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SIP-Based Emergency Notification System

SIP-Based Emergency Notification System. Knarig Arabshian IRT Laboratory Columbia University December 5, 2001. Overview . What is an Emergency Notification System? Current Emergency Notification Systems Using SIP for an Emergency Notification System

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SIP-Based Emergency Notification System

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  1. SIP-Based Emergency Notification System Knarig Arabshian IRT Laboratory Columbia University December 5, 2001

  2. Overview • What is an Emergency Notification System? • Current Emergency Notification Systems • Using SIP for an Emergency Notification System • Benefits in using SIP for Emergency Notification • Conclusion and Future work

  3. What are Emergency Notification Systems? • Allow government officials to notify a community of an emergency and precautionary measures that must be taken • Different emergency situations and alert methods • Fire Alarms • Earthquake or chemical spills indicated by sirens • Notifying public of terrorist attacks via radio/TV broadcasting

  4. Current Emergency Notification Systems • Emergency Alert System (EAS) • Controlled by the government and used mostly for wide area emergency notification • Specifies how and when state and local governments provide emergency instruction to the public

  5. Current Emergency Notification Systems • Localized Emergency Alerting Systems • Reverse 911, Community Alert Network notifies local officials or companies that subscribe to a network • Subscriptions include preferences regarding: • Geographical location of notification • Types of emergency alerts • Alert methods

  6. Using SIP for Emergency Notification • It is likely that traditional modes of communication will be augmented by Internet telephones and applications in the near future • We need to have Emergency Notification Systems established on the Internet • SIP is an application-layer signaling protocol which can be used for event notification

  7. SIP-based Emergency Notification System • Subscribe/Notify methods • SIP Authentication • Network Architecture

  8. Subscribe/Notify • SIP clients can subscribe to a remote SIP server and request notification from it • In case of an event, remote server will alert the client that an event has occurred • User Agent Client (UAC) represents the institution that subscribes for emergency notification • User Agent Server (UAS) is the institution that issues notifications during an emergency

  9. Subscribe/Notify • SIP message will have “SUBSCRIBE or “NOTIFY” in the method section of the SIP request. • The SUBSCRIBE request • Resembles that of a SIP INVITE • Must have one “Event” header in the header field which will specify the type of event it is subscribing to. • Must also contain an “Expires” header which defines the duration of the subscription

  10. Subscribe/Notify • If the UAC wants to subscribe to multiple events, then it must send multiple SUBSCRIBE messages, with distinct Call-IDs, to the UAS and indicate each Event it is subscribing to • If the Subscription has expired, then it sends another SUBSCRIBE message with the same Call-ID but different CSeq number • To unsubscribe, it sends a SUBSCRIBE message with the ”Expires” field set to zero

  11. Subscribe/Notify • Can contain optional message body in SUBSCRIBE request • Further details of notification such as methods of alerting (sirens, IM Messages, telephone calls) • Standardized grammar to automate the processing of the SUBSCRIBE request in the UAS • If message body is not present then UAC will expect the default method of alert

  12. Subscribe/Notify • NOTIFY Message Request • The “Event” header will indicate the type of emergency notification it is • The message body of the NOTIFY message will include specific instructions on the alert methods

  13. Emergency Notification Process Send Notify to UAC UAC UAS Send 200 Confirmation response to UAS

  14. Alert Process Process message body of NOTIFY request SOUND ALERT!! UAC

  15. SIP-based Emergency Notification System • Subscribe/Notify methods • SIP Authentication • Network Architecture

  16. SIP Authentication • UAS must verify that UAC is an authorized official capable of handling emergency alerts • UAC must also authenticate the veracity of the emergency alerts sent by the UAS to prevent false alarms • Two authentication schemes • Basic: weak security—transmits username and password in plain sight • Digest: better choice—uses more name-value pairs

  17. SIP Authentication • Subscriber must be aware of all the local emergency alerting agencies in its area • Someone has to provide this information • Third party • Emergency notification server

  18. Third Party Provides Credentials • Third party operates directory server with information about a local area • Monitored and maintained by government officials who recognize UACs and UASs as valid institutions • UACs and UASs subscribe to the directory server indicating alerts they request or support • Maps UACs to local UASs

  19. Third Party Provides Credentials • Lightweight Directory Access Protocol (LDAP) can be used to obtain information from local directory server • Government officials managing the directory server • Provide certificates to local UACs and UASs which establish them as valid institutions for community alerting • Create and distribute passwords to the UACs and their matching UASs

  20. Third Party Provides Credentials • This method is scalable and works well for large number of UACs and UASs • Not the preferred method for this system since there are only a limited number of agencies within a community who are authorized by the government to provide and receive emergency notification • Separate directory server needlessly complicates the system

  21. Emergency Notification Server Provides Credentials • Each emergency notification server has a pre-established list of authorized government officials in its area • It sends either postal mail or encrypted e-mail to them indicating • Their password is if they wanted to subscribe • Types of emergency notifications the server supports

  22. Emergency Notification Server Provides Credentials • UAC sends a SUBSCRIBE message to the UAS directly • UAC receives a 401 WWW-Authenticate message in response • UAC responds with its encrypted password in the Authorization header • UAS verifies the password and adds the subscriber as a registered user in its database • UAS sends a confirmation NOTIFY message to the UAC • UAC adds the UAS to its database of emergency notification servers

  23. UAC sends an encrypted concatenation of username and password in the Authorization header UAC sends a SUBSCRIBE message to UAS UAC UAS UAS responds with WWW-Authenticate message UAS confirms with a NOTIFY response message

  24. SIP-based Emergency Notification System • Subscribe/Notify methods • SIP Authentication • Network Architecture

  25. Network Architecture • Hierarchical network structure provides good scalability and facilitates the breakdown of geographical location • Main emergency notification server at the root serves all the states in the USA • Each state has a server that serves its cities and so on

  26. Network Architecture • Within the hierarchical tree, children of the same parent should have directory listings of each other • This is beneficial because the number of government officials within a community will not be very high • Saves time and resources in a critical emergency situation

  27. Hierarchy of Emergency Notification Server in the United States USA AL AK WY Abbeville Montgomery

  28. Network Architecture • Directory listing maintained by each server should map a server to an IP address • Server names are stored in a database using their geographical location names as keys • Child nodes must subscribe to their parent node servers and siblings must subscribe to each other

  29. Benefits in using SIP for Emergency Notification • Use on Different Applications and Devices • Internet telephony, multimedia applications, instant messaging and others • 3G cell phones, PDAs, home PCs and telephones

  30. Benefits in using SIP for Emergency Notification • More Information • SIP message can carry a lot of information which can give a detailed description of the emergency event • Single message can have multilingual content and receiver of the message can choose a language

  31. Benefits in using SIP for Emergency Notification • Automated Action • SIP message body automates subscription and notification process • UAC subscribes to UAS with following preferences in message body: fire, sound alarm bells • In case of a fire, UAS sends a NOTIFY to the UAC with its message body containing information which will invoke sounding of alarm bells.

  32. Benefits in using SIP for Emergency Notification • Lower Resource Consumption • SIP will be running over the Internet which is a much faster medium than PSTN • Example of a local network connected with a T1 (1.5Mb/s) line • 50 subscribers/line • 200 Kb/message • 7.49 subscribers/second/T1 line • Compare this with PSTN (56 Kb/s) line which yields 0.28 subscribers/second/PSTN line. • T1 reaches 27 times more subscribers/sec/line

  33. Benefits in using SIP for Emergency Notification • Complementary to Current EAS System • SIP-based emergency systems can be integrated with radio/TV broadcasting to provide emergency notifications via the Internet as well

  34. Conclusion and Future Work • Using SIP SUBSCRIBE/NOTIFY messages we can develop an Internet-based emergency notification system • Extend sipc to develop a flashing lights demo • Use SOAP (Simple Object Access Protocol) within the NOTIFY message body to automate alert process

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