911 services: wireline, wireless and VoIP Prof. Henning Schulzrinne Dept. of Computer Science Columbia University, New York FCC Solutions Summit March 18, 2004
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911 services: wireline, wireless and VoIP Prof. Henning Schulzrinne Dept. of Computer Science Columbia University, New York FCC Solutions Summit March 18, 2004 Overview E911 for wireline E911 for wireless (Phase II) Short-term 911 service for VoIP Differences between PSTN and VoIP Objectives Internet standardization efforts Components of emergency calling Three core components that need to be replicated – everything else are implementation details 1. 2. identifying emergency calls (“911”) determining the right PSAP for current caller location 3. coarse-grained location currently, ALI and MSAG deliver caller location to PSAP fine-grained location E911 for wireline CAMA or SS7 555-1234 313 Main St CO Switch LEC network PSAP #1 CAMA or PRI delivers ANI (555-1234) Tandem Switch (911 Selective Router) 555-1234 PSAP #1 MSAG ANI: 555-1234 313 Main ALI 100-500 Main Street ESN 1789 private data link 555-1234 PSAP #1, 313 Main St provisioned updates verify address validity Wireless 911 Phase I (April 1998) Route all call to the appropriate PSAP based on call sector Provide cell/sector location data to PSAP Provide call back number to PSAP Phase II (October 2001) Phase I + latitude and longitude 67% 95% handset 50m 150m network 100m 300m Wireless 911: Phase 2 MSC pANI (ESRD or ESRK) ISUP r s i l t r i y N et LEC selective router Wireless Tower PDE MPC/SCP E2 S A-GPS, UTDOA, … t w .a p dynamic updates .c o ESRK = unique for call ESRD = unique for location ALI ESRK or ESRD coordinates callback number Problems with existing 911 system 1970s technology: gets complicated if multiple providers CAMA trunks induce long call setup delays limited in ability to transfer information (10 digits) ILEC vs. CLEC multiple wireless providers tied to ILEC rate centers and other PSTN routing artifacts hard to move PSAPs on short notice (e.g., emergency evacuation) can’t just plug into any network termination PSTN vs. Internet Telephony PSTN: Signaling & Media Internet telephony: Signaling & Media China Signaling Signaling Media Belgian customer, currently visiting US Australia How does VoIP differ from landline and wireless PSTN? Telephone companies are no longer needed new location, but same identifier there are still carriers for DSL and cable “IP dial tone” but unaware of type of data carried (voice, web, IM, …) VSP may be in another state or country Corporations and universities don’t have email carriers, either Yahoo voice service provider MCI All devices are nomadic ISP (IP) NYSERNET dark fiber provider (λ) (TCP, RTP, SIP) The role of phone numbers and identifiers Wireline line, device, subscriber & location Wireless device, but not location VoIP (phone number and URIs): mostly identifies person, not device multiple devices located in different states can share the same number however, may not have a phone number if it does, area code may be from different state than customer billing address multiple devices device can move, while number stays the same not related to ISP Why is VoIP ≠ wireless? VoIP devices may not have phone numbers as lookup keys e.g., sip:[email protected] Location information for devices is civil, not longitude/latitude e.g., service address for VSPs GPS not available (nor functional) on indoor devices Cell phones don’t work in our building… plus, accuracy of 50 m (67%) or 150 m spans many buildings… no floor information so A-GPS is unlikely to work there, either Plus, wireless E911 complexity due to old signaling mechanism expensive and complicated to connect to multiple wireless operators proposals to use IP-based solutions 50m Objectives for IP-based 911 International Multimedia integrity, privacy and confidentiality, protection against denial-of-service attacks Technology-independent users can test operation without tying up operator resources Secure easily re-route calls to any number of backup PSAPs Testable re-use standard protocols (SIP, DNS, DHCP, HTTP, XML, …) avoid repeat of CAMA trunks Resilient integrate alternate modalities such as text (TDD) and video (sign language) COTS devices must work anywhere independent of local emergency number international roaming do not depend on (e.g.,) specific wireless or link technology Pro-competitive does not require carriers or gatekeepers Three stages to VoIP 911 when deployable ? use 10digit admin. number? mobility caller location conveyed to PSAP? PSAP modification ALI (DB) modification new services I1 now allowed stationary no no no none I2 December 2004 no stationary nomadic yes no (10-digit) yes none I3 specified by late 2004 no stationary nomadic mobile yes IP-enabled replaced by DNS GNP multimedia international calls Example I1 solution #1 SS7 CLEC #1 Example: VoxPath End Office Switch LAN IP Phone Customer Signaling Gateway PSAP Softswitch Broadband Network Media Gateway End Office Switch Selective Router 1 2 3 4 5 6 7 8 9 * 8 # Call Taker POP CLEC #2 Mark Lewis I1 Solution #2 Level3 Customer Softswitch Dedicated 911 trunks PSTN E911 Tandem End Users Public Internet or Private IP Network E911 Tandem IP Phones ALI DB PBX (emergency lines) Level 3 911 Softswitch Network ACD PSAP Mark Lewis Possible I2 architecture IP INVITE sos PSTN MG Selective Router ISUP CAMA ESRK, DN loc ALI SIP PUBLISH ALIFE E2+ ESP PAM Local ALI National Voice N/Ws Emergency Services N/W based on slide by Martin Dawson IETF I3 standardization efforts IETF = Internet Engineering Task Force = international open standardization body “911” sip:sos@ include civil and/or geo 911 sos 112 sos sip:[email protected] provide location (civil or geo) DHCP cn=us, a1=nj, a2=bergen Conclusion Existing 911 system closely tied to PSTN history number as universal identifier close affiliation with PSTN switches incremental, constrained evolution VoIP offers opportunity to increase robustness and decrease costs Initial international and US standardization efforts in progress IETF and NENA collaboration combines 911 and Internet expertise