Traffic Policing and Shaping


Traffic Policing and Shaping
 
 
 
This chapter describes the support of per subscriber Traffic Policing and Shaping feature on ST16 and Cisco® ASR 5000 Chassis and explains the commands and RADIUS attributes that are used to implement this feature. The product Administration Guides provide examples and procedures for configuration of basic services on the system. It is recommended that you select the configuration example that best meets your service model, and configure the required elements for that model, as described in the respective product Administration Guide, before using the procedures in this chapter.
This chapter included following procedures:
 
Overview
This section describes the traffic policing and shaping feature for individual subscriber. This feature is comprises of two functions:
 
 
Traffic Policing
Traffic policing enables the configuring and enforcing of bandwidth limitations on individual subscribers and/or APN of a particular traffic class in 3GPP/3GPP2 service.
 
Bandwidth enforcement is configured and enforced independently on the downlink and the uplink directions.
A Token Bucket Algorithm (a modified trTCM) [RFC2698] is used to implement the Traffic-Policing feature. The algorithm used measures the following criteria when determining how to mark a packet:
Committed Data Rate (CDR): The guaranteed rate (in bits per second) at which packets can be transmitted/received for the subscriber during the sampling interval.
Peak Data Rate (PDR): The maximum rate (in bits per second) that subscriber packets can be transmitted/received for the subscriber during the sampling interval.
Burst-size: The maximum number of bytes that can be transmitted/received for the subscriber during the sampling interval for both committed (CBS) and peak (PBS) rate conditions. This represents the maximum number of tokens that can be placed in the subscriber’s “bucket”. Note that the committed burst size (CBS) equals the peak burst size (PBS) for each subscriber.
The system can be configured to take any of the following actions on packets that are determined to be in excess or in violation:
Drop: The offending packet is discarded.
Transmit: The offending packet is passed.
Lower the IP Precedence: The packet’s ToS bit is set to “0”, thus downgrading it to Best Effort, prior to passing the packet. Note that if the packet’s ToS bit was already set to “0”, this action is equivalent to “Transmit”.
 
Traffic Shaping
Traffic Shaping is a rate limiting method similar to the Traffic Policing, but provides a buffer facility for packets exceeded the configured limit. Once the packet exceeds the data-rate, the packet queued inside the buffer to be delivered at a later time.
 
The bandwidth enforcement can be done in the downlink and the uplink direction independently. If there is no more buffer space available for subscriber data system can be configured to either drop the packets or kept for the next scheduled traffic session.
 
Traffic Policing Configuration
Traffic Policing is configured on a per-subscriber basis. The subscribers can either be locally configured subscribers on the system or subscriber profiles configured on a remote RADIUS server.
In 3GPP service Traffic policing can be configured for subscribers through APN configuration as well.
Important: In 3GPP service attributes received from the RADIUS server supersede the settings in the APN.
Important: Commands used in the configuration samples in this section provide base functionality to the extent that the most common or likely commands and/or keyword options are presented. In many cases, other optional commands and/or keyword options are available. Refer to the Command Line Interface Reference for complete information regarding all commands.
 
Configuring Subscribers for Traffic Policing
 
Important: Instructions for configuring RADIUS-based subscriber profiles are not provided in this document. Please refer to the documentation supplied with your server for further information.
Step 1
Step a
 
configure
  context <context_name>
     subscriber name <user_name>
        qos traffic-police direction downlink
        end
Step b
 
configure
  context <context_name>
     subscriber name <user_name>
        qos traffic-police direction uplink
        end
Notes:
There are numerous keyword options associated with the qos traffic-police direction { downlink | uplink } command.
Important: If the exceed/violate action is set to “lower-ip-precedence”, the TOS value for the outer packet becomes “best effort” for packets that exceed/violate the traffic limits regardless of what the ip user-datagram-tos-copy command in the Subscriber Configuration mode is configured to. In addition, the “lower-ip-precedence” option may also override the configuration of the ip qos-dscp command (also in the Subscriber Configuration mode). Therefore, it is recommended that command not be used when specifying this option.
Step 2
context <context_name>
  show subscriber configuration username <user_name>
Step 3
Save the configuration as described in the Verifying and Saving Your Configuration chapter.
 
Configuring APN for Traffic Policing in 3GPP Networks
This section provides information and instructions for configuring APN template’s QoS profile in support of Traffic Policing.
 
The profile information is sent to the SGSN(s) in response to GTP Create/Update PDP Context Request messages. If the QoS profile requested by the SGSN is lower than the configured QoS profile configured, the profile requested by the SGSN is used. If the QoS profile requested by the SGSN is higher, the configured rates are used.
Note that values for the committed-data-rate and peak-data-rate parameters are exchanged in the GTP messages between the GGSN and the SGSN. Therefore, the values used may be lower than the configured values. When negotiating the rate with the SGSN(s), the system convert this to a value that is permitted by GTP as shown in the table below.
Permitted Values for Committed and Peak Data Rates in GTP Messages
Step 1
 
configure
  context <context_name>
     apn <apn_name>
        qos rate-limit downlink
        end
 
configure
  context <context_name>
     apn <apn_name>
        qos rate-limit uplink
        end
Notes:
There are numerous keyword options associated with qos rate-limit { downlink | uplink } command.
Optionally, configure the maximum number of PDP contexts that can be facilitated by the APN to limit the APN’s bandwidth consumption by entering the following command in the configuration:
max-contents primary <number> total <total_number>
Important: If a “subscribed” traffic class is received, the system changes the class to background and sets the following: The uplink and downlink guaranteed data rates are set to 0. If the received uplink or downlink data rates are 0 and traffic policing is disabled, the default of 64 kbps is used. When enabled, the APN configured values are used. If the configured value for downlink max data rate is larger than can fit in an R4 QoS profile, the default of 64 kbps is used. If either the received uplink or downlink max data rates is non-zero, traffic policing is employed if enabled for the background class. The received values are used for responses when traffic policing is disabled.
Step 2
 
show apn { all | name <apn_name> }
The output is a concise listing of configured APN parameter settings.
Step 3
Save the configuration as described in the Verifying and Saving Your Configuration chapter.
 
Traffic Shaping Configuration
Traffic Shaping is configured on a per-subscriber basis. The subscribers can either be locally configured subscribers on the system or subscriber profiles configured on a remote RADIUS server.
In 3GPP service Traffic policing can be configured for subscribers through APN configuration as well.
Important: In 3GPP, service attributes received from the RADIUS server supersede the settings in the APN.
Important: Commands used in the configuration samples in this section provide base functionality to the extent that the most common or likely commands and/or keyword options are presented. In many cases, other optional commands and/or keyword options are available. Refer to the Command Line Interface Reference for complete information regarding all commands.
 
Configuring Subscribers for Traffic Shaping
This section provides information and instructions for configuring local subscriber profiles on the system to support Traffic Shaping.
 
Important: Instructions for configuring RADIUS-based subscriber profiles are not provided in this document. Please refer to the documentation supplied with your server for further information.
Step 1
Step a
 
configure
  context <context_name>
     subscriber name <user_name>
        qos traffic-shape direction downlink
        end
Step b
 
configure
  context <context_name>
     subscriber name <user_name>
        qos traffic-shape direction uplink
        end
Notes:
There are numerous keyword options associated with qos traffic-shape direction { downlink | uplink } command.
Important: If the exceed/violate action is set to “lower-ip-precedence”, the TOS value for the outer packet becomes “best effort” for packets that exceed/violate the traffic limits regardless of what the ip user-datagram-tos-copy command in the Subscriber Configuration mode is configured to. In addition, the “lower-ip-precedence” option may also override the configuration of the ip qos-dscp command (also in the Subscriber Configuration mode). Therefore, it is recommended that command not be used when specifying this option.
Step 2
 
context <context_name>
  show subscriber configuration username <user_name>
Step 3
Save the configuration as described in the Verifying and Saving Your Configuration chapter.
 
Configuring APN for Traffic Shaping in 3GPP Networks
This section provides information and instructions for configuring APN template’s QoS profile in support of Traffic Shaping.
 
The profile information is sent to the SGSN(s) in response to GTP Create/Update PDP Context Request messages. If the QoS profile requested by the SGSN is lower than the configured QoS profile configured, the profile requested by the SGSN is used. If the QoS profile requested by the SGSN is higher, the configured rates are used.
Note that values for the committed-data-rate and peak-data-rate parameters are exchanged in the GTP messages between the GGSN and the SGSN. Therefore, the values used may be lower than the configured values. When negotiating the rate with the SGSN(s), the system convert this to a value that is permitted by GTP as shown in the following table.
Permitted Values for Committed and Peak Data Rates in GTP Messages
Step 1
Step a
 
configure
  context <context_name>
     subscriber name <user_name>
        qos rate-limit downlink
        end
Step b
 
configure
  context <context_name>
     apn <apn_name>
        qos rate-limit uplink
        end
Step 2
Optional. Configure the maximum number of PDP contexts that can be facilitated by the APN to limit the APN’s bandwidth consumption by entering the following command in the configuration:
 
configure
  context <context_name>
     apn <apn_name>
        max-contexts primary <number> total <total_number>
        end
Notes:
There are numerous keyword options associated with qos rate-limit direction { downlink | uplink } command.
For more information on commands, refer Command Line Interface Reference
If the exceed/violate action is set to lower-ip-precedence, this command may override the configuration of the ip qos-dscp command in the GGSN service configuration mode for packets from the GGSN to the SGSN. In addition, the GGSN service ip qos-dscp command configuration can override the APN setting for packets from the GGSN to the Internet. Therefore, it is recommended that command not be used in conjunction with this action.
Step 3
 
show apn { all | name <apn_name> }
The output is a concise listing of configured APN parameter settings.
Step 4
Save the configuration as described in the Verifying and Saving Your Configuration chapter.
 
RADIUS Attributes
 
Traffic Policing for CDMA Subscribers
The RADIUS attributes listed in the following table are used to configure Traffic Policing for CDMA subscribers (PDSN, HA) configured on remote RADIUS servers. More information on these attributes can be found in the AAA Interface Administration and Reference.
RADIUS Attributes Required for Traffic Policing Support for CDMA Subscribers
NOTE: It is recommended that this parameter be configured to at least the greater of the following two values: 1) 3 times greater than packet MTU for the subscriber connection, OR 2) 3 seconds worth of token accumulation within the “bucket” for the configured peak-data-rate.
NOTE: It is recommended that this parameter be configured to at least the greater of the following two values: 1) 3 times greater than packet MTU for the subscriber connection, OR 2) 3 seconds worth of token accumulation within the “bucket” for the configured peak-data-rate.
 
Traffic Policing for UMTS Subscribers
The RADIUS attributes listed in the following table are used to configure Traffic Policing for UMTS subscribers configured on remote RADIUS servers. More information on these attributes can be found in the AAA Interface Administration and Reference.
RADIUS Attributes Required for Traffic Policing Support for UMTS Subscribers
 

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