Ratio between Number of Radius Accouting Server and Number of Radiuis Authentication Server

Joe Shen joe_hznm at yahoo.com.sg
Fri May 4 02:23:31 UTC 2007

We establish two server farm which service on two IP. 
BAS use that two IP as AAA server addresses.
Currently , number of accouting server is much less
than authentication server although DB connection
allocated to accouting server is nearly the same to
authentication servers.

The problem is,  radius server responding speed may
become very slow ( more than 100s) at peak time. some
of radius accouting packets overflows when they are
sent to radius server process queue. As radius
responding speed is slow, BAS retransmit those packets
in queue, the system performance worsen for 
duplicated packets. some dial-session is not closed
normally because Accouting-off packets are lost or

I plan to deal with the problem by starting at
incoming packets rate measurement, and server
structure  optimization. But, there seems to be too
few material available. 


--- K K <kkadow at gmail.com> wrote:

> On 5/3/07, Joe Shen <joe_hznm at yahoo.com.sg> wrote:
> > Is there any recommendation on Ratio between
> number of
> >  radius accouting server and number of radius
> > authentication server, if accouting and
> authentication
> > are executed by different hardware platform ?
> I generally deploy just two accounting servers,
> because (most)
> RADIUS-enabled devices deal with
> caching/retransmitting accounting
> data in a reasonable fashion if the accounting
> servers are slow or
> unresponsive -- users won't notice if Accounting is
> slow, quite the
> opposite of Authentication.
> Many (most?) RAS/VPN/etc devices only support
> configuring two RadAcct
> servers, even devices which offer up to 4 total auth
> servers might
> only allow 2 for accounting.  Also keep in mind that
> some devices use
> a primary/backup configuration, while other
> implementations send all
> Accounting records to *both* servers at all times.
> > Is there any way to estimate the burst rate of
> radius
> > protocol packet in ISP network?
> You can calculate your burst rate by either
> post-processing the RADIUS
> event logs from the servers, or from NetFlow data. 
> The real-world PPS
> rate and BPS for RADIUS should be very low, even on
> a busy ISP -- our
> biggest problem with RADIUS traffic isn't the
> traffic itself, but
> rather giving the protocol priority on congested WAN
> links so it isn't
> dropped by an oversubscribed router.  Dropped
> packets are primarily a
> problem for authentication requests, particularly if
> you're using
> RADIUS with SecurID (due to the built-in
> multi-second delay ACE/Server
> forces for all authentication requests, RADIUS or
> otherwise).
> Kevin
> --
> Moderator, unofficial RSA ACE/Server + SecurID users
> group:
> http://tech.groups.yahoo.com/group/securid-users/

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