CHAPTER16 Services
Mediant 4000 SBC | User's Manual
Skype for Business passes the location information of the Skype for Business client in an IETF-
standard format - Presence Information Data Format - Location Object (PIDF-LO)–in a SIP INVITE
message. However, this content cannot be sent on the SIP Trunksince they do no support such a
content. To overcome this, Enterprises deploying the device can divide their office space into
Emergency Response Locations (ERLs) and assign a dedicated Emergency Location Identification
Number (ELIN) to each ERL (or zone). When Skype for Business sends a SIP INVITE message
with the PIDF-LO to the device, it can parse the content and translate the calling number to an
appropriate ELIN. The device then sends the call to the SIP Trunkwith the ELIN number as the
calling number. The ELIN number is sent to the emergency service provider, which sends it on to
the appropriate PSAP according to the ELIN address match in the ALI database lookup.
The ERL defines a specific location at a street address, for example, the floor number of the
building at that address. The geographical size of an ERL is according to local or national
regulations (for example, less than 7000 square feet per ERL). Typically, you would have an ERL
for each floor of the building. The ELIN is used as the phone number for 911 callers within this ERL.
The figure below illustrates the use of ERLs and ELINs, with an E9-1-1 call from floor 2 at the
branch office:
The table below shows an example of designating ERLs to physical areas (floors) in a building and
associating each ERL with a unique ELIN.
Table 16-28:Designating ERLs and Assigning to ELINs
ERL Number Physical Area IP Address ELIN
1 Floor 1 10.13.124.xxx 503 972-4410
2 Floor 2 10.15.xxx.xxx 503 972-4411
3 Floor 3 10.18.xxx.xxx 503 972-4412
In the table above, a unique IP subnet is associated per ERL. This is useful if you implement
different subnets between floors. Therefore, IP phones, for example, on a specific floor are in the
same subnet and therefore, use the same ELIN when dialing 9-1-1.
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