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 identifying emergency calls (“911”) determining the right PSAP for current caller location coarse-grained location currently, ALI and MSAG deliver caller location to PSAP fine-grained location

E911 for wireline MSAG ALI verify address validity PSAP #1 CAMA or PRI delivers ANI (555-1234) CO Switch CAMA or SS7 Tandem Switch (911 Selective Router) 555-1234 313 Main St LEC network 555-1234  PSAP #1 ANI: 555-1234  313 Main MSAG ALI private data link 100-500 Main Street  ESN 1789 555-1234  PSAP #1, 313 Main St provisioned updates verify address validity

Wireless 911 Phase I (April 1998) Phase II (October 2001) 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 pANI E2 ALI ESRK or ESRD  coordinates MSC pANI ISUP y N e t r s i r l i t LEC selective router Wireless Tower PDE MPC/SCP E2 ALI A-GPS, UTDOA, … S dynamic updates t ESRK or ESRD  coordinates callback number w . a p . c o ESRK = unique for call ESRD = unique for location

Problems with existing 911 system 1970s technology: CAMA trunks induce long call setup delays limited in ability to transfer information (10 digits) gets complicated if multiple providers 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 Signaling & Media Signaling & Media China Internet telephony: With a few exceptions, in Internet telephony, end systems are the only entities where signaling and media flows converge. Thus, any service that requires interaction with user media is likely to be easier to implement in the end systems. More seperately Signaling Signaling Media Belgian customer, currently visiting US Australia

How does VoIP differ from landline and wireless PSTN? All devices are nomadic new location, but same identifier Telephone companies are no longer needed 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 voice service provider (TCP, RTP, SIP) Yahoo ISP (IP) MCI dark fiber provider (λ) NYSERNET

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:hgs@cs.columbia.edu Location information for devices is civil, not longitude/latitude e.g., service address for VSPs GPS not available (nor functional) on indoor devices plus, accuracy of 50 m (67%) or 150 m spans many buildings… no floor information Cell phones don’t work in our building… 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 devices must work anywhere independent of local emergency number Multimedia Integrate alternate modalities such as text (TDD) and video (sign language) COTS avoid repeat of CAMA trunks Resilient easily re-route calls to any number of backup PSAPs Testable users can test operation without tying up operator resources Secure integrity, confidentiality, protection against denial-of-service attacks Technology-independent do not depend on (e.g.,) specific wireless or link technology Pro-competitive does not require carriers or gatekeepers

VoIP and 911 – Two stages Short term: Longer term: work with existing PSAPs may not support nomadic devices Longer term: upgrades in PSAP CPE opportunity for improved overall architecture support nomadic devices support multimedia provide framework for simpler & cheaper circuit-switched landline and wireless architecture

Short-term solutions Emulate wireline Emulate wireless every subscriber has phone number capture VoIP subscriber address and enter into ALI DB gateway calls 10-digit number and provides ANI Emulate wireless VoIP provider = another wireless carrier use similar dynamic updates for ALI DB

IETF standardization efforts IETF = Internet Engineering Task Force = international open standardization body “911” sip:sos@ include civil and/or geo 911  sos 112  sos sip:psap@leonia.nj.gov 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 standardization efforts in progress