[j-nsp] Session utilization is 90% of the system capacity

[Vincent De Keyzer]

Hello,

we have a Netscreen 25 at our office (30 people), that we use for 
Internet access and VoIP.

 From time to time the firewall goes bananas: traffic does not go 
through anymore, ping success rate to default gateway is very low, and 
if we succeed to login, we see very high CPU and messages in the log 
that say:

2008-03-13 15:08:31 system crit  00051 Session utilization has reached 
28857,
                                       which is 90% of the system capacity!
2008-03-13 15:08:29 system crit  00051 Session utilization has reached 
28857,
                                       which is 90% of the system capacity!
2008-03-13 15:08:28 system crit  00051 Session utilization has reached 
28857,
                                       which is 90% of the system capacity!
2008-03-13 15:08:27 system crit  00051 Session utilization has reached 
28857,
                                       which is 90% of the system capacity!
2008-03-13 15:08:26 system crit  00051 Session utilization has reached 
28857,
                                       which is 90% of the system capacity!
2008-03-13 15:08:24 system crit  00051 Session utilization has reached 
28857,
                                       which is 90% of the system capacity!
2008-03-13 15:08:19 system crit  00051 Session utilization has reached 
28857,
                                       which is 90% of the system capacity!
2008-03-13 15:08:18 system crit  00051 Session utilization has reached 
28857,
                                       which is 90% of the system capacity!
2008-03-13 15:08:16 system crit  00051 Session utilization has reached 
28857,
                                       which is 90% of the system capacity!

How do I troubleshoot this? What are those sessions? How do I identify 
them? How do I limit them? Is it a good thing to limit them?

I don't know where to start, so any idea will be appreciated.

Thanks

Vincent