[Search] [txt|pdfized|bibtex] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04                                                
 Internet Draft                                      Mary Barnes,Editor
 Document: draft-ietf-sipping-req-history-01.txt            Mark Watson
                                                        Nortel Networks
                                                        Cullen Jennings
                                                                  Cisco
                                                           Jon Peterson
 Category: Informational                                        NeuStar
 Expires  June 2003                                       December 2002
 
          SIP Generic Request History Capability û Requirements
 
 Status of this Memo
 
 This document is an Internet-Draft and is in full conformance with all
 provisions of Section 10 of RFC2026.
 
 Internet-Drafts are working documents of the Internet Engineering Task
 Force (IETF), its areas, and its working groups.  Note that other
 groups may also distribute working documents as Internet-Drafts.
 
 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."
 
 The list of current Internet-Drafts can be accessed at
      http://www.ietf.org/ietf/1id-abstracts.txt
 The list of Internet-Draft Shadow Directories can be accessed at
      http://www.ietf.org/shadow.html.
 
 Abstract
 
 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 URLs on a web page,
 "call history/logging" style services within intelligent "call
 management" software for SIP UAs and calls to voicemail servers and
 call centers.  While SIP implicitly provides the redirect/retarget
 capabilities that enable calls to be routed to chosen applications,
 there is currently no standard mechanism within SIP for communicating
 the 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 draft discusses the motivations in support of a mechanism for
 recording the "request history", and proposes detailed requirements
 for such a generic "request history" capability.
 
 
 
 
 Barnes                   Expires - June 2003                [Page 1]


 SIP Generic Request History Capability - Requirements    December 2002
 
 
 Table of Contents
 
 1.   Introduction:  Why define a Generic "Request History" capability?
      2
 2.   Conventions used in this document..............................3
 3.   "Request History" Requirements.................................3
 4.   Security Considerations........................................5
 5.   Privacy Considerations.........................................6
 6.   IANA Considerations............................................6
 7.   References.....................................................6
 8.   Contributors...................................................6
 9.   Acknowledgments................................................7
 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?
 
    SIP implicitly provides redirect/retarget capabilities that enable
    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
    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
    associating this request history only with the specific SIP
    Redirect Server capability that provides for a response to be sent
    back to a UAC requesting that the UAC should retarget the original
    request to an alternate URI.  The rules for determining request
    targets as described in section 16.5 of [1] are consistent with the
    use of the retarget term in this draft.
 
    The motivation for the request history is that in the process of
    retargeting 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. The proposal in this draft is to
    provide a mechanism for transporting the request history.  It is
    not proposing any behavior for a Proxy or UA upon receipt of the
    information. Indeed, such behavior should be a local decision for
    the recipient application.
 
    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
 
 
 Barnes                   Expires - June 2003                [Page 2]


 SIP Generic Request History Capability - Requirements    December 2002
 
 
       arrived at the site via an "associate" site which 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 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:
 
    4. Some diagnostic information for debugging SIP requests.
 
    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
 
    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.
 
 
 3. "Request History" Requirements
 
    The following list constitutes a set of requirements for a "Request
    History" capability. It is anticipated that some of these
    requirements can be met using existing elements within SIP; whether
    and what SIP extensions would be needed to meet these requirements
    is out of scope of this draft.
 
 
 
 Barnes                   Expires - June 2003                [Page 3]


 SIP Generic Request History Capability - Requirements    December 2002
 
 
    1) CAPABILITY-req:  The "Request History" capability will provide a
    capability to inform proxies and UAs involved in processing a
    request about the history/progress of that request. While 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) OPTIONALITY-req: The "Request History" information is optional.
 
    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
    the specific application, thus no specific protocol element is
    needed.
 
    2.2) Due to the capability being "optional" from the SIP protocol
    perspective, the impact to an application of not having the
    "Request History" must be described. Applicability guidelines to be
    addressed by applications using this capability must be provided as
    part of the solution to these requirements.
 
 
    3) GENERATION-req: "Request History" information is generated when
    the request is retargeted.
 
    3.1) 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'.
 
    3.2) 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.
 
 
    4) ISSUER-req: "Request History" information can be generated by a
    UA, proxy or redirect server. It can be passed in both requests and
    responses.
 
 
    5) CONTENT-req:  The "Request History" information for each
    occurrence of retargeting, shall include the following:
 
      5.1) The new URI or address to which the request is in the
    process of being retargeted,
 
      5.2) The URI or address from which the request was retargeted,
 
      5.3) The reason for the Request-URI modification,
 
 
 
 Barnes                   Expires - June 2003                [Page 4]


 SIP Generic Request History Capability - Requirements    December 2002
 
 
      5.4) Chronological ordering of the Request History information.
 
    6) REQUEST-VALIDITY-req:  Request-History is applicable to requests
    not sent within an established dialog. (i.e. INVITE, REGISTER,
    MESSAGE, and OPTIONS).
 
    7) 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.
 
    8) FORWARDS-req:  Request-History information may also be included
    by the generating entity in the request, if it is forwarded
    onwards.
 
 
 4. Security Considerations
 
    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) Loss of privacy associated with forwarding a specific Request
    URI in the Request History.
 
    3) 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.
 
    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.
 
 
 
 Barnes                   Expires - June 2003                [Page 5]


 SIP Generic Request History Capability - Requirements    December 2002
 
 
    3) SEC-req-3: The entity receiving the information conveyed by the
    Request History must be able to authenticate the source of the
    information.
 
    4) SEC-req-4: To ensure the confidentiality of the Request History
    information, only entities which 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, either by
    retargeting and capturing the information, or as an application
    making use of the information in a Request or Response.
 
 5.Privacy Considerations
 
    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 [2])
    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.
 
    It is recognized that meeting the privacy requirements can impact
    the functionality of this solution by overriding the request to
    generate the information. The applicability guidelines for a
    solution must clearly address this impact.
 
 
 6.IANA Considerations
 
    This document does not have any implications for IANA.
 
 7.References
 
    [1] J. Rosenberg et al, "SIP: Session initiation protocol," RFC
    3261, June, 2002.
 
    [2] J. Peterson, "A Privacy Mechanism for the Session Initiation
    Protocol (SIP)", RFC 3323, November, 2002.
 
 
 8. Contributors
 
      Robert Sparks contributed excellent feedback and direction for
      the Security considerations section of this document.  In
 
 
 Barnes                   Expires - June 2003                [Page 6]


 SIP Generic Request History Capability - Requirements    December 2002
 
 
      addition, he highlighted the importance of addressing the
      optionality aspects of the "Request History" capability.
 
 9. Acknowledgments
 
      The editor would like to thank Sanjoy Sen, Ben Campbell, Rohan
      Mahy and Jonathan Rosenberg for providing useful comments and
      suggestions related to this draft.
 
 
 AuthorsÆ Addresses
 
    Mark Watson
    Nortel Networks (UK)
    Maidenhead Office Park (Bray House)
    Westacott Way
    Maidenhead,
    Berkshire                        Tel: +44 (0)1628-434456
    England                       Email:  mwatson@nortelnetworks.com
 
    Mary Barnes
    Nortel Networks               Tel: +1 972-684-5432
    Richardson, Texas             Email:  mbarnes@nortelnetworks.com
 
    Jon Peterson
    NeuStar, Inc.
    1800 Sutter Street, Suite 570
    Concord, CA 94520             Email: Jon.Peterson@NeuStar.com
 
    Cullen Jennings
    Cisco Systems
    170 West Tasman Dr               Tel: +1 408 527 9132
    MS: SJC-21/3                     Email: fluffy@cisco.com
 
 Full Copyright Statement
 
    Copyright (C) The Internet Society (2002).  All Rights Reserved.
 
    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
 
 
 Barnes                   Expires - June 2003                [Page 7]


 SIP Generic Request History Capability - Requirements    December 2002
 
 
    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."
 
 
 10. Appendix A - Scenarios
 
    This section highlights some scenarios under which the Request
    History Capability could be applicable.
 
    Certainly, various other solutions can be applied in some fashion
    to each of these scenarios.  However, the objective of this draft
    has been to abstract the requirements from these scenarios towards
    providing a more robust solution for each and at the same time
    providing fundamental building block(s) applicable to future
    applications.
 
      10.1 Sequentially forking with Retargeting
 
    This scenario is as follows:
 
      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.
      Proxy 2 unfortunately tries several of the same places (UA3 and
      UA4), before completing at UA5.
 
 
    UA1        Proxy1  Proxy2     UA2      UA3      UA4      UA5
 
    |            |         |        |        |        |        |
    |--INVITE -->|         |        |        |        |        |
    |            |         |        |        |        |        |
    |            |--INVITE -------->|        |        |        |
    |<--100 -----|         |        |        |        |        |
    |            |<-302 ------------|        |        |        |
    |            |         |        |        |        |        |
    |            |-------INVITE ------------>|        |        |
    |            |         |        |        |        |        |
    |            |<-------180 ---------------|        |        |
    |<---180 ----|         |        |        |        |        |
 
 
 Barnes                   Expires - June 2003                [Page 8]


 SIP Generic Request History Capability - Requirements    December 2002
 
 
    |  . .       |-------INVITE------------->|        |        |
    |            |       timeout    |        |        |        |
    |            |         |        |        |        |        |
    |            |------INVITE ---------------------->|        |
    |<--100 -----|         |        |        |        |        |
    |            |<-302 ------------------------------|        |
    |            |         |        |        |        |        |
    |            |-INVITE->|        |        |        |        |
    |            |         |        |        |        |        |
    |            |         |---INVITE ------>|        |        |
    |            |         |        |        |        |        |
    |            |         |<---180----------|        |        |
    |<---180 --------------|        |        |        |        |
    |            |         |        |        |        |        |
    |  . .       |         |----INVITE------>|        |        |
    |            |         |      timeout    |        |        |
    |            |         |        |        |        |        |
    |            |         |------INVITE ------------>|        |
    |<--100 ---------------|        |        |        |        |
    |            |         |<-302 --------------------|        |
    |            |         |        |        |        |        |
    |            |         |------INVITE --------------------->|
    |            |         |        |        |        |        |
    |            |         |<-----200 OK---------------------->|
    |<--200 OK-------------|        |        |        |        |
    |            |         |        |        |        |        |
    |--ACK --------------------------------------------------->|
    |            |         |        |        |        |        |
 
 
    This scenario is provided to show the duplication of messaging when
    there isnÆt sufficient knowledge to optimize a sequential attempt
    at reaching an end user.  With the "Request History" capability,
    this flow could be optimized as follows:
 
    UA1        Proxy1  Proxy2     UA2      UA3      UA4      UA5
 
    |            |         |        |        |        |        |
    |--INVITE -->|         |        |        |        |        |
    |            |         |        |        |        |        |
    |            |--INVITE -------->|        |        |        |
    |<--100 -----|         |        |        |        |        |
    |            |<-302 ------------|        |        |        |
    |            |         |        |        |        |        |
    |            |-------INVITE ------------>|        |        |
    |            |         |        |        |        |        |
    |            |<-------180 ---------------|        |        |
    |<---180 ----|         |        |        |        |        |
    |  . .       |-------INVITE------------->|        |        |
 
 
 Barnes                   Expires - June 2003                [Page 9]


 SIP Generic Request History Capability - Requirements    December 2002
 
 
    |            |       timeout    |        |        |        |
    |            |         |        |        |        |        |
    |            |------INVITE ---------------------->|        |
    |<--100 -----|         |        |        |        |        |
    |            |<-302 ------------------------------|        |
    |            |         |        |        |        |        |
    |            |-INVITE->|        |        |        |        |
    |            |         |        |        |        |        |
    |            |         |        |        |        |        |
    |            |         |------INVITE --------------------->|
    |            |         |        |        |        |        |
    |            |         |<-----200 OK---------------------->|
    |<--200 OK-------------|        |        |        |        |
    |            |         |        |        |        |        |
    |--ACK --------------------------------------------------->|
    |            |         |        |        |        |        |
 
 
      10.2 Voicemail
 
    This scenario is as follows:
 
      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.
      reason the call was retargeted, original Request URI) to make a
      policy decision about what mailbox to use, which greeting to play
      etc. This scenario shows that something like the "Request
      History" capability must be used for this service to function.
 
 UA1          Proxy           UA-A         UA-B        UA-VM
 
 |              |              |             |          |
 |--INVITE ---->|              |             |          |
 |              |              |             |          |
 |              |--INVITE ---->|             |          |
 |<--100 -------|              |             |          |
 |              |<-302 --------|             |          |
 |              |              |             |          |
 |              |--------INVITE ------------>|          |
 |              |              |             |          |
 |              |<--------180 ---------------|          |
 |<---180 ------|              |             |          |
 |  . . .       |--------INVITE------------->|          |
 |              |        timeout             |          |
 |              |              |             |          |
 |              |-------INVITE ------------------------>|
 |              |              |             |          |
 
 
 Barnes                   Expires - June 2003               [Page 10]


 SIP Generic Request History Capability - Requirements    December 2002
 
 
 |              |<-200 ---------------------------------|
 |              |              |             |          |
 |<-200---------|              |             |          |
 |              |              |             |          |
 |--ACK ----------------------------------------------->|
 |              |              |             |          |
 |              |              |             |          |
 
 
 Certainly, another valid scenario for the support of voicemail would
 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
 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
 identity the correct mailbox, etc., into the Request-URI. This fits
 with the SIP service paradigm where the Request-URI identifies the
 resource (namely, the particular mailbox/greeting etc.) that is
 required.
 
 However, whilst this model is certainly applicable and required in
 SIP, it places service intelligence away from the system providing the
 key aspect of the service (the VM server).
 
 The proposal in this draft is to rely on generic information-providing
 capabilities in the UA/Proxy, allowing the Voicemail system to provide
 more and better voicemail-related services without relying on specific
 capabilities in the UA/Proxy. This would allow voicemail service
 providers to innovate independently of the particular UA/Proxy that
 their customers are using, and its capabilities. Presently, with the
 information loss problem, VM service providers, and any other similar
 service providers, are limited in the services they can provide
 because they do not have complete information about how the call
 reached them. They rely on the UA/proxy of their customers having the
 necessary capabilities to formulate a Request-URI identifying exactly
 what should happen next. Finally, there is obviously a desire to use
 existing voicemail platforms based on PSTN/ISDN technology, which
 operate according to the paradigm in this example.
 
 
 
 
 
 
 
 Barnes                   Expires - June 2003               [Page 11]