MARTINI WG H. Kaplan Internet Draft Acme Packet Intended status: Standards-Track Expires: April 25, 2011 October 25, 2010 SIP GIN MARTINI with Open-plan Local-number Identifier Values for Enterprises (OLIVE) draft-kaplan-martini-with-olive-02 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. 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Kaplan Expires April 18, 2010 [Page 1] Internet-Draft SIP MARTINI with OLIVE October 2010 Abstract The Martini Working Group has defined a mechanism for SIP IP-PBX type devices to REGISTER and obtain SIP service for E.164-based Address of Records, using the GIN mechanism [draft-gin]. This document defines a means for open-plan Local-Numbers to be used with Martini-based IP-PBXs. Table of Contents 1. Introduction..................................................2 2. Definitions...................................................3 3. Background....................................................3 3.1. The GIN Mechanism........................................3 3.2. Local-Numbers............................................4 4. The Solution - an Overview....................................4 5. Registering for Local-Number AoRs.............................5 6. SSP Processing of Inbound Non-E.164 Requests..................7 7. Interaction with Other Mechanisms.............................7 7.1. Globally Routable User-Agent URIs (GRUU).................7 7.2. Registration Event Package...............................7 7.3. Non-Adjacent Contact Registration (Path) and Service Route Discovery......................................................8 8. Open Issues...................................................8 9. Examples......................................................8 9.1. Usage Scenario: Basic Registration case..................9 10. IANA Considerations.........................................10 11. Security Considerations.....................................10 12. Acknowledgements............................................10 13. Informative References......................................11 Author's Address.................................................12 Appendix A - Why Local-Numbers may need processing by SSPs.......12 1. Introduction In many deployed SIP Service Provider (SSP) architectures, it is common to use REGISTER requests to provide the reachability information for IP-PBXs, instead of DNS-based resolution and routing. An IETF-defined mechanism for doing so is being worked on in the Martini Working Group, with the GIN mechanism [draft-gin]. The current GIN mechanism only supports E.164-based AoRs, however in actual deployments private-extension or "local" numbers are used for hosted and carrier-provided intra-Enterprise calling services. These forms of AoRs are not supported by the current GIN mechanism. This document defines a means by which they can be supported, in a manner consistent with [RFC3261] and [draft-gin]. Kaplan Expires - April 2011 [Page 2] Internet-Draft SIP MARTINI with OLIVE October 2010 2. Definitions For brevity's sake, this document uses the word "request" instead of "out-of-dialog request", but in all case means out-of-dialog request. AoR: address-of-record, as defined by RFC 3261: a URI by which the user is canonically known (e.g., on their business cards, in the From header field of their requests, in the To header field of REGISTER requests, etc.). Open-plan: an open-plan is a dialing-plan which is not constrained to be a specific set of numbers all known to the SSP; some specific numbers may be known by the SSP, and/or a beginning set of digits are known to the SSP and used to route calls to different branches Local-Number: an AoR which follows the form of local-number in [RFC3966], but may be encoded in a SIP or TEL URI. The local-number contains a 'phone-context' parameter identifying the scope of its number. Implicit Registration: implicitly providing the reachability information for something other than the AoR explicitly indicated in the Register transaction. Reachability Information: a set of URI's identifying the host and path of Proxies to reach that host; like any URI, these URI's may identify the specific connection transport, IP Address, and port information, or they may only identify FQDN's. SSP: SIP Service Provider, as defined by [RFC5486]. 3. Background 3.1. The GIN Mechanism The GIN mechanism, defined in [draft-gin], allows a SIP UA such as an IP-PBX to Register a set of E.164 AoRs in "bulk". Instead of creating a separate REGISTER transaction for every E.164 AoR, the IP-PBX sends one REGISTER request with a 'bnc' Contact URI parameter which indicates the Contact URI needs to be expanded in the Registrar's location service database. The expansion is such that each E.164 user number becomes the user portion of the registered Contact URI, one for each implicitly registered E.164 number-based AoR. SIP Request routing to the Registered E.164 AoR then follows normal [RFC3261] procedures, replacing the Request URI with the expanded Kaplan Expires - April 2011 [Page 3] Internet-Draft SIP MARTINI with OLIVE October 2010 registered Contact URI, and adding any Path information as a Route set, etc. 3.2. Local-Numbers The Local-Number syntax for TEL URIs is defined in [RFC3966], such that a local-number is a set of digits, possibly with an extension or isdn-subaddress parameter, and scoped to the domain name or global-number-digits in its phone-context. In theory, a SIP UA can target its request to a Local-Number using the [RFC3966] syntax in a TEL URI or SIP URI, and have the request delivered to the UA or IP- PBX identified by the user digits for the given phone-context, which may subsequently route the request to the specific extension or isdn-subaddress. In practice it's not that simple. Most branch-office IP-PBXs do not use the Local-Number syntax for their targets, and do not recognize such syntax if they receive it in the Request URI. Often the SSP adds the phone-context to received requests from the IP-PBX, and removes it when sending to the IP-PBX. The reasons for this include: (a) the IP-PBX is wholly within the context and thus has no knowledge of, nor concern that there cold be, other contexts; (b) the IP-PBX may not actually know all the numbers in the private number plan, only its local ones; and (c) historically it has not been necessary for them to add such explicit indicators for things to work, and thus the status-quo is difficult to change. Furthermore, Local-Numbers are difficult because they are doubly- scoped: once at the URI level by the domain name, and internally by the phone-context URI user parameter. The authoritative system for the Local-Number user portion (the system(s) which knows what they are and how to process them) is not necessarily identified by the URI's domain name, but rather may be identified by the phone- context's value. In other words, the SSP may not know about all possible Local-Number numbers, and even a given IP-PBX may not know them all for its Enterprise; the knowledge may be distributed. This presents difficulties for certain GIN functions such as reg-event, and is why this document refers to GIN support for Local-Numbers as being for "open-plan" scenarios. 4. The Solution - an Overview The general concept proposed in this document is to logically apply GIN for the complete set of Local-Number "AoRs" of the Registered-to domain, as if they were individually Registered. The GIN-based REGISTER request would cause the Registrar to logically populate the set of AoR-to-Contact bindings, as it did before. Kaplan Expires - April 2011 [Page 4] Internet-Draft SIP MARTINI with OLIVE October 2010 The Contact URI user portion would also be "expanded", using the same user portion as that of the implicitly registered AoRs: namely a Local-Number format. The Local-Number username is "normalized" in the same manner as [draft-gin]. Note that the list of Local-Number AoRs associated with a PBX is a matter of local provisioning at the SSP and at the PBX, as it was in [draft-gin]. The mechanism defined in this document does not provide any means to detect or recover from provisioning mismatches (although the registration event package can be used as a standardized means for auditing such AoRs). No new option-tag is required, because this document's mechanism does not require any changes in GIN [draft-gin] registration nor in subsequent [RFC3261] routing behavior in the IP-PBX, nor in any proxies along the path. The routing follows the [RFC3261] Registered AoR-contact resolution model, which is a basic function of SIP. The only SIP devices affected by this document's mechanism is the SSP's Registrar, which needs to update the appropriate AoR entries, and any proxy/ies of the SSP which perform route resolution by looking up the contents of the (logical) location-service database. Since such proxies may not even be in the path of the REGISTER request, an option-tag will not help. And since the Registrar and Proxies in question are all under control of the same administrative entity (the SSP), it is reasonable to expect them all to support this document's mechanism, if any do. 5. Registering for Local-Number AoRs This document's mechanism relies on the GIN [draft-gin] Registration mechanism. The IP-PBX Registers into the SSP, using a REGISTER request with the "gin" option-tag in the Require and Proxy-Require header fields, and a Contact URI containing the "bnc" URI parameter and no user portion. After the PBX is authenticated, the registrar updates its location service so that each of the Local-Number AoRs associated with the PBX creates a unique AOR to Contact mapping. In practice, however, the SSP domain may not have specific knowledge of any or all user names within a given phone-context's scope. In fact, the Local-Number TEL URI parameters (which are URI user parameters in SIP URIs) may only have meaning to the ultimate target of the request, or some entity which is authoritative for the phone- context's user names. Those parameters cannot be removed by the SSP if it does not actually process the user portions of the Local- Number. (i.e., if it does not have the dial-plan, etc.) Kaplan Expires - April 2011 [Page 5] Internet-Draft SIP MARTINI with OLIVE October 2010 With regard to this document's mechanism, what this means is that such an SSP cannot physically instantiate an AoR in a database for every possible Local-Number and cannot physically instantiate an expanded Contact URI for every possible Local-Number user name with every possible user parameter. That does not inhibit the mechanism from working or being usable, however, because the location-service database model is purely an abstract concept. What's important is that the route-resolving Proxy be able to lookup and replace an AoR it is authoritative for, to a Registered Contact URI, such that the resultant Request URI matches what the IP-PBX expects to receive. It is "safe" to do this because the explicitly Registered Contact URI of the [draft-gin] REGISTER request had no user portion, and thus no possible URI user parameters. As defined in [draft-gin], the Contact URI parameters of the REGISTER are saved and reused, but not URI user parameters. There are multiple ways of describing the logical AoR instantiation and Contact URI expansion rules. They could be described as covering every possible ABNF expansion, such that every possible user and parameter logically exists in the location-service database (but obviously not physically exists). Or it could be described as only the phone-context value itself being an "AoR" entry and Contact URI expansion, with a policy to allow any and all user names and parameters to be copied instead of replaced by the Contact URI. This remains an open issue for discussion, as discussed in section 8. Regardless, for an implicitly Registered SIP AoR with a URI user portion matching the syntax outlined for "local-number" TEL URIs in [RFC3966]: the Contact is expanded following the other AoR models, EXCEPT that all URI user parameters are also included. For example, if the logically provisioned "AoR" from the previous examples were: "sip:12345;ext=678;phone-context=+1212555@ssp.example.com", it would logically get an automatically generated Contact value of and if the AoR were "sip:12345;ext=678;phone- context=ssp.example.com@ssp.example.com", the resultant Contact value would be . Note that in practice it is not uncommon to receive a SIP URI which does not strictly comply with the formatting rules of [RFC3966], but is processed as if it were, based on local policies. That is legal, of course, but from a logical perspective the SIP URI is actually retargeted or transformed into the syntactically valid form following [RFC3966], and that form MUST be the one used for routing, Contact URI expansions, etc. Likewise, if the URI were a TEL URI, Kaplan Expires - April 2011 [Page 6] Internet-Draft SIP MARTINI with OLIVE October 2010 it MUST be logically transformed into a SIP URI of the SSP's domain as defined in section 19.1.6 of [RFC3261], with an appropriate phone-context, before executing the rules. As in [draft-gin], aside from the "bnc" parameter, all URI parameters present in the Contact URI in the REGISTER message MUST be copied to the Contact value stored in the location service. Note that the location service database, and any entry model described here, is purely an abstract concept used by [RFC3261], [draft-gin], and this document; an actual implementation may do whatever it likes internally, so long as the external behavior follows the model. For example, if an SSP does not maintain any specific knowledge of the Local Number dial-plan, but simply performs prefix or default routing for an Enterprise's private extensions, the SSP could just route based on the E.164 phone- context field value without having a separate physical "AoR" database entry for each local number of that context. 6. SSP Processing of Inbound Non-E.164 Requests The SSP Proxy/Registrar (or equivalent entity) performs traditional Proxy/Registrar behavior, based on the logical mapping described in Section 5 and [draft-gin]. 7. Interaction with Other Mechanisms The following sections describe the means by which this mechanism interacts with relevant REGISTER-related extensions currently defined by the IETF. Currently, the descriptions are somewhat informal, and omit some details for the sake of brevity. If the MARTINI working group expresses interest in furthering the mechanism described by this document, they will be fleshed out with more detail and formality. 7.1. Globally Routable User-Agent URIs (GRUU) The GRUU mechanism for this document's mechanism works exactly the same way as defined in [draft-gin]. The GIN GRUU mechanism has no dependency on the AoR being an E.164. 7.2. Registration Event Package The Registration Event Packet behavior for this document's mechanism works exactly the same way as defined in [draft-gin]. The [draft- gin] reg-event model has no dependency on the AoR being an E.164. Kaplan Expires - April 2011 [Page 7] Internet-Draft SIP MARTINI with OLIVE October 2010 There is, however, an issue for Local-Numbers, if the SSP does not actually know the full list of Local-Number user names in the given phone-context scope. In such a case, it is TBD for how to handle this. This remains an open issue for discussion, as discussed in section 8. 7.3. Non-Adjacent Contact Registration (Path) and Service Route Discovery The Path and Service-Route behavior and considerations for this document's mechanism are exactly the same as defined in [draft-gin]. The [draft-gin] Path and Service-Route model has no dependency on the AoR being an E.164. 8. Open Issues This document has several open issues, which were noted previously. They center around the handling of Local-Numbers. Local-Numbers are difficult because they are doubly-scoped: once at the URI level by the domain name, and internally by the phone-context URI user parameter. The authoritative system for the Local-Number user portion (the system(s) which knows what they are and how to process them) is not necessarily identified by the URI's domain name, but rather may be identified by the phone-context's value. If the phone-context identifies the SSP domain, all's well - but that's rarely the case. More likely is that it identifies an E.164 number, or a sub-domain of the SSP, or another domain entirely. This causes issues with certain functions such as the reg-event package, which has been identified as an open issue. 9. Examples These will be fleshed out more in later versions of the draft, with explanations of the processing performed at each step. For the time being, they just show the basic syntax described above. Kaplan Expires - April 2011 [Page 8] Internet-Draft SIP MARTINI with OLIVE October 2010 9.1. Usage Scenario: Basic Registration case This example shows a basic bulk REGISTER transaction, followed by an INVITE addressed to one of the registered terminals, for a Local- Number AoR. Internet SSP PBX | | | | |REGISTER | | |Contact:| | |<--------------------------------| | | | | |200 OK | | |-------------------------------->| | | | |INVITE | | |sip:1234;ext=678 | | | ;phone-context=+1212555 | | | @ssp.example.com | | |------------------------------->| | | | | | |INVITE | | |sip:1234;ext=678 | | | ;phone-context=+1212555 | | | @198.51.100.3;f=b | | |-------------------------------->| REGISTER sip:ssp.example.com SIP/2.0 Via: SIP/2.0/UDP 198.51.100.3:5060;branch=z9hG4bKnashds7 Max-Forwards: 70 To: From: ;tag=a23589 Call-ID: 843817637684230998sdasdh09 CSeq: 1826 REGISTER Proxy-Require: gin Require: gin Supported: path Contact: Expires: 7200 Content-Length: 0 Kaplan Expires - April 2011 [Page 9] Internet-Draft SIP MARTINI with OLIVE October 2010 INVITE sip:1234;ext=678;phone-context=+1212555 @ssp.example.com SIP/2.0 Via: SIP/2.0/UDP foo.example;branch=z9hG4bKa0bc7a0131f0ad Max-Forwards: 69 To: From: ;tag=456248 Call-ID: f7aecbfc374d557baf72d6352e1fbcd4 CSeq: 24762 INVITE Contact: Content-Type: application/sdp Content-Length: ... INVITE sip:1234;ext=678;phone-context=+1212555 @198.51.100.3;f=b SIP/2.0 Via: SIP/2.0/UDP foo.example;branch=z9hG4bKa0bc7a0131f0ad Via: SIP/2.0/UDP ssp.example.com;branch=z9hG4bKa45cd5c52a6dd50 Max-Forwards: 68 To: From: ;tag=456248 Call-ID: 7ca24b9679ffe9aff87036a105e30d9b CSeq: 24762 INVITE Contact: Content-Type: application/sdp Content-Length: ... 10. IANA Considerations This document makes no request of IANA. 11. Security Considerations This section is still TBD, but it should follow/have the same issues as [draft-gin]. 12. Acknowledgements Thanks to Adam Roach for providing text copied from [draft-gin]. Kaplan Expires - April 2011 [Page 10] Internet-Draft SIP MARTINI with OLIVE October 2010 13. Informative References [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [RFC3263] Rosenberg, J., Schulzrinne, H., "Session Initiation Protocol (SIP): Locating SIP Servers", RFC 3263, June 2002. [RFC3327] Willis, D., and Hoeneisen, B., "Session Initiation Protocol (SIP) Extension Header Field for Registering Non-Adjacent Contacts", RFC 3327, December 2002. [RFC3455] Garcia-Martin, M., Henrikson, E., and Mills, D., "Private Header (P-Header) Extensions to the Session Initiation Protocol (SIP) for the 3rd-Generation Partnership Project (3GPP)", RFC 3455, January 2003. [RFC3608] Willis, D., and Hoeneisen, B., "Session Initiation Protocol (SIP) Extension Header Field for Service Route Discovery During Registration", RFC 3608, October 2003. [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966, December 2004. [RFC4244] Barnes, M. (ed.), "An Extension to the Session Initiation Protocol (SIP) for Request History Information", RFC 4244, November 2005. [RFC5486] Malas, D., and Meyer, D., "Session Peering for Multimedia Interconnect (SPEERMINT) Terminology", RFC 5486, March 2009. [draft-gin] Roach, A. B., "Registration for Multiple Phone Numbers in the Session Initiation Protocol (SIP)", draft-ietf- martini-gin-01, April 2010. [draft-4244bis] Barnes, M., et al, "An Extension to the Session Initiation Protocol (SIP) for Request History Information", draft-ietf-sipcore-rfc4244bis-00, February 2010. Kaplan Expires - April 2011 [Page 11] Internet-Draft SIP MARTINI with OLIVE October 2010 Author's Address Hadriel Kaplan Acme Packet 71 Third Ave. Burlington, MA 01803, USA Email: hkaplan@acmepacket.com Appendix A - Why Local-Numbers may need processing by SSPs There is some debate about how a non-E.164 AoR could even be received by the SSP for processing to begin with. This section describes how such could be the case. It should be noted that this document only deals with SIP AoRs of the same URI domain name as that of the REGISTER's To URI - namely the SSP's domain. A SIP Request targeted to a Local-Number could require processing by the SSP because: - The SSP provides IP-Centrex type services for some of the AoRs of an Enterprise, for example for small branches, while providing SIP-Trunk service to the main IP-PBX(s). Requests from the IP-Centrex UAs will thus be targeted to Local-numbers as they are received by the SSP Proxy on their way to the IP- PBX. - The SSP provides inbound extension dialing, for example by offering private calling-card services, such that a E.164 number call is terminated by an Application Server of the SSP which authenticates the caller belongs to an Enterprise and then allows private extension dialing, as a UAC, thereby originating a new SIP session Request using a Local-Number target. - The SSP provides inter-branch private dialing, by routing on some number of leading digits of a Local-Number. There are other possibilities as well, of course, but this section is only intended to provide some basic rational for why it is possible for a local-number AoR to be used and appear in the SSP. Kaplan Expires - April 2011 [Page 12]