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Lync Emergency 911 Calls by Location

January 9, 2012

Sometimes clients don’t need or aren’t ready to implement Enhanced 911 capabilities in Lync but still need to provide for calls to 911 from office locations. It is possible to configure Lync to handle 911 similar to how a PBX would handle these call. Emergency 911 calls placed from office locations where Lync Enterprise Voice has been implemented  will route out to the local PSAP with the main office phone number, but calls made to 911 from Lync outside the office will fail. Addistionally, this location based routing overrides a user’s assigned dial plan so when the travel to a different office locationa 911 calls will route based on their location.

For this to work, all office locations where Lync is enabled must be equipped with local telephone service and local equipment to direct 911 calls out to the local PSAP. Typically this would be accomplished with an ISDN PRI line and a PSTN Gateway although it would be possible to handle with a POTS line and Tenor.

911 PSTN Usage and Route

First a PSTN Usage and associated route need to be created so that when 911 is dialed it get’s normalized to +911 and routes out the gateway with a caller ID of the main office number.

Note – currently Lync only enables creating PSTN usages from within Voice Policies. Since in this scenario the PSTN usage should only be associated with a Location Policy, the PSTN usage needs to be removed from the Voice Policy after creating it.

If using a tool like the Dialing Rule Optimizer that creates a PSTN Usage and Route for service numbers of 211 through 911, be sure to modify the normalization rule to exclude 911 by changing pattern to match to ^([2-8]11)$.

Network Configuration

Next the appropriate network configuration needs to be entered into Lync. The location information entered here should not be confused with the Location Information Services (LIS) database. The LIS database provides location displayed in the Lync client interface and is the data that sent to Enhanced 911 service providers over a SIP trunk.

Location Policy

Create a user location policy for each site and select to Enable enhanced emergency services for the policy. Do not select to use location for emergency services only. Select the appropriate PSTN Usage previously created and enter the emergency dial number of 911 with a mask of 911. You may also wish to include a mask of 9911 if users were traditionally used to prefixing outbound calls with a 9. The mask would then need to be entered as 911;9911. Additionally, you may want to configure a notification URI to send Lync IM message to one or more personnel if a 911 call is placed. Note – the Conference URI and Conference mode will only work with a E911 provider.

Region, Sites and Subnets

Create a new region and select the central site that it will relate to. Typically regions relate to central sites and there will be one region created for each central site defined in the Lync topology.  Then create a site for each office and associate it with the appropriate region and select the correct location policy. Finally, create all subnets and masks for each site. Important – you must enter the subnets and masks as defined in DHCP and assigned to clients so that there is an exact match. For example, if the clients are assigned IP’s of 10.57.10.x, and 10.57.11.x, you would need to create two subnet ID’s, one for each with a mask of 24. Creating a subnet ID of 10.57.0.0 with a mask of 16 would not create a match between the client and Lync network configuration.

When you are done you will have Sites created for each office location with the appropriate Location Policy assigned and each site will have its subnets defined. Note – unless you are implementing CAC there is no need to create and assign a bandwidth policy.

Now, when users sign into their Lync client while in the office calls to 911 will normalize to +911 and route out the PSTN gateway.

If the same user signs into their Lync client from another location and dials 911, the number will not normalize and the call will fail.

A look at the Communicator tracing log shows that the provisioningGroupList contains a subnet attribute that identifies the logical network that the client is on and is used for defining the correction location policy and other network-dependent services that the client is configured to use.

20800: <provisioningGroupList xmlns=”http://schemas.microsoft.com/2006/09/sip/provisioninggrouplist&#8221; subnet=”10.1.0.0″><provisioningGroup name=”endpointConfiguration”/>locationPolicy“/><provisioningGroup name=”mediaConfiguration”/>

Test Calls

In a large Lync deployment, it may not be feasible for voice support personnel to travel to remote sites to test 911 calls. Since the Location Policy is configured as a user policy, it is possible to assign it to a test user account to enable that account to dial 911 and route successfully. Be sure to assign the account to the correct Dial Plan and Voice Policy. Also, as a best practice, before making test calls to 911, be sure to notify local office staff that you are making a call prior to placing the call in the event the PSAP calls back the main office number.

From → Lync 2010

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