Table Of Contents
Adaptive Frame Relay Traffic Shaping for Interface Congestion
Related Features and Technologies
Supported Standards, MIBs, and RFCs
Configuring Frame Relay Adaptive Traffic Shaping for Interface Congestion
Verifying Frame Relay Adaptive Traffic Shaping for Interface Congestion
Frame Relay Adaptive Traffic Shaping for Interface Congestion Example
Adaptive Frame Relay Traffic Shaping for Interface Congestion
Feature History
This document describes the Adaptive Frame Relay Traffic Shaping for Interface Congestion feature in Cisco IOS Release 12.2(4)T. It includes the following sections:
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Supported Standards, MIBs, and RFCs
Feature Overview
The Adaptive Frame Relay Traffic Shaping for Interface Congestion feature enhances Frame Relay traffic shaping functionality by adjusting permanent virtual circuit (PVC) sending rates based on interface congestion. When this new feature is enabled, the traffic-shaping mechanism monitors interface congestion. When the congestion level exceeds a configured value called queue depth, the sending rate of all PVCs is reduced to the minimum committed information rate (minCIR). As soon as interface congestion drops below the queue depth, the traffic-shaping mechanism changes the sending rate of the PVCs back to the committed information rate (CIR). This process guarantees the minCIR for PVCs when there is interface congestion.
Note
This new feature works in conjunction with backward explicit congestion notification (BECN) and Foresight functionality. If interface congestion exceeds the queue depth when adaptive shaping for interface congestion is enabled along with BECN or ForeSight, then the PVC sending rate is reduced to the minCIR. When interface congestion drops below the queue depth, then the sending rate is adjusted in response to BECN or ForeSight.
Before the introduction of this feature, interface congestion caused packets to be delayed or dropped at the interface. The Adaptive Frame Relay Traffic Shaping for Interface Congestion feature helps ensure that packet drop occurs at the virtual circuit (VC) queues. When used with FRF.12 fragmentation, this feature also ensures that packets are dropped before fragmentation occurs.
Benefits
The Adaptive Frame Relay Traffic Shaping for Interface Congestion feature
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Restrictions
This feature is supported on terminated and switched PVCs. It is not supported on switched virtual circuits (SVCs).
Related Features and Technologies
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Related Documents
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Supported Platforms
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Platform Support Through Feature Navigator
Cisco IOS software is packaged in feature sets that support specific platforms. To get updated information regarding platform support for this feature, access Feature Navigator. Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature.
Feature Navigator is a web-based tool that enables you to quickly determine which Cisco IOS software images support a specific set of features and which features are supported in a specific Cisco IOS image.
To access Feature Navigator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions at http://www.cisco.com/register.
Feature Navigator is updated when major Cisco IOS software releases and technology releases occur. As of May 2001, Feature Navigator supports M, T, E, S, and ST releases. You can access Feature Navigator at the following URL:
http://www.cisco.com/go/fn
Supported Standards, MIBs, and RFCs
Standards
No new or modified standards are supported by this feature.
MIBs
No new or modified MIBs are supported by this feature.
To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
RFCs
No new or modified RFCs are supported by this feature.
Prerequisites
In order to use the Adaptive Frame Relay Traffic Shaping for Interface Congestion feature, Frame Relay traffic shaping must be enabled on the interface.
Configuration Tasks
See the following sections for configuration tasks for the Adaptive Frame Relay Traffic Shaping for Interface Congestion feature. Each task in the list is identified as either required or optional.
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Configuring Frame Relay Adaptive Traffic Shaping for Interface Congestion
To configure a map class for adaptive traffic shaping for interface congestion, use the following commands beginning in global configuration mode:
Verifying Frame Relay Adaptive Traffic Shaping for Interface Congestion
Step 1
The following is sample output from the show frame-relay pvc command:
Router# show frame-relay pvc 41PVC Statistics for interface Serial1 (Frame Relay DTE)DLCI = 41, DLCI USAGE = LOCAL, PVC STATUS = DELETED, INTERFACE = Serial1.1input pkts 0 output pkts 0 in bytes 0out bytes 0 dropped pkts 0 in FECN pkts 0in BECN pkts 0 out FECN pkts 0 out BECN pkts 0in DE pkts 0 out DE pkts 0out bcast pkts 0 out bcast bytes 0pvc create time 4d22h, last time pvc status changed 4d22hcir 56000 bc 7000 be 0 byte limit 875 interval 125mincir 28000 byte increment 875 Adaptive Shaping IF_CONGpkts 0 bytes 0 pkts delayed 0 bytes delayed 0shaping inactivetraffic shaping drops 0Queueing strategy:fifoOutput queue 0/40, 0 drop, 0 dequeuedStep 2
Note
The following is sample output from the show interfaces serial command for an interface that is configured with adaptive traffic shaping for interface congestion with a queue depth of 10 packets. The "Output queue" field indicates 10 packets in the interface queue.
Router# show interfaces serial 2
Serial2 is up, line protocol is upHardware is HD64570Internet address is 2.0.0.2/8MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,reliability 255/255, txload 10/255, rxload 10/255Encapsulation FRAME-RELAY, loopback not setKeepalive not setFR SVC disabled, LAPF state downBroadcast queue 0/64, broadcasts sent/dropped 0/0, interface broadcasts 0Last input 00:06:55, output 00:00:00, output hang neverLast clearing of "show interface" counters 00:11:01Queueing strategy:fifoOutput queue 10/40, 6731 drops; input queue 24/75, 0 drops...
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Configuration Examples
This section provides the following configuration example:
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Frame Relay Adaptive Traffic Shaping for Interface Congestion Example
In the following example, the rate of traffic destined for PVC 200 will be reduced to the minCIR if the number of packets in the interface queue exceeds 10. When the number of packets in the interface queue drops below 10, then the traffic rate will immediately return to the CIR.interface serial0encapsulation frame-relayframe-relay traffic-shapingframe-relay interface-dlci 200class adjust_vc_class_rate!map-class frame-relay adjust_vc_class_rateframe-relay cir 64000frame-relay mincir 32000frame-relay adaptive-shaping interface-congestion 10Command Reference
This section documents the modified frame-relay adaptive-shaping command that configures the Adaptive Frame Relay Traffic Shaping for Interface Congestion feature. All other commands used with this feature are documented in the Cisco IOS Release 12.2 command reference publications.
frame-relay adaptive-shaping
To enable Frame Relay adaptive traffic shaping, use the frame-relay adaptive-shaping command in map-class configuration mode. To disable adaptive traffic shaping, use the no form of this command.
frame-relay adaptive-shaping {[becn | foresight] | [interface-congestion [queue-depth]]}
no frame-relay adaptive-shaping {[becn | foresight] | [interface-congestion]}
Syntax Description
Defaults
Frame Relay adaptive traffic shaping is not enabled by default.
The default queue depth is 0 packets.
Command Modes
Static maps class configuration
Command History
11.3
This command was introduced.
12.2(4)T
This command was modified to configure adaptive traffic shaping for interface congestion.
Usage Guidelines
This command replaces the frame-relay becn-response-enable command. If you use the frame-relay becn-response-enable command in scripts, you should replace it with the frame-relay adaptive-shaping command.
The frame-relay adaptive-shaping command configures a router to adjust virtual circuit (VC) sending rates in response to BECN or ForeSight backward congestion notification messages or interface congestion.
Include this command in a map-class definition and apply the map class either to the main interface or to a subinterface.
Adaptive traffic shaping for interface congestion can be configured along with BECN or ForeSight. When adaptive shaping for interface congestion is used with BECN or ForeSight, if interface congestion exceeds the queue-depth, then the PVC send rate is reduced to minCIR. When interface congestion drops below the queue-depth, then the send rate is adjusted in response to BECN or ForeSight.
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Examples
ForeSight Example
This example shows the map-class definition for a router configured with traffic shaping and Router ForeSight enabled:
interface Serial0no ip addressencapsulation frame-relayframe-relay traffic-shapingframe-relay class control-A!map-class frame-relay control-Aframe-relay adaptive-shaping foresightframe-relay cir 56000frame-relay bc 64000Adaptive Shaping for Interface Congestion Example
In the following example, the queue depth is set at 10 packets. If the number of packets in the interface queue exceeds 10, the rate of traffic destined for PVC 200 will be reduced to the minCIR. When the number of packets in the interface queue drops below 10, then the traffic rate will immediately return to the CIR.interface serial0encapsulation frame-relayframe-relay traffic-shapingframe-relay interface-dlci 200class adjust_vc_class_rate!map-class frame-relay adjust_vc_class_rateframe-relay cir 64000frame-relay mincir 32000frame-relay adaptive-shaping interface-congestion 10Related Commands
Glossary
BECN—backward explicit congestion notification. Bit set by a Frame Relay network in frames traveling in the opposite direction of frames encountering a congested path. DTE receiving frames with the BECN bit set can request that higher-level protocols take flow control action as appropriate.
CIR—committed information rate. The rate at which a Frame Relay network agrees to transfer information under normal conditions, averaged over a minimum increment of time. CIR, measured in bits per second, is one of the key negotiated traffic metrics.
ForeSight—A network traffic control feature used in Cisco switches. When the ForeSight feature is enabled on the switch, the switch will periodically send out a ForeSight message. When a Cisco router receives a ForeSight message indicating that certain data-link connection identifiers (DLCIs) are experiencing congestion, the router reacts by activating its traffic-shaping function to slow down the output rate.
FRF.12—An implementation agreement developed to allow long data frames to be fragmented into smaller pieces and interleaved with real-time frames. In this way, real-time voice and nonreal-time data frames can be carried together on lower-speed links without causing excessive delay to the real-time traffic.
minCIR—The minimum acceptable incoming or outgoing committed information rate (CIR) for a Frame Relay virtual circuit.
PVC—permanent virtual circuit or connection. A virtual circuit that is permanently established. PVCs save bandwidth associated with circuit establishment and teardown in situations where certain virtual circuits must exist all the time.
SVC—switched virtual circuit. Virtual circuit that is dynamically established on demand and is torn down when transmission is complete. SVCs are used in situations where data transmission is sporadic.
Guest
