Regulating Packet Flow on a Per-Interface Basis Using Generic Traffic Shaping

Last Updated: September 06, 2011

Packet flow on a network can be regulated using a traffic shaping mechanism. One such traffic shaping mechanism is a Cisco feature called Generic Traffic Shaping (GTS). Generic Traffic Shaping allows you to regulate the flow of packets going out an interface or subinterface, matching the packet flow to the speed of the interface. This module describes the concepts and tasks related to configuring Generic Traffic Shaping.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Prerequisites for Configuring Generic Traffic Shaping

  • Be familiar with the concepts in the "Regulating Packet Flow Using Traffic Shaping" module.
  • Use Feature Navigator to determine if the platform in use supports GTS. Access Cisco Feature Navigator at http://www.cisco.com/go/fn .

Restrictions for Configuring Generic Traffic Shaping

  • GTS is not supported on the following interfaces:
    • Multilink PPP (MLP) interfaces
    • Integrated Services Digital Networks (ISDNs), dialer interfaces, or generic routing encapsulation (GRE) tunnel interfaces on the Cisco 7500 series router
  • GTS is not supported with flow switching.

Information About Configuring Generic Traffic Shaping

Generic Traffic Shaping Functionality

GTS is a traffic shaping mechanism (also known as a "traffic shaper"). A traffic shaper typically delays excess traffic using a buffer, or queueing mechanism, to hold packets and shape the flow when the data rate of the source is higher than expected. It holds and shapes traffic to a particular bit rate by using the token bucket mechanism. See the "Regulating Packet Flow Using Traffic Shaping" module.


Note
GTS is similar to Class-Based Traffic Shaping. Although Class-Based Traffic Shaping is the Cisco-recommended mechanism, GTS is still supported.

GTS supports traffic shaping on most media and encapsulation types on the router.

GTS works with a variety of Layer 2 technologies, including Frame Relay, ATM, Switched Multimegabit Data Service (SMDS), and Ethernet.

GTS performs the following tasks:

  • Applies traffic shaping on a per-interface basis and uses access control lists (ACLs) to select the traffic to shape.
  • On a Frame Relay subinterface, dynamically adapts to available bandwidth by integrating backward explicit congestion notification (BECN) signals, or shapes to a specified rate. This is known as adaptive GTS.
  • On an ATM/ATM Interface Processor (AIP) interface, responds to the Resource Reservation Protocol (RSVP) feature signalled over statically configured ATM permanent virtual circuits (PVCs).

Adaptive Generic Traffic Shaping on Frame Relay Networks

If adaptive GTS is configured 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.

With adaptive GTS, the router uses backward explicit congestion notifications (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 two commands on both ends of the network link, enabling the router at the high-speed end to detect and adapt to congestion even when traffic is flowing primarily in one direction.

For more information about configuring adaptive GTS, see the Configuring Adaptive Generic Traffic Shaping for Frame Relay Networks.

Access Control List Functionality and Generic Traffic Shaping

Access control lists filter network traffic by controlling whether routed packets are forwarded or blocked at the router interface. When configured with GTS, the router examines each packet to determine how to shape the traffic on the basis of the criteria you specified for the access control list.

Access control list criteria could be the source address of the traffic, the destination address of the traffic, the upper-layer protocol, or other information. Note that sophisticated users can sometimes successfully evade or fool basic access control lists because no authentication is required.

Benefits of Generic Traffic Shaping

All of the benefits associated with traffic shaping also apply to GTS. For information about the benefits of traffic shaping, see the "Regulating Packet Flow Using Traffic Shaping" module.

How to Configure Generic Traffic Shaping

Configuring Generic Traffic Shaping on an Interface

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type number

4.    traffic-shape rate bit-rate [burst-size] [excess-burst-size] [buffer-limit]

5.    end

6.    show traffic-shape [interface-type interface-number]

7.    show traffic-shape statistics [interface-type interface-number]

8.    exit


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
interface type number


Example:

Router(config)# interface s4/0

 

Configures an interface (or subinterface) type and enters interface configuration mode.

  • Enter the interface type number.
 
Step 4
traffic-shape rate bit-rate [burst-size] [excess-burst-size] [buffer-limit]


Example:

Router(config-if)# traffic-shape rate 128000

 

Enables traffic shaping for outbound traffic on an interface based on the bit rate specified.

  • Enter the bit rate.
 
Step 5
end


Example:

Router(config-if)# end

 

Returns to privileged EXEC mode.

 
Step 6
show traffic-shape [interface-type interface-number]


Example:

Router# show traffic-shape serial4/0

 

(Optional) Displays the current traffic-shaping configuration.

 
Step 7
show traffic-shape statistics [interface-type interface-number]


Example:

Router# show traffic-shape statistics serial4/0

 

(Optional) Displays the current traffic-shaping statistics.

 
Step 8
exit


Example:

Router# exit

 

(Optional) Exits privileged EXEC mode.

 

Configuring Generic Traffic Shaping Using an Access Control List

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    access-list access-list-number {deny | permit} source [source-wildcard]

4.    interface type number

5.    traffic-shape group access-list bit-rate [burst-size [excess-burst-size]]

6.    end

7.    show traffic-shape [interface-type interface-number]

8.    show traffic-shape statistics [interface-type interface-number]

9.    exit


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
access-list access-list-number {deny | permit} source [source-wildcard]


Example:

Router(config)# access-list 1 permit 192.5.34.0 0.0.0.255

 

Shapes traffic according to specified access list.

  • Enter the access list number, one of the required keywords, and the source information.
 
Step 4
interface type number


Example:

Router(config)# interface s4/0

 

Configures an interface (or subinterface) type and enters interface configuration mode.

  • Enter the interface type number.
 
Step 5
traffic-shape group access-list bit-rate [burst-size [excess-burst-size]]


Example:

Router(config-if)# traffic-shape group 101 128000

 

Enables traffic shaping based on a specific access list for outbound traffic on an interface.

  • Enter the access list number and the bit rate.
 
Step 6
end


Example:

Router(config-if)# end

 

Returns to privileged EXEC mode.

 
Step 7
show traffic-shape [interface-type interface-number]


Example:

Router# show traffic-shape serial4/0

 

(Optional) Displays the current traffic-shaping configuration.

 
Step 8
show traffic-shape statistics [interface-type interface-number]


Example:

Router# show traffic-shape statistics serial4/0

 

(Optional) Displays the current traffic-shaping statistics.

 
Step 9
exit


Example:

Router# exit

 

(Optional) Exits privileged EXEC mode.

 
What to Do Next


Note
Repeat the above procedure for each additional type of traffic you want to shape.

Configuring Adaptive Generic Traffic Shaping for Frame Relay Networks

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type number

4.    traffic-shape rate bit-rate [burst-size] [excess-burst-size] [buffer-limit]

5.    traffic-shape adaptive bit-rate

6.    traffic-shape fecn-adapt

7.    end

8.    show traffic-shape [interface-type interface-number]

9.    show traffic-shape statistics [interface-type interface-number]

10.    exit


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
interface type number


Example:

Router(config)# interface s4/0

 

Configures an interface (or subinterface) type and enters interface configuration mode.

  • Enter the interface type number.
 
Step 4
traffic-shape rate bit-rate [burst-size] [excess-burst-size] [buffer-limit]


Example:

Router(config-if)# traffic-shape rate 128000

 

Enables traffic shaping for outbound traffic on an interface based on the bit rate specified.

  • Enter the bit rate.
 
Step 5
traffic-shape adaptive bit-rate


Example:

Router(config-if)# traffic-shape adaptive 64000

 

Configures a Frame Relay subinterface to estimate the available bandwidth when BECNs are received.

  • Enter the bit rate.
 
Step 6
traffic-shape fecn-adapt


Example:

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

 

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

 
Step 7
end


Example:

Router(config-if)# end

 

Returns to privileged EXEC mode.

 
Step 8
show traffic-shape [interface-type interface-number]


Example:

Router# show traffic-shape serial4/0

 

(Optional) Displays the current traffic-shaping configuration.

 
Step 9
show traffic-shape statistics [interface-type interface-number]


Example:

Router# show traffic-shape statistics serial4/0

 

(Optional) Displays the current traffic-shaping statistics.

 
Step 10
exit


Example:

Router# exit

 

(Optional) Exits privileged EXEC mode.

 

Configuration Examples for Generic Traffic Shaping

Example Generic Traffic Shaping on an Interface Configuration

The following is an example of GTS configured on serial interface s4/0:

        
          enable
        
      
        
          configure terminal
      
 interface s4/0 
  traffic-shape rate 128000
  end 
 
      
 
     
 
     
 
      
 
      
 
     
 
    
 
    
 
      
       
     
Example Generic Traffic Shaping Using an Access Control List Configuration
 
     
 
      
 
        
         
       
 The following is an example of GTS configured using an ACL. In this example, GTS is configured for the outbound traffic on ACL 1.
 
       
        
          enable
        
      
 
       
        
          configure terminal
      
 
       
 access-list 1 permit 192.5.34.0 0.0.0.255
 
       
 interface s4/0
 
 
       
  traffic-shape group 101 128000
 
       
  end 
 
       
 
      
 
     
 
     
 
      
 
      
 
     
 
    
 
    
 
      
       
     
Example Adaptive Generic Traffic Shaping for a Frame Relay Network Configuration
 
     
 
      
 
        
         
       
 The following is an example of adaptive GTS configured on Frame Relay network. In this example, adaptive GTS is configured using the traffic-shaperate command. The traffic-shapeadaptive command specifies the minimum bit rate to which the traffic is shaped. The actual maximum transmission rate will be between the rate specified in the traffic-shapeadaptive command and the rate specified in the traffic-shaperate command.
 
       
        
          enable
        
      
 
       
        
          configure terminal
      
 
       
 interface s4/0 
 
       
  traffic-shape rate 128000
 
       
  traffic-shape adaptive 64000
 
       
  traffic-shape fecn-adapt
 
       
  end 
 
       
 
      
 
     
 
     
 
      
 
      
 
     
 
    
 
   
 
   
 
     
      
    
Where to Go Next
 
    
 
     
 To configure Class-Based Traffic Shaping, see the "Regulating Packet Flow on a Per-Class Basis Using Class-Based Traffic Shaping" module. 
 
     
 To configure Frame Relay Traffic Shaping (FRTS), see the "MQC-Based Frame Relay Traffic Shaping" module. 
 
    
 
    
 
     
 
     
 
    
 
   
 
   
 
     
      
    
Additional References
 
    
 
     
 
       
        
     
 
     
 
       
        
      
Related Documents
 
      
 
        
         
       
 
         
         
 
           
 Related Topic
 		 
           
 Document Title
 		 
         
 
         
         
         
 
           
 Cisco IOS commands
 		 
           
 Cisco IOS Master Commands List, All Releases 
 		 
         
 
         
 
           
 QoS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples
 		 
           
 Cisco IOS Quality of Service Solutions Command Reference 
 		 
         
 
         
 
           
 Overview information about using traffic shaping to regulate packet flow on a network
 		 
           
 "Regulating Packet Flow Using Traffic Shaping" module
 		 
         
 
         
 
           
 Class-Based Traffic Shaping
 		 
           
 "Regulating Packet Flow on a Per-Class Basis Using Class-Based Traffic Shaping" module
 		 
         
 
         
 
           
 FRTS
 		 
           
 "MQC-Based Frame Relay Traffic Shaping" module
 		 
         
 
         
       
 
      
 
     
 
     
 
       
        
      
Standards
 
      
 
        
         
       
 
         
         
 
           
 Standard
 		 
           
 Title
 		 
         
 
         
         
         
 
           
 No new or modified standards are supported, and support for existing standards has not been modified.
 		 
           
 --
 		 
         
 
         
       
 
      
 
     
 
     
 
       
        
      
MIBs
 
      
 
        
         
       
 
         
         
 
           
 MIB
 		 
           
 MIBs Link
 		 
         
 
         
         
         
 
           
 No new or modified MIBs are supported, and support for existing MIBs has not been modified.
 
 
 		 
           
 To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
 
 http://www.cisco.com/go/mibs 
 		 
         
 
         
       
 
      
 
     
 
     
 
       
        
      
RFCs
 
      
 
        
         
       
 
         
         
 
           
 RFC
 		 
           
 Title
 		 
         
 
         
         
         
 
           
 No new or modified RFCs are supported, and support for existing RFCs has not been modified. 
 		 
           
 --
 		 
         
 
         
       
 
      
 
     
 
     
 
       
        
      
Technical Assistance
 
      
 
        
         
       
 
         
         
 
           
 Description
 		 
           
 Link
 		 
         
 
         
         
         
 
           
 The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. 
 		 
           
 http://www.cisco.com/cisco/web/support/index.html 
 		 
         
 
         
       
 
      
 
     
 
    
 
    
 
     
 
     
 
    
 
   
 
   
 
     
      
    
Feature Information for Generic Traffic Shaping
 
    
 
     
 
       
        
      
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature. 
 
      
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required. 
 
     
 
     
 
       
        
      
 
        
         
       
 
         
         
 
          Table 1 
          Feature Information for Generic Traffic Shaping  
         
 
         
       
 
       
 
         
         
 
           
 Feature Name 
 		 
           
 Software Releases 
 		 
           
 Feature Configuration Information 
 		 
         
 
         
         
         
 
           
 Generic Traffic Shaping 
 		 
           
 12.2(1) 15.0(1)S Cisco IOS XE 3.1.0 SG 
 		 
           
 This feature was introduced. This feature was integrated into the Cisco IOS Release 15.0(1)S. 
 
 In Cisco IOS XE 3.1.0 SG, this feature was integrated. 
 		 
         
 
         
       
 
      
 
     
 
    
 
    
 
     
 
     
 
    
 
   
 
   
 
     
      
    
 
 
    
 
     
 
       
        
      
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R) 
 
      
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.