Practical VoIP Using VOCAL

Chapter 17. System Monitoring

The Network Management System is based on the Simple Network Management Protocol (SNMP) project that originated at Carnegie Mellon University (CMU) and the University of California at Davis (UCD) and is now available from the Net-SNMP pages on SourceForge.Net (http://net-snmp.sourceforge.net). Starting from this code, which includes a stack and a daemon, we built a system that provides network statistics; a GUI interface for monitoring, stopping, and starting servers; and a heartbeating mechanism that allows VOCAL servers to be aware of which servers are up and which are down at any given time.

SNMP works through a dedicated port, which creates a problem if you are running a multiserver system like VOCAL on one host. Our solution was to build an agent to interface with each process and send data back to the Network Manager through the SNMP port to a GUI or another collection point. As you will see in our illustrations and discussion, the agent works with a simple, proprietary protocol called Agent API that provides a conduit between the different processes and the SNMP tools.

SNMP Support

VOCAL supports Version 2 of the Simple Network Management Protocol (SNMP, RFC 1157). If you are new to this protocol, there is good documentation and a set of tutorials on the Net-SNMP site. Before looking at our implementation, let’s review a few SNMP terms and commands as reference points for this discussion.

Elements

SNMP works with these two elements: ...