Fixing 911 Overload

Every year, NENA – The National Emergency Number Association – estimates that there are over 240 million calls into 911 call centers (known as Public Safety Answer Points or PSAPs). A common problem among all PSAPs continues to be non-emergency calls arriving into the center on Their specialized 911 trunks that exist specifically for emergency calls. The quantity of these trunks is typically limited in each center and and the amount has been carefully engineered to handle the normal volume of 911 calls from the community served by that agency along with a few spares and diverse CO routing where available. The problem is that when they become flooded with non-emergency traffic, legitimate emergency calls could be blocked.

This design also makes the PSAP more susceptible to SWATTING and DDoS attacks by practically anyone and from anywhere. In some areas, emergency calls into a center that is busy may overflow to an adjacent PSAP. While this seems like a logical idea from a backup perspective, let’s examine the bigger picture here.

Not only does this expand the attack face from a SWATTING and DDoS perspective, it is actually quite useless unless there is a Mutual Aid and MOU agreement in place with the other agency. Without the proper authority and the radio comms infrastructure, as well as access to the CAD, there really isn’t much that those agencies can do other than answer the call and write down the information. They then need to figure out a way to get that incident to the agency that can provide service. Typically, if there is no access to the radio network of the adjacent community, or no visibility to the computer-aided dispatch or CAD system, there is little they can actually do with the information they have. Also, remember that if the call has overflowed to them in the first place, they might not even have a way of reaching the original agency using conventional methods, Where is the problem?

The Core Problem: Dedicated 911 Trunks

The existing 911 network in the US is dependent on specialized CAMA trunks. Queries for location use the Automatic Number Identification (ANI) received with the call to determine the location of the caller, and a direct peer-to-peer relationship exists between the PSAP and the local exchange carrier 911 Central Office using these single-purpose trunks.

Since these trunks are limited in number, when a non-emergency call arrives on an emergency trunk, that line becomes tied up for the duration of that call, even if the resource that handles the call is a non-emergency resource. This creates a traffic engineering problem, because now the number of trunks reserved to handle emergency calls are taking the additional non-emergency traffic, something that totally Skews the Erlang calculations used to engineer the number of circuits.

311 to the rescue?

Many believe, and cities like NYC and Philadelphia have implemented, a localized 311 non-emergency service designed to offload non-emergency calls from 911 Call centers and call takers. The call handling technology used to deliver a 311 service is similar to that in the 911 center. This allows the 311 facility itself to become a natural choice for a disaster recovery location or if a facility is needed to house a temporary relief workforce for the 911 center due to capacity or physical damage.

The fact that a 311 center exists though, does not itself provide a solution to the problem, a little more is required. The root cause of the overload issue noted earlier is that people dial 911 when they should have dialed 311. In other words, their call is arriving on the wrong network, and that wrong network has limited resources from a trunking perspective.

Are rubber bands the fix?

While fixes for critical emergency communications from the public should never use duct tape and rubber bands, “elasticity” does bring significant value. Looking back on legacy trunking, of nearly any kind, there is the limitation of a physical circuit on a pair of copper wires. If I need one, I order one. If I need 10, then I order 10. If I need 10, but I only can get 8, then I am short by 2, and there is not much I can do about it. SIP trunking, on the other hand, is delivered over a data facility. The actual bandwidth on that facility can often be dynamic and Is commonly referred to as “a pipe.”

When thinking about the characteristics of data, often it equates very nicely to water. If I need to deliver more water, I need to get a bigger pipe; if I need to deliver more data, the same concept applies. That being said, an inherent benefit of a “data pipe” is that often the delivery medium is the same regardless of the capacity or size. Now a request to the carrier can turn-up or turn-down service capacities through software or configuration. Because of this, the size of the pipe becomes elastic and flexible to my current trends and needs.

Re-engineering with new capabilities

With this new elasticity capability in our network, let’s re-engineer things a little bit to take advantage of its capabilities.

Modern NG-911 Network on Dynamic Trunks

With all of these circuits moved to intelligent SIP trunking, I now have flexibility and sizing capabilities that allow me to be more dynamic with emergency and non-emergency call center call routing. The initial overall pipe capacity reflects best guess estimations for ALL TRAFFIC, and a new control layer of communication between my premise and the carrier networks exists to communicate any changes Required in the specific trunk route sizing required.

Sending these real-time statistics and state changes to the carrier allows real-time elasticity of IP trunking size to realize the most efficient use of resources. Calls to 911 are automatically flagged as such and routed to the 911 CPE where call takers answer. Similarly, calls to 311 are automatically flagged as such and routed to the 311 CPE, where call-takers also answer those calls. By doing this, the number of simultaneous calls to each type of service is controlled by the CPE.

Should a 911 call end up being a non-emergency situation, and the call gets transferred to the 311 center for assistance, a signal is sent to the carrier to add additional bandwidth to the inbound 911 trunk group to compensate for the non-emergency call.

How bandwidth is calculated and allocated is something that now becomes totally under the control of the receiving agency. For example, let’s go back to our disaster recovery scenario. A significant natural event is impacting the local area. An anticipated  20% increase of 911 call taker staff will require 15 additional call-taker seats. In the 311 Center, 15 seats get flagged as auxiliary 911 positions and get staffed by 911 personnel. An increase in carrier bandwidth allows for the additional call volume expected.

This scenario is just another example of why the nation needs to move to NG 911 quickly. The Legacy 911 network in the US uses analog CAMA trunks that are special-purpose and fixed in their capacity. Increases must be pre-engineered and may take weeks or months to implement or sit idly unused, causing unnecessary charges to stack up to municipalities. The technology to accomplish this architecture already exists in nearly every commercial market in existence today. We should heed the lessons learned over many years and provide the same level of innovation to our most essential call centers, ones that save lives.

Mark J. Fletcher, ENP
Chief Architect – Public Safety Solutions – AVAYA

Follow me on Twitter @Fletch911
Listen to my Podcasts

Testing 1-2-3 . . . PART Three – Location

By: Mark J. Fletcher, ENP
Chief Architect Public Safety Solutions – AVAYA

In PART Two of this blog, we discussed the Emergency Call
Network, that segment of the PSTN dedicated to emergency calling and connecting the PSAPs together on a regional basis. In this section, we’ll cover the mobility that modern networks provide to Enterprise users, and clearly one of the most challenging pieces of information for 9-1-1 call takers to obtain.

We learned that the Selective Router in the E911 Tandem office was responsible for connecting callers to the right PSAP. That decision is made based on the Caller ID presented with the call. Initially, this was a very valid best practice, as the network was well documented, and changes were well controlled and performed by the service provider.

One Number – One Address
Telephone numbers rarely were co-located in multiple locations (with a few
exceptions) therefore the telephone number was an excellent data point usable for determining the location of a device, and the network was designed around this fact. In the mid 80’s, the Northern Telecom DMS 100 was introduced as a digital central office platform, and AT&T introduced the ESS 5 with similar capabilities.

With these new digital switching platforms, the layout inside the Central
Office radically changed from one that was mechanical stepper-motor-based to one that used a digital switching matrix, and with this automation fewer and fewer CO’s were staffed with technicians, as the building role became merely a wire center with a cross connection point for dial tone to street pairs. With the digital evolution these switches brought was a new series of custom calling features.

A Star is Born
Customers did however get some very new features, like Caller ID and feature ‘STAR-codes.’
Missed a call? Dial *69 to be connected with the last number that called. *72
along with a telephone number would forward any calls to the new destination, and depending on the services provisioned in the CO, various other features became available to customers. Many of these features took advantage of Caller ID information that was now available with the call. For the very first time, the called person could know the identity of the caller displayed on their telephone device. Caller ID (better known as Automatic Number Identification or ANI) now provided 911 centers with information about who was calling, or at least the number they were calling from. Now, if a silent call came in, or there was a question about the address and location, the original color could be easily reached. 911 centers also played games with the electrical properties on the phone lines, and it was common practice not to pass any answer or disconnect supervision from the PSAP. This providing for a simple way to keep the line open simply by
not hanging up on the public safety end.

Location, Location, Location
Without a service address, it’s impossible to send any help at the time of an
emergency. To solve this problem, 911 centers begin taking the ANI (phone
number) they were receiving with calls, in making a query back into the carrier network database that routed the call. This ALI Automatic Location Information added location to the context for wireline calls, however the cellular industry didn’t catch up, and continued to report only Phase 1 location information, which was the latitude and longitude of the radio tower the cell phone happened to connect through. With the white density of cell towers, compared to today, the effective service areas were quite large spending several miles. When cellular towers were installed on mountaintops they often lined up with political borders, once again exasperating the location problem if you’re located across the state lines hitting a remote tower due to height and proximity. This problem remained for many years, and only began to be solved as devices started to contain GPS radio receivers, but there was still an underlying problem at the network layer level.

Can You SEE Me Now?
As the density and placement of cellular towers increased, Basic radio
coverage and interoperability became commonplace. Carriers started to
interoperate with each other, and cellular handoff became a commonplace feature spanning the entire coast. Making a call with simple, but making a 911 call remained problematic. Don’t get me wrong, calls could be received and routed quite simply, however since the 911 network is a legacy analog based network, and no data channel exists to pass information on, 911 centers went into making a query to the cellular carrier asking them what visibility was available out of their network. Despite the device itself having an excellent location awareness, due to Wi-Fi fingerprints, access points, cellular towers, as well as a GPS signal when outside, the location of you what is the network looking in, and what the device had (known as handset-based location accuracy) was simply unavailable to the PSAPs, and no mechanism existed to communicate anything other than a voice path between the caller and the call taker.

Google Can Find Me . . .
Yes, I am well aware that Google, Domino’s Pizza, and a plethora of other
services are you able to locate your cellular device with incredible accuracy; in the first responders at 911 that are trying to save your life, cannot. The primary reason behind this is that because the device is utilizing an application. Also, the application has access to the device-based  location information held in the memory. This particular location information uses all of the data points that we discussed earlier, and that information is communicated back over the Internet to the host application. Once again, this is where the train goes way off the rails.

The information that is contained within the device is like having a trans-Atlantic Ocean liner that is landlocked in a lake in the middle of Kentucky. Regardless of the level of luxury, the number of passengers it holds, or the amazing abilities contained within the ship, without any use cases or access to the ocean, you’re going to have a rusting pile of steel in just a few years.

Unfortunately, this is the exact state at our Legacy PSTN network exists in
today. Consumer-based technology, the information age of the Internet, and the digital transformation that has occurred in commercial businesses, have connected the world at levels never before conceived. The devices we carry our hands and our pockets, are capable of blinding fast speeds and connectivity levels never dreamed of before. I can call, I can video, I can text, and I can email anyone on the planet; except 9-1-1. My daughter, halfway around the world on a beach in Waikiki with her boyfriend can transmit real-time high definition video from her handheld device to my handheld device 4,882 miles away with practically zero latency, but if she had a medical emergency and needed help, she would be stuck with a voice call and location inaccuracy about half mile or more if she called 911.

In any commercial enterprise space, despite be vast amount of digital
information we have available about the emergent event, the situational
awareness about the emergency, or even lifesaving information about the caller, no matter what the technology is at the origination point, the network in the receiving agency are relegated too low fidelity text based information. Why? I’m not sure I’ve gotten a good answer to that . . . . yet. But I know a few young entrepreneurs that took the problem head-on, and drove a paradigm shift change in an industry that was half a century old and very much stuck in its ways.

In Part Four of this series, we will dive into over-the-top applications, that
utilize the Internet in the open connectivity that exists nearly everywhere to take a short cut around the technology roadblocks that lay between citizens who need help, in the public safety first responders that can provide that help.

Please remember to follow me on Twitter @Fletch 911, check
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