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NG911 technology. Henning Schulzrinne What is NG911 technically? (One-slide version). Successor (replacement) for circuit-switched technology Same user interface (dial 9-1-1), different back end Internet protocols (IP)

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Ng911 technology l.jpg

NG911 technology

Henning Schulzrinne

What is ng911 technically one slide version l.jpg
What is NG911 technically? (One-slide version)

  • Successor (replacement) for circuit-switched technology

  • Same user interface (dial 9-1-1), different back end

    • Internet protocols (IP)

    • COTS technology: IP, RTP, SIP, XML, HTTP, …

    • Location information generated locally at terminal

      • GPS or network-based information

    • Full support of stationary, nomadic and mobile devices

    • Any number of media streams, with dynamic addition and deletion

    • Capability-based call routing (e.g., language, media capabilities)

      • e.g., supports American Sign Language as language tag


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IETF and NENA standards

  • “phone BCP” (draft-ietf-ecrit-phonebcp-16)

  • PSAPs MUST support RTT and video:

    • BCP: ED-76 Endpoints supporting real-time text MUST use [RFC4103]. The expectations for emergency service support for the real-time text medium are described in [RFC5194], Section 7.1.

    • It must be possible to place an emergency call using ToIP and it must be possible to use a relay service in such a call. The emergency service provided to users utilising the real-time text medium must b equivalent to the emergency service provided to users utilising speech or other media.A text gateway must be able to route real-time text calls to emergency service providers when any of the recognised emergency numbers that support text communications for the country or region are called, e.g., "911" in the USA and "112" in Europe. Routing real-time text calls to emergency services may require the use of a transcoding service.A text gateway with cellular wireless packet-switched services must be able to route real-time text calls to emergency service providers when any of the recognized emergency numbers that support real-time text communication for the country is called.


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Real-Time Text

  • RTT refresher:

    • (typically) one character at a time

    • immediate upon entry

    • bi-directional (full duplex)

  • Technology: RFC 4103 (Internet standard)

    • support international characters (e.g., Chinese or Russian)

  • Just another media session in SIP session

  • Negotiated by both sides

    • Caller: “I support real-time text”

    • Callee: “Great – so do I”


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Video in NG911

  • Allow calls directly to PSAP

  • Bridge in VRS

 receive call: video + sign language

 add VRS to call (dial-out)

MCU (conference bridge)


use normal NG911 call routing


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  • SMS as transitional technology

  • Challenges:

    • SMS is not reliable (but better than nothing)

    • Delivery can be delayed

    • SMS don’t include caller location information

    • SMS are datagrams  need to maintain session to same call taker

  • Requirements:

    • All wireless carriers need to implement N11 routing

    • If indirect, gateway providers would need to upgrade protocols

    • Phone number to location mapping or in-band protocol

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(no information about carrier or location)

Needs to be upgraded

could insert location


entity (ESInet)


can get lost

or delayed

SMS don’t contain location information

3-digit codes are carrier specific

Each message is limited to 160 characters

(larger messages combined at receiver)

SMS modem

(no short code)


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  • Non-audio media well integrated into NG911

    • “first class participants”

  • SMS challenging  requires large-scale mobile system modification

    • special-purpose clients may be easier

  • Transition video, relay services and RTT to NG911 early

    • avoid building transient conversion infrastructure