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Standardizing IP-based Emergency Services

Standardizing IP-based Emergency Services. Hannes Tschofenig Nokia-Siemens IETF ECRIT Chair Hannes.tschofenig@gmx.net. Richard Barnes BBN Technologies IETF GEOPRIV Chair rbarnes@bbn.com. Goal of this Presentation. Understand the big picture of IP-based emergency services standardization.

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Standardizing IP-based Emergency Services

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  1. Standardizing IP-based Emergency Services Hannes TschofenigNokia-SiemensIETF ECRIT Chair Hannes.tschofenig@gmx.net Richard BarnesBBN TechnologiesIETF GEOPRIV Chair rbarnes@bbn.com

  2. Goal of this Presentation • Understand the big picture of IP-based emergency services standardization. • Learn about technical challenges and their solutions • Obtain pointers to documents for further reading (for in-depth study) • I am here to help! Ask questions

  3. High-Level Emergency Services Categorization • Authority-to-Citizen • Example: Tsunami warning • Authority-to-Authority • Example: Communication between emergency personnel Citizen-to-Authority Note that some Standards Development Organizations (SDOs) use the term “individuals” instead of “citizen”.

  4. Architectural Considerations End Host VoIP, Inc. (Application Service Provider) Layer 7 ISP, Inc. (Internet Service Provider) Layer 3 Last Mile, Inc. (Internet Access Provider) Layer 1/2

  5. Architectural Considerations, cont. • ISP/IAP has the technical means to know the precise location of the end host. • ASP, ISP and IAP are, in some cases, different entities. • Internet is a world-wide network; end points go everywhere – services come from everywhere. • There are a multitude of different business models with • Many different protocols being used • Long time to migrate and devices / networks with very different capabilities

  6. Assumptions about PSAP Capabilities • Throughout the subsequent slides we assume a IP-based PSAP to be present in the future emergency services architecture. • Architectural descriptions for how to interwork with legacy PSAPs can, for example, be found in the NENA i2 specification. • http://www.nena.org/media/File/08-001_20051205.pdf • Other national variants (often derived from the NENA i2 work exist)

  7. Putting the Pieces together • Work done in a couple of organizations • 3GPP/3GPP2 • Wimax Forum • NENA / EENA • OMA • ATIS ESIF • ETSI EMTEL • IETF • COCOM EGEA • E9-1-1 Institute • COMCARE • NIST …

  8. 3GPP, 3GPP2, Wimax Forum NENA/EENA IETF

  9. SIP Dependency • The IETF emergency services architecture does NOT require SIP being used between the User Agent and the VSP. • The usage of SIP is, however, documented for those using SIP. • Currently, there is no specification for usage of non-SIP protocols for emergency services. • Although the 3GPP IMS architecture utilizes SIP their communication model is different enough to cause interoperability problems with plain IETF SIP clients. As such, one could see the User Agent to VSP 3GPP specification as a different SIP dialect. • For interworking with IP-based PSAPs IETF and NENA assume the usage of SIP by the VSP. • Other organizations have a much stronger requirement for SIP usage, such as 3GPP, and 3GPP2.

  10. PSAP / Call Taker Today’s VoIP Emergency Service SubscriberDatabase (0) Enter Location User (3) LocationInfo (2) Query for location VoIP Call VoIP Call (1) (5) SIP Proxy dial 1-1-2 VSP

  11. Properties • Systems largely build on user-provided location information (and updates when necessary). • Causes problems when update is not provided in time. Challenges with nomadic usage and particularly with true mobility. • Requires call-taker to verify the provided location information. • Provided only by those who interwork with the PSTN (from a regulatory point of view). • VSP often hands calls over to emergency services interconnection provider to interface PSAP. • Emergency numbers are detected by the VSP. There is typically no special support for emergency calling provided by the User Agent software.

  12. Automatic Location • The ISP/IAP best knows the location of the end host. • Note: GPS, and location databases maintained by independent third parties do not require ISP/IAP. • However, these mechanisms work only under certain conditions. Hence, often seen as additional possibility rather than a replacement for ISP/IAP provided location. • Common understanding in the industry is that automatic location will have to be provided for VoIP emergency services in the mid- to long-term. • The next slides assume that such an automatic location capability is added for IP-based emergency services.

  13. PSAP / Call Taker “Legacy End Points” Location Information Server Routing Database (3) Location + Service Identifier (4) PSAP URI (2) Location (1) (5) INVITE Request URI: urn:service:sos To: 112 Route Header: PSAP URI < Reference to PIDF-LO> INVITE Request URI: 112 To: 112 SIP Proxy dial 1-1-2 VSP • Dial string provided by the end point may conform to RFC 4967 or RFC 3966. • Dial string recognition, location determination, route determination done by SIP proxy

  14. Challenges • Two challenges appear with the mentioned architecture: • How is the LIS discovered?The IP address is the only information that is available to the VSP. Hence, the IP address has to be used to determine the ISP. Based on this info the LIS run by the ISP has to be determined. • How is the emergency call routed to the nearest PSAP?Information about the PSAP boundaries need to be available.

  15. Disadvantages • When the emergency call is not recognized by the User Agent then • Call Waiting • Call Transfer • Three Way Call • Flash hold • Outbound Call Blocking cannot be disabled. • Callbacks from the PSAP may get blocked by the User Agent software. • Privacy settings might disclosure identity information, even if not desired. • Certain call features may not be supported either, such as REFER (for conference call and transfer to secondary PSAP) or GRUU. • User Agents will not convey location information to the VSP (even if available at the end host). • Only the emergency numbers configured at the VSP are understood. This may lead to cases where a dialed emergency number is not recognized. • Using the IP address to find the ISP is challenging and may, in case of mobility protocols and VPNs, lead to wrong results. • Privacy concerns might arise when a potentially large number of VSPs/ASPs are able to retrieve location information from an ISP. • It is likely that only authorized VSP/ASPs are allowed to be granted access. Unlikely to work across country boundaries. • Might require specific emergency services structure in order to work securely.

  16. Privacy & Security • Allowing other parties to retrieve location from an ISP raises authorization challenges. • BUT: Is the VSP really in need for location? • Interestingly enough only to a limited extend (at a country level) when there are not too many options to route calls exist. Examples: • A) Very small number of stage 1 PSAP cover the entire country (UK). • B) A single or a small number of ESRPs exist within the country that accept any call and routing happens within the ES network automatically. (e.g., Sweden and Lithuania). • C) VSP routes calls via the ISP (e.g., IMS, DT) • Learning the country where a specific host is located can be done based on IP-to-Location lookups. • With option (B) there are not necessarily changes to the emergency services systems necessary as the number of PSAPs may be left unchanged.

  17. Initial Upgrades to End Hosts Location Information Server Routing Database (3) (4) (0) Access Network Identifier or LbyR Location + Service Identifier PSAP URI (2) Location (1) (5) INVITE Request URI: urn:service:sos To: urn:service:sos INVITE Request URI: urn:service:sos To: urn:service:sos Route Header: PSAP URI < Reference to PIDF-LO> SIP Proxy dial 1-2-2 VSP PSAP / Call Taker

  18. Assumptions • End host detects emergency call (based on some pre-configured emergency numbers) • End host may implement additional emergency services features (e.g., disabling silence suppression). • End host learns the domain of the access network (for example using http://tools.ietf.org/html/draft-ietf-geopriv-lis-discovery-11) and may be able to obtain a LbyR via http://tools.ietf.org/wg/geopriv/draft-ietf-geopriv-dhcp-lbyr-uri-option/ or http://tools.ietf.org/wg/geopriv/draft-ietf-geopriv-http-location-delivery/. • VSP is either able to resolve the LbyR in order to route the call or to use the domain to query a LIS.

  19. (2) Location + Service Identifier (1) GPS Info Fully Upgraded End Device Location Information Server Routing Database • End host obtains location information necessary for call routing • End host uses LoST to learn locally available emergency numbers. It may also learn the PSAP URI but this function may also be provided by the VSP. (1) Location (3) PSAP URI + emergency number (4) (5) INVITE Request URI: urn:service:sos To: urn:service:sos Route Header: PSAP URI <PIDF-LO> INVITE Request URI: urn:service:sos To: urn:service:sos Route Header: PSAP URI <PIDF-LO> dial 1-2-2 SIP Proxy PSAP VSP (Note: This is a random IP device.)

  20. Characteristics • Locally available LoST servers improve reliability. LoST servers can, however, be deployed everywhere. • LoST servers provide dial string recognition • Local network characteristics (e.g., enterprise emergency network) can be considered using locally deployed LoST servers. • If connectivity to VSP does not work direct messaging to PSAP possible (assumes certain SIP profile).

  21. … subsequent slides talk about some of the components in more detail • Identifying an emergency call • Location • Format of location information • Protocols for obtaining location • Emergency Call Routing • Standardization of the emergency call procedures for SIP.

  22. Identifying an Emergency Call

  23. Emergency Numbers Emergency Numbers used worldwide, see http://www.sccfd.org/travel.html Emergency numbers vary in countries. Example: 9-1-1 for North America, 1-1-2 for Europe. Some countries use separate numbers for ambulance/police/fire; others don’t

  24. Service URNs • Emergency caller enters emergency dial string into the user interface • On the protocol level an emergency number independent scheme is desired to mark a call as an emergency call.  This lead to the work on Service URNs. Work done in the ECRIT working group: http://www.ietf.org/html.charters/ecrit-charter.html • Service URN registry established in http://tools.ietf.org/html/rfc5031 • Examples: urn:service:sos, urn:service:sos.ambulance, urn:service:sos.fire, urn:service:sos.poison, urn:service:sos.police

  25. Home and Visited Emergency Numbers • Required to support both home and visited emergency number • e.g., for an American traveler who is visiting Europe, both 9-1-1 and 1-1-2 should be recognized as emergency • How does the User Agent learn about emergency numbers: • Home Emergency Number: User can learn this number through LoST* or device configuration. • Visited Emergency Number: Obtained dynamically via LoST* (*): LoST is a protocol, more on later slides.

  26. Location

  27. Encoding of Location Information • The GEOPRIV WG http://www.ietf.org/html.charters/geopriv-charter.html uses two formats for location information encoding. • Binary Format • XML-based Format • For bandwidth constraint environments a functionality-reduced binary encoding is used (e.g., DHCP, link layer protocols) and for application protocols the XML encoding is preferred. • The XML encoding is based on the Presence Information Data Format (PIDF) for Location Objects (LO), or simply PIDF-LO. • PIDF-LO uses the Geography Markup Language (GML) developed by OGC for describing geodetic information.

  28. PIDF-LO: RFC 4119 • The Presence Information Data Format (PIDF) is an XML-based format for presence (RFC 3863) • A PIDF document contains identity information (as part of the ‘entity’ attribute). • Extends PIDF to accommodate new functionality: • <location-info> Element • Encapsulates location information • GML 3.0 <feature.xsd> schema (mandatory-to-implement) • Supports civic location format (optional-to-implement) • <method> Element • Describes the way location information was derived or discovered. • Example: <method>gps</method> • Registry available at: http://www.iana.org/assignments/method-tokens • <provided-by> Element • Entity or organization that supplied this location information • <usage-rules> Element • Used to indicate privacy preferences

  29. More on Civic Information • Initially civic location was specified for DHCP in RFC 4776* (http://www.ietf.org/rfc/rfc4776.txt) • RFC 4776 uses a binary format. • With RFC 4119* (PIDF-LO) for some of the RFC 4776 civic elements an XML encoding was specified. • With http://www.ietf.org/rfc/rfc5139.txt the document was revised and new civic tokens were added to be able to express addresses in Asia. • Note: Not every jurisdiction needs to make use of all civic tokens. An example of a profiling for Austria is described in http://tools.ietf.org/html/draft-ietf-geopriv-civic-address-recommendations *: Note that the content of RFC 4776 was developed before the work on PIDF-LO (RFC 4119). It was, however, faster to finish the standardization work on PIDF-LO.

  30. Location Shapes for Geodetic Info • Location determination techniques produce location information in different shape types. The specification uses the GML-based format for describing the shapes: http://tools.ietf.org/html/rfc5491 • The following location shapes are described: • Point (2d and 3d) • Polygon (2d) • Circle (2d) • Ellipse (2d) • Arc Band (2d) • Sphere (3d) • Ellipsoid (3d) • Prism (3d) • The document additionally makes a couple of simplifying restrictions (e.g., coordinate reference systems). • Finally, it also describes how PIDF-LO documents are created when location information from multiple sources is available. • Format is aligned with functionality provided by OMA and 3GPP specifications.

  31. Obtaining Location Information 1) Target has location information • Manual configuration or GPS (without help of the network) 2) Target wants to obtain location info from a LIS in theaccess network (see LCPs on subsequent slide) 3) Target obtains location from a location server in the user’s home network • OMA MLS/SUPL: http://tinyurl.com/6qdbxt 4) Location Server from 3rd Party Providers using Global Cell-ID database, BSSID database

  32. Location Configuration Protocols (LCPs) Location Information Server Target • Assumes that some entity in the access network knows the location of the Target. • LIS is topologically close to the Target. • Request from the Target to the LISneeds to contain identifier to lookup location information • Identifier will typically be the IP address • Protocol exchange may happen at different layers. E.g.: • HTTP in case of HELD • IP in case of DHCP • On top of the link layer but below IP (LLDP-MED) • Link layer Request Location Location

  33. LCPs, cont. • Link layer mechanisms (e.g., various extensions to IEEE link layer protocols) LLDP-MED • http://tinyurl.com/5eqlpq • http://tinyurl.com/5o3yxk • http://tinyurl.com/6hvag5 • DHCP (civic and geospatial) • RFC 4776 for civic location information (slides at http://tinyurl.com/6oj52t)http://www.ietf.org/rfc/rfc4776.txt • RFC 3825 for geodetic location information (slides at http://tinyurl.com/6jgchf) http://www.ietf.org/rfc/rfc3825.txt • Application Layer Location Configuration Protocol(e.g., HELD http://tools.ietf.org/html/draft-ietf-geopriv-http-location-delivery) • OMA MLS/SUPL: http://tinyurl.com/6qdbxt

  34. Location by Reference • Previous slides describe how location can be passed around per value. • But there are examples when this is not desired. • E.g., when location frequently changes • Solution approach: • Instead of retrieving location information per value a reference is obtained. • This reference can be resolved to a location object (more than once) and may yield to fresh location • Access control can also be enforced. • The reference plays the role of a privacy-enhancing generalized identifier.

  35. Architecture Location Information Server • Examples: • sips:9769+357yc6s64ceyoiuy5ax3o@ls.example.com • https://ls.example.com:9768/357yc6s64ceyoiuy5ax3o Location Reference Location Information Location Reference Request SIP, HTTP, etc. + Location Reference Location Recipient User Agent(or proxy)

  36. Identifier Extensions • HELD allows the source IP address of the HELD request to be used for the location lookup. • Sometimes more flexiblity with regard to the identifier choice is needed  „HELD Identity Extensions“ Document: http://tools.ietf.org/id/draft-ietf-geopriv-held-identity-extensions • Typical usage: • LIS-to-LIS communication scenarios (in DSL wholesale environments) http://tools.ietf.org/html/draft-winterbottom-geopriv-held-lis2lis-bcp • SIP proxy-to-Location Server communication

  37. Request location for IP address 10.162.93.203 Request location for VCI/VPI xyz. (2a) (2a) PSAP / Call Taker (2b) (2b) Location Location Example IAP LIS ISP LIS (1) (5) INVITE Request URI: urn:service:sos To: urn:service:sos INVITE Request URI: urn:service:sos To: urn:service:sos Route Header: PSAP URI <Location Reference> SIP Proxy VSP dial 1-1-2 Target (Emergency Caller)

  38. De-Referencing • The Location Recipient obtains the URI and needs to resolve it to location information. • Dereferencing protocol depends on the URI scheme: • SIP Subscribe / Notify (in case of a SIP URI) • HTTP (in case of HTTP URI) (+ secure versions being used; HTTPS and SIPS) • Best current practice document for HTTP-based Location URIs: • http://tools.ietf.org/id/draft-winterbottom-geopriv-deref-protocol • Provides polling capabilities • For SIP the SIP presence event package is used to obtain location information • Offers also asynchronous notifications ( next slide)

  39. Rate Limiting Asynchronous Notifications of SIP • When location may change regularly then it is useful to restrict the number of asynchronous notifications being sent. • SIP offers asynchronous message (with the PubSub concept) and a SUBSCRIBE message may contains rate limiting filters. • Document is available with: http://tools.ietf.org/wg/geopriv/draft-ietf-geopriv-loc-filters/ • Features: • Object moves more than a specific distance horizontally or vertically since the last notification • Object exceeds a specific speed • Object enters or exits pre-defined regions • one or more of the values of the specified address labels has changed • Reduction of the rate at which messages that are being sent.

  40. Emergency Call Routing

  41. Finding the closest PSAP Location Information Emergency Number + + Service URN Service URN + (PSAP) URI + Location-to-Service Translation (LoST) is an XML-based query and response protocol running on top of HTTP. Service Boundary

  42. Features • Protocol specification available with • http://tools.ietf.org/html/rfc5222 • Satisfies the requirements for mapping protocols: • http://tools.ietf.org/html/rfc5012 • Provides civic address validation • Returns XML tag names of components (classified into <valid>, <invalid> and <unchecked>) • Offers recursive and iterative query resolution • Service boundary may be returned via reference or by value. • Functionality for listing available service URNs and listing service URNs per location. • Supports extensible location profiles. Currently 2 profiles are available: • geodetic-2d (offers Point, Polygon, Circle, Ellipse, ArcBand) • civic (based on http://tools.ietf.org/html/rfc5139)

  43. From a Protocol to an Architecture • LoST is a protocol that runs between a LoST client and a LoST server. • Not sufficient when calls from anywhere need to find their way to the right PSAP. • RFC 5582 describes a global mapping architecture using LoST. • Unlike DNS it does not require a single root. There are many root elements and they synchronize their mappings, for example, using http://tools.ietf.org/html/draft-ietf-ecrit-lost-sync • Like DNS it has redundancy mechanisms built-in • LoST is a core building block for the NENA i3 architecture, see http://tinyurl.com/63dvs4 • There are multiple ways to deploy LoST. LoST deployment needs country-specific profiling to historical deployment differences and other preferences. Example questions: • Who runs authoritative LoST servers? Who runs caches? • Who is allowed to put mapping data into the LoST server? • Who is allowed to access LoST servers? • How many LoST servers are needed? Is there a synchronization between them?

  44. LoST Architecture, cont. • Does not require support from the ISP/IAP • But leaves the option to do so • Dynamic LoST server discovery procedure available: • via DNS (defined in http://tools.ietf.org/html/rfc5222) • Via DHCP (defined in http://tools.ietf.org/html/rfc5223) • Open Source code to play with: • Pointer to code from Columbia University - http://www.tschofenig.priv.at/wp/?p=486

  45. Leaf Node Leaf Node Leaf Node Tree Node Tree Node Leaf Node Terminology FG Forest Guide FG FG FG T3 (.at) FG T1 (.us) Resolver T2 (.de) seeker Tree Tree Tree

  46. Terminology • Seekers: Consumers of mapping data and may cache responses. Don’t act as servers. • Resolvers: Know how to contact FGs and tree nodes. May cache results. Does not have authoritative mappings configured. • Forest Guide: Knows about the coverage region of all trees. Do not provide mapping data themselves. Redirects only to tree nodes. • Tree Node: Maintains mapping data and coverage regions. Knows about the coverage region of all its child nodes. • Leaf Nodes only maintain mapping data. No coverage region data. • From an implementation point of view: • Coverage Region: • Maintains {PSAP Boundary & Service URN LoST server URI} mappings • Mapping Data: • Maintains {PSAP Boundary & Service URN  PSAP URI } mappings

  47. Example broadcast (gossip) FG FG FG FG T1: .us T2: .de FG resolver T2 (.de) seeker 313 Westview Leonia, NJ US T3 (.at) T1 (.us)

  48. Example • When query hits T1 tree then it finally travels to a node that knows about the LoST servers responsible for New Jersey: • C A1 A2 A3 LoST server name • US NJ Atlantic * atlantic.nj.example.org/sos • US NJ Bergen * bergen.nj.example.org/sos • US NJ Monmouth * monmouth.nj.example.org/sos • US NJ Essex * essex.nj.example.org/sos • US NJ Essex Newark newark.example.com/sos • .... • The LoST server at bergen.nj.example.org then contains the following data: • country A1 A2 A3 PSAPs and further LoST servers • US NJ Bergen Leonia sip:psap@leonianj.gov • US NJ Bergen Fort Lee sip:emergency@fortleenj.org • US NJ Bergen Teaneck sip:police@teanecknjgov.org • US NJ Bergen Englewood englewoodnj.gov • ….

  49. Standardization of the emergency call procedures for SIP.

  50. IETF-based Emergency Call Procedure • The architecture describes the final envisioned emergency services deployment. • This particularly refers to the sharing of responsibilities (end host, VSP, ISP). • The relevant documents are: • http://tools.ietf.org/wg/ecrit/draft-ietf-ecrit-framework/ • http://tools.ietf.org/wg/ecrit/draft-ietf-ecrit-phonebcp/ • These documents ALSO describe the VSP-to-PSAP interaction. • draft-ietf-ecrit-phonebcp makes use of the Service URN and SIP Location Conveyance http://tools.ietf.org/wg/sip/draft-ietf-sip-location-conveyance/ as protocol mechanisms.

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