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2.2.2 Accounting Requests

Accounting-Request packets are sent from a NAS to a RADIUS server to allow for accounting of a service provided to a user.

Upon receipt of an Accounting-Request packet, the server attempts to record it (see Accounting), and if it succeeds in doing so, it replies with an Accounting-Response packet. Otherwise, it sends no reply, which then causes the NAS to retransmit its request within a preconfigured interval of time. Such retransmits will continue until either the server responds with an Accounting-Response packet or a preconfigured number of retransmits is reached, whichever occurs first.

Any attribute valid in an Access-Request or Access-Accept packet is also valid in an Accounting-Request packet, except the following attributes, which are never present in any Accounting-Request packet:

Either a NAS-IP-Address or a NAS-Identifier must be present in an Accounting-Request packet. It should contain either a NAS-Port or a NAS-Port-Type attribute (or both), unless the service does not involve a port or the NAS does not distinguish among its ports.

If the Accounting-Request packet includes a Framed-IP-Address, that attribute must contain the actual IP of the user.

There are five types of accounting packets, differentiated by the value of the Acct-Status-Type attribute. These are:

Session Start Packet

The session start packet is sent after the user has successfully passed the authentication and has started to receive the requested service. It must contain at least following attributes:

  • Acct-Status-Type = Start
  • User-Name
  • Acct-Session-Id
  • NAS-IP-Address
  • NAS-Port-Id
Session Stop Packet

The session stop packet is sent after the user has disconnected. It conveys the information about the duration of the session, number of octets transferred, etc. It must contain at least the following attributes:

  • Acct-Status-Type = Stop
  • User-Name
  • NAS-IP-Address
  • Acct-Session-Id

The last three of them are used to find the corresponding session start packet.

Keepalive Packet

The keepalive packet is sent by the NAS when it obtains some new information about the user’s session, e.g. it has determined its IP or has changed the connection speed. The packet must contain at least the following attributes:

  • Acct-Status-Type = Alive
  • User-Name
  • NAS-IP-Address
  • Acct-Session-Id
Accounting-Off Packet

By sending this packet, the NAS requests that radiusd mark all sessions registered from this particular NAS as finished. Receiving this packet usually means that the NAS is to be shut down, or is about to change its configuration in a way that requires all currently opened sessions to be closed. The packet must contain at least the following attributes:

  • Acct-Status-Type = Accounting-Off
  • NAS-IP-Address
Accounting-On Packet

By sending this packet, the NAS informs radiusd that it is ready to accept the incoming connections. Usually this packet is sent after startup, or after a major reconfiguration of the NAS. It must contain at least the following attributes:

  • Acct-Status-Type = Accounting-On
  • NAS-IP-Address

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