One document matched: draft-ietf-radius-acct-interim-01.txt
Differences from draft-ietf-radius-acct-interim-00.txt
RADIUS Working Group Pat Calhoun
INTERNET DRAFT 3Com Corporation
Category: Internet Draft Mark Beadles
Title: draft-ietf-radius-acct-interim-01.txt Compuserve Corporation
Date: January 1998 Alex Ratcliff
RADIUS Accounting
Interim Accounting Record Extension
<draft-ietf-radius-acct-interim-01.txt>
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-
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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 (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
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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.
2.0 Operation
When a user is authenticated, a RADIUS server issues an Access-Accept
in response to a successful Access-Request. If the server wishes to
receive interim accounting messages for the given user it must include
the Acct-Interim-Interval RADIUS attribute in the message, which
indicates the interval in seconds between interim messages.
It is also possible to statically configure an interim value on the
NAS itself. Note that a locally configured value on the NAS overrides
a value found in an Access-Accept.
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
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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 all the information is cumulative, a NAS MUST ensure that only a
single generation of an interim Accounting message for a given session
is present in the retransmission queue at any given time. This means
that the NAS MUST first delete any pending interim messages for the
given session (whose information is now obsolete) from the
retransmissions before issuing a new interim message. Note that this
event would only occur if the RADIUS accounting server was not
reachable.
A NAS MAY use a fudge factor to add a random delay between Interim
Accounting messages for separate sessions. This will ensure that a
cycle where all messages are sent at once is prevented (this could
occur if a primary link was recently restored and many dial-up users
were directed to the same NAS at once).
Although this extension allows control from a central RADIUS Server,
the authors wish to strongly caution against using low interval values
(i.e. less than 60 seconds). In a NAS with large port densities, it
can become a CPU intensive task as well as a waste of network
bandwidth.
3.0 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.
Additionally this attribute MAY indicate an interim update.
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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 and can have one of the following
values:
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. This value can only
appear in the Access-Accept RADIUS message.
A summary of the Acct-Interim-Interval 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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Type
85 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 60 and SHOULD NOT be less than 600.
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.
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