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System Administration Guide: IP Services

ProcedureHow to Configure Forwarding for Application Traffic in the IPQoS Configuration File

The next procedure shows how to configure forwarding for application traffic. In the procedure, you define per-hop behaviors for application traffic classes that might have lower precedence than other traffic on a network. The steps continue building the /var/ipqos/BigAPPS.qos file in Example 34–3.

Before You Begin

The procedure assumes that you have an existing IPQoS configuration file with already-defined classes and already-defined filters for the applications to be marked.

  1. Open the IPQoS configuration file that you have created for the application server, and locate the end of the last filter clause.

    In the /var/ipqos/BigAPPS.qos file, the last filter is the following:


     filter {
        name ftpdata
        sport ftp-data
        class ftp
    }
}

  2. Invoke the marker as follows:


    action {
    module dscpmk
    name markAF13
    module dscpmk

    Invokes the marker module dscpmk.

    name markAF13

    Gives the name markAF13 to the action statement.

  3. Define the per-hop behavior to be marked on electronic mail traffic flows.


        params {
        global_stats FALSE
        dscp_map{0-63:14}
        next_action continue
    }
}
    global_stats FALSE

    Enables statistics collection for the markAF13 marker action statement. However, because the value of enable_stats is FALSE, statistics are not collected.

    dscp_map{0–63:14}

    Assigns a DSCP of 14 to the packet headers of the traffic class smtp, which is currently being processed by the marker.


    next_action continue

    Indicates that no further processing is required on packets of the traffic class smtp. These packets can then return to the network stream.

    The DSCP of 14 tells the marker to set all entries in the dscp map to the decimal value 14 (binary 001110). The DSCP of 14 sets the AF13 per-hop behavior. The marker marks packets of the smtp traffic class with the DSCP of 14 in the DS field.

    AF13 assigns all packets with a DSCP of 14 to a high-drop precedence. However, because AF13 also assures a Class 1 priority, the router still guarantees outgoing email traffic a high priority in its queue. For a table of possible AF codepoints, refer to Table 37–2.

  4. Add a marker action statement to define a per-hop behavior for network news traffic:


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

    Gives the name markAF21 to the action statement.

    dscp_map{0–63:18}

    Assigns a DSCP of 18 to the packet headers of the traffic class nntp, which is currently being processed by the marker.

    The DSCP of 18 tells the marker to set all entries in the dscp map to the decimal value 18 (binary 010010). The DSCP of 18 sets the AF21 per-hop behavior. The marker marks packets of the news traffic class with the DSCP of 18 in the DS field.

    AF21 assures that all packets with a DSCP of 18 receive a low-drop precedence, but with only Class 2 priority. Thus, the possibility of network news traffic being dropped is low.

See Also