Cisco IOS Quality of Service Solutions Configuration�Guide, Release�12.2
Configuring Generic Traffic Shaping
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Configuring Generic Traffic Shaping

Table Of Contents

Configuring Generic Traffic Shaping

Generic Traffic Shaping Configuration Task List

Configuring GTS

Configuring GTS for an Access List

Configuring Adaptive GTS for Frame Relay Networks

Monitoring the GTS Configuration

Generic Traffic Shaping Configuration Examples

GTS Enabled on the Interface Example

Constrained Access Rate Example

Different Controlled Rates Through an IP Internet Example

Frame Relay Adaptability to Congestion Example

Different Accommodated Access Speeds Example


Configuring Generic Traffic Shaping


This chapter describes the tasks for configuring the Generic Traffic Shaping (GTS) feature on a router.

For complete conceptual information, see the section "Traffic Shaping" in the chapter "Policing and Shaping Overview" in this book.

For a complete description of the GTS commands mentioned in this chapter, refer to the Cisco IOS Quality of Service Solutions Command Reference. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.

To identify the hardware platform or software image information associated with a feature, use the Feature Navigator on Cisco.com to search for information about the feature or refer to the software release notes for a specific release. For more information, see the "Identifying Supported Platforms" section in the "Using Cisco IOS Software" chapter in this book.


Note GTS is not supported on Integrated Services Digital Networks (ISDNs), dialup interfaces, or generic routing encapsulation (GRE) tunnel interfaces on the Cisco 7500 series router. Traffic shaping is not supported with flow switching.


Generic Traffic Shaping Configuration Task List

To configure GTS, perform the tasks described in the following sections. The task in the first section is required; the tasks in the remaining sections are optional.

Configuring GTS (Required)

Configuring GTS for an Access List (Optional)

Configuring Adaptive GTS for Frame Relay Networks (Optional)

Monitoring the GTS Configuration (Optional)

See the end of this chapter for the section "Generic Traffic Shaping Configuration Examples."

Configuring GTS

To configure GTS for outbound traffic on an interface or subinterface, use the following command in interface configuration mode:

Command
Purpose

Router(config-if)# traffic-shape rate bit-rate [burst-size [excess-burst-size]]

Configures traffic shaping for outbound traffic on an interface.


Configuring GTS for an Access List

To configure GTS for outbound traffic on an access list, use the following commands beginning in global configuration mode:

 
Command
Purpose

Step 1 

Router(config)# access-list access-list-number

Assigns traffic to an access list.

Step 2 

Router(config-if)# interface interface-type interface-number

Enters interface configuration mode.

Step 3 

Router(config-if)# traffic-shape group access-list-number bit-rate [burst-size [excess-burst-size]]

Configures traffic shaping for outbound traffic on an interface for the specified access list.

Repeat the steps for each type of traffic you want to rate-limit.

Configuring Adaptive GTS for Frame Relay Networks

If traffic shaping is performed on a Frame Relay network using the traffic-shape rate command, you can also use the traffic-shape adaptive command to specify the minimum bit rate to which the traffic is shaped.

To configure adaptive GTS for outbound traffic on an interface or subinterface, use the following commands in interface configuration mode:

 
Command
Purpose

Step 1 

Router(config-if)# traffic-shape rate bit-rate [burst-size [excess-burst-size]]

Enables traffic shaping for outbound traffic on an interface.

Step 2 

Router(config-if)# traffic-shape adaptive[bit-rate]

Configures minimum bit rate to which traffic is shaped when backward explicit congestion notifications (BECNs) are received on an interface.

Step 3 

Router(config-if)# traffic-shape fecn-adapt

Configures reflection of forward explicit congestion notifications (FECNs) as BECNs.

With adaptive GTS, the router uses BECNs to estimate the available bandwidth and adjust the transmission rate accordingly. The actual maximum transmission rate will be between the rate specified in the traffic-shape adaptive command and the rate specified in the traffic-shape rate command.

Configure these commands on both ends of the link, enabling the router at the high-speed end to detect and adapt to congestion even when traffic is flowing primarily in one direction.

Monitoring the GTS Configuration

To monitor the current traffic shaping configuration and statistics, use the following commands in EXEC mode, as needed:

Command
Purpose

Router# show traffic-shape [interface-name]

Displays the current traffic shaping configuration.

Router# show traffic-shape statistics [interface-name]

Displays the current traffic shaping statistics.


Generic Traffic Shaping Configuration Examples

The following sections provide GTS configuration examples:

GTS Enabled on the Interface Example

Constrained Access Rate Example

Different Controlled Rates Through an IP Internet Example

Frame Relay Adaptability to Congestion Example

Different Accommodated Access Speeds Example

For information on how to configure GTS, see the section "Generic Traffic Shaping Configuration Task List" in this chapter.

GTS Enabled on the Interface Example

This example shows the configuration of two traffic-shaped interfaces on a router. Ethernet interface 0 is configured to limit User Datagram Protocol (UDP) traffic to 1 Mbps. Ethernet interface 1 is configured to limit all output to 5 Mbps.

access-list 101 permit udp any any
interface Ethernet0
 traffic-shape group 101 1000000 125000 125000
!
interface Ethernet1
 traffic-shape rate 5000000 625000 625000

The following is sample output for the show traffic-shape command for this example:

Router# show traffic-shape

Interface   Ethernet0

       Access Target    Byte   Sustain   Excess    Interval  Increment    Adapt
VC     List   Rate      Limit  bits/int  bits/int  (ms)      (bytes)      Active
-      101    1000000   31250  125000    125000    125       15625        -

Interface   Ethernet1

       Access Target    Byte   Sustain   Excess    Interval  Increment    Adapt
VC     List   Rate      Limit  bits/int  bits/int  (ms)      (bytes)      Active
-             5000000   156250 625000    625000    125       78125        -

The following is sample output for the show traffic-shape statistics command for this example:

Router# show traffic-shape statistics

          Access Queue     Packets   Bytes     Packets   Bytes     Shaping
I/F       List   Depth                         Delayed   Delayed   Active
Et0       101    0         2         180       0         0         no
Et1              0         0         0         0         0         no

Constrained Access Rate Example

In this example, a T1 line may be used for 100 milliseconds (ms) in a burst, but the long-term average is limited to 64 kbps. This configuration example restricts the amount of load the system can induce on the outbound network interface.

interface serial 4/1:0
 traffic-shape rate 64000 6400 6400 

If you need to restrict the amount of load the system can induce outbound, and therefore the total load the system can impose on the Internet service provider (ISP), configure traffic shaping on the outbound interfaces.

Different Controlled Rates Through an IP Internet Example

Perhaps you need to restrict the flow of Network News Transfer Protocol (NNTP) to each of some set of sites across an intervening backbone to 64 kbps. This example shows how to configure that control and provide one site with 256 kbps:

access-list 101 permit 10.10.10.10 
access-list 102 permit 10.10.10.20 
access-list 103 permit 10.10.10.30 
!
interface serial 0
 traffic-shape group 101 64000 
 traffic-shape group 102 64000 
 traffic-shape group 103 256000 

Separate token buckets are maintained for each access list, and traffic not matching any access list is not shaped at all.

Frame Relay Adaptability to Congestion Example

This example does not restrict flow across a Frame Relay subinterface that has been layered onto a single data-link connection identifier (DLCI). However, in the presence of BECN bits from the network, the flow is throttled back to the committed information rate (CIR). The access rate of the interface is assumed to be 1544 kbps, and the CIR is 64 kbps.

interface serial 2
 traffic-shape rate 1544000 
 traffic-shape adaptive 64000 
 traffic-shape fecn-adapt

If the traffic-shape fecn-adapt command is configured at both ends of the link, the far end will reflect received FECNs as BECNs in Q.922 TEST RESPONSE messages.

Different Accommodated Access Speeds Example

Frame Relay networks are often asymmetrical, that is, the access rate at one site may differ from the access rate at another. In such cases, it may be worthwhile to configure the faster rate to shape to the access rate of the slower rate, and to respond to BECNs. Using the previous example as a starting point, in which the access rate is 1544 kbps and the CIR is 64 kbps, and the access rate at the far end is 128 kbps, the configuration of the subinterfaces would be as follows:

interface serial 3
 traffic-shape rate 128000 
 traffic-shape adaptive 64000