draft-ietf-sipcore-info-events-08.txt   draft-ietf-sipcore-info-events-09.txt 
SIPCORE C. Holmberg SIPCORE C. Holmberg
Internet-Draft Ericsson Internet-Draft Ericsson
Obsoletes: 2976 (if approved) E. Burger Obsoletes: 2976 (if approved) E. Burger
Intended status: Standards Track NeuStar, Inc. Intended status: Standards Track NeuStar, Inc.
Expires: November 20, 2010 H. Kaplan Expires: April 1, 2011 H. Kaplan
Acme Packet Acme Packet
May 19, 2010 September 28, 2010
Session Initiation Protocol (SIP) INFO Method and Package Framework Session Initiation Protocol (SIP) INFO Method and Package Framework
draft-ietf-sipcore-info-events-08 draft-ietf-sipcore-info-events-09
Abstract Abstract
This document defines a method, INFO, for the Session Initiation This document defines a method, INFO, for the Session Initiation
Protocol (SIP), and an Info Package mechanism. The document Protocol (SIP), and an Info Package mechanism. The document
obsoletes RFC 2976. For backward compatibility the document also obsoletes RFC 2976. For backward compatibility the document also
specifies a "legacy" mode of usage of the INFO method that is specifies a "legacy" mode of usage of the INFO method that is
compatible with the usage previously defined in RFC 2976, referred to compatible with the usage previously defined in RFC 2976, referred to
as "legacy INFO Usage" in this document. as "legacy INFO Usage" in this document.
skipping to change at page 1, line 44 skipping to change at page 1, line 44
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This Internet-Draft will expire on November 20, 2010. This Internet-Draft will expire on April 1, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. The INFO Method . . . . . . . . . . . . . . . . . . . . . . . 5 3. Applicability and Backward Compatibility . . . . . . . . . . . 6
3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. The INFO Method . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. INFO Request . . . . . . . . . . . . . . . . . . . . . . 5 4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2.1. INFO Request Sender . . . . . . . . . . . . . . . . . 5 4.2. INFO Request . . . . . . . . . . . . . . . . . . . . . . 6
3.2.2. INFO Request Receiver . . . . . . . . . . . . . . . . 6 4.2.1. INFO Request Sender . . . . . . . . . . . . . . . . . 7
3.2.3. SIP Proxies . . . . . . . . . . . . . . . . . . . . . 7 4.2.2. INFO Request Receiver . . . . . . . . . . . . . . . . 8
3.3. INFO Message Body . . . . . . . . . . . . . . . . . . . . 7 4.2.3. SIP Proxies . . . . . . . . . . . . . . . . . . . . . 8
3.3.1. INFO Request Message Body . . . . . . . . . . . . . . 7 4.3. INFO Message Body . . . . . . . . . . . . . . . . . . . . 8
3.3.2. INFO Response Message Body . . . . . . . . . . . . . . 7 4.3.1. INFO Request Message Body . . . . . . . . . . . . . . 8
3.4. Order of Delivery . . . . . . . . . . . . . . . . . . . . 8 4.3.2. INFO Response Message Body . . . . . . . . . . . . . . 9
4. Info Packages . . . . . . . . . . . . . . . . . . . . . . . . 8 4.4. Order of Delivery . . . . . . . . . . . . . . . . . . . . 9
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Info Packages . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2. User Agent Behavior . . . . . . . . . . . . . . . . . . . 8 5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 8 5.2. User Agent Behavior . . . . . . . . . . . . . . . . . . . 10
4.2.2. UA Procedures . . . . . . . . . . . . . . . . . . . . 8 5.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 10
4.2.3. Recv-Info header field rules . . . . . . . . . . . . . 10 5.2.2. UA Procedures . . . . . . . . . . . . . . . . . . . . 10
4.2.4. Info Package fallback rules . . . . . . . . . . . . . 10 5.2.3. Recv-Info header field rules . . . . . . . . . . . . . 11
4.3. REGISTER Processing . . . . . . . . . . . . . . . . . . . 11 5.2.4. Info Package fallback rules . . . . . . . . . . . . . 12
5. Formal INFO Method Definition . . . . . . . . . . . . . . . . 11 5.3. REGISTER Processing . . . . . . . . . . . . . . . . . . . 12
5.1. INFO Method . . . . . . . . . . . . . . . . . . . . . . . 11 6. Formal INFO Method Definition . . . . . . . . . . . . . . . . 13
6. INFO Header Fields . . . . . . . . . . . . . . . . . . . . . . 13 6.1. INFO Method . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 13 7. INFO Header Fields . . . . . . . . . . . . . . . . . . . . . . 14
6.2. Info-Package header field . . . . . . . . . . . . . . . . 14
6.3. Recv-Info header field . . . . . . . . . . . . . . . . . 14
7. Info Package Considerations . . . . . . . . . . . . . . . . . 14
7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 14 7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.2. Appropriateness of Info Package Usage . . . . . . . . . . 14 7.2. Info-Package header field . . . . . . . . . . . . . . . . 15
7.3. Alternative Mechanisms . . . . . . . . . . . . . . . . . 15 7.3. Recv-Info header field . . . . . . . . . . . . . . . . . 16
7.3.1. Alternative SIP signaling plane mechanisms . . . . . . 15 8. Info Package Considerations . . . . . . . . . . . . . . . . . 16
7.3.2. Media Plane Mechanisms . . . . . . . . . . . . . . . . 16 8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.3.3. Non-SIP related mechanisms . . . . . . . . . . . . . . 17 8.2. Appropriateness of Info Package Usage . . . . . . . . . . 16
8. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 8.3. Alternative Mechanisms . . . . . . . . . . . . . . . . . 16
8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 17 8.3.1. Alternative SIP signaling plane mechanisms . . . . . . 16
8.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8.3.2. Media Plane Mechanisms . . . . . . . . . . . . . . . . 18
9. Legacy INFO Usage . . . . . . . . . . . . . . . . . . . . . . 18 8.3.3. Non-SIP related mechanisms . . . . . . . . . . . . . . 19
9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 18 9. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.2. Problems . . . . . . . . . . . . . . . . . . . . . . . . 18 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.3. Co-existence with Info Package based INFO usage . . . . . 19 9.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10. Info Package Requirements . . . . . . . . . . . . . . . . . . 19 10. Info Package Requirements . . . . . . . . . . . . . . . . . . 19
10.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 19 10.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.2. Overall Description . . . . . . . . . . . . . . . . . . . 20 10.2. Overall Description . . . . . . . . . . . . . . . . . . . 20
10.3. Applicability . . . . . . . . . . . . . . . . . . . . . . 20 10.3. Applicability . . . . . . . . . . . . . . . . . . . . . . 20
10.4. Info Package Name . . . . . . . . . . . . . . . . . . . . 20 10.4. Info Package Name . . . . . . . . . . . . . . . . . . . . 21
10.5. Info Package Parameters . . . . . . . . . . . . . . . . . 21 10.5. Info Package Parameters . . . . . . . . . . . . . . . . . 21
10.6. SIP Option Tags . . . . . . . . . . . . . . . . . . . . . 21 10.6. SIP Option Tags . . . . . . . . . . . . . . . . . . . . . 21
10.7. INFO Message Body Parts . . . . . . . . . . . . . . . . . 21 10.7. INFO Message Body Parts . . . . . . . . . . . . . . . . . 22
10.8. Info Package Usage Restrictions . . . . . . . . . . . . . 22 10.8. Info Package Usage Restrictions . . . . . . . . . . . . . 22
10.9. Rate of INFO Requests . . . . . . . . . . . . . . . . . . 22 10.9. Rate of INFO Requests . . . . . . . . . . . . . . . . . . 22
10.10. Info Package Security Considerations . . . . . . . . . . 22 10.10. Info Package Security Considerations . . . . . . . . . . 23
10.11. Implementation Details . . . . . . . . . . . . . . . . . 23 10.11. Implementation Details . . . . . . . . . . . . . . . . . 23
10.12. Examples . . . . . . . . . . . . . . . . . . . . . . . . 23 10.12. Examples . . . . . . . . . . . . . . . . . . . . . . . . 23
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
11.1. Update to Registration of SIP INFO Method . . . . . . . . 23 11.1. Update to Registration of SIP INFO Method . . . . . . . . 23
11.2. Registration of the Info-Package header field . . . . . . 24 11.2. Registration of the Info-Package header field . . . . . . 24
11.3. Registration of the Recv-Info header field . . . . . . . 24 11.3. Registration of the Recv-Info header field . . . . . . . 24
11.4. Creation of the Info Packages Registry . . . . . . . . . 24 11.4. Creation of the Info Packages Registry . . . . . . . . . 24
11.5. Registration of the Info-Package Content-Disposition . . 25 11.5. Registration of the Info-Package Content-Disposition . . 25
11.6. SIP Response Code 469 Registration . . . . . . . . . . . 25 11.6. SIP Response Code 469 Registration . . . . . . . . . . . 25
12. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 12. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
12.1. Indication for which Info Packages UAs are willing to 12.1. Indication for which Info Packages UAs are willing to
receive INFO requests . . . . . . . . . . . . . . . . . . 25 receive INFO requests . . . . . . . . . . . . . . . . . . 25
12.1.1. Initial INVITE request . . . . . . . . . . . . . . . . 25 12.1.1. Initial INVITE request . . . . . . . . . . . . . . . . 25
12.1.2. Target refresh . . . . . . . . . . . . . . . . . . . . 26 12.1.2. Target refresh . . . . . . . . . . . . . . . . . . . . 26
12.2. INFO request associated with Info Package . . . . . . . . 27 12.2. INFO request associated with Info Package . . . . . . . . 27
12.2.1. Single payload . . . . . . . . . . . . . . . . . . . . 27 12.2.1. Single payload . . . . . . . . . . . . . . . . . . . . 27
12.2.2. Multipart INFO . . . . . . . . . . . . . . . . . . . . 27 12.2.2. Multipart INFO . . . . . . . . . . . . . . . . . . . . 28
13. Security Considerations . . . . . . . . . . . . . . . . . . . 30 13. Security Considerations . . . . . . . . . . . . . . . . . . . 31
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
14.1. Normative References . . . . . . . . . . . . . . . . . . 31 14.1. Normative References . . . . . . . . . . . . . . . . . . 32
14.2. Informative References . . . . . . . . . . . . . . . . . 31 14.2. Informative References . . . . . . . . . . . . . . . . . 32
Appendix A. Legacy INFO Usage . . . . . . . . . . . . . . . . . . 33 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 34
A.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 33 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 35
A.2. ISUP . . . . . . . . . . . . . . . . . . . . . . . . . . 33
A.3. QSIG . . . . . . . . . . . . . . . . . . . . . . . . . . 34
A.4. MSCML . . . . . . . . . . . . . . . . . . . . . . . . . . 34
A.5. MSML . . . . . . . . . . . . . . . . . . . . . . . . . . 34
A.6. Video Fast Update . . . . . . . . . . . . . . . . . . . . 34
A.7. DTMF . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 34
Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 38 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 38
1. Introduction 1. Introduction
This document defines a method, INFO, for the Session Initiation This document defines a method, INFO, for the Session Initiation
Protocol (SIP) [RFC3261]. Protocol (SIP) [RFC3261].
The purpose of the INFO message is to carry application level The purpose of the INFO message is to carry application level
information between endpoints, using the SIP dialog signaling path. information between endpoints, using the SIP dialog signaling path.
Note that the INFO method is not used to update characteristics of a Note that the INFO method is not used to update characteristics of a
skipping to change at page 4, line 46 skipping to change at page 4, line 46
NOTE: A UA can use an empty Recv-Info header field (a header field NOTE: A UA can use an empty Recv-Info header field (a header field
without a value) to indicate that it is not willing to receive INFO without a value) to indicate that it is not willing to receive INFO
requests for any Info-Package, but to inform other UAs that it still requests for any Info-Package, but to inform other UAs that it still
supports the Info Package mechanism. supports the Info Package mechanism.
When a UA sends an INFO request, it uses the Info-Package header When a UA sends an INFO request, it uses the Info-Package header
field to indicate which Info Package is associated with the request. field to indicate which Info Package is associated with the request.
One particular INFO request can only be associated with a single Info One particular INFO request can only be associated with a single Info
Package. Package.
2. Applicability 2. Motivation
A number of applications, standardized and proprietary, make use of
the INFO method as it was previously defined in RFC 2976 [RFC2976],
referred to as "legacy INFO usage". These include but are not
limited to:
o RFC 3372 [RFC3372] specifies the encapsulation of ISDN User Part
(ISUP) in SIP message bodies. ITU-T and 3GPP have specified
similar procedures.
o [Ecma-355] specifies the encapsulation of QSIG in SIP message
bodies.
o RFC 5022 [RFC5022] specifies how INFO is used as a transport
mechanism by the Media Server Control Markup Language (MSCML)
protocol. MSCML uses an option-tag in the Require header field to
ensure that the receiver understands the INFO content.
o RFC 5707 [RFC5707] specifies how INFO us used as a transport
mechanism by the Media Server Markup Language (MSML) protocol.
o Companies have been using INFO messages in order to request fast
video update. Currently a standardized mechanism, based on RTCP,
has been specified in RFC 5168 [RFC5168].
o Companies have been using INFO messages in order to transport DTMF
tones. All mechanisms are proprietary, and have not been
standardized.
Some legacy INFO usages are also recognized as being shortcuts to
more appropriate and flexible mechanisms.
Furthermore, RFC 2976 did not define mechanisms that would enable a
SIP UA to indicate (1) the types of applications and contexts in
which they support the INFO method or (2) the types of application
and context with which a specific INFO message is associated.
Because legacy INFO usages do not have associated Info Packages, it
is not possible to use the Recv-Info and Info-Package header fields
with legacy INFO usages. That is, a UA cannot use the Recv-Info
header field to indicate for which legacy INFO usages it is willing
to receive INFO requests, and a UA cannot use the Info-Package header
field to indicate for which legacy INFO usage an INFO request is
associated with.
Due to the problems described above, legacy INFO usages often require
static configuration about for what type of applications and contexts
UAs support the INFO method, and the way they handle application
information transported in INFO messages. That has caused
interoperability problems in the industry.
To overcome these problems, the SIP Working Group has spent
significant discussion time over many years coming to agreement on
whether it was more appropriate to fix INFO (by defining a
registration mechanism for the ways in which it was used) or to
deprecate it altogether (with the usage described in RFC 3398
[RFC3398] being grandfathered as the sole legitimate usage).
Although it required substantial consensus building and concessions
by those more inclined to completely deprecate INFO, the eventual
direction of the working group was to publish a framework for
registration of INFO packages as defined in this specification.
3. Applicability and Backward Compatibility
This document defines a method, INFO, for the Session Initiation This document defines a method, INFO, for the Session Initiation
Protocol (SIP) [RFC3261], and an Info Package mechanism. The Protocol (SIP) [RFC3261], and an Info Package mechanism. The
document obsoletes [RFC2976]. For backward compatibility the document obsoletes RFC 2976 [RFC2976]. For backward compatibility,
document also specifies a "legacy" mode of usage of the INFO method the document also specifies a "legacy" mode of usage of the INFO
that is compatible with the usage previously defined in [RFC2976], method that is compatible with the usage previously defined in RFC
referred to as "legacy INFO Usage" in this document. 2976, referred to as "legacy INFO Usage".
3. The INFO Method For backward compatibility purposes, this document does not deprecate
legacy INFO usages, and does not mandate users to define Info
Packages for such usages. However:
3.1. General 1. A UA MUST NOT insert an Info-Package header field in a legacy
INFO request (as described in Section 3, an INFO request
associated with an Info Package always contains an Info-Package
header field).
2. It is strongly RECOMMENDED that any new usage uses the Info
Package mechanism defined in this specification, since it does
not share the issues associated with legacy INFO usage, and since
Info Packages can be registered with IANA.
3. UAs are allowed to enable both legacy INFO usages and Info
Package usages as part of the same invite dialog usage, but UAs
SHALL NOT mix legacy INFO usages and Info Package usages in order
to transport the same application level information. If
possible, UAs SHALL prefer the usage of an Info Package.
4. The INFO Method
4.1. General
The INFO method provides a mechanism for transporting application The INFO method provides a mechanism for transporting application
level information that can further enhance a SIP application. Annex level information that can further enhance a SIP application. Annex
A gives more details on the types of applications for which the use A gives more details on the types of applications for which the use
of INFO is appropriate. of INFO is appropriate.
This section describes how a UA handles INFO requests and responses, This section describes how a UA handles INFO requests and responses,
as well as the message bodies included in INFO messages. as well as the message bodies included in INFO messages.
3.2. INFO Request 4.2. INFO Request
4.2.1. INFO Request Sender
3.2.1. INFO Request Sender
An INFO request can be associated with an Info Package (see An INFO request can be associated with an Info Package (see
Section 4), or associated with a legacy INFO usage (see Section 9). Section 5), or associated with a legacy INFO usage (see Section 2).
The construction of the INFO request is the same as any other non- The construction of the INFO request is the same as any other non-
target refresh request within an existing invite dialog usage as target refresh request within an existing invite dialog usage as
described in Section 12.2 of [RFC3261]. described in Section 12.2 of RFC 3261.
When a UA sends an INFO request associated with an Info Package, it When a UA sends an INFO request associated with an Info Package, it
MUST include an Info-Package header field that indicates which Info MUST include an Info-Package header field that indicates which Info
Package is associated with the request. A specific INFO request can Package is associated with the request. A specific INFO request can
be used only for a single Info Package. be used only for a single Info Package.
When a UA sends an INFO request associated with an legacy INFO usage When a UA sends an INFO request associated with an legacy INFO usage
there is no Info Package associated with the request, and the UA MUST there is no Info Package associated with the request, and the UA MUST
NOT include an Info-Package header field in the request. NOT include an Info-Package header field in the request.
The INFO request MUST NOT contain a Recv-Info header field. A UA can The INFO request MUST NOT contain a Recv-Info header field. A UA can
only indicate a set of Info Packages for which it is willing to only indicate a set of Info Packages for which it is willing to
receive INFO requests by using the SIP methods (and their responses) receive INFO requests by using the SIP methods (and their responses)
listed in Section 4. listed in Section 5.
A UA MUST NOT send an INFO request outside an invite dialog usage and A UA MUST NOT send an INFO request outside an invite dialog usage and
MUST NOT send an INFO request for an Info Package inside an invite MUST NOT send an INFO request for an Info Package inside an invite
dialog usage if the remote UA has not indicated willingness to dialog usage if the remote UA has not indicated willingness to
receive that Info-Package within that dialog. receive that Info-Package within that dialog.
If a UA receives a 469 (Bad Info Package) response to an INFO If a UA receives a 469 (Bad Info Package) response to an INFO
request, based on [RFC5057] the response represents a Transaction request, based on RFC 5057 the response represents a Transaction Only
Only failure, and the UA MUST NOT terminate the invite dialog usage. failure, and the UA MUST NOT terminate the invite dialog usage.
Due to the possibility of forking, the UA which sends the initial Due to the possibility of forking, the UA which sends the initial
INVITE request MUST be prepared to receive INFO requests from INVITE request MUST be prepared to receive INFO requests from
multiple remote UAs during the early dialog phase. In addition, the multiple remote UAs during the early dialog phase. In addition, the
UA MUST be prepared to receive different Recv-Info header field UA MUST be prepared to receive different Recv-Info header field
values from different remote UAs. values from different remote UAs.
NOTE: If the UAS (receiver of the initial INVITE request) sends an NOTE: If the UAS (receiver of the initial INVITE request) sends an
INFO request just after it has sent the response which creates the INFO request just after it has sent the response which creates the
dialog, the UAS needs to be prepared that the INFO request can reach dialog, the UAS needs to be prepared that the INFO request can reach
the UAC before the dialog creating response, and might therefore be the UAC before the dialog creating response, and might therefore be
rejected by the UAC. In addition, an INFO request might be rejected rejected by the UAC. In addition, an INFO request might be rejected
due to a race condition, if a UA sends the INFO request at the same due to a race condition, if a UA sends the INFO request at the same
time as the remote UA sends a new set of Info Packages for which it time as the remote UA sends a new set of Info Packages for which it
is willing to receive INFO requests. is willing to receive INFO requests.
3.2.2. INFO Request Receiver 4.2.2. INFO Request Receiver
If a UA receives an INFO request associated with an Info Package that 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 the UA has not indicated willingness to receive, the UA MUST send a
469 (Bad Info Package) response (see Section 11.6), which contains a 469 (Bad Info Package) response (see Section 11.6), which contains a
Recv-Info header field with Info Packages for which the UA is willing Recv-Info header field with Info Packages for which the UA is willing
to receive INFO requests. The UA MUST NOT use the response to update to receive INFO requests. The UA MUST NOT use the response to update
the set of Info Packages, but simply to indicate the current set. In the set of Info Packages, but simply to indicate the current set. In
the terminology of Multiple Dialog Usages [RFC5057], this represents the terminology of Multiple Dialog Usages [RFC5057], this represents
a Transaction Only failure, and does not terminate the invite dialog a Transaction Only failure, and does not terminate the invite dialog
usage. usage.
If a UA receives an INFO request associated with an Info Package and If a UA receives an INFO request associated with an Info Package and
the message body part with Content-Disposition 'Info-Package' (see the message body part with Content-Disposition 'Info-Package' (see
Section 3.3.1) has a Multipurpose Internet Mail Extensions (MIME) Section 4.3.1) has a Multipurpose Internet Mail Extensions (MIME)
type that the UA supports but not in the context of that Info type that the UA supports but not in the context of that Info
Package, it is RECOMMENDED that the UA send a 415 (Unsupported Media Package, it is RECOMMENDED that the UA send a 415 (Unsupported Media
Type) response. Type) response.
The UA MAY send other error responses, such as Request Failure (4xx), The UA MAY send other error responses, such as Request Failure (4xx),
Server Failure (5xx) and Global Failure (6xx), in accordance with the Server Failure (5xx) and Global Failure (6xx), in accordance with the
error handling procedures in [RFC3261]. error handling procedures defined in RFC 3261.
Otherwise, if the INFO request is syntactically correct and well Otherwise, if the INFO request is syntactically correct and well
structured, the UA MUST send a 200 (OK) response. structured, the UA MUST send a 200 (OK) response.
NOTE: If the application needs to reject the information which it NOTE: If the application needs to reject the information which it
received in an INFO request, that needs to be done on the application received in an INFO request, that needs to be done on the application
level. I.e. the application needs to trigger a new INFO request, level. I.e. the application needs to trigger a new INFO request,
which contains information that the previously received application which contains information that the previously received application
data was not accepted. Individual Info Package specifications need data was not accepted. Individual Info Package specifications need
to describe the details for such procedures. to describe the details for such procedures.
3.2.3. SIP Proxies 4.2.3. SIP Proxies
Proxies need no additional behavior beyond that described in Proxies need no additional behavior beyond that described in RFC 3261
[RFC3261] to support INFO. to support INFO.
3.3. INFO Message Body 4.3. INFO Message Body
3.3.1. INFO Request Message Body 4.3.1. INFO Request Message Body
The purpose of the INFO request is to carry application level The purpose of the INFO request is to carry application level
information between SIP UAs. The application information data is information between SIP UAs. The application information data is
carried in the payload of the message body of the INFO request. carried in the payload of the message body of the INFO request.
NOTE: An INFO request associated with an Info Package can also NOTE: An INFO request associated with an Info Package can also
include information associated with the Info Package using Info- include information associated with the Info Package using Info-
Package header field parameters. Package header field parameters.
If an INFO request associated with an Info Package contains a message If an INFO request associated with an Info Package contains a message
body part, the body part is identified by a Content-Disposition body part, the body part is identified by a Content-Disposition
header field 'Info-Package' value. The body part can contain a header field 'Info-Package' value. The body part can contain a
single MIME type, or it can be a multipart [RFC5621] which contains single MIME type, or it can be a multipart [RFC5621] which contains
other body parts associated with the Info Package. other body parts associated with the Info Package.
UAs MUST support multipart body parts in accordance with [RFC5621]. UAs MUST support multipart body parts in accordance with RFC 5621.
NOTE: An INFO request can also contain other body parts that are NOTE: An INFO request can also contain other body parts that are
meaningful within the context of an invite dialog usage but are not meaningful within the context of an invite dialog usage but are not
specifically associated with the INFO method and the application specifically associated with the INFO method and the application
concerned. concerned.
When a UA supports a specific Info-Package, the UA MUST also support When a UA supports a specific Info-Package, the UA MUST also support
message body MIME types in accordance with that Info-Package. message body MIME types in accordance with that Info-Package.
However, in accordance with [RFC3261] the UA still indicates the However, in accordance with RFC 3261 the UA still indicates the
supported MIME types using the Accept header. supported MIME types using the Accept header.
3.3.2. INFO Response Message Body 4.3.2. INFO Response Message Body
A UA MUST NOT include a message body associated with an Info Package A UA MUST NOT include a message body associated with an Info Package
in an INFO response. Message bodies associated with Info Packages in an INFO response. Message bodies associated with Info Packages
MUST only be sent in INFO requests. MUST only be sent in INFO requests.
A UA MAY include a message body which is not associated with an Info A UA MAY include a message body which is not associated with an Info
Package in an INFO response. Package in an INFO response.
3.4. Order of Delivery 4.4. Order of Delivery
The Info Package mechanism does not define a delivery order The Info Package mechanism does not define a delivery order
mechanism. Info Packages can rely on the CSeq header field to detect mechanism. Info Packages can rely on the CSeq header field to detect
if an INFO request is received out of order. if an INFO request is received out of order.
If specific applications need additional mechanisms for order of If specific applications need additional mechanisms for order of
delivery, those mechanisms, and related procedures, are specified as delivery, those mechanisms, and related procedures, are specified as
part of the associated Info Package (e.g. the use of sequence numbers part of the associated Info Package (e.g. the use of sequence numbers
within the application data). within the application data).
4. Info Packages 5. Info Packages
4.1. General 5.1. General
An Info Package specification defines the content and semantics of An Info Package specification defines the content and semantics of
the information carried in an INFO message associated with an Info the information carried in an INFO message associated with an Info
Package. The Info Package mechanism provides a way for UAs to Package. The Info Package mechanism provides a way for UAs to
indicate for which Info Packages they are willing to receive INFO indicate for which Info Packages they are willing to receive INFO
requests, and which Info Package a specific INFO request is requests, and which Info Package a specific INFO request is
associated with. associated with.
4.2. User Agent Behavior 5.2. User Agent Behavior
4.2.1. General 5.2.1. General
This section describes how a UA handles Info Packages, how a UA uses This section describes how a UA handles Info Packages, how a UA uses
the Recv-Info header field, and how the UA acts in re-INVITE rollback the Recv-Info header field, and how the UA acts in re-INVITE rollback
situations. situations.
4.2.2. UA Procedures 5.2.2. UA Procedures
A UA which supports the Info Package mechanism MUST indicate, using A UA which supports the Info Package mechanism MUST indicate, using
the Recv-Info header field, the set of Info Packages for which it is the Recv-Info header field, the set of Info Packages for which it is
willing to receive INFO requests for a specific session. A UA can willing to receive INFO requests for a specific session. A UA can
list multiple Info Packages in a single Recv-Info header field, and list multiple Info Packages in a single Recv-Info header field, and
the UA can use multiple Recv-Info header fields. A UA can use an the UA can use multiple Recv-Info header fields. A UA can use an
empty Recv-Info header field, i.e. a header field without any header empty Recv-Info header field, i.e. a header field without any header
field values. field values.
A UA provides its set of Info Packages for which it is willing to A UA provides its set of Info Packages for which it is willing to
skipping to change at page 9, line 47 skipping to change at page 11, line 28
If a UA indicates multiple Info Packages, which provide similar If a UA indicates multiple Info Packages, which provide similar
functionality, it is not possible to indicate a priority order of the functionality, it is not possible to indicate a priority order of the
Info Packages, or to indicate that the UA wishes to only receive INFO Info Packages, or to indicate that the UA wishes to only receive INFO
requests for one of the Info Packages. It is up to the application requests for one of the Info Packages. It is up to the application
logic associated with the Info Packages, and specific Info Package logic associated with the Info Packages, and specific Info Package
specifications, to describe application behavior in such cases. specifications, to describe application behavior in such cases.
For backward compatibility purpose, even if a UA indicates support of For backward compatibility purpose, even if a UA indicates support of
the Info Package mechanism, it is still allowed to enable legacy INFO the Info Package mechanism, it is still allowed to enable legacy INFO
usages Section 9. In addition, if a UA indicates support of the INFO usages. In addition, if a UA indicates support of the INFO method
method using the Allow header field [RFC3261], it does not implicitly using the Allow header field [RFC3261], it does not implicitly
indicate support of the Info Package mechanism. A UA MUST use the indicate support of the Info Package mechanism. A UA MUST use the
Recv-Info header field in order to indicate that it supports the Info Recv-Info header field in order to indicate that it supports the Info
Package mechanism. Likewise, even if a UA uses the Recv-Info header Package mechanism. Likewise, even if a UA uses the Recv-Info header
field to indicate that it supports the Info Package mechanism, in field to indicate that it supports the Info Package mechanism, in
addition the UA still indicates support of the INFO method using the addition the UA still indicates support of the INFO method using the
Allow header. Allow header.
This document does not define a SIP option tag [RFC3261] for the Info This document does not define a SIP option tag [RFC3261] for the Info
Package mechanism. However, an Info Package specification can define Package mechanism. However, an Info Package specification can define
an option-tag associated with the specific Info Package, as described an option-tag associated with the specific Info Package, as described
in Section 10.6. in Section 10.6.
4.2.3. Recv-Info header field rules 5.2.3. Recv-Info header field rules
The text below defines rules on when a UA is required to include a The text below defines rules on when a UA is required to include a
Recv-Info header field in SIP messages. Section 6.1 lists the SIP Recv-Info header field in SIP messages. Section 7.1 lists the SIP
methods, for which a UA can insert a Recv-Info header field in methods, for which a UA can insert a Recv-Info header field in
requests and responses. requests and responses.
- The sender of an initial INVITE request MUST include a Recv-Info - The sender of an initial INVITE request MUST include a Recv-Info
header field in the initial INVITE request, even if the sender is not header field in the initial INVITE request, even if the sender is not
willing to receive INFO requests associated with any Info Package. willing to receive INFO requests associated with any Info Package.
- The receiver of a request which contains a Recv-Info header field - The receiver of a request which contains a Recv-Info header field
MUST include a Recv-Info header field in a reliable 18x/2xx response MUST include a Recv-Info header field in a reliable 18x/2xx response
to the request, even if the request contains an empty Recv-Info to the request, even if the request contains an empty Recv-Info
skipping to change at page 10, line 45 skipping to change at page 12, line 26
not restricted to generate its own set of Info Packages as a subset not restricted to generate its own set of Info Packages as a subset
of the Info Package set received in the Info Package header field of of the Info Package set received in the Info Package header field of
the request. the request.
Similar to SDP answers, the receiver can include the same Recv-Info Similar to SDP answers, the receiver can include the same Recv-Info
header field value in multiple responses (18x/2xx) for the same header field value in multiple responses (18x/2xx) for the same
INVITE/re-INVITE transaction, but the receiver MUST use the same INVITE/re-INVITE transaction, but the receiver MUST use the same
Recv-Info header field value (if included) in all responses for the Recv-Info header field value (if included) in all responses for the
same transaction. same transaction.
4.2.4. Info Package fallback rules 5.2.4. Info Package fallback rules
If the receiver of a request which contains a Recv-Info header field If the receiver of a request which contains a Recv-Info header field
rejects the request, both the sender and receiver of the request MUST rejects the request, both the sender and receiver of the request MUST
roll back to the set of Info Packages which was used before the roll back to the set of Info Packages which was used before the
request was sent. This also applies to the case where the receiver request was sent. This also applies to the case where the receiver
of an INVITE/re-INVITE request has included a Recv-Info header field of an INVITE/re-INVITE request has included a Recv-Info header field
in a provisional response, but later rejects the request. in a provisional response, but later rejects the request.
NOTE: The dialog state rollback rules for Info Packages might differ NOTE: The dialog state rollback rules for Info Packages might differ
from the rules for other types of dialog state information (SDP, from the rules for other types of dialog state information (SDP,
target, etc). target, etc).
4.3. REGISTER Processing 5.3. REGISTER Processing
This document allows a UA to insert a Recv-Info header field in a This document allows a UA to insert a Recv-Info header field in a
REGISTER request. However, a UA SHALL NOT include a header value for REGISTER request. However, a UA SHALL NOT include a header value for
a specific Info Package unless the specific Info Package a specific Info Package unless the specific Info Package
specification describes how the header field value shall be specification describes how the header field value shall be
interpreted and used by the registrar, e.g. in order to determine interpreted and used by the registrar, e.g. in order to determine
request targets. request targets.
Rather than using the Recv-Info header field in order to determine Rather than using the Recv-Info header field in order to determine
request targets, it is recommended to use more appropriate request targets, it is recommended to use more appropriate
mechanisms, e.g. based on [RFC3840]. However, this document does not mechanisms, e.g. based on RFC 3840 [RFC3840]. However, this document
define a feature tag for the Info Package mechanism, or a mechanism does not define a feature tag for the Info Package mechanism, or a
to define feature tags for specific Info Packages. mechanism to define feature tags for specific Info Packages.
5. Formal INFO Method Definition 6. Formal INFO Method Definition
5.1. INFO Method 6.1. INFO Method
This document describes one new SIP method: INFO. This document This document describes one new SIP method: INFO. This document
replaces the definition and registrations found in [RFC2976]. replaces the definition and registrations found in RFC 2976
[RFC2976].
This table expands on Tables 2 and 3 in [RFC3261]. This table expands on Tables 2 and 3 in RFC 3261 [RFC3261].
Header Where INFO Header Where INFO
------ ----- ---- ------ ----- ----
Accept R o Accept R o
Accept 415 o Accept 415 o
Accept-Encoding R o Accept-Encoding R o
Accept-Encoding 2xx o Accept-Encoding 2xx o
Accept-Encoding 415 c Accept-Encoding 415 c
Accept-Language R o Accept-Language R o
Accept-Language 2xx o Accept-Language 2xx o
skipping to change at page 13, line 12 skipping to change at page 14, line 39
To c m (w/ Tag) To c m (w/ Tag)
Unsupported 420 o Unsupported 420 o
User-Agent o User-Agent o
Via m Via m
Warning r o Warning r o
WWW-Authenticate 401 m WWW-Authenticate 401 m
WWW-Authenticate 407 o WWW-Authenticate 407 o
Figure 1: Table 1: Summary of Header Fields Figure 1: Table 1: Summary of Header Fields
6. INFO Header Fields 7. INFO Header Fields
6.1. General 7.1. General
This table expands on tables 2 and 3 in [RFC3261]. This table expands on tables 2 and 3 in RFC 3261 [RFC3261].
Header field where proxy ACK BYE CAN INV OPT REG PRA INF MSG UPD Header field where proxy ACK BYE CAN INV OPT REG PRA INF MSG UPD
------------------------------------------------------------------ ------------------------------------------------------------------
Info-Package R - - - - - - - m* - - Info-Package R - - - - - - - m* - -
Recv-Info R - - - m - o o - - o Recv-Info R - - - m - o o - - o
Recv-Info 2xx - - - o** - - o***- - o*** Recv-Info 2xx - - - o** - - o***- - o***
Recv-Info 1xx - - - o** - - - - - - Recv-Info 1xx - - - o** - - - - - -
Recv-Info 469 - - - - - - - m* - - Recv-Info 469 - - - - - - - m* - -
Recv-Info r - - - o - - o - - o Recv-Info r - - - o - - o - - o
skipping to change at page 14, line 8 skipping to change at page 15, line 38
* Not applicable to INFO requests and responses associated with * Not applicable to INFO requests and responses associated with
legacy INFO usages. legacy INFO usages.
** Mandatory in at least one reliable 18x/2xx response, if sent, ** Mandatory in at least one reliable 18x/2xx response, if sent,
to the INVITE request, if the associated INVITE request contained to the INVITE request, if the associated INVITE request contained
a Recv-Info header field. a Recv-Info header field.
*** Mandatory if the associated request contained a Recv-Info *** Mandatory if the associated request contained a Recv-Info
header field. header field.
As defined in section 20 of RFC 3261 [RFC3261], a "mandatory" As defined in section 20 of RFC 3261, a "mandatory" header field
header field MUST be present in a request, and MUST be understood MUST be present in a request, and MUST be understood by the UAS
by the UAS receiving the request." receiving the request."
6.2. Info-Package header field 7.2. Info-Package header field
This document adds Info-Package to the definition of the element This document adds Info-Package to the definition of the element
"message-header" in the SIP message grammar [RFC3261]. Section 3 "message-header" in the SIP message grammar [RFC3261]. Section 4
describes the Info-Package header field usage. describes the Info-Package header field usage.
For the purposes of matching Info Package types indicated in Recv- For the purposes of matching Info Package types indicated in Recv-
Info with those in the Info-Package header field value, one compares 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 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 Info-Package header field octet-by-octet with that of the Recv-Info
header field value. That is, the Info Package name is case header field value. That is, the Info Package name is case
sensitive. Info-package-param is not part of the comparison-checking sensitive. Info-package-param is not part of the comparison-checking
algorithm. algorithm.
This document does not define values for Info-Package types. This document does not define values for Info-Package types.
Individual Info Package specifications define these values. Individual Info Package specifications define these values.
6.3. Recv-Info header field 7.3. Recv-Info header field
This document adds Recv-Info to the definition of the element This document adds Recv-Info to the definition of the element
"message-header" in the SIP message grammar [RFC3261]. Section 4 "message-header" in the SIP message grammar [RFC3261]. Section 5
describes the Recv-Info header field usage. describes the Recv-Info header field usage.
7. Info Package Considerations 8. Info Package Considerations
7.1. General 8.1. General
This section covers considerations to take into account when deciding This section covers considerations to take into account when deciding
whether the usage of an Info Package is appropriate for transporting whether the usage of an Info Package is appropriate for transporting
of application information for a specific use-case. of application information for a specific use-case.
7.2. Appropriateness of Info Package Usage 8.2. Appropriateness of Info Package Usage
When designing an Info Package, for application level information When designing an Info Package, for application level information
exchange, it is important to consider: is signaling, using INFO exchange, it is important to consider: is signaling, using INFO
requests, within a SIP dialog, an appropriate mechanism for the use- requests, within a SIP dialog, an appropriate mechanism for the use-
case? Is it because it is the most reasonable and appropriate case? Is it because it is the most reasonable and appropriate
choice, or merely because "it's easy"? Choosing an inappropriate choice, or merely because "it's easy"? Choosing an inappropriate
mechanism for a specific use-case can cause negative effects in SIP mechanism for a specific use-case can cause negative effects in SIP
networks where the mechanism is used. networks where the mechanism is used.
7.3. Alternative Mechanisms 8.3. Alternative Mechanisms
7.3.1. Alternative SIP signaling plane mechanisms 8.3.1. Alternative SIP signaling plane mechanisms
7.3.1.1. General 8.3.1.1. General
This subsection describes some alternative mechanisms for This subsection describes some alternative mechanisms for
transporting application information on the SIP signaling plane, transporting application information on the SIP signaling plane,
using SIP messages. using SIP messages.
7.3.1.2. INFO Request Rate and Volume 8.3.1.2. INFO Request Rate and Volume
INFO messages differ from many other sorts of SIP messages in that INFO messages differ from many other sorts of SIP messages in that
they carry application information, and the size and rate of the INFO they carry application information, and the size and rate of the INFO
message is directly determined by the application. This can cause message is directly determined by the application. This can cause
application information traffic to interfere with other traffic on application information traffic to interfere with other traffic on
that infrastructure, or to self-interfere when data rates become too that infrastructure, or to self-interfere when data rates become too
high. high.
There is no default throttling mechanism for INFO requests. Apart There is no default throttling mechanism for INFO requests. Apart
from the SIP session establishment, the number of SIP messages from the SIP session establishment, the number of SIP messages
skipping to change at page 16, line 6 skipping to change at page 17, line 37
exchange of bulk data beyond these limits, especially if the headers exchange of bulk data beyond these limits, especially if the headers
plus body exceed the User Datagram Protocol (UDP) MTU [RFC0768]. plus body exceed the User Datagram Protocol (UDP) MTU [RFC0768].
Appropriate mechanisms for such traffic include the Hypertext Appropriate mechanisms for such traffic include the Hypertext
Transfer Protocol (HTTP) [RFC2616], the Message Session Relay Transfer Protocol (HTTP) [RFC2616], the Message Session Relay
Protocol (MSRP) [RFC4975], or other media plane data transport Protocol (MSRP) [RFC4975], or other media plane data transport
mechanisms. mechanisms.
RFC 5405 [RFC5405] provides additional guidelines for applications RFC 5405 [RFC5405] provides additional guidelines for applications
using UDP that may be useful background reading. using UDP that may be useful background reading.
7.3.1.3. SUBSCRIBE/NOTIFY 8.3.1.3. SUBSCRIBE/NOTIFY
An alternative for application level interaction is to use An alternative for application level interaction is to use
subscription-based events [RFC3265], which uses the SIP SUBSCRIBE and subscription-based events [RFC3265], which uses the SIP SUBSCRIBE and
NOTIFY methods. Using that mechanism, a UA requests state NOTIFY methods. Using that mechanism, a UA requests state
information, such as key pad presses from a device to an application information, such as key pad presses from a device to an application
server or key map images from an application server to a device. server or key map images from an application server to a device.
Event Packages [RFC3265] perform the role of disambiguating the Event Packages [RFC3265] perform the role of disambiguating the
context of a message for subscription-based events. The Info Package context of a message for subscription-based events. The Info Package
mechanism provides similar functionality for application information mechanism provides similar functionality for application information
skipping to change at page 16, line 40 skipping to change at page 18, line 23
and B2BUAs, the resource impact caused by the subscription dialogs and B2BUAs, the resource impact caused by the subscription dialogs
needs to be considered. The number of subscription dialogs per user needs to be considered. The number of subscription dialogs per user
also needs to be considered. also needs to be considered.
As for any other SIP signaling plane based mechanism for transporting As for any other SIP signaling plane based mechanism for transporting
application information, the SUBSCRIBE/NOTIFY messages can put a application information, the SUBSCRIBE/NOTIFY messages can put a
significant burden on intermediate SIP entities which are part of the significant burden on intermediate SIP entities which are part of the
dialog route set, but do not have any interest in the application dialog route set, but do not have any interest in the application
information transported between the end users. information transported between the end users.
7.3.1.4. MESSAGE 8.3.1.4. MESSAGE
The MESSAGE method [RFC3428] defines one-time instant message The MESSAGE method [RFC3428] defines one-time instant message
exchange, typically for sending MIME contents for rendering to the exchange, typically for sending MIME contents for rendering to the
user. user.
7.3.2. Media Plane Mechanisms 8.3.2. Media Plane Mechanisms
7.3.2.1. General 8.3.2.1. General
In SIP, media plane channels associated with SIP dialogs are In SIP, media plane channels associated with SIP dialogs are
established using SIP signaling, but the data exchanged on the media established using SIP signaling, but the data exchanged on the media
plane channel does not traverse SIP signaling intermediates, so if plane channel does not traverse SIP signaling intermediates, so if
there will be a lot of information exchanged, and there is no need there will be a lot of information exchanged, and there is no need
for the SIP signaling intermediaries to examine the information, it for the SIP signaling intermediaries to examine the information, it
is recommended to use a media plane mechanism, rather than a SIP is recommended to use a media plane mechanism, rather than a SIP
signaling based. signaling based.
A low latency requirement for the exchange of information is one A low latency requirement for the exchange of information is one
strong indicator for using a media channel. Exchanging information strong indicator for using a media channel. Exchanging information
through the SIP routing network can introduce hundreds of through the SIP routing network can introduce hundreds of
milliseconds of latency. milliseconds of latency.
7.3.2.2. MRCP 8.3.2.2. MRCP
One mechanism for media plane exchange of application data is the One mechanism for media plane exchange of application data is the
Media Resource Control Protocol (MRCP) [I-D.ietf-speechsc-mrcpv2], Media Resource Control Protocol (MRCP) [I-D.ietf-speechsc-mrcpv2],
where a media plane connection-oriented channel, such as a where a media plane connection-oriented channel, such as a
Transmission Control Protocol (TCP) [RFC0793] or Stream Control Transmission Control Protocol (TCP) [RFC0793] or Stream Control
Transmission Protocol (SCTP) [RFC4960] stream is established. Transmission Protocol (SCTP) [RFC4960] stream is established.
7.3.2.3. MRSP 8.3.2.3. MRSP
MSRP [RFC4975] defines session-based instant messaging as well as MSRP [RFC4975] defines session-based instant messaging as well as
bulk file transfer and other such large-volume uses. bulk file transfer and other such large-volume uses.
7.3.3. Non-SIP related mechanisms 8.3.3. Non-SIP related mechanisms
Another alternative is to use a SIP-independent mechanism, such as Another alternative is to use a SIP-independent mechanism, such as
HTTP [RFC2616]. In this model, the UA knows about a rendezvous point HTTP [RFC2616]. In this model, the UA knows about a rendezvous point
to direct HTTP requests to for the transfer of information. Examples to direct HTTP requests to for the transfer of information. Examples
include encoding of a prompt to retrieve in the SIP Request URI in 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- [RFC4240] or the encoding of a SUBMIT target in a VoiceXML [W3C.REC-
voicexml21-20070619] script. voicexml21-20070619] script.
8. Syntax 9. Syntax
8.1. General 9.1. General
This section describes the syntax extensions to the ABNF syntax This section describes the syntax extensions to the ABNF syntax
defined in [RFC3261] required for the INFO method, and adds defined in RFC 3261 required for the INFO method, and adds
definitions for the Info-Package and Recv-Info header fields. The definitions for the Info-Package and Recv-Info header fields. The
previous sections describe the semantics. The ABNF defined in this previous sections describe the semantics. The ABNF defined in this
specification is conformant to [RFC5234]. specification is conformant to RFC 5234 [RFC5234].
8.2. ABNF 9.2. ABNF
INFOm = %x49.4E.46.4F ; INFO in caps INFOm = %x49.4E.46.4F ; INFO in caps
Method =/ INFOm Method =/ INFOm
message-header =/ (Info-Package / Recv-Info) CRLF message-header =/ (Info-Package / Recv-Info) CRLF
Info-Package = "Info-Package" HCOLON Info-package-type Info-Package = "Info-Package" HCOLON Info-package-type
Recv-Info = "Recv-Info" HCOLON [Info-package-list] Recv-Info = "Recv-Info" HCOLON [Info-package-list]
Info-package-list = Info-package-type *( COMMA Info-package-type ) Info-package-list = Info-package-type *( COMMA Info-package-type )
Info-package-type = Info-package-name *( SEMI Info-package-param) Info-package-type = Info-package-name *( SEMI Info-package-param)
Info-package-name = token Info-package-name = token
Info-package-param = generic-param Info-package-param = generic-param
9. Legacy INFO Usage
9.1. General
A number of applications, standardized and proprietary, make use of
the INFO method as it was previously defined in [RFC2976], referred
to as "legacy INFO usage".
For backward compatibility purpose, this document does not deprecate
such usages, and does not mandate users to define Info Packages for
such usages. However, it is strongly RECOMMENDED that any new usage
uses the Info Package mechanism defined in this specification, since
it does not share the issues associated with legacy INFO usage, and
since Info Packages can be registered with IANA.
9.2. Problems
While legacy INFO usage has been widely adopted for specific
application use cases, [RFC2976] did not define a mechanism for SIP
UAs to indicate for which types of applications and contexts they
support the INFO method. In addition, [RFC2976] did not provide a
mechanism to explicitly indicate the type of application and context
for which a specific INFO message is associated.
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.
Since legacy INFO usages do not have associated Info Packages, it is
not possible to use the Recv-Info and Info-Package header fields with
legacy INFO usages. That is, a UA cannot use the Recv-Info header
field to indicate for which legacy INFO usages it is willing to
receive INFO requests, and a UA cannot use the Info-Package header
field to indicate for which legacy INFO usage an INFO request is
associated with.
Due to the problems described above, legacy INFO usages often require
static configuration about for what type of applications and contexts
UAs support the INFO method, and the way they handle application
information transported in INFO messages. That has caused
interoperability problems in the industry. Therefore, a need for a
well defined and documented description of what the information sent
in the INFO is used for has been identified. This situation is
analogous to the context issue in Internet Mail [RFC3458].
Section 4.1 describes how the Info Package mechanisms solves the
issues associated with legacy INFO usages.
9.3. Co-existence with Info Package based INFO usage
As described in Section 3, an INFO request associated with an Info
Package always contains an Info-Package header field. A UA MUST NOT
insert an Info-Package header field in a legacy INFO request.
UAs are allowed to enable both legacy INFO usages and Info Package
usages as part of the same invite dialog usage. However, UAs SHALL
NOT mix legacy INFO usages and Info Package usages in order to
transport the same application level information. If possible, UAs
SHALL prefer the usage of an Info Package.
See Appendix A for examples of existing legacy INFO usages.
10. Info Package Requirements 10. Info Package Requirements
10.1. General 10.1. General
This section provides guidance on how to define an Info Package, and This section provides guidance on how to define an Info Package, and
what information needs to exist in an Info Package specification. what information needs to exist in an Info Package specification.
If, for an Info Package, there is a need to extend or modify the If, for an Info Package, there is a need to extend or modify the
behavior described in this document, that behavior MUST be described behavior described in this document, that behavior MUST be described
in the Info Package specification. It is bad practice for Info in the Info Package specification. It is bad practice for Info
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Info Package specifications MUST NOT weaken any behavior designated Info Package specifications MUST NOT weaken any behavior designated
with "SHOULD" or "MUST" in this specification. However, Info with "SHOULD" or "MUST" in this specification. However, Info
Packages specifications MAY strengthen "SHOULD", "MAY", or Packages specifications MAY strengthen "SHOULD", "MAY", or
"RECOMMENDED" requirements to "MUST" strength if applications "RECOMMENDED" requirements to "MUST" strength if applications
associated with the Info Package require it. associated with the Info Package require it.
Info Package specifications MUST address the issues defined in the Info Package specifications MUST address the issues defined in the
following subsections, or document why an issue is not applicable for following subsections, or document why an issue is not applicable for
the specific Info Package. the specific Info Package.
Section 7.3 describes alternative mechanisms, which should be Section 8.3 describes alternative mechanisms, which should be
considered as part of the process for solving a specific use-case, considered as part of the process for solving a specific use-case,
when there is a need for transporting application information. when there is a need for transporting application information.
10.2. Overall Description 10.2. Overall Description
The Info Package specification MUST contain an overall description of The Info Package specification MUST contain an overall description of
the Info Package: what type of information are carried in INFO the Info Package: what type of information are carried in INFO
requests associated with the Info Package, and for what type of requests associated with the Info Package, and for what type of
applications and functionalities UAs can use the Info Package. applications and functionalities UAs can use the Info Package.
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information. information.
Annex A provides more information, and describes alternative Annex A provides more information, and describes alternative
mechanisms which one should consider for solving a specific use-case. mechanisms which one should consider for solving a specific use-case.
10.4. Info Package Name 10.4. Info Package Name
The Info Package specification MUST define an Info Package name, The Info Package specification MUST define an Info Package name,
which UAs use as a header field value (e.g. "infoX") to identify the which UAs use as a header field value (e.g. "infoX") to identify the
Info Package in the Recv-Info and Info-Package header fields. The Info Package in the Recv-Info and Info-Package header fields. The
header field value MUST conform to the ABNF defined in Section 8.2. header field value MUST conform to the ABNF defined in Section 9.2.
The Info Package mechanism does not support package versioning. The Info Package mechanism does not support package versioning.
Specific Info Package message body payloads can contain version Specific Info Package message body payloads can contain version
information, which is handled by the applications associated with the information, which is handled by the applications associated with the
Info Package. However, such feature is outside the scope of the Info Package. However, such feature is outside the scope of the
generic Info Package mechanism. generic Info Package mechanism.
NOTE: Even if an Info Package name contains version numbering (e.g. NOTE: Even if an Info Package name contains version numbering (e.g.
foo_v2), the Info Package mechanism does not distinguish a version foo_v2), the Info Package mechanism does not distinguish a version
number from the rest of the Info Package name. number from the rest of the Info Package name.
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the name with parameters defined for other Info Packages, but the the name with parameters defined for other Info Packages, but the
parameter semantics are specific to the Info Package for which they parameter semantics are specific to the Info Package for which they
are defined. However, when choosing the name of a parameter it is are defined. However, when choosing the name of a parameter it is
RECOMMENDED to not use the same name as an existing parameter for RECOMMENDED to not use the same name as an existing parameter for
another Info Package, if the semantics of the parameters are another Info Package, if the semantics of the parameters are
different. different.
10.6. SIP Option Tags 10.6. SIP Option Tags
The Info Package specification MAY define SIP option tags, which can The Info Package specification MAY define SIP option tags, which can
be used as described in [RFC3261]. be used as described in RFC 3261.
The registration requirements for option tags are defined in The registration requirements for option tags are defined in RFC 5727
[RFC5727]. [RFC5727].
10.7. INFO Message Body Parts 10.7. INFO Message Body Parts
The Info Package specification MUST define which message body part The Info Package specification MUST define which message body part
MIME types are associated with the Info Package. The specification MIME types are associated with the Info Package. The specification
MUST either define those body parts, which include the syntax, MUST either define those body parts, which include the syntax,
semantics and MIME type of the each body part, or refer to other semantics and MIME type of the each body part, or refer to other
documents which define the body parts. documents which define the body parts.
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Package, or whether the UA has to wait for the response for a Package, or whether the UA has to wait for the response for a
previous INFO request associated with the same Info Package. previous INFO request associated with the same Info Package.
There can also be restrictions related to whether UAs need to support There can also be restrictions related to whether UAs need to support
and use other SIP extensions and capabilities when they use the Info and use other SIP extensions and capabilities when they use the Info
Package, and if there are restrictions related to how UAs can use the Package, and if there are restrictions related to how UAs can use the
Info-Package together with other Info Packages. Info-Package together with other Info Packages.
As the SIP stack might not be aware of Info Package specific As the SIP stack might not be aware of Info Package specific
restrictions, it cannot be assumed that overlapping requests would be restrictions, it cannot be assumed that overlapping requests would be
rejected. As defined in Section 3.2.2, UAs will normally send a 200 rejected. As defined in Section 4.2.2, UAs will normally send a 200
(OK) response to an INFO request. The application logic associated (OK) response to an INFO request. The application logic associated
with the Info Package needs to handle situations where UAs do not with the Info Package needs to handle situations where UAs do not
follow restrictions associated with the Info Package. follow restrictions associated with the Info Package.
10.9. Rate of INFO Requests 10.9. Rate of INFO Requests
If there is a maximum or minimum rate at which UAs can send INFO If there is a maximum or minimum rate at which UAs can send INFO
requests associated with the Info Package within a dialog, the Info requests associated with the Info Package within a dialog, the Info
Package specification MUST document the rate values. Package specification MUST document the rate values.
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The policy for review of Info Packages is "Specification Required", The policy for review of Info Packages is "Specification Required",
as defined in [RFC5226]. This policy was selected because Info as defined in [RFC5226]. This policy was selected because Info
Packages re-use an existing mechanism for transport of arbitrary Packages re-use an existing mechanism for transport of arbitrary
session-associated data within SIP, and therefore new Info Packages session-associated data within SIP, and therefore new Info Packages
do not require the more extensive review required by specifications do not require the more extensive review required by specifications
that make fundamental protocol changes. However, the reviewer is that make fundamental protocol changes. However, the reviewer is
expected to verify that each Info Package registration is in fact expected to verify that each Info Package registration is in fact
consistent with this definition. Changes to the SIP protocol and consistent with this definition. Changes to the SIP protocol and
state machine are outside of the allowable scope for an Info Package state machine are outside of the allowable scope for an Info Package
and are governed by other procedures including [RFC5727] and its and are governed by other procedures including RFC 5727 and its
successors, if any. successors, if any.
The following data elements populate the Info Package Registry. The following data elements populate the Info Package Registry.
o Info Package Name: The Info Package Name is a case-sensitive o Info Package Name: The Info Package Name is a case-sensitive
token. In addition, IANA shall not register multiple Info Package token. In addition, IANA shall not register multiple Info Package
names that have identical case-insensitive values. names that have identical case-insensitive values.
o Reference: A reference to a specification which describes the Info o Reference: A reference to a specification which describes the Info
Package. Package.
The initial population of this table shall be: The initial population of this table shall be:
Name Reference Name Reference
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Content-length: 59 Content-length: 59
I am a foo-x message type, and I belong to Info Package foo I am a foo-x message type, and I belong to Info Package foo
--theboundary-- --theboundary--
13. Security Considerations 13. Security Considerations
By eliminating multiple usages of INFO messages without adequate By eliminating multiple usages of INFO messages without adequate
community review and by eliminating the possibility for rogue SIP UAs community review and by eliminating the possibility for rogue SIP UAs
from confusing another UA by purposely sending unrelated INFO from confusing another UA by purposely sending unrelated INFO
requests, as described in Section 9.2, we expect this document's requests, we expect this document's clarification of the use of INFO
clarification of the use of INFO to improve the security of the to improve the security of the Internet. Whilst rogue UAs can still
Internet. Whilst rogue UAs can still send unrelated INFO requests, send unrelated INFO requests, this mechanism provides mechanisms for
this mechanism provides mechanisms for which the UAS and other which the UAS and other security devices can associate INFO requests
security devices can associate INFO requests with Info Packages that with Info Packages that have been negotiated for a session.
have been negotiated for a session.
If the content of the Info Package payload is private, UAs will need If the content of the Info Package payload is private, UAs will need
to use end-to-end encryption, such as S/MIME, to prevent access to 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 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 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. user agents (B2BUA's), which the user may not trust.
The INFO request transports application level information. One The INFO request transports application level information. One
implication of this is INFO messages may require a higher level of implication of this is INFO messages may require a higher level of
protection than the underlying SIP dialog signaling. In particular, protection than the underlying SIP dialog signaling. In particular,
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Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980. August 1980.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, with Session Description Protocol (SDP)", RFC 3264,
June 2002. June 2002.
[RFC3398] Camarillo, G., Roach, A., Peterson, J., and L. Ong,
"Integrated Services Digital Network (ISDN) User Part
(ISUP) to Session Initiation Protocol (SIP) Mapping",
RFC 3398, December 2002.
[RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
"Indicating User Agent Capabilities in the Session "Indicating User Agent Capabilities in the Session
Initiation Protocol (SIP)", RFC 3840, August 2004. Initiation Protocol (SIP)", RFC 3840, August 2004.
[RFC3372] Vemuri, A. and J. Peterson, "Session Initiation Protocol [RFC3372] Vemuri, A. and J. Peterson, "Session Initiation Protocol
for Telephones (SIP-T): Context and Architectures", for Telephones (SIP-T): Context and Architectures",
BCP 63, RFC 3372, September 2002. BCP 63, RFC 3372, September 2002.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific [RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002. Event Notification", RFC 3265, June 2002.
[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., [RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
and D. Gurle, "Session Initiation Protocol (SIP) Extension and D. Gurle, "Session Initiation Protocol (SIP) Extension
for Instant Messaging", RFC 3428, December 2002. for Instant Messaging", RFC 3428, December 2002.
[RFC4240] Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network [RFC4240] Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network
Media Services with SIP", RFC 4240, December 2005. Media Services with SIP", RFC 4240, December 2005.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", [RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007. RFC 4960, September 2007.
skipping to change at page 33, line 20 skipping to change at page 34, line 21
November 2008. November 2008.
[RFC5707] Saleem, A., Xin, Y., and G. Sharratt, "Media Server Markup [RFC5707] Saleem, A., Xin, Y., and G. Sharratt, "Media Server Markup
Language (MSML)", RFC 5707, February 2010. Language (MSML)", RFC 5707, February 2010.
[RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet [RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
Mail Extensions (S/MIME) Version 3.2 Message Mail Extensions (S/MIME) Version 3.2 Message
Specification", RFC 5751, January 2010. Specification", RFC 5751, January 2010.
[W3C.REC-voicexml21-20070619] [W3C.REC-voicexml21-20070619]
Porter, B., Oshry, M., Bodell, M., Rehor, K., McGlashan, Rehor, K., Bodell, M., Burke, D., Baggia, P., Auburn, R.,
S., Burke, D., Auburn, R., Candell, E., Burnett, D., Burnett, D., Candell, E., Carter, J., McGlashan, S., Lee,
Carter, J., Baggia, P., and A. Lee, "Voice Extensible A., Porter, B., and M. Oshry, "Voice Extensible Markup
Markup Language (VoiceXML) 2.1", World Wide Web Consortium Language (VoiceXML) 2.1", World Wide Web Consortium
Recommendation REC-voicexml21-20070619, June 2007, Recommendation REC-voicexml21-20070619, June 2007,
<http://www.w3.org/TR/2007/REC-voicexml21-20070619>. <http://www.w3.org/TR/2007/REC-voicexml21-20070619>.
[I-D.ietf-speechsc-mrcpv2] [I-D.ietf-speechsc-mrcpv2]
Shanmugham, S. and D. Burnett, "Media Resource Control Burnett, D. and S. Shanmugham, "Media Resource Control
Protocol Version 2 (MRCPv2)", Protocol Version 2 (MRCPv2)",
draft-ietf-speechsc-mrcpv2-20 (work in progress), draft-ietf-speechsc-mrcpv2-21 (work in progress),
August 2009. July 2010.
[Ecma-355] [Ecma-355]
"Standard ECMA-355 Corporate Telecommunication Networks - "Standard ECMA-355 Corporate Telecommunication Networks -
Tunnelling of QSIG over SIP", ECMA http:// Tunnelling of QSIG over SIP", ECMA http://
www.ecma-international.org/publications/standards/ www.ecma-international.org/publications/standards/
Ecma-355.htm, June 2008. Ecma-355.htm, June 2008.
Appendix A. Legacy INFO Usage Appendix A. Acknowledgements
A.1. General
This section provides examples of existing legacy INFO usages. The
section is not meant to be a comprehensive catalog of legacy INFO
usages, but it should give the reader a flavor for current legacy
INFO usages.
A.2. ISUP
[RFC3372] specifies the encapsulation of ISDN User Part (ISUP) in SIP
message bodies. ITU-T and 3GPP have specified similar procedures.
A.3. QSIG
[Ecma-355] specifies the encapsulation of QSIG in SIP message bodies.
A.4. MSCML
[RFC5022] specifies how INFO is used as a transport mechanism by the
Media Server Control Markup Language (MSCML) protocol. MSCML uses an
option-tag in the Require header field to ensure that the receiver
understands the INFO content.
A.5. MSML
[RFC5707] specifies how INFO us used as a transport mechanism by the
Media Server Markup Language (MSML) protocol.
A.6. Video Fast Update
Companies have been using INFO messages in order to request fast
video update. Currently a standardized mechanism, based on RTCP, has
been specified in [RFC5168]
A.7. DTMF
Companies have been using INFO messages in order to transport DTMF
tones. All mechanisms are proprietary, and have not been
standardized.
Appendix B. Acknowledgements
The work on this document was influenced by the "INFO Considered The work on this document was influenced by the "INFO Considered
Harmful" draft (26 December 2002) written by Jonathan Rosenberg, and Harmful" draft (26 December 2002) written by Jonathan Rosenberg, and
by the "Packaging and Negotiation of INFO Methods for the Session by the "Packaging and Negotiation of INFO Methods for the Session
Initiation Protocol" draft (15 January 2003) written by Dean Willis. Initiation Protocol" draft (15 January 2003) written by Dean Willis.
The following individuals have been involved in the work, and have The following individuals have been involved in the work, and have
provided input and feedback on this document: provided input and feedback on this document:
Adam Roach, Anders Kristensen, Andrew Allen, Arun Arunachalam, Ben Adam Roach, Anders Kristensen, Andrew Allen, Arun Arunachalam, Ben
Campbell, Bob Penfield, Bram Verburg, Brian Stucker, Chris Campbell, Bob Penfield, Bram Verburg, Brian Stucker, Chris
Boulton, Christian Stredicke, Cullen Jennings, Dale Worley, Dean Boulton, Christian Stredicke, Cullen Jennings, Dale Worley, Dean
Willis, Eric Rescorla, Frank Miller, Gonzalo Camarillo, Gordon Willis, Eric Rescorla, Frank Miller, Gonzalo Camarillo, Gordon
Beith, Henry Sinnreich, Inaki Baz Castillo, James Jackson, James Beith, Henry Sinnreich, Inaki Baz Castillo, James Jackson, James
Rafferty, Jeroen van Bemmel, Joel Halpern, John Elwell, Johnathan Rafferty, Jeroen van Bemmel, Joel Halpern, John Elwell, Johnathan
Rosenberg, Juha Heinanen, Gordon Beith, Keith Drage, Kevin Attard Rosenberg, Juha Heinanen, Gordon Beith, Keith Drage, Kevin Attard
Compagno, Manpreet Singh, Martin Dolly, Mary Barnes, Michael Compagno, Manpreet Singh, Martin Dolly, Mary Barnes, Michael
Procter, Paul Kyzivat, Peili Xu, Peter Blatherwick, Raj Jain, Procter, Paul Kyzivat, Peili Xu, Peter Blatherwick, Raj Jain,
Rayees Khan, Robert Sparks, Roland Jesske, Roni Evan Salvatore Rayees Khan, Robert Sparks, Roland Jesske, Roni Evan Salvatore
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Keith Drage provided comments and helped immensely with Figure 1. Keith Drage provided comments and helped immensely with Figure 1.
Arun Arunachalam, Brett Tate, John Elwell, Keith Drage and Robert Arun Arunachalam, Brett Tate, John Elwell, Keith Drage and Robert
Sparks provided valuable feedback during the WGLC process, in order Sparks provided valuable feedback during the WGLC process, in order
to prepare this document for publication. to prepare this document for publication.
Adam Roach, Dean Willis, John Elwell and Paul Kyzivat provided Adam Roach, Dean Willis, John Elwell and Paul Kyzivat provided
valuable input in order to sort out the message body part usage for valuable input in order to sort out the message body part usage for
Info Packages. Info Packages.
Appendix C. Change Log Appendix B. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing] [RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-sipcore-info-events-09
o New Motivation section added
o Old section 9 and Annex A removed
Changes from draft-ietf-sipcore-info-events-08 Changes from draft-ietf-sipcore-info-events-08
o Further changes based on IESG comments o Further changes based on IESG comments
o Editorial changes o Editorial changes
o Section 7.3 removed o Section 7.3 removed
o New section 7.4.1.2. added, containing text from old section 7.3 o New section 7.4.1.2. added, containing text from old section 7.3
Changes from draft-ietf-sipcore-info-events-07 Changes from draft-ietf-sipcore-info-events-07
o Further changes based on WGLC comments o Further changes based on WGLC comments
o Editorial changes o Editorial changes
o IANA registry procedures clarified o IANA registry procedures clarified
 End of changes. 90 change blocks. 
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