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Moderator
Posts: 245
Registered: ‎09-12-2007

Article discussion: E-911 and VoWLAN

This is the discussion thread for the article "E-911 and VoWLAN" at http://airheads.arubanetworks.com/article/e-911-emergency-calling-and-vowlan
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Jon Green, ACMX, CISSP
Security Guy
Aruba
Posts: 105
Registered: ‎04-09-2007

E9-1-1

Having dabbled in E9-1-1 for a while, it was interesting to get a little deeper with this project.

From what I can see, Aruba customers have taken two directions on emergency calls. Some (government agencies, for instance) are most concerned that the public safety dispatch centre gets the correct information, mostly the location of the caller. For this they need a server like Cisco Emergency Responder - but of course this is required both for wired IP phones as well as wireless - and then they need to integrate the WLAN under it. As the paper explains, this is actually very easy, although the IP-subnet method of location is somewhat 'agricultural' in the words of my Aussie associate.

As far as I know, other emergency call handlers use the same mechanism. It's the safe fallback if CDP or LLDP fail to return a good location.

But the second area of activity in emergency calls is in providing useful information to internal security and response teams. I am aware of a number of Aruba customers - all universities, interestingly enough - that have gone after this with panache and elan. Here the object is to provide a screen showing the location of the caller on a floorplan, and perhaps of other devices/users in the area. An external application must first be alerted that an emergency call has been dialled, usually from a CTI interface to the IP PBX. It needs to extract the MAC address of the caller's device, which can then be used with a location query to either the mobility controller, or the AirWave management server. And up pops a nice clear picture of the floorplan with the calling device on it. I'd argue this isn't E9-1-1 in the legal requirement sense, but it's certainly of great importance to large campus WLANs, and should be of interest to many Aruba customers.

And before anyone adroitly points out that the IP-subnet method is lame and has a couple of holes in it, I should mention first that we are tied to the capabilities of the CER or equivalent, and second that we are not satisfied with this solution either. We (the industry and Aruba) can do better.

Peter Thornycroft
Frequent Contributor II
Posts: 110
Registered: ‎12-07-2007

Re: Article discussion: E-911 and VoWLAN

I can't get the link to work but we might be moving to something related. We presently have a different SSID for each campus to aid in 911. For different reasons, our telephony people want our central office SSID on all campuses just for some of our people to use. I've been trying to get them to move to a single SSID for the entire district but the telephony guys argue we can't because of 911 (their arguments don't really hold weight when put under scrutiny but higher-ups are non-the-less not willing to go along).

Since each school does have it's own Voice vlan, I could use IP based location (which is as accurate as our current SSID per campus system) for 911. How would I go about configuring it? Any docs or pointers?
Aruba
Posts: 105
Registered: ‎04-09-2007

Re: Article discussion: E-911 and VoWLAN

I couldn't get the link at the top to work either. It's probably moved. Here's where I found the article: http://airheads.arubanetworks.com/article/e-911-emergency-calling-and-vowlan

Antar
Moderator
Posts: 245
Registered: ‎09-12-2007

Re: Article discussion: E-911 and VoWLAN

Link fixed. :)
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Jon Green, ACMX, CISSP
Security Guy
Aruba
Posts: 105
Registered: ‎04-09-2007

Multi-site E9-1-1


I can't get the link to work but we might be moving to something related. We presently have a different SSID for each campus to aid in 911. For different reasons, our telephony people want our central office SSID on all campuses just for some of our people to use. I've been trying to get them to move to a single SSID for the entire district but the telephony guys argue we can't because of 911 (their arguments don't really hold weight when put under scrutiny but higher-ups are non-the-less not willing to go along).

Since each school does have it's own Voice vlan, I could use IP based location (which is as accurate as our current SSID per campus system) for 911. How would I go about configuring it? Any docs or pointers?




I read through this a couple of times, but there's something I'm not quite catching. I'd start with the call flow - is this a central PBX for multiple sites? If so, do you need to route calls from each site back out of a trunk on that site, and/or to use an emergency call server like Cisco Emergency Responder, RedSky or equivalent to switch the ANI?

In this latter case, using IP-subnet to identify the caller's location should work, the missing part is putting the phone on the right VLAN or having the DHCP server recognize its location... there are probably other ways. But it should work with a common SSID at every site, I think? You may have a WLAN where SSIDs are linked to VLANs, but there are other ways, with Aruba at least.

If the former, we'd have to draw it out. I'd like to think there's a way.

Does this extended rambling shed any light? I think if we could see a network diagram, we could work it out.

Antar
Frequent Contributor II
Posts: 110
Registered: ‎12-07-2007

Re: Article discussion: E-911 and VoWLAN

I think I muddied the water a bit. Here is the important part of the original post:

Since each school does have it's own Voice vlan, I could use IP based location (which is as accurate as our current SSID per campus system) for e9-1-1. How would I go about configuring it? Any docs or pointers?

Forget the single common SSID portion for now (each school would still have it's own voice VLAN).


Now I've been asked to look into the device location solution for personnel within our school district for e9-1-1. Do you have contact information for someone who might be able to help us get this set up? We have the Airwave management system (monitor only) in addition to our Master-local controllers so we should have those pieces ready.
Aruba
Posts: 105
Registered: ‎04-09-2007

Re: Article discussion: E-911 and VoWLAN

There are a number of possibilities here, depending how complicated/sophisticated you want to get:
1. If there's a central PBX, and outgoing trunks at each school campus, it should be possible to direct an emergency call from a particular location via the particular trunk, thus giving the PSAP the campus address. The trick with Wi-Fi phones is to map the phone's location to the outgoing trunk. I believe RedSky can do this, possibly also Cisco Emergency Responder. They would have to parse the IP address, but it seems IP subnet maps to site in your network, so that would be OK. If you were to rely on phone number -> outgoing trunk, you would have to make sure Wi-Fi phones always stay at the same school.
2. If the central PBX has trunks from a central location, you would have to use RedSky or CER to substitute the ANI on the call, mapping it to zones corresponding to IP subnet and hence site... should work without drama. This is what I documented in the note referenced in this thread. If the varous school sites are in different PSAP areas, it gets a little more complicated by RedSky has the technology.
3. Many organizations are just as concerned that internal security people should get information when a 911 call is dialled. This is where the AirWave (or Aruba controller) location API is useful. A query (usually by MAC address) to AirWave gets a floorplan or campus map with the device's location indicated. If you have a friendly local police department, you could perhaps put a screen on their desk to show this, but it's usually easier for internal security groups. You would need to write an app to make this work automatically end-to-end.

To move forward, try your local Aruba SE or feel free to get in touch at pthornycroft@arubanetworks.com

Antar
Aruba
Posts: 105
Registered: ‎04-09-2007

Re: Article discussion: E-911 and VoWLAN

I'm sorry Pete, I thought I replied to this a couple of weeks ago but I obviously had some finger trouble and didn't manage to post the message.

I don't have a full answer for you - at this stage it's probably best to get with your friendly Aruba SE or give me a buzz at pthornycroft(at)arubanetworks.com but I do have a few ideas.

- If you want to use 'IP Subnet' to identify the caller's location, you almost certainly need an emergency response server such as RedSky or Cisco Emergency Responder (for Cisco call manager / UC manager). This is the most comprehensive answer, but these systems aren't inexpensive.

Depending on how your IP-PBX is set up, it may be possible to accomplish an E9-1-1 solution in other ways. For instance, if there is an outgoing trunk from each school location, it may be possible to use a call routing rule in the PBX to send the call out via the local trunk. This will depend on the PBX.

The note referenced by this thread explains how it would work in the first instance (CER, although RedSky would work just as well).

Antar
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