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    Sending the Acct-Start and Acct-Update Messages After NCP Negotiation Is Completed Overview

    When authentication, authorization, and accounting (AAA) receives authentication-grant permission from the RADIUS server, an Acct-Start message is sent immediately from the Broadband Remote Access Server (B-RAS) to the RADIUS server. An Acct-Update message is sent from the B-RAS to the RADIUS server immediately after IP notifies AAA to set a user IP address or user interface ID.

    However, you can use the aaa accounting delay-start command to delay the sending of the Acct-Start message from the B-RAS to the RADIUS server until Network Control Protocol (NCP) negotiation is completed. When NCP negotiation is completed, IP notifies AAA to set a user IP address or user interface ID (in case of Point-to-Point Protocol version 6 [PPPv6] subscribers). Only then does the B-RAS send the Acct-Start message to the RADIUS server. This ensures that Framed-Interface-Id [96] or Framed-IP-Address [8] RADIUS attributes that are negotiated during Internet Protocol Control Protocol (IPCP) or Internet Protocol version 6 Control Protocol (IPv6CP) are present in the Acct-Start message, thereby reducing the number of accounting messages from two to one for each subscriber.

    When delaying the sending of the Acct-Start message is enabled:

    • In a single-stack environment:
      • Acct-Start message is sent after IPCP negotiation is completed (for PPPv4 subscribers)
      • Acct-Start message is sent after IPv6CP negotiation is completed (for PPPv6 subscribers)
    • In a dual-stack environment:
      • Acct-Start message is sent after IPCP or IPv6CP negotiation is completed, whichever occurs first (for PPPv4 and PPPv6 subscribers)

    You can use the aaa accounting immediate-update-framed-ipv6-interfaceId-negotiation command to send the Acct-Update message with the Framed-Interface-Id [96] RADIUS attributes from the B-RAS to the RADIUS server for PPPv6 users immediately after NCP negotiation is completed.

    When the immediate sending of the Framed-Interface-Id [96] RADIUS attributes in the Acct-Update message is enabled:

    • In a single-stack environment:
      • Acct-Update message is sent after IPv6CP negotiation is completed (for PPPv6 subscribers)
    • In a dual-stack environment:
      • Acct-Update message is sent after both IPCP and IPv6CP negotiations are completed (for PPPv4 and PPPv6 subscribers)

    Published: 2014-08-13