[Docs] [txt|pdf|xml] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 RFC 6881

ecrit                                                           B. Rosen
Internet-Draft                                                   NeuStar
Intended status: Standards Track                                 J. Polk
Expires: March 21, 2008                                    Cisco Systems
                                                      September 18, 2007


    Best Current Practice for Communications Services in support of
                           Emergency Calling
                      draft-ietf-ecrit-phonebcp-02

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 March 21, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   The IETF has several efforts targeted at standardizing various
   aspects of placing emergency calls.  This memo describes best current
   practice on how devices, networks and services should use such
   standards to make emergency calls.





Rosen & Polk             Expires March 21, 2008                 [Page 1]

Internet-Draft          Emergency Call Phone BCP          September 2007


Table of Contents

   1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Overview of how emergency calls are placed . . . . . . . . . .  3
   4.  Which devices and sevices should support emergency  calls  . .  3
   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  . . . . . . . . . .  5
       6.2.2.  Access network "wire database" location
               information  . . . . . . . . . . . . . . . . . . . . .  5
       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 . . . . . . . . . . .  6
     6.4.  Location and references to location  . . . . . . . . . . .  7
     6.5.  End system location configuration  . . . . . . . . . . . .  7
     6.6.  When location should be configured . . . . . . . . . . . .  7
     6.7.  Conveying location in SIP  . . . . . . . . . . . . . . . .  8
     6.8.  Location updates . . . . . . . . . . . . . . . . . . . . .  8
     6.9.  Multiple locations . . . . . . . . . . . . . . . . . . . .  9
     6.10. Location validation  . . . . . . . . . . . . . . . . . . .  9
     6.11. Default location . . . . . . . . . . . . . . . . . . . . . 10
     6.12. Other location considerations  . . . . . . . . . . . . . . 10
   7.  Uninitialized devices  . . . . . . . . . . . . . . . . . . . . 10
   8.  Routing the call to the PSAP . . . . . . . . . . . . . . . . . 11
   9.  Signaling of emergency calls . . . . . . . . . . . . . . . . . 12
     9.1.  Use of TLS . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.2.  SIP signaling requirements for User Agents . . . . . . . . 12
     9.3.  SIP signaling requirements for proxy servers . . . . . . . 13
   10. Call backs . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   11. Mid-call behavior  . . . . . . . . . . . . . . . . . . . . . . 14
   12. Call termination . . . . . . . . . . . . . . . . . . . . . . . 15
   13. Disabling of features  . . . . . . . . . . . . . . . . . . . . 15
   14. Media  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
   15. Testing  . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
   16. Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
   18. Normative References . . . . . . . . . . . . . . . . . . . . . 18
   Appendix A.  BCP Requirements Sorted by Responsible Party  . . . . 22
     A.1.  Requirements of End Devices  . . . . . . . . . . . . . . . 22
     A.2.  Requirements of Service Providers  . . . . . . . . . . . . 30
     A.3.  Requirements of Access Networks  . . . . . . . . . . . . . 34
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37
   Intellectual Property and Copyright Statements . . . . . . . . . . 38





Rosen & Polk             Expires March 21, 2008                 [Page 2]

Internet-Draft          Emergency Call Phone BCP          September 2007


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 SIP User Agents and proxy servers 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 devices and applications, access networks,
   service providers and PSAPs to achieve globally interoperable
   emergency calling on the Internet.


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 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 INVITE request.


4.  Which devices and sevices should support emergency  calls

   ED-1 if a user could reasonably expect to be able to place a call for
   help with the device, then the device or application SHOULD support
   emergency calling.

   SP-1 If a device or application expects to be able to place a call



Rosen & Polk             Expires March 21, 2008                 [Page 3]

Internet-Draft          Emergency Call Phone BCP          September 2007


   for help, the service that supports it SHOULD 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 do dial string recognition of emergency dial
   strings.

   SP-2 Proxy servers SHOULD do dial string recognition of emergency
   dial strings if for some reason the endpoint does not recognize them.

   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 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
   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.  Devices/Service
   Providers MUST be capable of recognizing all of the associated dial
   strings.




Rosen & Polk             Expires March 21, 2008                 [Page 4]

Internet-Draft          Emergency Call Phone BCP          September 2007


6.  Location and its role in an emergency call

   Location 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,
   Location Mapping Protocols, 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 ways location can be specified.  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/SP-10 Endpoints and Service Providers MUST be prepared to
   handle location represented in either civic or geo form.

   ED-13/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/AN-2 Any suitable location determination mechanism MAY be used.

6.2.1.  User-entered location information

   ED-15/AN-3 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 [I-D.ietf-geopriv-revised-civic-lo] 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



Rosen & Polk             Expires March 21, 2008                 [Page 5]

Internet-Draft          Emergency Call Phone BCP          September 2007


   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 providing wire database location information
   SHOULD provide interior location data where possible.  It is
   RECOMMENDED that interior location be provided when spaces exceed
   approximately 650 m2.

   AN-6 Access networks (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 which reports the location of the access point as the
   location of the clients of that access point.

6.2.3.  End-system measured location  information

   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/AN-7 Devices that support endpoint measuring of location MUST
   have at least a coarse location (<1km) capability 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
   measured location MUST require 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 (<1km) capability at all times for routing
   of calls.

   AN-10 Access networks with range of <10M MUST provide a location to
   mobile devices connected to it.  The location provided SHOULD be that
   of the beacon location unless a more accurate mechanism is provided.

6.3.  Who adds location, endpoint or proxy

   ED-18 Endpoints SHOULD do location configuration themselves.

   SP-12 Proxies MAY provide location on behalf of devices it supports
   if:



Rosen & Polk             Expires March 21, 2008                 [Page 6]

Internet-Draft          Emergency Call Phone BCP          September 2007


   o  It has a relationship with all access networks the device could
      connect to, and the relationship allows it to obtain location.
   o  It has an identifier that can be used by the access network to
      determine the location of the endpoint, particularly in the
      presence of NAT and VPN tunnels that may exist between the access
      network and the service provider.

   ED-19/SP-13 Where proxies provide location on behalf of endpoints,
   the proxy MUST provide a mechanism to supply emergency dial strings
   to the device if the device recognizes them, or the proxy MUST track
   the location of the device with sufficient accuracy and timeliness to
   be able to recognize the local dial string at the time of an
   emergency call.

6.4.  Location and references to location

   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.

6.5.  End system location configuration

   ED-21 endpoints 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 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 650m2), the LAN MUST reflect the location
   provided by the WAN to the LAN.

   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.

   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.

6.6.  When location should be configured

   ED-23 Endpoints SHOULD obtain location immediately after obtaining
   local network configuration information.

   ED-24 To minimize the effects of non-bypassable VPNs, location



Rosen & Polk             Expires March 21, 2008                 [Page 7]

Internet-Draft          Emergency Call Phone BCP          September 2007


   configuration SHOULD be attempted before such tunnels are
   established.

   ED-25 Software which uses LCPs SHOULD locate and use the actual
   hardware network interface.

   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.

   AN-15 Placement of NAT devices should consider the effect of the NAT
   on the LCP.

   ED-26 For devices which are not expected to roam, refreshing on the
   order of once per day is RECOMMENDED.

   ED-27 For devices which roam, refresh of location 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.  There can be instances in which a device is aware of when
   it moves, for example when it changes access points.  When this type
   of event occurs, the device SHOULD refresh its location.

   ED-28/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 100ms.  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-29/SP-14 Location sent between SIP elements MUST be conveyed using
   [I-D.ietf-sip-location-conveyance].

6.8.  Location updates

   ED-30/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-31/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-32/AN-19 The LIS SHOULD provide a location reference which permits



Rosen & Polk             Expires March 21, 2008                 [Page 8]

Internet-Draft          Emergency Call Phone BCP          September 2007


   a subscription with appropriate filtering.

   ED-33/AN-20 For calls sent with location-by-reference, with a SIP or
   SIPS scheme, the server resolving the reference MUST support a
   SUBSCRIBE [RFC3118] to the presence event [RFC3856].  For other
   location-by-reference schemes, a repeated location dereference by the
   PSAP MUST be supported.

   ED-34 If location was sent by value, and the endpoint gets updated
   location, it MUST send the updated location to the PSAP via reINVITE
   or UPDATE.  Such updates SHOULD be limited to no more than one update
   every 10 seconds.

6.9.  Multiple locations

   ED-35 If a UA has more than one location available to it, it MUST
   choose one location to use to route the call towards the PSAP.

   SP-15 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-16 If a proxy is attempting to assert 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.

   SP-17 All location objects received by a proxy MUST be delivered to
   the PSAP.

   ED-36/SP-18 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-37/SP-19 The "used-for-routing" parameter MUST be set to the
   location that was used to query LoST.

6.10.  Location validation

   AN-21 Location validation of civic locations via LoST SHOULD be
   performed by the LIS before entering a location in its database.

   ED-38 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.




Rosen & Polk             Expires March 21, 2008                 [Page 9]

Internet-Draft          Emergency Call Phone BCP          September 2007


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.

   SP-20 Proxies handling emergency calls MUST insert a default location
   if the call does not contain a location.

   AN-23/SP-21 Default locations MUST be marked with method=Default and
   an appropriate provided-by in the PIDF-LO.

6.12.  Other location considerations

   ED-39 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-40/AN-24 To prevent against spoofing of the DHCP server, elements
   implementing DHCP for location configuration SHOULD use [RFC3118].

   ED-41 S/MIME MUST NOT be used to protect the Geolocation header or
   bodies.

   ED-42/SP-22 TLS MUST be used to protect location (but see Section 9).


7.  Uninitialized devices

   ED-43 Uninitialized devices SHOULD NOT lead a user to believe an
   emergency call could be placed on it unless local regulations require
   it.

   ED-44/AN-25/SP-23 Uninitialized devices SHOULD NOT be capable of
   placing an emergency call unless local regulations require it.

   ED-45/AN-26/SP-24 Uninitialized devices that can place emergency
   calls MUST supply location the same as a fully capable device would.

   ED-46/SP-25 Unitialized Devices MUST supply a call back URI.  See
   Section 7.

   ED-47/SP-26 Unitialized Devices MUST include identifiers in the
   signaling that can be used by the service provider to identify the
   device and to allow filtering of calls from the device by the PSAP/
   ESRP.




Rosen & Polk             Expires March 21, 2008                [Page 10]

Internet-Draft          Emergency Call Phone BCP          September 2007


8.  Routing the call to the PSAP

   ED-48 Endpoints who obtain their own location SHOULD perform LoST
   mapping to the PSAP URI.

   ED-49 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 use.

   ED-50 The endpoint SHOULD 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-51 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.

   SP-27 All proxies in the outbound path SHOULD 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 Route header 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 with the URI obtained.

   SP-28 To deal with old user agents that predate this specification
   and with UAs that do not have access to their own location data,
   proxies that recognize 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 become the Request URI.

   SP-29 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-30 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-52/SP-31 [RFC3261] and [RFC3263] procedures MUST be used to route
   an emergency call towards the PSAP's URI.

   ED-53 Initial INVITES MUST provide an Offer [RFC3264].




Rosen & Polk             Expires March 21, 2008                [Page 11]

Internet-Draft          Emergency Call Phone BCP          September 2007


9.  Signaling of emergency calls

   ED-54 Best Current Practice for SIP user agents including handling of
   audio, video and real-time text [RFC4103] SHOULD be applied.  This
   memo can be considered as an addition to it for endpoints.

9.1.  Use of TLS

   ED-55/SP-32 sips: MUST be specified when attempting to signal an
   emergency call with SIP.

   ED-56/SP-33 If TLS session establishment fails, the call MUST be
   retried with sip:.

   ED-57/SP-34 [I-D.ietf-sip-outbound] is RECOMMENDED to maintain
   persistent TLS connections between elements.

   ED-58/AN-27 https: MUST be specified when attempting to retrieve
   location (configuration or dereferencing) with HELD.

   ED-59/AN33 If TLS session establishment fails, the location
   retrieveal MUST be retried with http:.

9.2.  SIP signaling requirements for User Agents

   ED-60 The initial SIP signaling Method is an INVITE:
   1.   The Request URI SHOULD be the service URN in the "sos" tree, If
        the device cannot do local dial string interpretation, the
        Request-URI SHOULD be a dialstring URI [RFC4967] with the dialed
        digits.
   2.   The To: header MUST be present and SHOULD be a service URN in
        the "sos" tree.  If the device cannot do local dial string
        interpretation, the To: SHOULD be a dialstring 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 and SHOULD include the URI of the
        device.
   5.   A Route: header SHOULD be present with a PSAP URI obtained from
        LoST (see Section 8) and the loose route parameter.  A sips URI
        [RFC3261] SHOULD be specified, unless the operation must be
        retried due to a failure to establish a TLS connection.  If the
        device does not do dial plan interpretation, 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.



Rosen & Polk             Expires March 21, 2008                [Page 12]

Internet-Draft          Emergency Call Phone BCP          September 2007


   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 or
        by-reference.
   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] then whichever location
        is used for routing the message towards the PSAP or ESRP, even
        if there is only one, the Geolocation "message-routed-on- this-
        uri" header parameter SHOULD be added to the corresponding URI
        in the Geolocation header.
   12.  A normal SDP offer SHOULD be included in the INVITE.  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.

9.3.  SIP signaling requirements for proxy servers

   SP-35 SIP Proxy servers processing emergency calls:
   1.  If the proxy does dial plan interpretation on behalf of user
       agents, the proxy MUST look for the local emergency dialstring at
       the location of the end device and MAY look for the home
       dialstring.  If it finds it, the proxy MUST:
       *  Insert a Geolocation header as per 10-12 above.  Location-by-
          reference MUST be used because proxies may not insert bodies.
       *  Include the Geolocation "inserted-by=server" AND "routed-by-
          this-uri" parameters.
       *  Map the location to a PSAP uri using LoST.





Rosen & Polk             Expires March 21, 2008                [Page 13]

Internet-Draft          Emergency Call Phone BCP          September 2007


       *  Add a Route header with the service URN appropriate for the
          emergency dialstring.
       *  Replace the Request-URI (which was the dialstring) with the
          PSAP URI obtained from LoST.
       *  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-36 Unitialized devices MUST have a globally routable URI in a
   Contact: header.

   SP-37 Unitialized devices SHOULD have a persistent URI in a
   P-Asserted-Identity: header.


11.  Mid-call behavior

   ED-61/SP-38 During the course of an emergency call, devices and
   proxies MUST support REFER transactions and the Referred-by: header
   [RFC3515] to:
   1.  Be REFERed to a conference bridge; PSAPs often include
       dispatchers, responders or specialists on a call.
   2.  Be REFERed to a secondary PSAP.  Some responder's dispatchers are
       not located in the primary PSAP.  The call may have to be
       transferred to another PSAP.  Most often this will be an attended
       transfer, or a bridged transfer.(For devices that are Mobile).



Rosen & Polk             Expires March 21, 2008                [Page 14]

Internet-Draft          Emergency Call Phone BCP          September 2007


   ED-62/SP-39User agents and proxies MUST Support Session
   Timer[RFC4028] to guard against session corruption.


12.  Call termination

   ED-63 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, and when
   answered, reconnect the caller to the PSAP.

   ED-64 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 expires the call MAY be declared lost.  If in
   the interval, an incoming call is received from the domain of the
   PSAP, the device SHOULD drop the old call and alert for the (new)
   incoming call.  Dropping of the old call SHOULD 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-65/SP-40 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.

   ED-66/SP-41 The emergency dialstrings SHOULD NOT be permitted in Call
   Forward numbers or speed dial lists.

   ED-67/SP-42 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-68 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



Rosen & Polk             Expires March 21, 2008                [Page 15]

Internet-Draft          Emergency Call Phone BCP          September 2007


   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-69 Endpoints MUST send and receive media streams on RTP [RFC3550].

   ED-70 Normal SIP offer/answer [RFC3264] negotiations MUST be used to
   agree on the media streams to be used.

   ED-71 Endpoints supporting voice MUST support G.711 A law (and mu Law
   in North America) encoded voice as described in [RFC3551].  It is
   desirable to support wideband codecs in the offer.

   ED-72 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-73 Endpoints supporting IM MUST support either [RFC3428] or
   [RFC3920].

   ED-74 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-75 Endpoints supporting video MUST support H.264 per [RFC3984].


15.  Testing

   ED-76 INVITE requests to a service urn with a urn parameter of "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
   does not support the test mechanism.

   ED-77 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



Rosen & Polk             Expires March 21, 2008                [Page 16]

Internet-Draft          Emergency Call Phone BCP          September 2007


   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-78 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-79 User agents SHOULD perform a full call test, including media
   loopback, after a disconnect and subsequent change in IP address.
   After an initial IP address assignment test, a full test SHOULD be
   repeated approximately every 30 days with a random interval.

   ED-80 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-81 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
   draft-ietf-ecrit-security- threats, and the forthcoming GEOPRIV
   security document(s).

   Ed.  Note: go through that doc and make sure any actions needed are
   captured in the BCP text.


17.  Acknowledgements

   Work group members participating in the creation and review of this
   document include include Hannes Tschofenig, Ted Hardie, Marc Linsner,
   Roger Marshall, Stu Goldman, Shida Schubert, James Winterbottom,
   Roger Marshall, Barbara Stark, Richard Barnes and Peter Blatherwick.






Rosen & Polk             Expires March 21, 2008                [Page 17]

Internet-Draft          Emergency Call Phone BCP          September 2007


18.  Normative References

   [I-D.ietf-ecrit-framework]
              Rosen, B., "Framework for Emergency Calling using Internet
              Multimedia", draft-ietf-ecrit-framework-02 (work in
              progress), July 2007.

   [I-D.ietf-ecrit-lost]
              Hardie, T., "LoST: A Location-to-Service Translation
              Protocol", draft-ietf-ecrit-lost-06 (work in progress),
              August 2007.

   [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.

   [I-D.ietf-geopriv-http-location-delivery]
              Barnes, M., "HTTP Enabled Location Delivery (HELD)",
              draft-ietf-geopriv-http-location-delivery-01 (work in
              progress), July 2007.

   [I-D.ietf-geopriv-pdif-lo-profile]
              Tschofenig, H., "GEOPRIV PIDF-LO Usage Clarification,
              Considerations and Recommendations",
              draft-ietf-geopriv-pdif-lo-profile-08 (work in progress),
              July 2007.

   [I-D.ietf-geopriv-revised-civic-lo]
              Thomson, M. and J. Winterbottom, "Revised Civic Location
              Format for PIDF-LO",
              draft-ietf-geopriv-revised-civic-lo-05 (work in progress),
              February 2007.

   [I-D.ietf-mmusic-media-loopback]



Rosen & Polk             Expires March 21, 2008                [Page 18]

Internet-Draft          Emergency Call Phone BCP          September 2007


              Hedayat, K., "An Extension to the Session Description
              Protocol (SDP) for Media Loopback",
              draft-ietf-mmusic-media-loopback-06 (work in progress),
              April 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-14 (work in progress),
              June 2007.

   [I-D.ietf-sip-location-conveyance]
              Polk, J. and B. Rosen, "Location Conveyance for the
              Session Initiation Protocol",
              draft-ietf-sip-location-conveyance-08 (work in progress),
              July 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-10 (work in progress), July 2007.

   [I-D.ietf-sipping-config-framework]
              Petrie, D. and S. Channabasappa, "A Framework for Session
              Initiation Protocol User Agent Profile Delivery",
              draft-ietf-sipping-config-framework-12 (work in progress),
              June 2007.

   [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-07 (work in progress),
              August 2006.

   [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.



Rosen & Polk             Expires March 21, 2008                [Page 19]

Internet-Draft          Emergency Call Phone BCP          September 2007


   [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.

   [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.

   [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.

   [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



Rosen & Polk             Expires March 21, 2008                [Page 20]

Internet-Draft          Emergency Call Phone BCP          September 2007


              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.

   [RFC3920]  Saint-Andre, P., Ed., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 3920, October 2004.

   [RFC3966]  Schulzrinne, H., "The tel URI for Telephone Numbers",
              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.

   [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.




Rosen & Polk             Expires March 21, 2008                [Page 21]

Internet-Draft          Emergency Call Phone BCP          September 2007


Appendix A.  BCP Requirements Sorted by Responsible Party

A.1.  Requirements of End Devices

   ED-1 if a user could reasonably expect to be able to place a call for
   help with the device, then the device or application SHOULD support
   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

   ED-3 Endpoints SHOULD do dial string recognition of emergency dial
   strings

   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 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.  Devices/Service
   Providers MUST be capable of recognizing all of the associated dial
   strings.

   ED-12 Endpoints 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.




Rosen & Polk             Expires March 21, 2008                [Page 22]

Internet-Draft          Emergency Call Phone BCP          September 2007


   ED-15 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 [I-D.ietf-geopriv-revised-civic-lo] 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 (<1km) capability at all times for routing
   of calls.  This mechanism MAY be a service provided by the access
   network.

   ED-18 Endpoints SHOULD do location configuration themselves.

   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 endpoints 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 Endpoints SHOULD obtain location immediately after obtaining
   local network configuration information.

   ED-24 To minimize the effects of non-bypassable VPNs, location
   configuration SHOULD be attempted before such tunnels are
   established.

   ED-25 Software which uses LCPs SHOULD locate and use the actual
   hardware network interface.

   ED-26 For devices which are not expected to roam, refreshing on the
   order of once per day is RECOMMENDED

   ED-27 For devices which roam, refresh of location 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.  There can be instances in which a device is aware of when
   it moves, for example when it changes access points.  When this type



Rosen & Polk             Expires March 21, 2008                [Page 23]

Internet-Draft          Emergency Call Phone BCP          September 2007


   of event occurs, the device SHOULD refresh its location.

   ED-28 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 100ms.  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-29 Location sent between SIP elements MUST be conveyed using
   [I-D.ietf-sip-location-conveyance].

   ED-30 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-31 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-32 The LIS SHOULD provide a location reference which permits a
   subscription with appropriate filtering.

   ED-33 For calls sent with location-by-reference, with a SIP or SIPS
   scheme, the server resolving the reference MUST support a SUBSCRIBE
   [RFC3118] to the presence event [RFC3856].  For other location-by-
   reference schemes, a repeated location dereference by the PSAP MUST
   be supported.

   ED-34 If location was sent by value, and the endpoint gets updated
   location, it MUST send the updated location to the PSAP via reINVITE
   or UPDATE.  Such updates SHOULD be limited to no more than one update
   every 10 seconds.

   ED-35 If a UA has more than one location available to it, it MUST
   choose one location to use to route the call towards the PSAP.

   ED-36/ 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-37 The "used-for-routing" parameter MUST be set to the location
   that was used to query LoST.

   ED-38 Endpoints SHOULD validate civic locations when they receive



Rosen & Polk             Expires March 21, 2008                [Page 24]

Internet-Draft          Emergency Call Phone BCP          September 2007


   them from their LCP.  Validation SHOULD be performed in conjunction
   with the LoST route query to minimize load on the LoST server.

   ED-39 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-40 To prevent against spoofing of the DHCP server, elements
   implementing DHCP for location configuration SHOULD use [RFC3118].

   ED-41 S/MIME MUST NOT be used to protect the Geolocation header or
   bodies.

   ED-42 TLS MUST be used to protect location (but see Section 9).

   ED-43 Uninitialized devices SHOULD NOT lead a user to believe an
   emergency call could be placed on it unless local regulations require
   it.

   ED-44 Uninitialized devices SHOULD NOT be capable of placing an
   emergency call unless local regulations require it.

   ED-45 Uninitialized devices that can place emergency calls MUST
   supply location the same as a fully capable device would.

   ED-46 Unitialized Devices MUST supply a call back URI.  See Section 7

   ED-47 Unitialized Devices MUST include identifiers in the signaling
   that can be used by the service provider to identify the device and
   to allow filtering of calls from the device by the PSAP/ESRP.

   ED-48 Endpoints who obtain their own location SHOULD perform LoST
   mapping to the PSAP URI.

   ED-49 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 use.

   ED-50 The endpoint SHOULD 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-51 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.

   ED-52 [RFC3261] and [RFC3263] procedures MUST be used to route an



Rosen & Polk             Expires March 21, 2008                [Page 25]

Internet-Draft          Emergency Call Phone BCP          September 2007


   emergency call towards the PSAP's URI.

   ED-53 Initial INVITES MUST provide an Offer [RFC3264]

   ED-54 Best Current Practice for SIP user agents including handling of
   audio, video and real-time text [RFC4103] SHOULD be applied.  This
   memo can be considered as an addition to it for endpoints.

   ED-55 sips: MUST be specified when attempting to signal an emergency
   call with SIP

   ED-56 If TLS session establishment fails, the call MUST be retried
   with sip:

   ED-57 [I-D.ietf-sip-outbound] is RECOMMENDED to maintain persistent
   TLS connections between elements

   ED-58 https: MUST be specified when attempting to retrieve location
   (configuration or dereferencing) with HELD

   ED-59 If TLS session establishment fails, the location retrieveal
   MUST be retried with http:

   ED-60 The initial SIP signaling Method is an INVITE:
   1.   The Request URI SHOULD be the service URN in the "sos" tree, If
        the device cannot do local dialstring interpretation, the
        Request-URI SHOULD be a dialstring URI [RFC4967] with the dialed
        digits.
   2.   The To: header MUST be present and SHOULD be a service URN in
        the "sos" tree.  If the device cannot do local dialstring
        interpretation, the To: SHOULD be a dialstring 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 and SHOULD include the URI of the
        device.
   5.   A Route: header SHOULD be present with a PSAP URI obtained from
        LoST (see Section 8 ) and the loose route parameter.  A sips URI
        [RFC3261] SHOULD be specified, unless the operation must be
        retried due to a failure to establish a TLS connection.  If the
        device does not do dial plan interpretation, 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.





Rosen & Polk             Expires March 21, 2008                [Page 26]

Internet-Draft          Emergency Call Phone BCP          September 2007


   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 or
        by-reference.
   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] then whichever location
        is used for routing the message towards the PSAP or ESRP, even
        if there is only one, the Geolocation "message-routed-on- this-
        uri" header parameter SHOULD be added to the corresponding URI
        in the Geolocation header.
   12.  A normal SDP offer SHOULD be included in the INVITE.  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.

   ED-61 During the course of an emergency call, devices and proxies
   MUST support REFER transactions and the Referred-by: header [RFC3515]
   to:
   1.  Be REFERed to a conference bridge; PSAPs often include
       dispatchers, responders or specialists on a call.
   2.  Be REFERed to a secondary PSAP.  Some responder's dispatchers are
       not located in the primary PSAP.  The call may have to be
       transferred to another PSAP.  Most often this will be an attended
       transfer, or a bridged transfer.(For devices that are Mobile).

   ED-62 User agents and proxies MUST Support Session Timer [RFC4028] to
   guard against session corruption.

   ED-63 UACs with an active emergency call (i.e.  SIP Dialog) MUST NOT



Rosen & Polk             Expires March 21, 2008                [Page 27]

Internet-Draft          Emergency Call Phone BCP          September 2007


   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, and when
   answered, reconnect the caller to the PSAP.

   ED-64 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 expires the call MAY be declared lost.  If in
   the interval, an incoming call is received from the domain of the
   PSAP, the device SHOULD drop the old call and alert for the (new)
   incoming call.  Dropping of the old call SHOULD 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-65 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.

   ED-66 The emergency dialstrings SHOULD NOT be permitted in Call
   Forward numbers or speed dial lists.

   ED-67 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-68 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-69 Endpoints MUST send and receive media streams on RTP [RFC3550].

   ED-70 Normal SIP offer/answer [RFC3264] negotiations MUST be used to
   agree on the media streams to be used.

   ED-71 Endpoints supporting voice MUST support G.711 A law (and mu Law
   in North America) encoded voice as described in [RFC3551].  It is



Rosen & Polk             Expires March 21, 2008                [Page 28]

Internet-Draft          Emergency Call Phone BCP          September 2007


   desirable to support wideband codecs in the offer.

   ED-72 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-73 Endpoints supporting IM MUST support either [RFC3428] or
   [RFC3920].

   ED-74 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-75 Endpoints supporting video MUST support H.264 per [RFC3984].

   ED-76 INVITE requests to a service urn with a urn parameter of "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
   does not support the test mechanism.

   ED-77 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-78 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-79 User agents SHOULD perform a full call test, including media
   loopback, after a disconnect and subsequent change in IP address.



Rosen & Polk             Expires March 21, 2008                [Page 29]

Internet-Draft          Emergency Call Phone BCP          September 2007


   After an initial IP address assignment test, a full test SHOULD be
   repeated approximately every 30 days with a random interval.

   ED-80 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-81 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 that supports it SHOULD facilitate emergency
   calling.

   SP-2 Proxy servers SHOULD do dial string recognition of emergency
   dial strings if for some reason the endpoint does not recognize them.

   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 LoST
   [I-D.ietf-ecrit-lost].

   SP-7 Proxy Servers MUST recognize emergency dial strings represented
   by [RFC4967] and SHOULD recognize 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.  Devices/Service Providers MUST be capable of
   recognizing all of the associated dial strings.

   SP-10 Endpoints 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.




Rosen & Polk             Expires March 21, 2008                [Page 30]

Internet-Draft          Emergency Call Phone BCP          September 2007


   SP-12 Proxies MAY provide location on behalf of devices it supports
   if:
   o  It has a relationship with all access networks the device could
      connect to, and the relationship allows it to obtain location.
   o  It has an identifier that can be used by the access network to
      determine the location of the endpoint, particularly in the
      presence of NAT and VPN tunnels that may exist between the access
      network and the service provider.

   SP-13 Where proxies provide location on behalf of endpoints, the
   proxy MUST provide a mechanism to supply emergency dia lstrings to
   the device if the device recognizes them, or the proxy MUST track the
   location of the device with sufficient accuracy and timeliness to be
   able to recognize the local dial string at the time of an emergency
   call.

   SP-14 Location sent between SIP elements MUST be conveyed using
   [I-D.ietf-sip-location-conveyance].

   SP-15 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-16 If a proxy is attempting to assert 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.

   SP-17 All location objects received by a proxy MUST be delivered to
   the PSAP.

   SP-18 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-19 The "used-for-routing" parameter MUST be set to the location
   that was used to query LoST.

   SP-20 Proxies handling emergency calls MUST insert a default location
   if the call does not contain a location.

   SP-21 Default locations MUST be marked with method=Default and an
   appropriate provided-by in the PIDF-LO.

   SP-22 TLS MUST be used to protect location (but see Section 9).




Rosen & Polk             Expires March 21, 2008                [Page 31]

Internet-Draft          Emergency Call Phone BCP          September 2007


   SP-23 Uninitialized devices SHOULD NOT be capable of placing an
   emergency call unless local regulations require it.

   SP-24 Uninitialized devices that can place emergency calls MUST
   supply location the same as a fully capable device would.

   SP-25 Unitialized Devices MUST supply a call back URI.  See Section 7

   SP-26 Unitialized Devices MUST include identifiers in the signaling
   that can be used by the service provider to identify the device and
   to allow filtering of calls from the device by the PSAP/ESRP.

   SP-27 All proxies in the outbound path SHOULD 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 Route header 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 with the URI obtained.

   SP-28 To deal with old user agents that predate this specification
   and with UAs that do not have access to their own location data,
   proxies that recognize 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 become the Request URI.

   SP-29 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-30 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-31 [RFC3261] and [RFC3263] procedures MUST be used to route an
   emergency call towards the PSAP's URI.

   SP-32 sips: MUST be specified when attempting to signal an emergency
   call with SIP

   SP-33 If TLS session establishment fails, the call MUST be retried
   with sip:

   SP-34 [I-D.ietf-sip-outbound] is RECOMMENDED to maintain persistent
   TLS connections between elements



Rosen & Polk             Expires March 21, 2008                [Page 32]

Internet-Draft          Emergency Call Phone BCP          September 2007


   SP-35 SIP Proxy servers processing emergency calls:
   1.  If the proxy does dial plan interpretation on behalf of user
       agents, the proxy MUST look for the local emergency dialstring at
       the location of the end device and MAY look for the home
       dialstring.  If it finds it it MUST:
       *  Insert a Geolocation header as per 10-12 above.  Location-by-
          reference MUST be used because proxies may not insert bodies.
       *  Include the Geolocation "inserted-by=server" AND "routed-by-
          this-uri" parameters.
       *  Map the location to a PSAP uri using LoST.
       *  Add a Route header with the service URN appropriate for the
          emergency dialstring.
       *  Replace the Request-URI (which was the dialstring) with the
          PSAP URI obtained from LoST.
       *  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.

   SP-36 Unitialized devices MUST have a globally routable URI in a
   Contact: header

   SP-37 Unitialized devices SHOULD have a persistent URI in a
   P-Asserted-Identity: header

   SP-38 During the course of an emergency call, devices and proxies
   MUST support REFER transactions and the Referred-by: header [RFC3515]
   to:





Rosen & Polk             Expires March 21, 2008                [Page 33]

Internet-Draft          Emergency Call Phone BCP          September 2007


   1.  Be REFERed to a conference bridge; PSAPs often include
       dispatchers, responders or specialists on a call.
   2.  Be REFERed to a secondary PSAP.  Some responder's dispatchers are
       not located in the primary PSAP.  The call may have to be
       transferred to another PSAP.  Most often this will be an attended
       transfer, or a bridged transfer.(For devices that are Mobile)

   SP-39User agents and proxies MUST Support Session Timer [RFC4028] to
   guard against session corruption.

   SP-40 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.

   SP-41 The emergency dialstrings SHOULD NOT be permitted in Call
   Forward numbers or speed dial lists.

   SP-42 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 Networks

   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 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 [I-D.ietf-geopriv-revised-civic-lo] 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 providing wire database location information
   SHOULD provide interior location data where possible.  It is
   RECOMMENDED that interior location be provided when spaces exceed



Rosen & Polk             Expires March 21, 2008                [Page 34]

Internet-Draft          Emergency Call Phone BCP          September 2007


   approximately 650 m2

   AN-6 Access networks (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 which reports the location of the access point as the
   location of the clients of that access point.

   AN-7 Devices that support endpoint measuring of location MUST have at
   least a coarse location (<1km) capability 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
   measured location MUST require 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 (<1km) capability at all times for routing
   of calls.

   AN-10 Access networks with range of <10M MUST provide a location to
   mobile devices connected to it.  The location provided SHOULD be that
   of the beacon 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 650m2), the LAN MUST reflect the location
   provided by the WAN to the LAN.

   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.

   AN-15 Placement of NAT devices should consider the effect of the NAT
   on the LCP.

   AN-16 It is RECOMMENDED that location determination not take longer



Rosen & Polk             Expires March 21, 2008                [Page 35]

Internet-Draft          Emergency Call Phone BCP          September 2007


   than 250 ms to obtain routing location and systems SHOULD be designed
   such that the typical response is under 100ms.  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
   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
   [RFC3118] to the presence event [RFC3856].  For other location-by-
   reference schemes, a repeated location dereference by the PSAP MUST
   be supported.

   AN-21 Location validation of civic locations via LoST SHOULD be
   performed by the LIS 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.

   AN-23 Default locations MUST be marked with method=Default and an
   appropriate provided-by in the PIDF-LO.

   AN-24 To prevent against spoofing of the DHCP server, elements
   implementing DHCP for location configuration SHOULD use [RFC3118].

   AN-25 Uninitialized devices SHOULD NOT be capable of placing an
   emergency call unless local regulations require it.

   AN-26 Uninitialized devices that can place emergency calls MUST
   supply location the same as a fully capable device would.

   AN-27 https: MUST be specified when attempting to retrieve location
   (configuration or dereferencing) with HELD





Rosen & Polk             Expires March 21, 2008                [Page 36]

Internet-Draft          Emergency Call Phone BCP          September 2007


Authors' Addresses

   Brian Rosen
   NeuStar
   470 Conrad Dr.
   Mars, PA  16046
   US

   Phone: +1 724 382 1051
   Email: br@brianrosen.net


   James M. Polk
   Cisco Systems
   3913 Treemont Circle
   Colleyville, TX  76034
   US

   Phone: +1-817-271-3552
   Email: jmpolk@cisco.com































Rosen & Polk             Expires March 21, 2008                [Page 37]

Internet-Draft          Emergency Call Phone BCP          September 2007


Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   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 March 21, 2008                [Page 38]


Html markup produced by rfcmarkup 1.108, available from http://tools.ietf.org/tools/rfcmarkup/