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    Configuring Calculation of Service Session Accounting Based on Scheduler Profiles Instead of Rate-Limit Profiles in Hierarchical Parent Groups for Forwarded Packets

    You can configure the Service Manager application to compute accounting for service sessions based on the number of packets that are forwarded by the scheduler profile in QoS profiles on output interfaces. Service Manager collects statistics from parent groups that are configured in an output policy attached to an interface. Each parent group might contain a rate-limit profile. When packets enter an interface to which a rate-limit profile is applied, the router counts the number of bytes (packets) over time, categorizes each packet as committed, conformed, or exceeded, and assigns a transmit, drop, or mark action to the packets.

    Parent groups configured in a hierarchy are effectively used in a layer 2 (ATM) access network for digital subscriber lines (DSLs) where many routing gateways lead to one Broadband Remote Access Server (B-RAS). The B-RAS uses rate-limit hierarchies to allocate shareable bandwidth to each routing gateway, which enables unused bandwidth from one routing gateway to be used by others.

    Each rate-limit profile in a hierarchical parent group processes and classifies the packets that arrive at an interface, and computes the statistics to be displayed in the output of the show commands for the relevant interfaces. For rate-limit profiles in a hierarchical parent group that are part of classifier groups in a policy attached to an output interface, if you configure a scheduler profile in a QoS profile and attach it to the same output interface, the packets processed by the rate-limit profile in the hierarchical parent group might be either forwarded or dropped based on the scheduler profile attached to the interface. A scheduler profile configures the bandwidth at which a traffic queue is validated as a function of relative weight, assured rate, and shaping rate.

    This method of operation causes discrepancies and inaccuracies in the accounting statistics for subscriber service sessions that the Service Manager application collects. Because packets that are treated as forwarded packets at the rate-limit profile in a hierarchical parent group might be classified in a different way at some other level in a rate-limit hierarchy, incorrect accounting statistics are retrieved for service sessions.

    In an environment in which you apply policies, with rate-limit profiles defined in a hierarchical parent group, to interfaces that are also assigned with scheduler profiles, you can enable Service Manager to calculate accounting information for subscriber sessions based on the packets forwarded by scheduler profiles. You can use the service-accounting-statistics scheduler-based command in Global Configuration mode to enable this capability to compute accounting details based on scheduler profiles for policies with hierarchical rate-limit profiles on output interfaces. By default, this feature is not enabled. This functionality is effective only for packets that are forwarded at an output interface by a policy that contains a rate-limit profile in a hierarchical parent group and does not apply to packets that are dropped by the rate-limit profile.

    When you enable or disable this feature, the statistical values collected for policies that contain rate-limit profiles in hierarchical parent groups on output interfaces are reset. This setting to calculate accounting details for service sessions based on scheduler profiles is preserved across an upgrade operation.

    When you enable this functionality, the following operations are performed:

    • The packet received at an output interface is processed by the rate-limit profile defined in a hierarchical parent group after classification. If the packet is marked to be transmitted based on the action specified in the rate-limit profile, the statistical counter to save the number of forwarded packets in the parent group is not incremented. When the packet arrives at the scheduler profile and is processed by it, if it is scheduled to be forwarded, the counter to store the number of forwarded packets for each rate-limit profile is incremented.
    • If the incoming packet is determined to be dropped by the rate-limit profile in the parent group against which it is validated, the counter to record the number of dropped packets of the parent group is incremented.

    If you enable scheduler profile–based computation of service session accounting, for IPv4, IPv6, or MPLS interfaces, the output of the show ip interface , show ipv6 interface, or show mpls interface commands display the forwarded packets and bytes fields, and dropped packets and bytes fields in the rate-limit-profile section under the IP, IPv6, or MPLS policy output headings for policies with hierarchical parent groups. The committed, conformed, exceeded, saturated, and unconditional packets and bytes fields are not displayed in the rate-limit-profile section in the output of these commands for policies with hierarchical parent groups.

    To enable computation of accounting statistics for service sessions based on scheduler profiles for forwarded packets with rate-limit profiles in hierarchical parent groups on output interfaces:

    • From Global Configuration mode, enable the capability to calculate accounting statistics for subscriber service sessions by using scheduler profiles instead of rate-limit profiles in hierarchical parent groups:
      host1(config)#service-accounting-statistics scheduler-based

      Use the no version of this command to disable the computation of accounting details based on scheduler profiles. In such a case, the accounting information is computed based on rate-limit profiles defined in hierarchical parent groups for policies on output interfaces.

    Published: 2014-08-20