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Date:      Fri, 20 Jul 2001 01:52:16 -0700
From:      "Ted Mittelstaedt" <tedm@toybox.placo.com>
To:        "Panagiotis Skoulikaritis" <pskoul@egreta.gr>, "FreeBSD Questions" <questions@FreeBSD.ORG>
Subject:   RE: need help configuring radius
Message-ID:  <003d01c110f9$46a368e0$1401a8c0@tedm.placo.com>
In-Reply-To: <3B57DA52.CDEE84D@egreta.gr>

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First, you don't want to ask this here, instead you want to subscribe to
the portmaster-radius mailing list at http://www.livingston.com/tech/archive/

Secondly, what your asking is not simple.  For example there's a couple
of Reply attributes out there that might work - Port-Limit and MultLink Flag,
but these are not standard.  You must check your NAS documentation to see
if it recognizes them and applies them to ISDN multilink calls.  Further
they only work if you only have a single NAS.

The usual method of doing what your wanting to do is to use a RADIUS server
such as cistron that has support for setting multiple login limits.  The
way these servers work is if you only permit a single session for a user
they will authenticate the first session then deny all other auth attempts
as long as that session is logged in.  Therein is the difficulty, however,
because RADIUS is a stateless protocol and as such there's no direct
connection
between the radius server and the NAS that the radius server can use to
synchronize a database of who is logged in and who isn't.

What some people do to track logins is to depend on the start and stop
records, they increment a counter when they get a start record and
decrement it when they get a stop record.  This works OK for small NAS
with just a few ports, there's a radius daemon at

http://yardradius.on.openave.net/

that works quite well for that.

However, for anything significant (more than 20 ports or so) you run into
synchronization problems.  Some NAS have piss-poor accounting record control,
Portmasters have been known under heavy load to not bother sending start
accounting records or sending duplicates.  Also RADIUS is UDP so you could
lose the packet anyway.  Then you get into a situation where the radius
server thinks a user is logged on when they really arent thus the next time
they call in the NAS won't let them logon.

More sophisticated servers like cistron get around this problem by issuing
an SNMP query to the NAS every time they see what they think is a simultaneous
login attempt, to check and see if the first login is really there.  This
requires some fooling around with scripts and ucd-snmp.  Also it's very
NAS dependent - if you have a collection of NAS from different manufacturer
then your going to really be hosed and some NAS (USR for example) don't
give out that data via SNMP so you have to do other scripting with Telnet
scripts.

At our site we started out with the free radius 2.01 daemon Livingston handed
out
then finally dumped it for YARD because of the simultaneous use thing.  But
I only lasted about 8 months with dealing with that because of the problems of
keeping the radius daemon in sync with a big nas with many T1's coming into
it.
I finally scrapped all that and went to ICradius
(ftp://ftp.innercite.com/pub/icradius) which is a modified cistron
that runs on a mysql server.  It also has several web-based interfaces to
it which helped greatly because we have admins that I don't trust with UNIX
command line access.  Also having all the accounting in a SQL server is
extremely
useful, beforehand we used to have to futz with all these icky perl scripts
to attempt to get reporting off the monthly detail files which were huge.  Now
we can query usage on the fly which helps with troubleshooting as well as the
customers that call up claiming they never used the service and why are we
billing them.  There's also some other tiered billing things that become
possible with SQL queries that I won't get into.  But I will warn you,
although it's a great radius server it's very complicated and not simple to
setup on FreeBSD.  It's easy to see why the commercial radius servers like
Steel Belted Radius are selling so well.

Ted Mittelstaedt                                       tedm@toybox.placo.com
Author of:                           The FreeBSD Corporate Networker's Guide
Book website:                          http://www.freebsd-corp-net-guide.com


>-----Original Message-----
>From: owner-freebsd-questions@FreeBSD.ORG
>[mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of Panagiotis
>Skoulikaritis
>Sent: Friday, July 20, 2001 12:14 AM
>To: FreeBSD Questions
>Subject: need help configuring radius
>
>
>Hello
>
>I need help with configuring my radius server.
>I would like to distinguish on how my users log in depending on their
>contract with either 64 kbps isdn or 128 kbps isdn.  So far I' m using
>the attribute NAS-Port-Type = ISDN, but this way every user that has
>this attribute can use both channels of the isdn even though they
>haven't subscribe for that.  Any help would be appreciated.
>
>Thanks
>
>Panagiotis
>
>
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