draft-ietf-sipping-req-history-00.txt   draft-ietf-sipping-req-history-01.txt 
Internet Draft Mary Barnes,Editor Internet Draft Mary Barnes,Editor
Document: draft-ietf-sipping-req-history-00.txt Mark Watson Document: draft-ietf-sipping-req-history-01.txt Mark Watson
Nortel Networks Nortel Networks
Cullen Jennings Cullen Jennings
Cisco Cisco
Jon Peterson Jon Peterson
Category: Informational NeuStar Category: Informational NeuStar
Expires February 2003 August 2002 Expires June 2003 December 2002
SIP Generic Request History Capability û Requirements SIP Generic Request History Capability û Requirements
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with all This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026. provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other Force (IETF), its areas, and its working groups. Note that other
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capabilities that enable calls to be routed to chosen applications, capabilities that enable calls to be routed to chosen applications,
there is currently no standard mechanism within SIP for communicating there is currently no standard mechanism within SIP for communicating
the history of such a request. This "request history" information the history of such a request. This "request history" information
allows the receiving application to determine hints about how and why allows the receiving application to determine hints about how and why
the call arrived at the application/user. the call arrived at the application/user.
This draft discusses the motivations in support of a mechanism for This draft discusses the motivations in support of a mechanism for
recording the "request history", and proposes detailed requirements recording the "request history", and proposes detailed requirements
for such a generic "request history" capability. for such a generic "request history" capability.
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Table of Contents Table of Contents
1. Introduction: Why define a Generic "Request History" capability? 1. Introduction: Why define a Generic "Request History" capability?
2 2
2. Conventions used in this document..............................3 2. Conventions used in this document..............................3
3. "Request History" Requirements.................................3 3. "Request History" Requirements.................................3
4. Security Considerations........................................5 4. Security Considerations........................................5
5. IANA Considerations............................................6 5. Privacy Considerations.........................................6
7. Contributors...................................................6 6. IANA Considerations............................................6
8. Acknowledgments................................................6 7. References.....................................................6
9. Appendix A - Scenarios.........................................8 8. Contributors...................................................6
9.1. Sequentially forking with Retargetting................8 9. Acknowledgments................................................7
9.2. Voicemail............................................10 10. Appendix A - Scenarios.........................................8
10.1 Sequentially forking with Retargeting.................8
10.2 Voicemail............................................10
1. Introduction: Why define a Generic "Request History" capability? 1. Introduction: Why define a Generic "Request History" capability?
SIP implicitly provides redirect/retarget capabilities that enable SIP implicitly provides redirect/retarget capabilities that enable
calls to be routed to specific applications as defined in [1]. The calls to be routed to specific applications as defined in [1]. The
term retarget will be used henceforth in this draft to refer to the term retarget will be used henceforth in this draft to refer to the
process of a Proxy Server/UAC changing a URI in a request and thus process of a Proxy Server/UAC changing a URI in a request and thus
changing the target of the request. This term is chosen to avoid changing the target of the request. This term is chosen to avoid
associating this request history only with the specific SIP associating this request history only with the specific SIP
Redirect Server capability that provides for a response to be sent Redirect Server capability that provides for a response to be sent
back to a UAC requesting that the UAC should retarget the original back to a UAC requesting that the UAC should retarget the original
request to an alternate URI. The rules for determining request request to an alternate URI. The rules for determining request
targets as described in section 16.5 of [1] are believed to be targets as described in section 16.5 of [1] are consistent with the
consistent with the use of the retarget term in this draft. use of the retarget term in this draft.
The motivation for the request history is that in the process of The motivation for the request history is that in the process of
retargeting old routing information can be forever lost. This lost retargeting old routing information can be forever lost. This lost
information may be important history that allows elements to which information may be important history that allows elements to which
the call is retargeted to process the call in a locally defined, the call is retargeted to process the call in a locally defined,
application specific manner. The proposal in this draft is to application specific manner. The proposal in this draft is to
provide a mechanism for transporting the request history. It is provide a mechanism for transporting the request history. It is
not proposing any behavior for a Proxy or UA upon receipt of the not proposing any behavior for a Proxy or UA upon receipt of the
information. Indeed, such behavior should be a local decision for information. Indeed, such behavior should be a local decision for
the recipient application. the recipient application.
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application specific manner. The proposal in this draft is to application specific manner. The proposal in this draft is to
provide a mechanism for transporting the request history. It is provide a mechanism for transporting the request history. It is
not proposing any behavior for a Proxy or UA upon receipt of the not proposing any behavior for a Proxy or UA upon receipt of the
information. Indeed, such behavior should be a local decision for information. Indeed, such behavior should be a local decision for
the recipient application. the recipient application.
Current network applications provide the ability for elements Current network applications provide the ability for elements
involved with the call to exchange additional information relating involved with the call to exchange additional information relating
to how and why the call was routed to a particular destination. to how and why the call was routed to a particular destination.
The following are examples of such applications: The following are examples of such applications:
1. Web "referral" applications, whereby an application residing 1. Web "referral" applications, whereby an application residing
within a web server determines that a visitor to a website has within a web server determines that a visitor to a website has
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arrived at the site via an "associate" site which will receive arrived at the site via an "associate" site which will receive
some "referral" commission for generating this traffic, some "referral" commission for generating this traffic,
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2. Email forwarding whereby the forwarded-to user obtains a 2. Email forwarding whereby the forwarded-to user obtains a
"history" of who sent the email to whom and at what time "history" of who sent the email to whom and at what time
3. Traditional telephony based call redirection services such as 3. Traditional telephony services such as Voicemail, call-center
Voicemail, call-center "automatic call distribution", and "automatic call distribution", and "follow-me" style services.
"follow-me" style services.
Several of the aforementioned applications, and specifically those Several of the aforementioned applications define application
applications based on email or WWW, define application specific specific mechanisms through which it is possible to obtain the
mechanisms through which it is possible to obtain the necessary necessary history information.
history information.
In order to prevent differing proprietary mechanisms emerging to In addition, request history information could be used to enhance
obtain the required "request history" information, it is proposed basic SIP functionality by providing:
that the SIPPING WG evaluate the requirements and determine a
generic mechanism for the transport of such "request history" 4. Some diagnostic information for debugging SIP requests.
information.
5. A stronger security solution for SIP. A side effect is that each
proxy which captures the "request history" information in a
secure manner provides an additional means (without requiring
signed keys) for the original requestor to be assured that the
request was properly retargeted.
This draft summarizes the requirements for defining a generic
mechanism for the transport of request history information.
Example scenarios are provided in the appendix illustrating how a
SIP building block that provides request history information could
be used by some applications. It is not the intent, nor is it
within the scope, of this requirementÆs draft to prescribe a
complete solution for any of these applications.
2. Conventions used in this document 2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC-2119. this document are to be interpreted as described in RFC-2119.
3. "Request History" Requirements 3. "Request History" Requirements
The following list constitutes a set of requirements for a "Request The following list constitutes a set of requirements for a "Request
History" capability. It is anticipated that some of these History" capability. It is anticipated that some of these
requirements can be met using existing elements within SIP; whether requirements can be met using existing elements within SIP; whether
and what SIP extensions would be needed to meet these requirements and what SIP extensions would be needed to meet these requirements
is out of scope of this draft. is out of scope of this draft.
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1) CAPABILITY-req: The "Request History" capability will provide a 1) CAPABILITY-req: The "Request History" capability will provide a
capability to inform proxies and UAs involved in processing a capability to inform proxies and UAs involved in processing a
request about the history/progress of that request. While this is request about the history/progress of that request. While this is
inherently provided when the retarget is in response to a SIP inherently provided when the retarget is in response to a SIP
redirect, it is deemed useful for non-redirect retargeting redirect, it is deemed useful for non-redirect retargeting
scenarios, as well. scenarios, as well.
2) OPTIONALITY-req: The "Request History" information is optional. 2) OPTIONALITY-req: The "Request History" information is optional.
2.1) In many cases, it is anticipated that whether the history is 2.1) In many cases, it is anticipated that whether the history is
added to the Request would be a local policy decision enforced by added to the Request would be a local policy decision enforced by
the specific application, thus no specific protocol element is the specific application, thus no specific protocol element is
needed. needed.
2.2) Due to the capability being "optional" from the SIP protocol 2.2) Due to the capability being "optional" from the SIP protocol
perspective, the impact to an application of not having the perspective, the impact to an application of not having the
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"Request History" must be described. Applicability guidelines to be "Request History" must be described. Applicability guidelines to be
addressed by applications using this capability must be provided as addressed by applications using this capability must be provided as
part of the solution to these requirements. part of the solution to these requirements.
3) GENERATION-req: "Request History" information is generated when 3) GENERATION-req: "Request History" information is generated when
the request is retargeted. the request is retargeted.
3.1) In some scenarios, it might be possible for more than one 3.1) In some scenarios, it might be possible for more than one
instance of retargeting to occur within the same Proxy. A proxy instance of retargeting to occur within the same Proxy. A proxy
should also generate Request History information for the 'internal should also generate Request History information for the 'internal
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responses. responses.
5) CONTENT-req: The "Request History" information for each 5) CONTENT-req: The "Request History" information for each
occurrence of retargeting, shall include the following: occurrence of retargeting, shall include the following:
5.1) The new URI or address to which the request is in the 5.1) The new URI or address to which the request is in the
process of being retargeted, process of being retargeted,
5.2) The URI or address from which the request was retargeted, 5.2) The URI or address from which the request was retargeted,
5.3) The reason for the Request-URI modification. The reason for 5.3) The reason for the Request-URI modification,
the retargeting is only known to the application performing the
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be defined, SIP Generic Request History Capability - Requirements December 2002
5.4) Chronological ordering of the Request History information. 5.4) Chronological ordering of the Request History information.
6) REQUEST-VALIDITY-req: Request-History is applicable to requests 6) REQUEST-VALIDITY-req: Request-History is applicable to requests
not sent within an established dialog. (i.e. INVITE, REGISTER, not sent within an established dialog. (i.e. INVITE, REGISTER,
MESSAGE, and OPTIONS). MESSAGE, and OPTIONS).
7) BACKWARDS-req: Request-History information may be passed from 7) BACKWARDS-req: Request-History information may be passed from
the generating entity backwards towards the UAC. This is needed to the generating entity backwards towards the UAC. This is needed to
enable services that inform the calling party about the dialog enable services that inform the calling party about the dialog
establishment attempts. establishment attempts.
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8) FORWARDS-req: Request-History information may also be included 8) FORWARDS-req: Request-History information may also be included
by the generating entity in the request, if it is forwarded by the generating entity in the request, if it is forwarded
onwards. onwards.
4. Security Considerations 4. Security Considerations
The Request History information is being inserted by a network The Request History information is being inserted by a network
element retargeting a Request, resulting in a slightly different element retargeting a Request, resulting in a slightly different
problem than the basic SIP header problem, thus requiring specific problem than the basic SIP header problem, thus requiring specific
consideration. In addition, there may be privacy implications consideration. It is recognized that these security requirements
associated with some of the Request History information. can be generalized to a basic requirement of being able to secure
information that is inserted by proxies.
The potential security problems introduced include the following: The potential security problems include the following:
1) A rogue application could insert a bogus Request History entry 1) A rogue application could insert a bogus Request History entry
either by adding an additional entry as a result of retargeting or either by adding an additional entry as a result of retargeting or
entering invalid information. entering invalid information.
2) Loss of privacy associated with forwarding a specific Request 2) Loss of privacy associated with forwarding a specific Request
URI in the Request History. URI in the Request History.
3) A rogue application could re-arrange the Request History 3) A rogue application could re-arrange the Request History
information to change the nature of the end application or to information to change the nature of the end application or to
mislead the receiver of the information. mislead the receiver of the information.
Thus, any solution to "Request History" capability must meet the Thus, a security solution for "Request History" must meet the
following requirements: following requirements:
1) SEC-req-1: The entity receiving the Request History must be able 1) SEC-req-1: The entity receiving the Request History must be able
to determine whether any of the previously added Request History to determine whether any of the previously added Request History
content has been altered. content has been altered.
2) SEC-req-2: The ordering of the Request History information must 2) SEC-req-2: The ordering of the Request History information must
be preserved at each instance of retargeting. be preserved at each instance of retargeting.
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3) SEC-req-3: The entity receiving the information conveyed by the 3) SEC-req-3: The entity receiving the information conveyed by the
Request History must be able to authenticate the source of the Request History must be able to authenticate the source of the
information. information.
It is likely that the solutions to several of the requirements are 4) SEC-req-4: To ensure the confidentiality of the Request History
inter-related. For example, with the requirement for Chronological information, only entities which process the request should have
ordering [Requirement 5.4 in section 3], it is likely that the visibility to the information.
solution to SEC-req-1 would also meet SEC-req-2.
It should also be noted that these requirements apply to any entity
making use of the Request History information, either by
retargeting and capturing the information, or as an application
making use of the information in a Request or Response. However,
to ensure the overall integrity of this information as it traverses
Watson Expires - February 2003 [Page 5] It should be noted that these security requirements apply to any
SIP Generic Request History Capability - Requirements August 2002 entity making use of the Request History information, either by
retargeting and capturing the information, or as an application
making use of the information in a Request or Response.
the network, an additional requirement with regards to the security 5.Privacy Considerations
of the transport is introduced:
4) SEC-req-4: To ensure the overall integrity of the chain of Since the Request URI that is captured could inadvertently reveal
Request History information, the transport must be secure. information about the originator, there are general privacy
requirements that MUST be met:
In addition, there are general privacy requirements that MUST be 1) PRIV-req-1: The entity retargeting the Request must ensure that
met: it maintains the network-provided privacy (as described in [2])
5) PRIV-req-1: The entity retargeting the Request must ensure that associated with the Request as it is retargeted.
it maintains the privacy (as described in [2]) associated with the
original Request URI which is retargeted.
6) PRIV-req-2: The entity receiving the Request History must 2) PRIV-req-2: The entity receiving the Request History must
maintain the privacy associated with the information. maintain the privacy associated with the information.
It is recognized that meeting the privacy requirements can impact It is recognized that meeting the privacy requirements can impact
the functionality of this solution by overriding the request to the functionality of this solution by overriding the request to
generate the information. The applicability guidelines for a generate the information. The applicability guidelines for a
solution must clearly address this impact. solution must clearly address this impact.
5. IANA Considerations 6.IANA Considerations
This document does not have any implications for IANA. This document does not have any implications for IANA.
6. References 7.References
[1] J. Rosenberg et al, "SIP: Session initiation protocol," RFC [1] J. Rosenberg et al, "SIP: Session initiation protocol," RFC
3261, June, 2002. 3261, June, 2002.
[2] J. Peterson, "SIP Privacy", draft-ietf-sip-privacy-general- [2] J. Peterson, "A Privacy Mechanism for the Session Initiation
01.txt, June, 2002. Protocol (SIP)", RFC 3323, November, 2002.
7. Contributors 8. Contributors
Robert Sparks contributed excellent feedback and direction for Robert Sparks contributed excellent feedback and direction for
the Security considerations section of this document. In the Security considerations section of this document. In
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addition, he highlighted the importance of addressing the addition, he highlighted the importance of addressing the
optionality aspects of the "Request History" capability. optionality aspects of the "Request History" capability.
8. Acknowledgments 9. Acknowledgments
The authors would like to thank Chris Hogg for serving as the The editor would like to thank Sanjoy Sen, Ben Campbell, Rohan
editor for the initial (-00) version of this draft. In addition, Mahy and Jonathan Rosenberg for providing useful comments and
Sanjoy Sen and Ben Campbell provided useful comments and
suggestions related to this draft. suggestions related to this draft.
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AuthorsÆ Addresses AuthorsÆ Addresses
Mark Watson Mark Watson
Nortel Networks (UK) Nortel Networks (UK)
Maidenhead Office Park (Bray House) Maidenhead Office Park (Bray House)
Westacott Way Westacott Way
Maidenhead, Maidenhead,
Berkshire Tel: +44 (0)1628-434456 Berkshire Tel: +44 (0)1628-434456
England Email: mwatson@nortelnetworks.com England Email: mwatson@nortelnetworks.com
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others, and derivative works that comment on or otherwise explain others, and derivative works that comment on or otherwise explain
it or assist in its implementation may be prepared, copied, it or assist in its implementation may be prepared, copied,
published and distributed, in whole or in part, without restriction published and distributed, in whole or in part, without restriction
of any kind, provided that the above copyright notice and this of any kind, provided that the above copyright notice and this
paragraph are included on all such copies and derivative works. paragraph are included on all such copies and derivative works.
However, this document itself may not be modified in any way, such However, this document itself may not be modified in any way, such
as by removing the copyright notice or references to the Internet as by removing the copyright notice or references to the Internet
Society or other Internet organizations, except as needed for the Society or other Internet organizations, except as needed for the
purpose of developing Internet standards in which case the purpose of developing Internet standards in which case the
procedures for copyrights defined in the Internet Standards process procedures for copyrights defined in the Internet Standards process
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must be followed, or as required to translate it into languages must be followed, or as required to translate it into languages
other than English. The limited permissions granted above are other than English. The limited permissions granted above are
perpetual and will not be revoked by the Internet Society or its perpetual and will not be revoked by the Internet Society or its
successors or assigns. This document and the information contained successors or assigns. This document and the information contained
herein is provided on an "AS IS" basis and THE INTERNET SOCIETY herein is provided on an "AS IS" basis and THE INTERNET SOCIETY
AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL
WARRANTIES,EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES,EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE
ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE." FOR A PARTICULAR PURPOSE."
Watson Expires - February 2003 [Page 7] 10. Appendix A - Scenarios
SIP Generic Request History Capability - Requirements August 2002
9. Appendix A - Scenarios
This section highlights some scenarios under which the Request This section highlights some scenarios under which the Request
History Capability could be applicable. History Capability could be applicable.
Certainly, various other solutions can be applied in some fashion Certainly, various other solutions can be applied in some fashion
to each of these scenarios. However, the objective of this draft to each of these scenarios. However, the objective of this draft
has been to abstract the requirements from these scenarios towards has been to abstract the requirements from these scenarios towards
providing a more robust solution for each and at the same time providing a more robust solution for each and at the same time
providing fundamental building block(s) applicable to future providing fundamental building block(s) applicable to future
applications. applications.
9.1. Sequentially forking with Retargeting 10.1 Sequentially forking with Retargeting
This scenario is as follows: This scenario is as follows:
UA 1 sends a call to proxy 1. Proxy 1 sequentially tries several UA 1 sends a call to proxy 1. Proxy 1 sequentially tries several
places (UA2, UA3 and UA4) before retargeting the call to Proxy 2. places (UA2, UA3 and UA4) before retargeting the call to Proxy 2.
Proxy 2 unfortunately tries several of the same places (UA3 and Proxy 2 unfortunately tries several of the same places (UA3 and
UA4), before completing at UA5. UA4), before completing at UA5.
UA1 Proxy1 Proxy2 UA2 UA3 UA4 UA5 UA1 Proxy1 Proxy2 UA2 UA3 UA4 UA5
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|--INVITE -->| | | | | | |--INVITE -->| | | | | |
| | | | | | | | | | | | | |
| |--INVITE -------->| | | | | |--INVITE -------->| | | |
|<--100 -----| | | | | | |<--100 -----| | | | | |
| |<-302 ------------| | | | | |<-302 ------------| | | |
| | | | | | | | | | | | | |
| |-------INVITE ------------>| | | | |-------INVITE ------------>| | |
| | | | | | | | | | | | | |
| |<-------180 ---------------| | | | |<-------180 ---------------| | |
|<---180 ----| | | | | | |<---180 ----| | | | | |
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| . . |-------INVITE------------->| | | | . . |-------INVITE------------->| | |
| | timeout | | | | | | timeout | | | |
| | | | | | | | | | | | | |
| |------INVITE ---------------------->| | | |------INVITE ---------------------->| |
|<--100 -----| | | | | | |<--100 -----| | | | | |
| |<-302 ------------------------------| | | |<-302 ------------------------------| |
| | | | | | | | | | | | | |
| |-INVITE->| | | | | | |-INVITE->| | | | |
| | | | | | | | | | | | | |
| | |---INVITE ------>| | | | | |---INVITE ------>| | |
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| | | | | | | | | | | | | |
| | |<---180----------| | | | | |<---180----------| | |
|<---180 --------------| | | | | |<---180 --------------| | | | |
| | | | | | | | | | | | | |
| . . | |----INVITE------>| | | | . . | |----INVITE------>| | |
| | | timeout | | | | | | timeout | | |
| | | | | | | | | | | | | |
| | |------INVITE ------------>| | | | |------INVITE ------------>| |
|<--100 ---------------| | | | | |<--100 ---------------| | | | |
| | |<-302 --------------------| | | | |<-302 --------------------| |
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| | | | | | | | | | | | | |
| |--INVITE -------->| | | | | |--INVITE -------->| | | |
|<--100 -----| | | | | | |<--100 -----| | | | | |
| |<-302 ------------| | | | | |<-302 ------------| | | |
| | | | | | | | | | | | | |
| |-------INVITE ------------>| | | | |-------INVITE ------------>| | |
| | | | | | | | | | | | | |
| |<-------180 ---------------| | | | |<-------180 ---------------| | |
|<---180 ----| | | | | | |<---180 ----| | | | | |
| . . |-------INVITE------------->| | | | . . |-------INVITE------------->| | |
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| | timeout | | | | | | timeout | | | |
| | | | | | | | | | | | | |
| |------INVITE ---------------------->| | | |------INVITE ---------------------->| |
|<--100 -----| | | | | | |<--100 -----| | | | | |
| |<-302 ------------------------------| | | |<-302 ------------------------------| |
| | | | | | | | | | | | | |
| |-INVITE->| | | | | | |-INVITE->| | | | |
| | | | | | | | | | | | | |
| | | | | | | | | | | | | |
| | |------INVITE --------------------->| | | |------INVITE --------------------->|
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| | | | | | | | | | | | | |
| | |<-----200 OK---------------------->| | | |<-----200 OK---------------------->|
|<--200 OK-------------| | | | | |<--200 OK-------------| | | | |
| | | | | | | | | | | | | |
|--ACK --------------------------------------------------->| |--ACK --------------------------------------------------->|
| | | | | | | | | | | | | |
9.2. Voicemail 10.2 Voicemail
This scenario is as follows: This scenario is as follows:
UA 1 called UA A which had been forwarded to UA B which forwarded UA 1 called UA A which had been forwarded to UA B which forwarded
to a UA VM (voicemail server) which needs information (e.g. to a UA VM (voicemail server) which needs information (e.g.
reason the call was retargeted, original Request URI) to make a reason the call was retargeted, original Request URI) to make a
policy decision about what mailbox to use, which greeting to play policy decision about what mailbox to use, which greeting to play
etc. This scenario shows that something like the "Request etc. This scenario shows that something like the "Request
History" capability must be used for this service to function. History" capability must be used for this service to function.
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| | | | | | | | | |
| |--------INVITE ------------>| | | |--------INVITE ------------>| |
| | | | | | | | | |
| |<--------180 ---------------| | | |<--------180 ---------------| |
|<---180 ------| | | | |<---180 ------| | | |
| . . . |--------INVITE------------->| | | . . . |--------INVITE------------->| |
| | timeout | | | | timeout | |
| | | | | | | | | |
| |-------INVITE ------------------------>| | |-------INVITE ------------------------>|
| | | | | | | | | |
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| |<-200 ---------------------------------| | |<-200 ---------------------------------|
| | | | | | | | | |
|<-200---------| | | | |<-200---------| | | |
| | | | | | | | | |
|--ACK ----------------------------------------------->| |--ACK ----------------------------------------------->|
| | | | | | | | | |
| | | | | | | | | |
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SIP Generic Request History Capability - Requirements August 2002
Certainly, another valid scenario for the support of voicemail would Certainly, another valid scenario for the support of voicemail would
be that this 'policy decision' on which mailbox to use (etc.) is made be that this 'policy decision' on which mailbox to use (etc.) is made
by the UA which forwarded to voicemail (UA B), or by the Proxy which by the UA which forwarded to voicemail (UA B), or by the Proxy which
performed the forwarding on behalf of B. In this case, the UA or Proxy performed the forwarding on behalf of B. In this case, the UA or Proxy
can put all the information that the Voicemail server needs to can put all the information that the Voicemail server needs to
identity the correct mailbox, etc., into the Request-URI. This fits identity the correct mailbox, etc., into the Request-URI. This fits
with the SIP service paradigm where the Request-URI identifies the with the SIP service paradigm where the Request-URI identifies the
resource (namely, the particular mailbox/greeting etc.) that is resource (namely, the particular mailbox/greeting etc.) that is
required. required.
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their customers are using, and its capabilities. Presently, with the their customers are using, and its capabilities. Presently, with the
information loss problem, VM service providers, and any other similar information loss problem, VM service providers, and any other similar
service providers, are limited in the services they can provide service providers, are limited in the services they can provide
because they do not have complete information about how the call because they do not have complete information about how the call
reached them. They rely on the UA/proxy of their customers having the reached them. They rely on the UA/proxy of their customers having the
necessary capabilities to formulate a Request-URI identifying exactly necessary capabilities to formulate a Request-URI identifying exactly
what should happen next. Finally, there is obviously a desire to use what should happen next. Finally, there is obviously a desire to use
existing voicemail platforms based on PSTN/ISDN technology, which existing voicemail platforms based on PSTN/ISDN technology, which
operate according to the paradigm in this example. operate according to the paradigm in this example.
Watson Expires - February 2003 [Page 11] Barnes Expires - June 2003 [Page 11]
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