Network Working Group M. Mohali Internet-Draft Orange Obsoletes: 6044 (if approved) March 04, 2015 Intended status: Informational Expires: September 5, 2015 Mapping and interworking of Diversion information Between Diversion and History-Info Headers in the Session Initiation Protocol (SIP) draft-mohali-rfc6044bis-02 Abstract Although the SIP History-Info header field is the solution adopted in IETF, the non-standard Diversion header field is nevertheless already implemented and used for conveying call diversion related information in the Session Initiation Protocol (SIP) signaling. On one hand, the non-standard Diversion header field is described, as Historic, in [RFC5806]. On the other hand, the History-Info header field is described in [RFC7044] that obsoletes the original[RFC4244] describing the History-Info header field. [RFC7044] defines the SIP header field, History-Info, for capturing the history information in requests and new SIP header field parameters for the History-Info and Contact header fields to tag the method by which the target of a request is determined. [RFC7044] also defines a value for the Privacy header field that directs the anonymization of values in the History-Info header field. Since the Diversion header field is used in existing network implementations for the transport of call diversion information, its interworking with the SIP History-Info standardized solution is needed. This document describes a recommended interworking guideline between the Diversion header field and the History-Info header field to handle call diversion information. In addition, an interworking policy is proposed to manage the headers' coexistence. This work is intended to enable the migration from non-standard implementations and deployments toward IETF specification-based implementations and deployments. This document obsoletes [RFC6044]that describes the interworking between the Diversion header field [RFC5806] and the obsoleted History-Info header field as defined on [RFC4244]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Mohali Expires September 5, 2015 [Page 1] Internet-Draft Mapping of Diversion and History-Info March 2015 Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on September 5, 2015. Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Background . . . . . . . . . . . . . . . . . . . . . . . 3 1.3. From RFC4244 to RFC7044 . . . . . . . . . . . . . . . . . 4 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 5 3. Interworking recommendations . . . . . . . . . . . . . . . . 7 3.1. General recommendations . . . . . . . . . . . . . . . . . 7 3.2. Privacy considerations . . . . . . . . . . . . . . . . . 7 3.3. Headers in SIP Method . . . . . . . . . . . . . . . . . . 9 3.4. SIP network/terminal using Diversion to SIP network/terminal using History-Info header . . . . . . . 9 3.5. SIP network/terminal using History-Info header to SIP network/terminal using Diversion header . . . . . . . . . 11 4. Header fields syntaxes reminder . . . . . . . . . . . . . . . 12 4.1. History-Info header field syntax . . . . . . . . . . . . 12 4.2. Diversion header field syntax . . . . . . . . . . . . . . 15 5. Diversion header to History-Info header . . . . . . . . . . . 15 6. History-Info header to Diversion header . . . . . . . . . . . 19 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.1. Example with Diversion header changed into History-Info header . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.2. Example with History-Info header changed into Diversion Mohali Expires September 5, 2015 [Page 2] Internet-Draft Mapping of Diversion and History-Info March 2015 header . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.3. Example with two SIP networks using History-Info header interworking with a SIP network using Diversion header . 21 7.4. Additional interworking Cases . . . . . . . . . . . . . . 23 8. Backward Compatibility . . . . . . . . . . . . . . . . . . . 25 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 10. Security Considerations . . . . . . . . . . . . . . . . . . . 25 11. Acknowlegements . . . . . . . . . . . . . . . . . . . . . . . 25 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 12.1. Normative References . . . . . . . . . . . . . . . . . . 26 12.2. Informative References . . . . . . . . . . . . . . . . . 26 Appendix A. Interworking between Diversion header and Voicemail URI . . . . . . . . . . . . . . . . . . . . . . . . 27 A.1. Diversion header field to Voicemail URI . . . . . . . . . 27 A.2. Voicemail URI to Diversion header field . . . . . . . . . 27 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 28 1. Introduction 1.1. Overview For some VoIP-based services (eg. Voicemail, Interactive Voice Recognition (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 applications, it needs to pass through the network. This is possible with two different SIP header fields: History-Info header field defined in [RFC7044] and the historic Diversion header field defined in [RFC5806] which are both able to transport diversion information in the SIP signaling. Although the Diversion header field is not standardized, it has been widely implemented. Therefore, it is useful to have guidelines to make this header field interwork with the standard History-Info header field. Note that the new implementation and deployment of the Diversion header field is strongly discouraged. This document provides a mechanism for header fields content translation between the Diversion header field and the History-Info header field. 1.2. Background The obsoleted History-Info header field [RFC4244] and its extension for forming SIP service URIs (including Voicemail URI) [RFC4458] used to be recommended by IETF to convey redirection information. They also used to be recommended in the "Communication Diversion (CDIV) service" 3GPP specification [TS_24.604]. Mohali Expires September 5, 2015 [Page 3] Internet-Draft Mapping of Diversion and History-Info March 2015 Concerning, the Diversion header field, it was originally described in an Internet Draft that was submitted to the SIP Working Group and was finally published as [RFC5806] for the historical record and to provide a reference for this RFC. This header field contains a list of diverting URIs and associated information providing specific information as the reason for the call diversion. Most of the first SIP-based implementations have implemented the Diversion header field when no standard solution was ready to deploy. The IETF has standardized the History-Info header field partly because it can transport general history information. This allows the receiving part to determine how and why the session is received. As the History-Info header field may contain further information than call diversion information, it is critical to avoid losing information and be able to extract the relevant data using the retargeting cause URI parameter described in [RFC4458] for the transport of the call forwarding reason. The Diversion header field and the History-Info header field have different syntaxes reminded in this document. Note that the main difference is that the History-Info header field is a chronological writing header whereas the Diversion header field applies a reverse chronology (i.e. the first diversion entry read corresponds to the last diverting user). The Appendix A provides an interworking guideline between the Diversion header field and the Voicemail URI which is another way to convey diversion information without using the History-Info header field. The Voicemail URI is defined in [RFC4458]. 1.3. From RFC4244 to RFC7044 The detail of why and how [RFC4244] has been updated and replaced by [RFC7044] is provided in section 16 of [RFC7044]. Here are the main changes for the History-Info header field implementation: 1. Added header field parameters "mp", "rc" and "np" to capture the specific method by which a target is determined. 2. Added a way to indicate a gap in History-Info by adding a "0" in the index. 3. To apply privacy, entries are anonymized rather than removed. 4. Many SHOULD are changed into MUST to have a more reliable header. Mohali Expires September 5, 2015 [Page 4] Internet-Draft Mapping of Diversion and History-Info March 2015 Backward compatibility aspects are discussed in section 8 of this document. 2. Problem Statement This section provides the baseline terminology used in the rest of the document and defines the scope of interworking between the Diversion header field and the History-Info header field. 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 a simple proxy to route the session or for an application server to provide a supplementary service. The Diversion header field and the History-Info header field differ in the approach and scope of addressing this problem. For clarity, the following vocabulary is used in this document: o Retarget/redirect: these terms refer to the process of a Proxy Server/User Agent Client (UAC) changing a Request-URI (Section 7.1 of [RFC3261]) in a request and thus changing the target of the request. This includes changing the Request-URI due to a location service lookup and redirect processing. This also includes internal (to a proxy/SIP intermediary) changes of the URI prior to the forwarding of the request. The retarget term is defined in [RFC7044]. o 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 during or prior to the session establishment. This document does not intend to describe when or how History-Info or Diversion header fields should be used. Hereafter is provided clarification on the context in which the interworking is required. The Diversion header field has exactly the same scope as the call diversion service and each header field entry reflects a call diversion invocation. The Diversion header field is used for recording call forwarding information which could be useful to Mohali Expires September 5, 2015 [Page 5] Internet-Draft Mapping of Diversion and History-Info March 2015 network entities downstream. Today, this SIP header field is implemented by several manufacturers and deployed in networks. The History-Info header field is used to store all retargeting information including call diversion information. As such, the History-Info header field [RFC7044] is used to convey call diversion related information by using a cause URI parameter [RFC4458] in the relevant entry. Note, however, that the use of cause URI parameter [RFC4458] in a History-Info entry for a call diversion is specific to the 3GPP specification [TS_24.604]. [RFC4458] focuses on retargeting toward voicemail server and does not specify whether the cause URI parameter should be added 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 to avoid the loss of non-mapped information at the boundary between a network region using History-Info header field and one using the Diversion header field. The [RFC7044] defines three header field parameters, "rc", "mp", and "np". The header field parameters "rc" and "mp" indicate the mechanism by which a new target for a request is determined. The header field "np" reflects that the target has not changed. All parameters contain an index whose value refers to the hi-index of the hi-entry with an hi-targeted-to-uri that represents the Request-URI that was retargeted. Since both header fields address call forwarding needs, diverting information could be mixed-up or be inconsistent if both are present in an uncoordinated fashion in the INVITE request. So, Diversion and History-Info header fields must not independently coexist in the same session signaling. This document addresses how to convert information between the Diversion header field and the History-Info header field, and when and how to preserve both header fields to cover additional cases. For the transportation of consistent diversion information downstream, it is necessary to make the two header fields interwork. Interworking between the Diversion header field and the History-Info header field is introduced in sections 5 and 6. Since coexistence scenario may vary from one use case to another one, guidelines regarding header fields interaction are proposed in section 3. Mohali Expires September 5, 2015 [Page 6] Internet-Draft Mapping of Diversion and History-Info March 2015 3. Interworking recommendations 3.1. General 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 is aware, by configuration, that it is at the border between two regions, one using History-Info header field and one using Diversion header field. As History-Info header field is a standard solution, a network using the Diversion header field must be able to provide information to a network using the History-Info header field. In this case, to avoid header fields coexistence it is required to replace, as often as possible, the Diversion header field with the History-Info header field in the INVITE request during the interworking. Since, the History-Info header field has a wider scope than the Diversion header field, it may be used for other needs and services than call diversion. In addition to trace call diversion information, History-Info header field also acts as a session history and can store all successive Request-URI values. Consequently, even if it should be better to remove the History-Info header field after the creation of the Diversion header field avoiding confusion, the History-Info header field must remain unmodified in the SIP signaling if it contains supplementary (non-diversion) information. It is possible to have History-Info header fields that do not have values that can be mapped into the Diversion header field. In this case, no interworking with Diversion header field should be performed and it must be defined per implementation what to do in this case. This point is left out of the scope of this document. 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. The following sections describe the basic common use case. Additional interworking cases are described in section 7.5. 3.2. Privacy considerations When a SIP message is forwarded to a domain for which the SIP intermediary is not responsible, a Privacy Service at the boundary of the domain applies the appropriate privacy based on the value of the Mohali Expires September 5, 2015 [Page 7] Internet-Draft Mapping of Diversion and History-Info March 2015 Privacy header field in the message header or in the privacy parameter within concerned header. 1. For the History-Info header field, it is the "headers" component of the hi-targeted-to-uri in the individual hi-entries with the possible priv-value "history". 2. For the Diversion header field, it is the diversion-privacy parameter "privacy" in each Diversion header field. o For the History-Info header field, as recommended in [RFC7044]: - If there is a Privacy header field in the message header of a request with a priv-value of "header" or "history", then all the hi-targeted-to-uris (in the hi-entries associated with the domain for which the SIP intermediary is responsible) are anonymized by the Privacy Service. The Privacy Service must change any hi-targeted-to-uri in these hi-entries that have not been anonymized to the anonymous SIP URI "anonymous@anonymous.invalid" as recommended in sections 4.1.1.3 and 4.1.1.2 of [RFC3323]. - If there is a Privacy header field in the "headers" component of a hi-targeted-to-uri with a priv-value of "history", then all the concerned hi-entries must be anonymized as described above prior to forwarding. The Privacy Service must remove the Privacy header field from the "headers" component of the hi-targeted-to-uris of the concerned hi-entries and the priv-value of "history" from the Privacy header field in the message header of the request prior to forwarding. If there are no remaining priv-values in the Privacy header field, the Privacy Service must remove the Privacy header field from the request. o For the Diversion header field: - If there is a Privacy header field in the message header of a request with a priv-value of "header", then all the addresses in the Diversion header fields (associated with the domain for which the SIP intermediary is responsible) are anonymized by the Privacy Service by changing the address to the anonymous SIP URI "anonymous@anonymous.invalid" as recommended in sections 4.1.1.3 and 4.1.1.2 of [RFC3323] prior to forwarding. - For the each Diversion header field or each entry in the Diversion header field, if there is a diversion-privacy Mohali Expires September 5, 2015 [Page 8] Internet-Draft Mapping of Diversion and History-Info March 2015 parameter with a value set to "full", "uri" or "name", then the concerned Diversion header field address must be anonymized as described above prior to forwarding. In the concerned Diversion header field entries, the diversion- privacy parameter must be removed from the header. The privacy information interworking as described in sections 5 and 6 must only be considered within a trusted domain that ensure to correctly apply the privacy requirements. 3.3. Headers in SIP Method The recommended interworking presented in this document should apply only for INVITE requests. In 3xx responses: Both History-Info and Diversion header fields could be present in 3xx responses. When a proxy wants to interwork with a network supporting the other header field, it should apply the interworking between Diversion header field and History-Info header field 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 field or History-Info header field (according to its capabilities) in the forwarded INVITE. Local policies could apply to send the received header field in the next INVITE or not. In SIP responses other than 100: All SIP responses where History-Info could be present are not used for the Call Forwarding service and should not be changed into Diversion header field. The destination network must be transparent to the received History-Info header field. Note: The following mapping is inspired from the ISUP to SIP interworking described in [TS_29.163]. 3.4. SIP network/terminal using Diversion to SIP network/terminal using History-Info header When the Diversion header field is used to create a History-Info header field, the Diversion header field must be removed in the outgoing INVITE. It is considered that all the information present in the Diversion header field is transferred in the History-Info header field. Mohali Expires September 5, 2015 [Page 9] Internet-Draft Mapping of Diversion and History-Info March 2015 If a History-Info header field is also present in the incoming INVITE (in addition to Diversion header field), the Diversion header field and History-Info header field present must be mixed and only the diversion information not yet present in the History-Info header field must be inserted as a last entry (more recent) in the existing History-Info header field, following the creation process recommended in [RFC7044]. As an example, this could be the case of an INVITE coming from network_2 using Diversion header field but previously passed through network_1 using History-Info header field (or the network_2 uses History-Info header field to transport successive URI information) and going to network_3 using History-Info header field. 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;rc=1 | | | | | | | | | | | | | | | | | |INVITE | | | | | | | | | |------>| | | | | | | | | |History-Info: | | | | | | | | |; index=1,| | | | | | | |; index=1.1;rc=1, | | | | | | |; index=1.1.1;mp=1.1 | | In this case, the incoming INVITE contains a Diversion header field and a History-Info header field. Therefore, as recommended in this document, it is necessary to create for network_3, a single History- Info header field gathering existing information from both the History-Info and the Diversion header fields received. Anyway, it is required from network_2 (ie.IWF) to remove the Diversion header field when the message is going to a network not using the Diversion header Mohali Expires September 5, 2015 [Page 10] Internet-Draft Mapping of Diversion and History-Info March 2015 field. Then network_3 could use call forwarding information that is present in a single header field and add its own diversion information if necessary. Notes: 1. If a network is not able either to use only one header field each time, or to maintain both header fields up to date, the chronological order can not be certified. 2. It is not possible to have only Diversion header field when the History-Info header field 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 field taking into account the Diversion internal chronology. 3.5. SIP network/terminal using History-Info header to SIP network/ terminal using Diversion header When the History-Info header field is interpreted to create a Diversion header field, some precautions must be taken. If the History-Info header field contains only call forwarding information, then it must be deleted after the interworking. If the History-Info header field contains other information, then only the information of concern to the diverting user must be used to create entries in the Diversion header field and the History-Info header field must be kept as received in the INVITE and forwarded downstream. Note: The History-Info header field could be used for other reasons than call diversion 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 field, it would be better not to lose history information due to passing though the network which only support Diversion header field. A recommended solution must not disrupt the standard behavior and networks which do not implement the History-Info header field must be transparent to a received History-Info header field. If a Diversion header field is present in the incoming INVITE (in addition to History-Info header field), only diversion information present in the History-Info header field but not in the Diversion header field must be inserted from the last entry (more recent) into the existing Diversion header field as recommended in the [RFC5806]. Mohali Expires September 5, 2015 [Page 11] Internet-Draft Mapping of Diversion and History-Info March 2015 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 field enables the recording of sequential forking for the same served-user. During an interworking, from the History-Info header field to Diversion header field, the History-Info entries containing a forking situation (with an incremented "index" parameter) could possibly be mapped if it contains a call forwarding "cause" parameter. The interworking entity could choose to create only a Diversion entry or 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 A). 4. Header fields syntaxes reminder 4.1. History-Info header field syntax The ABNF syntax [RFC5234] for the History-Info header field and header field parameters is as follows: History-Info = "History-Info" HCOLON hi-entry *(COMMA hi-entry) hi-entry = hi-targeted-to-uri *(SEMI hi-param) hi-targeted-to-uri = name-addr hi-param = hi-index/hi-target-param/hi-extension hi-index = "index" EQUAL index-val index-val = number *("." number) number = [ %x31-39 *DIGIT ] DIGIT hi-target-param = rc-param / mp-param / np-param rc-param = "rc" EQUAL index-val mp-param = "mp" EQUAL index-val np-param = "np" EQUAL index-val hi-extension = generic-param The ABNF definitions for "generic-param", "name-addr", "HCOLON", "COMMA", "SEMI", and "EQUAL" are from[RFC3261]. The History-Info header field is specified in [RFC7044]. The top- most History-Info entry (first in the list) corresponds to the oldest history information. Mohali Expires September 5, 2015 [Page 12] Internet-Draft Mapping of Diversion and History-Info March 2015 Cause URI parameter: A hi-entry may contain a cause URI parameter expressing the diversion reason. This cause URI parameter is defined in [RFC4458]. The ABNF grammar [RFC5234] for the cause-param parameter is reminded below as it has been subject to Errata [ID: 1409] in [RFC4458]. The Status-Code is defined in [RFC3261]. cause-param = "cause=" Status-Code This parameter is also named cause-param is a SIP/SIPS URI parameter 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 [RFC4458] . 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 precisely, each diverting user is located in the hi-entry before the one containing a cause-param with cause value as listed in [RFC4458]. Reason header field: Moreover, the Reason header field defined in [RFC3326] should be escaped in the hi-entry of the diverting user when the call diversion is due to a received SIP response. The Reason header field 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 field 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 field parameter is not taken into account in the mapping with a Diversion header field. Target URI parameter: The [RFC4458] also defines the 'target' URI parameter which could be inserted in a Request-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 already present in the hi-entries, the 'target' URI parameter is not taken into account regarding the interworking with the Diversion header field. From the Diversion header field, it could be possible to create the 'target' URI parameter in the hi-entries and/or in the Request-URI but this Mohali Expires September 5, 2015 [Page 13] Internet-Draft Mapping of Diversion and History-Info March 2015 possibility is based on local policies not described in this document. Privacy header field: A Privacy header field as defined in [RFC3323] could also be embeded in hi-entries with the 'history' value defined in [RFC7044]. Index header field parameter: The index parameter is a string of digits, separated by dots to indicate the number of forward hops and retargets. 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. Missing entry: If the request clearly has a gap in the hi-entry (i.e., the last hi-entry and Request-URI differ), the entity adding an hi-entry must add a single index with a value of "0" (i.e., the nonnegative integer zero) prior to adding the appropriate index for the action to be taken (eg. Index=1.1.2.0.1). Prior to any application usage of the History-Info header field parameters, the SIP entity that processes the hi-entries must evaluate the hi-entries and determine if there are any gaps in the hi-entries. "histinfo" option tag: According to [RFC7044], a proxy that receives a Request with the "histinfo" option tag in the Supported header field 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. Example: History-Info: ; index=1, ;index=1.1;mp=1, ; index=1.1.1;mp=1.1 Mohali Expires September 5, 2015 [Page 14] Internet-Draft Mapping of Diversion and History-Info March 2015 4.2. Diversion header field syntax The following text is restating the exact syntax that the production rules in [RFC5806] define, but using [RFC5234] ABNF: 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) diversion-extension = token [EQUAL (token / quoted-string)] Note: The Diversion header field 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: ; reason=user-busy; counter=1; privacy=full, ; reason=unconditional; counter=1; privacy=off 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 field is Mohali Expires September 5, 2015 [Page 15] Internet-Draft Mapping of Diversion and History-Info March 2015 present, the interworking function must adapt its behavior to respect the chronological order. For more information, see section 3. Concerning the privacy information in the Diversion header field, the following mapping only applies within a trusted domain, otherwise see the privacy considerations in section 3.2. 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 History-Info entry (the last one) must be created with the diverted-to party address present in the Request-URI of the received INVITE. The mapping is described in the table hereafter. The first entry created in the History-Info header field contains: - a hi-target-to-uri with the name-addr parameter of the bottom- most Diversion header field, - if a privacy parameter is present in the bottom-most Diversion entry, then a Privacy header field must be escaped in the History- Info header field as described in the table hereafter, - a hi-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): Source Destination Diversion header component: History-Info header component: ======================================================================= Name-addr Hi-target-to-uri ======================================================================= Reason of the previous Cause URI parameter Diversion entry A cause-param "cause" is added in each hi-entry (except the first one) "unknown"----------------------------------404 (default 'cause' value) "unconditional"----------------------------302 "user-busy"--------------------------------486 "no-answer"--------------------------------408 "deflection "------------------------------480 or 487 "unavailable"------------------------------503 "time-of-day"------------------------------404 (default) Mohali Expires September 5, 2015 [Page 16] Internet-Draft Mapping of Diversion and History-Info March 2015 "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 extended with ".1" Then the History-Info header created with the Diversion entry with the previous index extended 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" ====================================================================== hi-target-param A mp-param "mp" is added in each created hi-entry (except the first one) The "mp" parameter is set to the index value of the preceding hi-entry. ======================================================================= 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, - an index set to the previous created index extended with a new level ".1" added at the end, - a hi-target-param set to "mp" equals to the index value of the previous preceding hi-entry. Notes: Mohali Expires September 5, 2015 [Page 17] Internet-Draft Mapping of Diversion and History-Info March 2015 1. For other optional Diversion parameters, there is no recommendation as History-Info header field does not provide equivalent parameters. 2. For values of the diversion-reason 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[TS_24.604] as it cover a large portion of cases. 3. The Diversion header field can contain a "tel" URI as defined in [RFC3966]in the name-addr parameter. The History-Info header field can also contain an address that is a "tel" URI but if this hi-entry has to be completed with either a SIP header field (eg. Reason or Privacy) or a SIP URI parameter (eg. 'cause' or 'target'); the "tel" URI must be converted into a SIP URI. [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 field, the History-Info header field should be created with a SIP URI with user=phone and a domain set to "unknow.invalid". 4. The Diversion header field allows the carrying of a counter that retains the information about the number of successive redirections. History-Info does not have an equivalent because to trace and count the number of diversion it is necessary to count cause parameter containing a value associated to a call diversion listed in[RFC4458]. Read the index value is not enough. With the use of the "placeholder" entry the History-info header field entries could reflect the real number of diversion occurred still thanks to the cause-param. Example of placeholder entry in the History-Info header field: ;index=1.1 ;index=1.1.1;mp=1.1 "cause=xxx" reflects the diverting reason of a previous diverting user. For a placeholder hi-entry the value "404" must be taken for the cause-param and so, located in the next hi-entry. Mohali Expires September 5, 2015 [Page 18] Internet-Draft Mapping of Diversion and History-Info March 2015 Concerning local policies recommendations about header fields coexistence in the INVITE request, see sections 3 and 7.5. 6. History-Info header to Diversion header Concerning the privacy information for the History-Info header field, the following mapping only applies within a trusted domain, otherwise see the privacy considerations in section 3.2. 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 field entry selected will be mapped into the last Diversion header field entry and so on. One Diversion header field entry must be created for each History-Info entry having cause-param with a value listed in [RFC4458]. Diversion information: The Target_entry and the Diverting_entry terms defined below are used to ease the mapping understanding of the History-Info header field. The diversion information can be identified by finding the following hi-entries: o Target_entry: hi-entries containing a cause-param URI parameter with a value listed in [RFC4458]will contain the diversion reason and the address of the target of the concerned call forwarding. Following the [RFC7044]these hi-entries may also contain a hi- target-param set to "mp". o Diverting_entry: For each previously identified hi-entry: - If there is a "mp" header field parameter, the hi-entry whose hi-index matches the value of the hi-target-param "mp" will contain the diverting party address, its possible privacy and/ or SIP reason when the retargeting has been caused by a received SIP response. - If there is no "mp" header field parameter, the information of the diverting party address, privacy and/or SIP reason will be found in the hi-entry that precede this identified hi-entry. Note: Following [RFC7044], all retargeting entries must point to a hi-entry that contain a "mp" parameter but for backward compatibility reasons, it may be absent from some of the received hi-entries. You Mohali Expires September 5, 2015 [Page 19] Internet-Draft Mapping of Diversion and History-Info March 2015 can find more information on the backward compatibility aspects in section 8. The History-Info header field must be mapped into the Diversion header field as following: Source Destination History-Info header component: Diversion header component: ===================================================================== Hi-target-to-uri Name-addr of the Diverting_entry. ===================================================================== Cause-param Reason of the Target_entry 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 field escaped Privacy in the hi-targeted-to-uri of the Diverting_entry "history"----------------------------------"full" Privacy header field ----------------------"Off" Absent or "none" ===================================================================== Note: For other optional History-Info parameters, there is no recommendation as Diversion header field does not provide equivalent parameters. Concerning local policies recommendations about header fields coexistence in the INVITE request, see section 3. Mohali Expires September 5, 2015 [Page 20] Internet-Draft Mapping of Diversion and History-Info March 2015 7. Examples 7.1. Example with Diversion header changed into History-Info header INVITE sip:last_diverting_target Diversion: ;reason=unconditional;counter=1; privacy=off, ;reason=user-busy;counter=1; privacy=full, ;reason=no-answer;counter=1; privacy=off Mapped into: History-Info: ; index=1, ;index=1.1;mp=1, ;index=1.1.1;mp=1.1, ;index=1.1.1.1;mp=1.1.1 7.2. Example with History-Info header changed into Diversion header INVITE sip:last_diverting_target; cause=486 History-Info: ; index=1, ;index=1.1;mp=1, ;index=1.1.1;mp=1.1 Mapped into: Diversion: ; reason=user-busy; counter=1; privacy=off, ; 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 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. Mohali Expires September 5, 2015 [Page 21] Internet-Draft Mapping of Diversion and History-Info March 2015 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; rc=1 | | | | | | | | | | | | | | | | | |INV C | | | | | | | | | |------>| | | | | | | | | |History-Info: | | | | | | | | ; index=1,| | | | | | | ; index=1.1; rc=1, | | | | | | ; index=1.1.1; mp=1.1 | | | | | | | | | | | | | | |INV C | | | | | | | | | |----->| | | | | | | | | Diversion: | | | | | | | | | userB; reason=unconditional; counter=1; privacy=off | | | |History-Info: | | | | | | | | ; index=1,| | | | | | | ; index=1.1; rc=1,| | | | | | ; index=1.1.1; mp=1.1 | | | | | | | | | | | | | | |INV C | | | | | | | | | |------>| | | | | | | | | No modification of Diversion header | | | | | | | | | | | | | | | | |INV C | | | | | | | | | |------>| | | | | | | | | | | | | | | | | | | |<--180-| | | | | | | | | | | | | | | | | | | No response timer expires | | | | | | | |---INV D --->| | | | | |Diversion: | | | | | |userC; reason=no-answer; counter=1; privacy=full, | | | |userB; reason=unconditional; counter=1; privacy=off, | | | History-Info: | | | Mohali Expires September 5, 2015 [Page 22] Internet-Draft Mapping of Diversion and History-Info March 2015 | | | ; index=1, | | | | | | ; index=1.1; rc=1, | | | | | | ; index=1.1.1; mp=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; rc=1, | | | | | ; index=1.1.1; mp=1.1 | | | | | | | | | | | | | | | | | | | | INV E | | | | | | | | | |------>| | | History-Info: | | | | | | | | ; index=1, | | | | | | | ; index=1.1; rc=1, | | | | | | ; index=1.1.1; mp=1.1, | | | | ; index=1.1.1.0.1, | | |;index=1.1.1.0.1.1; mp=1.1.1.0.1,| | |; index=1.1.1.0.1.1.1; mp=1.1.1.0.1.1| | | | | | | | | | | | | | | | | | | | | * Note: The IWF is an interworking function which could be a stand- alone equipment not defined in this document (it could be a proxy). 7.4. Additional interworking Cases Even if for particular cases in which both header fields 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 them supporting Diversion header field and other ones supporting History-info header field, there is a problem when any node handling a message does not know the next node that will handle the message. This case can occur when the network has new and old nodes, the older ones using Diversion header field and the more recent History-Info header field. While a network replacement may be occurring there will be a time when both nodes coexist in the network. If the different nodes are being used to support different subscriber types due to different Mohali Expires September 5, 2015 [Page 23] Internet-Draft Mapping of Diversion and History-Info March 2015 node capabilities then the problem is more important. In this case there is a need to pass both History-Info header field and Diversion header field within the core network. These header fields need to be equivalent to ensure that, whatever the node receiving the message, the correct diversion information is received. This requires that whatever the received header field, there is a requirement to be able to compare the header fields and to convert the header fields. Depending upon the node capability, it may be possible to make assumptions as to how this is handled. o If it is known that the older Diversion header field supporting nodes do not pass on any received History-Info header field then the interworking becomes easier. If a message is received with only Diversion header fields 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 field. o If the node creates a new History-Info header field for a call diversion, then an additional Diversion header field must be created. o If the next node is an 'old' node then the Diversion header field will be used by that node and the History-Info entries will be removed from the message when it is passed on. o If the next node is a new node then the presence of both Diversion header field and History-Info header field means that interworking has already occurred and the Diversion and History-Info entries must be considered equivalent. o If both nodes pass on both History-Info header field and Diversion header field but only actively use one, then both types of node need to perform the interworking and must maintain equivalence between the header fields. This will eventually result in the use of Diversion header field being deprecated when all nodes in the network support History-Info header field. o If a gap is identified in the History-Info header field by a node that would create a new entry, it shall add a single index with a value of "0" prior to adding the appropriate index for the action to be taken. Mohali Expires September 5, 2015 [Page 24] Internet-Draft Mapping of Diversion and History-Info March 2015 8. Backward Compatibility The backward compatibility aspects are due to the changes on the History-Info header field evolution from [RFC4244] to [RFC7044]that are described in section 1.3 of this document. The backawrd compatibility is taken into account throughout this document for the interworking with the Diversion header field. More details are provided in the backward compatibility section of [RFC7044]. 9. IANA Considerations This document makes no request of IANA. 10. Security Considerations The security considerations in [RFC7044] and [RFC5806] apply. The privacy considerations described in section 3.2 apply. The use of Diversion header field or History-Info header field 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 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 header fields can provide misleading information to users and applications. A SIP entity that can provide a redirection reason in a History-Info header field or Diversion header field should be able to suppress this in accordance with privacy requirements of the user concerned. 11. 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, Mary Barnes, Francois Audet, Erick Sasaki, Shida Schubert, Joel M. Halpern, Bob Braden and Robert Sparks. Merci a Lionel Morand, Xavier Marjou et Philippe Fouquart. 12. References Mohali Expires September 5, 2015 [Page 25] Internet-Draft Mapping of Diversion and History-Info March 2015 12.1. Normative References [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. [RFC3966] "The tel URI for Telephone Numbers", RFC 3966, December 2004. [RFC4244] "An Extension to the Session Initiation Protocol (SIP) for Request History Information", RFC 4244, November 2005. [RFC5806] "Diversion Indication in SIP", March 2010. [RFC7044] "An Extension to the Session Initiation Protocol (SIP) for Request History Information", RFC 7044, February 2014. 12.2. Informative References [RFC4458] "Session Initiation Protocol (SIP) URIs for Applications such as Voicemail and Interactive Voice Response (IVR)", RFC 4458, April 2006. [RFC5234] "Augmented BNF for Syntax Specifications: ABNF", RFC 5234, January 2008. [RFC6044] "Mapping and Interworking of Diversion Information between Diversion and History-Info Headers in the Session Initiation Protocol (SIP)", RFC 6044, October 2010. [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. Mohali Expires September 5, 2015 [Page 26] Internet-Draft Mapping of Diversion and History-Info March 2015 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 Request-URI of the INVITE request. This mechanism is mainly used for call diversion to a voicemail. A.1. Diversion header field 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 field with a default value set to 404. If the Diversion header field 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 this user or not). Note: This interworking could be done in addition to the interworking of the Diversion header field into the History-Info header field. A.2. Voicemail URI to Diversion header field 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 Mohali Expires September 5, 2015 [Page 27] Internet-Draft Mapping of Diversion and History-Info March 2015 Author's Address Marianne Mohali Orange 38-40 rue du General Leclerc Issy-Les-Moulineaux Cedex 9 92794 France Phone: +33 1 45 29 45 14 Email: marianne.mohali@orange.com Mohali Expires September 5, 2015 [Page 28]