENDED" requirements to "MUST"
strength if applications associated with the Info Package requires
it.
Info Package definitions SHALL address the issues defined in the
following subsections, unless an issue is not applicable for the
specific Info Package.
7.2. Applicability
The Info Package specification MUST describe why the Info Package
mechanism, rather than some other mechanism, has been chosen for the
specific use-case to transfer application information between SIP
endpoints. Common reasons can be a requirement for SIP Proxies or
back-to-back User Agents (B2BUAs) to see the transport application
information, or that it is seen unfeasible to establish separate
dialogs (subscription) for transporting the information.
Annex A provides more information, and describes alternative
mechanisms which one should consider for solving the specific use-
case.
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7.3. Info Package Name
The Info Package specification MUST define an Info Package name.
The specification MUST also define the header field value to be used
to indicate support of this package in the Recv-Info and Info-Package
header fields. The header field value MUST conform to the ABNF
defined in Section 8.2.
The specification MUST also include the information that appears in
the IANA registration of the token. For information on registering
such types, see Section **9.
7.4. Info Package Parameters
The Info Package specification MAY define Info Package parameters
which can be used in the Recv-Info or Info-Package header fields,
together with the header field value representing the Info Package.
The specification MUST describe the syntax and semantics of the
parameters. It MUST be specified whether a specific parameter is
only applicable to the Recv-Info header, the Info-Package header, or
both.
Note that Info Package parameters are only applicable for the Info
Package(s) for which they have been explicitly defined. If used for
other Info Packages they MUST be discarded.
7.5. SIP Option Tags
The Info Package specification MAY define SIP option tags, which can
be used as described in [RFC3261].
SIP option tags MUST conform to the SIP Change Process [RFC3427].
7.6. INFO Message Bodies
The Info Package specification MUST define what type of message
bodies, if any, are associated with the Info Package, and MUST refer
to specifications where the syntax, semantics and MIME type of the
message body is described.
7.7. Info Package Usage Restrictions
The Info Package specification MUST define whether a UA is allowed to
send overlapping (outstanding) INFO requests associated with the Info
Package, or whether the UA has to wait for the response for a
previous INFO request associated with the same Info Package.
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The specification MUST define whether there SIP level restrictions in
the usage of the Info Package. For example, an Info Package may
require support of other SIP extensions (e.g. reliable provisional
responses).
The specification MUST define whether there are restrictions on
indicating support of, or using, the Info Package together with other
Info Packages.
If Info Package restrictions are violated (i.e. if overlapping INFO
requests are not allowed for an Info Package, but a UA still receives
overlapping requests), the UA MUST NOT reject such requests. Instead
the application logic associated with the Info Package MUST handle
such situations.
7.8. Rate of INFO Requests
The Info Package specification MUST a maximum rate at which INFO
requests associated with the specific Info Package can be generated
by a UA in a dialog.
The specification MAY define Info Package parameters to be used for
indicating or negotiating the INFO request rate. Alternatively the
rate information can be included in the application information
associated with the Info Package.
7.9. IANA Registrations
The Info Package specification MUST contain an IANA Considerations
section that includes definitions for the Info Package Name and, if
needed, supported MIME types.
7.10. Security Considerations
If the application information associated with the Info Package
requires certain level of security, the Info Package specification
MUST describe the mechanisms to be used in order to provide the
required security.
Otherwise, even if no additional security than what is provided for
the underlying SIP protocol is needed, it SHALL be stated in the Info
Package specification.
NOTE: In some cases, it may not be sufficient to mandate TLS in order
to secure the Info Package payload, since intermediaries will have
access to the payload and past the first hop, there is no way to
assure subsequent hops will not forwards the payload in clear text.
The best way to ensure secure transport at the application level is
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to have the security at the application level. The most common
method of achieving this is to use end-to-end security techniques
such as S/MIME [RFC3851].
7.11. Application Procedures
The Info Package specification SHOULD contain a description of the
application procedures associated with the Info Package, or
alternatively refer to application procedures defined elsewhere.
7.12. Examples
It is RECOMMENDED that Info Package specifications include
demonstrative message flow diagrams, paired with complete messages
and message descriptions.
Note that example flows are by definition informative, and MUST NOT
replace normative text
8. Syntax
8.1. General
This Section describes the syntax extensions required for the INFO
method. The previous sections describe the semantics. Note the
formal syntax definitions described in this document use the ABNF
format used in [RFC3261] and contain references to elements defined
therein.
8.2. ABNF
INFOm = %x49.4E.46.4F ; INFO in caps
extension-method = INFOm / token
Info-Package = "Info-Package" HCOLON Info-package-type
Recv-Info = "Recv-Info" HCOLON Info-package-list
Info-package-list = "nil"
/ Info-package-type *( COMMA Info-package-type )
Info-package-type = Info-package-name *( ";" Info-package-param)
Info-package-name = token
Info-package-param = generic-param
NOTE on the Recv-Info production: if the header field value is "nil",
the header field MUST NOT contain any other Info Packages, and the
SIP message MUST NOT contain more than one Recv-Info header field.
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9. IANA Considerations
9.1. Update to Registration of SIP INFO Method
Please update the existing registration in the SIP Methods and
Response Codes registry under the SIP Parameters registry that
states:
Method: INFO
Reference: [RFC2976]
to:
Method: INFO
Reference: [RFCXXXX]
9.2. Registration of the Info-Package Header Field
Please add the following new SIP header field in the Header Fields
subregistry under the SIP Parameters registry.
Header Name: Info-Package
Compact Form: (none)
Reference: [RFCXXXX]
9.3. Registration of the Recv-Info Header Field
Please add the following new SIP header field in the Header Fields
subregistry under the SIP Parameters registry.
Header Name: Recv-Info
Compact Form: (none)
Reference: [RFCXXXX]
9.4. Creation of the Info Packages Registry
Please create a subregistry in the SIP Parameters registry for Info
Packages. This subregistry has a modified First Come First Served
[RFC5226] policy.
The following data elements populate the Info Package Registry.
o Info Package Name: The Info Package Name is a case-sensitive
token. In addition, IANA shall not register multiple Info Package
names that have identical case-insensitive values.
o Info Package Parameters: The Info Package Parameters are case-
sensitive tokens. Info Package Parameters are only applicable to
the Info Package for which they are defined, so the same Info
Package Parameter Names may exist for different Info Packages.
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o Info Package Payload MIME Types: A list of zero or more registered
MIME types from the MIME Type Registry.
o Standards Status: Values are "Standards Track" or empty. See
below for a discussion and rules on this field.
o Reference: If there is a published specification describing the
Info Package, place a reference to that specification in this
column. See below for a discussion on this field.
If there is a published specification, the registration MUST include
a reference to such specification. The Standards Status field is an
indicator of the level of community review for the Info Package
specification. If the specification meets the requirements for
Specification Required [RFC5226], the value for the Standards Status
field is "Standards Track". Otherwise, the field is empty.
This document uses the Info Package Name "nil" to represent "no Info
Package present" and as such, IANA shall not honor a request to
register the "nil" Info Package.
The initial population of this table shall be:
Name MIME Type Standards Status Reference
nil Standards Track [RFCXXXX]
9.5. Registration of the Info-Package Content-Disposition
Please add the following registration to the Content-Disposition
registry. The description suitable for the IANA registry is as
follows.
The payload of the message carrying this Content-Disposition header
field value is the payload of an Info Package.
9.6. SIP Response Code 469 Registration
Please register the 469 response code in the Session Initiation
Protocol Parameters - Response Codes registry as follows.
Response Code: 469
Default Reason Phrase: Bad INFO Package
Reference: RFCXXXX
10. Examples
10.1. Simple Info Package
Here Alice sends Bob a simple Info Package payload.
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INFO sip:alice@192.0.2.1 SIP/2.0
Via: SIP/2.0/UDP 192.0.2.2:5060;branch=z9hG4bKnabcdef
To: Alice <sip:alice@example.net>;tag=1234567
From: Bob <sip:bob@example.com>;tag=abcdefg
Call-Id: 123456mcmxcix
CSeq: 2 INFO
Info-Package: foo
Content-type: application/foo
Content-Disposition: Info-Package
Content-length: 24
I am a foo message type
10.2. Multipart INFO Example
Other SIP extensions can put payloads into an INFO method,
independent of the Info Package. In this case, the Info Package
payload gets put into a Multipart MIME body, with the content
disposition indicating which body belongs to the Info Package. Since
there is one and only one Info Package payload in the message, we
only need to tag which body part goes with the Info Package.
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INFO sip:alice@192.0.2.1 SIP/2.0
Via: SIP/2.0/UDP 192.0.2.2:5060;branch=z9hG4bKnabcdef
To: Alice <sip:alice@example.net>;tag=1234567
From: Bob <sip:bob@example.com>;tag=abcdefg
Call-Id: 123456mcmxcix
CSeq: 7 INFO
Info-Package: foo
mumble-extension: <cid:abcd9999qq>
Content-Type: multipart/mixed;boundary="theboundary"
Content-Length: ...
--theboundary
Content-Type: application/mumble
Content-Id: abcd9999qq
...
<mumble stuff>
--theboundary
Content-Type: application/foo
Content-Disposition: Info-Package
Content-length: 24
I am a foo message type
--theboundary--
11. Modifications to SIP Change Process
By eliminating multiple uses of INFO messages without adequate
community review and by eliminating the possibility for rogue SIP UAs
from confusing another User Agent by purposely sending unrelated INFO
requests, we expect this document's clarification of the use of INFO
to improve the security of the Internet. Whilst rogue UAs can still
send unrelated INFO requests, this framework provides mechanisms for
which the UAS and other security devices can filter for approved Info
Packages.
If the content of the Info Package payload is private, User Agents
will need to use end-to-end encryption, such as S/MIME, to prevent
access to the content. This is particularly important as transport
of INFO is likely not to be end-to-end, but through SIP proxies and
back-to-back user agents (B2BUA's), which the user may not trust.
The INFO mechanism transports application level information. One
implication of this is INFO messages may require a higher level of
protection than the underlying SIP-based session signaling. In
particular, if one does not protect the SIP signaling from
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eavesdropping or authentication and repudiation attacks, for example
by using TLS transport, then the INFO request and its contents will
be vulnerable, as well. Even with SIP/TLS, any SIP hop along the
path from UAC to UAS can view, modify, or intercept INFO requests, as
they can with any SIP request. This means some applications may
require end-to-end encryption of the INFO payload, beyond, for
example, hop-by-hop protection of the SIP signaling itself. Since
the application dictates the level of security required, individual
Info Packages have to enumerate these requirements. In any event,
the Info Package mechanism described by this document provides the
tools for such secure, end-to-end transport of application data.
One interesting property of Info Package use is one can reuse the
same digest-challenge mechanism used for INVITE based authentication
for the INFO request. For example, one could use a quality-of-
protection (qop) value of authentication with integrity (auth-int),
to challenge the request and its body, and prevent intermediate
devices from modifying the body. However this assumes the device
which knows the credentials in order to perform the INVITE challenge
is still in the path for the INFO, or that the far-end UAS knows such
credentials.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[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.
[I-D.ietf-sip-body-handling]
Camarillo, G., "Message Body Handling in the Session
Initiation Protocol (SIP)",
draft-ietf-sip-body-handling-06 (work in progress),
March 2009.
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12.2. Informative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981.
[RFC2976] Donovan, S., "The SIP INFO Method", RFC 2976,
October 2000.
[RFC4497] Elwell, J., Derks, F., Mourot, P., and O. Rousseau,
"Interworking between the Session Initiation Protocol
(SIP) and QSIG", BCP 117, RFC 4497, May 2006.
[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.
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
RFC 4949, August 2007.
[RFC3080] Rose, M., "The Blocks Extensible Exchange Protocol Core",
RFC 3080, March 2001.
[RFC3851] Ramsdell, B., "Secure/Multipurpose Internet Mail
Extensions (S/MIME) Version 3.1 Message Specification",
RFC 3851, July 2004.
[RFC3725] Rosenberg, J., Peterson, J., Schulzrinne, H., and G.
Camarillo, "Best Current Practices for Third Party Call
Control (3pcc) in the Session Initiation Protocol (SIP)",
BCP 85, RFC 3725, April 2004.
[RFC3427] Mankin, A., Bradner, S., Mahy, R., Willis, D., Ott, J.,
and B. Rosen, "Change Process for the Session Initiation
Protocol (SIP)", BCP 67, RFC 3427, December 2002.
[RFC3841] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Caller
Preferences for the Session Initiation Protocol (SIP)",
RFC 3841, August 2004.
[RFC3372] Vemuri, A. and J. Peterson, "Session Initiation Protocol
for Telephones (SIP-T): Context and Architectures",
BCP 63, RFC 3372, September 2002.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
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[RFC3458] Burger, E., Candell, E., Eliot, C., and G. Klyne, "Message
Context for Internet Mail", RFC 3458, January 2003.
[RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
and D. Gurle, "Session Initiation Protocol (SIP) Extension
for Instant Messaging", RFC 3428, December 2002.
[RFC4028] Donovan, S. and J. Rosenberg, "Session Timers in the
Session Initiation Protocol (SIP)", RFC 4028, April 2005.
[RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
the Session Description Protocol (SDP)", RFC 4145,
September 2005.
[RFC4240] Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network
Media Services with SIP", RFC 4240, December 2005.
[RFC4730] Burger, E. and M. Dolly, "A Session Initiation Protocol
(SIP) Event Package for Key Press Stimulus (KPML)",
RFC 4730, November 2006.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007.
[RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message
Session Relay Protocol (MSRP)", RFC 4975, September 2007.
[RFC5022] Van Dyke, J., Burger, E., and A. Spitzer, "Media Server
Control Markup Language (MSCML) and Protocol", RFC 5022,
September 2007.
[RFC5057] Sparks, R., "Multiple Dialog Usages in the Session
Initiation Protocol", RFC 5057, November 2007.
[RFC5168] Levin, O., Even, R., and P. Hagendorf, "XML Schema for
Media Control", RFC 5168, March 2008.
[W3C.REC-voicexml21-20070619]
Porter, B., McGlashan, S., Lee, A., Burnett, D., Carter,
J., Oshry, M., Bodell, M., Baggia, P., Rehor, K., Burke,
D., Candell, E., and R. Auburn, "Voice Extensible Markup
Language (VoiceXML) 2.1", World Wide Web Consortium
Recommendation REC-voicexml21-20070619, June 2007,
<http://www.w3.org/TR/2007/REC-voicexml21-20070619>.
[I-D.ietf-speechsc-mrcpv2]
Shanmugham, S. and D. Burnett, "Media Resource Control
Protocol Version 2 (MRCPv2)",
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draft-ietf-speechsc-mrcpv2-19 (work in progress),
June 2009.
[I-D.saleem-msml]
Sharratt, G. and A. Saleem, "Media Server Markup Language
(MSML)", draft-saleem-msml-08 (work in progress),
February 2009.
Appendix A. Info Package Considerations
A.1. General
This section covers considerations to take into account when deciding
whether the usage of an Info Package is appropriate for transporting
of application information for a specific use-case.
A.2. Appropriateness of Info Package Usage
When designing an Info Package, for application level information
exchange, it is important to consider: is signaling, using INFO
requests, within a SIP session, an appropriate mechanism for the use-
case? Is it because it is the most reasonable and appropriate
choice, or merely because "it's easy"? Choosing an inappropriate
mechanism for a specific use-case can cause negative effects in SIP
networks where the mechanism is used.
A.3. Dialog Fate Sharing
As described in [RFC5057], an INFO request is always part of an
INVITE dialog usage.
One needs to consider the fate of the dialog usage of an INFO request
is rejected. In some cases it may be acceptable that the whole
dialog useage is terminated, while in other cases is is desirable to
maintain the dialog usage.
A.4. INFO Request Rate and Volume
There is no default throttling mechanism for INFO requests. Apart
from the session establishment, the number of SIP messages exchanged
during a normal SIP session is rather small.
Some applications, like sending of DTMF tones, can generate a burst
of up to 20 messages per second. Other applications, like constant
GPS location updates, could generate a high rate of INFO requests
during the whole session.
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Furthermore, SIP messages tend to be relatively small, on the order
of 500 Bytes to 32K Bytes. SIP is a poor mechanism for direct
exchange of bulk data beyond these limits, especially if the headers
plus body exceed the UDP MTU [RFC0768]. Appropriate mechanisms for
such traffic include HTTP [RFC2616], MSRP [RFC4975], or other user
plane data transport mechanisms.
A.5. Alternative Mechanisms
A.5.1. Alternative SIP signaling plane mechanisms
A.5.1.1. General
This subsection describes some alternative mechanisms for
transporting application information on the SIP signaling plane,
using SIP messages.
A.5.1.2. SUBSCRIBE/NOTIFY
An alternative for application level interaction is SIP Events, also
known as SUBSCRIBE/NOTIFY [RFC3265]. In this model, a user agent
requests state information, such as key pad presses from a device to
an application server or key map images from an application server to
a device.
A SUBSCRIBE requests creates a new session, and a subscription dialog
usage [RFC5057], which is separate, and does not share the fate any
other sessions.
The subscription mechanism can be used by SIP entities to receive
state information about SIP sessions, without requiring the entities
to be part of the route set of those sessions.
As SUBSCRIBE/NOTIFY messages traverse through stateful SIP proxies
and B2BUAs, the resource impact caused by the subscription sessions
needs to be considred. The number of subscription sessions per user
also needs to be considered.
As for any other SIP signaling plane based mechanism for transporting
application information, the SUBSCRIBE/NOTIFY messages can put a
significant burden on intermediate SIP entities which are part of the
session route set, but do not have any interest in the application
information transported between the end users.
A.5.1.3. MESSAGE
The MESSAGE method [RFC3428] defines one-time instant message
exchange, typically for sending MIME contents for rendering to the
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user.
A.5.2. Media Plane Mechanisms
A.5.2.1. General
In SIP, media plane channels associated with SIP sessions are
established using SIP signaling, but the data exchanged on the media
plane channel does not traverse SIP signaling intermediates, so if
there will be a lot of information exchanged, and there is no need
for the SIP signaling intermediates routing to examine the
information, it is recommended to use a media plane mechanism, rather
than a SIP signaling based.
A low latency requirement for the exchange of information is one
strong indicator for using a media channel. Exchanging information
through the SIP routing network can introduce hundreds of
milliseconds of latency.
A.5.2.2. MRCPv2
One mechanism for media plane exchange of application data is MRCPv2
[I-D.ietf-speechsc-mrcpv2], where a media plane connection-oriented
channel, such as a TCP [RFC0793] or SCTP [RFC4960] stream is
established.
A.5.2.3. MRSP
MSRP [RFC4975] defines session-based instant messaging as well as
bulk file transfer and other such large-volume uses.
A.5.3. Non-SIP related mechanisms
Another alternative is to use a totally externally signaled channel,
such as HTTP [RFC2616]. In this model, the user agent knows about a
rendezvous point to direct HTTP requests to for the transfer of
information. Examples include encoding of a prompt to retrieve in
the SIP Request URI in [RFC4240] or the encoding of a SUBMIT target
in a VoiceXML [W3C.REC-voicexml21-20070619] script.
Appendix B. Legacy INFO Usages
We do not intend this section to be a comprehensive catalog of INFO
usages. However, it should give the reader a flavor for current INFO
usages.
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B.1. ISUP
SIP-T uses Content-Type to identify ISUP protocol elements in an INFO
message. See RFC3372 [RFC3372].
B.2. QSIG
QSIG uses Content-Type to identify QSIG protocol elements in an INFO
message. See RFC4497 [RFC4497].
B.3. MSCML
MSCML uses a Require to ensure the UAS understands that INFO messages
of the MSCML type are in fact MSCML messages. See RFC5022 [RFC5022].
B.4. MSML
MSML endpoints just know the INFO messages carry MSML and from the
Content-Type of the given INFO method request. See the MSML
[I-D.saleem-msml] draft.
B.5. Video Fast Update
Microsoft, Polycom, and Radvision used INFO messages as an interim
solution for requesting fast video update before the ability to
request I-Frames in RTCP was available. See the XML Schema for Media
Control [RFC5168] for more information.
Appendix C. Acknowledgements
We are standing on the shoulders of giants. Jonathan Rosenberg did
the original "INFO Considered Harmful" Internet Draft on 26 December
2002, which influenced the work group and this document. Likewise,
Dean Willis influenced the text from his Internet Draft, "Packaging
and Negotiation of INFO Methods for the Session Initiation Protocol"
of 15 January 2003. Four paragraphs come from Jonathan Rosenberg's
INFO Litmus draft. My, we have been working on this for a long time!
This and other related drafts have elicited well over 450 messages on
the SIP list. People who have argued with its thesis, supported its
thesis, added to the examples, or argued with the examples, include
the following individuals:
Adam Roach, Bram Verburg, Brian Stucker, Chris Boulton, Cullen
Jennings, Dale Worley, Dean Willis, Frank Miller, Gonzalo
Camarillo, Gordon Beith, Henry Sinnreich, James Jackson, James
Rafferty, Jeroen van Bemmel, Joel Halpern, John Elwell, Johnathan
Rosenberg, Juha Heinanen, Keith Drage, Kevin Attard Compagno,
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Manpreet Singh, Martin Dolly, Mary Barnes, Michael Procter, Paul
Kyzivat, Peili Xu, Peter Blatherwick, Raj Jain, Rayees Khan,
Robert Sparks, Roland Jesske, Salvatore Loreto, Sam Ganesan,
Sanjay Sinha, Spencer Dawkins, Steve Langstaff, Sumit Garg, and
Xavier Marjou.
John Elwell and Francois Audet helped with QSIG references. In
addition, Francois Audet provided actual text for the revised
abstract. Keith Drage gave lots of excellent comments and helped
immensely with Figure 1.
The work group version of this document benefited from the close
readings and comments from
John Elwell, Paul Kyzivat, Dean Willis, Francois Audet, Dale
Worley, Andrew Allen, Adam Roach, Anders Kristensen, Gordon Beith,
Ben Campbell, Bob Penfield, Keith Drage, Jeroen van Bemmel, Mary
Barnes, and Salvatore Loreto.
Since publication of the first work group version of this document,
we have had over 329 messages. New voices in addition to those
included above include
Arun Arunachalam, Christian Stredicke, Eric Rescorla, Inaki Baz
Castillo, and Roni Evan.
However, any errors and issues we missed are still our own.
Appendix D. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-sip-info-events-03
o Clarified Abstract language
o All SIP dialogs are now refered to as sessions
o Clarified the image example in the Introduction
o Clarified the relationship (none) between SIP Event Packages and
SIP Info Packages
o Really, really clarified the protocol is NOT a negotiation but an
advertisement
o Split Section 3 into UAS and UAC behavior
o Moved the example in section 3 into its own sub-section, and used
full SIP header fields
o Clarified forking behavior
o Clarified language around when to send a body
o Added 469 error response, instead of reusing 489
o Clarified overlapping INFO method handling
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o Fixed table 1 to follow 3261, not 2543
o Added REFER to the INFO Headers table
o replaced token-nodot with token for Info-Package header field
values
o Clarified end-to-end security considerations
o Info Package parameters are semi-colon delimited, not dot
delimited
Changes from -02
o Applicability statement explicitly says we're backwards compatible
o Explicitly state we work like UPDATE (both early and confirmed
dialogs)
o Agreed text for IANA Considerations package registry
Changes from -01
o One and only one Info Package per INFO
o Removed Send-Info header field, greatly simplifying negotiation
o Multiple body part identification through Content-Disposition:
Info-Package
o Note that forking INVITEs may result in multiple INFOs coming back
to INVITE originator
o Describe how a UAS can enforce strict adherence to this document
o Remove CANCEL INFO faux pas
o Better explained overlapping INFO issues and resolutions
o Token names are now really case sensitive
o Moved Info Package Considerations to an Appendix
o Introduced stronger, yet more open, IANA registration process
o Took a few more paragraphs from INFO Litmus to cover all bases.
o Added RFC 5168 to legacy usages
Changes from -00
o Corrected ABNF.
o Enabled sending of legacy INFO messages. Receiving legacy INFO
messages was already here.
o Negotiation is not Offer/Answer, it is Offer/Offer.
o Created the explicit "nil" Info Package to indicate no info
package.
o Fixed CANCEL impacting future transactions.
o Added Registrar behavior.
o Added OPTIONS processing.
o Clarified overlapping INFO method processing.
o Described multiple INFO bodies in a single INFO method.
o Took out Info-Package as a header field for responses to the INFO
method.
o Expanded on risks of using INFO and filled-in more on the
alternatives
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o Moved definitions of INFO into the body of the text and cleaned up
IANA Considerations section
o Added legacy usages descriptions
Authors' Addresses
Eric W. Burger
NeuStar, Inc.
46000 Center Oak Plaza
Sterling, VA 20166-6579
USA
Email: eburger@standardstrack.com
URI: http://www.standardstrack.com
Hadriel Kaplan
Acme Packet
71 Third Ave.
Burlington, MA 01803
USA
Phone:
Fax:
Email: hkaplan@acmepacket.com
URI:
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas, 02420
Finland
Phone:
Fax:
Email: christer.holmberg@ericsson.com
URI:
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