USENIX 2005 Annual Technical Conference, FREENIX Track Abstract
Pp. 95108 of the Proceedings
Ourmon and Network Monitoring Performance
James R. Binkley and Bart Massey, Portland State University
Ourmon is an open-source network management and anomaly
detection system that has been developed over a period of
several years at Portland State University. Ourmon monitors
a target network both to highlight abnormal network traffic
and measure normal traffic loads. In this paper, we
describe the features and performance characteristics of Ourmon.
Ourmon features include a novel mechanism for running
multiple concurrent Berkeley Packet Filter (BPF) expressions
bound to a single RRDTOOL-style graph, as well as various
types of "top talker" (top-N) filters aimed at conventional
network flow measurements and anomaly detection. These
features permit a variety of useful and easily-understood
One problem that sniffer-based network monitor systems face
is network-intensive attacks that can overwhelm monitoring
and analysis resources. Lab experiments with an IXIA
high-speed packet generator, as well as experiences with
Ourmon in a real network environment, demonstrate this
problem. Some recent modifications to Ourmon have greatly
improved its performance. However, minimum-size packets in a
high-speed network can still easily make a host lose packets
even at relatively slow rates and low monitor workloads. We
contend that small packet performance is a general network
security problem faced by current monitoring systems including
both open source systems such as Ourmon and
Snort, and commercial systems.
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