Cisco Unified Communications Manager preempts lower precedence calls when adjusting video bandwidth for high priority calls.
If the bandwidth is not sufficient to preempt, Cisco Unified Communications Manager instructs endpoints to use previously
reserved lower video bandwidth. When Cisco Unified Communications Manager preempts a video call, the preempted party receives
a preemption tone and the call gets cleared.
Call Detail Records
For the DRSN, CDRs represent precedence levels with values 0, 1, 2, 3, and 4 where 0 specifies Executive Override and 4 specifies
Routine, as used in DSN. CDRs thus do not use the DRSN format.
Common Network Facility Preemption
Common Network Facility Preemption support exists only for T1-CAS and T1-PRI (North American) interfaces on targeted Voice
over IP gateways that Cisco Unified Communications Manager controls by using MGCP protocol and that have been configured as
MLPP Preemption Enabled.
Intercluster trunk MLPP carries precedence information through dialed digits. Domain information does not get preserved and
must be configured per trunk for incoming calls.
MLPP-enabled devices are not supported in line groups. We recommend the following guidelines:
- MLPP-enabled devices should not be configured in a line group. Route groups, however, are supported. Both trunk selection
and hunting methods are supported.
- If an MLPP-enabled device is configured in a line group or route group, in the event of preemption, if the route list does
not lock onto the device, the preempted call may be rerouted to other devices in the route/hunt list and preemption indication
may be returned only after no devices are able to receive the call.
- Route lists can be configured to support either of two algorithms of trunk selection and hunting for precedence calls. In
method 1, perform a preemptive search directly. In method 2, first perform a friendly search. If this search is not successful,
perform a preemptive search. Method 2 requires two iterations through devices in a route list. If route lists are configured
for method 2, in certain scenarios involving line groups, route lists may seem to iterate through the devices twice for precedence
Look Ahead For Busy
Cisco Unified Communications Manager does not support the Look Ahead for Busy (LFB) option.
Only MLPP Indication Enabled devices generate MLPP-related notifications, such as tones and ringers. If a precedence call
terminates at a device that is not MLPP Indication Enabled, no precedence ringer gets applied. If a precedence call originates
from a device that is not MLPP Indication Enabled, no precedence ringback tone gets applied. If a device that is not MLPP
Indication Enabled is involved in a call that is preempted (that is, the other side of the call initiated preemption), no
preemption tone gets applied to the device.
Phones and trunks
For phones, devices that are MLPP indication disabled (that is, MLPP Indication is set to Off) cannot be preempted. For trunks,
MLPP indication and preemption function independently.
Ring Setting Behavior
|Turning on MLPP Indication (at the enterprise parameter, common device configuration, or device level) disables normal Ring
Setting behavior for the lines on a device, unless MLPP Indication is turned off (overridden) for the device.
IOS gateways support the SCCP interface to Cisco Unified Communications Manager. They support BRI and analog phones which
appear on Cisco Unified Communications Manager as supported phone models. SCCP phones support the MLPP feature, and so do
some phones with specific SIP loads. See the relevant phone administration and user guides for Cisco IP phone support information.
|MLPP support for supplementary services specifies the following restrictions:
- MLPP addresses only the basic Call Pickup feature and Group Call Pickup feature, not Other Group Pickup.
- Call Forward All (CFA) support for inbound MLPP calls always forwards the call to the MLPP Alternate Party (MAP) target of
the called party, if the MAP target is configured. In the event of an incorrect configuration (that is, if no MAP target is
specified), the call is rejected, and the calling party receives a reorder tone.
- Call Forward No Answer (CFNA) support for inbound MLPP calls forwards the call once to a CFNA target. After the first hop,
if the call is unanswered, the call is sent to the MAP target of the original called party, if the MAP target has been configured.
In the event of an incorrect configuration (that is, if no MAP target is specified), the call gets rejected, and the calling
party receives reorder tone.
- Call Forward Busy (CFB) support for inbound MLPP calls forwards the call up to the maximum number that has been configured
for forwarding hops. If the maximum hop count gets reached, the call gets sent to the MAP target of the original called party,
if the MAP target has been configured. In the event of an incorrect configuration (that is, no MAP target is specified), the
call gets rejected, and the calling party receives reorder tone.
- For hunt pilot support, the hunt group algorithm must specify Longest Idle Time, Top Down, or Circular. Ensure the hunt group
options for busy treatment, no answer treatment, and unregistered treatment are set to Try next member, but do not go to next
group. Preemption only occurs across a single hunt group.
User Access Channel
User Access Channel support exists only for the following Cisco Unified IP Phone models, which must be configured as MLPP
- Cisco Unified IP Phone 7960, 7962, 7965
- Cisco Unified IP Phone 7940, 7942, 7945