NG911 project status

Henning Schulzrinne(with Jong Yul Kim, Wonsang Song, Anshuman Rawat, Matthew Mintz-

Habib, Amrita Rajagopal and Xiaotao Wu)

Dept. of Computer ScienceColumbia University

NG911 project meeting (College Station, February 2006)

Options for location delivery• GPS• L2: LLDP-MED (standardized version of CDP + location

data)– periodic per-port broadcast of configuration

information– currently implementing CDP

• L3: DHCP for– geospatial (RFC 3825)– civic (draft-ietf-geopriv-dhcp-civil)

• L7: proposals for retrievals– for own IP address (draft-linsner-geopriv-lcp)

– by IP address– by MAC address– by identifier (conveyed by DHCP or PPP)

NG911 project meeting (College Station, February 2006)

Phase 3 : Routing to Correct PSAP

NG911 project meeting (College Station, February 2006)

IETF ECRIT working group• Emergency Contact Resolution with Internet Technologies• Solve four major pieces of the puzzle:

– location conveyance (with SIPPING & GEOPRIV)– emergency call identification– mapping geo and civic caller locations to PSAP– discovery of local and visited emergency dial string

• Not solving– location discovery– inter-PSAP communication and coordination– citizen notification

• Current status:– finishing general and security requirements– tentative agreement on mapping protocol and identifier– later, to work on overall architecture and UA requirements

NG911 project meeting (College Station, February 2006)

Emergency identifier requirements• Direct user interface, without “dialing” number

– but do NOT require user to input this identifier directly

– i.e., separate user interface from protocol identifier!

• Reach emergency help in any country, without knowledge of local numbers– also, universally recognizable by proxies

regardless of location of caller• Deployable incrementally

– even if not all entities support the mechanism• Testable without impacting PSAP (human)

resources

NG911 project meeting (College Station, February 2006)

Defining an (emergency) services URN• URN = universal resource name

– identifies resource, not its network location– translated by protocol (e.g., DNS) into location(s)

• New: service URN urn:service:service• Identifies a generic service, not a specific resource• Uses mapping protocol:

– {identifier, location} URL(s)• Can be used anywhere a URN or URL is allowed, e.g.:

– web pages– result returned by mapping protocol– request and To URI in SIP

• For emergency services:– urn:service:sos, urn:service:sos.fire, urn:service:sos.police,

urn:service:sos.marine, urn:service:sos.mountain, urn:service:sos.rescue, urn:service:sos.poison, urn:service:sos.suicide, urn:service:sos.mental-health

• Could also be used for other services: urn:service:directory

NG911 project meeting (College Station, February 2006)

UA recognition & UA resolution

INVITE sip:psap@leonianj.govTo: urn:service:sos

<location>

9-1-1(dial string)

mapping

INVITE sip:psap@leonianj.govTo: urn:service:sos

<location>

leonianj.gov

mapping may recurse

location information

DHCPLLDP-MED

NG911 project meeting (College Station, February 2006)

UA recognition & proxy resolution

9-1-1

mapping

INVITE urn:service:sosTo: urn:service:sos

<location>

INVITE sip:psap@leonianj.govTo: urn:service:sos

<location>

provider.com

NG911 project meeting (College Station, February 2006)

UA recognition & proxy resolution(proxy location determination)

9-1-1

mapping

INVITE urn:service:sosTo: urn:service:sos

INVITE sip:psap@leonianj.govTo: urn:service:sosLocation: <location>

provider.com

NG911 project meeting (College Station, February 2006)

Proxy recognition & proxy resolution

9-1-1

mapping

INVITE sip:911@provider.com;user=phoneTo: sip:911@provider.com;user=phone

INVITE sip:psap@leonianj.govTo: sip:911@provider.com;user=phoneLocation: <location>

provider.com

NG911 project meeting (College Station, February 2006)

Phase 1 & 2 : Identifying Emergency Calls & Determining Caller Location

NG911 project meeting (College Station, February 2006)

DHCP for locations

• modified dhcpd (ISC) to generate location information• use MAC address backtracking to get location information

DHCPserver

DHCP answer:0:US:1:CA:2:LOS ANGELES:3:LONG BEACH:6:HYATT AVE:19:300

DHCPINFORM00:11:20:9d:a0:03

NG911 project meeting (College Station, February 2006)

DHCP for locations (cont.)

# ip_phone 1host sip0011209da003 { next-server ng911serv.irt.cs.columbia.edu; hardware ethernet 00:11:20:9d:a0:03; fixed-address 128.59.17.59; option tftp-server-name "128.59.19.174"; option host-name "sip0011209da003";#0:US:1:CA:2:LOS ANGELES:3:LONG BEACH:6:HYATT AVE:19:300option loc-civil

55:53:2:1:2:43:41:2:b:4c:4f:53:20:41:4e:47:45:4c:45:53:3:a:4c:4f:4e:47:20:42:45:41:43:48:6:9:48:59:41:54:54:20:41:56:45:13:3:33:30:30;

}

dhcpd.conf

NG911 project meeting (College Station, February 2006)

Emergency dial strings• ~60 different dial strings in use

– some countries separate fire/police/…, others don’t

– some are used for other services• PBX, information, prefix, …

• Needs to support both home and visited dial string when traveling

• Home = dial string at home location of traveler– traveler may not know local conventions

• Visited = dial string at visited location– fellow tourist picks up phone– babysitter in ex-pat household

• Configure– via DHCP– via SIP configuration mechanism– via location mapping

NG911 project meeting (College Station, February 2006)

LUMP: Mapping service URNs + locations to URLs

• Common problem:– {geo or civic location, service} set of URLs– e.g., {Broadway/NY, “911”} fire@psap.nyc.gov– also applies to anything from towing service to pizza delivery

• Need to be able to validate addresses ahead of emergency– does this street address resolve to a PSAP?– can the ambulance find the address?

• Service providers don’t trust each other (fully)– e.g., who gets to include Jerusalem in its map– service may depend which warlord you belong to – can’t wait for UN (or ICANN) to create global emergency

services database• Suggested approach: new distributed mapping protocol

– LUMP: location-to-URL mapping protocol– uses SOAP, but special service URLs

NG911 project meeting (College Station, February 2006)

LUMP: overview• Support global-scale resolution of service

identifiers (e.g., service URNs) + locations to other URLs

• Attempts to be reliable and scalable– borrow concepts, but not protocol

limitations, from DNS• Architecture: “Forest of trees with a cloud

above”– avoid root as only deployment alternative

• Uses standard web services building blocks

NG911 project meeting (College Station, February 2006)

LUMP: Location-to-URL Mapping

clusterserves VSP2

NYUS

NJUS

Bergen CountyNJ US

123 Broad AveLeoniaBergen CountyNJ US

cluster serving VSP1

replicateroot information

searchreferral

rootnodes

LeoniaNJ US

sip:psap@leonianj.gov

VSP1

NG911 project meeting (College Station, February 2006)

LUMP architecture

T1

(.us)

T2

(.de) T3

(.dk)

G

G

GG

G broadcast (gossip)T1: .us

T2: .de

resolver

seeker313 Westview

Leonia, NJ US

Leonia, NJ sip:psap@leonianj.gov

tree guide

NG911 project meeting (College Station, February 2006)

Caching• Generally, UA caches lookup results

– query: “I’m at (X,Y), what’s my PSAP?”– answer: “Your PSAP is sip:psap@town.gov as long as you stay

in polygon (X1,Y1; X2, Y2; …); this is valid for 12 hours”• almost no impact of node mobility on query frequency

– same for civic: “as long as you stay on Main Street, your town”• civic only relevant for nomadic users

– actual PSAP coverage area may be larger just an optimization

• Almost always avoids query during emergency call– MAY re-query during call– load distribution via DNS

• given frequency of calls for one resolver, likely to be no DNS caching anyway

• Further optimization: query with timestamp (or etag) of last answer– answer: “still the same, thanks for asking”

NG911 project meeting (College Station, February 2006)

Performance notes• US: only about 6 calls/second for whole country

– on average, but may spike during mass casualty events

• Use TCP (or TCP/TLS) for reliability• Expect 1-2 queries/day/client• Typical: >> 100 queries/second/server

– almost all rows will be cached in memory•only about 6,000 rows

– one server 8,640,000 queries– probably N+1 spared– data center cost: $300/month/server

$0.0003/user/month (1Mq/day)

NG911 project meeting (College Station, February 2006)

Implementation status• Prototype

implementation at Columbia University:– includes referrals– both geo and civic

coordinates– from draft WSDL

(with minor fixes)• Server

– Axis (Apache) SOAP server

– Postgres SQL geo database

• does polygon intersection

• Client– Java app (web page)– Tcl (for our SIP client)

NG911 project meeting (College Station, February 2006)

LUMP geo mapping

NG911 project meeting (College Station, February 2006)

LUMP: SOAP request

NG911 project meeting (College Station, February 2006)

Calltaker Routing

• Using SIP caller preferences/callee capabilities– Example: caller language preference

• automatically route to call taker who speaks French

•Accept-Language: fr

NG911 project meeting (College Station, February 2006)

Phase 4 : Call Presentation

Call Taker 1

Call Taker 2

Call Taker n

Hospital Police Fire Envinsa Server

HTTP SOAPTelephone #

Location Info

psap@domainw/location

Controller (psapd)

Policy

Conference Mixer

selectavailable calltaker

createconference

INVITE toconference

joinconference

REFER PoliceTo conference

joinconference

(1)

(3)(2)

(4)

(5)

(6a)

(6b)

(8)

(7)

INVITE toconference

NG911 project meeting (College Station, February 2006)

caller psapd conf.server

call taker

(2) INVITE calltaker(loc, no SDP)

(1) INVITE psap(loc, SDP1)

(4) INVITE calltaker conf.(no loc, SDP2)

(5) 200 OK(SDP2')

(7) ACK(SDP2')

(6) ACK

(8) media

(9) INVITE caller conf.(no loc, SDP1)

(10) 200 OK(SDP1')

(11) 200 OK(SDP1')

(12) ACK

(13) ACK

(14) media

(15) sos call established

(3) 200 OK(SDP2)

180 Ringing

180 Ringing

Controller (psapd) Flow

NG911 project meeting (College Station, February 2006)

PSAP interface

using GeoLynx or Google Maps as “GIS”

NG911 project meeting (College Station, February 2006)

Ongoing work (Spring 2006)• Track LUMP specification• SIPc

– DHCP support– DB for CDP– Call history window for call back– Determine if call dropped without

normal termination messaging– Call taker blocking others from call

• SIPc + psapd– Emergency number determination– Civic address validation using MSAG

• psapd– Transfer to another psapd– TLS support and testing

• Other– Video push– sipd must handle “486 Busy” from

psapd– Assign unique number to each

incident– Associate multiple calls with an

incident

•System-wide– Pre-determined limit of

simultaneous calls– Incoming Call Queue at the

option of the PSAP• Incident specific

announcements• Prioritize calls in queue

– Overflow calls to designated backup IP PSAP• Indications of overflow for

originating and destination PSAP

– Adding information in PIDF-LO– Call taker re-bids location

information• Caller updates location

information• Re-routing calls when

location changes• Interaction with external elements

– TDD support

NG911 project meeting (College Station, February 2006)

Conclusion• IETF ECRIT working group converging on set of

solutions– mapping protocol– emergency identifier– location conveyance– to be done: UA requirements

• Demo implementation of LUMP• Multi-call taker PSAP approximation• Working on solving core I3 & PSAP requirements from

NENA documents