[cisco-bba] PPP: limiting number of concurrent sessions

Victor Lyapunov victor.lyapunov at gmail.com
Mon Dec 15 14:22:45 EST 2008

Hello all

The company I work for has a number of cisco routers acting solely as
LAC, providing wholeshale services to other ISPs that terminate the
subscriber PPP sessions in their LNS.

We plan to start terminating the PPP sessions directly to our routers.
Since we want limit the max-concurrent sessions per user to 1, we have
 to make sure that the radius can reliably detect and avoid double logins.

We shall use free radius and expect to serve 100.000+ customers. Since
radius protocol is not 100% reliable, extra mechanisms are often used
when such a limit is imposed for the max concurrent sessions per user
(e.g. the radius using telnet, finger or SNMP can contact the BRAS and
verify if a particular user is already logged in or not)

I want to ask from your experience what is the prefered method for
avoiding double logins especially when such a large number of subscribers
has to served?

I am concerned that having the radius to contact the BRAS in-order to
verify each double login attempt will result to a heavy performance impact
for the BRAS


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