Summary
Internet communications based on SIP can provide rich and reliable emer-
gency call services for end users, such as “911” or “112,” often with better
availability because of the resilience of the Internet compared to the PSTN.
The emergency call services over the Internet require the emergency Public
Safety Access Points (PSAP) to be connected to the Internet, and also be IP
enabled. The emergency calling services based on IP can be most effectively
implemented and automated by using the DNS and delegating the correct reg-
istrations down the DNS delegation tree. The Interim “911” emergency calling
architecture for VoIP makes use of the PSTN and its legacy database infra-
structure in large part as is.
Emergency communications in case of disasters can use standard SIP meth-
ods and interwork well with the Emergency Telecommunications Services
(ETS) existing on the PSTN, as well as in a pure IP environment. SIP signaling
can also interwork with the network infrastructure for coordination of net-
work resources, such as PSTN gateway ports or on bandwidth-challenged IP
links.
References
[1] “Emergency Call Information in the Domain System” by B. Rosen. Internet
Draft, IETF, October 2005.
[2] “Requirements for Emergency Context Resolution with Internet Technolo-
gies” H. Schulzrinne and R. Marshall. Internet Draft, IETF, September 2005,
work in progress.
[3] IETF GEOPRIV WG: http://ietf.org/html.charters/geopriv-
charter.html.
[4] “Emergency telephone number” in Wikipedia: http://en.wikipedia
.org/wiki/Emergency_telephone_number.
[5] “Emergency Services URI for SIP” by H. Schulzrinne. Internet Draft, IETF,
October 2005, work in progress.
[6] “Security Threats and Requirements for Emergency Calling” by H.
Tschofenig et al. Internet Draft, IETF, December 2005.
[7] “NENA Interim VoIP Architecture for Enhanced 9-1-1 Services (i2)” pre-
pared by the National Emergency Number Association (NENA) VoIP-
Packet Technical Committee, December 6, 2005.
[8] “Framework for Supporting Emergency Telecommunications Service (ETS)
in IP Telephony” by K. Carlberg et al. RFC 4190, IETF, Nov. 2005.
[9] “Requirements for Resource Priority Mechanisms for SIP” by H.
Schulzrinne. RFC 3487, IETF, February 2005.
Emergency and Preemption Communication Services 285