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Using IM and SMS for Emergency Text Communications Wonsang Song, Jong Yul Kim, and Piotr Boni and Michael Armstrong Henning Schulzrinne Verizon Network and Technology Dept. of Computer Science, Columbia University {piotr.boni, michael.g.armstrong}@verizon.com {wonsang,jyk,hgs}@cs.columbia.edu ABSTRACT Integrating multimedia capable networks such as IM and Currently, text communication cannot be used to ask for SMS networks is one of the core concepts of Next Genera- help in emergency situations. Even in the Next Genera- tion 9-1-1 (NG9-1-1). NG9-1-1 is an IP/SIP-based system tion 9-1-1 system, an IP/SIP-based emergency communica- that will replace the current TDM-based emergency infras- tion system, there has been no investigation into how text tructure. We explain the NG9-1-1 system in more detail in communications such as Instant Messaging (IM) and Short Section 2. Message Service (SMS) can be integrated. We identify the Our key contribution is the integration of IM and SMS technical challenges in the integration of IM and SMS net- networks into the NG9-1-1 architecture. We introduce a works with the NG9-1-1 system, and propose a solution for model of integration for IM and SMS networks, and focus each challenge. We also describe a working prototype sys- on a few technical challenges in the integration of the text tem using our approach. communication system into the NG9-1-1 architecture. In the case of IM network, one problem is that most popu- lar IM protocols are proprietary and therefore incompatible Keywords with the NG9-1-1 system. Thus, we propose a SIP-based Emergency communications, IM, NG9-1-1, SIP, SMS model of integration. Another problem is consistent deliv- ery of multiple messages within a session to the same call taker. We solve this problem by implementing state-keeping 1. INTRODUCTION mechanisms in three di®erent components within the NG9- Text communication is increasingly popular, with an esti- 1-1 architecture. In the SMS network, there are three prob- mated 71 million IM users in the United States alone in 2007 lems: location conveyance, SIP conversion, and consistent [1]. In 2008, US SMS users sent 601 billion SMS messages, delivery of multiple messages within a session to the same an increase of 954% over 2005 [2]. As such, text communi- call taker. We solve the ¯rst problem by sending the loca- cation has become a major communication method. tion information and the user's message in one unit. We As a consequence, text communication is currently being introduce an SMS gateway to solve the second problem. To used for a variety of limited cases in emergency situations. solve the consistent message delivery problem, we implement In Boston and New York, SMS messages are used to report state-keeping mechanisms similar to the one used in the IM anonymous crime tips [3, 4]. It is also being used for emer- network. gency alerts on university campuses. We briefly describe the NG9-1-1 architecture in Section However, text communication should become an alterna- 2, show how we can integrate IM networks in Section 3, tive method available to the general public to request for illustrate how SMS messages can be delivered to IP-based help in emergency situations, just like a 9-1-1 voice call. If PSAPs in Section 4. text communication were to be used for emergency commu- nications, it would have the following advantages. It can be used in situations where voice calls are not possible. One 2. BACKGROUND example of such situations was during Hurricane Katrina, Next Generation 9-1-1 (NG9-1-1) is an IP/SIP-based emer- when voice calls were not possible because of overload, peo- gency communication system proposed by the National Emer- ple used SMS messages to successfully communicate with gency Number Association [6]. It provides media conver- their friends [5]. The deaf and hard-of-hearing can also ben- gence and data integration that is not possible with the cur- e¯t from emergency text communications. rent emergency communication system. For example, it is not possible to send a picture or video to the call taker using the current system, but NG9-1-1 is designed to allow such multimedia communications. Also, additional data such as Permission to make digital or hard copies of all or part of this work for floor plans, health records, or telematics data can be deliv- personal or classroom use is granted without fee provided that copies are ered to the call taker when they are needed. not made or distributed for profit or commercial advantage and that copies As shown in Figure 1, the architecture of the system is bear this notice and the full citation on the first page. To copy otherwise, to divided into two parts. One is the Emergency Services IP republish, to post on servers or to redistribute to lists, requires prior specific Network (ESInet) which is an IP-based network shared by permission and/or a fee. IPTCOMM ’09, July 7-8, 2009, Atlanta, Georgia, USA. a group of Public Safety Answering Points (PSAP). There Copyright 2009 ACM ...$10.00. may be several ESInets deployed. PSAPs are the agencies Call Origination Network Emergency Services IP Network (ESInet) PSAP A PSAP SIP . Proxy . Location-to-Service Translation (LoST) Server Automatic Call Taker Call Cellular Network Distributor . Emergency Services Public Safety Answering. Points (PSAP) Routing Proxy (ESRP) . PSAP Z PSTN Network PSAP SIP . Proxy . VoIP Network . Automatic Call Taker Call Distributor Figure 1: The NG9-1-1 architecture that receive and handle emergency calls. Each PSAP serves automatic call distributor selects a call taker and forwards users within its jurisdictional boundary. Therefore, each the call to the call taker. The call taker's status changes to ESInet covers a region that is the union of the boundaries busy and remains so until the end of the dialog. Meanwhile, of the PSAPs participating in that ESInet. The other part the call taker communicates with the caller to verify the lo- is the origination network such as cellular network, public cation, determine the type of emergency, and dispatch help switched telephony network, or Voice over IP (VoIP) net- to the caller. work. IM and SMS networks are also considered origination networks. The ESInet contains Emergency Services Routing Proxy, 3. INTEGRATION OF THE INSTANT MES- Location-to-Service Translation [7] server, and several IP- SAGING ORIGINATION NETWORK based PSAPs. The Emergency Services Routing Proxy (ESRP) is a SIP routing entity that forwards the call to the most ap- As mentioned in the previous section, it is the responsibil- propriate PSAP. The ESRP needs the Location-to-Service ity of the IM origination network to convert its protocols to Translation (LoST) server in order to determine the PSAP SIP when sending an emergency message. Although at least URL based on the caller's location. The LoST server is 85% of the IM market is dominated by AOL, Yahoo!, and an entity that maintains the PSAP boundaries and PSAP Microsoft [8], which use proprietary protocols, our work does URLs. An IP-based PSAP contains an automatic call dis- not focus on converting these protocols to SIP. Instead, we tributor and call takers. Automatic call distributors are focus on how these service providers can use SIP MESSAGE components that route incoming calls to a call taker based requests [9] to integrate their systems with the NG9-1-1 sys- on local policy. tem. There are many types of origination networks, but in the There is a reason we do not focus on the conversion prob- NG9-1-1 architecture, they share common responsibilities: lem. Commercial IM network providers already use stan- identifying an emergency call, obtaining the location of the dard IM protocols such as SIP or XMPP in their systems. caller and making it available to the PSAP, and routing the Yahoo! and Microsoft use SIP to allow their subscribers to call to the appropriate ESRP. Since the ESInet is SIP-based, talk across networks while AOL and Google use XMPP for it is also the origination networks' responsibility to convert the same purpose. Therefore, if we base our approach on us- their protocols to SIP. This means that IM and SMS service ing SIP MESSAGE method for integration, it may be easily providers must also ful¯ll these responsibilities in order to adapted by existing commercial IM providers. integrate with the NG9-1-1 system. Within SIP, there are two di®erent ways to send IM mes- An example of an emergency call flow within the NG9- sages. One method is to use Media Session Relay Protocol 1-1 architecture is as follows. When the caller initiates an (MSRP) [10]. MSRP is an example of a session-mode IM emergency voice call, the caller's device determines its lo- communication protocol that can be used with SIP call es- cation and queries a LoST server to resolve the location to tablishment, session negotiation, and teardown mechanisms. an ESRP URL. A SIP INVITE request with the location in- In MSRP, a TCP connection is established between the par- formation is sent to the ESRP. The ESRP queries a LoST ticipants once session is initiated. Since session is already server to resolve the location to a PSAP URL and forwards designed into the protocol, MSRP can be used by IM sys- the SIP INVITE request to the PSAP. Within the PSAP, the tems without having to keep track of the session by other means. However, MSRP is not widely used today. IM Origination Network Emergency Services IP Network Manual Entry LLDP-MED Switch Location ESRP ACD SIP Message SIP Message + Location + Location IM Client Outbound Proxy Location ESRP URL LoST Server Call Taker PSAP LoST Server Figure 2: The IM prototype system The other method, which we focus on, is a SIP MESSAGE sends all messages to the same ESInet regardless of changes method, which is an example of page-mode IM communica- in location.

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