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Versions: (draft-ietf-sip-info-events) 00 01
02 03 04 05 06 07 08 09 10 RFC 6086
SIPCORE E. Burger
Internet-Draft NeuStar, Inc.
Obsoletes: RFC 2976 H. Kaplan
(if approved) Acme Packet
Expires: April 26, 2010 C. Holmberg
Ericsson
October 23, 2009
Session Initiation Protocol (SIP) INFO Method and Package Framework
draft-ietf-sipcore-info-events-02
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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Abstract
This document defines a new method, INFO, for the Session Initiation
Protocol (SIP) [RFC3261], and an Info Package mechanism. The
document obsoletes [RFC2976]. For backward compatibility the
document also specifies a "legacy" mode of usage of the INFO method
that is compatible with the usage previously defined in [RFC2976],
referred to as "legacy INFO Usage" in this document.
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 . . . . . . . . . . . . . . . . . . . . . 6
3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. User Agent Behavior . . . . . . . . . . . . . . . . . . . 6
3.3. Package Versioning . . . . . . . . . . . . . . . . . . . 7
3.4. REGISTER Processing . . . . . . . . . . . . . . . . . . . 7
3.5. OPTIONS Processing . . . . . . . . . . . . . . . . . . . 8
4. The INFO Method . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. INFO Request . . . . . . . . . . . . . . . . . . . . . . 8
4.3. INFO Request Message Body . . . . . . . . . . . . . . . . 9
4.4. INFO Response . . . . . . . . . . . . . . . . . . . . . . 10
4.5. INFO Response Message Body . . . . . . . . . . . . . . . 11
4.6. Order of Delivery . . . . . . . . . . . . . . . . . . . . 11
5. Formal INFO Method Definition . . . . . . . . . . . . . . . . 11
5.1. INFO Method . . . . . . . . . . . . . . . . . . . . . . . 11
6. INFO Header Fields . . . . . . . . . . . . . . . . . . . . . . 13
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.2. Info-Package header field . . . . . . . . . . . . . . . . 13
6.3. Recv-Info header field . . . . . . . . . . . . . . . . . 14
7. Info Package Considerations . . . . . . . . . . . . . . . . . 14
7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.2. Appropriateness of Info Package Usage . . . . . . . . . . 14
7.3. Dialog Fate Sharing . . . . . . . . . . . . . . . . . . . 14
7.4. INFO Request Rate and Volume . . . . . . . . . . . . . . 14
7.5. Alternative Mechanisms . . . . . . . . . . . . . . . . . 15
7.5.1. Alternative SIP signaling plane mechanisms . . . . . . 15
7.5.2. Media Plane Mechanisms . . . . . . . . . . . . . . . . 16
7.5.3. Non-SIP related mechanisms . . . . . . . . . . . . . . 17
8. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9. Legacy INFO Usage . . . . . . . . . . . . . . . . . . . . . . 17
9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.2. Problems . . . . . . . . . . . . . . . . . . . . . . . . 18
9.3. Co-existence with Info Package based INFO usage . . . . . 18
10. Info Package Requirements . . . . . . . . . . . . . . . . . . 19
10.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 19
10.3. Info Package Name . . . . . . . . . . . . . . . . . . . . 19
10.4. Info Package Parameters . . . . . . . . . . . . . . . . . 20
10.5. SIP Option Tags . . . . . . . . . . . . . . . . . . . . . 20
10.6. INFO Message Bodies . . . . . . . . . . . . . . . . . . . 20
10.7. Info Package Usage Restrictions . . . . . . . . . . . . . 20
10.8. Rate of INFO Requests . . . . . . . . . . . . . . . . . . 21
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10.9. IANA Registrations . . . . . . . . . . . . . . . . . . . 21
10.10. Info Package Security Considerations . . . . . . . . . . 21
10.11. Application Procedures . . . . . . . . . . . . . . . . . 22
10.12. Examples . . . . . . . . . . . . . . . . . . . . . . . . 22
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
11.1. Update to Registration of SIP INFO Method . . . . . . . . 22
11.2. Registration of the Info-Package Header Field . . . . . . 22
11.3. Registration of the Recv-Info Header Field . . . . . . . 23
11.4. Creation of the Info Packages Registry . . . . . . . . . 23
11.5. Registration of the Info-Package Content-Disposition . . 24
11.6. SIP Response Code 469 Registration . . . . . . . . . . . 24
12. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
12.1. Indication of which Info Packages UAs are willing to
receive INFO requests within an invite dialog usage . . . 24
12.2. INFO request with information associated with a
simple Info Package . . . . . . . . . . . . . . . . . . . 25
12.3. Multipart INFO Example . . . . . . . . . . . . . . . . . 25
13. Security Considerations . . . . . . . . . . . . . . . . . . . 26
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
14.1. Normative References . . . . . . . . . . . . . . . . . . 27
14.2. Informative References . . . . . . . . . . . . . . . . . 28
Appendix A. Legacy INFO Usages . . . . . . . . . . . . . . . . . 30
A.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 30
A.2. ISUP . . . . . . . . . . . . . . . . . . . . . . . . . . 30
A.3. QSIG . . . . . . . . . . . . . . . . . . . . . . . . . . 30
A.4. MSCML . . . . . . . . . . . . . . . . . . . . . . . . . . 30
A.5. MSML . . . . . . . . . . . . . . . . . . . . . . . . . . 31
A.6. Video Fast Update . . . . . . . . . . . . . . . . . . . . 31
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 31
Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
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1. Introduction
This document defines a new method, INFO, for the Session Initiation
Protocol (SIP) [RFC3261].
The purpose of the INFO message is to carry application level
information between endpoints, using the SIP dialog signaling path.
Note that the INFO method is not used to update characteristics of a
SIP dialog or session, but to allow the applications which use the
SIP session to exchange information (which may update the state of
those applications).
This document also defines an Info Package mechanism. An Info
Package specification defines the content and semantics of the
information carried in an INFO message associated with the Info
Package. The Info Package mechanism also provides a way for UAs to
for which Info Packages they are willing to receive INFO requests.
The document defines how the INFO method is used, new SIP header
fields for the INFO method, and how to transport payload information
associated with an Info Package using INFO requests.
Use of the INFO method does not constitute a separate dialog usage.
INFO messages are always part of, and share the fate of, an invite
dialog usage [RFC5057]. INFO messages cannot be sent as part of
other dialog usages.
A UA uses the Recv-Info header field, on a per-dialog basis, to
indicate for which Info Packages it is willing to receive INFO
requests. A UA can indicate an initial set of Info Packages during
dialog establishment and can indicate a new set during the lifetime
of the invite dialog usage.
NOTE: A UA can use the Recv-Info header field with a 'nil' value to
indicate that it is not willing to receive INFO requests for any
Info-Package, but to inform other UAs that it 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.
One particular INFO request can only be associated with a single Info
Package.
This document obsoletes [RFC2976]. However, for backward
compatibility it specifies a "legacy" mode of usage of the INFO
method that is compatible with the usage previously defined in
[RFC2976], referred to as "legacy INFO Usage" in this document.
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2. Applicability
This document defines a new method, INFO, for the Session Initiation
Protocol (SIP) [RFC3261], and an Info Package mechanism. The
document obsoletes [RFC2976]. For backward compatibility the
document also specifies a "legacy" mode of usage of the INFO method
that is compatible with the usage previously defined in [RFC2976],
referred to as "legacy INFO Usage" in this document.
3. Info Package Support
3.1. General
This section describes how SIP UAs indicate for which Info Packages
they are willing to receive INFO requests.
3.2. User Agent Behavior
A UA which supports the Info Package mechanism MUST indicate, using
the Revc-Info header field, the set of Info Packages for which it is
willing to receive INFO request. 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 dialog
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.
If a UA is not willing to INFO requests for any Info Packages, during
dialog establishment or later during the invite dialog usage, the UA
MUST indicate this by including a Recv-Info header field with a 'nil'
value. This informs other UAs that the UA still supports the Info
Package mechanism.
Example: If a UA has previously indicated Info Packages 'foo' and
'bar', and the UA during the lifetime of the invite dialog usage
wants to indicate that it does not want to receive INFO requests for
any Info Packages anymore, the UA sends a target refresh request with
a Recv-Info header field with a header value of 'nil'.
Once a UA has indicated that it is willing to receive INFO requests
for a specific Info Package, and a dialog has been established, the
UA MUST be prepared to receive INFO request associated with that Info
Package.
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A UA MUST NOT send an INFO request associated with an Info Package
until it has received an indication that the remote UA is willing to
receive INFO requests for that Info Package, and a dialog has been
established with the remote UA.
If a UA indicates multiple Info Packages, which provide similar
functionality, it is not possible to indicate a priority order of the
Info Packages, or that that the UA wishes to only receive INFO
request for one of the Info Packages. It is up to the application
logic associated with the Info Packages, and specific Info Package
descriptions to describe application behavior in such cases.
For backward compatibility purpose, even if a UA indicates support of
the Info Package mechanism, it is still allowed to enable legacy INFO
usages Section 9.
This document does not define a SIP option tag [RFC3261] for the Info
Package mechanism. However, an Info Package specification can define
an option-tag associated with the specific Info Package, as described
in Section 10.5.
For backward compatibility, if a UA indicates support of the INFO
method using the Allow header field [RFC3261], it does not implicitly
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
Package mechanism. Likewise, even if a UA uses the Recv-Info header
field to indicate that it supports the Info Package mechanism, in
addition the UA MUST still also explicitly indicate support of the
INFO method using the Allow header field.
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 with the Info Package, but
that is outside the scope of the Info Package mechanism.
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
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
a specific Info Package unless the specific Info Package
specification describes how the header field value shall be
interpreted and used by the registrar, e.g. in order to determine
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request targets.
NOTE: Rather than using the Recv-Info header field in order to
determine request targets, it is recommended to use more appropriate
mechanisms, e.g. based on [RFC3840].
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 to receive.
NOTE: As for any other capability and extension, for a specific
dialog UAs need to indicate which Info Packages they are willing to
receive within that dialog.
4. The INFO Method
4.1. General
This section describes the UA handling of INFO requests and
responses, and message bodies carried in INFO messages.
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.
4.2. INFO Request
When a UA sends an INFO request associated with an Info Package, it
MUST include an Info-Package header field that indicates which Info
Package is associated with the request. A specific INFO request can
be used only for a single Info Package. For a specific dialog, a UA
MUST NOT send INFO requests associated with Info Packages that the
remote UA has not indicated that it is willing to receive.
A UA can send an INFO requests associated with a legacy INFO usage
Section 9. 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 UA cannot use the Recv-Info header field to
indicate whether it is willing to receive INFO requests associated
with that legacy INFO usage.
The INFO method MUST NOT be used outside an invite dialog usage. The
INFO method has no lifetime beyond its transaction or usage of its
own. UAs indicate, per-dialog basis, for which Info Packages they
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are willing to receive INFO requests. The set of Info Packages
cannot automatically be used within other dialogs.
Due to the possibility of forking, a UAC which, during the early
dialog phase indicates that it is willing to receive INFO requests
for one or more Info Packages MUST be prepared to receive INFO
requests associated with those Info Packages from multiple remote
UAs. Note that each remote UA can indicate a different set of Info
Packages for which they are willing to receive INFO request.
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 within early and confirmed dialogs.
The INFO request MUST NOT contain a Recv-Info header field. The UA
can only indicate a set of Info Packages for which it is willing to
receive INFO requests by using the SIP methods (and their responses)
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 is carried as payload in the message body of the INFO
request, using one or more body parts.
Info Package specifications MUST describe the application level
information associated with the Info Package. Each body part MUST
have a MIME type value, and the syntax and content of the body part,
defined.
Each body part, when associated with an Info Package, MUST have a
Content-Disposition header field with an 'Info-Package' value
assigned, in order to be able distinguish body parts associated with
the Info Package from other body parts.
NOTE: Some SIP functions that are orthogonal to INFO may insert body
parts unrelated to the Info Package.
Body parts associated with specific MIME types may sometimes have
specific Content-Disposition header field values defined for them.
For example, for body parts with a 'text/plain' MIME a Content-
Disposition header field with a 'render' value is often assigned.
However, when a body part in the INFO message is associated with an
Info Package, it MUST always have a Content-Disposition header field
with an 'Info-Package' value assigned. The Info Package
specification defines how applications process the body part
contents.
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If a SIP message body contains multiple body parts, multipart body
parts [RFC5621] are used to separate them. If all body parts within
a multipart body part are associated with the Info Package, the
multipart body part SHALL have a Content-Disposition header field
with an 'Info-Package' value assigned to it. However, each body part
within the multipart body part MUST still have a Content-Disposition
header field with an 'Info-Package' value assigned to them, in order
to avoid that the parser assigns a default Content-Disposition header
value to the body part.
NOTE: According to [RFC5621], body parts within a multipart are not
implicitly assigned the Content-Disposition header field value of the
multipart body part which they belong to.
This document does not define Info Package specific rules on how body
parts associated with Info Packages are to be inserted into multipart
body parts, and what type of multiparts are used. If an Info Package
requires special rules regarding the usage of multipart body parts,
the specification for that Info Package MUST specify such rules.
UAs MUST conform to [RFC5621] to support multipart body parts.
If a UA indicates that it is willing to receive a specific Info
Package, the UA naturally also supports any associated message body
part MIME type associated with the Info Package. However, in
addition the UA MUST still indicate support of those MIME types in
the Accept header field, according to the procedures in [RFC3261].
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.
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 for legacy usage, for which no Info-
Package is associated (the INFO request does not contain an Info-
Package header field), the UA MUST send a 200 OK response.
The UAS MAY send other responses, such as Request Failure (4xx),
Server Failure (5xx) and Global Failure (6xx) as appropriate for the
request.
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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 Section 11.6. In the terminology of
Multiple Dialog Usages [RFC5057], this represents a Transaction Only
failure.
If a UA receives an INFO request that 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 that 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.
4.5. INFO Response Message Body
The Info Package mechanism allows a SIP stack to generate a response
to an INFO request without application interaction. As a result,
Info Packages cannot require a message body in INFO responses,
require different response codes, or otherwise require the response
to the INFO request to contain application information. If the
application needs to send information in the other direction, it can
send a new INFO request which contains the information.
4.6. Order of Delivery
The Info Package mechanism relies on the CSeq header field to detect
if an INFO request is received out of order.
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
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------ ----- ----
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 -
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
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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
6. INFO Header Fields
6.1. General
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 - - -
Recv-Info 2xx 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].
Table 2: INFO-related Header Fields
6.2. Info-Package header field
This document adds Info-Package to the definition of the element
"message-header" in the SIP message grammar [RFC3261]. 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
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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].
6.3. Recv-Info header field
This document adds Recv-Info to the definition of the element
"message-header" in the SIP message grammar [RFC3261]. Section 3
describes the Recv-Info header field usage.
7. Info Package Considerations
7.1. 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.
7.2. 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 dialog, 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.
7.3. 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 usage is terminated, while in other cases is is desirable to
maintain the dialog usage.
7.4. INFO Request Rate and Volume
There is no default throttling mechanism for INFO requests. Apart
from the SIP session establishment, the number of SIP messages
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exchanged during the lifetime 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 lifetime of the invite dialog usage.
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.
7.5. Alternative Mechanisms
7.5.1. Alternative SIP signaling plane mechanisms
7.5.1.1. General
This subsection describes some alternative mechanisms for
transporting application information on the SIP signaling plane,
using SIP messages.
7.5.1.2. SUBSCRIBE/NOTIFY
An alternative for application level interaction is to use
subscription-based events [RFC3265], which uses the SIP SUBSCRIBE and
NOTIFY methods. Using that mechanism, 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.
Event Packages [RFC3265] perform the role of disambiguating the
context of a message for subscription-based events. The Info Package
mechanism provides similar functionality for application information
exchange using invite dialog usages [RFC5057].
While an INFO request is always part of, and shares the fate of, an
existing invite dialog usage, a SUBSCRIBE request creates a new
session and a subscription dialog usage [RFC5057] which is separate,
and does not share the fate any other sessions.
The subscription-based mechanism can be used by SIP entities to
receive state information about SIP dialogs and sessions, without
requiring the entities to be part of the route set of those dialogs
and sessions.
As SUBSCRIBE/NOTIFY messages traverse through stateful SIP proxies
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and B2BUAs, the resource impact caused by the subscription sessions
needs to be considered. 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
dialog route set, but do not have any interest in the application
information transported between the end users.
7.5.1.3. MESSAGE
The MESSAGE method [RFC3428] defines one-time instant message
exchange, typically for sending MIME contents for rendering to the
ser.
7.5.2. Media Plane Mechanisms
7.5.2.1. General
In SIP, media plane channels associated with SIP dialogs 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.
7.5.2.2. 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.
7.5.2.3. MRSP
MSRP [RFC4975] defines session-based instant messaging as well as
bulk file transfer and other such large-volume uses.
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7.5.3. 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.
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.
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
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such usages. However, any new usage of INFO SHALL use the Info
Package mechanism defined in this specification.
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].
9.3. Co-existence with Info Package based INFO usage
As described in Section 4, an INFO request associated with an Info
Package always contains an Info-Package header field. A legacy INFO
request MUST NOT contain an Info-Package header field.
UAs are allowed to enable both legacy INFO usages and Info Package
usages as part of the same invite dialog usage.
See Appendix A for examples of existing legacy INFO usages.
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10. Info Package Requirements
10.1. 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, or document why an issue is not applicable for
the specific Info Package.
10.2. 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 transported application
information (which would not be the case if the information was
transported on a media path), or that it is not seen feasible to
establish separate dialogs (subscription) in order to transport the
information.
Annex A provides more information, and describes alternative
mechanisms which one should consider for solving a specific use-case.
10.3. Info Package Name
The Info Package specification MUST define a for Info Package name
(e.g. "Info Package for X").
The specification MUST also define the header field value (e.g.
"infoX") 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.
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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.
10.4. 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. They MUST
NOT be used for other Info Packages.
NOTE: Info Package parameters defined for specific Info Packages may
share the name with parameters defined for other Info Packages, but
the parameter semantics are specific to the Info Package for which
they are defined.
10.5. 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
[I-D.peterson-rai-rfc3427bis].
10.6. INFO Message Bodies
The Info Package specification MUST define what type of message body
parts are associated with the Info Package, and MUST refer to
specifications where the syntax, semantics and MIME type of the
message body parts are described.
If multiple body parts are used with an Info Package, the Info
Package specification MUST define whether there are special rules on
how the body parts are to be inserted in multipart body parts, and
what types of multipart to use.
10.7. 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
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Package, or whether the UA has to wait for the response for a
previous INFO request associated with the same Info Package.
The specification MUST define whether there are 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.
As the SIP stack may not be aware of Info Package specific
restrictions, it cannot be assumed that overlapping requests would be
rejected. As defined in Section 4.4, in most cases a 200 OK response
will be sent for the INFO request. The application logic associated
with the Info Package needs to handle situations which can occur due
to overlapping requests.
10.8. Rate of INFO Requests
The Info Package specification MUST specify 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.
10.9. 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.
10.10. Info Package 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, this fact SHALL be stated in
the Info Package specification.
NOTE: In some cases, it may not be sufficient to mandate TLS in order
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to secure the Info Package payload, since intermediaries will have
access to the payload, and beyond 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
to have the security at the application level. One way of achieving
this is to use end-to-end security techniques such as S/MIME
[RFC3851].
10.11. 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.
10.12. 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 do not
replace normative text
11. IANA Considerations
11.1. 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]
11.2. 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.
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Header Name: Info-Package
Compact Form: (none)
Reference: [RFCXXXX]
11.3. 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]
11.4. 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.
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:
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Name MIME Type Standards Status Reference
nil Standards Track [RFCXXXX]
11.5. Registration of the Info-Package Content-Disposition
Please add the following new header field value to the Content-
Disposition registry.
Name: info-package
Description: the body contains information associated with an Info Package
Reference: RFCXXXX
11.6. SIP Response Code 469 Registration
Please register the following new response code in the Session
Initiation Protocol Parameters - Response Codes registry.
Response Code: 469
Default Reason Phrase: Bad INFO Package
Reference: RFCXXXX
12. Examples
12.1. Indication of which Info Packages UAs are willing to receive INFO
requests within an invite dialog usage
The UAC sends an INVITE request, where the UAC indicates that it is
willing to receive Info Packages P and R.
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.
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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: ...
...
The UAC sends ACK.
ACK sip:ngw1@a.example.com SIP/2.0
Via: SIP/2.0/TCP pc33.example.com;branch=z9hG4bK754
Max-Forwards: 70
To: Bob <sip:bob@example.com>;tag=a6c85cf
From: Alice <sip:alice@example.com>;tag=1928301774
Call-ID: a84b4c76e66710@pc33.example.com
CSeq: 314159 ACK
Content-Length: 0
12.2. INFO request with information associated with a simple Info
Package
Here Alice sends Bob a simple Info Package payload.
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
12.3. Multipart INFO Example
Other SIP extensions can sometimes add payload body parts into an
INFO request, independent of the Info Package. In this case, the
Info Package payload gets put into a Multipart MIME body, with a
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Content-Disposition header field that indicates which body part is
associated with the Info Package.
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--
13. Security Considerations
By eliminating multiple usages of INFO messages without adequate
community review and by eliminating the possibility for rogue SIP UAs
from confusing another UA 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 mechanism 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, UAs 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 request transports application level information. One
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implication of this is INFO messages may require a higher level of
protection than the underlying SIP dialog signaling. In particular,
if one does not protect the SIP signaling from 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.
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, 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.
[RFC5621] Camarillo, G., "Message Body Handling in the Session
Initiation Protocol (SIP)", RFC 5621, September 2009.
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14.2. 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.
[RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
"Indicating User Agent Capabilities in the Session
Initiation Protocol (SIP)", RFC 3840, August 2004.
[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.
[I-D.peterson-rai-rfc3427bis]
Peterson, J., Jennings, C., and R. Sparks, "Change Process
for the Session Initiation Protocol (SIP)",
draft-peterson-rai-rfc3427bis-03 (work in progress),
September 2009.
[W3C.REC-voicexml21-20070619]
McGlashan, S., Lee, A., Carter, J., Porter, B., Auburn,
R., Oshry, M., Rehor, K., Bodell, M., Burke, D., Baggia,
P., Candell, E., and D. Burnett, "Voice Extensible Markup
Language (VoiceXML) 2.1", World Wide Web Consortium
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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)",
draft-ietf-speechsc-mrcpv2-20 (work in progress),
August 2009.
[I-D.saleem-msml]
Saleem, A. and G. Sharratt, "Media Server Markup Language
(MSML)", draft-saleem-msml-09 (work in progress),
July 2009.
[Ecma-355]
"Standard ECMA-355 Corporate Telecommunication Networks -
Tunnelling of QSIG over SIP", ECMA http://
www.ecma-international.org/publications/standards/
Ecma-355.htm, June 2008.
Appendix A. Legacy INFO Usages
A.1. General
This section provides examples of existing legacy INFO usages. This
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 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
MSCML protocol. MSCML uses an option-tag in the Require header field
to ensure that the receiver understands the INFO content.
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A.5. MSML
[I-D.saleem-msml] specifies how INFO us used as a transport mechanism
by the 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]
Appendix B. Acknowledgements
The work on this document was influenced by the "INFO Considered
Harmful" draft (26 December 2002) written by Jonathan Rosenberg, and
by the "Packaging and Negotiation of INFO Methods for the Session
Initiation Protocol" draft (15 January 2003) written by Dean Willis.
The following individuals have been involved in the work, and have
provided input and feedback on this document:
Adam Roach, Anders Kristensen, Andrew Allen, Arun Arunachalam, Ben
Campbell, Bob Penfield, Bram Verburg, Brian Stucker, Chris
Boulton, Christian Stredicke, Cullen Jennings, Dale Worley, Dean
Willis, Eric Rescorla, Frank Miller, Gonzalo Camarillo, Gordon
Beith, Henry Sinnreich, Inaki Baz Castillo, James Jackson, James
Rafferty, Jeroen van Bemmel, Joel Halpern, John Elwell, Johnathan
Rosenberg, Juha Heinanen, Gordon Beith, Keith Drage, Kevin Attard
Compagno, Manpreet Singh, Martin Dolly, Mary Barnes, Michael
Procter, Paul Kyzivat, Peili Xu, Peter Blatherwick, Raj Jain,
Rayees Khan, Robert Sparks, Roland Jesske, Roni Evan Salvatore
Loreto, Sam Ganesan, Sanjay Sinha, Spencer Dawkins, Steve
Langstaff, Sumit Garg and Xavier Marjoum.
John Elwell and Francois Audet helped with QSIG references. In
addition, Francois Audet provided text for the revised abstract.
Keith Drage provided comments and helped immensely with Figure 1.
John Elwell and Robert Sparks provided valuable feedback during the
WGLC process, in order to prepare this document for publication.
Appendix C. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-sipcore-info-events-01
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o Further changes based on WGLC comments
o Appending A moved into the main part of the document
o Section name changed from "Modifications to SIP Change Process" to
"Security Considerations"
o "Syntax" section moved further up in the document
o Clarification on usage of Info Package related message body parts,
and the usage of the Content-Disposition header field with those
body parts
o Removed REFER and NOTIFY from the INFO Headers table
o Clarified usage of the Recv-Info header field in the REGISTER and
OPTIONS requests
o Major re-write of the Introduction section
o Text about legacy INFO and subscription-based events moved from
the Introduction to the main part of the document
o Wording about receiving Info-Packages has been replaced with
wording about receiving INFO requests for Info-Packages
o The text about the usage of message body, and body parts,
associated with Info Packages, has been clarified
Changes from draft-ietf-sip-info-events-04
o Major re-write of the document, due to problems to implement WGLC
comments into the existing text structure
o Wording allignment
o Clarification or roles
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
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
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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
o Moved definitions of INFO into the body of the text and cleaned up
IANA Considerations section
o Added legacy usages descriptions
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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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