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  • 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
  • Transcript

    • 1. 911 services: wireline, wireless and VoIP Prof. Henning Schulzrinne Dept. of Computer Science Columbia University, New York [email_address] VoIP Roundtable, Washington, DC June 24, 2004
    • 2. Overview
      • E911 for wireline
      • E911 for wireless (Phase II)
      • Differences between phone system and VoIP
      • Requirements and opportunities
      • Internet standardization efforts
      • Funding and regulation challenges
    • 3. Components of emergency calling
      • Three core components that need to be replicated – everything else are implementation details
        • identifying emergency calls (“911”)
        • determining the right emergency call center (PSAP) for current caller location
          • coarse-grained location
          • currently, two main databases: ALI for number-to-location mapping and MSAG for address verification
        • deliver caller location to PSAP
          • fine-grained location
    • 4. E911 for wireline LEC network 555-1234 313 Main St ALI MSAG 100-500 Main Street  ESN 1789 555-1234  PSAP #1, 313 Main St CAMA or PRI delivers ANI (555-1234) CAMA or SS7 ANI: 555-1234  313 Main 555-1234  PSAP #1 PSAP #1 verify address validity provisioned updates private data link CO Switch Tandem Switch ( 911 Selective Router )
    • 5. 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
      300m 100m network 150m 50m handset 95% 67%
    • 6. Wireless 911: Phase 2 y N e t r s r t i i l S t w . a p . c o Wireless Tower ALI PDE A-GPS, UTDOA, … MPC/SCP ESRK or ESRD  coordinates callback number pANI (ESRD or ESRK) ISUP LEC selective router MSC E2 ESRK = unique for call ESRD = unique for location dynamic updates
    • 7. Problems with existing 911 system
      • 1970s technology:
        • CAMA trunks induce long call setup delays
        • limited in ability to transfer information (8-10 digits)
        • sometimes, 2,400 baud modems for database access
          • increases call setup delays
      • gets complicated if multiple providers
        • ILEC vs. CLEC
        • multiple wireless providers in one state
      • 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
    • 8. PSTN vs. Internet Telephony Signaling & Media Signaling & Media Signaling Signaling Media PSTN: Internet telephony: China Belgian customer, currently visiting US Australia
    • 9. 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
        • anybody can be their own “VSP”
      • Corporations and universities don’t have email carriers, either
      voice service provider [VSP] (TCP, RTP, SIP) ISP (IP, DHCP) dark fiber provider ( λ ) Yahoo MCI NYSERNET
    • 10. 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
    • 11. Why is VoIP ≠ wireless?
      • VoIP devices may not have phone numbers as lookup keys
        • e.g.,
      • 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
    • 12. Objectives for IP-based 911
      • International
        • devices must work anywhere
        • independent of local emergency number
        • international roaming
      • Multimedia
        • integrate alternate modalities such as text (TDD) and video (sign language)
      • COTS (commercial off-the-shelf)
        • re-use standard protocols (SIP, DNS, DHCP, HTTP, XML, …)
        • 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, privacy and 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
    • 13. Opportunities for I911
      • More robust
        • multiple networks and interfaces increase disaster resiliency
        • operations can be moved easily to any network-connected location
      • Additional services
        • multimedia
          • text chat replacing TTY
          • video and images for situational awareness and instructions to civilians at scene of accident
        • additional data
          • hazmat data
          • accident data (impact velocity, airbags, fuel spill, …)
      • Better integration with first responders and public safety
        • integration with telematics providers
        • general awareness of call volume, origin and type
        • information flow back to PSAP
          • see 9/11 evacuation
        • hand off call data, not just remote printing of address
        • alerts and notifications to public safety and the public
      • Cheaper to build and operate
        • currently, small niche  expensive equipment, specialized circuits, slow upgrades
        • should be able to leverage almost existing technology  lower risk
    • 14. Three stages to VoIP 911: I1  I2  I3
      • I1:
        • may use administrative line to deliver call
        • no location delivery
      • I1 & I2:
        • no modification to PSAP
        • calls delivered to PSAP via existing technology
        • delivers location information
      • I3:
        • deliver calls to PSAP via VoIP
        • including circuit-switched calls
      • I1, I2 and I3 will likely co-exist for some time
        • design to allow local upgrades, without national or state-wide coordination
    • 15. Three stages to VoIP 911 IP-enabled no (10-digit) no PSAP modification global number portability multimedia international calls replaced by DNS yes stationary nomadic mobile no specified by late 2004 I3 none yes yes stationary nomadic no December 2004 I2 none no no stationary allowed now I1 new services ALI (DB) modification caller location conveyed to PSAP? mobility use 10-digit admin. number? when deployable?
    • 16. IETF and NENA I3 standardization efforts
      • IETF = Internet Engineering Task Force = international open standardization body
      provide location (civil or geo) include civil and/or geo sip:sos@ “ 911” 911  sos 112  sos cn=us, a1=nj, a2=bergen DHCP
    • 17. Regulatory challenges
      • Uniform technology
        • but avoid things that don’t work internationally
      • Distributed responsibility:
        • VSP does not know location
        • Residential user may have any number of VSPs
          • like prepaid calling cards
          • and may use any one of them for calling 911
        • ISP does not know VSP and whether call is voice or not
        •  ISP needs to provide location information to end user  regulatory mandate!
    • 18. Funding challenges
      • Existing line/number model does not work
        • longer term, no more “lines” and numbers
        • every person may have multiple identifiers
      • Short-term vs. long-term options
      • Even small VSPs have a national footprint
        • number assigned may not match location of customer
          • VoIP has built-in global number portability
        • can’t require to keep track of 6,000 different county 911 fees and recipients
      • Funding collector should
        • have direct customer relationship
        • know accurately where customer lives
        • have regional footprint
        • have modest collection and distribution costs
      • Some options:
        • facilities-based (broadband) ISP
        • local & state taxes
        • non-telecom utilities (water, gas, electric) that reflect residency
        • collect directly from household
          • like home owners insurance
    • 19. Conclusion
      • Existing 911 system closely tied to phone system history
        • number as universal identifier
        • close affiliation with telephone switches
        • incremental, constrained evolution
      • VoIP offers opportunity to increase robustness, offer new services and decrease costs
      • Initial international and US standardization efforts in progress
        • IETF and NENA collaboration combines 911 and Internet expertise
      • Initial prototypes and demonstration systems in development
    • 20. Additional I1 and I2 information
    • 21. Example I1 solution #1 Mark Lewis Broadband Network LAN IP Phone End Office Switch SS 7 End Office Switch Selective Router PSAP Media Gateway Signaling Gateway Softswitch Customer POP CLEC # 1 CLEC # 2 Call Taker Example: VoxPath 1 2 3 4 5 6 7 8 9 * 8 #
    • 22. I1 Solution #2 Customer Softswitch PSTN E911 Tandem IP Phones PSAP End Users Level 3 911 Softswitch Network Dedicated 911 trunks Public Internet or Private IP Network E911 Tandem Mark Lewis Level3 ALI DB ACD PBX (emergency lines)
    • 23. Possible I2 architecture Selective Router ALI ALI Local National PAM CAMA Emergency Services N/W Voice N/Ws IP ISUP E2+ ESP ALI-FE PSTN based on slide by Martin Dawson MG SIP PUBLISH ESRK, DN  loc INVITE sos