Internet Draft M. Barnes
Document: draft-ietf-sip-history-info-00.txt Editor
Category: Standards Track Nortel Networks
Expires: December, 2003 June 2003
An Extension to the Session Initiation Protocol for Request History
Information
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This draft defines a standard mechanism for capturing the history
information associated with a 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 draft defines
a new optional SIP header, History-Info, for capturing the history
information in requests. A new option tag, HistInfo, to be included
in the Supported header is defined to allow UAs to indicate whether
the HistInfo should be returned in responses to a request which has
captured the history information.
Table of Contents
1 Request History Information Description.........................3
1.1 Optionality of History-Info................................4
1.2 Securing History-Info......................................4
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1.3 Ensuring the Privacy of History-Info.......................5
2 Request History Information Protocol Details....................5
2.1 Protocol Structure of History-Info.........................5
2.2 Protocol Examples..........................................6
2.3 Protocol usage.............................................6
2.4 Security for History-Info..................................9
2.5 Example Applications using History-Info...................10
3. Security Considerations.......................................11
References.......................................................12
Appendix A Forking Scenarios....................................14
A.1 Sequentially forking (Hist-Info in Response)..............14
A.2 Sequential Forking (with Success).........................15
Appendix B Voicemail............................................16
Appendix C Automatic Call Distribution Example..................21
Full Copyright Statement.........................................22
Overview
This document provides the solution for the Request History
requirements as defined in [1].
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.
This functionality provides a standard mechanism for capturing the
request history information to enable a wide variety of services for
networks and end users, without prescribing the operation of those
services.
Section 1 provides an overall description of the solution, providing
references to the appropriate requirements met by each aspect of the
solution.
Section 2 provides the details of the additions to the SIP protocol,
which are required to capture the Request History information. An
example use of the request history information is included in Section
2, with additional scenarios included in the Appendix. It is
anticipated that these would be moved and progressed in the Service
examples draft [2] or individual informational drafts describing
these specific services, since History-Info is just one of the
building blocks for implementing these services. Individual drafts
would be particularly useful for documenting services for which there
are multiple solutions, since the use of the request history
information isn't prescriptive.
Conventions used in this document
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [7].
In order to provide a cross reference of the solution description to
the requirements defined in [1] without reiterating the entirety of
the requirements in this document, the requirements are referenced as
[REQNAME-req] following the text or paragraph which explicitly
satisfies the requirement.
Definitions
The following terminology is used in this document:
Retarget (as defined in [1]): The process of a Proxy Server/UAC
changing a URI in a request and thus changing the target of the
request.
Retargeted: past of Retarget.
Retargeted-from-URI: The URI or address from which the request was
retargeted.
Retargeted-to-URI: The new URI or address to which the request is in
the process of being retargeted.
1 Request History Information Description
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]. The solution for the capture of the Request
History Information defines a new header for SIP messages: History-
Info [CONTENT-req].
The Request History Information can appear in any request not
associated with an established dialog, which includes INVITE,
REGISTER, MESSAGE and OPTIONS [REQUEST-VALIDITY-req] and any valid
response to these requests.[ISSUER-req]
Request History Information is captured when a request is retargeted.
In some scenarios, it might be possible for more than one instance of
retargeting to occur within the same Proxy. A proxy SHOULD also
generate request history information for the 'internal retargeting'.
An entity (UA or proxy) retargeting in response to a redirect or
REFER SHOULD include any Request History information from the
redirect/REFER in the new request [GENERATION-req, FORWARDS-req].
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1.1 Optionality of History-Info
The Request History Information is optional in that neither UAs nor
Proxies are required to support it. The requirement for Request
History information to be returned in Responses is indicated using a
new Supported header: HistInfo [BACKWARDS-req]. In addition, local
policy can define whether or not the information is captured by the
retargeting entity for any request, or a specific Request-URI, being
retargeted. In many instances, it is likely that this could restrict
the applicability of services which make use of the Request History
Information to be limited to retargeting within domain(s) controlled
by the same local policy, or between domain(s) which negotiate
policies with other domains to ensure support of the given policy, or
services for which "complete" History Information isn't required to
provide the service. [OPTIONALITY-req] Thus, it is highly
recommended that all applications making use of the request history
information clearly define the impact of the information not being
available and specify the processing of such a request.
1.2 Securing History-Info
This draft defines a new header for SIP. Since, the Request History
information is being inserted by an entity as it targets a Request,
the resulting security requirements introduce a slightly different
problem than the basic SIP header or Identity problem. For History-
Info, the general requirement is to secure information that is
inserted by a proxy. It is primarily the captured Request-URIs that
are the security concern, since they can reflect some aspect of a
user's identity and service routing. Thus, the primary objective of
the security solution is to ensure that the information being
captured is protected from being accessed or manipulated by non-
authorized entities, with the fundamental assumption that retargeting
entities are implicitly authorized. The draft does suggest the use
of a secure transport mechanism such as TLS to ensure the overall
confidentiality of the History-Info[SEC-req-4]. However, the
complete security solution for History-Info depends upon a general
solution for protecting the captured information, which is addressed
in a separate solution draft [5]. Details of the use of this proposed
mechanism to satisfy the security requirements are provided in
section 2.4.
The security associated with the Request History Information is
optional and depends upon local policy and the impact on specific
applications of having the information compromised. Since, the
Request History Information itself is also optional and it has been
recommended that applications document the impact of the information
not being available, it is also suggested that the impact of not
supporting the security recommendations also be documented to ensure
that it is sufficiently addressed by the application.
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1.3 Ensuring the Privacy of History-Info
In order to satisfy the requirements of ensuring that the privacy
associated with a retargeted request is maintained by the retargeting
entity [PRIV-req-1] and by the receiving entity [PRIV-req-2], the
retargeting entity must determine if there is any privacy associated
with a request being retargeted. In some scenarios, the Privacy
header would indicate whether the headers in a message should be
privacy protected. However, the basic assumption is that local policy
would be used to determine whether a specific request should have its
privacy maintained and whether maintaining that privacy means that a
specific request URI would NOT be captured or that it would be
appropriately Privacy protected if it were captured. The proposal for
ensuring that the privacy is protected is to recommend the use of a
Privacy Service as defined by [6] for headers.
It is recognized that meeting the privacy requirements can impact the
functionality of this solution by overriding the request to generate
the information. As with the optionality and security requirements,
applications making use of History-Info should address any impact
this may have.
2 Request History Information Protocol Details
This section contains the details and usage of the proposed new SIP
protocol elements. It also discusses the security aspects of the
solution and provides some examples.
2.1 Protocol Structure of History-Info
History-Info is a header field as defined by [4]. It can appear in
any request not associated with an established dialog, which includes
INVITE, REGISTER, MESSAGE and OPTIONS and any valid response to these
requests.
It carries the following information:
o Targeted-to-URI: the Request URI captured as the Request is
targeted. By capturing a copy of the Request URI in the initial
request, the Retargeted-from-URI is already captured when a
request is retargeted and the Retargeted-to-URI is being
captured.
o Reason: An optional parameter for History-info. The reason for
the retargeting is captured by including the Reason Header [3]
as part of the captured Request URI.
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o Index: An optional parameter for History-Info reflecting the
chronological order of the information, indexed to also reflect
the forking and nesting of requests. [SEC-req-2]
The semantics of the captured Targeted-to-URIs are derived from the
current context of the request as follows:
o Retargeted-from-URI: this is the Request URI that is being
changed due to the retargeting. It is the Targeted-to-URI in the
request received by the retargeting entity. If it was not
explicitly captured by the original sender/forwarder of the
request, it would be captured and added to the request prior to
the Targeted-to-URI currently being captured. If the
sender/forwarder supported History-Info, it would have been
added prior to sending/forwarding the Request.
o Retargeted-to-URI: this is the Targeted-to-URI being captured in
the request being retargeted.
The following summarizes the syntax of the History-Info header, based
upon the standard SIP syntax [4]:
History-Info = ("History-Info" / "h") HCOLON
hist-info *(COMMA hist-info)
hist-info = hi-targeted-to-uri *( SEMI HI-param )
hi-targeted-to-uri= name-addr
hi-param = hi-index / hi-extension
hi-index = "index" EQUAL 1*DIGIT *(DOT 1*DIGIT)
hi-extension = generic-param
2.2 Protocol Examples
History-Info:<sip:UserA@ims.nortelnetworks.com?Reason=SIP;
cause=302;text="Moved Temporarily">; foo=bar
History-Info: <sip:45432@vm.nortelnetworks.com?
Reason=SIP;cause=486;text="Busy Here"> ; index=1.1.2
2.3 Protocol usage
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This section describes the processing specific to UAs and Proxies for
the History-Info and the HistInfo option tag.
[Editor's note: Once the Security solution is fully fleshed out, it
may be reasonable to move this section 2.3 after section 2.4 and
provide the detailed security related processing prior to this
section, so that security aspects can be highlighted in this section,
as well.]
2.3.1 UAC Behavior
The UAC SHOULD include the HistInfo option tag in the Supported
header in any request not associated with an established dialog for
which the UAC would like the History-Info in the Response. In
addition, the UAC should initiate the capturing of the History
Information by capturing the Request-URI as the hi-targeted-to-uri
and initializing the index to 1.
The processing of the History-Info received in the response is
application specific and outside the scope of this draft.
2.3.2 UAS Behavior
The processing of History-Info by a UAS in a Request depends upon
local policy and specific applications at the UAS which might make
use of the information. If the HistInfo option tag is received in a
request, the UAS should include any History-Info received in the
request in the subsequent response.
2.3.3 Proxy Behavior
The use of History-Info does not alter the fundamental processing of
proxies for determining request targets as defined in section 16.5 of
[4]. Whether a proxy captures the History-Info depends upon several
factors:
o Whether the Request contains the HistInfo option tag in the
Supported header.
o Local Policy
The following are further considerations for refinement of a
local policy supporting History-Info:
o Whether retargeting within a Proxy is captured
o Whether the History-Info captured for a proxy/domain
should go outside that domain (e.g. a Proxy knows that
the information is potentially useful within that domain,
however, policies (for privacy, user and network
security, etc.) prohibit the exposure of that information
outside that domain).
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Each application making use of History-Info should address the
applicability and impacts of the local policies.
Consistent with basic SIP processing of optional headers, proxies
should maintain History-Info captured by other domains, received in
messages which they forward, independent of whether local policy
supports History-Info.
The specific processing by proxies for capturing the History-Info in
Requests and Responses is described in detail in the following
sections.
2.3.3.1 Capturing History-Info in Requests
If the proxy supports History-Info, the proxy SHOULD add any History-
Info collected as it retargets a Request. For retargets that are the
result of an explicit SIP response, the SIP Response Code that
triggered the retargeting MUST be included in the Reason header of
the Targeted-to-URI. For retargets as a result of timeouts or
internal events, a Reason header MAY be included in the Reason header
of the Targeted-to-URI. The History-Info SHOULD be added following
any History-Info received in the request being forwarded.
Additionally, if a request is received that doesn't include a
captured Request URI from the previous entity, the proxy MAY add an
additional entry, effectively capturing the retargeted-from-URI in
the Request.
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. The basic rule for adding the index
are to read the value from the previous History-Info, if available,
and capture the index.n as the index for the History-Info being
captured, where n would typically be 1 for a forwarded request. Thus,
the level of nesting of the index reflects the number of hops. For
retargets within a proxy, the proxy MUST maintain the current level
of nesting by incrementing the lowest/last digit of the index for
each instance of retargeting, thus reflecting the number of retargets
within the proxy. If there is no previous History-Info entry, the
index included for the current entry is RECOMMENDED to start at 1,
indicating a new thread of History-Info. An index MUST NOT be added
in the scenario whereby the received request had no History-Info
header and the retargeted-from-URI is being captured for
completeness. This allows the entities making use of the History-
Info to detect any gaps in History-Info captured in the request.
Parallel forking, as with basic SIP processing, does introduce
somewhat of a special case. In the case of parallel forking, the
proxy SHOULD capture each of the Request-URIs to which the Request is
forked in the manner previously described. However, since the forking
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is parallel, it's recommended that rather than attempt to send the
logical order of the requests being sent, that the information for
subsequent requests or responses is built upon receipt of the initial
response to ensure that the series of any subsequent forking and
retargeting of any of the forked requests accurately reflects the
logical sequence. Again, it is recommended that the index be
captured for each forked request following a similar model as that
previously described, with each new Request having a unique index.
The lack of Reason headers in the captured Request-URIs should be
indicative of the parallel nature of forking (i.e the Request-URIs
are not the result of retargets, but are rather all simultaneous
Targeted-To URIs.)
2.3.3.2 Processing History-Info in Responses
A proxy that receives a Request with the HistInfo option tag in the
Supported header, and depending upon a local policy supporting the
capture of History-Info, SHOULD return captured History-Info in
subsequent, provisional and final responses to the Request. A 183
response MAY be sent explicitly for the purposes of conveying
History-Info prior to the final response.
2.3.4 Redirect Server Behavior
It MAY be advantageous for redirect servers to support the receipt of
History-Info in requests. By receiving it in the request, the
Redirect Server MAY be able to optimize the information it sends in
responses by looking at the already targeted-to-URIs. However, a
redirect server SHOULD NOT add any new History-Info, as that would be
done by the entity receiving the 3xx response. Thus, a redirect
server SHOULD have local policy defined such that History-Info is not
captured, which should be the default. However, a redirect server
MAY include History-Info in responses to reflect retargets that have
already taken place by including any History-Info received in a
request in a subsequent response.
2.4 Security for History-Info
As discussed in Section 1, the security requirements are met by
recommending the use of TLS (a basic SIP requirement per [4]) and
through the use of the security solution defined in [5].
2.4.1 Security examples
[Editor's Note: Need to add some protocol details for protecting
History-Info once [5] is further along].
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2.5 Example Applications using History-Info
This scenario highlights an example where the History-Info in the
response is primarily of use in not retrying routes that have already
been tried by another proxy. Note, that this is just an example and
that there may be valid reasons why a Proxy would want to retry the
routes and thus, this would like be a local proxy or even user
specific policy.
UA 1 sends a call to "Bob" to proxy 1. Proxy 1 forwards the request
to Proxy 2. Proxy 2 parallel forks and tries several places (UA2,
UA3 and UA4) before sending a response to Proxy 1 that all the places
are busy. Proxy 1, without the History-Info, would try several of
the same places (UA3 and UA4)based upon registered contacts for
"Bob", before completing at UA5. However, with the History-Info,
Proxy 1 determines that UA3 and UA4 have already received the invite,
thus the INVITE goes directly to UA5.
UA1 Proxy1 Proxy2 UA2 UA3 UA4 UA5
| | | | | | |
|--INVITE -->| | | | | |
| |-INVITE->| | | | |
Supported: HistInfo
History-Info: <sip:Bob@P1>, <sip:Bob@P2>; index=1
| | | | | | |
| | |-INVITE>| | | |
History-Info: <sip:Bob@P1>, <sip:Bob@P2>; index=1,
<sip:User2@UA2>; index=1.1
| | | | | | |
| | |-----INVITE ---->| | |
History-Info: <sip:Bob@P1 >, <sip:Bob@P2 >; index=1,
<sip:User3@UA3>; index=1.2
| | | | | | |
| | |-------INVITE------------>| |
History-Info: <sip:Bob@P1 >, <sip:Bob@P2 >; index=1,
<sip:User4@UA4 >; index=1.3
/* All Responses from the INVITEs indicate Busy. */
| | | | | | |
| |<-486 ---| | | | |
History-Info: <sip:Bob@P1 >, <sip:Bob@P2 >; index=1,
<sip:User2@UA2>; index=1.1,
<sip:User3@UA3>; index=1.2,
<sip:User4@UA4>; index=1.3
| | | | | | |
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/* Upon receipt of the response, P1 determines another route for the
INVITE, but finds that it matches some routes already attempted (e.g.
UA2 and UA3, thus the INVITE is only forwarded to UA5, where the session
is successfully established */
| | | | | | |
| |----------------INVITE --------------------->|
History-Info: <sip:Bob@P1>, <sip:Bob@P2>; index=1,
<sip:User2@UA2>; index=1.1,
<sip:User3@UA3>; index=1.2,
<sip:User4@UA4>; index=1.3,
<sip:User5@UA5?Reason=SIP;cause=486>
| | | | | | |
| |<-----200 OK---------------------------------|
|<--200 OK---| | | | | |
| | | | | | |
|--ACK --------------------------------------------------->|
Additional detailed scenarios are available in the appendix.
3. Security Considerations
This draft provides a proposal for addressing the Security
requirements identified in [1] in sections 1.2 and 2.4 of this draft
by proposing the use of TLS between entities. The protection of the
History-Info is dependent upon a general solution for securing
headers added by proxies. This general solution is described in [5].
4. IANA Considerations
(Note to RFC Editor: Please fill in all occurrences of XXXX in this
section with the RFC number of this specification).
This document defines a new SIP header field name with a compact
form: History-Info and h respectively, and a new option tag:
HistInfo.
The following changes should be made to http:///www.iana.org/
assignments/sip-parameters
The following row should be added to the header field section:
Header Name Compact Form Reference
History-Info h [RFCXXXX]
The following should be added to the Options Tags section:
Name Description Reference
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HistInfo When used with the Supported header, [RFCXXXX]
this option tag indicates support
for the History Information to be
captured for requests and returned in
subsequent responses. This tag is not
used in a Proxy-Require or Requires
header field since support of
History-Info is optional.
5. Changes since last version
Changes from individual draft-barnes-sipping-history-info-02 to the รป00
WG version:
o Updated references and added reference to Security solution
draft.
o Removed appendix D which included background on analysis of
solution options.
o Cleaned up the document format per rfc2223bis.
o Strengthened the inclusion of the INDEX as a MUST (per discussion
at IETF-56).
o Added text around the capturing of the Reason (SHOULD be captured
for SIP responses and MAY be captured for other things such as
timeouts).
o Clarified the response processing 2.3.3.2 to include provisional
responses and the sending of a 183 to convey History-Info.
o Added section 2.3.4 to address Redirect Server behavior.
References
[1] M. Barnes, M. Watson, C. Jennings, J. Peterson, "SIP Generic
Request History Capability Requirements", draft-ietf-sipping-req-
history-04.txt, June, 2003.
[2] A. Johnson, "SIP Service Examples", draft-ietf-sipping-service-
examples-03.txt, November, 2002.
[3] H. Schulzrinne, D. Oran, G. Camarillo, "The Reason Header Field
for the Session Initiation Protocol", RFC 3326, December, 2002.
[4] J. Rosenberg et al, "SIP: Session initiation protocol," RFC 3261,
June, 2002.
[5] M. Barnes, "A Mechanism to Secure SIP Identity Headers Inserted
by Intermediaries", draft-barnes-sipping-inserted-info-00.txt, June,
2003.
[6] J. Peterson, "A Privacy Mechanism for the Session Initiation
Protocol (SIP)", RFC 3323, November, 2002.
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[7] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.
[8] J. Peterson, "Enhancements for Authenticated Identity Management
in the Session Initiation Protocol (SIP)", draft-ietf-sip-identity-
01.txt, February, 2003.
[9] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
Acknowledgements
The editor would like to acknowledge the constructive feedback
provided by Robert Sparks, Paul Kyzivat, Scott Orton, John Elwell,
Nir Chen, Francois Audet, Anthony Brown, and Jayshree Bharatia.
The editor would like to acknowledge the significant input from
Rohan Mahy on some of the normative aspects of the ABNF, particularly
around the need for and format of the index.
Contributors' Addresses
Cullen and Mark provided substantial input in the form of email
discussion in the development of the initial version of this
individual solution document.
Cullen Jennings
Cisco Systems
170 West Tasman Dr
MS: SJC-21/3
Tel: +1 408 527 9132
Email: fluffy@cisco.com
Mark Watson
Nortel Networks (UK)
Maidenhead Office Park (Bray House)
Westacott Way
Maidenhead,
Berkshire
England
Tel: +44 (0)1628-434456
Email: mwatson@nortelnetworks.com
Authors' Address
Mary Barnes
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Nortel Networks
2380 Performance Drive
Richardson, TX USA
Phone: 1-972-684-5432
Email: mbarnes@nortelnetworks.com
Appendix A Forking Scenarios
A.1 Sequentially forking (Hist-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.
UA 1 sends a call to "Bob" via proxy 1. Proxy 1 sequentially tries
several places (UA2, UA3 and UA4) unsuccessfully before sending a
response to UA1.
This scenario is provided to show that by providing the History-Info
to UA1, the end user or an application at UA1 could make a decision
on how best to attempt finding "Bob". Without this mechanism UA1
might well attempt UA3 (and thus UA4) and then re-attempt UA4 on a rd 3 manual attempting at reaching "Bob". With this mechanism, either
the end user or application could know that "Bob" is busy on his home
phone and is physically not in the office. If there were an
alternative address for "Bob" known to this end user or application,
that hasn't been attempted, then either the application or the end
user could attempt that. The intent here is to highlight an example
of the flexibility of this mechanism that enables applications well
beyond SIP as it is certainly well beyond the scope of this draft to
prescribe detailed applications.
UA1 Proxy1 UA2 UA3 UA4
| | | | |
|--INVITE -->| | | |
| | | | |
| |--INVITE -------->| | |
|<--100 -----| | | |
| |<-302 ------------| | |
| | | | |
| |-------INVITE ------------>| |
| | | | |
| |<-------180 ---------------| |
|<---180 ----| | | |
| . . |-------INVITE------------->| |
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| | timeout | | |
| | | | |
| |------INVITE ---------------------->|
|<--100 -----| | | |
| | | | |
| |<-486 ------------------------------|
| | | | |
| |-- ACK ---------------------------->|
|<--486------| | | |
| | | | |
|--ACK ----->| | | |
| | | | |
[Editor's Note: Need to detail the message flow.]
A.2 Sequential Forking (with Success)
This scenario highlights an example where the History-Info in the
request is primarily of use in not retrying routes that have already
been tried by another proxy. Note, that this is just an example and
that there may be valid reasons why a Proxy would want to retry the
routes and thus, this would like be a local proxy or even user
specific policy.
UA 1 sends a call to "Bob" to proxy 1. Proxy 1 sequentially tries
several places (UA2, UA3 and UA4) before retargeting the call to
Proxy 2. Proxy 2, without the History-Info, would try several of the
same places (UA3 and UA4)based upon registered contacts for "Bob",
before completing at UA5. However, with the History-Info, Proxy 2
determines that UA3 and UA4 have already received the invite, thus
the INVITE goes directly to UA5.
UA1 Proxy1 Proxy2 UA2 UA3 UA4 UA5
| | | | | | |
|--INVITE -->| | | | | |
| | | | | | |
| |--INVITE -------->| | | |
|<--100 -----| | | | | |
| |<-302 ------------| | | |
| | | | | | |
| |-------INVITE ------------>| | |
| | | | | | |
| |<-------180 ---------------| | |
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|<---180 ----| | | | | |
| . . |-------INVITE------------->| | |
| | timeout | | | |
| | | | | | |
| |------INVITE ---------------------->| |
|<--100 -----| | | | | |
| |<-302 ------------------------------| |
| | | | | | |
| |-INVITE->| | | | |
| | | | | | |
| | | | | | |
| | |------INVITE --------------------->|
| | | | | | |
| | |<-----200 OK---------------------->|
|<--200 OK-------------| | | | |
| | | | | | |
|--ACK --------------------------------------------------->|
[Editor's Note: Need to add the details of the messages here.]
Appendix B Voicemail
This scenario highlights an example where the History-Info in the
request is primarily of use by an edge service (e.g. Voicemail
Server). It should be noted that this isn't intended to be a complete
specification for this specific edge service as it is quite likely
that additional information is need by the edge service. History-Info
is just one building block that this service makes use of.
UA 1 called UA A which had been forwarded to UA B which forwarded to
a UA VM (voicemail server). Based upon the retargeted URIs and
Reasons (and other information) in the INVITE, the VM server makes a
policy decision about what mailbox to use, which greeting to play
etc.
UA1 Proxy UA-A UA-B UA-VM
| | | | |
|--INVITE F1-->| | | |
| | | | |
| |--INVITE F2-->| | |
|<--100 F3-----| | | |
| |<-302 F4------| | |
| | | | |
| |--------INVITE F5---------->| |
| | | | |
| |<--------180 F6-------------| |
|<---180 F7----| | | |
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| . . . | | | |
| |------retransmit INVITE---->| |
| . . . | | | |
| | (timeout) | |
| | | | |
| |-------INVITE F8---------------------->|
| | | | |
| |<-200 F9-------------------------------|
| | | | |
|<-200 F10-----| | | |
| | | | |
|--ACK F11-------------------------------------------->|
Message Details
INVITE F1 UA1->Proxy
INVITE sip:UserA@nortelnetworks.com SIP/2.0
Via: SIP/2.0/UDP here.com:5060
From: BigGuy <sip:User1@here.com>
To: LittleGuy <sip:UserA@nortelnetworks.com>
Call-Id: 12345600@here.com
CSeq: 1 INVITE
Contact: BigGuy <sip:User1@here.com>
Content-Type: application/sdp
Content-Length: <appropriate value>
v=0
o=UserA 2890844526 2890844526 IN IP4 client.here.com
s=Session SDP
c=IN IP4 100.101.102.103
t=0 0
m=audio 49170 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/*Client for UA1 prepares to receive data on port 49170
from the network. */
INVITE F2 Proxy->UA-A
INVITE sip:UserA@ims.nortelnetworks.com SIP/2.0
Via: SIP/2.0/UDPims.nortelnetworks.com:5060;branch=1
Via: SIP/2.0/UDP here.com:5060
Record-Route: <sip:UserA@nortelnetworks.com>
From: BigGuy <sip:User1@here.com>
To: LittleGuy <sip:UserA@nortelnetworks.com>
Call-Id: 12345600@here.com
CSeq: 1 INVITE
History-Info: <sip:UserA@ims.nortelnetworks.com>; index=1
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Contact: BigGuy <sip:User1@here.com>
Content-Type: application/sdp
Content-Length: <appropriate value>
v=0
o=UserA 2890844526 2890844526 IN IP4 client.here.com
s=Session SDP
c=IN IP4 100.101.102.103
t=0 0
m=audio 49170 RTP/AVP 0
a=rtpmap:0 PCMU/8000
100 Trying F3 Proxy->UA1
SIP/2.0 100 Trying
Via: SIP/2.0/UDP here.com:5060
From: BigGuy <sip:User1@here.com>
To: LittleGuy <sip:UserA@nortelnetworks.com>
Call-Id: 12345600@here.com
CSeq: 1 INVITE
Content-Length: 0
302 Moved Temporarily F4 UserA->Proxy
SIP/2.0 302 Moved Temporarily
Via: SIP/2.0/UDP ims.nortelnetworks.com:5060;branch=1
Via: SIP/2.0/UDP here.com:5060
From: BigGuy <sip:User1@here.com>
To: LittleGuy <sip:UserA@nortelnetworks.com>;tag=3
Call-Id: 12345600@here.com
CSeq: 1 INVITE
Contact: <sip:UserB@nortelnetworks.com>
Content-Length: 0
INVITE F5 Proxy-> UA-B
INVITE sip:UserB@nortelnetworks.com SIP/2.0
Via: SIP/2.0/UDP ims.nortelnetworks.com:5060;branch=2
Via: SIP/2.0/UDP here.com:5060
From: BigGuy <sip:User1@here.com>
To: LittleGuy <sip:UserA@nortelnetworks.com>
Call-Id: 12345600@here.com
History-Info: <sip:UserA@ims.nortelnetworks.com>; index=1,
<sip:UserB@nortelnetworks.com?Reason=SIP; cause=302; text="Moved
Temporarily">;index=2
CSeq: 1 INVITE
Contact: BigGuy <sip:User1@here.com>
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Content-Type: application/sdp
Content-Length: <appropriate value>
v=0
o=User1 2890844526 2890844526 IN IP4 client.here.com
s=Session SDP
c=IN IP4 100.101.102.103
t=0 0
m=audio 49170 RTP/AVP 0
a=rtpmap:0 PCMU/8000
180 Ringing F6 UA-B ->Proxy
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP there.com:5060
From: BigGuy <sip:User1@here.com>
To: LittleGuy <sip:UserA@nortelnetworks.com>;tag=5
Call-ID: 12345600@here.com
CSeq: 1 INVITE
Content-Length: 0
180 Ringing F7 Proxy-> UA1
SIP/2.0 180 Ringing
SIP/2.0/UDP here.com:5060
From: BigGuy <sip:User1@here.com>
To: LittleGuy <sip:UserA@nortelnetworks.com>
Call-Id: 12345600@here.com
CSeq: 1 INVITE
Content-Length: 0
/* User B is not available. INVITE is sent multiple
times until it times out. */
/* The proxy forwards the INVITE to UA-VM after adding the
additional History Information entry. */
INVITE F8 Proxy-> UA-VM
INVITE sip:VM@nortelnetworks.com SIP/2.0
Via: SIP/2.0/UDP ims.nortelnetworks.com:5060;branch=3
Via: SIP/2.0/UDP here.com:5060
From: BigGuy <sip:User1@here.com>
To: LittleGuy <sip:UserA@nortelnetworks.com>
Call-Id: 12345600@here.com
History-Info: <sip:UserA@ims.nortelnetworks.com>;index=1,
<sip:UserB@nortelnetworks.com?Reason=SIP; cause=302; text="Moved
Temporarily">;index=2,
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<sip:VM@nortelnetworks.com?Reason=SIP;cause=480;text="Temporarily
Unavailable">;index=3
CSeq: 1 INVITE
Contact: BigGuy <sip:User1@here.com>
Content-Type: application/sdp
Content-Length: <appropriate value>
v=0
o=User1 2890844526 2890844526 IN IP4 client.here.com
s=Session SDP
c=IN IP4 100.101.102.103
t=0 0
m=audio 49170 RTP/AVP 0
a=rtpmap:0 PCMU/8000
200 OK F9
SIP/2.0 200 OK UA-VM->Proxy
Via: SIP/2.0/UDP ims.nortelnetworks.com:5060;branch=3
Via: SIP/2.0/UDP here.com:5060
From: BigGuy <sip:User1@here.com>
To: LittleGuy <sip:UserA@nortelnetworks.com>;tag=3
Call-Id: 12345600@here.com
CSeq: 1 INVITE
Contact: TheVoiceMail <sip:VM@nortelnetworks.com>
Content-Type: application/sdp
Content-Length: <appropriate value>
v=0
o=UserA 2890844527 2890844527 IN IP4 vm.nortelnetworks.com
s=Session SDP
c=IN IP4 110.111.112.114
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
200 OK F10 Proxy->UA1
SIP/2.0 200 OK
Via: SIP/2.0/UDP ims.nortelnetworks.com:5060;branch=3
Via: SIP/2.0/UDP here.com:5060
From: BigGuy <sip:User1@here.com>
To: LittleGuy <sip:UserA@nortelnetworks.com>;tag=3
Call-Id: 12345600@here.com
CSeq: 1 INVITE
Contact: TheVoiceMail <sip:VM@nortelnetworks.com>
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Content-Type: application/sdp
Content-Length: <appropriate value>
v=0
o=UserA 2890844527 2890844527 IN IP4 vm.nortelnetworks.com
s=Session SDP
c=IN IP4 110.111.112.114
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
ACK F11 UA1-> UA-VM
ACK sip:VM@nortelnetworks.com SIP/2.0
Via: SIP/2.0/UDP here.com:5060
From: BigGuy <sip:User1@here.com>
To: LittleGuy<sip:UserA@nortelnetworks.com>;tag=3
Call-Id: 12345600@here.com
CSeq: 1 ACK
Content-Length: 0
/* RTP streams are established between UA1 and
UA-VM. UA-VM starts announcement for UA1 */
Appendix C Automatic Call Distribution Example
This scenario highlights an example of an Automatic Call Distribution
service, where the agents are divided into groups based upon the type
of customers they handle. In this example, the Gold customers are
given higher priority than Silver customers, so a Gold call would get
serviced even if all the agents servicing the Gold group (ACDGRP1)
were busy, by retargeting the request to the Silver Group. Upon
receipt of the call at the agent assigned to handle the incoming
call, based upon the History-Info in the message, the application at
the agent can provide an indication that this is a Gold call, from
how many groups it might have overflowed before reaching the agent,
etc. thus can be handled appropriately by the agent.
For scenarios whereby calls might overflow from the Silver to the
Gold, clearly the alternate group identification, internal routing or
actual agent that handles the call SHOULD not be sent to UA1, thus
for this scenario, one would expect that the Proxy would not support
the sending of the History-Info in the response, even if requested by
the calling UA.
As with the other examples, this is not prescriptive of how one would
do this type of service but an example of a subset of processing that
might be associated with such a service. In addition, this example
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is not addressing any aspects of Agent availability, which might also
be done via a SIP interface.
UA1 Proxy ACDGRP1 Svr ACDGRP2 Svr UA2-ACDGRP2
| | | | |
|--INVITE F1-->| | | |
Supported:HistInfo
| | | | |
| |--INVITE F2-->| | |
Supported:HistInfo
History-Info: <sip:Gold@ACD.com>; index=1
History-Info: <sip:ACDGRP1@ACD.com>; index=1.1
| | | | |
| |<-302 F3------| | |
Contact: <sip:ACDGRP2@ACD.com>
| | | | |
| |--------INVITE F4---------->| |
History-Info: <sip:Gold@ACD.com>; index=1
History-Info: <sip:ACDGRP1@ACD.com>; index=1.1
History-Info: <sip:ACDGRP2@ACD.com>; index=1.2
| | | | |
| | | | |
| | | |INVITE F5>|
History-Info: <sip:Gold@ACD.com>; index=1
History-Info: <sip:ACDGRP1@ACD.com>; index=1.1
History-Info: <sip:ACDGRP2@ACD.com>; index=1.2
| | | | |
| | | |<-200 F6--|
| | | | |
| |<-200 F7--------------------| |
History-Info: <sip:Gold@ACD.com>; index=1
History-Info: <sip:ACDGRP1@ACD.com>; index=1.1
History-Info: <sip:ACDGRP2@ACD.com>; index=1.2
|<-200 F8------| | | |
< No History-Info included in the response due to Local Policy>
| | | | |
|--ACK F9--------------------------------------------->|
Message Details
[To be completed]
Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
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This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English. The limited permissions granted above are perpetual and
will not be revoked by the Internet Society or its successors or
assigns. This document and the information contained herein is
provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
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