RADIUS Working Group Pat R. Calhoun INTERNET DRAFT 3Com Corporation Category: Internet Draft Mark A. Beadles Title: draft-ietf-radius-acct-interim-00.txt CompuServe, Inc. Date: July 1997 Alex Ratcliffe UUNET Technologies, Inc. RADIUS Accounting Interim Accounting Record Extension Status of this Memo This document is an Internet-Draft. Internet-Drafts are working doc- uments of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute work- ing documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months. Internet-Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet- Drafts as reference material or to cite them other than as a ``work- ing draft'' or ``work in progress.'' To learn the current status of any Internet-Draft, please check the 1id-abstracts.txt listing contained in the Internet-Drafts Shadow Directories on ds.internic.net, nic.nordu.net, ftp.nisc.sri.com, or munnari.oz.au. Abstract The RADIUS Accounting document [1] defines a mechanism which is used by a Network Access Server (NAS) to send accounting information to a RADIUS server. The current protocol defines a Start and Stop record. This document defines an interim record which is used to make the RADIUS accounting protocol more robust. 1.0 Introduction The current protocol defines a message which a NAS sends to the RADIUS server when a session begins, and a message when the session ends. All information which is necessary for the billing process Calhoun, Beadles, Ratcliffe expires Janurary 1998 [Page 1]
INTERNET DRAFT July 1997 (i.e. session time, number of bytes transfered, etc) are only available in the Accounting Stop message. Therefore if a NAS becomes unavailable for some time (i.e. power failure, reboot, network problem, etc...) it becomes impossible for a service provider to bill for sessions initiated on the NAS (this is especially important with long lived sessions). This document introduces a new accounting message which is sent from NAS to the RADIUS server which is called the interim accounting message. This message is sent in order to periodically update the RADIUS server with information pertaining to a specific session. 1.1. Specification of Requirements In this document, several words are used to signify the requirements of the specification. These words are often capitalized. MUST This word, or the adjective "required", means that the definition is an absolute requirement of the specification. MUST NOT This phrase means that the definition is an absolute prohibition of the specification. SHOULD This word, or the adjective "recommended", means that there may exist valid reasons in particular circumstances to ignore this item, but the full implications must be understood and carefully weighed before choosing a different course. MAY This word, or the adjective "optional", means that this item is one of an allowed set of alternatives. An implementation which does not include this option MUST be prepared to interoperate with another implementation which does include the option. 2. Operation When a session is initiated, a NAS issues a RADIUS Start Accounting Request. The RADIUS Server processes the request and issues a response. However, if the RADIUS Server wishes to receive interim accounting information it needs to add a new RADIUS Attribute defined below which indicates the interval in seconds between interim messages. Calhoun, Beadles, Ratcliffe expires Janurary 1998 [Page 2]
INTERNET DRAFT July 1997 This scheme does not break backward interoperability since a RADIUS server not supporting this extension will simply not add the new Attribute. On the other hand, NAS' not supporting this extension will simply ignore the Attribute. This means that if a RADIUS Server uses the interim extension for other purposes (i.e. resource management) it MUST be aware of NAS' which do not support this extension. Note that all information in an interim message is cumulative (i.e. number of packets sent is the total since the beginning of the session, not since the last interim message). It is envisioned that an Interim Accounting record would contain all of the attributes normally found in an Accounting Stop message with the exception of the Acct-Term-Cause attribute. Since accounting packets are modified when retransmissions occur, it is recommended that the interval time restart only once the response from the RADIUS Server has been received (making sure that interim updates are not sent while retransmissions are pendig for a given session). A NAS COULD divide the interval time with the maximum number of retranmissions configured locally in order to determine the retransmission mechanism. Although this extension allows control from a central RADIUS Server, the authors wish to caution against using low interval values (i.e. 5 seconds). In a NAS with large port densities, it can becomes a CPU intensive task as well as a waste of network bandwidth. 3. Attributes This section defines the new RADIUS Attributes necessary to support the Interim Accounting extension. 3.1. Acct-Status-Type Description This attribute indicates whether this Accounting-Request marks the beginning of the user service (Start) or the end (Stop). It MAY be used by the client to mark the start of accounting (for example, upon booting) by specifying Accounting-On and to mark the end of accounting (for example, just before a scheduled reboot) by specifying Accounting-Off. Calhoun, Beadles, Ratcliffe expires Janurary 1998 [Page 3]
INTERNET DRAFT July 1997 Additionally this attribute MAY indicate an interim update. A summary of the Acct-Status-Type attribute format is shown below. The fields are transmitted from left to right. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Value +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Value (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 40 for Acct-Status-Type. Length 6 Value The Value field is four octets. 1 Start 2 Stop 3 Interim Update 7 Accounting-On 8 Accounting-Off 3.2. Acct-Interim-Interval Description This attribute indicates the number of seconds between each interim update in seconds for this specific session. A summary of the Acct-Interim-Interval attribute format is shown below. The fields are transmitted from left to right. Calhoun, Beadles, Ratcliffe expires Janurary 1998 [Page 4]
INTERNET DRAFT July 1997 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Value +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Value (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type ?? for Acct-Interim-Interval. Length 6 Value The Value field contains the number of seconds between each interim update to be sent from the NAS for this session. The value MUST NOT be smaller than 5. Calhoun, Beadles, Ratcliffe expires Janurary 1998 [Page 5]
INTERNET DRAFT July 1997 4.0 Contacts Pat R. Calhoun 3Com Corporation 1800 Central Ave. Mount Prospect, Il, 60056 pcalhoun@usr.com (847) 342-6898 Mark A. Beadles, Compuserve Corporation CompuServe, Inc. 5000 Britton Rd. Hilliard, OH, 43026 mbeadles@web.compuserve.com (614) 723-1941 Alex Ratcliffe, UUNET Technologies, Inc, 3060 Williams Drive, Fairfax, VA, 22032. alexr@uu.net. (703) 206 5698. 5.0 References [1] Rigney, C., "RADIUS Accounting", RFC 2139, April 1997. [2] Rigney, C., Rubens, A., Simpson, W., and Willens, S., "Remote Authentication Dial In User Service (RADIUS)", RFC 2138, April 1997. Calhoun, Beadles, Ratcliffe expires Janurary 1998 [Page 6]
