NMS Softwares
There are many simple and complicated Netowrk Management and Performance Monitoring softwares available out there, for free or commercially. From commercial softwares, I have very good experiences with HP OpenView, CiscoWorks, and from free ones, Nagios, Cacti, JFFNMS and NMIS.
But most network engineers prefer their own set of tools which is almost a combination of MRTG, RRDTool, SmokePing and Net-SNMP.
Most of the ready-to-use NMS software packages does not fit our needs. It's always a good idea to make your own set of monitoring scripts in conjunction with existing tools such as rrdtool, net-snmp or fping.
I use Cacti and JFFNMS for different tasks in our NOC, and also have my own set of scripts that adds more capabilities to the system.
JFFNMS has too many features but lacks a user friendly interface. One of its best features is supporting SLAs. So you can measure the uptime and quality of service against predefined SLAs. It also supports syslog and TACACS+ authentication which is a very handy feature in service provider environments.
Cacti is much simpler and easier to use, and is a great tool for NOC operators to have an overall look on their network performance.
An extensive set of tools for network management and monitoring, named COSI-NMS is available at http://cosi-nms.sourceforge.net/.
The problem that most of these packages have (at least the free ones) is the ease of integration between them. some, like rrd, mrtg, smokeping, and cacti, can be tied together on the backend, but don't integrate that easily on the front end and don't integrate at all with a ticket system or knowledge base.
nagios provides a good framework, but lacks the traffic graphing (or easy plugins for your favorite traffic-graphing software).
it would be nice to see an nms system that is truly open and modular, so you can pick pieces of great software packages and cobble them together easily for yourself, instead of being stuck with the built-in functionality any single package brings.
danno