Reachability Management; Network Operation Management Functions; Overload Management In Mme - Cisco ASR 5000 Series Administration Manual

▀ Features and Functionality - Base Software

Reachability Management

It provides a mechanism to track a UE which is in idle state for EPS connection management.
To reach a UE in idle state the MME initiates paging to all eNodeBs in all tracking areas in the TA list assigned to the
UE. The EPS session manager have knowledge about all the eNodeB associations to the MME and generates a list of
eNodeBs that needs to be paged to reach a particular UE.
The location of a UE in ECM-IDLE state is known by the network on a Tracking Area List granularity. A UE in ECM-
IDLE state is paged in all cells of the Tracking Areas in which it is currently registered. The UE may be registered in
multiple Tracking Areas. A UE performs periodic Tracking Area Updates to ensure its reachability from the network.

Network Operation Management Functions

This section describes following features:

Overload Management in MME

Radio Resource Management Functions
Mobile Equipment Identity Check
Multiple PDN Support
Overload Management in MME
Provides mechanism to handle overload/congestion situation. It can use the NAS signalling to reject NAS requests from
UEs on overload or congestion.
MME restricts the load that its eNodeBs are generating on it. This is achieved by the MME invoking the S1 interface
overload procedure as per 3GPP TS 36.300 and 3GPP TS 36.413 to a proportion of the eNodeB‟s with which the MME
has S1 interface connections.
Hardware and/or software failures within an MME may reduce the MME‟s load handling capability. Typically such
failures result in alarms which alert the operator or Operation and Maintenance system.
For more information on congestion control management, refer Configuring Congestion Control chapter in MME
Administration Guide.
capacity in the rest of the pool, the operator or Operation and Maintenance system might use the load re-
balancing procedure to move some load off an MME. However, extreme care is needed to ensure that this
load re-balancing does not overload other MMEs within the pool area (or neighboring SGSNs) as this might
lead to a much wider system failure.
▄ Cisco ASR 5000 Series Mobility Management Entity Administration Guide
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Only if the operator or Operation and Maintenance system is sure that there is spare
MME in LTE/SAE Wireless Data Services
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