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SIP-Based Emergency Notification System
Knarig ArabshianKnarig Arabshian
IRT LaboratoryIRT Laboratory
Columbia UniversityColumbia University
December 5, 2001December 5, 2001
Overview
What is an Emergency Notification System?What is an Emergency Notification System? Current Emergency Notification SystemsCurrent Emergency Notification Systems Using SIP for an Emergency Notification Using SIP for an Emergency Notification
SystemSystem Benefits in using SIP for Emergency Benefits in using SIP for Emergency
NotificationNotification Conclusion and Future workConclusion and Future work
What are Emergency Notification Systems? Allow government officials to notify a community Allow government officials to notify a community
of an emergency and precautionary measures that of an emergency and precautionary measures that must be takenmust be taken
Different emergency situations and alert methodsDifferent emergency situations and alert methods Fire AlarmsFire Alarms Earthquake or chemical spills indicated by Earthquake or chemical spills indicated by
sirenssirens Notifying public of terrorist attacks via Notifying public of terrorist attacks via
radio/TV broadcastingradio/TV broadcasting
Current Emergency Notification Systems Emergency Alert System (EAS)Emergency Alert System (EAS)
Controlled by the government and used Controlled by the government and used mostly for wide area emergency mostly for wide area emergency notificationnotification
Specifies how and when state and local Specifies how and when state and local governments provide emergency governments provide emergency instruction to the publicinstruction to the public
Current Emergency Notification Systems Localized Emergency Alerting SystemsLocalized Emergency Alerting Systems
Reverse 911, Community Alert Network Reverse 911, Community Alert Network notifies local officials or companies that notifies local officials or companies that subscribe to a networksubscribe to a network
Subscriptions include preferences regarding:Subscriptions include preferences regarding:Geographical location of notificationGeographical location of notificationTypes of emergency alertsTypes of emergency alertsAlert methods Alert methods
Using SIP for Emergency Notification It is likely that traditional modes of It is likely that traditional modes of
communication will be augmented by Internet communication will be augmented by Internet telephones and applications in the near futuretelephones and applications in the near future
We need to have Emergency Notification Systems We need to have Emergency Notification Systems established on the Internetestablished on the Internet
SIP is an application-layer signaling protocol SIP is an application-layer signaling protocol which can be used for event notificationwhich can be used for event notification
SIP-based Emergency Notification System Subscribe/Notify methods Subscribe/Notify methods SIP AuthenticationSIP Authentication Network ArchitectureNetwork Architecture
Subscribe/Notify
SIP clients can subscribe to a remote SIP server SIP clients can subscribe to a remote SIP server and request notification from itand request notification from it
In case of an event, remote server will alert the In case of an event, remote server will alert the client that an event has occurredclient that an event has occurred
User Agent Client (UAC) represents the institution User Agent Client (UAC) represents the institution that subscribes for emergency notificationthat subscribes for emergency notification
User Agent Server (UAS) is the institution that User Agent Server (UAS) is the institution that issues notifications during an emergencyissues notifications during an emergency
Subscribe/Notify
SIP message will have “SUBSCRIBE or SIP message will have “SUBSCRIBE or “NOTIFY” in the method section of the SIP “NOTIFY” in the method section of the SIP request.request.
The SUBSCRIBE requestThe SUBSCRIBE request Resembles that of a SIP INVITE Resembles that of a SIP INVITE Must have one “Event” header in the header field Must have one “Event” header in the header field
which will specify the type of event it is subscribing to.which will specify the type of event it is subscribing to. Must also contain an “Expires” header which defines Must also contain an “Expires” header which defines
the duration of the subscriptionthe duration of the subscription
Subscribe/Notify
If the UAC wants to subscribe to multiple events, If the UAC wants to subscribe to multiple events, then it must send multiple SUBSCRIBE messages, then it must send multiple SUBSCRIBE messages, with distinct Call-IDs, to the UAS and indicate with distinct Call-IDs, to the UAS and indicate each Event it is subscribing toeach Event it is subscribing to
If the Subscription has expired, then it sends If the Subscription has expired, then it sends another SUBSCRIBE message with the same Call-another SUBSCRIBE message with the same Call-ID but different CSeq numberID but different CSeq number
To unsubscribe, it sends a SUBSCRIBE message To unsubscribe, it sends a SUBSCRIBE message with the ”Expires” field set to zerowith the ”Expires” field set to zero
Subscribe/Notify
Can contain optional message body in Can contain optional message body in SUBSCRIBE requestSUBSCRIBE request Further details of notification such as methods Further details of notification such as methods
of alerting (of alerting (sirens, IM Messages, telephone calls)sirens, IM Messages, telephone calls)
Standardized grammar to automate the Standardized grammar to automate the processing of the SUBSCRIBE request in the processing of the SUBSCRIBE request in the UASUAS
If message body is not present then UAC will If message body is not present then UAC will expect the default method of alertexpect the default method of alert
Subscribe/Notify
NOTIFY Message RequestNOTIFY Message Request The “Event” header will indicate the type The “Event” header will indicate the type
of emergency notification it isof emergency notification it is The message body of the NOTIFY The message body of the NOTIFY
message will include specific instructions message will include specific instructions on the alert methods on the alert methods
SIP-based Emergency Notification System Subscribe/Notify methods Subscribe/Notify methods SIP AuthenticationSIP Authentication Network ArchitectureNetwork Architecture
SIP Authentication
UAS must verify that UAC is an authorized UAS must verify that UAC is an authorized official capable of handling emergency alertsofficial capable of handling emergency alerts
UAC must also authenticate the veracity of the UAC must also authenticate the veracity of the emergency alerts sent by the UAS to prevent false emergency alerts sent by the UAS to prevent false alarmsalarms
Two authentication schemesTwo authentication schemes Basic: weak security—transmits username and Basic: weak security—transmits username and
password in plain sightpassword in plain sight Digest: better choice—uses more name-value Digest: better choice—uses more name-value
pairspairs
SIP Authentication
Subscriber must be aware of all the local Subscriber must be aware of all the local emergency alerting agencies in its areaemergency alerting agencies in its area
Someone has to provide this informationSomeone has to provide this information Third partyThird party Emergency notification server Emergency notification server
Third Party Provides Credentials
Third party operates directory server with Third party operates directory server with information about a local areainformation about a local area
Monitored and maintained by government Monitored and maintained by government officials who recognize UACs and UASs as valid officials who recognize UACs and UASs as valid institutionsinstitutions
UACs and UASs subscribe to the directory server UACs and UASs subscribe to the directory server indicating alerts they request or supportindicating alerts they request or support
Maps UACs to local UASsMaps UACs to local UASs
Third Party Provides Credentials
Lightweight Directory Access Protocol (LDAP) Lightweight Directory Access Protocol (LDAP) can be used to obtain information from local can be used to obtain information from local directory serverdirectory server
Government officials managing the directory Government officials managing the directory serverserver Provide certificates to local UACs and UASs Provide certificates to local UACs and UASs
which establish them as valid institutions for which establish them as valid institutions for community alertingcommunity alerting
Create and distribute passwords to the UACs Create and distribute passwords to the UACs and their matching UASsand their matching UASs
Third Party Provides Credentials
This method is scalable and works well for large This method is scalable and works well for large number of UACs and UASsnumber of UACs and UASs
Not the preferred method for this system since Not the preferred method for this system since there are only a limited number of agencies within there are only a limited number of agencies within a community who are authorized by the a community who are authorized by the government to provide and receive emergency government to provide and receive emergency notificationnotification
Separate directory server needlessly complicates Separate directory server needlessly complicates the systemthe system
Emergency Notification Server Provides Credentials Each emergency notification server has a pre-Each emergency notification server has a pre-
established list of authorized government officials established list of authorized government officials in its areain its area
It sends either postal mail or encrypted e-mail to It sends either postal mail or encrypted e-mail to them indicatingthem indicating Their password is if they wanted to subscribeTheir password is if they wanted to subscribe Types of emergency notifications the server Types of emergency notifications the server
supportssupports
Emergency Notification Server Provides Credentials UAC sends a SUBSCRIBE message to the UAS directlyUAC sends a SUBSCRIBE message to the UAS directly UAC receives a 401 WWW-Authenticate message in UAC receives a 401 WWW-Authenticate message in
responseresponse UAC responds with its encrypted password in the UAC responds with its encrypted password in the
Authorization headerAuthorization header UAS verifies the password and adds the subscriber as a UAS verifies the password and adds the subscriber as a
registered user in its databaseregistered user in its database UAS sends a confirmation NOTIFY message to the UACUAS sends a confirmation NOTIFY message to the UAC UAC adds the UAS to its database of emergency UAC adds the UAS to its database of emergency
notification serversnotification servers
UAC UAS
UAS responds with WWW-Authenticate message
UAC sends an encrypted concatenation of username and password in the Authorization header
UAS confirms with a NOTIFY response message
UAC sends a SUBSCRIBE message to UAS
SIP-based Emergency Notification System Subscribe/Notify methods Subscribe/Notify methods SIP AuthenticationSIP Authentication Network ArchitectureNetwork Architecture
Network Architecture
Hierarchical network structure provides Hierarchical network structure provides good scalability and facilitates the good scalability and facilitates the breakdown of geographical locationbreakdown of geographical location
Main emergency notification server at the Main emergency notification server at the root serves all the states in the USAroot serves all the states in the USA
Each state has a server that serves its cities Each state has a server that serves its cities and so onand so on
Network Architecture
Within the hierarchical tree, children of the Within the hierarchical tree, children of the same parent should have directory listings same parent should have directory listings of each otherof each other
This is beneficial because the number of This is beneficial because the number of government officials within a community government officials within a community will not be very highwill not be very high
Saves time and resources in a critical Saves time and resources in a critical emergency situationemergency situation
Network Architecture
Directory listing maintained by each server Directory listing maintained by each server should map a server to an IP addressshould map a server to an IP address
Server names are stored in a database using Server names are stored in a database using their geographical location names as keystheir geographical location names as keys
Child nodes must subscribe to their parent Child nodes must subscribe to their parent node servers and siblings must subscribe to node servers and siblings must subscribe to each othereach other
Benefits in using SIP for Emergency Notification Use on Different Applications and DevicesUse on Different Applications and Devices
Internet telephony, multimedia Internet telephony, multimedia applications, instant messaging and applications, instant messaging and othersothers
3G cell phones, PDAs, home PCs and 3G cell phones, PDAs, home PCs and telephonestelephones
Benefits in using SIP for Emergency Notification More InformationMore Information
SIP message can carry a lot of SIP message can carry a lot of information which can give a detailed information which can give a detailed description of the emergency eventdescription of the emergency event
Single message can have multilingual Single message can have multilingual content and receiver of the message can content and receiver of the message can choose a languagechoose a language
Benefits in using SIP for Emergency Notification Automated ActionAutomated Action
SIP message body automates subscription and SIP message body automates subscription and notification processnotification process
UAC subscribes to UAS with following UAC subscribes to UAS with following preferences in message body: fire, sound alarm preferences in message body: fire, sound alarm bellsbells
In case of a fire, UAS sends a NOTIFY to the In case of a fire, UAS sends a NOTIFY to the UAC with its message body containing UAC with its message body containing information which will invoke sounding of information which will invoke sounding of alarm bells.alarm bells.
Benefits in using SIP for Emergency Notification Lower Resource ConsumptionLower Resource Consumption
SIP will be running over the Internet which is a much SIP will be running over the Internet which is a much faster medium than PSTNfaster medium than PSTN
Example of a local network connected with a T1 Example of a local network connected with a T1 (1.5Mb/s) line(1.5Mb/s) line
50 subscribers/line50 subscribers/line200 Kb/message200 Kb/message7.49 subscribers/second/T1 line7.49 subscribers/second/T1 line
Compare this with PSTN (56 Kb/s) line which yields Compare this with PSTN (56 Kb/s) line which yields 0.28 subscribers/second/PSTN line. 0.28 subscribers/second/PSTN line.
T1 reaches 27 times more subscribers/sec/lineT1 reaches 27 times more subscribers/sec/line
Benefits in using SIP for Emergency Notification Complementary to Current EAS SystemComplementary to Current EAS System
SIP-based emergency systems can be SIP-based emergency systems can be integrated with radio/TV broadcasting to integrated with radio/TV broadcasting to provide emergency notifications via the provide emergency notifications via the Internet as wellInternet as well
Conclusion and Future Work
Using SIP SUBSCRIBE/NOTIFY messages Using SIP SUBSCRIBE/NOTIFY messages we can develop an Internet-based we can develop an Internet-based emergency notification systememergency notification system
Extend sipc to develop a flashing lights Extend sipc to develop a flashing lights demodemo
Use SOAP (Simple Object Access Protocol) Use SOAP (Simple Object Access Protocol) within the NOTIFY message body to within the NOTIFY message body to automate alert processautomate alert process