With IPHost Network Monitor you can run simple snmp requests against a Netscreen device in your network.
nsPlySrcZone
NETSCREEN Ply Source Zone
1.3.6.1.4.1.3224.10.1.1.3
Traffic through a firewall means that traffic flows from one security zone to another. This object describes the source zone name traffic flow passes.
Back to NETSCREEN-POLICY-MIB MIB page.
IPHost Network monitor allows you to monitor nsPlySrcZone on Netscreen device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Netscreen firewalls right now.