User's Manual 644 Document #: LTRT-89730
Mediant 3000
2. Open the SBC General Settings page (Configuration tab > VoIP > SBC > SBC
General Settings), and then scroll down the page to the Call Priority and Preemption
group:
Figure 36-2: Configuring Emergency SBC Call Preemption
3. From the 'SBC Preemption Mode' drop-down list (SBCPreemptionMode), select
Enable to enable the SBC call preemption feature.
4. In the 'SBC Emergency Message Condition' field, enter the row index of the Message
Condition rule that you configured in Step 1 for identifying incoming emergency calls.
5. (Optional) Assign DiffServ levels (markings) to packets belonging to emergency calls:
a. In the 'SBC Emergency RTP DiffServ' field (SBCEmergencyRTPDiffServ), enter
the QoS level for RTP packets.
b. In the 'SBC Emergency Signaling DiffServ' field
(SBCEmergencySignalingDiffServ), enter the QoS level for SIP signaling packets.
6. Click Submit.
Notes:
• The device does not preempt already established emergency calls.
• The device does not monitor emergency calls with regards to Quality of
Experience (QoE).
36.2 Emergency Call Routing using LDAP to Obtain ELIN
The device can route emergency calls (e.g., 911) for INVITE messages that are received
without an ELIN number. This is in contrast to when the device is deployed in a Microsoft
Lync environment, whereby INVITE messages received from Lync contain ELIN numbers.
(For a detailed explanation on ELIN numbers and handling of emergency calls by
emergency server providers, see ''Enhanced 9-1-1 Support for Lync Server'' on page 292.)
To obtain an ELIN number for emergency calls received without ELINs, you can configure
the device to query an LDAP server for the 911 caller's ELIN number. The device adds the
resultant ELIN number and a Content-Type header for the PIDF XML message body to the
outgoing INVITE message, for example:
Content-Type: application/pidf+xml
<NAM>1234567890</NAM>
To enable this functionality, you need to configure a Call Setup rule in the Call Setup Rules
table (see ''Configuring Call Setup Rules'' on page 287). The following example shows a
Call Setup rule that queries an Active Directory (AD) server for the attribute
"telephoneNumber" whose value is the E9-1-1 caller's number, and then retrieves the
user's ELIN number from the attribute, "numberELIN":
Figure 36-3: Example of Call Setup Rule for LDAP Query of ELIN
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