ecrit B. Rosen Internet-Draft NeuStar Intended status: Standards Track J. Polk Expires: August 28, 2008 Cisco Systems February 25, 2008 Best Current Practice for Communications Services in support of Emergency Calling draft-ietf-ecrit-phonebcp-04 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 28, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract The IETF and other standards organization have efforts targeted at standardizing various aspects of placing emergency calls on IP networks. This memo describes best current practice on how devices, networks and services should use such standards to make emergency calls. Rosen & Polk Expires August 28, 2008 [Page 1] Internet-Draft Emergency Call Phone BCP February 2008 Table of Contents 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Overview of how emergency calls are placed . . . . . . . . . . 3 4. Which devices and services should support emergency calls . . 4 5. Identifying an emergency call . . . . . . . . . . . . . . . . 4 6. Location and its role in an emergency call . . . . . . . . . . 5 6.1. Types of location information . . . . . . . . . . . . . . 5 6.2. Location Determination . . . . . . . . . . . . . . . . . . 5 6.2.1. User-entered location information . . . . . . . . . . 6 6.2.2. Access network "wire database" location information . . . . . . . . . . . . . . . . . . . . . 6 6.2.3. End-system measured location information . . . . . . . 6 6.2.4. Network-measured location information . . . . . . . . 6 6.3. Who adds location, endpoint or proxy . . . . . . . . . . . 7 6.4. Location and references to location . . . . . . . . . . . 7 6.5. End system location configuration . . . . . . . . . . . . 7 6.6. When location should be configured . . . . . . . . . . . . 8 6.7. Conveying location in SIP . . . . . . . . . . . . . . . . 9 6.8. Location updates . . . . . . . . . . . . . . . . . . . . . 10 6.9. Multiple locations . . . . . . . . . . . . . . . . . . . . 10 6.10. Location validation . . . . . . . . . . . . . . . . . . . 11 6.11. Default location . . . . . . . . . . . . . . . . . . . . . 11 6.12. Other location considerations . . . . . . . . . . . . . . 11 7. LIS and LoST Discovery . . . . . . . . . . . . . . . . . . . . 11 8. Routing the call to the PSAP . . . . . . . . . . . . . . . . . 12 9. Signaling of emergency calls . . . . . . . . . . . . . . . . . 13 9.1. Use of TLS . . . . . . . . . . . . . . . . . . . . . . . . 13 9.2. SIP signaling requirements for User Agents . . . . . . . . 13 9.3. SIP signaling requirements for proxy servers . . . . . . . 15 10. Call backs . . . . . . . . . . . . . . . . . . . . . . . . . . 15 11. Mid-call behavior . . . . . . . . . . . . . . . . . . . . . . 16 12. Call termination . . . . . . . . . . . . . . . . . . . . . . . 16 13. Disabling of features . . . . . . . . . . . . . . . . . . . . 16 14. Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 15. Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 16. Security Considerations . . . . . . . . . . . . . . . . . . . 18 17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 18. Normative References . . . . . . . . . . . . . . . . . . . . . 19 Appendix A. BCP Requirements Sorted by Responsible Party . . . . 24 A.1. Requirements of End Devices . . . . . . . . . . . . . . . 24 A.2. Requirements of Service Providers . . . . . . . . . . . . 32 A.3. Requirements of Access Network . . . . . . . . . . . . . . 37 A.4. Requirements of Intermediate Devices . . . . . . . . . . . 39 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 42 Intellectual Property and Copyright Statements . . . . . . . . . . 43 Rosen & Polk Expires August 28, 2008 [Page 2] Internet-Draft Emergency Call Phone BCP February 2008 1. Terminology 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]. This document uses terms from [RFC3261], [I-D.ietf-ecrit-requirements] and [I-D.ietf-ecrit-framework]. 2. Introduction This document describes how access networks, SIP user agents, proxy servers and PSAPs support emergency calling, as outlined in [I-D.ietf-ecrit-framework], which is designed to complement the present document in section headings, numbering and content. This BCP succinctly describes the requirements of end devicesand applications (requirements prefaced by "ED-"), access networks (requirements prefaced by "AN-", service providers (requirements prefaced by "SP-") and PSAPs to achieve globally interoperable emergency calling on the Internet. This document also defines requirements for "Intermediate" devices which exist between end devices or applications and the access network. For example, a home router is an "Intermediate" device. Reporting location on an emergency call (see Section 6 may depend on the ability of such intermediate devices to meet the requirements prefaced by "INT-". 3. Overview of how emergency calls are placed An emergency call can be distinguished (Section 5) from any other call by a unique Service URN[I-D.ietf-ecrit-service-urn], which is placed in the call set-up signaling when a home or visited emergency dial string is detected. Because emergency services are local to specific geographic regions, a caller must obtain his location (Section 6) prior to making emergency calls. To get this location, either a form of measuring (e.g., GPS) (Section 6.2.3) device location in the endpoint is deployed, or the endpoint is configured (Section 6.5) with its location from the access network's Location Information Server (LIS). The location is conveyed (Section 6.7) in the SIP signaling with the call. The call is routed (Section 8) based on location using the LoST protocol [I-D.ietf-ecrit-lost], which maps a location to a set of PSAP URIs. Each URI resolves to a PSAP or an Emergency Services Routing Proxy (ESRP), which serves a group of PSAPs. The call arrives at the PSAP with the location included in the SIP INVITE request. Rosen & Polk Expires August 28, 2008 [Page 3] Internet-Draft Emergency Call Phone BCP February 2008 4. Which devices and services should support emergency calls ED-1 A device or application SHOULD support emergency calling if a user could reasonably expect to be able to place a call for help with the device. SP-1 If a device or application expects to be able to place a call for help, the service provider that supports it MUST facilitate emergency calling. ED-2 Devices that create media sessions and exchange audio, video and/or text, and have the capability to establish sessions to a wide variety of addresses, and communicate over private IP networks or the Internet, SHOULD support emergency calls. 5. Identifying an emergency call ED-3 Endpoints SHOULD recognize dial strings of emergency calls. If the service provider always knows the location of the device, then the service provider could recognize them. SP-2 Proxy servers SHOULD recognize emergency dial string if for some reason the endpoint does not recognize them. This cannot be relied upon by the device if the service provider cannot always determine the location of the device. ED-4/SP-3 Emergency calls MUST be marked with a Service URN in the Request-URI of the INVITE. ED-5/SP-4 Local dial strings MUST be recognized. ED-6/SP-5 Home dial strings MAY be recognized. ED-7/SP-6 Local emergency dial strings SHOULD be determined from LoST [I-D.ietf-ecrit-lost]. ED-8 Endpoints which do not recognize emergency dial strings SHOULD send dial strings as per [RFC4967]. SP-7 Proxy Servers MUST recognize emergency dial strings represented by [RFC4967] and SHOULD recognize emergency dial strings represented by a tel URI [RFC3966]. SP-8 Service providers MAY provide home dial strings by configuration [I-D.ietf-sipping-config-framework]. ED-9 Endpoints SHOULD be able to have home dial strings provisioned Rosen & Polk Expires August 28, 2008 [Page 4] Internet-Draft Emergency Call Phone BCP February 2008 by configuration. ED-10 Devices SHOULD NOT have one button emergency calling initiation. ED-11/SP-9 All emergency services specified in [I-D.ietf-ecrit-service-urn] MUST be recognized. 6. Location and its role in an emergency call Handling location for emergency calling usually involves several steps to process and multiple elements are involved. In Internet emergency calling, where the endpoint is located is "determined" using a variety of measurement or wiretracing methods. Endpoints may be "configured" with their own location by the access network. In some circumstances, a proxy server may insert location into the signaling on behalf of the endpoint. The location is "mapped" to the URI to send the call to, and the location is "conveyed" to the PSAP (and other elements) in the signaling. Likewise, we employ Location Configuration Protocols, the Location-to-Service Mapping Protocol, and Location Conveyance Protocols for these functions. The Location- to-Service Translation protocol [I-D.ietf-ecrit-lost] is the Location Mapping Protocol defined by the IETF. 6.1. Types of location information There are several forms of location. In IETF protocols, civic and geospatial (geo) forms are both supported. The civic forms include both postal and jurisdictional fields. A cell tower/sector can be represented as a point (geo or civic) or polygon. Other forms of location representation must be mapped into either a geo or civic for use in emergency calls. ED-12/INT-1/SP-10 Endpoints, Intermediate Devices and Service Providers MUST be prepared to handle location represented in either civic or geo form. ED-13/INT-2/SP-11/AN-1 Elements MUST NOT convert (civic to geo or geo to civic) from the form of location the determination mechanism supplied. 6.2. Location Determination ED-14/INT-3/AN-2 Any suitable location determination mechanism MAY be used. Rosen & Polk Expires August 28, 2008 [Page 5] Internet-Draft Emergency Call Phone BCP February 2008 6.2.1. User-entered location information ED-15/INT-4/AN-3 Devices, intermediate Devices and/or access networks SHOULD support a manual method to "override" the location the access network determines. Where a civic form of location is provided, all fields in the PIDF-LO [RFC4119] and [RFC5139] MUST be able to be specified. 6.2.2. Access network "wire database" location information AN-4 Access networks supporting copper, fiber or other hard wired IP packet service SHOULD support location configuration. If the network does not support location configuration, it MUST require every device that connects to the network to support end system measured location. AN-5/INT-5 Access networks and intermediate devices providing wire database location information SHOULD provide interior location data (building, floor, room, cubicle) where possible. It is RECOMMENDED that interior location be provided when spaces exceed approximately 650 square meters. AN-6/INT-6 Access networks and intermediate devices (including enterprise networks) which support intermediate range wireless connections (typically 100m or less of range) and which do not support a more accurate location determination mechanism such as triangulation, MUST support location configuration where the location of the access point is reflected as the location of the clients of that access point. Where the access network provides location configuration, intermediate devices MUST either be transparent to it, or provide an interconnected client for the supported configuration mechanism and a server for a configuration protocol supported by end devices upstream of the intermediate device 6.2.3. End-system measured location information ED-16/INT-7 Devices MAY support end-system measured location. Uncertainty of less than 100 m with 95% confidence SHOULD be available for dispatch. ED-17/INT-8/AN-7 Devices that support endpoint measuring of location MUST have at least a coarse location capability (typically <1km accuracy when not location hiding) at all times for routing of calls. This mechanism MAY be a service provided by the access network. 6.2.4. Network-measured location information AN-8 Access networks MAY provide network-measured location determination. Wireless access network which do not support network Rosen & Polk Expires August 28, 2008 [Page 6] Internet-Draft Emergency Call Phone BCP February 2008 measured location MUST require that all devices connected to the network have end-system measured location. Uncertainty of less than 100 m with 95% confidence SHOULD be available for dispatch. AN-9 Access networks that provide network measured location MUST have at least a coarse location (typically <1km when not location hiding) capability at all times for routing of calls. AN-10 Access networks with range of <10 meters MUST provide a location to mobile devices connected to it. The location provided SHOULD be that of the access point location unless a more accurate mechanism is provided. 6.3. Who adds location, endpoint or proxy ED-18/INT-9 Endpoints SHOULD do configure their own location. SP-12 Proxies MAY provide location on behalf of devices if: o The proxy has a relationship with all access networks the device could connect to, and the relationship allows it to obtain location. o The proxy has an identifier, such as an IP address, that can be used by the access network to determine the location of the endpoint, even in the presence of NAT and VPN tunnels that may obscure the identifier between the access network and the service provider. ED-19/INT-10/SP-13 Where proxies provide location on behalf of endpoints, the the service provider MUST ensure that either the end device is provided with the local dial strings for its current location (where the end device recognizes dial strings), or the service provider proxy MUST detect the appropriate local dial strings at the time of the call. 6.4. Location and references to location ED-20/INT-11 Devices SHOULD be able to accept and forward location by value or by reference. An end device that receives location by reference (and does not also get the corresponding value) MUST be able to perform a dereference operation to obtain a value. 6.5. End system location configuration ED-21/INT-12 Devices MUST support all of: DHCP location options [RFC4676] and [RFC3825], HELD [I-D.ietf-geopriv-http-location-delivery] and LLDP-MED [LLDP-MED]. AN-11/INT-13 The access network MUST support at least one of: DHCP Rosen & Polk Expires August 28, 2008 [Page 7] Internet-Draft Emergency Call Phone BCP February 2008 location options, HELD or LLDP-MED. AN-12/INT-14 Where a router is employed between a LAN and WAN in a small (less than approximately 650 square meters) area, the router MUST be transparent to the location provided by the WAN to the LAN. This may mean the router must obtain location as a client from the WAN, and supply an LCP server to the LAN with the location it obtains. Where the area is larger, the LAN MUST have a location configuration mechanism meeting this BCP. ED-22/INT-15 Endpoints SHOULD try all LCPs supported by the device in any order or in parallel. The first one that succeeds in supplying location can be used. AN-13/INT-16 Access networks that support more than one LCP MUST reply with the same location information (within the limits of the data format for the specific LCP) for all LCPs it supports. ED-23/INT-17/SP-14 When HELD is the LCP, the request MUST specify a value of "emergencyRouting" for the "responseTime" parameter and use the resulting location for routing. If a value for dispatch location will be sent, another request with the "responseTime" parameter set to "emergencyDispatch" must be completed, with the result sent for dispatch purposes. ED-24 Where the operating system supporting application programs which need location for emergency calls does not allow access to Layer 2 and Layer 3 functions necessary for a client application to use DHCP location options and/or LLDP-MED, the operating system MUST provide a published API conforming to ED-12 through ED-21 and ED-21 through ED-31. It is RECOMMENDED that all operating systems provide such an API. 6.6. When location should be configured ED-25/INT-18 Endpoints SHOULD obtain location immediately after obtaining local network configuration information.When HELD is the LCP the client MUST support a random back-off period (between 30 seconds and 300 seconds) for re-trying the HELD query, when no response is received. ED-26/INT-19 If the device is configured to use DHCP for bootstrapping, it MUST include both options for location acquisition (civic and geodetic), the option for LIS discovery, and the option for LoST discovery as defined in [RFC4676], [RFC3825], [I-D.thomson-geopriv-lis-discovery] and [I-D.ietf-ecrit-dhc-lost-discovery]. Rosen & Polk Expires August 28, 2008 [Page 8] Internet-Draft Emergency Call Phone BCP February 2008 ED-27/INT-20 If the device sends a DHCP INFORM message, it MUST include both options for location acquisition (civic and geodetic), the option for LIS discovery, and the option for LoST discovery as defined in [RFC4676], [RFC3825], [I-D.thomson-geopriv-lis-discovery] and [I-D.ietf-ecrit-dhc-lost-discovery]. ED-28/INT-21 To minimize the effects of VPNs that do not allow split tunneling VPNs, location configuration SHOULD be attempted before such tunnels are established. ED-29/INT-22 Software which uses LCPs SHOULD locate and use the actual hardware network interface rather than a VPN tunnel interface to direct LCP requests to the LIS in the actual access network. AN-14 Network administrators MUST take care in assigning IP addresses such that VPN address assignments can be distinguished from local devices (by subnet choice, for example), and LISs SHOULD NOT attempt to provide location to addresses that arrive via VPN connections unless it can accurately determine the location for such addresses. AN-15 Placement of NAT devices where an LCP uses IP address for an identifier SHOULD consider the effect of the NAT on the LCP. The address used to query the LIS MUST be able to correctly identify the record in the LIS representing the location of the querying device ED-30/INT-23 For devices which are not expected to roam, refreshing location on the order of once per day is RECOMMENDED. ED-31/INT-24 For devices which roam, refresh of location information SHOULD be more frequent, with the frequency related to the mobility of the device and the ability of the access network to support the refresh operation. If the device can detect that it has moved, for example when it changes access points, the device SHOULD refresh its location. ED-32/INT-25/AN-16 It is RECOMMENDED that location determination not take longer than 250 ms to obtain routing location and systems SHOULD be designed such that the typical response is under 100 ms. However, as much as 3 seconds to obtain routing location MAY be tolerated if location accuracy can be substantially improved over what can be obtained in 250 ms. 6.7. Conveying location in SIP ED-33/SP-15 Location sent between SIP elements MUST be conveyed using [I-D.ietf-sip-location-conveyance]. Rosen & Polk Expires August 28, 2008 [Page 9] Internet-Draft Emergency Call Phone BCP February 2008 6.8. Location updates ED-34/AN-17 Where the absolute location or the accuracy of location of the endpoint may change between the time the call is received at the PSAP and the time dispatch is completed, location update mechanisms MUST be provided. ED-35/AN-18 Mobile devices MUST be provided with a mechanism to get repeated location updates to track the motion of the device during the complete processing of the call. ED-36/AN-19 The LIS SHOULD provide a location reference which permits a subscription with appropriate filtering. ED-37/AN-20 For calls sent with location-by-reference, with a SIP or SIPS scheme, the server resolving the reference MUST support a SUBSCRIBE [RFC3265] to the presence event [RFC3856]. For other location-by-reference schemes, the PSAP will have to repeatedly dereference the URI to determine if the device moved. ED-38 If location was sent by value, and the endpoint gets updated location, it MUST send the updated location to the PSAP via a SIP re- INVITE or UPDATE request. Such updates SHOULD be limited to no more than one update every 10 seconds. 6.9. Multiple locations ED-39 If a UA has more than one location available to it, it MUST choose one location to route the call towards the PSAP. SP-16 If a proxy inserts location on behalf of an endpoint, and it has multiple locations available for the endpoint it MUST choose one location to use to route the call towards the PSAP. SP-17 If a proxy is attempting to insert location but the UA conveyed a location to it, the proxy MUST use the UA's location for routing and MUST convey that location towards the PSAP. It MAY also include what it believes the location to be in a separate Geolocation header. SP-18 All location objects received by a proxy MUST be delivered to the PSAP. ED-40/SP-19 Location objects MUST contain information about the method by which the location was determined, such as GPS, manually entered, or based on access network topology included in a PIDF- LO "method" element. In addition, the source of the location information MUST be included in a PIDF-LO "provided-by" element. Rosen & Polk Expires August 28, 2008 [Page 10] Internet-Draft Emergency Call Phone BCP February 2008 ED-41/SP-20 The "used-for-routing" parameter MUST be set to the location that was used to query LoST. 6.10. Location validation AN-21 A LIS should perform location validation of civic locations via LoST before entering a location in its database. ED-42 Endpoints SHOULD validate civic locations when they receive them from their LCP. Validation SHOULD be performed in conjunction with the LoST route query to minimize load on the LoST server. 6.11. Default location AN-22 When the access network cannot determine the actual location of the caller, it MUST supply a default location. The default SHOULD be chosen to be as close to the probable location of the device as the network can determine. See [I-D.ietf-ecrit-framework] SP-21 Proxies handling emergency calls MUST insert a default location if the call does not contain a location and the proxy does not have a method for obtaining a better location. AN-23/SP-22 Default locations MUST be marked with method=Default and the proxy MUST be identfied in provided-by element of the PIDF-LO. 6.12. Other location considerations ED-43 If the LCP does not return location in the form of a PIDF-LO [RFC4119], the endpoint MUST map the location information it receives from the configuration protocol to a PIDF-LO. ED-44/AN-24 To prevent against spoofing of the DHCP server, elements implementing DHCP for location configuration SHOULD use although the difficulty in providing appropriate credentials is significant. [RFC3118]. ED-45 S/MIME MUST NOT be used to encrypt the SIP Geolocation header or bodies. ED-46/SP-23 TLS MUST be used to protect location (but see Section 9.1). IPSEC [RFC2401] is an acceptable alternative. 7. LIS and LoST Discovery ED-47 Endpoints MUST support one or more mechanisms that allow them to determine their public IP address. Examples include ICE Rosen & Polk Expires August 28, 2008 [Page 11] Internet-Draft Emergency Call Phone BCP February 2008 [I-D.ietf-mmusic-ice] and HTTP get. ED-48 Endpoints MUST support LIS discovery as described in [I-D.thomson-geopriv-lis-discovery], and the LoST discovery as described in [I-D.ietf-ecrit-dhc-lost-discovery]. ED-49 The device MUST have a configurable default LoST server parameter. If the device is provided by or managed by service provider, it is expected that the service provider will configure this option. 8. Routing the call to the PSAP ED-50 Endpoints who obtain their own location SHOULD perform LoST mapping to the PSAP URI. ED-51 Mapping SHOULD be performed at boot time and whenever location changes beyond the service boundary obtained from a prior LoST mapping operation or the time-to-live value of that response has expired. The value MUST be cached for possible later use. ED-52 The endpoint MUST attempt to update its location at the time of an emergency call. If it cannot obtain a new location quickly (see Section 6), it MUST use the cached value. ED-53 The endpoint SHOULD attempt to update the LoST mapping at the time of an emergency call. If it cannot obtain a new mapping quickly, it MUST use the cached value if it has one. SP-24 Networks MUST be designed so that at least one proxy in the outbound path can recognize emergency calls with a Request URI of the service URN in the "sos" tree. An endpoint places a service URN in the Request URI to indicate that the endpoint understood the call was an emergency call. A proxy that processes such a call looks for the presence of a SIP Route header field with a URI of a PSAP. Absence of such a Route header indicates the UAC was unable to invoke LoST and the proxy MUST perform the LoST mapping and insert a Route header field with the URI obtained. SP-25 To deal with old user agents that predate this specification and with UAs that do not have access to their own location data, a proxy that recognizes a call as an emergency call that is not marked as such (see Section 5) MUST also perform this mapping, with the best location it has available for the endpoint. The resulting PSAP URI would be placed in a Route header with the service URN in the Request URI. Rosen & Polk Expires August 28, 2008 [Page 12] Internet-Draft Emergency Call Phone BCP February 2008 SP-26 Proxy servers performing mapping SHOULD use location obtained from the access network for the mapping. If no location is available, a default location (see Section 6.11) MUST be supplied. SP-27 A proxy server which attempts mapping and fails to get a mapping MUST provide a default mapping. A suitable default mapping would be the mapping obtained previously for the default location appropriate for the caller. ED-54/SP-28 [RFC3261] and [RFC3263] procedures MUST be used to route an emergency call towards the PSAP's URI. ED-55 Initial INVITES MUST provide an Offer [RFC3264]. 9. Signaling of emergency calls ED-56 Best Current Practice for SIP user agents [RFC4504] including handling of audio, video and real-time text [RFC4103] SHOULD be applied. This memo can be considered as an addition to [RFC4504] for endpoints. 9.1. Use of TLS ED-57/SP-29 TLS MUST be specified when attempting to signal an emergency call with SIP per [I-D.ietf-sip-sips]. IPSEC [RFC2401] is an acceptable alternative. ED-58/SP-30 If TLS session establishment fails, the call MUST be retried without TLS. ED-59/SP-31 [I-D.ietf-sip-outbound] is RECOMMENDED to maintain persistent TLS connections between elements. ED-60/AN-25 TLS MUST be specified when attempting to retrieve location (configuration or dereferencing) with HELD. The use of [RFC4507] is RECOMMENDED to minimise the time to establish TLS sessions. ED-61/AN-26 If TLS session establishment fails, the location retrieveal MUST be retried without TLS. 9.2. SIP signaling requirements for User Agents ED-62 The initial SIP signaling method is an INVITE request: 1. The Request URI SHOULD be the service URN in the "sos" tree, If the device cannot interpert local dial strings, the Request-URI SHOULD be a dial string URI [RFC4967] with the dialed digits. Rosen & Polk Expires August 28, 2008 [Page 13] Internet-Draft Emergency Call Phone BCP February 2008 2. The To header SHOULD be a service URN in the "sos" tree. If the device cannot do interpret local dial strings, the To: SHOULD be a dial string URI with the dialed digits. 3. The From header MUST be present and SHOULD be the AoR of the caller. 4. A Via header MUST be present. 5. A Route header SHOULD be present with a PSAP URI obtained from LoST (see Section 8) and the loose route parameter. If the device does not interpet dial plans, or was unable to obtain a route from a LoST serverr, no Route header will be present. 6. A Contact header MUST be present which MUST be globally routable, for example a GRUU [I-D.ietf-sip-gruu], to permit an immediate call-back to the specific device which placed the emergency call. 7. Other headers MAY be included as per normal SIP behavior. 8. A Supported header MUST be included with the 'geolocation' option tag [I-D.ietf-sip-location-conveyance], unless the device does not understand the concept of SIP location. 9. If a device understands the SIP location conveyance [I-D.ietf-sip-location-conveyance] extension and has its location available, it MUST include location either by-value, by-reference or both. 10. If a device understands the SIP Location Conveyance extension and has its location unavailable or unknown to that device, it MUST include a Supported header with a "geolocation" option tag, and MUST NOT include a Geolocation header, and not include a PIDF-LO message body. 11. If a device understands the SIP Location Conveyance extension and supports LoST [I-D.ietf-ecrit-lost], the Geolocation "used- for-routing" header parameter MUST be added to the corresponding URI in the Geolocation header. 12. A normal SDP offer SHOULD be included in the INVITE. If voice is supported the offer MUST include the G.711 codec, see Section 14. 13. If the device includes location-by-value, the UA MUST support multipart message bodies, since SDP will likely be also in the INVITE. 14. A UAC SHOULD include a "inserted-by=endpoint" header parameter on all Geolocation headers . This informs downstream elements which device entered the location at this URI (either cid-URL or location-by-reference URI). 15. SIP Caller Preferences [RFC3841] MAY be used to signal how the PSAP should handle the call. For example, a language preference expressed in an Accept-Language header may be used as a hint to cause the PSAP to route the call to a call taker who speaks the requested language. SIP Caller Preferences may also be used to indicate a need to invoke a relay service for communication with people with disabilities in the call. Rosen & Polk Expires August 28, 2008 [Page 14] Internet-Draft Emergency Call Phone BCP February 2008 9.3. SIP signaling requirements for proxy servers SP-32 SIP Proxy servers processing emergency calls: 1. If the proxy does interprets dial plans on behalf of user agents, the proxy MUST look for the local emergency dial string at the location of the end device and MAY look for the home dial string. If it finds it, the proxy MUST: * Insert a Geolocation header as above. Location-by-reference MUST be used because proxies must not insert bodies. * Include the Geolocation "inserted-by=server" and "used-for- routing" parameters. * Map the location to a PSAP URI using LoST. * Add a Route header with the PSAP URI. * Replace the Request-URI (which was the dial string) with the service URN appropriate for the emergency dial string. * Route the call using normal SIP routing mechanisms. 2. If the proxy recognizes the service URN in the Request URI, and does not find a Route header with a PSAP URI, it MUST run LoST routing. If a location was provided (which should be the case), the proxy uses that location to query LoST. The proxy may have to dereference a location by reference to get a value. If a location is not present, and the proxy can query a LIS which has the location of the UA it MUST do so. If no location is present, and the proxy does not have access to a LIS which could provide location, the proxy MUST supply a default location (See Section 6.11). The location (in the signaling, obtained from a LIS, or default) MUST be used in a query to LoST with the service URN received with the call. The resulting URI MUST be placed in a Route header added to the call. 3. The "inserted-by=" parameter in any Geolocation: header received on the call MUST NOT be modified or deleted in transit. 4. The proxy SHOULD NOT modify any parameters in Geolocation headers received in the call. It MAY add a Geolocation header. Such an additional location SHOULD NOT be used for routing; the location provided by the UA should be used. 5. Either a P-Asserted-Identity [RFC3325] or an Identity header [RFC4474], or both, MUST be included to identify the sender. 10. Call backs SP-33 Unitialized devices, like any device MUST have a globally routable URI in a Contact: header. SP-34 Unitialized devices SHOULD have a persistent URI in a P-Asserted-Identity: header if there is some way to assign such an identifier to the device. Rosen & Polk Expires August 28, 2008 [Page 15] Internet-Draft Emergency Call Phone BCP February 2008 11. Mid-call behavior ED-63/SP-35 During the course of an emergency call, devices and proxies MUST support REFER transactions and the Referred-by: header [RFC3515]. ED-64/SP-36 User agents and proxies MUST support Session Timer [RFC4028] to guard against session corruption. 12. Call termination ED-65 UACs with an active emergency call (i.e. SIP Dialog) MUST NOT generate a BYE request (or equivalent for other non-SIP signaling). The PSAP must be the only entity that can terminate a call. If the user "hangs up" an emergency call, the device should alert the user, and if the user responds by attempting to pick up the call, the device MUST reconnect the caller to the PSAP. ED-66 There can be a case where the session signaling path is lost, and the user agent does not receive the BYE. If the call is hung up, and the session timer (if implemented) expires, the call MAY be declared lost. If in the interval, an incoming call is received from the domain of the PSAP, the device MUST drop the old call and alert for the (new) incoming call. Dropping of the old call MUST only occur if the user is attempting to hang up; the domain of an incoming call can only be determined from the From header, which is not reliable, and could be spoofed. Dropping an active call by a new call with a spoofed From: would be a DoS attack. 13. Disabling of features ED-67/SP-37 User Agents and proxys MUST disable outgoing call features such as o Call Waiting o Call Transfer o Three Way Call o Flash hold o Outbound Call Blocking when an emergency call is established. Also see ED-72 in Section 14. ED-68/SP-38 The emergency dialstrings SHOULD NOT be permitted in Call Forward numbers or speed dial lists. ED-69/SP-39 The User Agent and Proxies SHOULD disable the following incoming call features on call backs from the PSAP: Rosen & Polk Expires August 28, 2008 [Page 16] Internet-Draft Emergency Call Phone BCP February 2008 o Call Waiting o Do Not Disturb o Call Forward (all kinds) ED-70 Call backs SHOULD be determined by retaining the domain of the PSAP which answers an outgoing emergency call and instantiating a timer which starts when the call is terminated. If a call is received from the same domain and within the timer period, sent to the Contact: or AoR used in the emergency call, it should be assumed to be a call back. The suggested timer period is 5 minutes. 14. Media ED-71 Endpoints MUST send and receive media streams on RTP [RFC3550]. ED-72 Normal SIP offer/answer [RFC3264] negotiations MUST be used to agree on the media streams to be used. ED-73 Endpoints supporting voice MUST support G.711 A law (and mu Law if they could be used in North America) encoded voice as described in [RFC3551]. It is desirable to include wideband codecs such as AMR-WB in the offer. ED-74 Silence suppression (Voice Activity Detection methods) MUST NOT be used on emergency calls. PSAP call takers sometimes get information on what is happening in the background to determine how to process the call. ED-75 Endpoints supporting IM MUST support both [RFC3428] and [RFC4975]. ED-76 Endpoints supporting real-time text MUST use [RFC4103]. The expectations for emergency service support for the real-time text medium, described in [I-D.ietf-sipping-toip], Section 7.1 SHOULD be fulfilled. ED-77 Endpoints supporting video MUST support H.264 per [RFC3984]. 15. Testing ED-78 INVITE requests to a service URN ending in ".test" indicates a request for an automated test. For example, "urn:service.sos.fire.test". As in standard SIP, a 200 (OK) response indicates that the address was recognized and a 404 (Not found) that it was not. A 486 (Busy Here) MUST be returned if the test service is busy, and a 488 (Not Acceptable Here) MUST be returned if the PSAP Rosen & Polk Expires August 28, 2008 [Page 17] Internet-Draft Emergency Call Phone BCP February 2008 does not support the test mechanism. ED-79 In its response to the test, the PSAP MAY include a text body (text/plain) indicating the identity of the PSAP, the requested service, and the location reported with the call. For the latter, the PSAP SHOULD return location-by-value even if the original location delivered with the test was by-reference. If the location- by-reference was supplied, and the dereference requires credentials, the PSAP SHOULD use credentials supplied by the LIS for test purposes. This alerts the LIS that the dereference is not for an actual emergency call and location hiding techniques, if they are being used, may be employed for this dereference. The response MAY include the connected identity of the PSAP per [I-D.ietf-sip-connected-identity]. ED-80 A PSAP accepting a test call SHOULD accept a media loopback test [I-D.ietf-mmusic-media-loopback] and SHOULD support the "rtp- pkt-loopback" and "rtp-start-loopback" options. The user agent would specify a loopback attribute of "loopback-source", the PSAP being the mirror. User Agents should expect the PSAP to loop back no more than 3 packets of each media type accepted (which limits the duration of the test), after which the PSAP would normally send BYE. ED-81 User agents SHOULD perform a full call test, including media loopback, after a disconnect and subsequent change in IP address not due to a reboot. After an initial test, a full test SHOULD be repeated approximately every 30 days with a random interval. ED-82 User agents MUST NOT place a test call immediately after booting. If the IP address changes after booting, the UA should wait a random amount of time (in perhaps a 30 minute period, sufficient for any avalanche restart to complete) and then test. ED-83 PSAPs MAY refuse repeated requests for test from the same device in a short period of time. Any refusal is signaled with a 486 or 488 response. 16. Security Considerations Security considerations for emergency calling have been documented in [I-D.ietf-ecrit-security-threats], and [I-D.barnes-geopriv-lo-sec]. 17. Acknowledgements Work group members participating in the creation and review of this document include include Hannes Tschofenig, Ted Hardie, Marc Linsner, Rosen & Polk Expires August 28, 2008 [Page 18] Internet-Draft Emergency Call Phone BCP February 2008 Roger Marshall, Stu Goldman, Shida Schubert, James Winterbottom, Barbara Stark, Richard Barnes and Peter Blatherwick. 18. Normative References [I-D.barnes-geopriv-lo-sec] Barnes, R., Lepinski, M., Tschofenig, H., and H. Schulzrinne, "Security Requirements for the Geopriv Location System", draft-barnes-geopriv-lo-sec-02 (work in progress), February 2008. [I-D.ietf-ecrit-dhc-lost-discovery] Schulzrinne, H., "A Dynamic Host Configuration Protocol (DHCP) based Location-to-Service Translation Protocol (LoST) Discovery Procedure", draft-ietf-ecrit-dhc-lost-discovery-02 (work in progress), July 2007. [I-D.ietf-ecrit-framework] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton, "Framework for Emergency Calling using Internet Multimedia", draft-ietf-ecrit-framework-04 (work in progress), November 2007. [I-D.ietf-ecrit-lost] Hardie, T., Newton, A., Schulzrinne, H., and H. Tschofenig, "LoST: A Location-to-Service Translation Protocol", draft-ietf-ecrit-lost-07 (work in progress), February 2008. [I-D.ietf-ecrit-requirements] Schulzrinne, H. and R. Marshall, "Requirements for Emergency Context Resolution with Internet Technologies", draft-ietf-ecrit-requirements-13 (work in progress), March 2007. [I-D.ietf-ecrit-security-threats] Taylor, T., "Security Threats and Requirements for Emergency Call Marking and Mapping", draft-ietf-ecrit-security-threats-05 (work in progress), August 2007. [I-D.ietf-ecrit-service-urn] Schulzrinne, H., "A Uniform Resource Name (URN) for Emergency and Other Well-Known Services", draft-ietf-ecrit-service-urn-07 (work in progress), August 2007. Rosen & Polk Expires August 28, 2008 [Page 19] Internet-Draft Emergency Call Phone BCP February 2008 [I-D.ietf-geopriv-http-location-delivery] Barnes, M., Winterbottom, J., Thomson, M., and B. Stark, "HTTP Enabled Location Delivery (HELD)", draft-ietf-geopriv-http-location-delivery-05 (work in progress), February 2008. [I-D.ietf-geopriv-pdif-lo-profile] Winterbottom, J., Thomson, M., and H. Tschofenig, "GEOPRIV PIDF-LO Usage Clarification, Considerations and Recommendations", draft-ietf-geopriv-pdif-lo-profile-11 (work in progress), February 2008. [I-D.ietf-mmusic-ice] Rosenberg, J., "Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols", draft-ietf-mmusic-ice-19 (work in progress), October 2007. [I-D.ietf-mmusic-media-loopback] Hedayat, K., "An Extension to the Session Description Protocol (SDP) for Media Loopback", draft-ietf-mmusic-media-loopback-07 (work in progress), November 2007. [I-D.ietf-sip-connected-identity] Elwell, J., "Connected Identity in the Session Initiation Protocol (SIP)", draft-ietf-sip-connected-identity-05 (work in progress), February 2007. [I-D.ietf-sip-gruu] Rosenberg, J., "Obtaining and Using Globally Routable User Agent (UA) URIs (GRUU) in the Session Initiation Protocol (SIP)", draft-ietf-sip-gruu-15 (work in progress), October 2007. [I-D.ietf-sip-location-conveyance] Polk, J. and B. Rosen, "Location Conveyance for the Session Initiation Protocol", draft-ietf-sip-location-conveyance-09 (work in progress), November 2007. [I-D.ietf-sip-outbound] Jennings, C. and R. Mahy, "Managing Client Initiated Connections in the Session Initiation Protocol (SIP)", draft-ietf-sip-outbound-11 (work in progress), November 2007. [I-D.ietf-sip-sips] Rosen & Polk Expires August 28, 2008 [Page 20] Internet-Draft Emergency Call Phone BCP February 2008 Audet, F., "The use of the SIPS URI Scheme in the Session Initiation Protocol (SIP)", draft-ietf-sip-sips-08 (work in progress), February 2008. [I-D.ietf-sipping-config-framework] Channabasappa, S., "A Framework for Session Initiation Protocol User Agent Profile Delivery", draft-ietf-sipping-config-framework-15 (work in progress), February 2008. [I-D.ietf-sipping-toip] Wijk, A. and G. Gybels, "Framework for real-time text over IP using the Session Initiation Protocol (SIP)", draft-ietf-sipping-toip-08 (work in progress), October 2007. [I-D.thomson-geopriv-lis-discovery] Thomson, M. and J. Winterbottom, "Discovering the Local Location Information Server (LIS)", draft-thomson-geopriv-lis-discovery-03 (work in progress), September 2007. [LLDP] IEEE, "IEEE802.1ab Station and Media Access Control", Dec 2004. [LLDP-MED] TIA, "ANSI/TIA-1057 Link Layer Discovery Protocol - Media Endpoint Discovery". [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the Internet Protocol", RFC 2401, November 1998. [RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046, January 2001. [RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", RFC 3118, June 2001. Rosen & Polk Expires August 28, 2008 [Page 21] Internet-Draft Emergency Call Phone BCP February 2008 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol (SIP): Locating SIP Servers", RFC 3263, June 2002. [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, June 2002. [RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific Event Notification", RFC 3265, June 2002. [RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks", RFC 3325, November 2002. [RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., and D. Gurle, "Session Initiation Protocol (SIP) Extension for Instant Messaging", RFC 3428, December 2002. [RFC3515] Sparks, R., "The Session Initiation Protocol (SIP) Refer Method", RFC 3515, April 2003. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. [RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video Conferences with Minimal Control", STD 65, RFC 3551, July 2003. [RFC3825] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host Configuration Protocol Option for Coordinate-based Location Configuration Information", RFC 3825, July 2004. [RFC3841] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Caller Preferences for the Session Initiation Protocol (SIP)", RFC 3841, August 2004. [RFC3856] Rosenberg, J., "A Presence Event Package for the Session Initiation Protocol (SIP)", RFC 3856, August 2004. [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers", Rosen & Polk Expires August 28, 2008 [Page 22] Internet-Draft Emergency Call Phone BCP February 2008 RFC 3966, December 2004. [RFC3984] Wenger, S., Hannuksela, M., Stockhammer, T., Westerlund, M., and D. Singer, "RTP Payload Format for H.264 Video", RFC 3984, February 2005. [RFC4028] Donovan, S. and J. Rosenberg, "Session Timers in the Session Initiation Protocol (SIP)", RFC 4028, April 2005. [RFC4103] Hellstrom, G. and P. Jones, "RTP Payload for Text Conversation", RFC 4103, June 2005. [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object Format", RFC 4119, December 2005. [RFC4190] Carlberg, K., Brown, I., and C. Beard, "Framework for Supporting Emergency Telecommunications Service (ETS) in IP Telephony", RFC 4190, November 2005. [RFC4474] Peterson, J. and C. Jennings, "Enhancements for Authenticated Identity Management in the Session Initiation Protocol (SIP)", RFC 4474, August 2006. [RFC4504] Sinnreich, H., Lass, S., and C. Stredicke, "SIP Telephony Device Requirements and Configuration", RFC 4504, May 2006. [RFC4507] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, "Transport Layer Security (TLS) Session Resumption without Server-Side State", RFC 4507, May 2006. [RFC4676] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information", RFC 4676, October 2006. [RFC4967] Rosen, B., "Dial String Parameter for the Session Initiation Protocol Uniform Resource Identifier", RFC 4967, July 2007. [RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message Session Relay Protocol (MSRP)", RFC 4975, September 2007. [RFC5139] Thomson, M. and J. Winterbottom, "Revised Civic Location Format for Presence Information Data Format Location Object (PIDF-LO)", RFC 5139, February 2008. Rosen & Polk Expires August 28, 2008 [Page 23] Internet-Draft Emergency Call Phone BCP February 2008 Appendix A. BCP Requirements Sorted by Responsible Party A.1. Requirements of End Devices ED-1 A device or application SHOULD support emergency calling if a user could reasonably expect to be able to place a call for help with the device. ED-2 Devices that create media sessions and exchange audio, video and/or text, and have the capability to establish sessions to a wide variety of addresses, and communicate over private IP networks or the Internet, SHOULD support emergency calls. ED-3 Endpoints SHOULD recognize dial strings of emergency calls. If the service provider always knows the location of the device, then the service provider could recognize them. ED-4 Emergency calls MUST be marked with a Service URN in the Request-URI of the INVITE. ED-5 Local dial strings MUST be recognized. ED-6 Home dial strings MAY be recognized. ED-7 Local emergency dial strings SHOULD be determined from LoST [I-D.ietf-ecrit-lost]. ED-8 Endpoints which do not recognize emergency dial strings SHOULD send dial strings as per [RFC4967]. ED-9 Endpoints SHOULD be able to have home dial strings provisioned by configuration. ED-10 Devices SHOULD NOT have one button emergency calling initiation. ED-11 All emergency services specified in [I-D.ietf-ecrit-service-urn] MUST be recognized. ED-12 Endpoints, Intermediate Devices and Service Providers MUST be prepared to handle location represented in either civic or geo form. ED-13 Elements MUST NOT convert (civic to geo or geo to civic) from the form of location the determination mechanism supplied. ED-14 Any suitable location determination mechanism MAY be used. ED-15 Devices, intermediate Devices and/or access networks SHOULD Rosen & Polk Expires August 28, 2008 [Page 24] Internet-Draft Emergency Call Phone BCP February 2008 support a manual method to "override" the location the access network determines. Where a civic form of location is provided, all fields in the PIDF-LO [RFC4119] and [RFC5139] MUST be able to be specified. ED-16 Devices MAY support end-system measured location. Uncertainty of less than 100 m with 95% confidence SHOULD be available for dispatch. ED-17 Devices that support endpoint measuring of location MUST have at least a coarse location capability (typically <1km accuracy when not location hiding) at all times for routing of calls. This mechanism MAY be a service provided by the access network. ED-18 Endpoints SHOULD do configure their own location. ED-19 Where proxies provide location on behalf of endpoints, the the service provider MUST ensure that either the end device is provided with the local dial strings for its current location (where the end device recognizes dial strings), or the service provider proxy MUST detect the appropriate local dial strings at the time of the call. ED-20 Devices SHOULD be able to accept and forward location by value or by reference. An end device that receives location by reference (and does not also get the corresponding value) MUST be able to perform a dereference operation to obtain a value. ED-21 Devices MUST support all of: DHCP location options [RFC4676] and [RFC3825], HELD [I-D.ietf-geopriv-http-location-delivery] and LLDP-MED [LLDP-MED]. ED-22 Endpoints SHOULD try all LCPs supported by the device in any order or in parallel. The first one that succeeds in supplying location can be used. ED-23 When HELD is the LCP, the request MUST specify a value of "emergencyRouting" for the "responseTime" parameter and use the resulting location for routing. If a value for dispatch location will be sent, another request with the "responseTime" parameter set to "emergencyDispatch" must be completed, with the result sent for dispatch purposes. ED-24 Where the operating system supporting application programs which need location for emergency calls does not allow access to Layer 2 and Layer 3 functions necessary for a client application to use DHCP location options and/or LLDP-MED, the operating system MUST provide a published API conforming to ED-12 through ED-18 and ED-21 through ED-27. It is RECOMMENDED that all operating systems provide such an API. Rosen & Polk Expires August 28, 2008 [Page 25] Internet-Draft Emergency Call Phone BCP February 2008 ED-25 Endpoints SHOULD obtain location immediately after obtaining local network configuration information.When HELD is the LCP the client MUST support a random back-off period (between 30 seconds and 300 seconds) for re-trying the HELD query, when no response is received. ED-26 If the device is configured to use DHCP for bootstrapping, it MUST include both options for location acquisition (civic and geodetic), the option for LIS discovery, and the option for LoST discovery as defined in [RFC4676], [RFC3825], [I-D.thomson-geopriv-lis-discovery] and [I-D.ietf-ecrit-dhc-lost-discovery]. ED-27 If the device sends a DHCP INFORM message, it MUST include both options for location acquisition (civic and geodetic), the option for LIS discovery, and the option for LoST discovery as defined in [RFC4676], [RFC3825], [I-D.thomson-geopriv-lis-discovery] and [I-D.ietf-ecrit-dhc-lost-discovery]. ED-28 To minimize the effects of VPNs that do not allow split tunneling VPNs, location configuration SHOULD be attempted before such tunnels are established. ED-29 Software which uses LCPs SHOULD locate and use the actual hardware network interface rather than a VPN tunnel interface to direct LCP requests to the LIS in the actual access network. ED-30 For devices which are not expected to roam, refreshing location on the order of once per day is RECOMMENDED. ED-31 For devices which roam, refresh of location information SHOULD be more frequent, with the frequency related to the mobility of the device and the ability of the access network to support the refresh operation. If the device can detect that it has moved, for example when it changes access points, the device SHOULD refresh its location. ED-32 It is RECOMMENDED that location determination not take longer than 250 ms to obtain routing location and systems SHOULD be designed such that the typical response is under 100 ms. However, as much as 3 seconds to obtain routing location MAY be tolerated if location accuracy can be substantially improved over what can be obtained in 250 ms. ED-33 Location sent between SIP elements MUST be conveyed using [I-D.ietf-sip-location-conveyance]. ED-34 Where the absolute location or the accuracy of location of the Rosen & Polk Expires August 28, 2008 [Page 26] Internet-Draft Emergency Call Phone BCP February 2008 endpoint may change between the time the call is received at the PSAP and the time dispatch is completed, location update mechanisms MUST be provided. ED-35 Mobile devices MUST be provided with a mechanism to get repeated location updates to track the motion of the device during the complete processing of the call. ED-36 The LIS SHOULD provide a location reference which permits a subscription with appropriate filtering. ED-37 For calls sent with location-by-reference, with a SIP or SIPS scheme, the server resolving the reference MUST support a SUBSCRIBE [RFC3265] to the presence event [RFC3856]. For other location-by- reference schemes, the PSAP will have to repeatedly dereference the URI to determine if the device moved. ED-38 If location was sent by value, and the endpoint gets updated location, it MUST send the updated location to the PSAP via a SIP re- INVITE or UPDATE request. Such updates SHOULD be limited to no more than one update every 10 seconds. ED-39 If a UA has more than one location available to it, it MUST choose one location to route the call towards the PSAP. ED-40 Location objects MUST contain information about the method by which the location was determined, such as GPS, manually entered, or based on access network topology included in a PIDF- LO "method" element. In addition, the source of the location information MUST be included in a PIDF-LO "provided-by" element. ED-41 The "used-for-routing" parameter MUST be set to the location that was used to query LoST. ED-42 Endpoints SHOULD validate civic locations when they receive them from their LCP. Validation SHOULD be performed in conjunction with the LoST route query to minimize load on the LoST server. ED-43 If the LCP does not return location in the form of a PIDF-LO [RFC4119], the endpoint MUST map the location information it receives from the configuration protocol to a PIDF-LO. ED-44 To prevent against spoofing of the DHCP server, elements implementing DHCP for location configuration SHOULD use although the difficulty in providing appropriate credentials is significant. [RFC3118]. ED-45 S/MIME MUST NOT be used to encrypt the SIP Geolocation header Rosen & Polk Expires August 28, 2008 [Page 27] Internet-Draft Emergency Call Phone BCP February 2008 or bodies. ED-46 TLS MUST be used to protect location (but see Section 9.1). IPSEC [RFC2401] is an acceptable alternative. ED-47 Endpoints MUST support one or more mechanisms that allow them to determine their public IP address. Examples include ICE [I-D.ietf-mmusic-ice] and HTTP get. ED-48 Endpoints MUST support LIS discovery as described in [I-D.thomson-geopriv-lis-discovery], and the LoST discovery as described in [I-D.ietf-ecrit-dhc-lost-discovery]. ED-49 The device MUST have a configurable default LoST server parameter. If the device is provided by or managed by service provider, it is expected that the service provider will configure this option. ED-50 Endpoints who obtain their own location SHOULD perform LoST mapping to the PSAP URI. ED-51 Mapping SHOULD be performed at boot time and whenever location changes beyond the service boundary obtained from a prior LoST mapping operation or the time-to-live value of that response has expired. The value MUST be cached for possible later use. ED-52 The endpoint MUST attempt to update its location at the time of an emergency call. If it cannot obtain a new location quickly (see Section 6), it MUST use the cached value. ED-53 The endpoint SHOULD attempt to update the LoST mapping at the time of an emergency call. If it cannot obtain a new mapping quickly, it MUST use the cached value if it has one. ED-54 [RFC3261] and [RFC3263] procedures MUST be used to route an emergency call towards the PSAP's URI. ED-55 Initial INVITES MUST provide an Offer [RFC3264]. ED-56 Best Current Practice for SIP user agents [RFC4504] including handling of audio, video and real-time text [RFC4103] SHOULD be applied. This memo can be considered as an addition to [RFC4504] for endpoints. ED-57 TLS MUST be specified when attempting to signal an emergency call with SIP per [I-D.ietf-sip-sips]. IPSEC [RFC2401] is an acceptable alternative. Rosen & Polk Expires August 28, 2008 [Page 28] Internet-Draft Emergency Call Phone BCP February 2008 ED-58 If TLS session establishment fails, the call MUST be retried without TLS. ED-59 [I-D.ietf-sip-outbound] is RECOMMENDED to maintain persistent TLS connections between elements. ED-60 TLS MUST be specified when attempting to retrieve location (configuration or dereferencing) with HELD. The use of [RFC4507] is RECOMMENDED to minimise the time to establish TLS sessions. ED-61 If TLS session establishment fails, the location retrieveal MUST be retried without TLS. ED-62 The initial SIP signaling method is an INVITE request: 1. The Request URI SHOULD be the service URN in the "sos" tree, If the device cannot interpert local dial strings, the Request-URI SHOULD be a dial string URI [RFC4967] with the dialed digits. 2. The To header SHOULD be a service URN in the "sos" tree. If the device cannot do interpret local dial strings, the To: SHOULD be a dial string URI with the dialed digits. 3. The From header MUST be present and SHOULD be the AoR of the caller. 4. A Via header MUST be present. 5. A Route header SHOULD be present with a PSAP URI obtained from LoST (see Section 8) and the loose route parameter. If the device does not interpet dial plans, or was unable to obtain a route from a LoST serverr, no Route header will be present. 6. A Contact header MUST be present which MUST be globally routable, for example a GRUU [I-D.ietf-sip-gruu], to permit an immediate call-back to the specific device which placed the emergency call. 7. Other headers MAY be included as per normal SIP behavior. 8. A Supported header MUST be included with the 'geolocation' option tag [I-D.ietf-sip-location-conveyance], unless the device does not understand the concept of SIP location. 9. If a device understands the SIP location conveyance [I-D.ietf-sip-location-conveyance] extension and has its location available, it MUST include location either by-value, by-reference or both. 10. If a device understands the SIP Location Conveyance extension and has its location unavailable or unknown to that device, it MUST include a Supported header with a "geolocation" option tag, and MUST NOT include a Geolocation header, and not include a PIDF-LO message body. 11. If a device understands the SIP Location Conveyance extension and supports LoST [I-D.ietf-ecrit-lost], the Geolocation "used- for-routing" header parameter MUST be added to the corresponding URI in the Geolocation header. Rosen & Polk Expires August 28, 2008 [Page 29] Internet-Draft Emergency Call Phone BCP February 2008 12. A normal SDP offer SHOULD be included in the INVITE. If voice is supported the offer MUST include the G.711 codec, see Section 14. 13. If the device includes location-by-value, the UA MUST support multipart message bodies, since SDP will likely be also in the INVITE. 14. A UAC SHOULD include a "inserted-by=endpoint" header parameter on all Geolocation headers . This informs downstream elements which device entered the location at this URI (either cid-URL or location-by-reference URI). 15. SIP Caller Preferences [RFC3841] MAY be used to signal how the PSAP should handle the call. For example, a language preference expressed in an Accept-Language header may be used as a hint to cause the PSAP to route the call to a call taker who speaks the requested language. SIP Caller Preferences may also be used to indicate a need to invoke a relay service for communication with people with disabilities in the call. ED-63 During the course of an emergency call, devices and proxies MUST support REFER transactions and the Referred-by: header [RFC3515]. ED-64 User agents and proxies MUST support Session Timer [RFC4028] to guard against session corruption. ED-65 UACs with an active emergency call (i.e. SIP Dialog) MUST NOT generate a BYE request (or equivalent for other non-SIP signaling). The PSAP must be the only entity that can terminate a call. If the user "hangs up" an emergency call, the device should alert the user, and if the user responds by attempting to pick up the call, the device MUST reconnect the caller to the PSAP. ED-66 There can be a case where the session signaling path is lost, and the user agent does not receive the BYE. If the call is hung up, and the session timer (if implemented) expires, the call MAY be declared lost. If in the interval, an incoming call is received from the domain of the PSAP, the device MUST drop the old call and alert for the (new) incoming call. Dropping of the old call MUST only occur if the user is attempting to hang up; the domain of an incoming call can only be determined from the From header, which is not reliable, and could be spoofed. Dropping an active call by a new call with a spoofed From: would be a DoS attack. ED-67 User Agents and proxys MUST disable outgoing call features such as o Call Waiting Rosen & Polk Expires August 28, 2008 [Page 30] Internet-Draft Emergency Call Phone BCP February 2008 o Call Transfer o Three Way Call o Flash hold o Outbound Call Blocking when an emergency call is established. Also see ED-72 in Section 14. ED-68 The emergency dialstrings SHOULD NOT be permitted in Call Forward numbers or speed dial lists. ED-69 The User Agent and Proxies SHOULD disable the following incoming call features on call backs from the PSAP: o Call Waiting o Do Not Disturb o Call Forward (all kinds) ED-70 Call backs SHOULD be determined by retaining the domain of the PSAP which answers an outgoing emergency call and instantiating a timer which starts when the call is terminated. If a call is received from the same domain and within the timer period, sent to the Contact: or AoR used in the emergency call, it should be assumed to be a call back. The suggested timer period is 5 minutes. ED-71 Endpoints MUST send and receive media streams on RTP [RFC3550]. ED-72 Normal SIP offer/answer [RFC3264] negotiations MUST be used to agree on the media streams to be used. ED-73 Endpoints supporting voice MUST support G.711 A law (and mu Law if they could be used in North America) encoded voice as described in [RFC3551]. It is desirable to include wideband codecs such as AMR-WB in the offer. ED-74 Silence suppression (Voice Activity Detection methods) MUST NOT be used on emergency calls. PSAP call takers sometimes get information on what is happening in the background to determine how to process the call. ED-75 Endpoints supporting IM MUST support both [RFC3428] and [RFC4975]. ED-76 Endpoints supporting real-time text MUST use [RFC4103]. The expectations for emergency service support for the real-time text medium, described in [I-D.ietf-sipping-toip], Section 7.1 SHOULD be fulfilled. ED-77 Endpoints supporting video MUST support H.264 per [RFC3984]. ED-78 INVITE requests to a service URN ending in ".test" indicates a Rosen & Polk Expires August 28, 2008 [Page 31] Internet-Draft Emergency Call Phone BCP February 2008 request for an automated test. For example, "urn:service.sos.fire.test". As in standard SIP, a 200 (OK) response indicates that the address was recognized and a 404 (Not found) that it was not. A 486 (Busy Here) MUST be returned if the test service is busy, and a 488 (Not Acceptable Here) MUST be returned if the PSAP does not support the test mechanism. ED-79 In its response to the test, the PSAP MAY include a text body (text/plain) indicating the identity of the PSAP, the requested service, and the location reported with the call. For the latter, the PSAP SHOULD return location-by-value even if the original location delivered with the test was by-reference. If the location- by-reference was supplied, and the dereference requires credentials, the PSAP SHOULD use credentials supplied by the LIS for test purposes. This alerts the LIS that the dereference is not for an actual emergency call and location hiding techniques, if they are being used, may be employed for this dereference. The response MAY include the connected identity of the PSAP per [I-D.ietf-sip-connected-identity]. ED-80 A PSAP accepting a test call SHOULD accept a media loopback test [I-D.ietf-mmusic-media-loopback] and SHOULD support the "rtp- pkt-loopback" and "rtp-start-loopback" options. The user agent would specify a loopback attribute of "loopback-source", the PSAP being the mirror. User Agents should expect the PSAP to loop back no more than 3 packets of each media type accepted (which limits the duration of the test), after which the PSAP would normally send BYE. ED-81 User agents SHOULD perform a full call test, including media loopback, after a disconnect and subsequent change in IP address not due to a reboot. After an initial test, a full test SHOULD be repeated approximately every 30 days with a random interval. ED-82 User agents MUST NOT place a test call immediately after booting. If the IP address changes after booting, the UA should wait a random amount of time (in perhaps a 30 minute period, sufficient for any avalanche restart to complete) and then test. ED-83 PSAPs MAY refuse repeated requests for test from the same device in a short period of time. Any refusal is signaled with a 486 or 488 response. A.2. Requirements of Service Providers SP-1 If a device or application expects to be able to place a call for help, the service provider that supports it MUST facilitate emergency calling. Rosen & Polk Expires August 28, 2008 [Page 32] Internet-Draft Emergency Call Phone BCP February 2008 SP-2 Proxy servers SHOULD recognize emergency dial string if for some reason the endpoint does not recognize them. This cannot be relied upon by the device if the service provider cannot always determine the location of the device. SP-3 Emergency calls MUST be marked with a Service URN in the Request-URI of the INVITE. SP-4 Local dial strings MUST be recognized. SP-5 Home dial strings MAY be recognized. SP-6 Local emergency dial strings SHOULD be determined from LoST [I-D.ietf-ecrit-lost]. SP-7 Proxy Servers MUST recognize emergency dial strings represented by [RFC4967] and SHOULD recognize emergency dial strings represented by a tel URI [RFC3966]. SP-8 Service providers MAY provide home dial strings by configuration [I-D.ietf-sipping-config-framework]. SP-9 All emergency services specified in [I-D.ietf-ecrit-service-urn] MUST be recognized. SP-10 Endpoints, Intermediate Devices and Service Providers MUST be prepared to handle location represented in either civic or geo form. SP-11 Elements MUST NOT convert (civic to geo or geo to civic) from the form of location the determination mechanism supplied. SP-12 Proxies MAY provide location on behalf of devices if: o The proxy has a relationship with all access networks the device could connect to, and the relationship allows it to obtain location. o The proxy has an identifier, such as an IP address, that can be used by the access network to determine the location of the endpoint, even in the presence of NAT and VPN tunnels that may obscure the identifier between the access network and the service provider. SP-13 Where proxies provide location on behalf of endpoints, the the service provider MUST ensure that either the end device is provided with the local dial strings for its current location (where the end device recognizes dial strings), or the service provider proxy MUST detect the appropriate local dial strings at the time of the call. SP-14 When HELD is the LCP, the request MUST specify a value of Rosen & Polk Expires August 28, 2008 [Page 33] Internet-Draft Emergency Call Phone BCP February 2008 "emergencyRouting" for the "responseTime" parameter and use the resulting location for routing. If a value for dispatch location will be sent, another request with the "responseTime" parameter set to "emergencyDispatch" must be completed, with the result sent for dispatch purposes. SP-15 Location sent between SIP elements MUST be conveyed using [I-D.ietf-sip-location-conveyance]. SP-16 If a proxy inserts location on behalf of an endpoint, and it has multiple locations available for the endpoint it MUST choose one location to use to route the call towards the PSAP. SP-17 If a proxy is attempting to insert location but the UA conveyed a location to it, the proxy MUST use the UA's location for routing and MUST convey that location towards the PSAP. It MAY also include what it believes the location to be in a separate Geolocation header. SP-18 All location objects received by a proxy MUST be delivered to the PSAP. SP-19 Location objects MUST contain information about the method by which the location was determined, such as GPS, manually entered, or based on access network topology included in a PIDF- LO "method" element. In addition, the source of the location information MUST be included in a PIDF-LO "provided-by" element. SP-20 The "used-for-routing" parameter MUST be set to the location that was used to query LoST. SP-21 Proxies handling emergency calls MUST insert a default location if the call does not contain a location and the proxy does not have a method for obtaining a better location. SP-22 Default locations MUST be marked with method=Default and the proxy MUST be identfied in provided-by element of the PIDF-LO. SP-23 TLS MUST be used to protect location (but see Section 9.1). IPSEC [RFC2401] is an acceptable alternative. SP-24 Networks MUST be designed so that at least one proxy in the outbound path can recognize emergency calls with a Request URI of the service URN in the "sos" tree. An endpoint places a service URN in the Request URI to indicate that the endpoint understood the call was an emergency call. A proxy that processes such a call looks for the presence of a SIP Route header field with a URI of a PSAP. Absence of such a Route header indicates the UAC was unable to invoke LoST and the proxy MUST perform the LoST mapping and insert a Route header Rosen & Polk Expires August 28, 2008 [Page 34] Internet-Draft Emergency Call Phone BCP February 2008 field with the URI obtained. SP-25 To deal with old user agents that predate this specification and with UAs that do not have access to their own location data, a proxy that recognizes a call as an emergency call that is not marked as such (see Section 5) MUST also perform this mapping, with the best location it has available for the endpoint. The resulting PSAP URI would be placed in a Route header with the service URN in the Request URI. SP-26 Proxy servers performing mapping SHOULD use location obtained from the access network for the mapping. If no location is available, a default location (see Section 6.11) MUST be supplied. SP-27 A proxy server which attempts mapping and fails to get a mapping MUST provide a default mapping. A suitable default mapping would be the mapping obtained previously for the default location appropriate for the caller. SP-28 [RFC3261] and [RFC3263] procedures MUST be used to route an emergency call towards the PSAP's URI. SP-29 TLS MUST be specified when attempting to signal an emergency call with SIP per [I-D.ietf-sip-sips]. IPSEC [RFC2401] is an acceptable alternative. SP-30 If TLS session establishment fails, the call MUST be retried without TLS. SP-31 [I-D.ietf-sip-outbound] is RECOMMENDED to maintain persistent TLS connections between elements. SP-32 SIP Proxy servers processing emergency calls: 1. If the proxy does interprets dial plans on behalf of user agents, the proxy MUST look for the local emergency dial string at the location of the end device and MAY look for the home dial string. If it finds it, the proxy MUST: * Insert a Geolocation header as above. Location-by-reference MUST be used because proxies must not insert bodies. * Include the Geolocation "inserted-by=server" and "used-for- routing" parameters. * Map the location to a PSAP URI using LoST. * Add a Route header with the PSAP URI. * Replace the Request-URI (which was the dial string) with the service URN appropriate for the emergency dial string. * Route the call using normal SIP routing mechanisms. Rosen & Polk Expires August 28, 2008 [Page 35] Internet-Draft Emergency Call Phone BCP February 2008 2. If the proxy recognizes the service URN in the Request URI, and does not find a Route header with a PSAP URI, it MUST run LoST routing. If a location was provided (which should be the case), the proxy uses that location to query LoST. The proxy may have to dereference a location by reference to get a value. If a location is not present, and the proxy can query a LIS which has the location of the UA it MUST do so. If no location is present, and the proxy does not have access to a LIS which could provide location, the proxy MUST supply a default location (See Section 6.11). The location (in the signaling, obtained from a LIS, or default) MUST be used in a query to LoST with the service URN received with the call. The resulting URI MUST be placed in a Route header added to the call. 3. The "inserted-by=" parameter in any Geolocation: header received on the call MUST NOT be modified or deleted in transit. 4. The proxy SHOULD NOT modify any parameters in Geolocation headers received in the call. It MAY add a Geolocation header. Such an additional location SHOULD NOT be used for routing; the location provided by the UA should be used. 5. Either a P-Asserted-Identity [RFC3325] or an Identity header [RFC4474], or both, MUST be included to identify the sender. SP-33 Unitialized devices, like any device MUST have a globally routable URI in a Contact: header. SP-34 Unitialized devices SHOULD have a persistent URI in a P-Asserted-Identity: header if there is some way to assign such an identifier to the device. SP-35 During the course of an emergency call, devices and proxies MUST support REFER transactions and the Referred-by: header [RFC3515]. SP-36 User agents and proxies MUST support Session Timer [RFC4028] to guard against session corruption. SP-37 User Agents and proxys MUST disable outgoing call features such as o Call Waiting o Call Transfer o Three Way Call o Flash hold o Outbound Call Blocking when an emergency call is established. Also see ED-72 in Section 14. SP-38 The emergency dialstrings SHOULD NOT be permitted in Call Forward numbers or speed dial lists. Rosen & Polk Expires August 28, 2008 [Page 36] Internet-Draft Emergency Call Phone BCP February 2008 SP-39 The User Agent and Proxies SHOULD disable the following incoming call features on call backs from the PSAP: o Call Waiting o Do Not Disturb o Call Forward (all kinds) A.3. Requirements of Access Network AN-1 Elements MUST NOT convert (civic to geo or geo to civic) from the form of location the determination mechanism supplied. AN-2 Any suitable location determination mechanism MAY be used. AN-3 Devices, intermediate Devices and/or access networks SHOULD support a manual method to "override" the location the access network determines. Where a civic form of location is provided, all fields in the PIDF-LO [RFC4119] and [RFC5139] MUST be able to be specified. AN-4 Access networks supporting copper, fiber or other hard wired IP packet service SHOULD support location configuration. If the network does not support location configuration, it MUST require every device that connects to the network to support end system measured location. AN-5 Access networks and intermediate devices providing wire database location information SHOULD provide interior location data (building, floor, room, cubicle) where possible. It is RECOMMENDED that interior location be provided when spaces exceed approximately 650 square meters. AN-6 Access networks and intermediate devices (including enterprise networks) which support intermediate range wireless connections (typically 100m or less of range) and which do not support a more accurate location determination mechanism such as triangulation, MUST support location configuration where the location of the access point is reflected as the location of the clients of that access point. Where the access network provides location configuration, intermediate devices MUST either be transparent to it, or provide an interconnected client for the supported configuration mechanism and a server for a configuration protocol supported by end devices upstream of the intermediate device AN-7 Devices that support endpoint measuring of location MUST have at least a coarse location capability (typically <1km accuracy when not location hiding) at all times for routing of calls. This mechanism MAY be a service provided by the access network. AN-8 Access networks MAY provide network-measured location determination. Wireless access network which do not support network Rosen & Polk Expires August 28, 2008 [Page 37] Internet-Draft Emergency Call Phone BCP February 2008 measured location MUST require that all devices connected to the network have end-system measured location. Uncertainty of less than 100 m with 95% confidence SHOULD be available for dispatch. AN-9 Access networks that provide network measured location MUST have at least a coarse location (typically <1km when not location hiding) capability at all times for routing of calls. AN-10 Access networks with range of <10 meters MUST provide a location to mobile devices connected to it. The location provided SHOULD be that of the access point location unless a more accurate mechanism is provided. AN-11 The access network MUST support at least one of: DHCP location options, HELD or LLDP-MED. AN-12 Where a router is employed between a LAN and WAN in a small (less than approximately 650 square meters) area, the router MUST be transparent to the location provided by the WAN to the LAN. This may mean the router must obtain location as a client from the WAN, and supply an LCP server to the LAN with the location it obtains. Where the area is larger, the LAN MUST have a location configuration mechanism meeting this BCP. AN-13 Access networks that support more than one LCP MUST reply with the same location information (within the limits of the data format for the specific LCP) for all LCPs it supports. AN-14 Network administrators MUST take care in assigning IP addresses such that VPN address assignments can be distinguished from local devices (by subnet choice, for example), and LISs SHOULD NOT attempt to provide location to addresses that arrive via VPN connections unless it can accurately determine the location for such addresses. AN-15 Placement of NAT devices where an LCP uses IP address for an identifier SHOULD consider the effect of the NAT on the LCP. The address used to query the LIS MUST be able to correctly identify the record in the LIS representing the location of the querying device AN-16 It is RECOMMENDED that location determination not take longer than 250 ms to obtain routing location and systems SHOULD be designed such that the typical response is under 100 ms. However, as much as 3 seconds to obtain routing location MAY be tolerated if location accuracy can be substantially improved over what can be obtained in 250 ms. AN-17 Where the absolute location or the accuracy of location of the endpoint may change between the time the call is received at the PSAP Rosen & Polk Expires August 28, 2008 [Page 38] Internet-Draft Emergency Call Phone BCP February 2008 and the time dispatch is completed, location update mechanisms MUST be provided. AN-18 Mobile devices MUST be provided with a mechanism to get repeated location updates to track the motion of the device during the complete processing of the call. AN-19 The LIS SHOULD provide a location reference which permits a subscription with appropriate filtering. AN-20 For calls sent with location-by-reference, with a SIP or SIPS scheme, the server resolving the reference MUST support a SUBSCRIBE [RFC3265] to the presence event [RFC3856]. For other location-by- reference schemes, the PSAP will have to repeatedly dereference the URI to determine if the device moved. AN-21 A LIS should perform location validation of civic locations via LoST before entering a location in its database. AN-22 When the access network cannot determine the actual location of the caller, it MUST supply a default location. The default SHOULD be chosen to be as close to the probable location of the device as the network can determine. See [I-D.ietf-ecrit-framework] AN-23 Default locations MUST be marked with method=Default and the proxy MUST be identfied in provided-by element of the PIDF-LO. AN-24 To prevent against spoofing of the DHCP server, elements implementing DHCP for location configuration SHOULD use although the difficulty in providing appropriate credentials is significant. [RFC3118]. AN-25 TLS MUST be specified when attempting to retrieve location (configuration or dereferencing) with HELD. The use of [RFC4507] is RECOMMENDED to minimise the time to establish TLS sessions. AN-26 If TLS session establishment fails, the location retrieveal MUST be retried without TLS. A.4. Requirements of Intermediate Devices INT-1 Endpoints, Intermediate Devices and Service Providers MUST be prepared to handle location represented in either civic or geo form. INT-2 Elements MUST NOT convert (civic to geo or geo to civic) from the form of location the determination mechanism supplied. INT-3 Any suitable location determination mechanism MAY be used. Rosen & Polk Expires August 28, 2008 [Page 39] Internet-Draft Emergency Call Phone BCP February 2008 INT-4 Devices, intermediate Devices and/or access networks SHOULD support a manual method to "override" the location the access network determines. Where a civic form of location is provided, all fields in the PIDF-LO [RFC4119] and [RFC5139] MUST be able to be specified. INT-5 Access networks and intermediate devices providing wire database location information SHOULD provide interior location data (building, floor, room, cubicle) where possible. It is RECOMMENDED that interior location be provided when spaces exceed approximately 650 square meters. INT-6 Access networks and intermediate devices (including enterprise networks) which support intermediate range wireless connections (typically 100m or less of range) and which do not support a more accurate location determination mechanism such as triangulation, MUST support location configuration where the location of the access point is reflected as the location of the clients of that access point. Where the access network provides location configuration, intermediate devices MUST either be transparent to it, or provide an interconnected client for the supported configuration mechanism and a server for a configuration protocol supported by end devices upstream of the intermediate device INT-7 Devices MAY support end-system measured location. Uncertainty of less than 100 m with 95% confidence SHOULD be available for dispatch. INT-8 Devices that support endpoint measuring of location MUST have at least a coarse location capability (typically <1km accuracy when not location hiding) at all times for routing of calls. This mechanism MAY be a service provided by the access network. INT-9 Endpoints SHOULD do configure their own location. INT-10 Where proxies provide location on behalf of endpoints, the the service provider MUST ensure that either the end device is provided with the local dial strings for its current location (where the end device recognizes dial strings), or the service provider proxy MUST detect the appropriate local dial strings at the time of the call. INT-11 Devices SHOULD be able to accept and forward location by value or by reference. An end device that receives location by reference (and does not also get the corresponding value) MUST be able to perform a dereference operation to obtain a value. INT-12 Devices MUST support all of: DHCP location options [RFC4676] and [RFC3825], HELD [I-D.ietf-geopriv-http-location-delivery] and LLDP-MED [LLDP-MED]. Rosen & Polk Expires August 28, 2008 [Page 40] Internet-Draft Emergency Call Phone BCP February 2008 INT-13 The access network MUST support at least one of: DHCP location options, HELD or LLDP-MED. INT-14 Where a router is employed between a LAN and WAN in a small (less than approximately 650 square meters) area, the router MUST be transparent to the location provided by the WAN to the LAN. This may mean the router must obtain location as a client from the WAN, and supply an LCP server to the LAN with the location it obtains. Where the area is larger, the LAN MUST have a location configuration mechanism meeting this BCP. INT-15 Endpoints SHOULD try all LCPs supported by the device in any order or in parallel. The first one that succeeds in supplying location can be used. INT-16 Access networks that support more than one LCP MUST reply with the same location information (within the limits of the data format for the specific LCP) for all LCPs it supports. INT-17 When HELD is the LCP, the request MUST specify a value of "emergencyRouting" for the "responseTime" parameter and use the resulting location for routing. If a value for dispatch location will be sent, another request with the "responseTime" parameter set to "emergencyDispatch" must be completed, with the result sent for dispatch purposes. INT-18 Endpoints SHOULD obtain location immediately after obtaining local network configuration information.When HELD is the LCP the client MUST support a random back-off period (between 30 seconds and 300 seconds) for re-trying the HELD query, when no response is received. INT-19 If the device is configured to use DHCP for bootstrapping, it MUST include both options for location acquisition (civic and geodetic), the option for LIS discovery, and the option for LoST discovery as defined in [RFC4676], [RFC3825], [I-D.thomson-geopriv-lis-discovery] and [I-D.ietf-ecrit-dhc-lost-discovery]. INT-20 If the device sends a DHCP INFORM message, it MUST include both options for location acquisition (civic and geodetic), the option for LIS discovery, and the option for LoST discovery as defined in [RFC4676], [RFC3825], [I-D.thomson-geopriv-lis-discovery] and [I-D.ietf-ecrit-dhc-lost-discovery]. INT-21 To minimize the effects of VPNs that do not allow split tunneling VPNs, location configuration SHOULD be attempted before such tunnels are established. Rosen & Polk Expires August 28, 2008 [Page 41] Internet-Draft Emergency Call Phone BCP February 2008 INT-22 Software which uses LCPs SHOULD locate and use the actual hardware network interface rather than a VPN tunnel interface to direct LCP requests to the LIS in the actual access network. INT-23 For devices which are not expected to roam, refreshing location on the order of once per day is RECOMMENDED. INT-24 For devices which roam, refresh of location information SHOULD be more frequent, with the frequency related to the mobility of the device and the ability of the access network to support the refresh operation. If the device can detect that it has moved, for example when it changes access points, the device SHOULD refresh its location. INT-25 It is RECOMMENDED that location determination not take longer than 250 ms to obtain routing location and systems SHOULD be designed such that the typical response is under 100 ms. However, as much as 3 seconds to obtain routing location MAY be tolerated if location accuracy can be substantially improved over what can be obtained in 250 ms. Authors' Addresses Brian Rosen NeuStar 470 Conrad Dr. Mars, PA 16046 US Phone: +1 724 382 1051 Email: br@brianrosen.net James Polk Cisco Systems 3913 Treemont Circle Colleyville, TX 76034 US Phone: +1-817-271-3552 Email: jmpolk@cisco.com Rosen & Polk Expires August 28, 2008 [Page 42] Internet-Draft Emergency Call Phone BCP February 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Rosen & Polk Expires August 28, 2008 [Page 43]