User's Manual 29. Configuring Supplementary Services
Version 6.8 465 Mediant 500L MSBR
29.11.4.3.1 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 467. The ELIN table also stores the following information:
• ELIN: ELIN number
• Time: Time at which the original E9-1-1 call was terminated with the PSAP
• Count: Number of E9-1-1 calls currently using this ELIN
An example of the ELIN database table is shown below:
ELIN Time Count Index Call From
4257275678 22:11:52 0 2 4258359333
4257275999 22:11:57 0 3 4258359444
4257275615 22:12:03 0 0 4258359555
4257275616 22:11:45 0 1 4258359777
The ELIN table stores this information for a user-defined period (see ''Configuring the
E9-1-1 Callback Timeout'' on page 469), starting from when the E9-1-1 call,
established with the PSAP, terminates. After this time expires, the table entry with its
ELIN is disregarded and no longer used (for PSAP callback). Therefore, table entries
of only the most recently terminated
E9-1-1 callers are considered in the ELIN table.
The maximum entries in the ELIN table depend on the AudioCodes ELIN Gateway
deployed in the Lync Server 2010 environment:
• Mediant 1000 Series and Mediant 2000: 100 entries
• Mediant 3000: 300 entries
4. The ELIN Gateway uses the ELIN number as the E9-1-1 calling number and sends it
in the ISDN Setup message (as an ANI / Calling Party Number) to the PSTN.
An example of a SIP INVITE message received from an E9-1-1 caller is shown below. The
SIP Content-Type header indicating the PIDF-LO, and the NAM field listing the ELINs are
shown in bold typeface.
INVITE sip:911;phone-context=Redmond@192.168.1.12;user=phone
SIP/2.0
From:
"voip_911_user1"<sip:voip_911_user1@contoso.com>;epid=1D19090AED;t
ag=d04d65d924
To: <sip:911;phone-context=Redmond@192.168.1.12;user=phone>
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