User's Manual 344 Document #: LTRT-68822
Mediant 2000
26.5.2.3 AudioCodes ELIN Gateway for Lync Server 2010 E9-1-1 Calls to PSTN
The Microsoft Mediation Server sends the location information of the E9-1-1 caller in the
XML-based PIDF-LO body contained in the SIP INVITE message. However, this content
cannot be sent on the PSTN network using ISDN PRI due to protocol limitations. To solve
this issue, Lync Server 2010 requires a PSTN Gateway (ELIN Gateway) to send the E9-1-1
call to the PSTN. When Lync Server 2010 sends the PIDF-LO to the PSTN Gateway, it
parses the content and translates the calling number to an appropriate ELIN. This ensures
that the call is routed to an appropriate PSAP, based on ELIN-address match lookup in the
Emergency Services provider's ALI database.
The figure below illustrates an AudioCodes ELIN Gateway deployed in the Lync Server
2010 environment for handling E9-1-1 calls between the Enterprise and the PSTN.
Figure 26-5: AudioCodes ELIN Gateway for E9-1-1 in Lync Server 2010 Environment
26.5.2.3.1 Detecting and Handling E9-1-1 Calls
The ELIN Gateway identifies E9-1-1 calls and translates their incoming E9-1-1 calling
numbers into ELIN numbers, sent toward the PSAP. The ELIN Gateway handles the
received E9-1-1 calls as follows:
1. The ELIN Gateway identifies E9-1-1 calls if the incoming SIP INVITE message
contains a PIDF-LO XML message body. This is indicated in the SIP Content-Type
header, as shown below:
Content-Type: application/pidf+xml
2. The ELIN Gateway extracts the ELIN number(s) from the "NAM" field in the XML
message. The "NAM" field corresponds to the <CompanyName> column in the
Location Information Server (LIS). The ELIN Gateway supports up to five ELIN
numbers per XML message. The ELINs are separated by a semicolon. The digits of
the ELIN number can be separated by hyphens (xxx-xxx-xxx) or they can be adjacent
(xxxxxxxxx), as shown below:
<ca:NAM>1111-222-333; 1234567890 </ca:NAM>
3. The ELIN Gateway saves the From header value of the SIP INVITE message in its
ELIN database table (Call From column). The ELIN table is used for PSAP callback,
as discussed later in 'PSAP Callback to Lync 2010 Clients for Dropped E9-1-1 Calls'
on page 346. The ELIN table also stores the following information:
• ELIN: ELIN number
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