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    PPPoE Service Name Tables Overview

    PPPoE clients use service name tags, as defined in RFC 2516, to request that an AC support certain services. The client includes a custom service name tag in the PADI packet that it broadcasts to remote ACs. Alternatively, the client can include an empty service name tag of zero length to indicate that any service is acceptable, or an unknown service name tag to represent a service not yet configured in the PPPoE service name table.

    On receipt of a PADI packet that it can serve, the AC responds with a PADO packet. The PADO packet contains a service name tag that is identical to the one in the PADI, as well as one or more additional service name tags indicating other services that the AC offers.

    A PPPoE service name table consists of one or more service name entries and their associated action. The PPPoE service name table can include three types of service name tags:

    • Custom service name tag (serviceName) — A service entry that represents a specific client service that an AC can support. The length of the custom service name tag can be up to 31 alphanumeric characters; for example, myQoSClass or my ISPService. You can optionally associate an action (drop or terminate) with a custom service. The default action for a custom service is terminate.
    • Empty service name tag (empty-service-name) — A service entry of zero length that is used to represent any service. The router either responds with a PADO packet to all PADI requests containing an empty service name tag, or denies (drops) all PADI requests based on the action configured for the service.
    • Unknown service name tag (unknown-service-name) — A service entry that has not been configured in the PPPoE service name table. When a PPPoE client includes an unknown service name tag in the PPPoE service name table, the router responds based on the action (drop or terminate) associated with the unknown service name entry.

      The default action associated with the unknown service name tag depends on the PPPoE service name table configuration. If all the services in the table are configured to drop, the default action for the unknown service name tag is terminate. If all the services in the table are configured to terminate, the default action for the unknown service name tag is drop. If both terminate and drop are configured for services in the table, all unknown service name tags are dropped by default.

    Features

    PPPoE service name tables enable an AC, such as an E Series router, to support multiple service name tags in addition to the empty service name tag and the unknown service name tag. You can configure up to 16 PPPoE service name tables per E Series router to:

    • Define the set of service name tags (empty service name, custom service name, and unknown service name) that the router advertises in the PADO packets sent to PPPoE clients.
    • Control whether the router responds to (terminate) or denies (drop) PADI requests based on the action associated with the service name tags.

    Table Structure

    Each entry, or row, in a PPPoE service name table consists of the following components:

    • Service name tag—Service name tags specify the client services that an AC supports. You can add three types of service name tags to the PPPoE service name table: empty service name, custom service name (serviceName), and unknown service name. Every PPPoE service name table includes one empty service name tag and one unknown service name service tag. An empty service name tag is a service tag of zero length that is used to represent any service. An unknown service name service tag is used to represent a service tag that has not been configured in the service name table. In addition to these two tags, you can configure up to 16 custom service name tags per table.
    • Action—Each service name tag has an associated action: terminate (the default action) or drop. For empty service name and unknown service name entries, you can use the action keyword with the service command to modify the default action associated with the service. For custom service name (serviceName) entries, using the action keyword with the service command is optional. The default action for a custom service tag entry is terminate.

    For example, Table 1 shows a PPPoE service name table containing five entries: three custom service name tags, two associated with the terminate action and one associated with the drop action; an empty service name tag (“ ”) associated with the drop action; and an unknown service name tag associated with the drop action.

    Table 1: Sample PPPoE Service Name Table

    Service Name

    Action

    “myISPService”

    Terminate

    “myQOSClass1”

    Terminate

    “myQOSClass2”

    Drop

    “  ” (empty-service-name)

    Drop

    unknown-service-name

    Drop

    Note: You can associate the drop action with a maximum of eight service tags in a PPPoE service name table.

    Enabling the Service Name Table for Use

    After you create a PPPoE service name table and populate it with entries, you must enable it for use with a static or dynamic PPPoE interface. To enable a PPPoE service name table for use with a static interface, you assign the table to the PPPoE major interface. To enable a PPPoE service name table for use with a dynamic interface, you add the table to a profile that is dynamically assigned to a PPPoE interface column.

    Published: 2014-08-14