Network Working Group M. Mohali Internet-Draft France Telecom Intended status: Informational June 24, 2009 Expires: December 26, 2009 Mapping and interworking of Diversion information Between Diversion and History-Info Headers in the Session Initiation Protocol (SIP) draft-mohali-diversion-history-info-04 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. 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. This Internet-Draft will expire on December 26, 2009. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Mohali Expires December 26, 2009 [Page 1] Internet-Draft Mapping Diversion and History-Info June 2009 Abstract The Diversion header is not standardized but widely used to convey diverting information in Session Initiation Protocol (SIP) signaling. This informational document proposes a way to interwork call diversion information contained in Diversion header with a History- Info header. In addition, an interworking policy is proposed to manage the headers coexistence. The History-Info header is described in [RFC4244] and the Diversion header is described in [draft-levy-sip-diversion-09]. Note to the RFC-Editor: The reference to this draft should be replaced by the Historic RFC reference (work in progress). Since the Diversion header is used in many existing networks implementations for transport of diversion information and its interworking with standardized solutions is not obvious, an interworking recommendation is needed. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Mohali Expires December 26, 2009 [Page 2] Internet-Draft Mapping Diversion and History-Info June 2009 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Background . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Interworking requirements and scope . . . . . . . . . . . 5 2.2. Interworking recommendations . . . . . . . . . . . . . . . 6 2.2.1. SIP network/terminal using Diversion to SIP network/terminal using History-Info header . . . . . . 7 2.2.2. SIP network/terminal using History-Info header to SIP network/terminal using Diversion header . . . . . 8 3. Headers syntaxes reminder . . . . . . . . . . . . . . . . . . 9 3.1. History-Info header syntax . . . . . . . . . . . . . . . . 9 3.2. Diversion header syntax . . . . . . . . . . . . . . . . . 11 4. Headers in SIP Method . . . . . . . . . . . . . . . . . . . . 12 5. Diversion header to History-Info header . . . . . . . . . . . 13 6. History-Info header to Diversion header . . . . . . . . . . . 16 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7.1. Example with Diversion header changed into History-Info header . . . . . . . . . . . . . . . . . . . 17 7.2. Example with History-Info header changed into Diversion header . . . . . . . . . . . . . . . . . . . . . 17 7.3. Example with two SIP networks using History-Info header interworking with a SIP network using Diversion header . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7.4. Additional interworking Cases . . . . . . . . . . . . . . 19 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20 10. Acknowlegements . . . . . . . . . . . . . . . . . . . . . . . 21 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21 11.1. Normative References . . . . . . . . . . . . . . . . . . . 21 11.2. Informative References . . . . . . . . . . . . . . . . . . 22 Appendix A. Interworking between Diversion header and Voicemail URI . . . . . . . . . . . . . . . . . . . . 22 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 23 Mohali Expires December 26, 2009 [Page 3] Internet-Draft Mapping Diversion and History-Info June 2009 1. Introduction 1.1. Overview For some network services (eg. Voicemail, IVR or automatic call distribution), it is helpful for the called SIP user agent to identify from whom and why the session was diverted. For this information to be used in various service providers or by various applications, this redirection information needs to pass through the network. This is possible with two different SIP headers: History-Info header [RFC4244] and Diversion header which are both able to transport diversion information in SIP signaling. Although the Diversion header is not standardized, it is widely used. Therefore, it is useful to have guidelines to make this header interwork with the standard History-Info header. This document provides a mechanism of translation between the Diversion header and the History-Info header. 1.2. Background The History-Info header [RFC4244] and the URI extension (including Voicemail URI) [RFC4458] are recommended by IETF to convey redirection information. They are also recommended in the "Communication Diversion (CDIV) service" 3GPP specification [TS_24.604]. At first, the Diversion header was described in [draft-levy-sip-diversion-09], which is today discarded. Note to the RFC-Editor: The reference to this draft should be replaced by the Historic RFC reference (work in progress). This header contains a list of the diverting URIs with associated information providing specific information as to why a call was diverted. Most of implementations have implemented the Diversion header when the History-Info header was not a standard. The IETF has chosen to standardize the History-Info header in part because it can transport general "request history" information which allows the receiving application to determine how and why the session arrived at the application/user. As History-Info header information is larger than call diversion information, it is really important to be sure of not losing information and be able to extract the relevant data using the retargeting cause URI parameter described in [RFC4458] for the transport of the diversion reason. Those headers have different syntaxes described below. Note that the main difference is that the History-Info header is a chronological writing header whereas the Diversion header is the opposite (i.e. the first diversion entry read correspond to the last diverting user). Mohali Expires December 26, 2009 [Page 4] Internet-Draft Mapping Diversion and History-Info June 2009 The Appendix provides an interworking guideline between the Diversion header and the Voicemail URI which is another way to convey diversion information described in [RFC4458]. 2. Problem Statement 2.1. Interworking requirements and scope This section provides the baseline terminology used in the rest of the document and defines the scope of interworking between these two headers that need to be addressed. They are many ways in which SIP signaling can be used to modify a session destination before it is established and many reasons for doing so. The behavior of the SIP entities that will have to further process the session downstream will sometimes vary depending on the reasons that lead to changing the destination, for example whether it is for simple proxy to route the session or for an application server to provide a supplementary service. The approach and scope in which the Diversion header and the History- Info header address this problem are different. For clarity, the following vocabulary is used in this document: Retargeting/redirecting: Retargeting/redirecting refer to the process of a Proxy Server/User Agent Client (UAC) changing a Uniform Resource Identifier (URI) in a request and thus changing the target of the request. These terms are defined in [RFC4244]. The History-Info header is used to store retargeting information. Call forwarding/call diversion/communication diversion: These terms are equivalent and refer to the Communications Diversion (CDIV) supplementary services, based on the ISDN Communication diversion supplementary services and defined in 3GPP [TS_24.604]. They are applicable to entities which are intended to modify the original destination of an IP multimedia session prior to or during the session establishment. This document does not describe when or how History-Info or Diversion headers are used. The following is offered to clarify the context in which this interworking is used. The History-Info header is used in practice to convey call diversion related information by using a cause URI parameter [RFC4458] in the relevant entry. Mohali Expires December 26, 2009 [Page 5] Internet-Draft Mapping Diversion and History-Info June 2009 The Diversion header has exactly the same scope as the call diversion service and each header entry reflects a call diversion invocation. The Diversion header is used for recording communication diversion information which could be useful to network entities downstream. Today, this SIP header is implemented by several manufacturers and deployed in several networks. The History-Info header is used to store all retargeting information including call diversion information. Note, however, that the use of cause URI parameter [RFC4458] in a History-Info entry for a call diversion is specific to the 3GPP specifications. RFC4458 focuses on retargeting toward voicemail server and does not specify whether the cause URI parameter should be added or not in a URI for other cases. As a consequence, implementations that do not use the cause URI parameter for call forwarding information, are not considered for the mapping described in this document. Nevertheless, some recommendations are given in the next sections on how not to lose non-mapped information at the boundary between a network region using History-Info header and one using the Diversion header. Since both headers addresses call forwarding needs, diverting information could be mixed-up or be inconsistent if both headers are present in an uncoordinated fashion in the INVITE request. So, Diversion and History-Info headers MUST NOT independently coexist for the session signaling. This specific address how to convert information between the two, and when and how to preserve both headers to cover additional cases. For the transportation of consistent diversion information downstream, it is necessary to make the two headers interwork. Interworking between the Diversion header and the History-Info header is introduced in sections 5 and 6. Since coexistence scenario may vary from one use case to another, guidelines regarding headers interaction are proposed. 2.2. Interworking recommendations Interworking function: In a normal case, the network topology assumption is that the interworking described in this document should be performed by a specific SIP border device which by configuration is aware that it is at the border between two regions, one using History-Info header and one using Diversion header. History-Info header is a standardized solution, so a network using the Diversion header MUST be able to provide information to a network Mohali Expires December 26, 2009 [Page 6] Internet-Draft Mapping Diversion and History-Info June 2009 using the History-Info header. In this case, to avoid both headers coexistence it is recommended as often as possible to replace the Diversion header with the History-Info header in the INVITE request during the interworking. Since, the History-Info header has a boarder scope than the Diversion header and may be used for services other than call diversion. In addition to tracing call diversion information, History-Info header also acts as a session history and could store all successive R-URI values. Consequently, even if it should be better to remove the History-Info header after the Diversion header has been created to avoid any confusion; if the History-Info header contains supplementary (non-diversion) information it MUST be retained as is and passed transparently in this network. It is possible to have History-Info headers that do not have values that can be mapped into the Diversion header. In this case, no interworking with Diversion header should be performed and implementations will have to decide what to do. This point is out of this document scope. As a conclusion, it is recommended to have local policies minimizing the loss of information and find the best way to keep it up to the terminating user agent. This section describes the basic and commonly used use case. More unusual interworking cases, are described in section 7.5. 2.2.1. SIP network/terminal using Diversion to SIP network/terminal using History-Info header When the Diversion header is used to create a History-Info header, the Diversion header MUST be removed in the outgoing INVITE. It is considered that all information present in the Diversion header is transferred in the History-Info header. If a History-Info header is present in the incoming INVITE (in addition to Diversion header), the Diversion header and History-Info header present MUST be mixed and only the diversion information not yet present in the History-Info header MUST be inserted as a last entry (more recent) in the existing History-Info header as recommended in [RFC4244]. As an example, this could be the case of an INVITE coming from network_2 using Diversion header but has previously passed through network_1 using History-Info header (or the network_2 uses History- Info header to transport successive URI information) and going to network_3 using History-Info header. Mohali Expires December 26, 2009 [Page 7] Internet-Draft Mapping Diversion and History-Info June 2009 IWF* IWF* network1 | network_2 |network_3 History-Info | Diversion |using | |Hist-Info | | UA A P1 AS B | P2 AS C UA C AS D | UA E | | | | | | | | | | |INVITE | | | | | | | | | |------>| | | | | | | | | | | | | | | | | | | | |INVITE | | | | | | | | | |------>| | | | | | | | | |Supported: histinfo | | | | | | | | History-Info: | | | | | | | | ; index=1, | | | | | | | ; index=1.1 | | | | | | | | | | | | | | | | | |INVITE | | | | | | | | | |------>| | | | | | | | | |History-Info: | | | | | | | | |; index=1,| | | | | | | |; index=1.1 | | | | | | | |; cause=302; index=1.1.1 | | | In this case, the incoming INVITE contains a Diversion header and a History-Info header. So that, it is necessary to create, for network_3, a single History-Info header gathering existing information from both the History-Info and the Diversion headers received. Then network_3 could use call forwarding information that is present in a single header and add its own diversion information if necessary. Note: if a network is not able either to use only one header each time, or to maintain both headers up to date, the chronological order could not be certified. Note: it is not possible to have only Diversion header when the History-Info header contains more than call diversion information. If previous policy recommendations are applied, the chronological order is respected as Diversion entries are inserted at the end of the History-Info header taking into account the Diversion internal chronology. 2.2.2. SIP network/terminal using History-Info header to SIP network/ terminal using Diversion header When the History-Info header is interpreted to create a Diversion header, some precautions MUST be taken. If the History-Info header contains only communication diversion Mohali Expires December 26, 2009 [Page 8] Internet-Draft Mapping Diversion and History-Info June 2009 information, then it MUST be suppressed after the interworking. If the History-Info header contains other information, then only the information of concern to the diverting user MUST be used to create entries in the Diversion header and the History-Info header MUST be kept as received in the INVITE and forwarded downstream. Note: The History-Info header could be used for other reasons than CDIV services, for example by a service which need to know if a specific AS had yet been invoked in the signaling path. If the call is later forwarded to a network using History-Info header, it would be better to not lose history information due to passing though the network which only support Diversion header. A recommended solution MUST NOT disrupt the standard behavior and networks which do not implement the History-Info header MUST be transparent to a received History-Info header. If a Diversion header is present in the incoming INVITE (in addition to History-Info header), only diversion information present in the History-Info header but not in the Diversion header MUST be inserted from the last entry (more recent) into the existing Diversion header as recommended in the Diversion draft [draft-levy-sip-diversion-09]. Note to the RFC-Editor: The reference to this draft should be replaced by the Historic RFC reference (work in progress). Note that the chronological order could not be certified. If previous policy recommendations are respected, this case SHOULD NOT happen. Forking case: The History-Info header enables the recording of sequential forking for the same served-user. During a interworking from the History- Info header to Diversion header, the History-Info entries containing a forking situation (with an incremented "index" parameter) could be either mapped for each entry with a call forwarding "cause" parameter, the interworking entity could choose to create only one Diversion entry or to not apply the interworking. The choice could be done according a local policy. The same logic is applied for an interworking with Voicemail URI (see the Appendix). 3. Headers syntaxes reminder 3.1. History-Info header syntax History-Info = "History-Info" HCOLON hi-entry *(COMMA hi-entry) hi-entry = hi-targeted-to-uri *( SEMI hi-param ) Mohali Expires December 26, 2009 [Page 9] Internet-Draft Mapping Diversion and History-Info June 2009 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 The History-Info header is specified in [RFC4244]. The top-most History-Info entry (first in the list) corresponds to the oldest history information. A hi-entry may contain a cause URI parameter expressing the diversion reason. This optional cause URI parameter is defined in [RFC4458] with the following syntax: cause-param = "cause" EQUAL Status-Code. This parameter is also named cause-param and should be inserted in the History-Info entry (URI) of the diverted-to user in case of call diversion as recommended in the 3GPP CDIV specification [TS_24.604]. The cause values used in the cause- param for the diverting reason are listed in the RFC and because it is a parameter dedicated to call forwarding service, its presence is used to determine that a hi-entry is a diverting user. More exactly, each diverting user is located in the hi-entry before the one containing a cause-param with cause value as listed in RFC 4458. Moreover, the Reason header defined in [RFC3326]SHOULD be escaped in the hi-entry of the diverting user when the call diversion is due to a SIP response received. The Reason header contains a cause parameter set to the true SIP response code received (Status-Code). Therefore, in case of call diversion due to a SIP response, both cause parameters should be used. The complexity is that these parameters could be used at the same time in the History-Info header but not in the same hi-entry and not with the same meaning. Only the cause-param is dedicated to call diversion service. The 'cause' Reason header parameter is not taken into account in the mapping with a Diversion header. [RFC4458] also defines the 'target' URI parameter which could be inserted in a R-URI and consequently in the hi-targeted-to-uri. This parameter is used to keep the diverting user address in the downstream INVITE request in Voicemail URI implementation. As this information is yet present in the hi-entries, the 'target' URI parameter is not taken into account regarding the interworking with the Diversion header. From the Diversion header, it could be possible to create the 'target' URI parameter in the hi-entries and/or in the R-URI but this possibility is on local policies responsabilty and not described in this document. A Privacy header as defined in [RFC3323] could also be included in hi-entries with the 'history' value defined in the RFC4244. The index parameter is a string of digits, separated by dots to Mohali Expires December 26, 2009 [Page 10] Internet-Draft Mapping Diversion and History-Info June 2009 indicate the number of forward hops and retargets. first one is Note: A history entry could contain the "gr" parameter. Regardless the rules concerning "gr" parameter defined in [TS_24.604] which must be applied, this parameter has no impact on the mapping and must only be copied with the served user address. Example: History-Info: ;index=1, ;index=1.1, ; index=1.1.1, Policy concerning "histinfo" option tag in Supported header: According to [RFC4244], a proxy that receives a Request with the "histinfo" option tag in the Supported header should return captured History-Info in subsequent, provisional and final responses to the Request. The behavior depends upon whether the local policy supports the capture of History-Info or not. 3.2. Diversion header syntax The current document is not written to define again the Diversion header and its use but to be sure that the syntax is interpreted in the same way by everyone. So that, the Diversion syntax is here a little changed to correspond to the current ABNF [RFC4234]: Diversion = "Diversion" HCOLON diversion-params *(COMMA diversion- params) diversion-params = name-addr *(SEMI (diversion-reason / diversion- counter / diversion-limit / diversion-privacy / diversion-screen / diversion-extension)) diversion-reason = "reason" EQUAL ("unknown" / "user-busy" / "no- answer" / "unavailable" / "unconditional" / "time-of-day" / "do-not- disturb" / "deflection" / "follow-me" / "out-of-service" / "away" / token / quoted-string) diversion-counter = "counter" EQUAL 1*2DIGIT diversion-limit = "limit" EQUAL 1*2DIGIT diversion-privacy = "privacy" EQUAL ("full" / "name" / "uri" / "off" / token / quoted-string) diversion-screen = "screen" EQUAL ("yes" / "no" / token / quoted- string) Mohali Expires December 26, 2009 [Page 11] Internet-Draft Mapping Diversion and History-Info June 2009 diversion-extension = token [EQUAL (token / quoted-string)] Note: The Diversion header could be used in the comma-separated format as described below and in a header-separated format. Both formats could be combined a received INVITE as RECOMMENDED in [RFC3261]. Example: Diversion: diverting_user2_addr; reason="user-busy"; counter=1; privacy=full, diverting_user1_addr; reason="unconditional"; counter=1; privacy=off 4. Headers in SIP Method You can find here a reminder of History-Info header field and Diversion header field in relation to methods. As those headers do not have the same capabilities, it is necessary to clarify the interworking. Use of History-Info header field: Header field where proxy ACK BYE CAN INV OPT REG MSG ------------ ----- ----- --- --- --- --- --- --- --- History-Info amdr - - - o o o o SUB NOT REF INF UPD PRA PUB --- --- --- --- --- --- --- History-Info amdr o o o - - - o Use of Diversion header field: Header field where enc. e-e ACK BYE CAN INV OPT REG ------------ ----- ----- --- --- --- --- --- --- --- Diversion R h - - - o - - Diversion 3xx h - - - o - - The recommended interworking presented in this document SHOULD apply only for INVITE requests. In 3xx responses, both headers could be present. When a proxy wants to interwork with a network supporting the other header field, it SHOULD apply the interworking between Diversion Mohali Expires December 26, 2009 [Page 12] Internet-Draft Mapping Diversion and History-Info June 2009 header and History-Info header in the 3xx response. When a recursing proxy redirects an initial INVITE after receiving a 3xx response, it SHOULD add as a last entry either a Diversion header or History-Info header (according to its capabilities) in the forwarded INVITE. Local policies could apply to send the received header in the next INVITE or not. Other messages where History-Info could be present are not used for the Call Forwarding service and SHOULD NOT be changed into Diversion header. The destination network MUST be transparent the received History-Info header. Note : the following mapping is inspired from the ISUP to SIP interworking described in [TS_29.163]. 5. Diversion header to History-Info header The following text is valid only if no History-Info is present in the INVITE request. If at least one History-Info header is present, the interworking function shall adapt its behavior to respect the chronological order. See section 2.2. For N Diversion entries N+1 History-Info entries MUST be created. To create the History-Info entries in the same order than during a session establishment, the Diversion entries MUST be mapped from the bottom-most until the top-most. Each Diversion entry shall be mapped into a History-Info entry. An additional (the last one) History-Info entry must be created with the diverted-to party address present in the R-URI of the received INVITE, The mapping is described below. The first entry created in the History-Info header contains: - a hi-target-to-uri with the name-addr parameter of the bottom- most Diversion header - if a privacy parameter is present in the bottom-most Diversion entry, then a Privacy header could be escaped in the History-Info header as described below, - an index set to 1. For each following Diversion entry (from bottom to top), the History- info entries are created as following (from top to bottom): Mohali Expires December 26, 2009 [Page 13] Internet-Draft Mapping Diversion and History-Info June 2009 Source Destination Diversion header component: History-Info header component: ======================================================================= Name-addr Hi-target-to-uri ======================================================================= Reason of the previous cause-param (not present in Diversion entry the first created hi-entry) "unknown"---------------------------------404 (default 'cause' value) "unconditional"---------------------------302 "user-busy"-------------------------------486 "no-answer"-------------------------------408 "deflection "-----------------------------480 or 487 "unavailable"-----------------------------404 "time-of-day"-----------------------------404 (default) "do-not-disturb"--------------------------404 (default) "follow-me"-------------------------------404 (default) "out-of-service"--------------------------404 (default) "away"------------------------------------404 (default) ======================================================================= Counter Hi-index "1" or parameter -------------------------The previous created index no present is incremented with ".1" Superior to "1" --------------------------Create N-1 placeholder History (i.e. N) entry with the previous index incremented with ".1" Then the History-Info header created with the Diversion entry with the previous index incremented with ".1" ======================================================================= Privacy Privacy header escaped in the hi-targeted-to-uri "full"------------------------------------"history" "Off"-------------------------------------Privacy header field absent or "none" "name"------------------------------------"history" "uri"-------------------------------------"history" ======================================================================= A last History-Info entry is created and contains: - a hi-target-to-uri with the Request-URI of the INVITE request. - a cause-param from the top-most Diversion entry, mapped from the diversion-reason as described above. Mohali Expires December 26, 2009 [Page 14] Internet-Draft Mapping Diversion and History-Info June 2009 - if a privacy parameter is present in the top-most Diversion entry, then a Privacy header could be escaped in the History-Info header as described above, - an index set to the previous created index and incremented with ".1" Note: For other optional Diversion parameters, there is no recommendation as History-Info header does not provide equivalent parameters. Note: For values of the diversion-reason values which are mapped with a recommended default value, it could also be possible to choose another value. The cause-param URI parameter offers less possible values than the diversion-reason parameter. However, it has been considered that cause-param values list was sufficient to implement CDIV service as defined in 3GPP as it cover a large portion of cases. Note : The Diversion header could contain a Tel:URI in the name-addr parameter but it seems to not be possible to have a Tel:URI in the History-Info header. RFC3261 gives an indication as to the mapping between sip: and tel: URIs but in this particular case it is difficult to assign a valid hostport as the diversion has occurred in a previous network and a valid hostport is difficult to determine. So, it is suggested that in case of Tel:URI in the Diversion header, the History-Info header should be created with a SIP URI with user=phone. Note: The Diversion header allows the carrying of a counter which had retained the information about the number of redirections which have occurred. History-Info does not have an equivalent because to trace and count diversion occurred it is necessary to count cause parameter containing a value associated to a call diversion. To read the index value is not enough. With the use of the "placeholder" entry the History-info header entries could reflect the real number of diversion occurred. Example of placeholder entry in the History-Info header: ;index=1.1 ;index=1.1.1 cause=xxx reflects the diverting reason of a previous diverting user. For a placeholder hi-entry the value "404" shall be taken for the cause-param and so, located in the next hi-entry. Concerning local policies recommendations about headers coexistence in the INVITE request, see sections 2.2 and 7.5. Mohali Expires December 26, 2009 [Page 15] Internet-Draft Mapping Diversion and History-Info June 2009 6. History-Info header to Diversion header To create the Diversion entries in the same order than during a session establishment, the History-Info entries MUST be mapped from the top-most until the bottom-most. The first History-Info header entry selected will be mapped into the last Diversion header entry and so on. One Diversion header entry MUST be created for each History-Info entry with a cause-param reflecting a diverting reason as listed in the [RFC4458]. In this case, the History-Info header MUST be mapped into the Diversion header as following: Source Destination History-Info header component: Diversion header component: ===================================================================== Hi-target-to-uri of the Name-addr History-Info which precedes the one containing a diverting cause-param ===================================================================== Cause-param Reason 404---------------------------------------"unknown" (default value) 302---------------------------------------"unconditional" 486---------------------------------------"user-busy" 408---------------------------------------"no-answer" 480 or 487--------------------------------"deflection " 503---------------------------------------"unavailable" ===================================================================== Hi-index Counter Mandatory parameter for--------------------The counter is set to "1". History-Info reflecting the chronological order of the information. ===================================================================== Privacy header [RFC3323]escaped in the Privacy hi-targeted-to-uri of the History-Info which precedes the one containing a diverting cause-param. Optional parameter for History-Info, this Privacy indicates that this specific History-Info header SHOULD not be forwarded. "history"----------------------------------"full" Privacy header field ----------------------"Off" Absent or "none" Mohali Expires December 26, 2009 [Page 16] Internet-Draft Mapping Diversion and History-Info June 2009 ===================================================================== Note: For other optional History-Info parameters, there is no recommendation as Diversion header does not provide equivalent parameters. Concerning local policies recommendations about headers coexistence in the INVITE request, see section 2.2. 7. Examples 7.1. Example with Diversion header changed into History-Info header INVITE last_diverting_target Diversion: diverting_user3_address;reason=unconditional;counter=1;privacy=off, diverting_user2_address;reason=user-busy;counter=1;privacy=full, diverting_user1_address;reason=no-answer;counter=1;privacy=off Mapped into: History-Info: ; index=1, ;index=1.1, ;index=1.1.1, ;index=1.1.1.1, 7.2. Example with History-Info header changed into Diversion header History-Info: ; index=1, ;index=1.1, ;index=1.1.1 Mapped into: Diversion: diverting_user2_address; reason=user-busy; counter=1; privacy=off, diverting_user1_address; reason=unconditional; counter=1; privacy=full 7.3. Example with two SIP networks using History-Info header interworking with a SIP network using Diversion header A -> P1 -> B -> C -> P2 -> D-> E Mohali Expires December 26, 2009 [Page 17] Internet-Draft Mapping Diversion and History-Info June 2009 A, B, C, D and E are users. B, C and D have Call Forwarding service invoked. P1 and P2 are proxies. Only relevant information is shown on the following call flow. IWF* IWF* SIP network using | SIP network using |SIP net. History-Info | Diversion |using | |Hist-Info | | UA A P1 AS B | P2 AS C UA C AS D | UA E | | | | | | | | | | |INV B | | | | | | | | | |------>| | | | | | | | | | | | | | | | | | | | |INV B | | | | | | | | | |------>| | | | | | | | | |Supported: histinfo | | | | | | | | History-Info: | | | | | | | | ; index=1, | | | | | | | ; index=1.1 | | | | | | | | | | | | | | | | | |INV C | | | | | | | | | |------>| | | | | | | | | |History-Info: | | | | | | | | |; index=1,| | | | | | | |; index=1.1 | | | | | | | |; index=1.1.1 | | | | | | | | | | | | | | | | |INV C | | | | | | | | | |------>| | | | | | | | | |Diversion: | | | | | | | | |B reason= unconditional counter=1 | | | | | |History-Info: | | | | | | | | |; index=1,| | | | | | | |; index=1.1 | | | | | | | |; index=1.1.1| | | | | | | | | | | | | | | | |INV C | | | | | | | | | |------>| | | | | | | | | |No modification of Diversion due to P2| | | | | | | | | | | | | | | | |INV C | | | | | | | | | |------>| | | | | | | | | | | | | | | | | | | |<--180-| | | | Mohali Expires December 26, 2009 [Page 18] Internet-Draft Mapping Diversion and History-Info June 2009 | | | | | | | | | | | | | | | No response timer expire | | | | | | | |---INV D --->| | | | | | Diversion: | | | | | | userC; reason=no-answer; counter=1; privacy=full, | | | userB; reason=unconditional; counter=1; privacy=off, | | | History-Info: | | | | | | ; index=1, | | | | | | ; index=1.1 | | | | | | ; index=1.1.1 | | | | | | | | | | | | | | | | | | | |INV E | | | | | | | | | |------>| | | | | Diversion: | | | | | userD; reason=time-of-day; counter=1; privacy=off| | | | userC; reason=no-answer; counter=1; privacy=full,| | | | userB; reason=unconditional; counter=1; privacy=off, | | | History-Info: | | | | | ; index=1, | | | | | ; index=1.1 | | | | | ; index=1.1.1 | | | | | | | | | | | | | | | | | | | | | INV E | | | | | | | | | |------->| | | | History-Info: | | | | ; index=1, | | | | ; index=1.1, | | | | ; index=1.1.1, | | | | ; index=1.1.1.1, | | | | ; index=1.1.1.1.1, | | | ; index=1.1.1.1.1.1 | | | | | | | | | | | | | | | | | | | | | * Note: The IWF is an interworking function which could be a stand-alone equipment not defined in this draft (it could be a proxy). 7.4. Additional interworking Cases Even if for particular cases in which both headers could coexist it should be the network local policy responsibility to make it work together, here are described some situations and some recommendations on the behavior to follow. In the case where there is one network which includes different nodes, some of which support Diversion header and some which support History-info header, the problem is when any node handling a message does not know which node will next handle the message. This case can Mohali Expires December 26, 2009 [Page 19] Internet-Draft Mapping Diversion and History-Info June 2009 occur when the network has new and old nodes, the older ones using Diversion header and the more recent History-Info header. While a network replacement may be occurring there will be a time when both nodes exist in the network. If the different nodes are being used to support different subscriber types due to different node capabilities then the problem is more important. In this case there is a need to pass both History-Info header and Diversion header within the network core. These headers need to be equivalent to ensure that whatever node receives the message the correct diversion information is received. This requires that whichever header is received there is a requirement to be able to compare the headers and to convert the headers. Depending upon node capability then it may be possible to make assumptions as to how this is handled. If it is known that the older Diversion header supporting nodes do not pass on any received History-Info header then the interworking becomes easier. If a message is received with only Diversion headers then it has originated from an 'old' node. The equivalent History- Info entries can be created and these can then be passed as well as the Diversion header. If the node creates a new History-Info header for a call diversion, then an additional Diversion header must be created. If the next node is an 'old' node then the Diversion header will be used by that node and the History-Info entries will be removed from the message when it is passed on. If the next node is a new node then the presence of both Diversion header and History-Info header means that interworking has already occurred and the Diversion and History-Info entries must be considered equivalent. If both nodes pass on both History-Info header and Diversion header but only actively use one, then both types of node need to perform the interworking and must maintain equivalence between the headers. This will eventually result in the use of Diversion header being deprecated when all nodes in the network support History-Info header. 8. IANA Considerations This document makes no request of IANA. 9. Security Considerations The use of Diversion header or History-Info header require to apply the requested privacy and integrity asked by each diverting user or entity. Without integrity, the requested privacy functions could be downgraded or eliminated, potentially exposing identity information. Without confidentiality, eavesdroppers on the network (or any Mohali Expires December 26, 2009 [Page 20] Internet-Draft Mapping Diversion and History-Info June 2009 intermediaries between the user and the privacy service) could see the very personal information that the user has asked the privacy service to obscure. Unauthorised insertion, deletion of modification of those headers can provide misleading information to users and applications. A SIP entity that can provide a redirection reason in a History-Info header or Diversion header SHOULD be able to suppress this in accordance with privacy requirements of the user concerned. 10. Acknowlegements The editor would like to acknowledge the constructive feedback and support provided by Steve Norreys, Jan Van Geel, Martin Dolly, Francisco Silva, Guiseppe. Sciortino, Cinza Amenta, Christer Holmberg, Ian Elz, Jean-Francois Mule, Lionel Morand, Xavier Marjou, Philippe Fouquart, Mary Barnes, Francois Audet, Erick Sasaki, Shida Schubert and Joel M. Halpern. 11. References 11.1. Normative References [RFC2119] "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997. [RFC3261] "SIP: Session Initiation Protocol", RFC 3261, June 2002. [RFC3323] "A Privacy Mechanism for the Session Initiation Protocol (SIP)", RFC 3323, November 2002. [RFC3326] "The Reason Header Field for the Session Initiation Protocol (SIP)", RFC 3326, December 2002. [RFC3969] "The Internet Assigned Number Authority (IANA) Uniform Resource Identifier (URI) Parameter Registry for the Session Initiation Protocol (SIP), BCP 99", RFC 3969, December 2004. [RFC4234] "Augmented BNF for Syntax Specifications: ABNF", RFC 4234, October 2005. [RFC4244] "An Extension to the Session Initiation Protocol (SIP) for Request History Information", RFC 4244, November 2005. Mohali Expires December 26, 2009 [Page 21] Internet-Draft Mapping Diversion and History-Info June 2009 11.2. Informative References [RFC4458] "Session Initiation Protocol (SIP) URIs for Applications such as Voicemail and Interactive Voice Response (IVR)", RFC 4458, April 2006. [TS_24.604] 3rd Generation Partnership Project, "Technical Specification Group Core Network and Terminals ; Communication Diversion (CDIV) using IP Multimedia (IM)Core Network (CN) subsystem ; Protocol specification (Release 8), 3GPP TS 24.604", December 2008. [TS_29.163] 3rd Generation Partnership Project, "Technical Specification Group Core Network and Terminals ; Interworking between the IP Multimedia (IM) Core Network (CN) Subsystem and Circuit Switched (CS) networks (Release 8)", December 2008. [draft-levy-sip-diversion-09] "Diversion Indication in SIP, draft-levy-sip-diversion-09", May 2009. Appendix A. Interworking between Diversion header and Voicemail URI Voicemail URI is a mechanism described in RFC4458 to provide a simple way to transport only one redirecting user address and the reason why the diversion occurred in the R-URI of the INVITE request. This mechanism is mainly used for call diversion to a voicemail. Diversion header to Voicemail URI: Received: Diversion: userA-address;reason=user-busy;counter=1;privacy=full Sent (Voicemail URI created in the R-URI line of the INVITE): sip: voicemail@example.com;target=userA-address;cause=486 SIP/2.0 Mapping of the Redirection Reason is the same as for History-Info header with a default value set to 404. If the Diversion header contains more than one Diversion entry, the choice of the redirecting user information inserted in the URI is in charge of the network local policy. For example, the choice criterion of the redirecting information inserted in the URI could be the destination of forwarded INVITE request (if the voicemail serves Mohali Expires December 26, 2009 [Page 22] Internet-Draft Mapping Diversion and History-Info June 2009 this user or not). Note: This interworking could be done in addition to the interworking of the Diversion header into the History-Info header. Voicemail URI to Diversion header: In case of real Voicemail, this way of interworking should not happen. However, if for any reason it occurs, it is recommended to do it as following: Received: INVITE sip: voicemail@example.com;\ target=sip:+33145454500%40example.com;user=phone;\ cause=302 SIP/2.0 Sent in the forwarded INVITE: Diversion: sip:+ 33145454500%40example.com;user=phone;reason=unconditional;counter=1 Author's Address Marianne Mohali France Telecom 38-40 rue du General Leclerc Issy-Les-Moulineaux Cedex 9 92794 France Phone: +33 1 45 29 45 14 Email: marianne.mohali@orange-ftgroup.com Mohali Expires December 26, 2009 [Page 23]