Network Working Group M. Barnes
Internet-Draft Polycom
Obsoletes: 4244 (if approved) F. Audet
Intended status: Standards Track Skype
Expires: October 29, 2011 S. Schubert
NTT
J. van Elburg
Detecon International Gmbh
C. Holmberg
Ericsson
April 27, 2011
An Extension to the Session Initiation Protocol (SIP) for Request
History Information
draft-ietf-sipcore-rfc4244bis-05.txt
Abstract
This document defines a standard mechanism for capturing the history
information associated with a Session Initiation Protocol (SIP)
request. This capability enables many enhanced services by providing
the information as to how and why a SIP request arrives at a specific
application or user. This document defines an optional SIP header
field, History-Info, for capturing the history information in
requests. The document also defines SIP header field parameters for
the History-Info and Contact header fields to tag the method by which
the target of a request is determined. In addition, this document
defines a value for the Privacy header field specific to the History-
Info header field. This document obsoletes RFC 4244.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 29, 2011.
Barnes, et al. Expires October 29, 2011 [Page 1]
Internet-Draft History-Info April 2011
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Barnes, et al. Expires October 29, 2011 [Page 2]
Internet-Draft History-Info April 2011
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 5
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. History-Info Header Field Protocol Structure . . . . . . . . . 8
5.1. History-Info Header Field Example Scenario . . . . . . . . 10
6. User Agent Handling of the History-Info Header Field . . . . . 13
6.1. User Agent Client (UAC) Behavior . . . . . . . . . . . . . 13
6.2. User Agent Server (UAS) Behavior . . . . . . . . . . . . . 13
7. Proxy/Intermediary Handling of History-Info Header Fields . . 13
8. Redirect Server Handling of History-Info Header Fields . . . . 14
9. Handling of History-Info Header Fields in Requests and
Responses . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Receiving a Request . . . . . . . . . . . . . . . . . . . 14
9.2. Sending a Request with History-Info . . . . . . . . . . . 15
9.3. Receiving a Response with History-Info or Request
Timeouts . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.4. Sending History-Info in Responses . . . . . . . . . . . . 16
10. Processing the History-Info Header Field . . . . . . . . . . . 16
10.1. Privacy in the History-Info Header Field . . . . . . . . . 17
10.1.1. Indicating Privacy . . . . . . . . . . . . . . . . . 17
10.1.2. Applying Privacy . . . . . . . . . . . . . . . . . . 18
10.2. Reason in the History-info Header Field . . . . . . . . . 19
10.3. Indexing in the History-Info Header Field . . . . . . . . 19
10.4. Indicating the Mechanism by which the Target was
Determined . . . . . . . . . . . . . . . . . . . . . . . . 21
11. Application Considerations . . . . . . . . . . . . . . . . . . 21
12. Security Considerations . . . . . . . . . . . . . . . . . . . 23
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
13.1. Registration of New SIP History-Info Header Field . . . . 24
13.2. Registration of "history" for SIP Privacy Header Field . . 25
13.3. Registration of Header Field Parameters . . . . . . . . . 25
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
15. Changes from RFC 4244 . . . . . . . . . . . . . . . . . . . . 26
15.1. Backwards compatibility . . . . . . . . . . . . . . . . . 28
16. Changes since last Version . . . . . . . . . . . . . . . . . . 28
17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 34
17.1. Normative References . . . . . . . . . . . . . . . . . . . 34
17.2. Informative References . . . . . . . . . . . . . . . . . . 35
Appendix A. Request History Requirements . . . . . . . . . . . . 35
A.1. Security Requirements . . . . . . . . . . . . . . . . . . 36
A.2. Privacy Requirements . . . . . . . . . . . . . . . . . . . 37
Appendix B. Example call flows . . . . . . . . . . . . . . . . . 38
B.1. Sequentially Forking (History-Info in Response) . . . . . 38
B.2. History-Info with Privacy Header Field . . . . . . . . . . 45
B.3. Privacy for a Specific History-Info Entry . . . . . . . . 47
Barnes, et al. Expires October 29, 2011 [Page 3]
Internet-Draft History-Info April 2011
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 48
Barnes, et al. Expires October 29, 2011 [Page 4]
Internet-Draft History-Info April 2011
1. Introduction
Many services that SIP is anticipated to support require the ability
to determine why and how a SIP request arrived at a specific
application. Examples of such services include (but are not limited
to) sessions initiated to call centers via "click to talk" SIP
Uniform Resource Locators (URLs) on a web page, "call history/
logging" style services within intelligent "call management" software
for SIP User Agents (UAs), and calls to voicemail servers. Although
SIP implicitly provides the retarget capabilities that enable SIP
requests to be routed to chosen applications, there is a need for a
standard mechanism within SIP for communicating the retargeting
history of the requests. This "request history" information allows
the receiving application to determine hints about how and why the
SIP request arrived at the application/user.
This document defines a SIP header field, History-Info, to provide a
standard mechanism for capturing the request history information to
enable a wide variety of services for networks and end-users. SIP
header field parameters are defined for the History-Info and Contact
header fields to tag the method by which the target of a request is
determined. In addition, this document defines a value for the
Privacy header field specific to the History-Info header.
The History-info header field provides a building block for
development of SIP based applications and services. The requirements
for the solution described in this document are included in
Appendix A. Example scenarios using the History-info header field
are included in Appendix B.
2. Conventions and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The term "retarget" is used in this document to refer to the process
of a SIP entity changing a Uniform Resource Identifier (URI) in a
request based on the rules for determining request targets as
described in Section 16.5 of [RFC3261] and of the subsequent
forwarding of that request as described in step 2 in section 16.6 of
[RFC3261]. This includes changing the Request-URI due to a location
service lookup and redirect processing. This also includes internal
(to a proxy/SIP intermediary) changes of the URI prior to forwarding
of the request.
The terms "location service", "forward", "redirect" and "AOR" are
Barnes, et al. Expires October 29, 2011 [Page 5]
Internet-Draft History-Info April 2011
used consistent with the terminology in [RFC3261].
The references to "domain for which the SIP entity/Proxy/Intermediary
is responsible" are consistent with and intended to convey the same
context as the usage of that terminology in [RFC3261]. The
applicability of History-Info to architectures or models outside the
context of [RFC3261] is outside the scope of this specification.
3. Background
SIP implicitly provides retargeting capabilities that enable SIP
requests to be routed to specific applications as defined in
[RFC3261]. The motivation for capturing the request history is that
in the process of retargeting a request, old routing information can
be forever lost. This lost information may be important history that
allows elements to which the request is retargeted to process the
request in a locally defined, application-specific manner. This
document defines a mechanism for transporting the request history.
Application-specific behavior is outside the scope of this
specification.
Current network applications provide the ability for elements
involved with the request to obtain additional information relating
to how and why the request was routed to a particular destination.
The following are examples of such applications:
1. Web "referral" applications, whereby an application residing
within a web server determines that a visitor to a website has
arrived at the site via an "associate" site that will receive
some "referral" commission for generating this traffic
2. Email forwarding whereby the forwarded-to user obtains a
"history" of who sent the email to whom and at what time
3. Traditional telephony services such as voicemail, call-center
"automatic call distribution", and "follow-me" style services
Several of the aforementioned applications currently define
application-specific mechanisms through which it is possible to
obtain the necessary history information.
In addition, request history information could be used to enhance
basic SIP functionality by providing the following:
o Some diagnostic information for debugging SIP requests.
Barnes, et al. Expires October 29, 2011 [Page 6]
Internet-Draft History-Info April 2011
o Capturing aliases and Globally Routable User Agent URIs (GRUUs)
[RFC5627], which can be overwritten by a home proxy upon receipt
of the initial request.
o Facilitating the use of limited use addresses (minted on demand)
and sub-addressing.
o Preserving service specific URIs that can be overwritten by a
downstream proxy, such as those defined in [RFC3087], and control
of network announcements and IVR with SIP URI [RFC4240].
4. Overview
The fundamental functionality provided by the request history
information is the ability to inform proxies and UAs involved in
processing a request about the history or progress of that request.
The solution is to capture the Request-URIs as a request is
retargeted, in a SIP header field: History-Info. This allows for the
capturing of the history of a request that would be lost with the
normal SIP processing involved in the subsequent retargeting of the
request.
The History-info header field is added to a Request when a new
request is created by a UAC or forwarded by a Proxy, or when the
target of a request is changed. It is possible for the target of a
request to be changed by the same proxy/SIP Intermediary multiple
times (referred to as 'internal retargeting'). A SIP entity changing
the target of a request in response to a redirect also propagates any
History-info header field from the initial request in the new
request. The ABNF and detailed description of the History-Info
header field parameters, along with examples is provided in
Section 5. Section 6, Section 7 and Section 8 provide the detailed
handling of the History-Info header field by SIP User Agents, Proxies
and Redirect Servers respectively.
This specification also defines two new SIP header field parameters,
"rc" and "mp", for the History-Info and Contact header fields, to tag
the method by which the target of a request is determined. Further
detail on the use of these header field parameters is provided in
Section 10.4.
In addition, this specification defines a priv-value for the Privacy
header, "history", that applies to all the History-info header field
entries in a Request or to a specific History-info header field hi-
entry as described above. Further detail is provided in
Section 10.1.
Barnes, et al. Expires October 29, 2011 [Page 7]
Internet-Draft History-Info April 2011
5. History-Info Header Field Protocol Structure
The History-info header field can appear in any request not
associated with an early or established dialog (e.g., INVITE,
REGISTER, MESSAGE, REFER and OPTIONS, PUBLISH and SUBSCRIBE, etc.)
and any non-100 provisional or final responses to these requests
(ISSUER-req, see Appendix A).
The following provides details for the information that is captured
in the History-Info header field entry (hi-entry) for each target
used for forwarding a request:
o hi-targeted-to-uri: A mandatory parameter for capturing the
Request-URI for the specific request as it is forwarded.
o hi-index: A mandatory parameter for History-Info reflecting the
chronological order of the information, indexed to also reflect
the forking and nesting of requests. The format for this
parameter is a string of digits, separated by dots to indicate the
number of forward hops and retargets. This results in a tree
representation of the history of the request, with the lowest-
level index reflecting a branch of the tree. By adding the new
entries in order (i.e., following existing entries per the details
in Section 10.3), including the index and sending the messages
using a secure transport, the ordering of the History-info header
fields in the request is assured. In addition, applications may
extract a variety of metrics (total number of retargets, total
number of retargets from a specific branch, etc.) based upon the
index values.
o hi-target-param: An optional parameter reflecting the mechanism by
which the Request URI captured in the hi-targeted-to-uri in the
hi-entry was determined. This parameter contains either an "rc"
or "mp" header field parameter, which is interpreted as follows:
"rc": The hi-targeted-to-URI is a contact bound to an AOR in an
abstract location service, that AOR being the Request-URI that
was retargeted. The AOR-to-contact binding has been placed
into the location service by a SIP Registrar that received a
SIP REGISTER request. The "rc" header field parameter contains
the value of the hi-index in the hi-entry with an
hi-targeted-to- uri that reflects the Request-URI that was
retargeted
"mp": The hi-targeted-to-URI represents a user other than the
user associated with the Request-URI in the incoming request
that was retargeted. This occurs when a request is statically
or dynamically retargeted to another user. The "mp" header
Barnes, et al. Expires October 29, 2011 [Page 8]
Internet-Draft History-Info April 2011
field parameter contains the value of the hi-index in the hi-
entry with an hi-targeted-to-uri that reflects the Request-URI
that was retargeted, thus identifying the "mapped from" target.
o Extension (hi-extension): A parameter to allow for future optional
extensions. As per [RFC3261], any implementation not
understanding an extension MUST ignore it.
The ABNF syntax for the History-info header field and header field
parameters is as follows:
History-Info = "History-Info" HCOLON hi-entry *(COMMA hi-entry)
hi-entry = hi-targeted-to-uri *(SEMI hi-param)
hi-targeted-to-uri = name-addr
hi-param = hi-index / hi-target-param / hi-extension
index-val = 1*DIGIT *("." 1*DIGIT)
hi-index = "index" EQUAL index-val
hi-target-param = rc-param / mp-param
rc-param = "rc" EQUAL index-val
mp-param = "mp" EQUAL index-val
hi-extension = generic-param
The ABNF definitions for "generic-param" and "name-addr" are from
[RFC3261].
This document also extends the "contact-params" for the Contact
header field as defined in [RFC3261] with the "rc" and "mp" header
field parameters defined above.
In addition to the parameters defined by the ABNF, an hi-entry may
also include a Reason header field and/or a Privacy header field,
which are both included in the "headers" component of the hi-
targeted-to-uri as described below:
o Reason: An optional parameter for History-Info, reflected in the
History-info header field by including the Reason header field
[RFC3326] included in the hi-targeted-to-uri. A reason is
included in the hi-targeted-to-uri of an hi-entry to reflect
Barnes, et al. Expires October 29, 2011 [Page 9]
Internet-Draft History-Info April 2011
information received in a response to the request sent to that
URI.
o Privacy: An optional parameter for History-Info, reflected in the
History-Info header field values by including the Privacy Header
[RFC3323] included in the hi- targeted-to-uri or by adding the
Privacy header field to the request. The latter case indicates
that the History-Info entries for the domain MUST be anonymized
prior to forwarding, whereas the use of the Privacy header field
included in the hi-targeted-to-uri means that a specific hi-entry
MUST be anonymized.
Note that since both the Reason and Privacy parameters are included
in the hi-targeted-to-uri, these fields will not be available in the
case that the hi-targeted-to-uri is a Tel-URI [RFC3966]. In such
cases, the Tel-URI SHOULD be transformed into a SIP URI per section
19.1.6 of [RFC3261].
The following provides examples of the format for the History-info
header field. Note that the backslash and CRLF between the fields in
the examples below are for readability purposes only.
History-Info: <sip:UserA@ims.example.com>;index=1;foo=bar
History-Info: <sip:UserA@ims.example.com?Reason=SIP%3B\
cause%3D302>;index=1.1,\
<sip:UserB@example.com?Privacy=history&Reason=SIP%3B\
cause%3D486>;index=1.2;mp=1.1,\
<sip:45432@192.168.0.3>;index=1.3;rc=1.2
5.1. History-Info Header Field Example Scenario
The following is an illustrative example of usage of History-Info.
In this example, Alice (sip:alice@atlanta.example.com) calls Bob
(sip:bob@biloxi.example.com). Alice's proxy in her home domain (sip:
atlanta.example.com) forwards the request to Bob's proxy (sip:
biloxi.example.com). When the request arrives at sip:
biloxi.example.com, it does a location service lookup for
bob@biloxi.example.com and changes the target of the request to Bob's
Contact URIs provided as part of normal SIP registration. In this
example, Bob is simultaneously contacted on a PC client and on a
phone, and Bob answers on the PC client.
One important thing illustrated by this call flow is that without
History-Info, Bob would "lose" the target information, including any
parameters in the request URI. Bob can recover that information by
Barnes, et al. Expires October 29, 2011 [Page 10]
Internet-Draft History-Info April 2011
locating the last hi-entry with an "rc" header field parameter. This
"rc" header field parameter contains the index of the hi-entry
containing the lost target information - i.e., the
sip:bob@biloxi.example.com hi-entry with index=1.1. Note that an hi-
entry is not included for the fork to sip:bob@192.0.2.7 since there
was no response at the time the 200 OK is sent to Alice.
The formatting in this scenario is for visual purposes; thus,
backslash and CRLF are used between the fields for readability.
Refer to Section 5.1 for the proper formatting. Additional detailed
scenarios are available in Appendix B.
Note: This example uses loose routing procedures.
Barnes, et al. Expires October 29, 2011 [Page 11]
Internet-Draft History-Info April 2011
Alice atlanta.example.com biloxi.example.com Bob@pc Bob@phone
| | | | |
| INVITE sip:bob@biloxi.example.com;p=x | |
|--------------->| | | |
| Supported: histinfo | | |
| | | | |
| | INVITE sip:bob@biloxi.example.com;p=x |
| |--------------->| | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 |
| | | | |
| | | INVITE sip:bob@192.0.2.3|
| | |--------------->| |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc=1.1
| | | | |
| | | INVITE sip:bob@192.0.2.7|
| | |-------------------------->|
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.7>;index=1.1.2;rc=1.1
| | | 200 | |
| | |<---------------| |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc=1.1
| | | | |
| | 200 | | |
| |<---------------| | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc=1.1
| | | | |
| | | Proxy Cancels INVITE |
| | |<=========================>|
| | | | |
| 200 | | | |
|<---------------| | | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3;index=1.1.1;rc=1.1
| | | | |
| ACK | | | |
|--------------->| ACK | | |
| |--------------->| ACK | |
| | |--------------->| |
Barnes, et al. Expires October 29, 2011 [Page 12]
Internet-Draft History-Info April 2011
Figure 1: Basic Call
6. User Agent Handling of the History-Info Header Field
A B2BUA MAY follow the behavior of a SIP intermediary as an
alternative to following the behavior of a UAS per Section 6.2 and a
UAC per Section 6.1. In behaving as an intermediary, a B2BUA carries
forward hi-entries received in requests at the UAS to requests being
forwarded by the UAC, as well as carrying forward hi-entries in
responses received at the UAC to the responses forwarded by the UAS,
subject to privacy considerations per Section 10.1.
6.1. User Agent Client (UAC) Behavior
The UAC MUST include the "histinfo" option tag in the Supported
header field in any new or out-of-dialog request for which the UAC
would like the History-info header field in the response. When
issuing a request, the UAC MUST follow the procedures in Section 9.2.
Note that in the case of an initial request, except where the UAC is
part of a B2BUA, there is no cache of hi-entries with which to
populate the History-info header field and the hi-index is set to 1
per Section 10.3. When receiving a response the UAC MUST follow the
procedures in Section 9.3.
6.2. User Agent Server (UAS) Behavior
When receiving a request, a UAS MUST follow the procedures defined in
Section 9.2. When sending a response other than a 3xx response, a
UAS MUST follows the procedures as defined in Section 9.4. When
sending a 3xx response, the UAS MUST follow the procedures defined
for a redirect server per Section 8. An application at the UAS can
make use of the cached hi-entries as described in Section 11.
7. Proxy/Intermediary Handling of History-Info Header Fields
This section describes the procedures for proxies and other SIP
intermediaries for the handling of the History-Info header fields for
each of the following scenarios:
Receiving a Request: An intermediary MUST follow the procedures in
Section 9.1 for the handling of hi-entries in incoming SIP
requests.
Barnes, et al. Expires October 29, 2011 [Page 13]
Internet-Draft History-Info April 2011
Sending a Request: For each outgoing request relating to a target
in the target set, the intermediary MUST follow the procedures of
Section 9.2.
Receiving a Response or Timeout: An intermediary MUST follow the
procedures of Section 9.3 when a SIP response is received or a
request times out.
Sending a Response: An intermediary MUST follow the procedures of
Section 9.4 for the handling of the hi-entries when sending a SIP
response.
In some cases, an intermediary may retarget a request more than once
before forwarding - i.e., a request is retargeted to a SIP entity
that is "internal" to the intermediary before the same intermediary
retargets the request to an external target . A typical example
would be a proxy that retargets a request first to a different user
(i.e., it maps to a different AOR) and then forwards to a registered
contact bound to the same AOR. In this case, the intermediary MUST
add an hi-entry for (each of) the internal target(s) per the
procedures in Section 9.2. The intermediary MAY include a Reason
header field in the hi-entry with the hi-targeted-to-uri that has
been retargeted as shown in the INVITE (F6) in the example in
Appendix B.1. Figure 1 provides an example of internal retargeting.
8. Redirect Server Handling of History-Info Header Fields
A redirect server MUST follow the procedures in Section 9.1 when it
receives a SIP Request. A redirect server MUST follow the procedures
in Section 9.4 when it sends a SIP Response. When generating the
Contact header field in a 3xx response, the redirect server MUST add
the appropriate target header field parameter to each Contact header
field as described in Section 10.4, if applicable.
9. Handling of History-Info Header Fields in Requests and Responses
This section describes the procedures for SIP entities for the
handling of the History-Info header field in SIP requests and
responses.
9.1. Receiving a Request
When receiving a request, a SIP entity MUST create a cache containing
the hi-entries associated with the request. The hi-entries MUST be
added to the cache in the order in which they were received in the
request.
Barnes, et al. Expires October 29, 2011 [Page 14]
Internet-Draft History-Info April 2011
If the Request-URI of the incoming request does not match the hi-
targeted-to-uri in the last hi-entry (i.e., the previous SIP entity
that sent the request did not include a History-Info header field),
the SIP entity MUST add an hi-entry to end of the cache, on behalf of
the previous SIP entity, as follows:
o The SIP entity MUST set the hi-targeted-to-uri to the value of the
Request-URI in the incoming request.
o If privacy is required, the SIP entity MUST follow the procedures
of Section 10.1.
o The SIP entity MUST set the hi-index parameter as described in
Section 10.3.
o The SIP entity MUST NOT include an "rc" or "mp" header field
parameter.
9.2. Sending a Request with History-Info
When sending a request, a SIP entity MUST include all cached hi-
entries in the request. In addition, the SIP entity MUST add a new
hi-entry to the outgoing request, but the SIP entity MUST NOT add the
new hi-entry to the cache at this time. The new hi-entry is
populated as follows:
hi-targeted-to-uri: The hi-targeted-to-uri MUST be set to the
value of the Request-URI of the current (outgoing) request.
privacy: If privacy is required, the procedures of Section 10.1
MUST be followed.
hi-index: The SIP entity MUST include an hi-index for the hi-entry
as described in Section 10.3.
rc/mp: The SIP entity MUST include an "rc" or "mp" header field
parameter in the hi-entry, if applicable, per the procedures in
Section 10.4.
9.3. Receiving a Response with History-Info or Request Timeouts
When a SIP entity receives a non-100 response or a request times out,
the SIP entity performs the following steps:
Barnes, et al. Expires October 29, 2011 [Page 15]
Internet-Draft History-Info April 2011
Step 1: Add hi-entry to cache
The SIP entity MUST add the hi-entry that was added to the request
that received the response or timed out to the cache, if it was
not already cached. The hi-entry MUST be added to the cache in
ascending order as indicated by the values in the hi-index
parameters of the hi-entries (e.g., 1.2.1 comes after 1.2 but
before 1.2.2 or 1.3).
Step 2: Add Reason header field
The SIP entity adds one or more Reason header fields to the hi-
targeted-to-uri in the (newly) cached hi-entry per the procedures
of Section 10.2, except in the case of a 2xx response.
Step 3: Add additional hi-entries
The SIP entity MUST also add to the cache any hi-entries received
in the response that are not already in the cache. This situation
can occur when the entity that generated the response retargeted
the request before generating the response. As per Step 1, the
hi-entries MUST be added to the cache in ascending order as
indicated by the values in the hi-index parameters of the hi-
entries
It is important to note that the cache does not contain hi-entries
for requests that have not yet received a non-100 response, so there
can be gaps in indices (e.g., 1.2 and 1.4 could but present but not
1.3).
9.4. Sending History-Info in Responses
When sending a response other than a 100, a SIP entity MUST include
all the cached hi-entries in the response, subject to the privacy
consideration in Section 10.1.2 with the following exception: If the
received request contained no hi-entries and there is no "histinfo"
option tag in the Supported header field, the SIP entity MUST NOT
include hi-entries in the response.
10. Processing the History-Info Header Field
The following sections describe the procedures for processing the
History-Info header field. These procedures are applicable to SIP
entities such as Proxies/Intermediaries, Redirect Servers or User
Agents.
Barnes, et al. Expires October 29, 2011 [Page 16]
Internet-Draft History-Info April 2011
10.1. Privacy in the History-Info Header Field
The privacy requirements for this document are described in
Appendix A.2. Section 10.1.1 describes the insertion of the Privacy
header field defined in [RFC3323] to indicate the privacy to be
applied to the History-Info header field entries. Section 10.1.2
describes how to apply privacy to a request or response that is being
forwarded, based on the presence of the Privacy header field.
10.1.1. Indicating Privacy
As with other SIP headers described in [RFC3323], the hi-targeted-to-
uris in the History-info header field can inadvertently reveal
information about the initiator of the request. Thus, the UAC needs
a mechanism to indicate that the hi-targeted-to-uris in the hi-
entries need to be privacy protected. The Privacy header field is
used by the UAC to indicate that privacy is to be applied to all the
hi-entries in the request as follows:
o If the UAC is including a Privacy header field with a priv-value
of "header" in the request, then the UAC SHOULD NOT include a
priv-value of "history" in the the Privacy header field in the
Request.
o If the UAC is including any priv-values other than "header" in the
Privacy header field, then the UAC MUST also include a priv-value
of "history" in the Privacy header field in the Request.
o If the UAC is not including any priv-values in the Privacy header
field in the request, then the UAC MUST add a Privacy header
field, with a priv-value of "history", to the request. The UAC
MUST NOT include a priv-value of "critical" in the Privacy header
field in the Request in this case.
In addition, the History-info header field can reveal general routing
and diverting information within an intermediary, which the
intermediary wants to privacy protect. In this case, the
intermediary MUST set a Privacy header field to a priv-value of
"history" and include the Privacy header field in the hi-targeted-to-
uri, for each new hi-entry added by the intermediary, as the request
is retargeted within the domain for which the SIP entity is
responsible. Note, that the hi-entries that are added to a request
from the cache are excluded in this case since the appropriate
privacy was set for those hi-entries when they were originally added
to a request. The intermediary MUST NOT include any other priv-
values in this Privacy header field. Note that the priv-value in the
Privacy header for the incoming request does not necessarily
influence whether the intermediary includes a Privacy header field in
Barnes, et al. Expires October 29, 2011 [Page 17]
Internet-Draft History-Info April 2011
the hi-entries. For example, even if the Privacy header for the
incoming request contained a priv-value of "none", the Proxy can
still set a priv-value of "history" in the Privacy header field
included in the hi-targeted-to-uri.
Finally, the terminator of the request may not want to reveal the
final reached target to the originator. In this case, the terminator
MUST include a Privacy header field with a priv-value of "history" in
the hi-targeted-to-uri in the last hi-entry, in the response. As
noted above, the terminator of the request MUST NOT use any other
priv-values in the Privacy header field included in the hi-entry.
10.1.2. Applying Privacy
When a request is retargeted to a URI associated with a domain for
which the SIP intermediary is not responsible or a response is
forwarded to a domain for which the SIP intermediary is not
responsible, a Privacy Service at the boundary of the domain applies
the appropriate privacy based on the value of the Privacy header
field in the message header or in the "headers" component of the hi-
targeted-to-uri in the individual hi-entries.
If there is a Privacy header field in the message header of a request
or response, with a priv-value of "header" or "history", then all the
hi-targeted-to-uris in the hi-entries, associated with the domain for
which a SIP intermediary is responsible, are anonymized by the
Privacy Service. The Privacy Service MUST change any hi-targeted-to-
uris in the hi-entries that have not been anonymized to anonymous
URIs containing a domain of anonymous.invalid (e.g.,
anonymous@anonymous.invalid). If there is a Privacy header field in
the "headers" component of the hi-targeted-to-uri in the hi-entry,
then the Privacy header field value MUST be removed from the hi-
entry. Once all the appropriate hi-entries have been anonymized, the
Privacy Service MUST remove the priv-value of "history" from the
Privacy header field in the message header of the request or
response. If there are no remaining priv-values in the Privacy
header field, the Privacy Service MUST remove the Privacy header
field from the request or response per [RFC3323].
If there is not a Privacy header field in the message header of the
request or response that is being forwarded, but there is a Privacy
header field with a priv-value of "history" in the "headers"
component in any of the hi-targeted-uris in the hi-entries associated
with the domain for which a SIP intermediary is responsible, then the
Privacy Service MUST anonymize those hi-targeted-to-uris. The
Privacy Service MUST populate each of the hi-targeted-to-uris with an
anonymous URI with a domain of anonymous.invalid (e.g.,
anonymous@anonymous.invalid). Any other priv-values in the Privacy
Barnes, et al. Expires October 29, 2011 [Page 18]
Internet-Draft History-Info April 2011
header field in the "headers" component of the hi-targeted-to-uris in
the hi-entries MUST be ignored. In any case, the Privacy Service
MUST remove the Privacy header field from the "headers" compenent of
the hi-targeted-to-uris in the hi-entries prior to forwarding.
10.2. Reason in the History-info Header Field
A Reason header field is added to the "headers" component in an hi-
targeted-to-uri when the hi-entry is added to the cache based upon
the receipt of a non-100 or non-2xx SIP response, as described in
Section 9.3. If the Reason header field is being added due to
receipt of an explicit SIP response and the response contains any
Reason header fields (see [RFC3326]), then the SIP entity MUST
include the Reason header fields in the "headers" component of the
hi-targeted-to-uri in the last hi-entry added to the cache, unless
the hi-targeted-to-uri is a Tel-URI. If the SIP response does not
contain a Reason header field, the SIP entity MUST include a Reason
header field, containing the SIP Response Code, in the "headers"
component of the hi-targeted-to-uri in the last hi-entry added to the
cache, unless the hi-targeted-to-uri is a Tel-URI.
If a request has timed out (instead of being explicitly rejected),
the SIP entity MUST include a Reason header field, containing a SIP
error response code of 408 "Request Timeout".
A SIP entity MAY also include a Reason header field in the "headers"
component of an hi-targeted-to-uri containing the URI of a request
that was retargeted as a result of internal retargeting.
If new protocol values for Reason headers are specified in the future
per [RFC3326], the use of these Reason headers for the History-Info
header field MUST follow the same rules as described above.
10.3. Indexing in the History-Info Header Field
In order to maintain ordering and accurately reflect the retargeting
of the request, the SIP entity MUST add an hi-index to each hi-entry.
Per the syntax in Section 5, the hi-index consists of a series of
digits separated by dots (e.g., 1.1.2). Each dot reflects a SIP
forwarding hop. The digit following each dot reflects the order in
which a request was retargeted at the hop. The highest digit at each
hop reflects the number of entities to which the request has been
retargeted at the specific hop (i.e., the number of branches). Thus,
the indexing results in a logical tree representation for the history
of the request.
The first index in a series of History-Info entries MUST be set to 1.
In the case that a SIP entity (intermediary or UAS) adds an hi-entry
Barnes, et al. Expires October 29, 2011 [Page 19]
Internet-Draft History-Info April 2011
on behalf of the previous hop, the hi-index MUST be set to 1. For
each forward hop (i.e., each new level of indexing), the hi-index
MUST start at 1. An increment of 1 MUST be used for advancing to a
new branch.
The basic rules for adding the hi-index are summarized as follows:
1. Forwarding a request without changing the target: In the case of
a request that is being forwarded without changing the target,
the hi-index reflects the increasing length of the branch. In
this case, the SIP entity MUST read the value from the History-
info header field in the received request and MUST add another
level of indexing by appending the dot delimiter followed by an
initial value of 1 for the new level. For example, if the hi-
index in the last History-info header field in the received
request is 1.1, a proxy would add an hi-entry with an hi-index of
1.1.1 and forward the request.
2. Retargeting within a processing entity - 1st instance: For the
first instance of retargeting within a processing entity, the SIP
entity MUST calculate the hi-index as prescribed for basic
forwarding.
3. Retargeting within a processing entity - subsequent instance: For
each subsequent retargeting of a request by the same SIP entity,
the SIP entity MUST calculate and add the hi-index for each new
branch by incrementing the rightmost value from the hi-index in
the last hi-entry. Per the example above, the hi-index in the
next request forwarded by this same SIP entity would be 1.1.2.
4. Retargeting based upon a Response: In the case of retargeting due
to a specific response (e.g., 302), the SIP entity MUST calculate
the hi-index calculated per rule 3. That is, the rightmost value
of the hi-index MUST be incremented (i.e., a new branch is
created). For example, if the hi-index in the History-Info
header of the sent request is 1.2 and the response to the request
is a 302, then the hi-index in the History-Info header field for
the new hi-targeted- to-URI would be 1.3.
5. Forking requests: If the request forwarding is done in multiple
forks (sequentially or in parallel), the SIP entity MUST set the
hi-index for each hi-entry for each forked request per the rules
above, with each new request having a unique index. Each index
MUST be sequentially assigned. For example, if the index in the
last History-Info header field in the received request is 1.1,
this processing entity would initialize its index to 1.1.1 for
the first fork, 1.1.2 for the second, and so forth (see Figure 1
for an example). Note, that in the case of parallel forking,
Barnes, et al. Expires October 29, 2011 [Page 20]
Internet-Draft History-Info April 2011
only the hi-entry corresponding to the fork is included in the
request.
10.4. Indicating the Mechanism by which the Target was Determined
This specification defines two header field parameters, "rc" and
"mp", indicating two mechanisms by which a new target for a request
is determined. Both parameters contain an index whose value is the
hi-index of the hi-entry with an hi-targeted-to-uri that represents
the Request-URI that was retargeted.
The SIP entity MUST determine the specific parameter field to be
included in the hi-target-param, in the History-info header field, as
the targets are added to the target set per the procedures in section
16.5 of [RFC3261] or per section 8.1.3.4 [RFC3261] in the case of
retargeting to a contact URI received in a 3xx response. In the
latter case, the specific header parameter field in the Contact
header becomes the header field parameter that is used in the hi-
target-param in the hi-entry when the request is retargeted. If the
Contact header field does not contain an "rc" or "mp" header field
parameter, then the SIP entity MUST NOT include an "rc" or "mp"
header field parameter in the hi-target-param in the hi-entry when
the request is retargeted to a contact URI received in a 3xx
response.
The SIP entity (intermediary or redirect server) determines the
specific header field parameter ("rc" or "mp") to be used based on
the criteria defined in Section 5 (hi-target-param) for each of the
header field parameters.
Note that there are two scenarios by which the "mp" header field
parameter can be derived.
o The mapping was done by the receiving entity on its own authority,
in which case the mp-value is the parent index of the hi-entry's
index.
o The mapping was done due to receiving a 3xx response, in which
case the mp-value is an earlier sibling or descendant of an
earlier sibling of the hi-entry's index, that of the downstream
request which received the 3xx response.
11. Application Considerations
History-Info provides a very flexible building block that can be used
by intermediaries and UAs for a variety of services. Prior to any
application usage of the History-Info header field parameters, the
Barnes, et al. Expires October 29, 2011 [Page 21]
Internet-Draft History-Info April 2011
SIP entity that processes the hi-entries MUST evaluate the hi-
entries. The SIP entity MUST determine if there are gaps in the
indices. Gaps are possible if the request is forwarded through
intermediaries that do not support the History-info header field and
are reflected by the existence of multiple hi-entries with an index
of "1". Gaps are also possible in the case of parallel forking if
there is an outstanding request at the time the SIP entity sends a
response as described in Section 9.4. Thus, if gaps are detected,
the SIP entity MUST NOT treat this as an error, but SHOULD indicate
to any applications that there are gaps. The interpretation of the
information in the History-info header field depends upon the
specific application; an application might need to provide special
handling in some cases where there are gaps.
The following describes some categories of information that
applications can use:
1. Complete history information - e.g., for debug or other
operational and management aspects, optimization of determining
targets to avoid retargeting to the same URI, etc. This
information is relevant to proxies, UACs and UASs.
2. Hi-entry with the index that matches the value of the "rc" header
field parameter in the last hi-entry with an "rc" header field
parameter in the Request received by a UAS - i.e., the last AOR
that was retargeted to a contact based on an AOR-to-contact
binding in an abstract location service.
3. Hi-entry with the index that matches the value of the "mp" header
field parameter in the last hi-entry with an "mp" header field
parameter in the hi-target-param in the Request received by a UAS
- i.e., the last Request URI that was mapped to reach the
destination.
4. Hi-entry with the index that matches the value of the "rc" header
field parameter in the first hi-entry with an "rc" header field
parameter in the Request received by a UAS. Note, this would be
the original AoR if all the entities involved support the
History-info header field and there is absence of an "mp" header
field parameter prior to the "rc" header field parameter in the
hi-target-param in the History-info header field. However, there
is no guarantee that all entities will support History-Info, thus
the hi-entry that matches the value of the "rc" parameter of the
first hi-entry with an "rc" parameter in the hi-target-param
within the domain associated with the target URI at the
destination is more likely to be useful.
Barnes, et al. Expires October 29, 2011 [Page 22]
Internet-Draft History-Info April 2011
5. Hi-entry with the index that matches the value of "mp" header
field parameter in the first hi-entry with an "mp" header field
parameter in the Request received by a UAS. Note, this would be
the original mapped URI if all entities supported the History-
info header field. However, there is no guarantee that all
entities will support History-Info, thus the hi-entry that
matches the value of the "mp" header field parameter of the first
hi-entry with an "mp" header field parameter within the domain
associated with the target URI at the destination is more likely
to be useful.
In many cases, applications are most interested in the information
within a particular domain(s), thus only a subset of the information
is required.
Some applications may use multiple types of information. For
example, an Automatic Call Distribution (ACD)/Call center application
that utilizes the hi-entry whose index matches the value of the "mp"
header field parameter of the first hi-entry with an "mp" header
field parameter, may also display other agents, reflected by other
hi-entries prior to entries with an "rc" header field parameter, to
whom the call was targeted prior to its arrival at the current agent.
This could allow the agent the ability to decide how they might
forward or reroute the call if necessary (avoiding agents that were
not previously available for whatever reason, etc.).
Since support for History-info header field is optional, a service
MUST define default behavior for requests and responses not
containing History-Info header fields. For example, an entity may
receive an incomplete set of hi-entries or hi-entries which are not
tagged appropriately with an hi-target-param. This may not impact
some applications (e.g., debug), however, it could require some
applications to make some default assumptions in this case. For
example, in an ACD scenario, the application could select the oldest
hi-entry with the domain associated with the ACD system and display
that as the original called party. Depending upon how and where the
request may have been retargeted, the complete list of agents to whom
the call was targeted may not be available.
12. Security Considerations
The security requirements for this document are specified in
Appendix A.1.
This document defines a header for SIP. The use of the Transport
Layer Security (TLS) protocol [RFC5246] as a mechanism to ensure the
overall confidentiality of the History-Info headers (SEC-req-4) is
Barnes, et al. Expires October 29, 2011 [Page 23]
Internet-Draft History-Info April 2011
strongly RECOMMENDED. This results in History-Info having at least
the same level of security as other headers in SIP that are inserted
by intermediaries. With TLS, History-Info headers are no less, nor
no more, secure than other SIP headers, which generally have even
more impact on the subsequent processing of SIP sessions than the
History-info header field.
Note that while using the SIPS scheme (as per [RFC5630]) protects
History-Info from tampering by arbitrary parties outside the SIP
message path, all the intermediaries on the path are trusted
implicitly. A malicious intermediary could arbitrarily delete,
rewrite, or modify History-Info. This specification does not attempt
to prevent or detect attacks by malicious intermediaries.
In terms of ensuring the privacy of hi-entries, the same security
considerations as those described in [RFC3323] apply. Namely if the
entity requesting privacy wants to ensure privacy is applied to the
hi-entries, a Privacy Service that supports both [RFC3323] and this
specification is REQUIRED in the entity's domain, so that the privacy
can be applied, as described in Section 10.1.2, when a request or
response leaves the domain.
13. IANA Considerations
This document requires several IANA registrations detailed in the
following sections.
This document obsoletes [RFC4244] but uses the same SIP header field
name and option tag. The IANA registry needs to update the
references to [RFC4244] with [RFCXXXX].
13.1. Registration of New SIP History-Info Header Field
This document defines a SIP header field name: History-Info and an
option tag: histinfo. The following changes have been made to
http:///www.iana.org/assignments/sip-parameters The following row has
been added to the header field section:.
The following row has been added to the header field section:
Header Name Compact Form Reference
----------- ------------ ---------
History-Info none [RFCXXXX]
The following has been added to the Options Tags section:
Barnes, et al. Expires October 29, 2011 [Page 24]
Internet-Draft History-Info April 2011
Name Description Reference
---- ----------- ---------
histinfo When used with the Supported header, [RFCXXXX]
this option tag indicates the UAC
supports the History Information to be
captured for requests and returned in
subsequent responses. This tag is not
used in a Proxy-Require or Require
header field since support of
History-Info is optional.
Note to RFC Editor: Please replace RFCXXXX with the RFC number of
this specification.
13.2. Registration of "history" for SIP Privacy Header Field
This document defines a priv-value for the SIP Privacy header field:
history The following changes have been made to
http://www.iana.org/assignments/sip-priv-values The following has
been added to the registration for the SIP Privacy header field:
Name Description Registrant Reference
---- ----------- ---------- ---------
history Privacy requested for Mary Barnes [RFCXXXX]
History-info header mary.barnes@polycom.com
fields(s)
Note to RFC Editor: Please replace RFC XXXX with the RFC number of
this specification.
13.3. Registration of Header Field Parameters
This specification defines the following new SIP header field
parameters in the SIP Header Field parameter sub-registry in the SIP
Parameter Registry, http:/www.iana.org/assignments/sip-parameters.
Header Field Parameter Name Predefined Reference
Values
_____________________________________________________________________
History-Info mp No [RFC xxxx]
History-Info rc No [RFC xxxx]
Contact mp No [RFC xxxx]
Contact rc No [RFC xxxx]
Barnes, et al. Expires October 29, 2011 [Page 25]
Internet-Draft History-Info April 2011
Note to RFC Editor: Please replace RFC XXXX with the RFC number of
this specification.
14. Acknowledgements
Jonathan Rosenberg et al produced the document that provided
additional use cases precipitating the requirement for the new header
parameters to capture the method by which a Request URI is
determined. The authors would like to acknowledge the constructive
feedback provided by Ian Elz, Paul Kyzivat, John Elwell, Hadriel
Kaplan and Dale Worley. John Elwell provided excellent suggestions
in terms of document structure.
Mark Watson, Cullen Jennings and Jon Peterson provided significant
input into the initial work that resulted in the development of of
[RFC4244]. The editor would like to acknowledge the constructive
feedback provided by Robert Sparks, Paul Kyzivat, Scott Orton, John
Elwell, Nir Chen, Palash Jain, Brian Stucker, Norma Ng, Anthony
Brown, Jayshree Bharatia, Jonathan Rosenberg, Eric Burger, Martin
Dolly, Roland Jesske, Takuya Sawada, Sebastien Prouvost, and
Sebastien Garcin in the development of [RFC4244].
The editor would like to acknowledge the significant input from Rohan
Mahy on some of the normative aspects of the ABNF for [RFC4244],
particularly around the need for and format of the index and around
the security aspects.
15. Changes from RFC 4244
This RFC replaces [RFC4244].
Deployment experience with [RFC4244] over the years has shown a
number of issues, warranting an update:
o In order to make [RFC4244] work in "real life", one needs to make
"assumptions" on how History-Info is used. For example, many
implementations filter out many entries, and only leave specific
entries corresponding, for example, to first and last redirection.
Since vendors uses different rules, it causes significant
interoperability isssues.
o [RFC4244] is overly permissive and evasive about recording
entries, causing interoperability issues.
o The examples in the call flows had errors, and confusing because
they often assume "loose routing".
Barnes, et al. Expires October 29, 2011 [Page 26]
Internet-Draft History-Info April 2011
o [RFC4244] has lots of repetitive and unclear text due to the
combination of requirements with solution.
o [RFC4244] gratuitously mandates the use of TLS on every hop. No
existing implementation enforces this rule, and instead, the use
of TLS or not is a general SIP issue, not an [RFC4244] issue per
se.
o [RFC4244] does not include clear procedures on how to deliver
current target URI information to the UAS when the Request-URI is
replaced with a contact.
o [RFC4244] does not allow for marking History-Info entries for easy
processing by User Agents.
The following summarizes the functional changes between this
specification and [RFC4244]:
1. Added header field parameters to capture the specific method by
which a target is determined to facilitate processing by users of
the History-info header field entries. A specific header field
parameter is captured for each of the target URIs as the target
set is determined (per section 16.5 of [RFC3261]). The header
field parameter is used in both the History-Info and the Contact
header fields.
2. Rather than recommending that entries be removed in the case of
certain values of the Privacy header field, the entries are
anonymized.
3. Updated the security section to be equivalent to the security
recommendations for other SIP headers inserted by intermediaries.
The first 2 changes are intended to facilitate application usage of
the History-info header field and eliminate the need to make
assumptions based upon the order of the entries and ensure that the
most complete set of information is available to the applications.
In addition, editorial changes were done to both condense and clarify
the text, moving the requirements to an appendix and removing the
inline references to the requirements. The examples were simplified
and updated to reflect the protocol changes. Several of the call
flows in the appendix were removed and put into a separate document
that includes additional use cases that require the new header
parameters.
Barnes, et al. Expires October 29, 2011 [Page 27]
Internet-Draft History-Info April 2011
15.1. Backwards compatibility
This specification is backwards compatible since [RFC4244] allows for
the addition of new optional parameters. This specification adds an
optional SIP header field parameter to the History-Info and Contact
headers. Entities that have not implemented this specification MUST
ignore these parameters, however, per [RFC4244] an entity MUST NOT
remove this parameter from an hi-entry.
16. Changes since last Version
NOTE TO THE RFC-Editor: Please remove this section prior to
publication as an RFC.
Changes from 04 to 05:
1. Lots of editorial corrections/clarifications per John Elwell's
comment.
2. Updated Reason header section 10.2 to be consistent (i.e.,
removed references to retargeting) with section 9.3 (Receiving a
response) where the hi-entries and reason header are added to the
cache.
3. Updated section 9.3 (receiving responses) to also include
timeouts and updated to reflect that we don't add the Reason
header in the case of 2xx responses.
4. Added text in Security considerations with regards to needing a
Privacy Service per RFC 3323 to ensure that the privacy is
applied.
Changes from 03 to 04:
1. Reorganization of sections per John Elwell's comments - i.e., a
common section for building HI referenced by the UA, Intermediary
and Redirect server sections.
2. Removing the use of "escape" when describing the handling of the
Privacy and Reason header fields.
3. Clarification of TEL URIs in terms of not having a Privacy or
Reason header field in the hi-targeted-to-uri.
Changes from 02 to 03:
Barnes, et al. Expires October 29, 2011 [Page 28]
Internet-Draft History-Info April 2011
1. Lots of editorial:
A. Reorganized sections similar to the RFC 4244 order - i.e.,
introduce header field parameters and syntax first, then
describe how the functional entities use the header. This
removes redundant (and often inconsistent) text describing
the parameters.
B. Expanded use of "header" to "header field"
C. More precision in terms of "escaping" of the Privacy and
Reason headers in the hi-targeted-to-uri (versus
"adding"/"setting"/etc. them to the hi-entry).
D. Consistent use of parameter names (i.e., hi-entry versus
entry, hi-target versus target, etc.)
E. Moved item 6 in the Index section to the section on Response
handling
F. Removed last remaining vestiges of inline references to
requirements.
2. Clarifications of functionality/applicability including:
A. which messages may contain History-Info
B. removing security text with regards to being able to figure
out if there are missing entries when using TLS (issue #44)
C. More complete information on the new header field parameters
as they relate to the hi-target parameter.
D. Changed wording from passive to active for normative
statements in many cases and removed superfluous normative
language.
3. Rewrite of the Privacy section to address issues and splitting
into the setting of the Privacy header fields and the processing/
application of the privacy header field priv-values.
4. Rewrite of the Reason header field section - simplifying the text
and adding back the RFC 4244 text with regards to the use of the
Reason header field in cases of internal retargeting.
Changes from 01 to 02:
Barnes, et al. Expires October 29, 2011 [Page 29]
Internet-Draft History-Info April 2011
1. Editorial nits/clarifications. [Issues: 1,6,17,18,21-
23,25,26,30-33,35-37,39,40]
2. Removing extraneous 4244 text - e.g., errors in flows,
"stronger" security, "session" privacy. [Issues: 3,5,7,11 ]
3. Updated definition of "retarget" to be all encompassing - i.e.,
also includes internal changes of target URI. Clarified text
for "internal retarging" in proxy section. [Issues: 2,8,9]
4. Clarified that the processing for Proxies is equally applicable
to other SIP intermediaries. [Issue: 9].
5. Changed more SHOULDs to MUSTs. [Issue: 10]
6. Fixes to Application considerations section. [Issues: 12-15]
7. Changed language in the procedure for Indexing to normative
language.
8. Clarifications for UAC processing:
* MUST add hi-entry. [Issue: 28]
* Clarify applicability to B2BUA. [Issue: 29]
* Fixed text for indexing for UAC in case of 3xx.
9. Changed "hit" URI parameter to header parameters: [Issues:4,40]
* Added index to all target header parameters. [Issues: 41]
* Updated all the relevant sections documenting setting and use
of new header parameters. [Issue: 40]
10. Updated/clarified privacy handling. [Issue: 16]
11. Updated Redirect Server section to allow adding History-info
header fields. [Issue: 24 ]
12. Added text around restrictions for Tel-URIs - i.e., no privacy
or reason. [Issues: 4, 12]
13. Updated text for forking - what goes in response. [Issues:
19,20]
Changes from 00 to 01:
Barnes, et al. Expires October 29, 2011 [Page 30]
Internet-Draft History-Info April 2011
1. Moved examples (except first) in appendix to a new
(informational) document.
2. Updated UAS and UAC sections to clarify and expand on the
handling of the History-info header field.
3. Updated the Application considerations section:
4.
* Included more detail with regards to how applications can make
use of the information, in particular based on the new tags.
* Removed privacy consideration (2nd bullet) since privacy is
now accomplished by anonymizing rather than removal of
entries.
Changes from (individual) barnes-sipcore-4244bis-03 to (WG) ietf-
sipcore-4244bis-00:
1. Added a new SIP/SIPS URI parameter to tag the URIs as they are
added to the target list and those returned in the contact header
in a 3xx response.
2. Updated description of "target" parameter to use the new URI
parameter value in setting the value for the parameter.
3. Clarified privacy.
4. Changed handling at redirect server to include the use of the new
URI parameter and to remove the functionality of adding the
History-Info entries (basically reverting to core 4244
processing).
5. Additional text to clarify that a service such as voicemail can
be done in multiple ways.
6. Editorial changes including removal of some vestiges of tagging
all entries (including the "aor" tag).
Changes from barnes-sipcore-4244bis-02 to 03:
1. Fixed problem with indices in example in voicemail example.
2. Removed oc and rt from the Hi-target parameter.
3. Removed aor tag
Barnes, et al. Expires October 29, 2011 [Page 31]
Internet-Draft History-Info April 2011
4. Added index parameter to "mp"
5. Added use-cases and call-flows from target-uri into appendix.
Changes from barnes-sipcore-4244bis-01 to 02:
1. Added hi-aor parameter that gets marked on the "incoming" hi-
entry.
2. Hi-target parameter defined to be either rc, oc, mp, rt, and now
gets included when adding an hi-entry.
3. Added section on backwards compatibility, as well as added the
recognition and handling of requests that do not support this
specification in the appropriate sections.
4. Updated redirect server/3xx handling to support the new
parameters - i.e., the redirecting entity must add the new hi-
entry since the proxy does not have access to the information as
to how the Contact was determined.
5. Added section on normative differences between this document and
RFC 4244.
6. Restructuring of document to be more in line with current IETF
practices.
7. Moved Requirements section into an Appendix.
8. Fixed ABNF to remove unintended ordering requirement on hi-index
that was introduced in attempting to illustrate it was a
mandatory parameter.
Changes from barnes-sipcore-4244bis-00 to 01 :
1. Clarified "retarget" definition.
2. Removed privacy discussion from optionality section - just refer
to privacy section.
3. Removed extraneous text from target-parameter (leftover from sip-
4244bis). Changed the terminology from the "reason" to the
"mechanism" to avoid ambiguity with parameter.
4. Various changes to clarify some of the text around privacy.
5. Reverted proxy response handling text to previous form - just
changing the privacy aspects to anonymize, rather than remove.
Barnes, et al. Expires October 29, 2011 [Page 32]
Internet-Draft History-Info April 2011
6. Other editorial changes to condense and simplify.
7. Moved Privacy examples to Appendix.
8. Added forking to Basic call example.
Changes from barnes-sipcore-4244bis-00 to 01 :
1. Clarified "retarget" definition.
2. Removed privacy discussion from optionality section - just refer
to privacy section.
3. Removed extraneous text from target-parameter (leftover from sip-
4244bis). Changed the terminology from the "reason" to the
"mechanism" to avoid ambiguity with parameter.
4. Various changes to clarify some of the text around privacy.
5. Reverted proxy response handling text to previous form - just
changing the privacy aspects to anonymize, rather than remove.
6. Other editorial changes to condense and simplify.
7. Moved Privacy examples to Appendix.
8. Added forking to Basic call example.
Changes from barnes-sip-4244bis-00 to barnes-sipcore-4244bis-00:
1. Added tags for each type of retargeting including proxy hops,
etc. - i.e., a tag is defined for each specific mechanism by
which the new Request-URI is determined. Note, this is
extremely helpful in terms of backwards compatibility.
2. Fixed all the examples. Made sure loose routing was used in all
of them.
3. Removed example where a proxy using strict routing is using
History-Info for avoiding trying same route twice.
4. Remove redundant Redirect Server example.
5. Index is now mandated to start at "1" instead of recommended.
6. Updated 3xx behavior as the entity sending the 3XX response MUST
add the hi-target attribute to the previous hi-entry to ensure
that it is appropriately tagged (i.e., it's the only one that
Barnes, et al. Expires October 29, 2011 [Page 33]
Internet-Draft History-Info April 2011
knows how the contact in the 3xx was determined.)
7. Removed lots of ambiguity by making many "MAYs" into "SHOULDs"
and some "SHOULDs" into "MUSTs".
8. Privacy is now recommended to be done by anonymizing entries as
per RFC 3323 instead of by removing or omitting hi-entry(s).
9. Requirement for TLS is now same level as per RFC 3261.
10. Clarified behavior for "Privacy" (i.e., that Privacy is for Hi-
entries, not headers).
11. Removed "OPTIONALITY" as specific requirements, since it's
rather superflous.
12. Other editorial changes to remove redundant text/sections.
Changes from RFC4244 to barnes-sip-4244bis-00:
1. Clarified that HI captures both retargeting as well as cases of
just forwarding a request.
2. Added descriptions of the usage of the terms "retarget",
"forward" and "redirect" to the terminology section.
3. Added additional examples for the functionality provided by HI
for core SIP.
4. Added hi-target parameter values to HI header to ABNF and
protocol description, as well as defining proxy, UAC and UAS
behavior for the parameter.
5. Simplified example call flow in section 4.5. Moved previous call
flow to appendix.
6. Fixed ABNF per RFC4244 errata "dot" -> "." and added new
parameter.
17. References
17.1. Normative References
[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.
Barnes, et al. Expires October 29, 2011 [Page 34]
Internet-Draft History-Info April 2011
[RFC3326] Schulzrinne, H., Oran, D., and G. Camarillo, "The Reason
Header Field for the Session Initiation Protocol (SIP)",
RFC 3326, December 2002.
[RFC3323] Peterson, J., "A Privacy Mechanism for the Session
Initiation Protocol (SIP)", RFC 3323, November 2002.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC4244] Barnes, M., "An Extension to the Session Initiation
Protocol (SIP) for Request History Information", RFC 4244,
November 2005.
17.2. Informative References
[RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User
Agent URIs (GRUUs) in the Session Initiation Protocol
(SIP)", RFC 5627, October 2009.
[RFC5630] Audet, F., "The Use of the SIPS URI Scheme in the Session
Initiation Protocol (SIP)", RFC 5630, October 2009.
[RFC3087] Campbell, B. and R. Sparks, "Control of Service Context
using SIP Request-URI", RFC 3087, April 2001.
[RFC4240] Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network
Media Services with SIP", RFC 4240, December 2005.
[RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
RFC 3966, December 2004.
Appendix A. Request History Requirements
The following list constitutes a set of requirements for a "Request
History" capability.
1. CAPABILITY-req: The "Request History" capability provides a
capability to inform proxies and UAs involved in processing a
request about the history/progress of that request. Although
this is inherently provided when the retarget is in response to a
SIP redirect, it is deemed useful for non-redirect retargeting
scenarios, as well.
Barnes, et al. Expires October 29, 2011 [Page 35]
Internet-Draft History-Info April 2011
2. GENERATION-req: "Request History" information is generated when
the request is retargeted.
A. In some scenarios, it might be possible for more than one
instance of retargeting to occur within the same Proxy. A
proxy MUST also generate Request History information for the
'internal retargeting'.
B. An entity (UA or proxy) retargeting in response to a redirect
or REFER MUST include any Request History information from
the redirect/REFER in the new request.
3. ISSUER-req: "Request History" information can be generated by a
UA or proxy. It can be passed in both requests and responses.
4. CONTENT-req: The "Request History" information for each
occurrence of retargeting shall include the following:
A. The new URI or address to which the request is in the process
of being retargeted,
B. The URI or address from which the request was retargeted, and
wether the retarget URI was an AOR
C. The mechanism by which the new URI or address was determined,
D. The reason for the Request-URI or address modification,
E. Chronological ordering of the Request History information.
5. REQUEST-VALIDITY-req: Request History is applicable to requests
not sent within an early or established dialog (e.g., INVITE,
REGISTER, MESSAGE, and OPTIONS).
6. BACKWARDS-req: Request History information may be passed from the
generating entity backwards towards the UAC. This is needed to
enable services that inform the calling party about the dialog
establishment attempts.
7. FORWARDS-req: Request History information may also be included by
the generating entity in the request, if it is forwarded onwards.
A.1. Security Requirements
The Request History information is being inserted by a network
element retargeting a Request, resulting in a slightly different
problem than the basic SIP header problem, thus requiring specific
consideration. It is recognized that these security requirements can
Barnes, et al. Expires October 29, 2011 [Page 36]
Internet-Draft History-Info April 2011
be generalized to a basic requirement of being able to secure
information that is inserted by proxies.
The potential security problems include the following:
1. A rogue application could insert a bogus Request History-Info
entry either by adding an additional hi-entry as a result of
retargeting or entering invalid information.
2. A rogue application could re-arrange the Request History
information to change the nature of the end application or to
mislead the receiver of the information.
3. A rogue application could delete some or all of the Request
History information.
Thus, a security solution for "Request History" must meet the
following requirements:
1. SEC-req-1: The entity receiving the Request History must be able
to determine whether any of the previously added Request History
content has been altered.
2. SEC-req-2: The ordering of the Request History information must
be preserved at each instance of retargeting.
3. SEC-req-3: The entity receiving the information conveyed by the
Request History must be able to authenticate the entity providing
the request.
4. SEC-req-4: To ensure the confidentiality of the Request History
information, only entities that process the request SHOULD have
visibility to the information.
It should be noted that these security requirements apply to any
entity making use of the Request History information.
A.2. Privacy Requirements
Since the Request-URI that is captured could inadvertently reveal
information about the originator, there are general privacy
requirements that MUST be met:
1. PRIV-req-1: The entity retargeting the Request must ensure that
it maintains the network-provided privacy (as described in
[RFC3323]) associated with the Request as it is retargeted.
Barnes, et al. Expires October 29, 2011 [Page 37]
Internet-Draft History-Info April 2011
2. PRIV-req-2: The entity receiving the Request History must
maintain the privacy associated with the information. In
addition, local policy at a proxy may identify privacy
requirements associated with the Request-URI being captured in
the Request History information.
3. PRIV-req-3: Request History information subject to privacy shall
not be included in ougoing messages unless it is protected as
described in [RFC3323].
Appendix B. Example call flows
The scenarios in this section provide sample use cases for the
History-info header field for informational purposes only. They are
not intended to be normative. A basic forking use case is included,
along with two use cases illustrating the use of the privacy.
B.1. Sequentially Forking (History-Info in Response)
This scenario highlights an example where the History-Info in the
response is useful to an application or user that originated the
request.
Alice sends a call to Bob via sip:example.com. The proxy sip:
example.com sequentially tries Bob on a SIP UA that has bound a
contact with the sip:bob@example.com AOR, and then several alternate
addresses (Office and Home) unsuccessfully before sending a response
to Alice. The hi-entry containing the initial contact is the hi-
entry just prior to the first hi-entry tagged with an "rc" header
field parameter. In this example, the Office and Home are not the
same AOR as sip:bob@example.com, but rather different AORs that have
been configured as alternate addresses for Bob in the proxy. In
other words, Office and Bob are not bound through SIP Registration
with Bob's AOR. This type of arrangement is common for example when
a "routing" rule to a PSTN number is manually configured in a Proxy.
These hi-entries are identified by the index contained in the hi-
target-param "mp" header field parameter in the hi-entries.
This scenario illustrates that by providing the History-Info to
Alice, the end-user or an application at Alice could make a decision
on how best to attempt finding Bob without sending multiple requests
to the same destination. Upon receipt of the response containing the
History-Info entries, the Request URIs for the History-Info entries
tagged with "mp" header field parameter are extracted. Those
Request-URIs can be compared to other URIs (if any) that might be
attempted in order to establish the session with Bob. Thus, avoiding
another INVITE to Bob's home phone. Without this mechanism, Alice
Barnes, et al. Expires October 29, 2011 [Page 38]
Internet-Draft History-Info April 2011
might well attempt to reach Bob at his office phone, which would then
retarget the request to Bob's home phone. When that attempt failed,
then Alice might attempt to reach Bob directly at his home phone,
unknowingly for a third time.
Alice example.com Bob Office Home
| | | | |
| INVITE F1 | | | |
|----------->| INVITE F2 | | |
| |----------------->| | |
| 100 Trying F3 | | |
|<-----------| 302 Move Temporarily F4 | |
| |<-----------------| | |
| | ACK F5 | | |
| |----------------->| | |
| | INVITE F6 | |
| |-------------------------->| |
| | 180 Ringing F7 | |
| |<--------------------------| |
| 180 Ringing F8 | |
|<-----------| retransmit INVITE | |
| |-------------------------->| |
| | ( timeout ) | |
| | INVITE F9 |
| |----------------------------------->|
| | 100 Trying F10 |
| |<-----------------------------------|
| | 486 Busy Here F11 |
| |<-----------------------------------|
| 486 Busy Here F12 |
|<-----------| ACK F13 |
| |----------------------------------->|
| ACK F14 | |
|----------->| |
Barnes, et al. Expires October 29, 2011 [Page 39]
Internet-Draft History-Info April 2011
Message Details
F1 INVITE alice -> example.com
INVITE sip:alice@example.com SIP/2.0
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F2 INVITE example.com -> Bob
INVITE sip:bob@192.0.2.4 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4>;index=1.1;rc=1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F3 100 Trying example.com -> alice
SIP/2.0 100 Trying
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com
CSeq: 1 INVITE
Content-Length: 0
Barnes, et al. Expires October 29, 2011 [Page 40]
Internet-Draft History-Info April 2011
F4 302 Moved Temporarily Bob -> example.com
SIP/2.0 302 Moved Temporarily
Via: SIP/2.0/TCP proxy.example.com:5060
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>;tag=3
Call-Id: 12345600@example.com
CSeq: 1 INVITE
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4>;index=1.1;rc=1
Contact: <sip:office@example.com>;mp=1
Content-Length: 0
F5 ACK 192.0.2.4 -> Bob
ACK sip:home@example.com SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com
CSeq: 1 ACK
Content-Length: 0
F6 INVITE example.com -> office
INVITE sip:office@192.0.2.3.com SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=2
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5>;index=1.2.1
CSeq: 1 INVITE
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
Barnes, et al. Expires October 29, 2011 [Page 41]
Internet-Draft History-Info April 2011
<!-- SDP Not Shown -->
F7 180 Ringing office -> example.com
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP proxy.example.com:5060;branch=2
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>;tag=5
Supported: histinfo
Call-ID: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5>;index=1.2.1
CSeq: 1 INVITE
Content-Length: 0
F8 180 Ringing example.com -> alice
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP example.com:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5>;index=1.2.1
CSeq: 1 INVITE
Content-Length: 0
Barnes, et al. Expires October 29, 2011 [Page 42]
Internet-Draft History-Info April 2011
F9 INVITE example.com -> home
INVITE sip:home@192.0.2.6 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=3
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5?Reason=SIP%3Bcause%3D408>;\
index=1.2.1>;index=1.2.1
History-Info: <sip:home@example.com>;index=1.3;mp=1
History-Info: <sip:home@192.0.2.6>;index=1.3.1
CSeq: 1 INVITE
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F10 100 Trying home -> example.com
SIP/2.0 100 Trying
Via: SIP/2.0/TCP proxy.example.com:5060;branch=3
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com
CSeq: 1 INVITE
Content-Length: 0
Barnes, et al. Expires October 29, 2011 [Page 43]
Internet-Draft History-Info April 2011
F11 486 Busy Here home -> example.com
SIP/2.0 486 Busy Here
Via: SIP/2.0/TCP proxy.example.com:5060;branch=3
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5?Reason=SIP%3Bcause%3D408>;\
index=1.2.1>;index=1.2.1
History-Info: <sip:home@example.com>;index=1.3;mp=1
History-Info: <sip:home@192.0.2.6>;index=1.3.1
CSeq: 1 INVITE
Content-Length: 0
F12 486 Busy Here example.com -> alice
SIP/2.0 486 Busy Here
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5?Reason=SIP%3Bcause%3D408>;\
index=1.2.1>;index=1.2.1
History-Info: <sip:home@example.com>;index=1.3;mp=1
History-Info: <sip:home@192.0.2.6>;index=1.3.1
CSeq: 1 INVITE
Content-Length: 0
Barnes, et al. Expires October 29, 2011 [Page 44]
Internet-Draft History-Info April 2011
F13 ACK example.com -> home
ACK sip:home@example.com SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com
CSeq: 1 ACK
Content-Length: 0
F14 ACK alice -> example.com
ACK sip:bob@example.com SIP/2.0
Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com
Route: <sip:proxy.example.com;lr>
CSeq: 1 ACK
Content-Length: 0
B.2. History-Info with Privacy Header Field
This example provides a basic call scenario without forking. Alice
has indicated that she wants Privacy associated with the History-Info
header field entries. In addition, sip:biloxi.example.com adds
Privacy header fields indicating that the History-info header field
information is anonymized outside the biloxi.example.com domain.
Note, that if the atlanta.example.com proxy had added privacy header
fields to all its hi-entries, then all the hi-entries in the response
would be anonymous.
Barnes, et al. Expires October 29, 2011 [Page 45]
Internet-Draft History-Info April 2011
Alice atlanta.example.com biloxi.example.com Bob
| | | |
| INVITE sip:bob@biloxi.example.com;p=x |
|--------------->| | |
| Supported: histinfo | |
| Privacy: History | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| | | |
| | INVITE sip:bob@biloxi.example.com;p=x
| |--------------->| |
| History-Info: <sip:anonymous@anonymous.invalid>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| | | |
| | | INVITE sip:bob@192.0.2.3
| | |--------------->|
| History-Info: <sip:anonymous@anonymous.invalid>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3?Privacy=history>;index=1.1.1;rc=1.1
| | | |
| | | 200 |
| | |<---------------|
| History-Info: <sip:anonymous@anonymous.invalid>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3?Privacy=history>;index=1.1.1;rc=1.1
| | | |
| | 200 | |
| |<---------------| |
| History-Info: <sip:anonymous@anonymous.invalid>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc=1.1
| | | |
| 200 | | |
|<---------------| | |
| History-Info: <sip:anonymous@anonymous.invalid>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc=1.1
| | | |
| ACK | | |
|--------------->| ACK | |
| |--------------->| ACK |
| | |--------------->|
Figure 2: Example with Privacy Header Fields
Barnes, et al. Expires October 29, 2011 [Page 46]
Internet-Draft History-Info April 2011
B.3. Privacy for a Specific History-Info Entry
This example provides a basic call scenario similar to Appendix B.2,
however, due to local policy at sip:biloxi.example.com, only the
final hi-entry in the History-Info, which is Bob's local URI,
contains a privacy header field with a priv-value of "history", thus
providing Alice with some information about the history of the
request, but anonymizing Bob's local URI.
Barnes, et al. Expires October 29, 2011 [Page 47]
Internet-Draft History-Info April 2011
Alice atlanta.example.com biloxi.example.com Bob
| | | |
| INVITE sip:bob@biloxi.example.com;p=x |
|--------------->| | |
| Supported: histinfo | |
| | | |
| | INVITE sip:bob@biloxi.example.com;p=x
| |--------------->| |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| | | |
| | | INVITE sip:bob@192.0.2.3
| | |--------------->|
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc=1.1
| | | |
| | | 200 |
| | |<---------------|
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3?Privacy=history>;index=1.1.1;rc=1.1
| | | |
| | 200 | |
| |<---------------| |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc=1.1
| | | |
| 200 | | |
|<---------------| | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:anonymous@anynymous.invalid>;index=1.1.1;rc=1.1
| | | |
| ACK | | |
|--------------->| ACK | |
| |--------------->| ACK |
| | |--------------->|
Figure 3: Example with Privacy Header Field for Specific URI
Barnes, et al. Expires October 29, 2011 [Page 48]
Internet-Draft History-Info April 2011
Authors' Addresses
Mary Barnes
Polycom
TX
US
Email: mary.ietf.barnes@gmail.com
Francois Audet
Skype
Email: francois.audet@skype.net
Shida Schubert
NTT
Email: shida@agnada.com
Hans Erik van Elburg
Detecon International Gmbh
Oberkasseler str. 2
Bonn,
Germany
Email: ietf.hanserik@gmail.com
Christer Holmberg
Ericsson
Hirsalantie 11, Jorvas
Finland
Email: christer.holmberg@ericsson.com
Barnes, et al. Expires October 29, 2011 [Page 49]
