[Serusers] Fwd: Re: AW: AW: [Sipping] FYI: RADIUS & SIP

[Greg Fausak]

Jiri,

Our implementation does not use RADIUS.  I am a long time
RADIUS user for my ISP.  It did not seem to be a good fit for us.

I will explain (skipping many of the details)...

We use a feedback loop.  We set the group flag for the customer,
For example "local", "cont_us", "sip".  We check to see if the customer
is in one of these groups before routing the call.  If the customer
attempts a "cont_us" (continental USA) call, and they do not belong
to the "cont_us" group, we simply redirect the SIP connection to a
recording
that tells them their account needs attention.

By default, the customer does NOT belong to ANY groups.  Our
backend processing constantly evaluates group membership, and if
It is deemed appropriate, the customer is placed in or removed from
groups.

The grp table is updated (via serctl now) at these times :

1) Just after they complete a call.
2) At the end of the month.
3) During an audit.

I know that many use RADIUS, and it seems to work for them.  It seemed
like an added complexity that wasn't necessary for us.

So what this means is that when a call is placed we can authenticate
quickly
by checking the group membership.  Then, after the call (when we have
more time
to think about it) we authenticate the next call.

It is our intention to relax the SER cache, and make all REGISTRATIONs
hit the database (rather than internal cache).  We will then be able to
run multiple SER servers sharing a common database.

It has been pointed out that the database is a single point of failure,
But, I can live with that.  We will use replication and keep a hot
standby
For the inevitable database failure (although, I have been running some
applications
for over a year without a database failure).

---greg

> -----Original Message-----
> From: serusers-bounces at lists.iptel.org 
> [mailto:serusers-bounces at lists.iptel.org] On Behalf Of Jiri Kuthan
> Sent: Thursday, August 07, 2003 12:48 PM
> To: serusers at lists.iptel.org
> Subject: [Serusers] Fwd: Re: AW: AW: [Sipping] FYI: RADIUS & SIP
> 
> 
> Dear SER users,
> 
> I would like to collect feedback on use of RADIUS with SIP.
> 
> There is a concern in the IETF that RADIUS is not good enough
> for accounting due to its lack of reliability. On the other hand,
> use of RADIUS for us has been one of the most frequently asked
> SER features.
> 
> Can people with hands on real deployments share their experience
> with me? I'm interested in aspects like how the missing reliability
> has been stressing your operation, how much they are interested
> in fixing it, and what kind of fixes they would welcoyme (transition
> to Diameter? adding fail-over capabilities?)
> 
> -Jiri
> 
> >> There is a believe in the IETF that lack of reliability in RADIUS
> >> determines this work to be dropped. (Authentication is a different
> >> story, though.)
> >
> >The point of this particular discussion is to understand whether
> >specification of RADIUS transport behavior might be helpful in that
> >regard, or whether we've have to go further (such as 
> specifying failover
> >behavior).
> >
> >Reading RFC 2865, one of the reasons that RADIUS was not 
> made to run over
> >TCP in the first place was that it was desired that failover 
> occur in a
> >timeframe prior to connection failure.  RFC 3539 handles 
> this issue by
> >defining application-layer timers and heartbeats that allow the AAA
> >application to re-send an accounting packet over another 
> connection before
> >tearing down a suspect one.
> >
> >Via the heartbeat mechanism, the AAA client can determine whether the
> >issue is due to its immediate connection, or something downstream.
> >Failover only occurs if the immediate connection is found to 
> be suspect,
> >so failover occurs on a hop-by-hop basis.
> >
> >RFC 3539 cannot be applied to the RADIUS protocol as it 
> stands because
> >RADIUS does not support a heartbeat.  As a result, a RADIUS 
> client can
> >failover even where its immediate proxy is healthy, because 
> of a problem
> >on a downstream RADIUS server.  Since RADIUS failover is
> >typically end-to-end, there may be no failover in proxies, even if a
> >server is not responding to requests proxied to it.
> >
> >Even if one were to define appropriate RTT/RTO measurements, 
> and use traffic
> >from the proxy as a demonstration of "liveness", 
> inappropriate failover
> >can still happen in cases where the time between proxy 
> traffic is greater
> >than the failover timer.
> >
> >The end result is that to be able to apply RFC 3539, one 
> would need to add
> >a heartbeat command to RADIUS.  This is a fairly major step, since it
> >would require changing both RADIUS client and server implementations.
> >
> >So the question is:
> >
> >"If a major protocol change were to be made to RADIUS to improve
> >reliability, would such a change be deployed on RADIUS clients and
> >servers and would it be acceptable for the SIP accounting 
> specification
> >to depend on such a change?"
> >
> >If the answer is yes, then a RADIUS failover spec  might be worth
> >discussing further. If no, then it seems to me that a RADIUS 
> failover spec it might
> >not be worth doing -- it's not considered important enough 
> to get over the deployment hurdles.
> >That raises the question of whether a dependency even on transport
> >behavior improvements is possible, since even this would 
> still require
> >changes on RADIUS clients (though not servers).
> >
> >Comments?
> 
> --
> Jiri Kuthan            http://iptel.org/~jiri/ 
> 
> _______________________________________________
> Serusers mailing list
> serusers at lists.iptel.org
> http://lists.iptel.org/mailman/listinfo/serusers
>