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System Administration Guide: IP Services

ProcedureHow to Configure Flow Control in the IPQoS Configuration File

To control the rate at which a particular traffic flow is released onto the network, you must define parameters for the meter. You can use either of the two meter modules, tokenmt or tswtclmt, in the IPQoS configuration file.

The next procedure continues to build the IPQoS configuration file for the application server in Example 34–3. In the procedure, you configure not only the meter but also two marker actions that are called within the meter action statement.

Before You Begin

The steps assume that you have already defined a class and a filter for the application to be flow-controlled.

  1. Open the IPQoS configuration file that you have created for the applications server.

    In the /var/ipqos/BigAPPS.qos file, you begin after the following marker action:


    action {
    module dscpmk
    name markAF21
    params {
        global_stats FALSE
        dscp_map{0-63:18}
        next_action continue
    }
}

  2. Create a meter action statement to flow-control traffic of the ftp class.


    action {
    module tokenmt
    name meterftp
    module tokenmt

    Invokes thetokenmt meter.

    name meterftp

    Gives the name meterftp to the action statement.

  3. Add parameters to configure the meter's rate.


    params {
       committed_rate 50000000
       committed_burst 50000000
    committed_rate 50000000

    Assigns a transmission rate of 50,000,000 bps to traffic of the ftp class.

    committed_burst 50000000

    Commits a burst size of 50,000,000 bits to traffic of the ftp class.

    For an explanation of tokenmt parameters, refer to Configuring tokenmt as a Two-Rate Meter.

  4. Add parameters to configure traffic conformance precedences:


        red_action markAF31
    green_action_name markAF22
    global_stats TRUE
    }
}
    red_action_name markAF31

    Indicates that when the traffic flow of the ftp class exceeds the committed rate, packets are sent to the markAF31 marker action statement.

    green_action_name markAF22

    Indicates that when traffic flows of class ftp conform to the committed rate, packets are sent to the markAF22 action statement.

    global_stats TRUE

    Enables metering statistics for the ftp class.

    For more information about traffic conformance, see Meter Module.

  5. Add a marker action statement to assign a per-hop behavior to nonconformant traffic flows of class ftp.


    action {
    module dscpmk
    name markAF31
    params {
        global_stats TRUE
        dscp_map{0-63:26}
        next_action continue
    }
}
    module dscpmk

    Invokes the marker module dscpmk.

    name markAF31

    Gives the name markAF31 to the action statement.

    global_stats TRUE

    Enables statistics for the ftp class.

    dscp_map{0–63:26}

    Assigns a DSCP of 26 to the packet headers of the traffic class ftp whenever this traffic exceeds the committed rate.

    next_action continue

    Indicates that no further processing is required on packets of the traffic class ftp. Then these packets can return to the network stream.

    The DSCP of 26 instructs the marker to set all entries in the dscp map to the decimal value 26 (binary 011010). The DSCP of 26 sets the AF31 per-hop behavior. The marker marks packets of the ftp traffic class with the DSCP of 26 in the DS field.

    AF31 assures that all packets with a DSCP of 26 receive a low-drop precedence, but with only Class 3 priority. Therefore, the possibility of nonconformant FTP traffic being dropped is low. For a table of possible AF codepoints, refer to Table 37–2.

  6. Add a marker action statement to assign a per-hop behavior to ftp traffic flows that conform to the committed rate.


    action {
    module dscpmk
    name markAF22
    params {
        global_stats TRUE
        dscp_map{0-63:20}
        next_action continue
    }
}
    name markAF22

    Gives the name markAF22 to the marker action.

    dscp_map{0–63:20}

    Assigns a DSCP of 20 to the packet headers of the traffic class ftp whenever ftp traffic conforms to its configured rate.

    The DSCP of 20 tells the marker to set all entries in the dscp map to the decimal value 20 (binary 010100). The DSCP of 20 sets the AF22 per-hop behavior. The marker marks packets of the ftp traffic class with the DSCP of 20 in the DS field.

    AF22 assures that all packets with a DSCP of 20 receive a medium-drop precedence with Class 2 priority. Therefore, conformant FTP traffic is assured a medium-drop precedence among flows that are simultaneously released by the IPQoS system. However, the router gives a higher forwarding priority to traffic classes with a Class 1 medium-drop precedence mark or higher. For a table of possible AF codepoints, refer to Table 37–2.

  7. Add the DSCPs that you have created for the application server to the appropriate files on the Diffserv router.

See Also