Performance Routing Configuration Guide, Cisco IOS XE Release 3S
PfR Bandwidth Visibility Distribution for xDSL Access
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PfR Bandwidth Visibility Distribution for xDSL Access

PfR Bandwidth Visibility Distribution for xDSL Access

In a network where the hub and spoke devices are connected via a multipoint tunnel, the hub site does not know about bandwidth limitations at the spoke devices. Without the updated information about bandwidth limitations, Performance Routing (PfR) cannot optimize the application traffic. Usually the spoke device connection to the Internet service provider (ISP) is a DSL connection, which can experience periodic bandwidth changes. PfR bandwidth visibility is a PfR enhancement that provides accurate maximum bandwidth information to peering PfR elements so that accurate policies can be applied automatically.

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 at the end of this module.

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.

Restrictions for PfR Bandwidth Visibility

  • PfR bandwidth resolution is not supported with PfR active mode because there is no throughput data for traffic-classes.
  • PfR does not support spoke-to-spoke tunneling. Disable spoke-to-spoke dynamic tunnels by configuring the ip nhrp server-only command under interface configuration mode as part of the Next Hop Resolution Protocol (NHRP) configuration.

Information About PfR Bandwidth Visibility

ADSL Definition

Digital Subscriber Line (DSL) technology is a modem technology that uses existing twisted pair telephone lines to transport high-bandwidth data, such as multimedia and video, to service subscribers. The term xDSL covers a number of similar yet competing forms of DSL, including Asymmetric DSL (ADSL/ADSL2), Symmetric DSL (SDSL), High Speed DSL (HDSL), Rate Adaptive (RADSL), and Very High Bit Data Rate DSL (VDSL) for delivering up to 52 Mbps downstream.

With Asymmetric DSL, unlike the less common Symmetric DSL, the bandwidth is greater for downloading data than for uploading data.

At the customer end of the connection, a DSL modem converts data from the digital signals used by computers into a voltage signal of a suitable frequency range, which is then applied to the phone line. At the exchange end, a Digital Subscriber Line Access Multiplexer (DSLAM) terminates the DSL circuits and aggregates them, where they are handed off to other networking transports. In the case of ADSL, the voice component is also separated at this step, either by a filter integrated in the DSLAM or by specialized filtering equipment installed before it.

PfR Bandwidth Visibility Challenges

In a network where the hub and spoke devices are connected via a multi-point tunnel, the hub site does not know about bandwidth limitations at the spoke devices. Without the updated information about bandwidth limitations, Performance Routing (PfR) cannot optimize the application traffic. Usually the spoke device connection to the Internet Service Provider (ISP) is a DSL connection, which can experience periodic bandwidth changes. For an example of such a network, see the network diagram below.

Figure 1. Hub and Spoke Devices with ADSL Connnections

PfR can redirect application traffic from one DMVPN/MGRE tunnel to another if the hub-spoke link utilization crosses a configured threshold, but PfR has no visibility into how congested a particular spoke is. There is a need for a mechanism that can discover updated receive (Rx) and transmit (Tx) limits at the spoke side and propagate the limit information to the hub, where the limit information can be used by PfR to effectively manage the application traffic.

Scenarios Creating ADSL Bandwidth Visibility Challenges

There are three main ADSL scenarios which can cause PfR bandwidth visibility challenges:

  • ADSL retrain—Automatic or manual intervention can force the DSLAM into line reconditioning and retraining in which the bandwidth allocation for the line changes. The interventions can occur without notice. For an upwards retrain, the impact on the branch is minimal. For a downwards retrain, the branch can lose bandwidth, a common issue in congested exchanges. The ability to monitor and assess when to move the traffic through another tunnel is key to maintaining a smooth retraining.
  • ADSL congestion—During congested periods, traffic can be held up. Under these circumstances it is imperative that the branch traffic be allowed to take the best possible path—and be distributed as well as possible over all links.
  • ADSL intermittent faults—There are occasions (sometimes quite frequent) when there are intermittent faults that cause minor outages. The investigation of these issues normally takes several working days (no SLA). Significant numbers of these intermittent faults manifest themselves as drops at the higher usage of the “allocated” bandwidth. The ability must exist to effectively change the usage profile of any single tunnel to rebalance the traffic loadings until the ISP has repaired the issue.

PfR Bandwidth Visibility Resolution

Bandwidth visibility is a Performance Routing (PfR) enhancement that provides accurate maximum bandwidth information to peering PfR elements so that accurate policies can be applied automatically. In a network where bandwidth visibility is an issue, there are typically hub and spoke devices connected via a multi-point tunnel, and the hub site does not know about bandwidth limitations at the spoke devices. Without the updated information about bandwidth limitations, PfR cannot optimize the application traffic. Currently the bandwidth limitations are updated manually, but this is not a scalable solution.

PfR bandwidth visibility leverages the existing PfR target discovery feature. The existing SAF-based peering infrastructure can be used to propagate the bandwidth information, as well as target information, from a spoke device to the hub device. On the hub, the PfR master controller builds a database of peers and tracks their maximum receive and transmit bandwidth information. The border routers track the total amount of bandwidth transmitted to a given peer network and report it back to the master controller. If the total amount of bandwidth transmitted to a given peer at any time exceeds certain percentage of the receiving capacity of that peer, PfR can reroute that application traffic to an alternate link, avoiding congestion at the spoke device.


Note


PfR does not support spoke-to-spoke tunneling. Disable spoke-to-spoke dynamic tunnels by configuring the ip nhrp server-only command under interface configuration mode as part of the Next Hop Resolution Protocol (NHRP) configuration.


To enable PfR bandwidth resolution, PfR target discovery must be configured on all devices on which PfR bandwidth-resolution is to be enabled. PfR bandwidth resolution is then enabled on all master controller devices. Both dynamic and static target discovery is supported by PfR bandwidth resolution. After bandwidth resolution is enabled, receive and transmit bandwidth limits are dynamically discovered and propagated using PfR target discovery. A mechanism is available to allow an overwrite of the dynamically discovered limits.


Note


PfR bandwidth resolution is not supported with PfR active mode because there is no throughput data for traffic-classes.


How to Configure PfR Bandwidth Visibility

Configuring PfR Target Discovery and MC Peering for a Hub Site in Multihop Networks

Perform this task to configure PfR master controller (MC) peering at the master controller at the headend of the network, usually a hub site master controller. The master controller must be a device with routing capability. This task assumes a multihop type of network where the network cloud between the hub site and the branch sites is not under the control of the customer or is not SAF-enabled. In this design, the hub site MC will be a Service Advertisement Facility (SAF) forwarder hub with which the branch MC SAF forwarders peer to exchange advertisements. The hub site MC will accept peering requests from branch MCs with the same SAF domain ID and MD5 authentication.


Note


In this task, dynamic PfR target discovery is enabled. This method is desirable when SAF is already enabled in the network for other applications or there is existing neighbor adjacency between MCs and SAF. For example, in a DMVPN WAN, if the PfR MCs coexist on the DMVPN tunnel devices, they also have SAF adjacency and do not require static peering.



Note


PfR does not support spoke-to-spoke tunneling. Disable spoke-to-spoke dynamic tunnels by configuring the ip nhrp server-only command under interface configuration mode as part of the Next Hop Resolution Protocol (NHRP) configuration.


SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    pfr master

    4.    target-discovery

    5.    mc-peer [head-end | peer-address] [loopback interface-number] [description text] [domain domain-id]

    6.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 pfr master


    Example:
    Device(config)# pfr master
     

    Enters PfR master controller configuration mode to configure a Cisco device as a master controller.

     
    Step 4target-discovery


    Example:
    Device(config-pfr-mc)# target-discovery 
     

    Configures PfR target discovery.

    • In this example, dynamic PfR target discovery is configured.
     
    Step 5 mc-peer [head-end | peer-address] [loopback interface-number] [description text] [domain domain-id]


    Example:
    Device(config-pfr-mc)# mc-peer head-end loopback1 description SJ-hub
              
     
    In this example, the PfR master controller peering is configured to show that this device is the hub (headend) device.
    • Use the domain keyword to specify a SAF domain ID to be used for MC peering. The domain-id argument is in the range of 1 to 65535. If the SAF domain ID is not specified, the default value of 59501 is used.
     
    Step 6 end


    Example:
    Device(config-pfr-mc)# end
     

    (Optional) Exits PfR master controller configuration mode and returns to privileged EXEC mode.

     

    Configuring PfR Target Discovery and MC Peering for a Branch Office in Multihop Networks

    Perform this task to configure PfR MC peering using static mode for PfR target discovery at a branch office that is acting as a spoke router. In this example, the IP address of the PfR master controller hub device at a head office (headend) of the network is configured as a loopback interface to allow MC peering. This task assumes a multihop type of network where the network cloud between the hub site and the branch offices is not under the control of the customer.


    Note


    PfR does not support spoke-to-spoke tunneling. Disable spoke-to-spoke dynamic tunnels by configuring the ip nhrp server-only command under interface configuration mode as part of the Next Hop Resolution Protocol (NHRP) configuration.


    Before You Begin

    PfR master controller (MC) peering must be configured on a device with routing capability located at the hub site (headend) of the network.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    pfr master

      4.    mc-peer [peer-address loopback interface-number] [description text] [domain domain-id]

      5.    target-discovery

      6.    end


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Device> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2configure terminal


      Example:
      Device# configure terminal
       

      Enters global configuration mode.

       
      Step 3 pfr master


      Example:
      Device(config)# pfr master
       

      Enters PfR master controller configuration mode to configure a Cisco device as a master controller.

       
      Step 4 mc-peer [peer-address loopback interface-number] [description text] [domain domain-id]


      Example:
      Device(config-pfr-mc)# mc-peer 10.11.11.1 loopback1
                
       

      In this example, the IP address of the PfR master controller hub device at a head office (headend) of the network is configured as the peer address.

       
      Step 5target-discovery


      Example:
      Device(config-pfr-mc)# target-discovery 
       

      Configures dynamic PfR target discovery.

       
      Step 6 end


      Example:
      Device(config-pfr-mc)# end
       

      (Optional) Exits PfR master controller configuration mode and returns to privileged EXEC mode.

       

      Enabling Bandwidth Resolution

      This task is performed on all PfR master controllers in every hub and spoke in the participating site.

      Before You Begin

      Note


      PfR target discovery must be configured before enabling bandwidth resolution. Both dynamic and static target discovery is supported by PfR bandwidth resolution. PfR bandwidth resolution is not supported with PfR active mode because there is no throughput data for traffic-classes.



      Note


      PfR does not support spoke-to-spoke tunneling. Disable spoke-to-spoke dynamic tunnels by configuring the ip nhrp server-only command under interface configuration mode as part of the Next Hop Resolution Protocol (NHRP) configuration.


      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    pfr master

        4.    bandwidth-resolution


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Device> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2 configure terminal


        Example:
        Device# configure terminal
         

        Enters global configuration mode.

         
        Step 3 pfr master


        Example:
        Device(config)# pfr master 
         

        Enters PfR master controller configuration mode to configure a router as a master controller and to configure global operations and policies.

         
        Step 4 bandwidth-resolution


        Example:
        Device(config-pfr-mc)# bandwidth-resolution
                  
         

        Enables bandwidth resolution.

         

        Overwriting Dynamically Discovered Receive and Transmit Bandwidth Limits

        Perform this task at a PfR master controller to manually specify the maximum receive (Rx) and transmit (Tx) limits for a PfR external interface. When bandwidth-resolution is enabled, receive and transmit bandwidth limits are dynamically discovered and propagated using PfR target discovery. Use this task to overwrite the dynamically discovered limits using PfR bandwidth resolution.

        After an external interface has been configured for a border router, PfR automatically monitors the utilization of external links on a border router every 20 seconds. The utilization is reported back to the master controller and, if the utilization exceeds the specified limit, PfR selects another exit link for traffic classes on that link. Only absolute values, in kilobits per second (kbps), can be specified to overwrite the dynamically discovered bandwidth limits.

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    pfr master

          4.    border ip-address [key-chain key-chain-name]

          5.    interface type number external

          6.    maximum utilization receive absolute kbps

          7.    max-xmit-utilization absolute kbps

          8.    end


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Device> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.
           
          Step 2 configure terminal


          Example:
          Device# configure terminal
           

          Enters global configuration mode.

           
          Step 3 pfr master


          Example:
          Device(config)# pfr master 
           

          Enters PfR master controller configuration mode to configure a router as a master controller and to configure global operations and policies.

           
          Step 4 border ip-address [key-chain key-chain-name]


          Example:
          Device(config-pfr-mc)# border 10.1.1.2
           

          Enters PfR-managed border router configuration mode to establish communication with a border router.

          • An IP address is configured to identify the border router.
          • At least one border router must be specified to create a PfR-managed network. A maximum of ten border routers can be controlled by a single master controller.
          Note   

          The key-chain keyword and key-chain-name argument must be entered when a border router is initially configured. However, this keyword is optional when reconfiguring an existing border router.

           
          Step 5 interface type number external


          Example:
          Device(config-pfr-mc-br)# interface GigabitEthernet 0/0/0 external
           

          Configures a border router interface as a PfR-managed external interface and enters PfR border exit interface configuration mode.

          • External interfaces are used to forward traffic and for active monitoring.
          • A minimum of two external border router interfaces are required in a PfR-managed network. At least one external interface must be configured on each border router. A maximum of 20 external interfaces can be controlled by single master controller.
          Note   

          Entering the interface (PfR) command without the external or internal keyword places the router in global configuration mode and not PfR border exit configuration mode. The no form of this command should be applied carefully so that active interfaces are not removed from the router configuration.

           
          Step 6 maximum utilization receive absolute kbps


          Example:
          Device(config-pfr-mc-br-if)# maximum utilization receive absolute 500000
           

          Sets the maximum utilization threshold of incoming traffic that can be transmitted over a PfR-managed entrance link interface.

          • Use the absolute keyword and kbps argument to specify the absolute maximum utilization on a PfR managed entrance link in kbps.
           
          Step 7 max-xmit-utilization absolute kbps


          Example:
          Device(config-pfr-mc-br-if)# max-xmit-utilization absolute 500000
           

          Configures the maximum utilization on a single PfR managed exit link.

          • Use the absolute keyword and kbps argument to specify the absolute maximum utilization on a PfR managed exit link in kbps.
           
          Step 8 end


          Example:
          Device(config-pfr-mc-br-if)# end
           

          Exits PfR border exit interface configuration mode and returns to privileged EXEC mode.

           

          Configuration Examples for PfR Bandwidth Visibility

          Example: Configuring PfR Bandwidth Resolution


          Note


          PfR target discovery must be configured before bandwidth resolution is enabled. Both dynamic and static target discovery is supported by PfR bandwidth resolution.


          The following configuration can be used in multihop networks where the network cloud between the head office and branch offices or remote sites is not controlled by the customer or is not SAF-enabled. Configuration examples are shown for three master controllers, one at the head office and two at branch offices. PfR bandwidth resolution is enabled on all PfR master controller (MC) devices. Output for the show pfr master bandwidth-resolution command is shown for all three sites.


          Note


          In the following examples, the hub and spoke device hostnames were configured as “Router-hub,” “Router-spoke1,” or “Router-spoke2,” but the device can be any device with routing capability that supports PfR.


          Hub MC Bandwidth Resolution Configuration

          The hub device has routing capability and is in the head office. In this example, PfR bandwidth resolution is enabled on the master controller.

          Router-hub> enable
          Router-hub# configure terminal
          Enter configuration commands, one per line.  End with CNTL/Z.
          Router-hub(config)# pfr master
          Router-hub(config-pfr-mc)# bandwidth-resolution
          Router-hub(config-pfr-mc)# end

          Spoke1 MC Bandwidth Resolution Configuration

          The spoke1 device has routing capability and is in a branch (spoke) office. In this example, PfR bandwidth resolution is enabled on the master controller at the branch office.

          Router-spoke1> enable
          Router-spoke1# configure terminal
          Enter configuration commands, one per line.  End with CNTL/Z.
          Router-spoke1(config)# pfr master
          Router-spoke1(config-pfr-mc)# bandwidth-resolution
          Router-spoke1(config-pfr-mc)# end

          Spoke2 MC Bandwidth Resolution Configuration

          The spoke2 device has routing capability and is in a second branch (spoke) office. In this example, PfR bandwidth resolution is enabled on the master controller at the second branch office.

          Router-spoke2> enable
          Router-spoke2# configure terminal
          Enter configuration commands, one per line.  End with CNTL/Z.
          Router-spoke2(config)# pfr master
          Router-spoke2(config-pfr-mc)# bandwidth-resolution
          Router-spoke2(config-pfr-mc)# end

          Example Output for PfR Bandwidth Resolution

          The following output is from the master controller for the hub device after PfR bandwidth resolution is enabled:

          Router-hub# show pfr master bandwidth-resolution all
          
          Border Router: 10.20.20.2           External Interface: Tu10                
          MC-peer address  Overlay address   Rx BW [kbps]   Tx BW [kbps]  Tx Load [kbps]      
          172.17.51.1      10.110.110.2      1000           900           0                   
          172.20.61.1      10.110.110.3      1000           900           35                  
          
          Border Router: 10.20.20.3           External Interface: Tu20                
          MC-peer address  Overlay address   Rx BW [kbps]   Tx BW [kbps]  Tx Load [kbps]      
          172.17.51.1      10.90.90.2        1000           900           18                  
          172.20.61.1      10.90.90.3        803            903

          The following output is from the master controller for the hub device after PfR bandwidth resolution is enabled and displays the output for the master controller peer at IP address 172.20.61.1:

          Router-hub# show pfr master bandwidth-resolution 172.20.61.1
          
          PfR Bandwidth Resolution Database
          MC-peer: 172.20.61.1          
          Border Router  External Interface  Overlay Address  Rx BW [kbps] Tx BW [kbps] Tx Load [kbps]      
          10.20.20.2     Tu10                10.110.110.3     1000         900          35                  
          10.20.20.3     Tu20                10.90.90.3       803          903          0

          Additional References

          Related Documents

          Related Topic

          Document Title

          Cisco IOS commands

          Cisco IOS Master Command List, All Releases

          Cisco IOS PfR commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples

          Cisco IOS Performance Routing Command Reference

          Basic PfR configuration for Cisco IOS XE releases

          “Configuring Basic Performance Routing” module

          Information about configuration for the border router only functionality for Cisco IOS XE Releases 3.1 and 3.2

          “Performance Routing Border Router Only Functionality” module

          Concepts required to understand the Performance Routing operational phases for Cisco IOS XE releases

          “Understanding Performance Routing” module

          Advanced PfR configuration for Cisco IOS XE releases

          “Configuring Advanced Performance Routing” module

          IP SLAs overview

          “Cisco IOS IP SLAs Overview” module

          PfR home page with links to PfR-related content on our DocWiki collaborative environment

          PfR:Home

          MIBs

          MIB

          MIBs Link

          • CISCO-PFR-MIB
          • CISCO-PFR-TRAPS-MIB

          To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

          http:/​/​www.cisco.com/​go/​mibs

          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 PfR Bandwidth Visibility

          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 PfR Bandwidth Visibility

          Feature Name

          Releases

          Feature Information

          PfR Bandwidth Visibility Distribution for xDSL Access

          15.3(1)T

          Cisco IOS XE Release 3.8S

          PfR bandwidth visibility is a PfR enhancement that provides accurate maximum bandwidth information to peering PfR elements so that policies can be applied automatically.

          The following commands were introduced or modified: bandwidth-resolution, debug pfr border bandwidth-resolution, debug pfr master bandwidth-resolution, show pfr master bandwidth-resolution.