--- 1/draft-ietf-sipcore-location-conveyance-02.txt 2010-07-13 01:10:38.000000000 +0200 +++ 2/draft-ietf-sipcore-location-conveyance-03.txt 2010-07-13 01:10:38.000000000 +0200 @@ -1,28 +1,29 @@ -SIPCORE Working Group James Polk +Network Working Group James Polk Internet Draft Cisco Systems -Expires: August 12, 2010 Brian Rosen -Intended Status: Standards Track (PS) NeuStar - Feb 12, 2010 +Expires: January 12, 2011 Brian Rosen +Intended Status: Standards Track (PS) Jon Peterson + NeuStar + July 12, 2010 Location Conveyance for the Session Initiation Protocol - draft-ietf-sipcore-location-conveyance-02.txt + draft-ietf-sipcore-location-conveyance-03.txt Abstract This document defines an extension to the Session Initiation Protocol (SIP) to convey geographic location information from one SIP entity to another SIP entity. The extension covers end-to-end - conveyance as well as location-based routing, where SIP servers - make routing decisions based upon the location of the user agent - client. + conveyance as well as location-based routing, where SIP + intermediaries make routing decisions based upon the location of the + user agent client. 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. @@ -31,21 +32,21 @@ 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 Aug 12, 2010. + This Internet-Draft will expire on Jan 12, 2011. Copyright Notice Copyright (c) 2010 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 @@ -64,1243 +65,579 @@ the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Conventions and Terminology used in this document . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2.1 Scoping and Describing a Target verses a Device . . . . . 4 - 3. Overview of SIP Location Conveyance . . . . . . . . . . . . . 5 - 4. SIP Modifications for Geolocation Conveyance . . . . . . . . 8 - 4.1 The Geolocation Header . . . . . . . . . . . . . . . . . 8 - 4.2 424 (Bad Location Information) Response Code . . . . . . 12 - 4.3 The Geolocation-Error Header . . . . . . . . . . . . . . 12 - 4.4 The 'geolocation' Option Tag . . . . . . . . . . . . . . 24 - 4.5 Using sip/sips/pres as a Dereference Scheme . . . . . . . 24 - 5. Geolocation Examples . . . . . . . . . . . . . . . . . . . . 25 - 5.1 Location-by-value (Coordinate Format) . . . . . . . . . . 26 - 5.2 Location-by-reference . . . . . . . . . . . . . . . . . . 27 - 6. SIP Element Behavior . . . . . . . . . . . . . . . . . . . . 28 - 6.1 UAC Behavior . . . . . . . . . . . . . . . . . . . . . . 28 - 6.2 UAS Behavior . . . . . . . . . . . . . . . . . . . . . . 33 - 6.3 Proxy Behavior . . . . . . . . . . . . . . . . . . . . . 38 - 7. Geopriv Privacy Considerations . . . . . . . . . . . . . . . 42 - 8. Security Considerations . . . . . . . . . . . . . . . . . . . 43 - 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 45 - 9.1 IANA Registration for New SIP Geolocation Header . . . . 45 - 9.2 IANA Registration for New SIP 'geolocation' Option Tag . 45 - 9.3 IANA Registration for New 424 Response Code . . . . . . . 45 - 9.4 IANA Registration for New SIP Geolocation-Error Header . 45 - 9.5 IANA Registration for New SIP Geolocation-Error Codes . . 46 - 9.6 IANA Registration of Location URI Schemes . . . . . . . . 47 - 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 47 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 48 - 11.1 Normative References . . . . . . . . . . . . . . . . . 48 - 11.2 Informative References . . . . . . . . . . . . . . . . . 49 - Author Information . . . . . . . . . . . . . . . . . . . . . 49 - Appendix A. Requirements for SIP Location Conveyance . . . . 50 + 3. Overview of SIP Location Conveyance . . . . . . . . . . . . . 3 + 4. SIP Modifications for Geolocation Conveyance . . . . . . . . 7 + 4.1 The Geolocation Header . . . . . . . . . . . . . . . . . 7 + 4.2 424 (Bad Location Information) Response Code . . . . . . 9 + 4.3 The Geolocation-Error Header . . . . . . . . . . . . . . 10 + 4.4 The 'geolocation' Option Tag . . . . . . . . . . . . . . 12 + 4.5 Location URIs in Message Bodies . . . . . . . . . . . . . 12 + 4.6 Location URIs Allowed . . . . . . . . . . . . . . . . . . 12 + 5. Geolocation Examples . . . . . . . . . . . . . . . . . . . . 13 + 5.1 Location-by-value (Coordinate Format) . . . . . . . . . . 13 + 5.2 Two Locations Composed in Same Location Object Example . 14 + 6. Geopriv Privacy Considerations . . . . . . . . . . . . . . . 16 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 17 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 18 + 8.1 IANA Registration for New SIP Geolocation Header . . . . 19 + 8.2 IANA Registration for New SIP 'geolocation' Option Tag . 19 + 8.3 IANA Registration for New 424 Response Code . . . . . . . 19 + 8.4 IANA Registration for New SIP Geolocation-Error Header . 19 + 8.5 IANA Registration for New SIP Geolocation-Error Codes . . 19 + 8.6 IANA Registration of Location URI Schemes . . . . . . . . 20 + 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 + 10.1 Normative References . . . . . . . . . . . . . . . . . 21 + 10.2 Informative References . . . . . . . . . . . . . . . . . 22 + Author Information . . . . . . . . . . . . . . . . . . . . . 22 + Appendix A. Requirements for SIP Location Conveyance . . . . 23 1. Conventions and Terminology used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described - in [RFC2119]. - - The following terms and acronyms used throughout this document are - defined here: - - LbyV: Location-by-Value - - Location Generator (LG): The entity that initially determines or - gathers the location of the Target and creates Location - Objects describing the location of the Target [RFC3693]. - - Location Inserter: a role created in this document describing the - entity that included location in a SIP request, either by-value - or by-reference (i.e., including a location URI). - - Location Object (LO): An object conveying location information - (and possibly privacy rules) to which Geopriv security - mechanisms and privacy rules are to be applied [RFC3693]. - - Location Recipient (LR): The entity that receives location - information. It may have asked for this location explicitly - (by sending a query to a location server), or it may receive - this location asynchronously [RFC3693]. - - Location Server (LS): The entity to which a LG publishes location - objects, the recipient of queries from location receivers, and - the entity that applies rules designed by the rule maker - [RFC3693]. - - A Location Server is also an entity that retains Target Location - Objects that are dereferenced by Location Recipients via SIP - SUB/NOT transactions. - - Target: A person or other entity whose location is communicated by - a Geopriv Location Object [RFC3693]. - - Using Protocol: A protocol that carries a Location Object [RFC3693]. + in [RFC2119]. This document furthermore uses numerous terms defined + in RFC 3693 [RFC3693], including Location Objection, Location + Recipient, Location Server, Target, and Using Protocol. 2. Introduction - This document describes how geolocation can be "conveyed" in a SIP - request from one SIP entity unsolicited to another entity using SIP - [RFC3261]. Here, "Location" is a description of the physical - geographical area where something currently exists. This - "something" is a Location Target. Note that this information is not - solicited (i.e., asked for or requested) by the entity that receives - it. The mechanism in this document does not define how one SIP - entity requests the location of another SIP entity to be returned in - a response. - - Geographic location in the IETF is discussed in RFC 3693 (Geopriv - Requirements) [RFC3693]. It defines a "Target" as the entity whose - location is being transmitted over IP. A [RFC3693]-defined "Using - Protocol" describes how a "Location Server" transmits a "Location - Object" to a "Location Recipient" while maintaining the contained - privacy intentions of the Target intact. This document describes a - SIP extension to carry a Location Object and how it complies with - the Using Protocol requirements in RFC 3693. - - Common terms are in Section 1. Section 3 provides an overview of SIP - location conveyance. Section 4 details the extensions to SIP - necessary to accomplish location conveyance. Section 5 gives decode - examples of geolocation within SIP requests, both with a value and - with a reference. Section 6 articulates the SIP element type - behaviors for location conveyance. Section 7 discusses Geopriv - privacy considerations. Section 8 discusses security - considerations. Section 9 IANA registers the modifications made to - SIP by this document in section 4. - -2.1 Scoping and Describing a Target verses a Device - - Geographic location is related to a device, not to a user as far as - this document is concerned. When a user is logged onto a device, - the two entities are bound and can be said to be the same Location - Target - as far as this document is concerned. This document - specifies how one UA uses a SIP request to convey its whereabouts to - another UA. - - Devices have a element in a presence document for - identification, which is usually its MAC (or equivalent) address. - This element is not always present in the presence document. As - will be mentioned in Section 6.1, there are different ways to - identify a Target, including in the form of a SIP Contact address - (as defined by RFC 3261) or a pseudonym. - - In SIP, we often interchangeably use the terms 'Alice' and '(the) - UA' to mean the same thing. Sometimes we refer to 'Alice the user', - which means the human, and not the SIP instance of an endpoint. - When we talk about 'Alice' without clarifying we are talking about - the human user, we implicitly bind Alice and the UA as the same - entity, even if she is identified with a pseudonym in SIP signaling. - This is common practice throughout most SIP documents. The Geopriv - architecture does not make this user-to-device binding very often in - its documentation. - - The Geopriv architecture describes Location Targets (Target) and - Location Recipients (LR), which can easily fit into the SIP model by - having Alice send Bob her location. In this example, Alice is the - Target and Bob is the Location Recipient. Here, we are not - concerned with how a UA learns its location, either by being told - where it is or from an onboard GPS. This is exclusively within the - Geopriv architecture. - - In this document, we allow SIP servers to insert the Target's - location while processing the SIP request towards the destination. - In this scenario, the originating UA (Alice) is always the Target. - The location inserting SIP server is not the Target. - - We also allow SIP servers to be consumers of location, i.e., an LR, - for the purposes of making routing decisions based on the location - in a SIP request. - - This document maintains the practice of other SIP documents by: - - o a Target associated with a user has the inherited identity of - that user (i.e., Alice or Bob). The SIP-URI will generally be - similar to (or be) a Contact address, which could be a pseudonym - for the user; (see Section 6.1 for more on this) - - o Alice is a UA, as is Bob. Understanding SIP signaling will - determine which is the UAC and which is the UAS. We specify - later that location can only be in a SIP request, even if that - request contains the location of more than one Target. + Session Initiation Protocol (SIP) [RFC3261] creates, modifies and + terminates multimedia sessions. SIP carries certain information + related to a session while establishing or maintaining calls. This + document defines how SIP conveys geographic location information of + a Target (Target) to a Location Recipient (LR). SIP acts as a Using + Protocol of location information, as defined in RFC 3693. - o a Target without an identifiable user associated with it is not - necessarily user-less, the binding is just not obvious or could - purposely be a pseudonym (for security reasons) . The SIP-URI - will be more like a fully qualified Call-ID (unique through space - and time, as defined by RFC 3261); + In order to convey location information, this document specifies a + new SIP header, the Geolocation header, which carries a reference to + a Location Object. That Location Object may appear in a MIME body + attached to the SIP request, or it may be a remote resource in the + network. - o a Target which is user-less will likely have a SIP-URI, where the - user-part of the address is the MAC (or equivalent) address of - the device, or a pseudo-string id, but still a URI for this - document's purpose; + Note that per RFC 3693, a Target is an entity whose location is + being conveyed. Thus, a Target could be a SIP user agent (UA), some + other IP device (a router or a PC) that does not have a SIP stack, a + non-IP device (a person or a black phone) or even a + non-communications device (a building or store front). In no way + does this document assume that the SIP user agent client which sends + a request containing a location object is necessarily the Target. + The location of a Target conveyed within SIP typically corresponds + to that of a device controlled by the Target, for example, a mobile + phone, but such devices can be separated from their owners, and + moreover, in some cases the user agent may not know its own + location. - The above is informative in nature. + In the SIP context, a location recipient will most likely be a SIP + UA, but due to the mediated nature of SIP architectures, location + information conveyed by a single SIP request may have multiple + recipients, as any SIP proxy server in the signaling path that + inspects the location of the Target must also be considered a + Location Recipient. In presence-like architectures, an intermediary + that receives publications of location information and distributes + them to watchers acts as a Location Server per RFC 3693. This + location conveyance mechanism can also be used to deliver URIs point + to such Location Servers where prospective Location Recipients can + request Location Objects. 3. Overview of SIP Location Conveyance + An operational overview of SIP location conveyance can be shown in 4 + basic diagrams, with most applications falling under one of these + basic use cases. - The concept of conveying location in SIP is fairly straightforward. - Location is conveyed directly or indirectly from a transmitting SIP - entity to a receiving SIP entity. When location is conveyed - directly, it is conveyed as a value contained within the SIP - request, as in Figure 1. + Each diagram has Alice and Bob as UAs. Alice is the Target, and Bob + is an LR. A SIP intermediary appears in some of the diagrams. Any + SIP entity that receives and inspects location information is an LR, + therefore any of the diagrams the SIP intermediary receives the SIP + request is potentially an LR - though that does not mean such an + intermediary necessarily has to route the SIP request based on the + location information. In some use cases, location information + passes through the LS on the right of each diagram. - Alice Bob LS - | | | + Alice SIP Intermediary Bob LS + | | | | | Request w/ Location | | - |------------------------>| | + |----------------------------------->| | | | | | Response | | - |<------------------------| | - | | | + |<-----------------------------------| | + | | | | Figure 1. Location Conveyed by Value - When location is conveyed indirectly, analogous to Content - Indirection [RFC4483], Bob receives (from Alice) a location URI and - must make an additional request - here called a dereference - to - learn Alice's actual location from a Location Server (LS) - identified in the location URI, as in Figure 2. + In Figure 1, Alice is both the Target and the LS that is conveying + her location directly to Bob, who acts as an LR. This conveyance is + point-to-point - it does not pass through any SIP-layer + intermediary. A Location Object appears by-value in the initial SIP + request as a MIME body, and Bob responds to that SIP request as + appropriate. There is a 'Bad Location Information' response code + introduced within this document to specifically inform Alice if she + conveys bad location to Bob (i.e., Bob "cannot parse the location + provided", or "there is not enough location information to determine + where Alice is"). - Alice Bob LS - | | | + Alice SIP Intermediary Bob LS + | | | | | Request w/ Location URI | | - |------------------------>| | - | | Dereference Request | - | |---------------------->| - | | | - | | Dereference Response | - | |<----------------------| - | Response | (includes location) | - |<------------------------| | + |----------------------------------->| | + | | Dereference | + | | Request | + | (To: Location URI) | + | |---------------->| | | | + | | Dereference | + | | Response | + | (includes location) | + | |<----------------| + | Response | | + |<-----------------------------------| | + | | | | - Figure 2. Location Conveyed by Reference - - Many protocols can be used for this dereference transaction, but - this is usually determined by the scheme of the location URI in the - SIP request. In other words, if the location URI is a SIPS: URI, - then SIPS would be used to contact the LS to make the dereference. + Figure 2. Location Conveyed as a Location URI - The location "value" in this SIP extension is in the form of a - "Presence Information Data Format - Location Object", or PIDF-LO, as - described in [RFC4119]. A PIDF-LO is an XML scheme specifically for - carrying the geographic location of a Target. LbyV refers to a UA - including a PIDF-LO as a message body part of a SIP request, sending - that Location Object to another SIP element. A UA can included a - location URI in a SIP request header field, pointing at a Location - Server, which can be dereferenced by a Location Recipient of this - location URI to retrieve Alice's Location Object, always in the form - of a PIDF-LO. + In Figure 2, location is conveyed indirectly, via a Location URI + carried in the SIP message (more of those details later). If Alice + sends Bob this Location URI, Bob will need to dereference the URI - + analogous to Content Indirection [RFC4483] - in order to request the + location information. In general, the LS provides the location value + to Bob instead of Alice directly. From a user interface + perspective, Bob the user won't know that this information was + gathered from an LS indirectly rather than culled from the SIP + request, and practically this does not impact the operation of + location-based applications. - To accomplish location conveyance in SIP, a new SIP header field, - Geolocation, is created and described in this document. The - Geolocation header field contains a URI that points to where the - location is for the location Target, either in the body of the SIP - request itself, or on a Location Server. A URI to help entities - parse for the location in a SIP request will (always) get this in - the form of a "cid:" URI (Content Identification), as defined in - [RFC2392]. + Alice SIP Intermediary Bob LS + | | | | + | Request | | | + | w/Location | | | + |--------------->| | | + | | Request | | + | | w/Location | | + | |------------------>| | + | | | | + | | Response | | + | |<------------------| | + | Response | | | + |<---------------| | | + | | | | - If the URI in the Geolocation header field is a scheme other than - "cid:", a dereference transaction (see Figure 2) is necessary. This - document describes how a SIP presence subscription [RFC3856] can be - used as a dereference protocol to retrieve the PIDF-LO for the - Target (see Section 4.5). + Figure 3. Location Conveyed though a SIP Intermediary - Location can be inserted in a SIP request by a SIP server as well as - by a UA. This document offers guidance on this practice. This - document also describes how a location recipient can determine which - entity included a specific location, as more than one location can - be conveyed in a given SIP request. Section 4 gets into guidance and - limitations of this behavior. + In Figure 3, we introduce the idea of a SIP intermediary into the + example to illustrate the role of proxying in the location + architecture. This intermediary could be a SIP proxy or it could be + a back-to-back-user-agent (B2BUA). In this message flow, the SIP + intermediary may act as a LR, in addition to Bob. The primary use + case for intermediaries consuming location information is + location-based routing. In this case, the intermediary chooses a + next hop for the SIP request by consulting a specialized location + service which selects forwarding destinations based on geographical + location. In this case, the intermediary acts as a Location + Recipient. - A new error response (424 Bad Location Information) is also defined - in this document. Within this response is a new header field - indicating location-based errors, called the Geolocation-Error - header field. This header field has various codes that provide - additional information about the type of location error experienced - by a Location Recipient, separated into actionable categories to be - taken by the UAC. + However, it can be the case that the SIP intermediary receives a + request with location information (conveyed either by-value or + by-reference) and does not know or care about Alice's location, or + support this extension, and merely passes it on to Bob - in this + case, the intermediary does not act as a Location Recipient. - Because more than one SIP entity can insert location, when - considering SIP as an end-to-end protocol, there needs to be a means - of identifying which location within a message of multiple locations - was considered bad by a location recipient - if that were to occur. - The ability to tell which entity (identified by host-id) inserted a - specific location is extremely important. Not only does this allow - each location error to be Targeted at a particular inserter of a - specific location object, but it also allows error recipients to - understand when the location they inserted was not at fault, and - that a received error is not meant for them. This optimization is - necessary, otherwise each location error would be a blanket error to - every entity upstream in the signaling path. + Note that an intermediary does not have to perform location-based + routing in order to be location recipient. It could be the case that + a SIP intermediary which does not perform location-based routing but + does care when Alice includes her location; for example, it could + care that the location information is complete or that it correctly + identifies where Alice is. The best example of this is + intermediaries that verify location information for emergency + calling, but it could also be for any location based routing - e.g., + contacting Pizza Hut, making sure that organization has Alice's + proper location in the initial SIP request. - Just as location can be conveyed by more than one entity about the - same Target, there can be more than one location recipient along a - request's path. It is possible to route SIP requests based on the - location of the Target (i.e., source based routing, instead of - normal destination based routing). This means SIP servers can be - location recipients. If this is not desired by a Location Inserter, - then the Location Inserter can also include a separate indication in - the Geolocation header field showing that this usage is not desired. + If the SIP intermediary rejects the message due to unsuitable + location information (we are not going to discuss any other reasons + in this document, and there are many), the SIP response will + indicate there was 'Bad Location Information' in the SIP request, + and provide a location specific error code indicating what Alice + needs to do to send an acceptable request. - Location Inserters have the ability to provide instructional - parameters about location it has inserted. These are hints to - downstream entities on how the location information in the message - was originated, intended and is to be used. + Alice SIP Intermediary Bob LS + | | | | + | Request | | | + | w/Location | | | + |--------------->| | | + | | | | + | Rejected | | | + | w/New Location | | | + |<---------------| | | + | | | | + | Request | | | + | w/New Location | | | + |--------------->| | | + | | Request | | + | | w/New Location | | + | |------------------>| | + | | | | - Transport Layer Security is expected when a request contains a - Target's location. Some implementations will choose to have S/MIME - for integrity protection, or to encrypt message bodies from source - to destination(s). + Figure 4. SIP Intermediary Replacing Bad Location - This document creates a new option tag: geolocation, to indicate - support for this extension by UAs. + In this last use case, the SIP intermediary wishes to include a + Location Object indicating where it understands Alice to be. Thus, + it must inform her user agent what location she should include in + any subsequent SIP request that contains her location. In these + cases, the intermediary can reject Alice's request, through the SIP + response, convey to her the best way to repair the request in order + for the intermediary to accept it. - The new header field, the header parameters, the new option tag, the - new error response, and Geolocation-Error codes are defined in - Section 4, each of which are IANA registered by this document. + Overriding location information provided by the user requires a + deployment where an intermediary necessarily knows better than an + end user - after all, it could be that Alice has an on-board GPS, + and the SIP intermediary only knows her nearest cell tower. Which is + more accurate location information? Currently, there is no way to + tell which entity is more accurate, or which is wrong - for that + matter. This document will not specify how to indicate which + location is more accurate than another. If desired, intermediaries + may furthermore allow both Alice's internally generated location, as + well as the SIP intermediary's determination of where Alice, to + appear in the same SIP request (the resubmitted one), and permit + that to be forwarded to Bob. This case is discussed in more detail + in section 4.2 of this document. - RFC 3693 demands that a transmitted location be required to maintain - privacy considerations. This document maintains all of the privacy - considerations defined by RFC 3693, plus adds an intended usage - indication within the SIP Geolocation header field. This increases - the considerations for recipients not to inspect a Target's location - when they are not the intended location recipient. + As an aside, it is not envisioned that any SIP-based emergency + services request (i.e., IP-911, or 112 type of call attempt) will + receive a corrective 'Bad Location Information' response from an + intermediary. Most likely, the SIP intermediary would in that + scenario act a B2BUA and insert into the request by-value any + appropriate location information for the benefit of Public Safety + Answering Point (PSAP) call centers to expedite call reception by + the emergency services personnel; thereby, minimizing any delay in + call establishment time. The implementation of these specialized + deployments is, however, outside the scope of this document. 4. SIP Modifications for Geolocation Conveyance - The following sections detail the standards track modifications - to SIP for Location Conveyance. + The following sections detail the modifications + to SIP for location conveyance. -4.1 The Geolocation Header Field +4.1 The Geolocation Header - This document defines Geolocation as a new SIP header field + This document defines "Geolocation" as a new SIP header field registered by IANA, with the following ABNF [RFC5234]: - Geolocation = "Geolocation" HCOLON (locationArg - *COMMA locationArg) + Geolocation = "Geolocation" HCOLON locationArg + (*COMMA locationArg) locationArg = locationValue / routing-param - locationValue = LAQUOT locationURI RAQUOT SEMI inserted-param + locationValue = LAQUOT locationURI RAQUOT *(SEMI geoloc-param) locationURI = sip-URI / sips-URI / pres-URI / cid-url ; (from RFC 2392) / absoluteURI ; (from RFC 3261) - inserted-param = "inserted-by" EQUAL geoloc-inserter - geoloc-inserter = DQUOTE hostport DQUOTE - / gen-value ; (from RFC 3261) - geoloc-param = "used-for-routing" / generic-param ; - (from RFC 3261) + geoloc-param = generic-param; (from RFC 3261) routing-param = "routing-allowed" EQUAL "yes" / "no" sip-URI, sips-URI and absoluteURI are defined according to [RFC3261]. The pres-URI is defined in [RFC3859]. - The cid-url is defined in [RFC2392] to locate message body - parts. This URI type is present in a SIP request when location - is conveyed as a value. + The cid-url is defined in [RFC2392] to locate message body parts. + This URI type is present in a SIP request when location is conveyed + as a MIME body in the SIP message. - Other protocols used in the location URI MUST be reviewed against + Other URI schemas used in the location URI MUST be reviewed against the RFC 3693 [RFC 3693] criteria for a Using Protocol. - The Geolocation header field MAY have one or more locationValues. - SIP servers inserting a locationValue MUST add the new value as the - last locationValue in the Geolocation header field (i.e., the last - locationValue in the header field is the most recent one added to - the message). Placement of the "routing-allowed" parameter, when - present, MUST be the last header field value in the Geolocation - header field. - - A locationValue has the following independent header field - parameters, - - o the "inserted-by=" parameter provides the hostport - (alice.example.com -- which is the same as the "sent-by" - parameter in a Via header field, with or without a port number) - of the SIP entity that inserted this locationValue into the - request. If a Location Recipient has determined a supplied - location is in error, as there can be more than one location in - any request, the "inserted-by=" parameter is copied into the - locationErrorValue in the response indicating the location error, - and to whom the error is for. Hence, this "inserted-by=" - parameter MUST be present in each locationValue. If an entity - receives an Geolocation-Error with a hostport that does not - identify this entity, the Geolocation-Error MUST be ignored. - - o the "used-for-routing" parameter to inform recipients that the - location in this locationValue was used to route the message - towards the ultimate destination UAS. "used-for-routing" can - occur more than once along the request's path. Because - locationValues are inserted as last inserted is last in the - header field, the last locationValue is the most recent one added - to the message. This also gives the "used-for-routing" header - field parameter added meaning - as the receiving SIP entity knows - which location URI the message was routed upon. - - Each locationValue MUST contain exactly one "inserted-by" parameter, - indicating which SIP entity added the locationValue to the SIP - request. - - There MUST NOT be more than one "inserted-by=" parameter or one - "used-for-routing" parameter in the same locationValue. However, - there can be more than one locationValue in the same Geolocation - header field. - - The "routing-allowed" header field parameter is a global parameter - over any (and all/each) locationValues in the Geolocation header - field. The placement of the parameter is outside any locationValue, - appears only once, and is always last in the header field value. The - routing-allowed parameter MAY be present when no locationValue is - present. This scenario sets the routing-allowed policy downstream - along the request's signaling path. + The Geolocation header field has zero or one locationValue, but + MUST NOT contain more than one locationValue. - This header field parameter only has the values "=yes" or "=no". - When this parameter is "=yes", any locationValue can be used for - routing decisions along the downstream signaling path by - intermediaries. + The placement of the "routing-allowed" header field parameter is + outside the locationValue, and MUST always be last in the header + field value. The routing-allowed parameter MAY be present when no + locationValue is present. This scenario sets the routing-allowed + policy downstream along the request's signaling path. This header + field parameter only has the values "=yes" or "=no". When this + parameter is "=yes", the locationValue can be used for routing + decisions along the downstream signaling path by intermediaries. When this parameter is "=no", this means no locationValue (inserted - by the originating UAC or any (or subsequent) intermediary(ies) - along the signaling path) can be used by any SIP intermediary to - make routing decisions. This behavior MUST be adhered to. Sections - 4.3 and 6.3 describe the details on what a routing intermediary does - if it believes it needs to use the location in the SIP request in - order to process the message further. + by the originating UAC or any intermediary along the signaling path + can be used by any SIP intermediary to make routing decisions. + Intermediaries that attempt to use the location information for + routing purposes in spite of this counter indication may end up + routing the request improperly as a result. Sections 4.3 describes + the details on what a routing intermediary does if it determines it + needs to use the location in the SIP request in order to process the + message further. The practical implication is that when the "routing-allowed" parameter is set to "no", if a cid:url is present in the SIP request, intermediaries MUST NOT view the location (because it is not for intermediaries to view), and if a location URI is present, intermediaries MUST NOT dereference it. UAs are allowed to view location in the SIP request even when the "routing-allowed" - parameter is set to "no". - - There MUST not be more than one routing-allowed parameter in any SIP - request, regardless of when there are cases of more than one - Geolocation header field row (i.e., more than one Geolocation - header in the SIP request, as defined in section 7.3.1 of RFC 3261). - There does not have to be any routing-allowed parameter present in a - Geolocation header value of a SIP request. However, the default - treatment of the absence of the routing-allowed parameter is as if - it were present, and set to "=no" without exception. + parameter is set to "no". An LR MUST by default consider the + "routing-allowed" header parameter as set to "no", with no + exceptions, unless the header field value is set to "yes". If a routing-allowed parameter is parsed as set to "=yes", an - implementation MUST parse the rest of the SIP header for another + implementation MUST parse the rest of the SIP headers for another instance of the Geolocation header value to determine if there is another instance of the routing-allowed parameter set to "=no". If this is the case, the behavior MUST be to process the "=no" indication only, and ignore the "=yes". This document defines the Geolocation header field as valid in the following SIP requests: INVITE [RFC3261], REGISTER [RFC3261], OPTIONS [RFC3261], BYE [RFC3261], UPDATE [RFC3311], INFO [RFC2976], MESSAGE [RFC3428], REFER [RFC3515], SUBSCRIBE [RFC3265], NOTIFY [RFC3265], - PUBLISH [RFC3903] and PRACK [RFC3262] - - Discussing location using the PUBLISH request is out of scope - for this document since it is part of Presence, therefore, for - completeness, Table 1 shows PUBLISH is to support Location - Conveyance via this extension, but is not discussed further. + PUBLISH [RFC3903], PRACK [RFC3262] The following table extends the values in Tables 2 and 3 of RFC 3261 [RFC3261]. Header field where proxy INV ACK CAN BYE REG OPT PRA ---------------------------------------------------------------- Geolocation R ar o - - o o o o Header field where proxy SUB NOT UPD MSG REF INF PUB ---------------------------------------------------------------- Geolocation R ar o o o o o o o Table 1: Summary of the Geolocation Header Field - The Geolocation header field MAY be included in any one of the above - requests by a UA. A proxy MAY add the Geolocation header field, - but MUST NOT modify any pre-existing locationValue, including any - associated header field parameters within an existing Geolocation - header field value, unless one of the existing locationValues is - used to retarget the request towards a new destination UAS. This is - discussed in section 6.3. - - [RFC3261] states message bodies cannot be added by proxies. - Therefore, any Geolocation header field added by a proxy MUST be in - the form of an location URI, in its own locationValue header field - value. - - A SIP proxy MAY add a Geolocation header field if one is not - present, and MAY add the "routing-allowed" parameter if not yet - present in the SIP request. When a "routing-allowed" parameter is - already present in the SIP request, a SIP server MUST NOT change the - value of the parameter (i.e., from 'yes' to 'no', or from 'no' to - 'yes'). This would override the policy set by an upstream SIP - entity (i.e., the UAC). - - Adding a new locationValue to an in-transit request is NOT - RECOMMENDED for at least two reasons, - - #1 SIP Servers are not the best geographic locators of where a - UA is; the location information that a SIP server knows might - not be the best location information available. - - #2 this document gives limited guidance as to what a Location - Recipient should do when receiving more than one location (no - instructions are given about which locationValue to use when - more than one is present), so adding a new locationValue may - lead to undesirable results. + The Geolocation header field MAY be included in any one of the + optional requests by a UA. A proxy MAY add the Geolocation header + field, but MUST NOT modify any pre-existing locationValue, including + the "routing-allowed" header field value. - Location Recipients receiving a location object, whether received - directly or as the result of a dereference, MUST honor the usage - element rules within that XML document, as defined in [RFC4119]. - Such entities MUST NOT alter the rule set. + A SIP intermediary MAY add a Geolocation header field if one is not + present - for example, when a user agent does not support the + Geolocation mechanism but their outbound proxy does and knows their + location, or any of a number of other use cases (see Figure 4 in + section 3). When adding a Geolocation header, a SIP intermediary + MAY supply the "routing-allowed" parameter if not yet present in the + SIP request. - Other modifications of the Geolocation header field MUST NOT occur - without an update to this specification. + SIP implementations are advised to pay special attention to the + policy elements for location retransmission and retention described + in RFC 4119. 4.2 424 (Bad Location Information) Response Code - This SIP extension creates a new location specific response code, - defined as follows. + This SIP extension creates a new location-specific response code, + defined as follows, 424 (Bad Location Information) The 424 (Bad Location Information) response code is a rejection of - the request due to its location contents, indicating the location - information was malformed or not satisfactory for the recipient's - purpose, or could not be dereferenced. + the request due to its location contents, indicating location + information that was malformed or not satisfactory for the + recipient's purpose, or could not be dereferenced. - Section 4.3 creates the Geolocation-Error header field to provide + A SIP intermediary can also reject a location it receives from a + Target when it understands the Target to be in a different location. + The proper handling of this scenario is for the SIP intermediary to + include the proper location in the 424 Response. This SHOULD be + included in the response as a MIME message body (i.e., a location + value), rather than as a URI; however, in cases where the + intermediary is willing to share location with recipients but not + with a user agent, a reference might be necessary. + + As mentioned in section 3 (below Figure 4), it might be the case + that the intermediary does not want to chance providing less + accurate location information than the user agent; thus it will + compose its understanding of where the user agent is in a separate + element of the same PIDF-LO message body of the SIP + response (which also contains the Target's version of where it is). + Therefore, both locations are included - each potentially with + different elements. The proper reaction of the user agent + is to generate a new SIP request that includes this composed + location object, and send it towards the original LR. SIP + intermediaries can verify that subsequent requests properly insert + the suggested location information before forwarding said requests. + + Section 4.3 describes a Geolocation-Error header field to provide more detail about what was wrong with the location information in - the request. This header field MUST be in the 424 response, - containing a locationErrorValue for each invalid locationValue in - the request (i.e., and one-for-one matching if all locationValues - in the request were bad). + the request. This header field MUST be included in the 424 response. - If more than one location is present in a request (value or location - URI), and the Location Recipient can process any of the - locationValues, a 424 MUST NOT be sent. The 424 is only appropriate - when the Location Recipient needs a locationValue and there are no - locationValues included in a SIP request that are usable by a - recipient. + The 424 is only appropriate when the Location Recipient needs a + locationValue and there are no locationValues included in a SIP + request that are usable by a recipient, or as shown in Figure 4 of + section 3, a SIP intermediary is informing the UA which location to + include in the next SIP request. A 424 MUST NOT be sent in response + to a request that lacks a Geolocation header entirely, as the user + agent in that case may not support this extension at all. A 424 (Bad Location Information) response is a final response within a transaction, and does not terminate an existing dialog. - The UA can use whatever means it knows of to verify/refresh its - location information before attempting a new request that includes - location. There is no cross-transaction awareness expected by either - the UA or any SIP intermediary as a result of this error message. - The new 424 (Bad Location Information) error code is registered with - IANA in Section 8 of this document. An initial set of - IANA-registered Geolocation-Error codes are in Section 4.3 of this - document. - -4.3 The Geolocation-Error Header Field +4.3 The Geolocation-Error Header - As discussed in Section 4.2, more granular error notifications, - specific to location errors within a received request, are required + As discussed in Section 4.2, more granular error notifications + specific to location errors within a received request are required if the UA is to know what was wrong within the original request. The Geolocation-Error header field is used for this purpose. The Geolocation-Error header field is used to convey - location-specific errors within a response. Additional - IANA-registered values must be defined in an RFC (this is the "RFC - Required" IANA policy defined in [RFC5226]). The Geolocation-Error + location-specific errors within a response. The Geolocation-Error header field has the following ABNF [RFC5234]: Geolocation-Error = "Geolocation-Error" HCOLON locationErrorValue - *(COMMA locationErrorValue) - locationErrorValue = location-error-arg SEMI - node-param SEMI inserter-param + locationErrorValue = location-error-arg location-error-arg = location-error-code *(SEMI location-error-params) location-error-code = 1*3DIGIT location-error-params = location-error-code-text / generic-param ; from RFC3261 location-error-code-text = "code" EQUAL quoted-string ; from RFC3261 - node-param = location-error-node-id - location-error-node-id = "node" EQUAL - DQOUTE hostport DQOUTE ; from RFC3261 - inserter-param = location-error-host-id - location-error-host-id = "inserter" EQUAL - DQOUTE hostport DQOUTE ; from RFC3261 - The Geolocation-Error header field MUST contain at least one + The Geolocation-Error header field MUST contain only one locationErrorValue to indicate what was wrong with the locationValue - in the corresponding request the Location Recipient determined was - bad. Each locationErrorValue contains a 3-digit error code - indicating what was wrong with the location in the request. Each - error type has a corresponding quoted error text string that is - human understandable. This text string is OPTIONAL, but RECOMMENDED - for easy understanding. - - Each locationErrorValue contains the Location Recipient identifier - (the "node=" parameter) which experienced the location error, as - well as an identifier of which SIP entity (the "inserter=" - parameter) the Location Recipient is told (in the locationValue) - added this problematic locationValue to the request. The "node=" - and "inserter=" are the domain identifier of a SIP entity, with the - ability to have the same host communicate on different ports - and - have port specific identification. This is the same information that - would be entered in the "sent-by" parameter of the Via header field - for that entity [RFC3261]. As stated in section 18 of RFC 3261, - the usage of FQDN is RECOMMENDED. Here are examples of both - locationErrorValue parameters, - - node="bob.example.com" - inserter="alice.example.com" - - Both the "node=" and "inserter=" parameters MUST be present in all - locationErrorValues in a response, unless the locationValue of the - request did not include the "inserted-by=" parameter (which is a - violation of this document). The "inserter=" parameter value is - copied from the "inserted-by=" parameter within the locationValue of - the request. This is required because a Location Recipient that - experienced a problem with the location included in a request needs - to tell the specific SIP entity which added the locationValue in - error into the original request. Since more than one SIP entity can - insert location into a request in transit, all other SIP elements - may be confused by receiving this error header field, were it to - remain generic to all entities in the response path. This - requirement means that the header field identifies the Location - Inserter who inserted the problematic locationValue, so that all - other SIP entities that read the header field know to ignore it. - This is of particular use if the original UAC did not include a - locationValue in the original SIP request, but a SIP server along - the path did insert a locationValue. The locationErrorValue would - be interpreted by each SIP entity along the original path upstream - and be processed by both the server that included the invalid - locationValue and the UAC that did not, resulting in confusion at - the UAC. - - A worse case is when both the original UAC and a SIP server along - the path included a locationValue, but there was something - wrong with only one of the locationValues. Without an - identification of the specific locationValue in error, both entities - would react, and one would react incorrectly. - - When more than one locationErrorValue is present in a - Geolocation-Error header field, they are separated by commas. - - If more than one locationErrorValue is present in a response, and - intended for the same "inserter=", each error code MUST be unique to - this "inserter=" entity, and the error codes MUST NOT conflict in - meaning. - - Here is an example of a Geolocation-Error header field: - - Geolocation-Error: 200; code="Retry Location Later"; - node="bob.example.com"; - inserter="alice.example.com"; + the Location Recipient determined was bad. The locationErrorValue + contains a 3-digit error code indicating what was wrong with the + location in the request. Each error code has a corresponding quoted + error text string that is human understandable. This text string is + OPTIONAL, but RECOMMENDED for human readability. The following table extends the values in Table 2&3 of RFC 3261 [RFC3261]. Header field where proxy INV ACK CAN BYE REG OPT PRA ---------------------------------------------------------------- Geolocation-Error r ar o - - o o o o + Header field where proxy SUB NOT UPD MSG REF INF PUB ---------------------------------------------------------------- Geolocation-Error r ar o o o o o o o Table 2: Summary of the Geolocation-Error Header Field The Geolocation-Error header field MAY be included in any response - to one of the above SIP requests, so long as Geolocation was in the - request part of the transaction. For example, Alice includes her - location in an INVITE to Bob. Bob can accept this INVITE, thus - creating a dialog, even though his UA determined the location - contained in the INVITE was bad. There is a Geolocation-Error - header value in the 200 OK to the INVITE informing Alice the INVITE - was accepted but the location provided was bad. The SIP requests - included in table 2 above are the ones allowed to optionally contain - the Geolocation header field (see section 4.1). That said, a UAC - MUST ignore a Geolocation-Error header field value that did not - contain its host-id.. - - Here is an example of a transaction that has a location error. In - this case, Bob responds with a 424 (Bad Location Information) - response, including a Geolocation-Error header field, is in Figure 3. - - Alice Bob - | | - | Request w/ Location | - |------------------------------------------------>| - | | - | | - | 424 (Bad Location Information) | - | with Geolocation-Error containing | - | 200 ("Retry Location Later with same data") | - |<------------------------------------------------| - | | + to one of the above SIP requests, so long as a Geolocation + locationValue was in the request part of the transaction. For + example, Alice includes her location in an INVITE to Bob. Bob can + accept this INVITE, thus creating a dialog, even though his UA + determined the location contained in the INVITE was bad. Bob merely + includes a Geolocation-Error header value in the 200 OK to the + INVITE informing Alice the INVITE was accepted but the location + provided was bad. The SIP requests included in table 2 above are the + ones allowed to optionally contain the Geolocation header field (see + section 4.1). - Figure 3. Basic Transaction with 424 and Geolocation-Error Header - Field + If, on the other hand, Bob cannot accept Alice's INVITE without a + suitable location, a 424 (Bad Location Information) is sent. This + message flow is shown in Figures 1, 2 or 3 in Section 3. The following subsections provide an initial list of location based errors for any SIP non-100 response, including the new 424 (Bad Location Information) response. These error codes are divided - into 5 categories, based on how the response receiver should react + into 4 categories, based on how the response receiver should react to these errors. - We start with a general purpose location error, meaning we are not - being specific about what is wrong with the location provided, but - it has been determined to be bad. - - o 1XX "Cannot Process Location" - - We next have an error that indicates there is probably nothing wrong - with the location information provided, but the receiver cannot - process it at this time. A Retry-After header value will indicate - how long to wait until sending location again to this Location - Recipient and expect it to be processed. - - o 2XX "Retry Location Later with same data" - - We next have an indication that something was wrong with the - location information supplied in the SIP request, and something on - the sender's side needs to be done to correct the bad information. - A Retry-After header value will indicate when to resend the location - information. - - o 3XX "Retry Location Later with updated device location" - - We next have a permission flag contained with this SIP request - indicating an LR need permission to reveal this information to a 3rd - party (retransmission-allowed flag) or permission to view the - contained location to properly process the SIP request - (routing-allowed flag). We will define two individual errors here to - facilitate informing the "inserter=" which flag needs to be adjusted - if they want this SIP request processed further by this SIP entity. - - o 4XX "Permission To Use Location Information" - - Finally, we create a general location denial error, for times when a - dereference was denied or timed-out. - - o 5XX "Location Information Denial" - - All 5 of the above error codes MUST be implemented to comply with - this specification. Each of these actionable errors is given a 3 - digit error code category, meaning any future 1XX, 2XX, 3XX, 4XX, - and 5XX error codes defined will have the same action expected by - X00 categories, although the future error code may provide more - granular information. If another action is expected to occur with a - newly defined error code, it MUST outside the 100-599 range. - -4.3.1 Location Error: 100 "Cannot Process Location" - - The location error 100 "Cannot Process Location" indicates to a - Geolocation-Error recipient that the locationValue supplied in a - request cannot be processed at this time. This only has to do with - the location that the location "inserter=" added to the request, and - not about the overall request that was sent. - - Action(s) to be taken by Geolocation-Error receiver for a 1XX: - This error gives no guidance on what to do next. It is a - general information indication to a SIP "inserter=" entity - that there was an unspecific problem with the location - supplied in the SIP request. - - Implementations MAY choose to react as if the "inserter=" - entity received a 2XX or 3XX location error. Implementations MUST - NOT react as if the "inserter=" entity received a 4XX location - error, as that error category involves human intervention to grant, - or not, permission to reveal "inserter=" location when this is - likely not desired. - - The text string of "Cannot Process Location" is RECOMMENDED, but not - mandatory for usage in this error. Implementations MAY use another - text string. - - An example 100 location error is: - - Geolocation-Error: 100; code="Cannot Process Location"; - node="bob.example.com"; - inserter="alice.example.com"; - - This category covers all 1XX location errors. The same basic - reaction is expected when a location "inserter=" entity receives any - 1XX location error. - -4.3.2 Location Error: 200 "Retry Location Later same data" - - The location error 200 "Retry Location Later same data" indicates - to a Geolocation-Error recipient that what they supplied in a - request, as far as location is concerned, cannot be processed at - this time, but there is no need to update the location at a later - time in a new SIP request. For example, this location error is - appropriate when the Location Recipient cannot process location at a - specific time, or when there is there was a timeout when a location - URI is dereferenced. - - Action(s) to be taken by Geolocation-Error receiver for a 2XX: - Reactions to a 2XX location error are to try again after some - period of time has elapsed. The "inserter=" has not identified - problems with the location provided in the original request, - so there is no need to update this location unless the - requestor moves. A Retry-After header field MUST be present in - the 424 response indicating after how long the LR thinks it - can process the location, the error recipient MUST obey this - instruction. A Retry-After header value of '0' indicates try - again immediately. - - Implementations SHOULD choose to react by queuing another message - with the same location information, unless the "inserter=" entity - knows it has changed locations. - - Implementations MAY inform the user of this error. The text string - of "Retry Location Later same data" is RECOMMENDED, but not - mandatory for this error. Implementations MAY use another text - string to inform the user that location was not received by the UA - (i.e., the called party). - - An example 200 location error is: - - Geolocation-Error: 200; code="Retry Location Later same data"; - node="bob.example.com"; - inserter="alice.example.com"; - - This category covers all 2XX location errors. The same basic - reaction is expected when a location "inserter=" entity receives any - 2XX location error. - - If a SIP request has the "routing-allowed" header field parameter - set to "no", and the SIP server believes processing location is - required in order to service the request properly, a 2XX location - error is sent towards the recipient. This error is the proper error - even when there is no location in the SIP request, but the SIP - request contains a policy statement that location is not to be - viewed during transit towards the ultimate destination. - -4.3.2.1 Location Error: 201 "Linkable Target Identity Required" - - The error code 201 "Linkable Target Identity Required" is - specifically for the event in which a SIP request requires a binding - of the Target's identity to the presence document in order to know - this is the Target's location to make an appropriate routing - decision. Because Alice could include Bob's location in her SIP - request, the SIP server - in this specific case - needs to - understand this message is routed based on Alice's location, and not - Bob's. There is no absolute binding between presence documents and - SIP signaling, hence a separate error with specific behaviors are - necessary. - - It is of particular importance is the emergency calling case, - described here [ID-PHONE]. The presence document has a - element containing an "entity=" attribute identifying who the - presence document is about. The PIDF-LO is a presence document. - [RFC3693] allows unlinkable pseudonyms to be in the "entity=" - attribute. This is problematic for some (all?) source location based - call routing situations. - - The "node=" routing intermediary makes this locationErrorValue a 201 - to resolve this problem. In the 424 response, the Retry-After header - value of '0' is REQUIRED, indicating the new request be sent - immediately, but with a Target identification resolved in the - PIDF-LO and SIP request. In presence, the "entity=" attribute is - typically the URI of the presentity, meaning something like the - Contact address of the UAC here. - - If there is no Retry-After header value, the default is to resend - the SIP request immediately with the corrected "entity=" attribute - (i.e., emulating a Retry-After: 0 header value). - - Action(s) to be taken by Geolocation-Error receiver for a 201: - - 201 location error indicate the "inserter=" did not properly - identify the Target of this presence document. The - Retry-After has been received - or is assumed to be 0 - - meaning the new SIP request is to be sent immediately. - -4.3.3 Location Error: 300 "Retry Location Later with device updated - location" - - The location error 300 "Retry Location Later with device updated - location" indicates to a Geolocation-Error recipient that what they - supplied in a request, as far as location is concerned, cannot be - processed. In order to retry this request in a new SIP request, the - location information must be updated. - - Action(s) to be taken by Geolocation-Error receiver for a 3XX: - - 3XX location errors indicate the "inserter=" SIP entity needs - to refresh its location, or make the location information - supplied more complete, without notifying the user of this - error. 3XX errors may be resolved without user intervention. - - This document gives no guidance how this is accomplished, given the - number of ways a UAC can learn its location, or a SIP intermediary - can determine this UAC's location (with or without the help of a - Location Server. - - This 300 location error currently does not indicate what exactly was - wrong with the location supplied, according to the Location - Recipient. That is left for a future effort. - - Implementations MAY choose whether or not to inform the user of this - error. The text string of "Retry Location Later with device updated - location" is RECOMMENDED, but not mandatory for usage in this - error. Implementation MAY use another text string to inform the - user that location was not received by the UA (i.e., the called - party). - - A 3XX location error would be used where the Location Recipient - cannot find or cannot parse the location supplied. 3XX location - errors should cause a requestor to retry with refreshed location - information, which might be sufficient to fix the problem. Also, a - 3XX location error would be used when a Location Recipient was - expecting to find location in a SIP request, but did not find it - - perhaps an emergency request was made that did not contain location. - The retry in this case would be in the form of an UPDATE Method - request, containing location. If the 424 response contains a - Retry-After value, there SHOULD NOT be a long delay associated with - a new request - under the guise that if the location had been good, - there would not have been an error to this request. - - An example 300 location error is: - - Geolocation-Error: 300; code="Retry Location Later with device - updated location"; - node="bob.example.com"; - inserter="alice.example.com"; - - This category covers all 3XX location errors. The same basic - reaction is expected when a location "inserter=" entity receives any - 3XX location error. - -4.3.4 Location Error: 400 "Permission To Use Location Information" - - The location error 400 "Permission To Use Location Information" - indicates to a Geolocation-Error recipient that they sent a - particular SIP Request including location in that request, without - giving permission in the request for an intermediary SIP entity to - look at that location information (i.e., the - was set to "no" in the PIDF-LO for B2BUAs, - or "routing-allowed=no" as a Geolocation header field parameter for - proxy servers) to route the request toward the intended recipient - (i.e., the called party). + o 1XX errors mean the LR cannot process the location within the + request. - All 4XX level location errors are asking for permission from the - "inserter=" to set a flag differently in order to accomplish - something with the location. + o 2XX errors mean the LR wants the LS to send new or updated + location information, perhaps with a delay associated with when + to send the request. - An example 400 location error is: + o 3XX errors mean some specific permission is necessary to process + the included location information. - Geolocation-Error: 400; code="Permission To Use Location - Information"; - node="bob.example.com"; - inserter="alice.example.com"; + o 4XX errors mean there was trouble dereferencing the Location URI + sent. - Because there are two completely separate flags known at this time, - one in the PIDF-LO (retransmission-allowed) and one as a Geolocation - header parameter (routing-allowed), two separate Locations Errors - are created to give the "inserter=" entity the specific choice to - reset the right flag. + All 4 of these error groups have a top level error code with the + meaning as stated above (i.e., a Location Error: 100 is "Cannot + Process Location", etc). There are two exceptions necessary to + include in this document, both have to do with permissions necessary + to process the SIP request; they are -4.3.4.1 Location Error: 401 "Permission To Retransmit Location + Location Error: 301 "Permission To Retransmit Location Information to a Third Party" - This location error is specific to having the PIDF-LO - element set to "=no". This location error - is asking for permission of the "inserter=" entity to resend the SIP - request with a PIDF-LO element set to - "=yes". - - Action(s) to be taken by Geolocation-Error receiver for a 401: - - The 401 location error indicates to the location "inserter=" - that the LR (i.e., a UA or SIP intermediary server) needs to - have permission to transmit the supplied location information - to a third party. This indication MUST require human user - intervention, acting as the Ruleholder of the policy on - whether or not location is to be revealed. - - The user of the location "inserter=" device can choose to grant - permission to the LR to allow this request to be sent on to another - entity, or the user can deny permission. It is the user's choice as - Ruleholder. - - Implementations MUST provide the user, as Ruleholder, a clear - indication that permission to consume their location is sought by an - entity that is not the entity that the user is calling. The text - string of " Permission To Retransmit Location Information to a Third - Party " is RECOMMENDED, but not mandatory for this error. - Implementations MAY use another text string to inform the user that - location is being sought by an LR. - - This document gives no guidance how the UA can seek permission from - the user, given the number of ways a UA can accomplish this (i.e., - audio prompt or toggle or keystroke on the UA). - - An example 401 location error is: - - Geolocation-Error: 401; code="Permission To Retransmit Location - Information to a Third Party"; - node="bob.example.com"; - inserter="alice.example.com"; + This location error is specific to having the Presence Information + Data Format (PIDF-LO) [RFC4119] element set + to "=no". This location error is stating it requires permission + (i.e., PIDF-LO element set to "=yes") to + process this SIP request further. If the LS sending the location + information does not want to give this permission, it will not reset + this permission in a new request. If the LS wants this message + processed without this permission reset, it MUST choose another + logical path (if one exists). -4.3.4.2 Location Error: 402 "Permission to Route based on Location + Location Error: 302 "Permission to Route based on Location Information" This location error is specific to having the locationValue header parameter set to "=no". This location error is - asking for permission of the "inserter=" entity to resend the SIP - request with a locationValue header parameter set - to "=yes". - - Action(s) to be taken by Geolocation-Error receiver for a 402: - - The 402 location error indicates to the location "inserter=" - that the LR (i.e., SIP intermediary server) needs to have - permission in to look at and use the supplied location to - complete the message routing. This indication MUST require - human user intervention, acting as the Ruleholder of the - policy on whether or not location is to be revealed. - - The user of the location "inserter=" can choose to grant permission - to this SIP intermediary server to allow this request to be routed, - or the user can deny permission. It is the user's choice as - Ruleholder. - - Implementations MUST provide the user, as Ruleholder, a clear - indication that permission to consume their location is sought by an - entity that is not the entity that the user is calling. The text - string of "Permission to Route based on Location Information" is - RECOMMENDED, but not mandatory for usage in this error. - Implementations MAY use another text string to inform the user that - location is being sought by an intermediary (i.e., not the called - party). - - This document gives no guidance how the UA can seek permission from - the user, given the number of ways a UA can accomplish this (i.e., - audio prompt or toggle or keystroke on the UA). - - This 402 location error indicates which specific SIP server needs - the location by the "node=" FQDN address supplied, perhaps telling - the user (via audio or video indication) which SIP entity wants its - location learned for routing purposes. Perhaps the user can know in - some circumstances whether this is an appropriate "node=" (domain). - This latter feature is not described in this document (just - mentioned here as a possibility). - - An example 402 location error is: - - Geolocation-Error: 402; code="Permission to Route based on - Location Information"; - node="bob.example.com"; - inserter="alice.example.com"; - -4.3.5 Location Error: 500 "Location Information Denial" - - The location error 500 "Location Information Denial" indicates to a - Geolocation-Error recipient that what they supplied in a request, as - far as location is concerned, has been denied at this time. - This only has to do with the location that the location "inserter=" - added to the request, and not about the overall request that was - sent. If this were applied to the SIP request itself, this would - equate to a 6XX Global error. - - Action(s) to be taken by Geolocation-Error receiver for a 5XX: - This error gives no guidance on what to do next, other than to - not try again with this same location supplied. - - If the Location Recipient determined that merely refreshing, or in - some other way alter or augment the location supplied would work in - a new request, then a 3XX location error would have been more - appropriate. An example of why this 5XX could have been returned is - if location were sent as a location URI, and the LS denied the - dereference request from the potential Location Recipient, this is - the expected location error returned to the "inserter=" entity. In - all likelihood, this is a dereference function error, meaning this - will not occur when location is carried by-value in the request. - - Implementations MUST NOT make any assumptions about the implications - of this location error other than recognizing that a location based - denial error has occurred. This does not mean the SIP request was - denied, or even had an error, unless the response was a 424. - Otherwise, this only has to do with the location part of the - request. - - The difference between a 1XX and a 5XX location error is simple. A - 1XX location error is appropriate when a Location Recipient either - does not know or cannot tell the "inserter=" entity what was wrong - with the location supplied in a SIP request. A 5XX location error - is appropriate when the Location Recipient was purposely and - actively prevented from retrieving the location information. This - could occur in a UA or SIP server. - - If implementations choose to inform the UA user of this error, the - text string of "Location Information Denial" is RECOMMENDED, but not - mandatory for usage in this error. Implementations MAY use another - text string. - - An example of this location error is here: - - Geolocation-Error: 500; code="Location Information Denial"; - node="bob.example.com"; - inserter="alice.example.com"; - - This category covers 5XX location errors. The same basic reaction - is expected when a location "inserter=" entity receives any 5XX - location error. - -4.3.6 Which Scenario Matches Which Error Code? + stating it requires permission (i.e., a set to + "=yes") to process this SIP request further. If the LS sending the + location information does not want to give this permission, it will + not reset this permission in a new request. If the LS wants this + message processed without this permission reset, it MUST choose + another logical path (if one exists). - The following scenario/error code mapping MUST be used for - consistency, +4.4 The 'geolocation' Option Tag - - Scheme (sip:, or sips:, or pres:, etc.) of the location URI - is not supported - (100) - - Format (geo or civic) is not supported - (100) - - Found where location information should be in the request, but do - not understand what is at that part of the request -(300) - - Cannot find LS in location URI (no access or no path) - (100) or - denied access - (500)) + This document creates and registers with the IANA one new option + tag: "geolocation". This option tag is to be used, as defined in + [RFC3261], in the Require, Supported and Unsupported header fields. - - Dereference failed (timeout) - (200) - - Insufficient location info supplied - (300) +4.5 Location URIs in Message Bodies -4.4 The 'geolocation' Option Tag + In the case where a location recipient sends a 424 response and + wishes to communicate suitable location by reference rather than by + value, the 424 MUST include a content-indirection body per RFC 4483. - This document creates and IANA registers one new option tag: - "geolocation". This option tag is to be used, as defined in - [RFC3261], in the Require, Supported and Unsupported header fields. +4.6 Location URIs Allowed -4.5 Using sip/sips/pres as a Dereference Scheme + The following is part of the discussion started in Section 3, Figure + 2, which initiated the concept of sending location indirectly. If a location URI is included in a SIP request, it MUST be a SIP-, SIPS- or PRES-URI. When PRES: is used, as defined in [RFC3856], if the resulting resolution resolves to a SIP: or SIPS: URI, this - section applies. - - This document IANA registers 3 mandatory-to-implement URI schemes - for a location URI: - - o SIP: - o SIPS: - o PRES: - - These 3 are registered with IANA in Section 9.6. - - These schemes MUST be implemented according to this document. + section applies. These schemes MUST be implemented according to + this document. absoluteURI is not mandatory-to-implement, but allowed. - Dereferencing a Target's location using SIP- or SIPS-URI is - accomplished by treating the URI as a PRES-URI and generating a - SUBSCRIBE request to a presence server as defined in [RFC3856] - using the 'presence' event package. The resulting NOTIFY MUST - contain a PIDF-LO. See Figure 4 for a basic message flow for a - dereference. The NOTIFY contains Alice's PIDF-LO in Figure 4. - - When used in this manner, SIP is a Using Protocol as defined in - [RFC3693] and elements receiving location MUST honor the - 'usage-element' rules as defined in this specification. - - Alice Location Server Bob - | | - | INVITE w/ Location URI | - |-------------------------------------------------------->| - | | | - | | SUBSCRIBE to location URI | - | |<-----------------------------| - | | 200 (OK) | - | |----------------------------->| - | | | - | | NOTIFY w/ PIDF-LO | - | |----------------------------->| - | | 200 (OK) | - | |<-----------------------------| - | | | - | 200 (OK) | - |<--------------------------------------------------------| - | | | - - Figure 4. Location-by-Reference and Dereferencing - - In Figure 4, Alice sends Bob her location as a location URI. Bob - receives this location URI in the INVITE and generates a new - transaction (SUBSCRIBE) to retrieve Alice's PIDF-LO. If accepted, - the PIDF-LO will be returned in the NOTIFY request from the Location - Server to Bob's UA. This is the first instance between Alice and - Bob that Alice's location is in any message. - - The SUBSCRIBE contains a geolocation option tag in either the - Supported or Require header field (depending on what strength of - support the UA requires). The NOTIFY MUST match the subscribing - UA's option-tag strength for geolocation. - - A dereference of a location URI using SUBSCRIBE is not violating a - PIDF-LO 'retransmission-allowed' element value set to 'no', as the - NOTIFY is the only message in this multi-message set of transactions - that contains the Target's location, with the location recipient - being the only SIP element to receive this PIDF-LO. This is the - purpose of this extension to SIP - to convey location to a specific - destination. - - Certain nuances about this subscription exist that will not be - covered in this document. Instead these additional functions will be - described in the following document: [ID-GEO-FILTERS]. Here we - introduce the general concept; the "Filters" document has the - details. These two are consistent with each other. - -5. Geolocation Examples - - This section contains are two examples of messages providing - location. One shows LbyV with coordinates, the other shows - dereferencable location URI. The example for (Coordinate format) is - taken from [RFC3825]. A Civic-format example of the same position on - the earth as is in the coordinate format example is in appendix B, - which is taken from [RFC4776]. The differences between the two - formats appear within the in the examples. Other - than this portion of each PIDF-LO, the rest is the same for both - location formats. + See [ID-GEO-FILTERS] for more details on dereferencing location. - The key to the provided samples is in the Geolocation header field, - which has a different type of URI, based on the different means of - location conveyance. Section 5.1 shows a "cid:" URI, indicating - this SIP request contains an LbyV message body - which is in the - form of a PIDF-LO. Section 5.2 shows an location URI indicating - location is to be acquired via an indirection dereference mechanism, - which is determined by the scheme of URI supplied. +5. Geolocation Example -5.1 Location-by-value (Coordinate Format) +5.1 Location-by-value (in Coordinate Format) This example shows an INVITE message with a coordinate location. In this example, the SIP request uses a sips-URI [RFC3261], meaning this message is protected using TLS on a hop-by-hop basis. INVITE sips:bob@biloxi.example.com SIP/2.0 Via: SIPS/2.0/TLS pc33.atlanta.example.com;branch=z9hG4bK74bf9 Max-Forwards: 70 To: Bob From: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com Geolocation: - ;inserted-by="alice@atlanta.example.com" - ,routing-allowed=no + ;routing-allowed=no Supported: geolocation Accept: application/sdp, application/pidf+xml CSeq: 31862 INVITE Contact: Content-Type: multipart/mixed; boundary=boundary1 Content-Length: ... --boundary1 Content-Type: application/sdp @@ -1311,838 +648,156 @@ Content-Type: application/pidf+xml Content-ID: - + - 33.001111 -96.68142 + 32.86726 -97.16054 no - 2010-02-12T06:00:00Z2010-07-30T20:00:00Z 802.11 - - 2010-02-12T04:00:00Z + mac:1234567890ab + 2010-07-28T20:57:29Z + --boundary1-- The Geolocation header field from the above INVITE: Geolocation: ... indicates the content-ID location [RFC2392] within the multipart - message body of where location information is, with SDP being the - other message body part. The "cid:" eases message body parsing. + message body of where location information is. An assumption can be + made that SDP is the other message body part. The "cid:" eases + message body parsing by disambiguating the MIME body that contains + the location information associated with this request. If the Geolocation header field did not contain a "cid:" scheme, for - example, like this location URI: + example, it could look like this location URI: - Geolocation: + Geolocation: ... the existence of a non-"cid:" scheme indicates this is a location URI, to be dereferenced to learn the Target's location. Any node wanting to know where user "target123" is would subscribe to - server5 to dereference the sips-URI (see Figure 4 for this message - flow, and Section 5.2 for this decoded example). The returning - NOTIFY would contain Alice's location in a PIDF-LO, as if it were - included in a message body (part) of the original INVITE. + that user at server5 to dereference the sips-URI (see Figure 3 in + section 3 for this message flow). -5.2 Location-by-reference +5.2 Two Locations Composed in Same Location Object Example - Below is an INVITE request with a location URI that is not a "cid:" - - instead of an LbyV PIDF-LO message body part as shown in Section - 5.1. The Location Recipient will dereference Alice's location at - the Atlanta Location Server the location URI is pointing towards. - Dereferencing, if done using SIP, is accomplished by the Location - Recipient sending a SUBSCRIBE request to the URI reference for - Alice's location. The received NOTIFY is the first SIP request - containing Alice's UA location, as a PIDF-LO message body (see - Figure 4 for this message flow example). The NOTIFY, in this case, - and not the INVITE, is the SIP request that is conveying location. - There is no retransmission of location in this usage. + This example shows the INVITE message after a SIP intermediary + rejected the original INVITE (say, the one in section 5.1). This + INVITE contains the composed LO sent by the SIP intermediary which + includes where the intermediary understands Alice to be. The rules + of RFC 5491 [RFC5491] are followed in this construction. + + This example is here, but should not be taken as occurring very + often. In fact, this is believed to be a corner case of location + conveyance applicability. INVITE sips:bob@biloxi.example.com SIP/2.0 - Via: SIP/2.0/TLS pc33.atlanta.example.com - ;branch=z9hG4bK74bf9 + Via: SIPS/2.0/TLS pc33.atlanta.example.com;branch=z9hG4bK74bf0 Max-Forwards: 70 To: Bob From: Alice ;tag=9fxced76sl - Call-ID: 3848276298220188511@atlanta.example.com - Geolocation: - ;inserted-by="bigbox3.atlanta.example.com" - ,routing-allowed=no + Call-ID: 3848276298220188512@atlanta.example.com + Geolocation: + ;routing-allowed=no Supported: geolocation Accept: application/sdp, application/pidf+xml - CSeq: 31862 INVITE - Contact: - - (...SDP goes here as the only message body) - - A Location Recipient would need to dereference the sips-URI in the - Geolocation header field to retrieve Alice's location. If the - atlanta.example.com domain chooses to implement location conveyance - and delivery in this fashion, it is RECOMMENDED that entities - outside this domain be able to reach the dereference server, unless - location is intentionally restricted within the atlanta.example.com - domain. - -6. SIP Element Behavior - - Because a device's location is generally considered to be sensitive - in nature, location information needs to be protected when - transmitted. This can be addressed through securing the location - information to prevent either viewing or changing the PIDF-LO. - - Section 26 of [RFC3261] defines the SIPS security functionality by - transporting SIP messages with either TLS protection between SIP - entities. - - If a SIP entity wants to prevent all SIP entities in a request path - that do not possess a decryption key from viewing or changing the - contents of the PIDF-LO, the message body needs to be secure by a - means such as S/MIME. - -6.1 UAC Behavior - - A UAC might choose to send location in a SIP request to facilitate - location-based routing of the request, or for some other purpose. - Alice communicating her location to Bob in a SIP request is a simple - example of this. If Alice wanted to include her location as a - message body in an INVITE that also has an SDP message body, the - Content-Type: Multipart MUST be supported by both UAC and UAS. - Multipart comes in many forms (/mixed, /alternative, etc), and this - document does not limit which type of multipart is used, though - future documents might specify or limit multipart to a subset of - all the choices for a given use. - - A UAC conveying location MUST include a locationValue in a - Geolocation header (see section 4.1) with either an LbyV indication - (a cid-URL), or a dereferencable location URI. Requests containing - an LbyV message body sent MUST also contain a Geolocation header - field. The UAC supporting this extension MUST include a Supported - header with the 'geolocation' option tag. - - More than one location format (civic and coordinate) can be included - in the same message body part, but all location parts of the same - PIDF-LO MUST point at the same position on the earth, identifying - the same Target. The same location in multiple formats, for - example, a partial or complete geodetic and a partial or complete - civic, allows the recipient to select the most preferred format for - its use. Additional complementary location information can be in - the second format as well. - - Multiple PIDF-LOs are allowed in the same request, with each allowed - to point at separate positions - however, each PIDF-LO MUST identify - a different Target (i.e., in the "entity=" attribute in the - element of the presence document). Therefore, there will - be no confusion by a Location Recipient receiving more than one - PIDF-LO (in a message body or when dereferenced, or a combination). - A SIP request SHOULD include only one location per Target in a - single SIP request. More than one will likely lead to confusion by - a Location Recipient because this extension does not provide - guidance on what a recipient is to do with more than one location - for the same Target (which could point to different positions), nor - does it give any preference regarding which location is more or less - reliable than another location in the same request. - - The presence of the 'geolocation' option tag in a Supported header - field without a Geolocation header field in the same message informs - a SIP element receiving this request that the UAC understands this - extension, but it does not know or wish to convey its location at - this time. Certain scenarios exist (location-based retargeting) in - which location is required in a SIP request in order to retarget the - message properly. Indicating support with a geolocation option tag - affects how a UAS or SIP server processes such a request. For - example, it ought to understand that erroring the request because - there was no location in the request is likely not going to result - in the location appearing in the subsequent request. - - The 'geolocation' option tag SHOULD NOT be used in the Proxy-Require - header field, because often the UAC will not know the underlying - topology to know which proxy will do the retargeting, thus - increasing the likelihood of a request failure at the first hop - proxy that does not understand this extension, as is required by - inclusion of the option tag in this header field. - - A UAC inserting a locationValue MUST include an "inserted-by=" - parameter to indicate its hostport. This is copied to the - "inserter=" parameter of the Geolocation-Error header field in a - response if a Location Recipient determines there is something wrong - with the locationValue in this request. Because more than one - locationValue can be inserted along the path of the request, this - indication is necessary to show which locationValue had the problem - in the response, and who the locationErrorValue is for. For - example: - - Geolocation: ; - inserted-by="alice@atlanta.example.com" - - If a UAC does not learn and store its location locally (a GPS chip) - or from the network (DHCP or LLDP-MED), the UAC MAY learn its - location URI (from DHCP for example). If the latter is the case, - the UAC can SUBSCRIBE to this location URI, using the 'presence' - event package, to get and store its own location. - - The Location Server will likely challenge requests to dereference a - Target's location URI. The location URI SHOULD be treated as - equivalent to possession of the location information itself and thus - TLS SHOULD be used when transmitting any location URI hop-by-hop - along the path to the Location Recipient, for protection reasons. - This is not to be confused with a 'possession model', in which - possessing the location URI grants authorization to dereference the - URI. Any entity dereferencing the location URI MUST pass whatever - authentication and authorization rules are on the LS to acquire this - location. The Ruleholder from [RFC3693] is still very much in - control - for any entity possessing the location URI. - - If the Location Generator wishes to control whether any location - included in the SIP request or added along the signaling path of - this request can be viewed for routing decisions, the Location - Generator adds a Geolocation header field value including the - "routing-allowed=no" parameter. This header field parameter - provides specific policy rules for each locationValue (if more than - one locationValue is inserted along the signaling path) within the - SIP request. A UAC SHOULD include the "routing-allowed" header - field parameter, with or without a locationValue, to each SIP - request supporting this specification to ensure the UAC's policy for - intermediaries which might add a locationValue of the Target - downstream. The default behavior for SIP servers is to consider - this value to be present, with a value of "=no". A "=no" value in - this parameter indicates there can be no routing decisions derived - from the UAC's location. UACs MUST be prepared to receive an error - indicating a SIP intermediary needs to have this parameter set - to"=yes" in order to properly routing this message. The UAC can - make a local policy choice as to whether it wishes to set the - parameter to "=yes", thus allowing each SIP entity along the message - path to use the UAC's location when making routing decisions. There - is no way to indicate that only a subset of SIP intermediaries have - permission, while other intermediaries do not. - - There is no feedback mechanism to inform the Target if a SIP server - has included a locationValue downstream. If a UAC has already - conveyed location in the original request of a transaction, and - wants to update its location information (for whatever reason) after - the original request is sent, or after a dialog is created, this is - done by sending an UPDATE request [RFC3311]. The UPDATE will include - a geolocation option tag and Geolocation header field with the new - locationValue to the original destination UAS. - - A presence document includes identity information (in the "entity=" - attribute of the element), although the identity could be - an unlinkable pseudonym [RFC3693]. Implementations of this - extension SHOULD consider the appropriateness of including an - unlinkable pseudonym as the identity in the location information - where a real identity is not required. See the concerns raised in - section 4.3.2 about unlinkable pseudonyms in relation to their - potential problems with requests that need to route based on the - location contained in the message. - - A location URI MUST NOT contain any user identifying information. - For example, it is much more secure to use something unidentifiable - like - - 3fg5T5yqWowhGLn54wg4NgHlkDsFn@example.atlanta.com - - rather than something identifiable like - - aliceishere@example.atlanta.com. - - Use of self-signed certificates is inappropriate for use in - protecting a PIDF, as the sender does not have a secure identity of - the recipient. - - Although this is discussed in more detail in later in section 6.2, - SIP entities MUST NOT bypass rules and behaviors conveyed in a - PIDF-LO. UACs SHOULD take care when setting their - flag to "yes". When Alice tells Bob her - location with this flag set to "yes", Bob is free to tell Carol - where Alice is (as long as the time has not - elapsed, indicating that the location information should have - already been deleted, according to RFC 4119). This is an implicit - byproduct of the PIDF-LO rule-set, as of this writing. This decision - is a configuration issue, but is worth mentioning here. - -6.1.1 UAC Receiving a Location Failure Indication - - Location Recipients that use the location information for - location-based routing decisions can be either destination UAs or - intermediate servers. If a request fails based on the location - information in the request, a 424 (Bad Location Information) - response is sent back to the UAC. The 424 MUST have a - Geolocation-Error header field containing one or more - locationErrorValues in the response message. A locationErrorValue - has a header field parameter indicating which entity inserted the - locationValue correlated to this error, called the "inserter=" - parameter. This "inserter=" parameter (in the locationErrorValue) - is copied from the "inserted-by=" parameter (from the locationValue) - by the Location Recipient (UA or proxy) sending the error response. - A UAC receiving a Geolocation-Error in any response type MUST check - whether the "inserter=" parameter in the locationErrorValue - indicates this UAC. - - o If locationErrorValue does not match, the locationErrorValue - MUST be ignored. - - o If a locationErrorValue is in a 424, and the "inserter=" entity - is not this UAC, the response SHOULD be treated as a 400 - response. - - o If locationErrorValue does indicate this UAC, this UAC MUST - process the response, including the Geolocation-Error code - (defined in section 4.3), taking the action described in that - section for the received error code. - - Additionally, the UAC MUST ignore a Geolocation-Error header field - value, even for this UAC, even in a 424 response if the UAC did not - include a Geolocation header field value (with locationValue) in the - request part of the transaction. - - A UAC MAY reattempt a new request if it can correct the stated - failure in the Geolocation-Error header field, unless the location - error is a 5XX level error - Section 4.3 clearly states not to do - this. A UAC MUST follow all the guidance that pertains to UACs from - Section 4.3 (Geolocation-Error Header Field), heeding what to do - when it receives any of the error codes articulated in that section. - - Any UAC that inserted location into a request MUST be prepared to - receive the Geolocation-Error header field in any response, looking - to determine if a locationErrorValue is meant for the UAC, and to - react accordingly. - - If a UAC includes location in a request, and either the UAS does not - determine errored location was critical to the transaction and - accept the request, or the request failed for reason other than - location, any response MAY contain a Geolocation-Error header field - containing a locationErrorValue with the details of the location - error. - -6.2 UAS Behavior - - If the Geolocation header field is present in a received SIP - request, the type of URI contained in the locationValue will - indicate if location is in a message body (part) or requires an - additional dereference transaction. If the location URI is sip:, - sips: or pres:, and the UAS wants to learn the UAC's location, the - UAS MUST SUBSCRIBE to the provided URI to retrieve the PIDF-LO being - conveyed by the UAC as defined in [RFC3856]. If successful, the - Target's PIDF-LO will be returned in the NOTIFY request from the - remote host. The UAS is not REQUIRED to dereference the location - URI if location is not needed to process the request. It is - RECOMMENDED the UAS display the location to the user, or otherwise - render the location appropriately. - - A Require header field with the 'geolocation' option tag indicates - the UAC requires that the UAS understand this extension, sending an - error response if it does not. A 420 (Bad Extension) with a - 'geolocation' option tag in an Unsupported header field would be the - appropriate response in this case. - - It is possible, but undesirable, for a message to arrive with a body - containing an LbyV, but with no Geolocation header field value - pointing to it (potentially no Geolocation header field at all). In - this case, the recipient MAY still read and use the message body. - Unless stated otherwise by future standards-track publication(s), a - location URI only has meaning within the Geolocation header field - and MUST NOT appear in any other SIP header field. - - There are 3 Geolocation header field parameters, - - o "inserted-by=" - o "used-for-routing" - o "routing-allowed" - - The "inserted-by=" and "used-for-routing" parameters are contained - within a locationValue, whereas the "routing-allowed" parameter is - outside any locationValue, and is to appear at most once in the SIP - request. - - The "inserted-by=" parameter informs a Location Recipient which SIP - entity added this locationValue to the SIP request. This parameter - is mandatory for each locationValue in the request. The value in - the "inserted-by=" parameter is copied into the "inserter=" - parameter in each locationErrorValue if there is an error in the - location to be reported back to the location sender. See section - 6.2.1. - - The "used-for-routing" parameter is included in the locationValue if - a SIP server used the location in the request to determine how to - route or forward the message towards the ultimate destination. If - there are more than one locationValues in the Geolocation header - field, it is possible that different locationValues were used to - route the message at different points along the path traversed by - the request. This is allowed, as it is consistent with the rule - that whenever a message is routed based upon a locationValue, a - "used-for-routing" parameter is added to the applicable - locationValue. This parameter MUST be present in each locationValue - used along the path. A "used-for-routing" parameter MUST NOT be - removed from a locationValue in a request. - - The "routing-allowed" parameter is exclusively for SIP servers, and - will be discussed in section 6.3. - - Additional locationValues inserted into a request MUST be placed - the order they were generated, and not rearranged. This informs a - Location Recipient which was the last locationValue in the message - that was used to route the message. This is for troubleshooting and - management reasons. - - Individual header field parameters in any received locationValue - MUST NOT be modified or deleted in transit to the ultimate - destination. - - A UAS MUST NOT send location in a response message, as there can be - any number of issues/problems with receiving location, and the UAC - or proxy server(s) cannot reply to a response with an error - response. If the UAS wants to send its location to a UAC, it can do - so in a new request within a separate transaction. This document - gives no recommendation about which SIP request to use, but SIP - MESSAGE is a viable choice. - - A UAS MAY include a 'geolocation' option tag in the Supported header - field of a response, indicating it does understand this extension, - even if location was not included in a request to the UAS. - - A UAS wishing to dereference a location URI contained in a received - request will use the 'presence' event package in a SUBSCRIBE request - to the URI. If accepted, the LS will return the PIDF-LO to the UAS - in one or more NOTIFY requests - depending on the duration of the - subscription. If there are any errors during dereferencing, - or in the PIDF-LO itself, the UAS will respond to the original - request with a locationErrorValue indicating what the UAS concluded - was wrong with the location. This is to include any dereferencing - problems encountered. - - Dereferencing for sip:, sips: and pres: URI schemes are - mandatory-to-implement. - - A UAS MUST be prepared to receive subsequent location updates from - upstream entities (regardless of how the UAS received location - previously from this UAC). The UAC will convey updated location - using the UPDATE [RFC3311] method to the UAS, and not a reINVITE. - The UAS MUST NOT reject updated location arriving in a reINVITE - though, as other dialog parameters might be changing also (in which - a reINVITE is appropriate). - - If there is more than one location (any combination of PIDF-LOs or - location URIs), this document does not give guidance as to what a - Location Recipient does with each location. There are no priority - or 'more-trusted' indications specified by this document. All this - is considered application-specific, and out-of-scope for this - document. If more than one location is present in the PIDF-LO, - location elements in the same PIDF-LO MUST apply to the same Target - (identified in the "entity=" attribute) and MUST point at the same - position on the earth. If there is more than one PIDF-LO with - different Target identifiers, then the UAC is merely telling the UAS - where more than one Target is, and there SHOULD NOT be any conflict. - - Within any PIDF-LO, there is a policy - element that can be set to "yes" or "no". These are the only - possibilities. If Alice conveys her location to Bob (as has been - described throughout this document) with a - element set to "no", then Bob MUST NOT inform any other element - where Alice is. If the element is set to - "yes", then Bob can inform other elements where Alice is, but only - as long as the policy element, also in the - PIDF-LO, allows [RFC4119]. As a byproduct of this, that means that - if Alice conveys her location to Bob with a - element set to "yes", and the time does not - require Bob to delete Alice's location yet, then Bob is free to tell - anyone else where Alice is. The "entity=" attribute in the - element identifies who is the Target of each location, - preventing confusion. Whenever Bob conveys Alice's location, - timer MUST be maintained as is (i.e., not changed - from when Bob received it). RFC 4119 implicitly allows this - behavior, and the behavior does not change when SIP is the Using - Protocol. - -6.2.1 UAS Generating a Location Failure Indication - - If a UAS receives location in a request, but determines there is a - problem with the location in the request, it is the responsibility - of the UAS to inform the entity that inserted the problematic - location into that request. The Geolocation header field in the - request has a locationValue, providing the UAS a location URI - indicating where the Target's location is. The Location Target - identified in the PIDF-LO may or may not be the location inserter, - or the generator of the request. Ultimately, location is in a - PIDF-LO. This is either in the request as a message body (LbyV), or - obtained by initiating a dereference transaction on a Location - Server identified in the location URI. Location Servers typically - challenge all dereference requests. All PIDF-LOs have a Location - Target identifier. The "inserted-by=" parameter of the - locationValue tells the UAS which SIP entity inserted that - locationValue. This "inserted-by=" parameter is copied into the - "inserter=" parameter of the locationErrorValue generated by the - Location Recipient (the UAS), in a response, when it wants to inform - the location "inserter=" entity there was a problem with the - location it received. - - There can be more than one locationValue in a request. The - "inserter=" parameter in the locationErrorValue will prevent - entities that did not insert the errored location from - misunderstanding whether the locationErrorValue applies to them. - - If there is one valid locationValue in a request, even if all the - others have errors associated with them, the Location Recipient MUST - NOT send a 424 (Bad Location Information) response. The Location - Recipient (the UAS) MUST send a locationErrorValue for each errored - locationValue, with unique "inserter=" parameters to make sure the - right entities know which locations were in error. - - As hinted at, a location "inserter=" can be a UAC or it can be an - in-signaling-path SIP server acting as a UAC locator. This - means the SIP server is including its version of where it thinks the - UAC is, geographically. This "inserter=" has to be in the form of - an dereferencable location URI in a locationValue, because SIP - servers are not allowed to insert message bodies. - - Each locationErrorValue has an error code, letting the location - "inserter=" entity know what was wrong with the location supplied by - that entity. See Section 4.3 for the 5 actionable responses a UAC - can take from a locationErrorValue. - - If the location "inserted-by=" entity, meaning either the UAC or - proxy in the message path chose to indicate that location was - sufficiently important to include a 'geolocation' option tag in a - Require header field, any error response SHOULD be a 424 (Bad - Location Information) back to the "inserter=" entity (knowing the - response will ultimately go to the UAC regardless) if there needs to - be a good locationValue sent to properly process the request. Only - entities identified in a locationErrorValue as the "inserter=" - entity will pay attention to this locationErrorValue. All other - entities MUST ignore any locationErrorValue not directed towards - them. See section 4.3 for more information on this, including all - the location-specific errors and Geolocation-Error header field - parameters. - - In the above scenario ('geolocation' option tag in a Require - header field), the only other response can be a 420, if the UAS - does not support this Geolocation extension to SIP. - - If the "inserted-by=" location entity placed the 'geolocation' - option tag in a Supported header field, the response can be a 424 if - it chooses, but also can be any other SIP response, including a 200 - OK. A locationErrorValue in a Geolocation-Error header field that - is not in a 424 (Bad Location Information) response is considered - informational by the Location Recipient, and does not cause the - Location Recipient to reject the request solely because of bad - location information. - - For example, Alice INVITEs Bob to a dialog, and includes geolocation - in the request. Bob can accept the INVITE with a 200 OK and still - add a locationErrorValue in the 200 OK indicating "yes, I accept - your request, and btw, something was wrong with the location you - provided in the INVITE". The specific problem with the location is - indicated by the Geolocation-Error code. The "inserter=" parameter - identifies the Location Inserter this locationErrorValue is intended - for. - - Each locationErrorValue is destined for one "inserter=" entity. - This gives a Location Recipient a mechanism to tell each inserter - what the Location Recipient concluded was wrong with the location - the "inserter=" entity included. Therefore, - - o there MUST be a locationErrorValue for each locationValue that - was considered bad by the UAS to ensure each upstream location - inserter understands which error code is intended for the - inserter (and which to ignore). - - o there MUST NOT be more than one locationErrorValue in the - response per locationValue in the request. - - o there MUST NOT be more than one locationErrorValue with the same - "inserter=" entity in the request. - - o there MUST NOT be a locationErrorValue in the response for a - locationValue in the request that was not in error, according to - the Location Recipient. - - Here is an example of a Geolocation-Error header field - - Geolocation-Error: 201; code="Linkable Target Identity Required"; - node="server42.example.com"; - inserter="alice.example.com"; - - The above example says that the Location Recipient is - server42.example.com, and this entity cannot verify the Target's - identity within this message. This is typically needed in order to - make routing decisions for the SIP request where the "entity=" - attribute has an unlinkable pseudonym obscuring a location Target's - identity from the signaling. This is not desire because if Alice's - message is to be routed based on the location in the SIP request, - server42 has to verify that this is Alice's location. The - appropriate action is to send a 424 (Bad Location Information) - response with the above (201) Geolocation-Error header value. We do - not want Alice's request routed based on Bob's location. - - See Section 4.3 for further rules about the Geolocation-Error header - field and the locationErrorValue. - - This document says nothing about what a Location Recipient does with - more than one 'good' locationValue in a request (i.e., which to - choose to use). This scenario MAY be addressed in a future effort. - - Further, more than one error code is allowed in the - locationErrorValue - each having one "inserter=" parameter. - -6.3 Proxy Behavior - - [RFC3261] states message bodies cannot be added by proxies. - However, proxies are permitted to add a header field to a request. - This means that a proxy can add a Geolocation locationValue header - field with a dereferencable location URI, but not an LbyV message - body. - - It is allowed, but NOT RECOMMENDED, for more than one SIP element to - insert location into a request along its path. As described earlier - in this document, each insertion of location into a SIP request is - accompanied by a new locationValue in a Geolocation header field. - Also described earlier, each locationValue MUST contain an - "inserted-by=" value indicating to a Location Recipient the host - that inserted a specific location into a particular request. - - If, however, location is already in a SIP request, a SIP server - SHOULD NOT add another location URI that identifies the same Target - in the PIDF-LO (in the "entity=" attribute) to the same request. - This will likely cause confusion at the Location Recipient as to - which to use. - - More than one Geolocation locationValue in a message is permitted, - but can cause confusion at the recipient. If a proxy chooses to add - a locationValue to a Geolocation header field, which would be a - local policy decision, the new locationValue MUST be added to the - end of the header field (after previous locationValue(s)). This is - done to create an order of insertion of locationValues along the - path. Proxies MUST NOT modify the order of locationValues in a - geolocation header field. Section 4 covers more details with - respect to the rules of usage for the Geolocation header value(s). - Each rule MUST be obeyed as written there. - - A proxy wishing to dereference a location URI contained in a - received request will use the 'presence' event package in a - SUBSCRIBE request to the URI, but only if the "routing-allowed" - header parameter is set to "=yes". This transaction is described in - Section 4.5. If accepted, the LS will return the PIDF-LO to the - proxy in a NOTIFY request. If there are any errors during - dereferencing, or in the PIDF-LO itself, the proxy will send an - error to the UAC with a locationErrorValue indicating what the proxy - concluded was wrong with the location. This is to include any - dereferencing problems encountered. - -6.3.1 Proxy Behavior with Geolocation Header Field Parameters - - SIP servers MUST NOT delete any existing Geolocation locationValue - (URI or header field parameter) from a request. An existing - locationValue MAY be modified by adding a "used-for-routing" - parameter to an existing locationValue, if the request was - retargeted based on the location within that locationValue. - - According to this specification, the default value of any - Geolocation header value "routing-allowed" is "no". If a Geolocation - header value is received by a SIP server with a "routing-allowed" - parameter set to "=no", the SIP server MUST NOT view or dereference - the location in the SIP request. If there is no "routing-allowed" - parameter in the SIP request (i.e., all instances of Geolocation - header field rows (as defined in section 7.3.1 of RFC 3261), the - previously stated default is to treat the Geolocation header value - as if it contained a "routing-allowed=no" parameter, without - exception. Therefore, this parameter does not have to be present to - deny SIP servers along the signaling path the ability to view the - Target's location. This parameter MAY be added in transit by a SIP - server, and MUST be with a value of "no". - - For example, an existing Geolocation locationValue in a request of: - - Geolocation: ; - inserted-by="alice123@atlanta.example.com" - - can be modified by a proxy to add the "used-for-routing" parameter, - like this: - - Geolocation: ; - inserted-by="alice123@atlanta.example.com", - used-for-routing - - if this is the locationValue the proxy used to make a retargeting - decision based upon, but the proxy can make no other modification. - - A SIP server MAY add a new Geolocation locationValue to a SIP - request. The server SHOULD NOT insert a locationValue of a Target - unless it is reasonably certain it knows the actual geographic - location of the Location Target (for example, if it thoroughly - understands the topology of the underlying access network and it can - identify the device location reliably, even in the presence of NAT - or VPN). Routing errors are likely if the SIP server inserts an - incorrect locationValue. - - A locationValue added to an existing Geolocation header field - would look like: - - Geolocation: ; - inserted-by="alice123@atlanta.example.com", - ; - inserted-by="ls7.atlanta.example.com" - - Notice the locationValue added by proxy "ls7" is last among - locationValues. Proxies MUST add locationValue at the end of all - locationValues that are already present in the request. - - If this request was then retargeted by an intermediary using the - locationValue inserted by server "ls7", the intermediary would add a - "used-for-routing" parameter like this: - - Geolocation: ; - inserted-by="alice123@atlanta.example.com", - ; - inserted-by="ls7.atlanta.example.com", used-for-routing - - It is conceivable that an initial routing decision is made on - one locationValue, and subsequently another routing decision is - made on a different locationValue further towards the ultimate - destination. This retargeting decision can be made on a newly - inserted locationValue. While unusual, it can occur. In such a - case, proxies MUST NOT remove any existing "used-for-routing" header - field parameter. In this instance, the SIP server retargeting based - on another locationValue MUST add the "used-for-routing" header - field parameter to the locationValue used for retargeting by this - server. This will result in a Geolocation header field indicating - that the request has been retargeted more than once, which is - allowed. - - A Proxy that inserts or adds locationValue into a request MAY move a - 'geolocation' option tag that is in a Supported header field into a - Require header field if this proxy deems geolocation to be - sufficiently important to Location Recipient(s) of this request. - - A proxy can read any locationValue present, and the associated body, - if not S/MIME protected, and can use the contents of the header - field to make location-based retargeting decisions, if retargeting - requests based on location is a function of that proxy. Retargeting - is defined in [RFC3261]. However, if the Geolocation header field - parameter "routing-allowed" is present and set to "no", or is not - present (the default behavior is "no" if "routing-allowed" is not - present, whether or not a Geolocation header field is present), SIP - servers MUST NOT view the contents of the location message body. - Further, SIP servers MUST NOT attempt to dereference a location URI. - This is because the Location Inserter (likely the originating UAC) - did not give the SIP server permission to view the location within - the SIP request. How a SIP server indicates it requires permission - to view a request's location in order to properly process this - request is described in section 6.3.2. - - If the Geolocation header field parameter "routing-allowed" is - present in a SIP request, the value MUST NOT be changed during - processing of the request. If the Geolocation header field - parameter "routing-allowed" is not present, SIP servers MUST treat - the location within the request as if the header field parameter - "routing-allowed" were present and set to "no". - - B2BUAs and SBCs should also adhere to the above proxy guidance with - respect to the "Routing-allowed" header field parameter. In other - words, if the particular type of SIP server mentioned here supports - this SIP extension and is not the ultimate destination of this SIP - request, each policy rule within the Geolocation header field MUST - remain intact and unchanged. - - SIP server MUST NOT delete a "routing-allowed" header field - parameter, but if one is not yet present, any SIP server MAY add a - "Routing-allowed" header field parameter with the value set to "no" - only. - -6.3.2 Proxy Error Behavior for Sending or Receiving locationErrorValues - - For proxies that receive a SIP request that contains a location - error, all the rules applicable to a UAS apply (see Section 6.2.1.). - The one point to add is that a proxy does not need to examine - location contained in a request. Section 6.2.1. only applies to - proxies that need to monitor or police location within requests (for - whatever reason). - - If a proxy inserted a locationValue into a request, it MUST be - ready to examine the response to that request, in case there is one - or more location errors in the response. To a great degree, this - scenario has the proxy behaving as a UAC (see section 6.1.1.) that - included a locationValue a request, which then receives an error to - that locationValue. - - This location-inserting proxy SHOULD be (at least) transaction - stateful for the response. If the proxy is configured as a - stateless proxy, and it inserts location, it MUST process and - monitor all SIP responses, looking for locationErrorValues that - indicate it was the "inserter=" to learn that the location it - supplied was in error. It SHOULD react according to the error code - received. This document gives no guidance what the proxy should do - to rectify the bad location information, since the proxy is not the - SIP response destination, but a future document could address this. - - The "routing-allowed" parameter's purpose is to indicate if SIP - servers along the signaling path should bother looking at the - location message body or dereferencing the location URI. There are - two values specified here for this parameter: "yes" and "no". If - the "routing-allowed" parameter is set to "yes", and the SIP server - determines this SIP request should be routed based on the Target's - location, this parameter gives the server permission to look at the - location (or dereference it). If this parameter is set to "no", - then the SIP server MUST NOT view the location message body or - dereference the location URI within this SIP request. If the SIP - server believes it cannot process this message properly because it - needs to learn the Target's location in order to route the message, - then it MUST return a 424 (Bad Location Information) response, - indicating it requires permission (error code 402) to view the - location. + CSeq: 31863 INVITE + Contact: + Content-Type: multipart/mixed; boundary=boundary1 + Content-Length: ... - Here is an example of a Geolocation-Error header field + --boundary1 - Geolocation-Error: 402; code="Permission to Route based on - Location Information"; - node="bob.example.com"; - inserter="alice.example.com"; + Content-Type: application/sdp - The above example says that the Location Recipient is - server42.example.com, and this entity believes it cannot route this - message without knowing permission to view the Target's location. - Regardless of whether there is a Geolocation header value parameter, - such as + ...SDP goes here - routing-allowed=no + --boundary1 - or this parameter is not present in the SIP request (as shown 402 - error example above). The default behavior is to act as if the - parameter is present and set to "=no". Server42 MUST get permission - to view the Target's location by reading a routing-allowed header - parameter saying "=yes", otherwise a 402 error is sent back to the - "inserter=" entity to get permission. + + + + + + + + + 32.86726 -97.16054 + + + + + no + 2010-07-30T20:00:00Z + + 802.11 + + mac:1234567890ab + 2010-07-28T20:57:29Z + + + + + + US + Texas + Colleyville + 3913 + Treemont + Circle + 76034 + Haley's Place + 1 + + + + no + 2010-07-30T20:00:00Z + triangulation + + + 2010-07-28T12:28:04Z + + + - Section 4.3 highlights this example, stating the user, Alice, MUST - be made aware of this location revelation request. This document - does not give any guidance how Alice is to be informed (i.e., audio, - visual, etc). Alice can grant permission or choose not to, knowing - this SIP request attempt (to this destination, at this time) will - fail. The problem might not recur if a future SIP request were to - travel through a different server than server42 (or it might again). + --boundary1-- -7. Geopriv Privacy Considerations +6. Geopriv Privacy Considerations Location information is considered by most to be highly sensitive information, requiring protection from eavesdropping, and altering in transit. [RFC3693] articulates rules to be followed by any protocol wishing to be considered a "Using Protocol", specifying how a transport protocol meets those rules. This section describes how SIP as a Using Protocol meets those requirements. Quoting requirement #4 of [RFC3693]: @@ -2170,269 +825,221 @@ "(Single Message Transfer) In particular, for tracking of small Target devices, the design should allow a single message/packet transmission of location as a complete transaction." When used for tracking, a simple NOTIFY or UPDATE normally is relatively small, although the PIDF itself can be large. Normal RFC 3261 procedures of reverting to TCP when the MTU size is exceeded would be invoked. -8. Security Considerations +7. Security Considerations Conveyance of physical location of a UA raises privacy concerns, and depending on use, there probably will be authentication and integrity concerns. This document calls for conveyance to - be accomplished through secure mechanisms, like S/MIME protecting - message bodies (although this is not widely deployed) or TLS - protecting the overall signaling. In cases where a session set-up - is retargeted based on the location of the UA initiating the call - or SIP MESSAGE, securing the LbyV location with an end-to-end - mechanism such as S/MIME is problematic, because one or more proxies - on the path need the ability to read the location information to - retarget the message to the appropriate new destination UAS. + be accomplished through secure mechanisms, like S/MIME encrypting + message bodies (although this is not widely deployed), TLS + protecting the overall signaling or conveyance location by-reference + and requiring all entities that dereference location to authenticate + themselves. In location-based routing cases, encrypting the + location payload with an end-to-end mechanism such as S/MIME is + problematic, because one or more proxies on the path need the + ability to read the location information to retarget the message to + the appropriate new destination UAS. Data can only be encrypted to a + particular, anticipated target, and thus if multiple recipients need + to inspect a piece of data, and those recipients cannot be predicted + by the sender of data, encryption is not a very feasible choice. Securing the location hop-by-hop, using TLS, protects the message - from eavesdropping and modification, but exposes the information to - all proxies on the path as well as the endpoint. In most cases, the - UA does not know the identity of the proxy or proxies providing - location-based routing services, so that end-to-middle solutions - might not be appropriate either. + from eavesdropping and modification in transit, but exposes the + information to all proxies on the path as well as the endpoint. In + most cases, the UA has no trust relationship with the proxy or + proxies providing location-based routing services, so such + end-to-middle solutions might not be appropriate either. - These same issues exist for basic SIP signaling, but SIP normally - does not carry information to physically track a user. This - extension is especially sensitive. That said, there is the ability, - according to [RFC3693] to have an anonymous identity for the - Target's location. This is accomplished by use of an unlinkable - pseudonym in the "entity=" attribute of the element - [RFC4479]. Though, this can be problematic for routing messages - based on location (covered several times in the document above). + When location information is conveyed by reference, however, one can + properly authenticate and authorize each entity that wishes to + inspect location information. This does not require that the sender + of data anticipate who will receive data, and it does permit + multiple entities to receive it securely, but it does not however + obviate the need for pre-association between the sender of data and + any prospective recipients. Obviously, in some contexts this + pre-association cannot be presumed; when it is not, effectively + unauthenticated access to location information must be permitted. In + this case, choosing pseudo-random URIs for location by-reference, + coupled with path encryption like SIPS, can help to ensure that only + entities on the SIP signaling path learn the URI, and thus restores + rough parity with sending location by-value. + + Location information is especially sensitive when the identity of + its Target is obvious. Note that there is the ability, according to + [RFC3693] to have an anonymous identity for the Target's location. + This is accomplished by use of an unlinkable pseudonym in the + "entity=" attribute of the element [RFC4479]. Though, + this can be problematic for routing messages based on location + (covered in the document above). Moreover, anyone fishing for + information would correlate the identity at the SIP layer with that + of the location information referenced by SIP signaling. When a UA inserts location, the UA sets the policy on whether to reveal its location along the signaling path - as discussed in Section 4, as well as flags in the PIDF-LO [RFC4119]. UAC implementations MUST make such capabilities conditional on explicit - user permission, and SHOULD alert the user that location is being - conveyed. Proxies inserting location for location-based routing are - unable to alert users, and such use is NOT RECOMMENDED. Proxies - conveying location using this extension MUST have the permission of - the Target to do so. + user permission, and MUST alert the user that location is being + conveyed. This SIP extension offers the default ability to require permission to view location while the SIP request is in transit. The default - for this is set to "no", and there is an error explicitly describing + for this is set to "no". There is an error explicitly describing how an intermediary asks for permission to view the Target's - location. - - Because Target locations can be placed on a Location Server - accessible with the possession of a location URI, this URI has its - own security considerations. It is tempting to assume that the - dereference of this URI would have authentication, authorization and - other security mechanisms that limit the access to information. - Unfortunately, this might not be true. The access network the UA is - connected to can be the source of location reference, and it might - not have any credentialing mechanism suitable for controlling access - to a Target's location. Consider, specifically, a nomadic user - connected to an access network in a hotel. The UA has no way to - provide a credential acceptable of the hotel Location Server (LS) to - any of its intended Location Recipients. The recipient of a - reference does not know if a reference has appropriate authorization - policies or not. - - Accordingly, possession of the reference should be considered - equivalent to possession of the value, and the reference should be - treated with the same degree of care as the value. Specifically, - TLS MUST be used to protect the security of the reference. Notice - that this specification does not constrain the dereference protocol - to use TLS. That specification is left entirely to the dereferencing - protocol documents. + location, plus a rule stating the user has to be made aware of this + permission request. There is no end-to-end integrity on any locationValue or locationErrorValue header field parameter (or middle-to-end if the value was inserted by a intermediary), so recipients of either header field need to implicitly trust the header field contents, and take whatever precautions each entity deems appropriate given this - situation. Any idea of using SIP Identity is lost as soon as it is - realized that the Geolocation header value can be added to by - intermediaries in the signaling path. + situation. -9. IANA Considerations +8. IANA Considerations The following are the IANA considerations made by this SIP extension. Modifications and additions to these registrations require a standards track RFC (Standards Action). [Editor's Note: RFC-Editor - within the IANA section, please replace "this doc" with the assigned RFC number, if this document reaches publication.] -9.1 IANA Registration for the SIP Geolocation Header Field +8.1 IANA Registration for the SIP Geolocation Header Field The SIP Geolocation Header Field is created by this document, with its definition and rules in Section 4.1 of this document, and should be added to the IANA sip-parameters registry, in the portion titled "Header Field Parameters and Parameter Values". Predefined Header Field Parameter Name Values Reference ---------------- ------------------- ---------- --------- - Geolocation inserted-by= no [this doc] - Geolocation used-for-routing yes [this doc] Geolocation routing-allowed yes [this doc] -9.2 IANA Registration for New SIP Option Tag +8.2 IANA Registration for New SIP 'geolocation' Option Tag The SIP option tag "geolocation" is created by this document, with the definition and rule in Section 4.4 of this document, to be added to the IANA sip-parameters registry. -9.3 IANA Registration for Response Code 424 +8.3 IANA Registration for 424 Response Code Reference: RFC-XXXX (i.e., this document) Response code: 424 (recommended number to assign) Default reason phrase: Bad Location Information This SIP Response code is defined in section 4.2 of this document. -9.4 IANA Registration of New Geolocation-Error Header Field +8.4 IANA Registration of New Geolocation-Error Header Field The SIP Geolocation-error header field is created by this document, with its definition and rules in Section 4.3 of this document, to be added to the IANA sip-parameters registry, in the portion titled "Header Field Parameters and Parameter Values". Predefined Header Field Parameter Name Values Reference ----------------- ------------------- ---------- --------- - Geolocation-Error inserter= no [this doc] - Geolocation-Error node= no [this doc] Geolocation-Error code= yes* [this doc] * see section 9.5 for the newly created values. -9.5 IANA Registration for the SIP Geolocation-Error Codes +8.5 IANA Registration for the SIP Geolocation-Error Codes New location specific Geolocation-Error codes are created by this document, and registered in a new table in the IANA sip-parameters registry. Details of these error codes are in Section 4.3 of this document. Geolocation-Error codes ----------------------- Geolocation-Error codes provide reason for the error discovered by Location Recipients, categorized by action to be taken by error - recipient to be placed into SIP responses to inform the location - inserter of the error. + recipient. Code Description Reference ---- --------------------------------------------------- --------- - 100 "Cannot Process Location" General location error, [this doc] - meaning location in the request cannot be - processed at this time. No actionable guidance. - Can be treated as a 200 or 300 error by error - recipient. - - 200 "Retry Location Later with same data" The location [this doc] - cannot be processed at this time. Error recipient - should try again with same data. - - 201 "Linkable Target Identity Required" [this doc] - Target's identity cannot be unlinkable within - the presence element's "entity=" attribute. This - is necessary for routing SIP requests based - on Target's location (and some other entity's). + 100 "Cannot Process Location" [this doc] - 300 "Retry Location Later with device updated location" [this doc] - Location cannot be processed at this time. Error - recipient should try again with same data. + 200 "Retry Location Later with device updated location" [this doc] - 400 "Permission To Use Location Information " [this doc] - Permission is being requested from the calling - user to reveal and or use location in request - before request can be processed. This error - informs the "inserter=" entity that permission - is required to process this SIP request. Ruleholder - MUST be informed of permission request. + 300 "Permission To Use Location Information" [this doc] - 401 "Permission To Retransmit Location Information to a Third Party" - Permission from the calling user to send location [this doc] - information to a third party entity - not in the - signaling path. This flag is in the PIDF-LO. The - user MUST be informed of permission request. + 301 "Permission To Retransmit Location Information to a Third Party" + [this doc] - 402 "Permission to Route based on Location Information" [this doc] - Permission from calling user to reveal location - in request before request can be processed. This - is a routing by location error. The user MUST be - informed of permission request. + 302 "Permission to Route based on Location Information" [this doc] - 500 "Location Information Denial" Request has been [this doc] - Explicitly denied because of the location in - the request. Sender should not try again. + 400 "Location Information Denial" [this doc] -9.6 IANA Registration of Location URI Schemes +8.6 IANA Registration of Location URI Schemes This document directs IANA to create a new set of parameters in a separate location from SIP and Geopriv, called the "Location Reference URI" registry, containing the URI scheme, the Content-Type, and the reference, as follows: URI Scheme Content-Type Reference ---------- ------------ --------- SIP: [this doc] SIPS: [this doc] PRES: [this doc] Additions to this registry must be defined in a permanent and readily available specification (this is the "Specification - Required" IANA policy defined in [RFC5226]).. + Required" IANA policy defined in [RFC5226]). -10. Acknowledgements +9. Acknowledgements To Dave Oran for helping to shape this idea. - To Jon Peterson and Dean Willis on guidance of the effort. + To Dean Willis for guidance of the effort. To Allison Mankin, Dick Knight, Hannes Tschofenig, Henning Schulzrinne, James Winterbottom, Jeroen van Bemmel, Jean-Francois Mule, Jonathan Rosenberg, Keith Drage, Marc Linsner, Martin Thomson, Mike Hammer, Ted Hardie, Shida Shubert, Umesh Sharma, Richard Barnes, Dan Wing, Matt Lepinski, John Elwell and Jacqueline Lee for constructive feedback and nits checking. Special thanks to Paul Kyzivat for his help with the ABNF in this document and to Robert Sparks for many helpful comments and the proper construction of the Geolocation-Error header field. And finally, to Spencer Dawkins for giving this doc a good scrubbing to make it more readable. -11. References +10. References -11.1 References - Normative +10.1 Normative References [RFC3261] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, May 2002. [RFC4119] J. Peterson, "A Presence-based GEOPRIV Location Object Format", RFC 4119, December 2005 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997 [RFC2392] E. Levinson, " Content-ID and Message-ID Uniform Resource Locators", RFC 2392, August 1998 - [RFC3863] H. Sugano, S. Fujimoto, G. Klyne, A. Bateman, W. Carr, J. - Peterson, "Presence Information Data Format (PIDF)", RFC - 3863, August 2004 - [RFC3856] J. Rosenberg, " A Presence Event Package for the Session Initiation Protocol (SIP)", RFC 3856, August 2004 [RFC3859] J. Peterson, "Common Profile for Presence (CPP)", RFC 3859, August 2004 [RFC3428] B. Campbell, Ed., J. Rosenberg, H. Schulzrinne, C. Huitema, D. Gurle, "Session Initiation Protocol (SIP) Extension for Instant Messaging" , RFC 3428, December 2002 @@ -2450,58 +1057,52 @@ [RFC3515] R. Sparks, "The Session Initiation Protocol (SIP) Refer Method", RFC 3515, April 2003 [RFC3903] Niemi, A, "Session Initiation Protocol (SIP) Extension for Event State Publication", RFC 3903, October 2004. [RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. - [IANA-civic] http://www.iana.org/assignments/civic-address-types- - Registry - [RFC5226] T. Narten, H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 5226, May 2008 [RFC4479] J. Rosenberg, "A Data Model for Presence", RFC 4479, July 2006 -11.2 References - Informative - - [RFC3693] J. Cuellar, J. Morris, D. Mulligan, J. Peterson. J. Polk, - "Geopriv Requirements", RFC 3693, February 2004 + [RFC3264] J. Rosenberg, H. Schulzrinne, "The Offer/Answer Model with + Session Description Protocol", RFC 3264, June 2002 [RFC4483] E. Berger, "A Mechanism for Content Indirection in SIP", RFC 4483, May 2006 - [RFC3825] J. Polk, J. Schnizlein, M. Linsner, "Dynamic Host - Configuration Protocol Option for Coordinate-based Location - Configuration Information", RFC 3825, July 2004 + [RFC5491] J. Winterbottom, M. Thomson, H. Tschofenig, "GEOPRIV PIDF-LO + Usage Clarification, Considerations, and Recommendations ", + RFC 5491, March 2009 - [RFC4776] H. Schulzrinne, " Dynamic Host Configuration Protocol - (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration - Information ", RFC 4776, October 2006 +10.2 Informative References - [ID-PHONE] B. Rosen, J. Polk, "ECRIT Phone BCP", - draft-ietf-ecrit-phonebcp, "work in progress", Jan 2010 + [RFC3693] J. Cuellar, J. Morris, D. Mulligan, J. Peterson. J. Polk, + "Geopriv Requirements", RFC 3693, February 2004 [ID-GEO-FILTERS] R. Mahy, B. Rosen, H. Tschofenig, "Filtering Location Notifications in SIP", draft-ietf-geopriv-loc-filters, "work - in progress", December 2009 + in progress", March 2010 - Author Information +Authors' Addresses James Polk Cisco Systems 3913 Treemont Circle Colleyville, Texas 76034 + 33.00111N 96.68142W Phone: +1-817-271-3552 Email: jmpolk@cisco.com Brian Rosen NeuStar, Inc. 470 Conrad Dr. Mars, PA 16046 @@ -2504,20 +1105,24 @@ Brian Rosen NeuStar, Inc. 470 Conrad Dr. Mars, PA 16046 40.70497N 80.01252W Phone: +1 724 382 1051 Email: br@brianrosen.net + Jon Peterson + NeuStar, Inc. + + Email: jon.peterson@neustar.biz Appendix A. Requirements for SIP Location Conveyance The following subsections address the requirements placed on the UAC, the UAS, as well as SIP proxies when conveying location. If a requirement is not obvious in intent, a motivational statement is included below it. A.1 Requirements for a UAC Conveying Location