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

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 caveats and feature information, see Bug Search Tool and 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.

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 ActionPurpose
    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 ActionPurpose
      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 ActionPurpose
        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.
        

                      		

                
        
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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
                
        

                      		

        
        

        

        

    
        

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RFC
        

                      		

                
        
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No new or modified RFCs are supported, and support for existing RFCs has not been modified. 
        

                      		

                
        
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        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.