- About this Guide
- Mobility Management Entity Overview
- Mobility Management Entity Configuration
- 128K eNodeB Connections
- A-MSISDN Functionality
- Access Restriction based on Regional Zone Code
- APN Override
- Backup and Recovery of Key KPI Statistics
- Cause Code #66
- Cell Broadcast Center - SBc Interface
- Cell Traffic Trace
- Closed Subscriber Groups
- CSFB and SMS over SGs Interface
- CSFB for 1xRTT
- DDN Throttling
- Default APN for DNS Failure
- eDRX Support on the MME
- Emergency Bearer Services
- Enhanced Congestion Control and Overload Control
- Enhanced Multimedia Priority Service (eMPS)
- Enhanced Event Logging
- Foreign PLMN GUTI Management
- GTP-C Load and Overload Control on MME
- GUTI Re-allocation
- Heuristic and Intelligent Paging
- HSS-based P-CSCF Restoration
- Idle-mode Signaling Reduction
- IMSI Manager Overload Control
- IMSI Manager Scaling on the MME
- Integrity and Confidentiality Algorithms for UE
- IPNE Service
- Limiting the Number of SGWs Tried
- Load Balancing and Rebalancing and VoLTE Offloading
- Local Emergency Numbers List
- Location Services
- MBMS for MME (eMBMS)
- Operator Policy
- Operator Specific QCI
- Operator Policy Selection Based on IMEI-TAC
- Overcharging Protection
- Paging Priority IE Support
- Power Saving Mode (PSM) in UEs
- QoS Profile Support
- S13 Additional IMEI Check
- Selective Authentication
- Session Tracing
- SGW Blacklisting on the MME
- SGSN-MME Combo Optimization
- Single Radio Voice Call Continuity
- SRVCC for 1xRTT
- State-Location Information Retrieval Flag
- TAI-based Routing for 20-bit and 28-bit eNB ID
- Timer-based GBR Bearer Deactivation
- UDPC2 Support for MME/SGSN
- UE Relocation
- VLR Management
- Troubleshooting the MME Service
- Monitor the MME Service
- Engineering Rules
- Feature Description
- Configuring EnhancedCongestion Control
- Configuring Enhanced Congestion Control
- Verifying the Congestion Control Configuration
- Verifying Congestion Action Profiles
- Monitoring andTroubleshooting
Enhanced Congestion
Control and Overload Control
Feature Description
The MME provides an enhanced congestion control and overload control feature set.
This feature builds on the base congestion control functionality provided on the MME. Refer to the Congestion Control and Overload Control sections in the MME Overview chapter for more information about the basic functionality.
To use this feature, you need a valid license key (MME Resiliency) installed. Contact your Cisco Account or Support representative for information on how to obtain a license.
Enhanced Congestion Control and Overload Control
- Drop or reject the following S1-AP/NAS messages: S1 Setup, Handover events, TAU request, Service request, PS-Attach request, Combined-attach request, Additional PDN request, or UE initiated bearer resource allocation.
- Allow voice or emergency calls/events.
- Initiate S1AP
overload start to a percentage of eNodeBs with options to signal any of the
following in the Overload Response IE:
- reject non-emergency sessions
- reject new sessions
- permit emergency sessions
- permit high-priority sessions and mobile-terminated services
- reject delay-tolerant access.
Relationships to Other Features
This license-enabled feature builds on the base congestion control functionality provided on the MME.
Refer to the Congestion Control and Overload Control sections in the MME Overview chapter for more information about the basic functionality.
Additional information is also provided in the Congestion Control chapter in the System Administration Guide.
Limitations
- Port-specific RX and TX utilization
- Port RX and TX utilization
- Message queue utilization
- Message queue wait time
The license-enabled Enhanced Congestion Control funtionality on the MME does not support the monitoring of these resources using three different threshold levels (critical, major and minor). Only a single threshold level (critical) can be monitored for these resources.
Configuring Enhanced Congestion Control
This feature requires that a valid license key be installed. Contact your Cisco Account or Support representative for information on how to obtain a license.
- Configuring Enhanced Congestion Control
- Verifying the Congestion Control Configuration
- Verifying Congestion Action Profiles
Configuring Enhanced Congestion Control
This section includes configuration procedures for the following:
- Configuring Thresholds and Tolerances
- License Utilization Thresholds
- Maximum Session Per Service Thresholds
- Service Control CPU Thresholds
- System CPU Thresholds
- System Memory Thresholds
- Configuring a Congestion Action Profile
- Associating a Congestion Action Profile with Congestion Control Policies
- Configuring Overload Control
- Configuring Congestion SNMP Traps
- Configuring Thresholds and Tolerances
- Configuring a Congestion Action Profile
- Associating a Congestion Action Profile with Congestion Control Policies
- Configuring Overload Control
- Configuring Enhanced Congestion SNMP Traps
Configuring Thresholds and Tolerances
Congestion threshold values must be defined to establish when a congestion condition is reached. Congestion threshold tolerances must also be configured to establish when a congestion condition is cleared. Individual thresholds values and tolerances can be defined for critical , major and minor thresholds.
The default tolerance window for critical thresholds is 10. The default for major and minor thresholds is 0.
If the tolerance is configured greater than threshold, then the tolerance will be treated as zero.
configure congestion-control threshold tolerance critical 10 congestion-control threshold max-sessions-per-service-utilization major 70 congestion-control threshold tolerance major 10 congestion-control threshold max-sessions-per-service-utilization minor 60 congestion-control threshold tolerance minor 10 congestion-control threshold max-sessions-per-service-utilization critical 80 end
For information about all of the congestion control commands available, refer to the Global Configuration Mode Commands chapter of the ASR 5x00 Command Line Interface Reference .
- License Utilization Thresholds
- Maximum Session Per Service Thresholds
- Service Control CPU Thresholds
- System CPU Thresholds
- System Memory Thresholds
License Utilization Thresholds
The license-utilization threshold is calculated based on the configured license values for the chassis.
In this example configuration, the minor threshold will be triggered at 4000 calls, major threshold will be triggered at 6000 calls, and critical threshold will be triggered at 8000 calls.
congestion-control threshold license-utilization critical 80 congestion-control threshold license-utilization major 60 congestion-control threshold license-utilization minor 40
Maximum Session Per Service Thresholds
This threshold is configured across all MME services.
config congestion-control threshold max-sessions-per-service-utilization critical 80
When there are multiple MME services configured with different max-subscribers parameters, chassis congestion will be calculated using the minimum of max-subscribers configured in each of the different MME services.
However, congestion actions will be applied to each individual service based on its corresponding max-session-per-service parameters.
For example:
configure context ingress mme-service mmesvc1 bind s1-mme ipv4-address 10.10.10.2 max-subscribers 10000 exit exit mme-service mmesvc2 bind s1-mme ipv4-address 10.10.10.3 max-subscribers 1000 exit exit mme-service mmesvc3 bind s1-mme ipv4-address 192.80.80.3 max-subscribers 20000 end
In the above example, chassis level critical congestion will get triggered when the number of subscribers in mmesvc2 is at 800. Corresponding SNMP traps will be generated. However, congestion policies will not be applied for mmesvc1 and mmesvc3. When the number of subscribers in mmesvc1 and mmesvc3 reaches 8000 and 16000 respectively, then congestion policies will be applied for mmesvc1 and mmesvc3.
Chassis congestion will be cleared only when the congestion is cleared in all MME services.
Similarly, when minor, major and critical threshold are configured for max-session-per-service for many MME services, the maximum value of the threshold will be considered for chassis level congestion.
For example, if mmesvc1 reaches the major threshold, mmesvc2 reaches the critical threshold and mmesvc3 reaches the minor threshold, then chassis congestion state will be critical.
Service Control CPU Thresholds
This threshold is calculated from the system's demux CPU. The threshold is calculated based on a five minute average CPU usage.
The highest CPU usage value of two CPU cores of the demux CPU is considered. For example, if CPU core 0 has a five minute CPU usage of 40 and CPU core 1 has a five minute CPU usage of 80, then CPU core 1 will be considered for threshold calculation.
The following example configuration shows threshold levels of 80, 60, and 40 usage:
congestion-control threshold service-control-cpu-utilization critical 80 congestion-control threshold service-control-cpu-utilization major 60 congestion-control threshold service-control-cpu-utilization minor 40
System CPU Thresholds
This threshold is calculated using the five minute CPU usage average of all CPUs (except standby CPU and SMC CPU ).
The highest CPU usage value of two CPU core of all CPU will be considered.
The following example configuration shows threshold levels of 80, 60, and 40 usage:
congestion-control threshold system-cpu-utilization critical 80 congestion-control threshold system-cpu-utilization major 60 congestion-control threshold system-cpu-utilization minor 40
System Memory Thresholds
This threshold is calculated using the five minute memory usage average of all CPUs (except standby CPU and SMC CPU ).
The following example configuration shows threshold levels of 80, 60, and 40 usage:
congestion-control threshold system-memory-utilization critical 80 congestion-control threshold system-memory-utilization major 60 congestion-control threshold system-memory-utilization minor 40
Configuring a Congestion Action Profile
Congestion Action Profiles define a set of actions which can be executed after the corresponding threshold is crossed.
Use the following example configuration which creates a congestion action profile named critical_action_profile and defines several actions for this profile:
configure lte-policy congestion-action-profile critical_action_profile reject s1-setups time-to-wait 60 drop handovers reject combined-attaches report-overload permit-emergency-sessions enodeb-percentage 50 end
See the Congestion Action Profile Configuration Commands chapter in the Command Line Reference for details about all the congestion action profile commands available.
Refer to Configuring Overload Control in this chapter for more information about the report-overload keyword and associated functionality.
Associating a Congestion Action Profile with Congestion Control Policies
Each congestion control policy (critical, major, minor) must be associated with a congestion control profile.
The following example configuration to associate the congestion action profile named critical_action_profile with the critical congestion control policy:
configure congestion-control policy critical mme-service action-profile critical_action_profile
Separate congestion action profiles can be associated with major and minor congestion control policies, for example:
congestion-control policy major mme-service action-profile major_action_profile congestion-control policy minor mme-service action-profile minor_action_profile
Configuring Overload Control
When an overload condition is detected on an MME, the system can be configured to report the condition to a specified percentage of eNodeBs and take the configured action on incoming sessions.
configure lte-policy congestion-action-profile <profile_name> congestion-action-profile <profile_name> end
configure congestion-control policy critical mme-service action report-overload reject-new-sessions enodeb-percentage <percentage> end
Notes:
See the Congestion Action Profile Configuration Mode Commands chapter in the Command Line Reference for details about all the congestion action profile commands available.
Configuring Enhanced Congestion SNMP Traps
When an enhanced congestion condition is detected, an SNMP trap (notification) is automatically generated by the system.
To disable (suppress) this trap:
configure snmp trap suppress EnhancedCongestion end
To re-enable generation of the Enhanced Congestion trap:
configure snmp trap enable EnhancedCongestion target <target-name> end
Verifying the Congestion Control Configuration
Use the following Exec mode command to display the configuration of the congestion control functionality.
show congestion-control configuration
Congestion-control: enabled Congestion-control Critical threshold parameters system cpu utilization: 80 service control cpu utilization: 80 system memory utilization: 80 message queue utilization: 80 message queue wait time: 10 seconds port rx utilization: 80 port tx utilization: 80 license utilization: 100 max-session-per-service utilization: 100 tolerence limit: 10 Congestion-control Critical threshold parameters system cpu utilization: 80 service control cpu utilization: 80 system memory utilization: 80 message queue utilization: 80 message queue wait time: 10 seconds port rx utilization: 80 port tx utilization: 80 license utilization: 100 max-session-per-service utilization: 100 tolerence limit: 10
Congestion-control Major threshold parameters
system cpu utilization: 0
service control cpu utilization: 0
system memory utilization: 0
message queue utilization: 0
message queue wait time: 0 seconds
port rx utilization: 0
port tx utilization: 0
license utilization: 0
max-session-per-service utilization: 0
tolerence limit: 0
Congestion-control Minor threshold parameters
system cpu utilization: 0
service control cpu utilization: 0
system memory utilization: 0
message queue utilization: 0
message queue wait time: 0 seconds
port rx utilization: 0
port tx utilization: 0
license utilization: 0
max-session-per-service utilization: 0
tolerence limit: 0
Overload-disconnect: disabled
Overload-disconnect threshold parameters
license utilization: 80
max-session-per-service utilization: 80
tolerance: 10 session disconnect percent: 5 iterations-per-stage: 8 Congestion-control Policy mme-service: Critical Action-profile : ap3 Major Action-profile : ap2 Minor Action-profile : ap1
Verifying Congestion Action Profiles
show lte-policy congestion-action-profile { name <profile_name> | summary }
Monitoring and Troubleshooting
This section provides information on how to monitor congestion control.
Congestion Control Show Command(s) and/or Outputs
This section provides information regarding show commands and/or their outputs in support of enhanced congestion control.
show congestion-control statistics mme
show congestion-control statistics mme [ full | critical | major | minor ]
The following output is a concise listing of congestion control statistics. In this example output, only the Critical information is shown.
Critical Congestion Policy Action Congestion Policy Applied : 0 times PS attaches Rejected : 0 times Dropped : 0 times PS attaches Rejected : 0 times Dropped : 0 times Combined attaches Rejected : 0 times Dropped : 0 times S1-Setup Rejected : 0 times Dropped : 0 times Handover Rejected : 0 times Dropped : 0 times Addn-pdn-connect Rejected : 0 times Dropped : 0 times Addn-brr-connect Rejected : 0 times Dropped : 0 times Service-Request Rejected : 0 times Dropped : 0 times TAU-Request Rejected : 0 times Dropped : 0 times S1AP Overload Start Sent : 2 times S1AP Overload Stop Sent : 2 times Excluded Emergency Events : 0 times Excluded Voice Events : 0 times
show congestion-control statistics mme
show snmp trap statistics verbose | grep EnhancedCongestion