One document matched: draft-ietf-radius-acct-interim-00.txt
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
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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
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(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.
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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.
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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.
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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.
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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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