Network Working Group M. Barnes
Internet-Draft Polycom
Obsoletes: 4244 (if approved) F. Audet
Intended status: Standards Track Skype
Expires: April 29, 2011 S. Schubert
NTT
J. van Elburg
Detecon International Gmbh
C. Holmberg
Ericsson
October 26, 2010
An Extension to the Session Initiation Protocol (SIP) for Request
History Information
draft-ietf-sipcore-rfc4244bis-02.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 call arrives at a specific
application or user. This document defines an optional SIP header,
History-Info, for capturing the history information in requests. SIP
header field parameters are defined to tag the method by which the
target of a request is determined. In addition, this document
defines a value for the Privacy header specific to the History-Info
header.
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 April 29, 2011.
Copyright Notice
Barnes, et al. Expires April 29, 2011 [Page 1]
Internet-Draft History-Info October 2010
Copyright (c) 2010 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 April 29, 2011 [Page 2]
Internet-Draft History-Info October 2010
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Overview of Operation . . . . . . . . . . . . . . . . . . . . 6
5. General User Agent Behavior . . . . . . . . . . . . . . . . . 10
5.1. User Agent Client (UAC) Behavior . . . . . . . . . . . . . 10
5.2. User Agent Server (UAS) Behavior . . . . . . . . . . . . . 10
5.2.1. Processing of Requests with History-Info . . . . . . . 10
5.2.2. Generation of Responses with History-Info . . . . . . 11
5.3. Redirect Server Behavior . . . . . . . . . . . . . . . . . 11
6. Proxy Behavior . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Adding the History-Info Header to Requests . . . . . . . . 12
6.1.1. Initial Request . . . . . . . . . . . . . . . . . . . 12
6.1.2. Re-sending based on failure response . . . . . . . . . 13
6.1.3. Re-sending based on redirection response . . . . . . . 14
6.2. Sending History-Info in Responses . . . . . . . . . . . . 14
7. The History-Info header field . . . . . . . . . . . . . . . . 14
7.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 14
7.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 17
7.3.1. Privacy in the History-Info Header . . . . . . . . . . 17
7.3.2. Reason in the History-Info Header . . . . . . . . . . 18
7.3.3. Indexing in the History-Info Header . . . . . . . . . 18
7.3.4. Request Target in the History-Info Header . . . . . . 20
8. Application Considerations . . . . . . . . . . . . . . . . . . 21
9. Security Considerations . . . . . . . . . . . . . . . . . . . 22
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
10.1. Registration of New SIP History-Info Header . . . . . . . 23
10.2. Registration of "history" for SIP Privacy Header . . . . . 24
10.3. Registration of Header Field Parameters . . . . . . . . . 24
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
12. Changes from RFC 4244 . . . . . . . . . . . . . . . . . . . . 25
12.1. Backwards compatibility . . . . . . . . . . . . . . . . . 26
13. Changes since last Version . . . . . . . . . . . . . . . . . . 27
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
14.1. Normative References . . . . . . . . . . . . . . . . . . . 32
14.2. Informative References . . . . . . . . . . . . . . . . . . 32
Appendix A. Request History Requirements . . . . . . . . . . . . 33
A.1. Security Requirements . . . . . . . . . . . . . . . . . . 34
A.2. Privacy Requirements . . . . . . . . . . . . . . . . . . . 35
Appendix B. Example call flows . . . . . . . . . . . . . . . . . 35
B.1. Sequentially Forking (History-Info in Response) . . . . . 35
B.2. History-Info with Privacy Header . . . . . . . . . . . . . 43
B.3. Privacy Header for a Specific History-Info Entry . . . . . 45
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 46
Barnes, et al. Expires April 29, 2011 [Page 3]
Internet-Draft History-Info October 2010
1. Introduction
Many services that SIP is anticipated to support require the ability
to determine why and how the call 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 calls to be routed to
chosen applications, there is a need for a standard mechanism within
SIP for communicating the retargeting history of such a request.
This "request history" information allows the receiving application
to determine hints about how and why the call arrived at the
application/user.
This document defines a SIP header, 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 to tag the method by which the
target of a request is determined. In addition, this document
defines a value for the Privacy header specific to the History-Info
header.
The History-Info header 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 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 April 29, 2011 [Page 4]
Internet-Draft History-Info October 2010
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 calls 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 call is retargeted to process the call 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 call to exchange additional information relating to
how and why the call 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.
o Capturing aliases and Globally Routable User Agent URIs (GRUUs)
[RFC5627], which can be overwritten by a home proxy upon receipt
Barnes, et al. Expires April 29, 2011 [Page 5]
Internet-Draft History-Info October 2010
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 of Operation
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
(CAPABILITY-req, see Appendix A). The solution is to capture the
Request-URIs as a request is retargeted, in a SIP header: History-
Info (CONTENT-req, see Appendix A). 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 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.) (REQUEST-VALIDITY-
req, see Appendix A) and any provisional or final responses to these
requests (ISSUER-req, see Appendix A).
The following information is carried in the History-Info header as
detailed in Section 7.1:
o Targeted-to-URI: The targeted-to-URI entry captures the Request-
URI for the specific request as it is forwarded.
o Index: The index reflects the chronological order of the
information, indexed to also reflect the forking and nesting of
requests.
o Reason: Reason describes why an entry was retargeted.
o Privacy: Privacy is used to request that an entry be anonymized if
the request is retargeted to a domain for which the retargeting
entity is not responsible.
o Target: A parameter indicating whether the Targeted-to-URI is a
registered contact ("rc") for another user mapped ("mp") from the
Request-URI in the incoming request that was retargeted. The
index of the History-Info entry for the URI that was retargeted is
included in each of these parameters. Note that there may be
Barnes, et al. Expires April 29, 2011 [Page 6]
Internet-Draft History-Info October 2010
other reasons a request is retargeted such as normal routing and
forwarding, strict routing, etc., thus not all history-info
entries have a target header field parameter. The "rc" and "mp"
scenarios are what is anticipated to be most useful to end
applications/users.
In addition, this specification defines a value for the Privacy
header, "history", that applies to all the History-Info header
entries in a Request or to a specific History-Info header entry as
described above. Further detailed is provided in Section 7.3.1.
The History-Info header 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 or REFER also propagates any
History-Info header from the initial Request in the new request.
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 home proxy (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
locating the last hi-entry with an "rc" header field parameter. This
"rc" parameter contains the index of the hi-entry containing the lost
target information - i.e., the sip:bob@biloxi.example.com 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 and
the headers in the URI are not shown properly formatted for escaping.
Refer to Section 7.2 for the proper formatting. Additional detailed
scenarios are available in the Appendix B.
Barnes, et al. Expires April 29, 2011 [Page 7]
Internet-Draft History-Info October 2010
Note: This example uses loose routing procedures.
Barnes, et al. Expires April 29, 2011 [Page 8]
Internet-Draft History-Info October 2010
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 April 29, 2011 [Page 9]
Internet-Draft History-Info October 2010
Figure 1: Basic Call
5. General User Agent Behavior
This section describes the processing specific to UAs for the
History-Info header.
5.1. User Agent Client (UAC) Behavior
The UAC MUST include the "histinfo" option tag in the Supported
header in any new or out-of-dialog request for which the UAC would
like the History-Info header in the response. In addition, the UAC
SHOULD add a History-Info header, using the Request-URI of the
request as the hi-targeted-to-uri, in which case the index MUST be
set to a value of 1 in the hi-entry. As a result, intermediaries and
the UAS at least know the original Request-URI, and if the Request-
URI was modified by a previous hop. In the case of a B2BUA
implementation, a UAC MAY add the hi-entries received in the incoming
request at the UAS to the subsequent outgoing request.
A UAC that does not want an hi-entry added due to privacy
considerations MUST include a Privacy header with a priv-value(s) of
"header" or "history". A UAC that wants to ensure that privacy not
be applied to its identity MUST include a Privacy header with a priv-
value of "none".
In the case where a UAC receives a 3xx response with a Contact header
and sends a new request in response to it, the UAC MAY include in the
outgoing request the previous hi-entry(s) received in the response.
In this case, the reason header MUST be associated with the hi-
targeted-to-uri in the previous (last) hi-entry, as described in
Section 7.3.2. A new hi-entry MUST then be added for the URI from
the Contact header (which becomes the new Request-URI). An index
MUST be added to the hi-entry. The value for the index is determined
following the rules for "Retargeting based upon a Response" as
prescribed in Section 7.3.3. If the Contact header contained any of
the header parameter fields defined in this specification, the UAC
MUST include the header parameter field as a header parameter field
associated with the current hi-entry as described in Section 7.3.4.
5.2. User Agent Server (UAS) Behavior
5.2.1. Processing of Requests with History-Info
Once the request terminates at the UAS, the UAS evaluates the
History-Info header. The last hi-entry reflects the most recent
target and MUST contain the Request-URI for the received request,
Barnes, et al. Expires April 29, 2011 [Page 10]
Internet-Draft History-Info October 2010
unless the previous entity that forwarded the request does not
support the History-Info header. If the Request-URI of the incoming
request does not match the last hi-entry (e.g., the last proxy does
not support History-Info), the UAS MUST insert an hi-entry. The UAS
MUST set the hi-targeted-to-uri based to the value of Request-URI in
the incoming request. If privacy is required, a privacy header with
a value of "history" MUST be added to the hi-entry. The UAS MUST
include an hi-index attribute as described in Section 7.3.3. The UAS
MUST NOT include a hi-target attribute, since the UAS has no way to
know the mechanism by which the Request-URI was determined. The
addition of the missing hi-entry ensures that the most complete
information can be provided in the response and provides consistency
in the information presented to applications. The information can
also be useful for implementations with B2BUAs that include the
History-Info, received in the incoming request, in the outgoing
request.
Prior to any application usage of the information, the validity MUST
be ascertained. If gaps are detected, this MUST NOT be treated as an
error since gaps are possible if the request is forwarded through
intermediate entities that do not support the History-Info header.
The interpretation of the information in the History-Info header by a
UAS in a request depends upon the specific applications supported by
the UAS; an application might need to provide special handling in
some cases where there are gaps. Application considerations and
guidelines are provided in section 7.
5.2.2. Generation of Responses with History-Info
If the "histinfo" option tag is received in a request, the UAS MUST
include any History-Info received in the request in the subsequent
response. If privacy is required, entries MUST be anonymized as
described in Section 7.3.1. The UAS MUST follow the rules for a
redirect server per Section 5.3 in generating a 3xx response.
The processing of History-Info in responses follows the methodology
described in Section 16.7 of [RFC3261], with the processing of
History-Info headers adding an additional step, just before Step 9,
"Forwarding the Response".
5.3. Redirect Server Behavior
A redirect server MUST include the History-Info headers received in
the request in the 3XX response that it sends. A redirect server
MUST add any new History-Info entries in cases of retargeting (both
internal and to other SIP entities) in the same manner as prescribed
for a proxy Section 6. In generating the Contact header in the 3xx
response, the redirect server MUST add the appropriate target header
Barnes, et al. Expires April 29, 2011 [Page 11]
Internet-Draft History-Info October 2010
field parameter to each Contact header as described in Section 7.3.4.
6. Proxy Behavior
This section describes the procedures for proxies and other SIP
intermediaries for adding History-Info headers when requests are
retargeted.
6.1. Adding the History-Info Header to Requests
This section describes the process of adding the History-Info header
to requests for the following cases:
o Forwarding of initial request (see Section 6.1.1)
o Resending based on failure response (see Section 6.1.2)
o Resending based on redirection response (see Section 6.1.3)
Retargeting is an iterative process, i.e., a proxy may redirect
"internally " more than one time. 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
that new AOR. In these cases, a proxy MUST add multiple hi-entry
fields. For example, a proxy that retargets bob@example.com to
office@example.com and then to office@192.0.2.5 adds hi-entries for
both office@example.com and office@192.0.2.5, in order to provide a
logical description of the retargeting process internal to the proxy.
A Reason MAY be associated with the hi-targeted-to-uri that has been
retargeted as shown in the example in Appendix B.1.
6.1.1. Initial Request
Upon receipt of an initial request for a dialog, or a standalone
request, a proxy forwarding the request MUST perform the following
steps. Note that those steps below do not apply if the request is
being re-sent as a result of failure (i.e., timeout, reception of an
error response).
Step 1: Adding Entries on Behalf of Previous Hops
If an incoming request does not already have a History-Info header
field (e.g., the UAC does not include any History-Info header and
no proxies in between support History-Info), or if the Request-URI
of the incoming request does not match the last hi-entry (e.g.,
the last proxy does not support History-Info), the proxy MUST
insert an hi-entry. The proxy MUST set the hi-targeted-to-uri
Barnes, et al. Expires April 29, 2011 [Page 12]
Internet-Draft History-Info October 2010
based to the value of Request-URI in the incoming request, unless
privacy is required. If privacy is required, the procedures of
Section 7.3.1 MUST be used. The proxy MUST NOT include a hi-
target attribute. The proxy MUST include an hi-index attribute
with a value of "1", as described in Section 7.3.3.
Step 2: Generating New Entries for Each Outgoing Request
The proxy then proceeds to request forwarding as per 16.6/
[RFC3261]. The proxy MUST add a separate hi-entry in each
separate outgoing request for each of the current (outgoing)
targets in the target set. The proxy MUST set the hi-targeted-to-
uri in those separate hi-entry(s) to the value of the Request-URI
of the current (outgoing) request, unless privacy is required. If
privacy is required, the procedures of Section 7.3.1 MUST be used.
The proxy MUST include an hi-index for each of the separate hi-
entry(s) as described in Section 7.3.3. The proxy MUST include
the appropriate hi-target header field parameter for each of the
separate entry(s) as described in Section 7.3.4, if applicable.
6.1.2. Re-sending based on failure response
When re-sending a request as a result of retargeting because of
failure (i.e., either reception of error responses or a timeout which
is considered to be an implicit 408 error response), the proxy MUST
perform the following steps:
Step 1: Including the Entries from Error Responses & Timeouts
The proxy MUST build the History-Info header field(s) sent in the
outgoing request using the aggregate information associated with
the received error responses(s) and timeout(s) for all the
branches that are generating failures, including the header
entries in the order indicated by the indexing (see
Section 7.3.3). If the received error response did not include
any History-Info header fields, the proxy MUST use the same
History-Info header fields that were sent in the outgoing request
that failed to build the outgoing request.
Step 2: Tagging the Last Entries
The proxy then examines the last hi-entry of the History-Info that
was just generated in Step 1 for each one of the branches that
generated failures or timeouts and MUST add a Reason header for
each one of those entries as per the procedures of Section 7.3.2.
Barnes, et al. Expires April 29, 2011 [Page 13]
Internet-Draft History-Info October 2010
Step 3: Generating New Entries for Each Outgoing Requests
Same as per Step 2 above for the normal forwarding case
Section 6.1.1.
6.1.3. Re-sending based on redirection response
When re-sending a request as a result of retargeting because of
redirection (i.e., receipt of a 3XX response), the following steps
apply:
Step 1: Including Previous Entries
The proxy MUST include the History-Info header fields that were
sent in the outgoing request that is being redirected.
Step 2: Tagging the Last Entry
The proxy then examines the last hi-entry of the History-Info that
was just generated in Step 1 and MUST add a Reason header this
entry as per the procedures of Section 7.3.2.
Step 3: Generating New Entries for Each Outgoing Requests
Same as per Step 2 for the normal forwarding case Section 6.1.1.
6.2. Sending History-Info in Responses
A proxy that receives a request with the "histinfo" option tag in the
Supported header, MUST forward captured History-Info in subsequent,
provisional, and final responses to the request sent by the ultimate
UAS (see Section 5.2). Any hi-entry containing a Privacy header with
a value of "history" MUST be anonymized prior to a proxy sending a
response with that hi-entry.
The processing of History-Info in responses follows the methodology
described in Section 16.7 of [RFC3261], with the processing of
History-Info headers adding an additional step, just before Step 9,
"Forwarding the Response".
7. The History-Info header field
7.1. Definition
History-Info is a header field as defined by [RFC3261]. It may
appear in any initial request for a dialog, standalone request or
responses associated with these requests. For example, History-Info
Barnes, et al. Expires April 29, 2011 [Page 14]
Internet-Draft History-Info October 2010
may appear in INVITE, REGISTER, MESSAGE, REFER, OPTIONS, SUBSCRIBE,
and PUBLISH and any valid responses, plus NOTIFY requests that
initiate a dialog.
The History-Info header carries the following information when the
header is included in a request or response:
o Targeted-to-URI (hi-targeted-to-uri): A mandatory parameter for
capturing the Request-URI for the specific request as it is
forwarded.
o Index (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 6.1), including the index and securing the
header, the ordering of the History-Info headers in the request is
assured (SEC-req-2, see Appendix A.1). 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 Reason: An optional parameter for History-Info, reflected in the
History-Info header by including the Reason Header [RFC3326]
escaped in the hi-targeted-to-uri. A reason is included for the
hi-targeted-to-uri that was retargeted as opposed to the hi-
targeted-to-uri to which it was retargeted.
o Privacy: An optional parameter for History-Info, reflected in the
History-Info header field values by including the Privacy Header
[RFC3323] escaped in the hi- targeted-to-uri or by adding the
Privacy header 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 escaped in the
hi-targeted-to-uri means that a specific hi-entry MUST be
anonymized.
o Target (hi-target): An optional parameter for the History-Info and
Contact headers. The hi-target is added for a hi-entry when it is
first added in a History-Info header field, and only one value is
permitted. Upon receipt of a request or response containing the
History-Info header, a UA can determine the mechanism by which the
target was determined. The following header field parameters are
defined for this parameter:
Barnes, et al. Expires April 29, 2011 [Page 15]
Internet-Draft History-Info October 2010
"rc": The hi-targeted-to-URI is a contact for the Request-URI,
in the incoming request, that is bound to an AOR in an abstract
location service. 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 index of the hi-entry associated with the URI in the
incoming request.
"mp": The hi-targeted-to-URI represents a user other than the
user associated with the Request-URI in the incoming
requesting. This occurs when a request is to be statically or
dynamically retargeted to another user. The value of the "mp"
header field parameter is the index parameter for the hi-
targeted-to- 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 is defined 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 / hi-extension
index-val = 1*DIGIT *("." 1*DIGIT)
hi-index = "index" EQUAL index-val
hi-target = 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].
Note that since both the Reason and Privacy parameters are escaped in
the hi-targeted-to-uri, these fields will not be available in the
Barnes, et al. Expires April 29, 2011 [Page 16]
Internet-Draft History-Info October 2010
case that the hi-targeted-to-uri is a Tel-URI [RFC3966].
7.2. Examples
The following provides some examples of the History-Info header.
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
7.3. Procedures
The following sections define procedures for processing of the
parameters (and headers) associated with the History-Info header.
These procedures may be applicable to processing entities such as
Proxies, Redirect Servers or User Agents.
7.3.1. Privacy in the History-Info Header
The privacy requirements for this document are described in
Appendix A.2.
As with other SIP headers described in [RFC3323], the History-Info
header can inadvertently reveal information about the originator. A
value of "header" in the Privacy header is used to indicate that such
headers in the request be privacy protected when the request is
forwarded by the intermediary. A value of "history" in the Privacy
header indicates that the History-Info header should be privacy
protected. If there is a Privacy header in the request with a priv-
value of "header" or "history", then the initial hi-entry MUST be
anonymized and the header removed when the request leaves a domain
for which the SIP entity is responsible.
In addition, the History-Info header can reveal general routing and
diverting information within an intermediary, which the intermediary
may want to privacy protect. In this case, a value of "history" in
the Privacy header is used to indicate which History-Info header
entries added by a SIP entity are to be anonymized. The priv-value
of "history" MUST be in the privacy header escaped in the hi-
targeted-to-uri for each hi-entry, added by the SIP entity, as the
request is retargeted within the domain for which the SIP entity is
responsible. If a request is being retargeted to a URI associated
Barnes, et al. Expires April 29, 2011 [Page 17]
Internet-Draft History-Info October 2010
with a domain for which the SIP entity is not responsible, the
processing entity MUST anonymize the hi-entries with a priv-value of
"history" and MUST remove the Privacy header from the hi-entries
prior to forwarding, unless the processing entity knows a priori that
it can rely on a downstream processing entity to apply the requested
privacy. The mechanism for the latter functionality is outside the
scope of this specification.
Finally, the terminator of the request may not want to reveal the
final reached target to the originator. In this case, the terminator
uses the a value of "history" in the Privacy header in the last hi-
entry in the response. The SIP entity that forwards the response
MUST anonymize that hi-entry and remove the Privacy header.
7.3.2. Reason in the History-Info Header
For retargets that are the result of an explicit SIP response, a
Reason MUST be associated with the hi-targeted-to-uri. If the SIP
response does not include a Reason header (see [RFC3326]), the SIP
Response Code that triggered the retargeting MUST be included as the
Reason associated with the hi-targeted-to-uri that has been
retargeted. If the response contains a Reason header for a protocol
that is not SIP (e.g., Q.850), it MUST be captured as an additional
Reason associated with the hi-targeted-to-uri that has been
retargeted, along with the SIP Response Code. If the Reason header
is a SIP reason, then it MUST be used as the Reason associated with
the hi-targeted-to-uri rather than the SIP response code.
If a request has timed out (instead of being explicitly rejected), it
MUST be treated as if a 408 "Request Terminated" error response code
was received.
7.3.3. Indexing in the History-Info Header
In order to maintain ordering and accurately reflect the nesting and
retargeting of the request, an index MUST be included along with the
Targeted-to-URI being captured. Per the syntax in Section 7, the
index consists of a dot-delimited series of digits (e.g., 1.1.2).
Each dot reflects a hop or level of nesting; thus, the number of hops
is determined by the total number of dots. Within each level, the
integer reflects the number of peer entities to which the request has
been routed. 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 proxy adds an entry on behalf of the previous hop,
the index MUST be set to 1. For each level of indexing, the index
MUST start at 1. An increment of 1 MUST be used for advancing to a
Barnes, et al. Expires April 29, 2011 [Page 18]
Internet-Draft History-Info October 2010
new branch.
The basic rules for adding the index are summarized as follows:
1. Basic Forwarding: In the case of a request that is being
forwarded, the index is determined by adding another sub-level of
indexing since the depth/length of the branch is increasing. To
accomplish this, the processing entity MUST read the value from
the History-Info header in the received request and MUST add
another level of indexing by appending the dot delimiter followed
by an initial index for the new level of 1. For example, if the
index in the last History-Info header field in the received
request is 1.1, this proxy would initialize its index to 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
calculation of the index follows that prescribed for basic
forwarding.
3. Retargeting within a processing entity - subsequent instance: For
each subsequent retargeting of a request by the same processing
entity, another branch MUST be added. The index for each new
branch MUST be calculated by incrementing the last/lowest digit
at the current level, the index in the next request forwarded by
this same processing entity, following the example above, 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 index MUST be calculated
per rule 3. That is, the lowest/last digit of the index MUST be
incremented (i.e., a new branch is created), with the increment
of 1. For example, if the index in the History-Info header of
the sent request is 1.2 and the response to the request is a 302,
then the 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 index MUST be captured
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 for each individual fork, only the entry corresponding
to that fork is included (e.g., the entry for fork 1.1.1 is not
included in the request sent to fork 1.1.2, and vice-versa).
Barnes, et al. Expires April 29, 2011 [Page 19]
Internet-Draft History-Info October 2010
6. When a response is built and it represents the aggregate of
responses to multiple forks (e.g., multiple forks that fail), the
processing entity MUST build the subsequent response using the
aggregated information associated with each of the forks for
which there have been responses and MUST include the header
entries in the order indicated by the indexing. For example, if
a procesing entity received failure responses for forks 1.1.1 and
1.1.2, it would return both the 1.1.1 and 1.1.2 entries to the
entity that generated the hi-entry with index of 1. See
Appendix B.1 for an example. Note that in the case of parallel
forking where one fork is successful, only the forks for which
responses have been received at the time the proxy sends the
successful response are included in that response. Responses are
processed as described in Section 16.7 of [RFC3261] with the
aggregated History-Info entries processed similar to Step 7
"Aggregate Authentication Header Field Values".
7.3.4. Request Target in the History-Info Header
This specification defines two header field parameters, "rc" and
"mp", indicating two non-inclusive mechanisms by which a new target
for a request is determined. The specific parameter field to be
included in the History-Info header is determined as the targets are
added to the target set per the procedures of 16.5 or when the
Contact header field in a 3xx response is populated. Both parameters
contain an index whose value corresponds to the index in the hi-entry
containing the Request-URI that was retargeted.
The specific parameter field to be included in the History-Info
header is determined as follows:
o "rc": If the hi-targeted-to-URI was determined based on a contact
for the Request-URI being retargeted that is bound to an AOR in an
abstract location service, then the "rc" header field parameter
MUST be included in the hi-entry. The index of the "rc" parameter
MSUT be set to the hi-index containing the Request-URI being
retargeted.
o "mp": If the hi-targeted-to-URI was determined based on a mapping
to a user other than the user associated with the Request-URI
being retargeted, then the "mp" header field parameter MUST be
included in the hi-entry. The index of the "mp" parameter MUST be
set to the hi-index containing the Request-URI being retargeted.
Note that there are two scenarios by which the "mp" parameter can be
derived.
Barnes, et al. Expires April 29, 2011 [Page 20]
Internet-Draft History-Info October 2010
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 of the hi-entry's index,
that of the downstream request which received the 3xx response.
8. 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 information the entries MUST be evaluated to
determine gaps in indices. If gaps are detected, this MUST NOT be
treated as an error since gaps are possible if the request is
forwarded through intermediate entities that do not support the
History-Info header. The interpretation of the information in the
History-Info header depends upon the specific application; an
application might need to provide special handling in some cases
where there are gaps.
The following summarizes the categories of information that
applications may 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. Entry with the index that matches the value of the last entry
with a "rc" header parameter in the Request received by a UAS -
i.e., the Request URI associated with the destination of the
request was determined based on an AOR-to-contact binding in an
abstract location service.
3. Entry with the index that matches the value of the last entry
with a "mp" header parameter in the Request received by a UAS -
i.e., the last Request URI that was mapped to reach the
destination.
4. Entry with the index that matches the value of the first entry
with a "rc" header parameter in the Request received by a UAS.
Note, this would be the original AoR if all entries support the
History-Info header and there is absence of a "mp" header
parameter prior to the "rc" header parameter in the History-Info
header. However, there is no guarantee that all entities will
support History-Info, thus the first entry with an "rc" header
Barnes, et al. Expires April 29, 2011 [Page 21]
Internet-Draft History-Info October 2010
parameter within the domain associated with the target URI at the
destination is more likely to be useful.
5. Entry with the index that matches the value of the first entry
with a "mp" header parameter in the Request received by a UAS.
Note, this would be the original mapped URI if all entities
supported the History-Info header. However, there is no
guarantee that all entities will support History-Info, thus the
first entry with an "mp" header 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 entry who index matches the index of the first
History-Info entry with an hi-target value of "mp", may also display
other agents, reflected by other History-Info entries prior to
entries with hi-target values of "rc", 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 is optional, a service MUST
define default behavior for requests and responses not containing
History-Info headers. For example, an entity may receive only
partial History-Info entries or entries which are not tagged
appropriately with an hi-target parameter. 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.
9. 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
Barnes, et al. Expires April 29, 2011 [Page 22]
Internet-Draft History-Info October 2010
overall confidentiality of the History-Info headers (SEC-req-4) is
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.
With the level of security provided by TLS (SEC-req-3), the
information in the History-Info header can thus be evaluated to
determine if information has been removed by evaluating the indices
for gaps (SEC-req-1, SEC-req-2). It would be up to the application
to define whether it can make use of the information in the case of
missing entries.
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.
10. IANA Considerations
This document requires several IANA registrations detailed in the
following sections.
This document updates [RFC4244] but uses the same SIP header field
name and option tag. The IANA registry needs to update the
references to [RFC4244] with [RFCXXXX].
10.1. Registration of New SIP History-Info Header
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 April 29, 2011 [Page 23]
Internet-Draft History-Info October 2010
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 RFC XXXX with the RFC number of
this specification.
10.2. Registration of "history" for SIP Privacy Header
This document defines a priv-value for the SIP Privacy header:
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:
Name Description Registrant Reference
---- ----------- ---------- ---------
history Privacy requested for Mary Barnes [RFCXXXX]
History-Info header(s) mary.barnes@polycom.com
Note to RFC Editor: Please replace RFC XXXX with the RFC number of
this specification.
10.3. 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]
Note to RFC Editor: Please replace RFC XXXX with the RFC number of
Barnes, et al. Expires April 29, 2011 [Page 24]
Internet-Draft History-Info October 2010
this specification.
11. 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.
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.
12. 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 April 29, 2011 [Page 25]
Internet-Draft History-Info October 2010
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 parameters to capture the specific method by which a
target is determined to facilitate processing by users of the
History-Info header entries. A specific header parameter is
captured for each of the target URIs as the target set is
determined (per section 16.5 of [RFC3261]). The header parameter
is used in both the History-Info and the Contact headers.
2. Rather than recommending that entries be removed in the case of
certain values of the privacy header, recommend that 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 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. 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.
12.1. Backwards compatibility
This specification is backwards compatible since [RFC4244] allows for
the addition of new optional parameters. This specification adds an
Barnes, et al. Expires April 29, 2011 [Page 26]
Internet-Draft History-Info October 2010
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.
13. Changes since last Version
NOTE TO THE RFC-Editor: Please remove this section prior to
publication as an RFC.
Changes from 01 to 02:
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]
Barnes, et al. Expires April 29, 2011 [Page 27]
Internet-Draft History-Info October 2010
10. Updated/clarified privacy handling. [Issue: 16]
11. Updated Redirect Server section to allow adding History-Info
headers. [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:
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.
3. Updated the Application considerations section:
* 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.
Barnes, et al. Expires April 29, 2011 [Page 28]
Internet-Draft History-Info October 2010
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
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 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 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.
Barnes, et al. Expires April 29, 2011 [Page 29]
Internet-Draft History-Info October 2010
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-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.
Barnes, et al. Expires April 29, 2011 [Page 30]
Internet-Draft History-Info October 2010
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
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.
Barnes, et al. Expires April 29, 2011 [Page 31]
Internet-Draft History-Info October 2010
6. Fixed ABNF per RFC4244 errata "dot" -> "." and added new
parameter.
14. References
14.1. 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.
[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.
14.2. 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.
[RFC3969] Camarillo, G., "The Internet Assigned Number Authority
(IANA) Uniform Resource Identifier (URI) Parameter
Registry for the Session Initiation Protocol (SIP)",
Barnes, et al. Expires April 29, 2011 [Page 32]
Internet-Draft History-Info October 2010
BCP 99, RFC 3969, December 2004.
[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.
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.
Barnes, et al. Expires April 29, 2011 [Page 33]
Internet-Draft History-Info October 2010
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
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 entry
either by adding an additional 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.
Barnes, et al. Expires April 29, 2011 [Page 34]
Internet-Draft History-Info October 2010
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.
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 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 entry
just prior to the firt entry tagged with an hi-target value of "rc".
In this example, the Office and Home are not the same AOR as
Barnes, et al. Expires April 29, 2011 [Page 35]
Internet-Draft History-Info October 2010
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 "mp" 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" 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 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.
Barnes, et al. Expires April 29, 2011 [Page 36]
Internet-Draft History-Info October 2010
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 | |
|----------->| |
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 -->
Barnes, et al. Expires April 29, 2011 [Page 37]
Internet-Draft History-Info October 2010
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
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
Barnes, et al. Expires April 29, 2011 [Page 38]
Internet-Draft History-Info October 2010
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;cause=302>;\
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>
<!-- SDP Not Shown -->
Barnes, et al. Expires April 29, 2011 [Page 39]
Internet-Draft History-Info October 2010
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;cause=302>;\
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;cause=302>;\
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 April 29, 2011 [Page 40]
Internet-Draft History-Info October 2010
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;cause=302>;\
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;cause=480>;\
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 April 29, 2011 [Page 41]
Internet-Draft History-Info October 2010
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;cause=302>;\
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;cause=480>;\
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;cause=302>;\
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;cause=480>;\
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 April 29, 2011 [Page 42]
Internet-Draft History-Info October 2010
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
This example provides a basic call scenario without forking. Alice
has indicated that she wants Privacy associated with her History-Info
entry and sip:biloxi.example.com adds Privacy headers indicating that
the History-Info header information is anonymized outside the
biloxi.example.com domain. Note, that if the atlanta.example.com
proxy had added privacy headers to all its hi-entries, then all the
hi-entries in the response would be anonymous.
Barnes, et al. Expires April 29, 2011 [Page 43]
Internet-Draft History-Info October 2010
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
Barnes, et al. Expires April 29, 2011 [Page 44]
Internet-Draft History-Info October 2010
B.3. Privacy Header 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 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 April 29, 2011 [Page 45]
Internet-Draft History-Info October 2010
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 for Specific URI
Barnes, et al. Expires April 29, 2011 [Page 46]
Internet-Draft History-Info October 2010
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 April 29, 2011 [Page 47]
