SNMP is the widely used device specific monitoring method. With continued improvements in the performance of SNMP data collection and serving methods, SNMP-based monitoring is now more applicable to real-time data collection, beyond traditional network management and trends gathering for capacity planning. Often, the user of an SNMP based monitoring system intends to make a selection of variables to be read over a duration during which monitoring is required, for example, just to get a snapshot of some resource utilization such as link utilization, traffic class utilization on some selected target routers when conducting network testing. In such cases, some kind of interactive monitoring system that provides the possibility to start and stop monitoring is often desired. The user of such a system requires an appropriate user interface through which selections of what to monitor can be made on-demand, and real-time traffic graphs can be displayed automatically. This paper describes how to design SNMP-based monitoring systems, supporting ubiquitous access and real-time visualization of traffic flow, using low cost tools. The concepts presented in this paper are backed by our implementation of a tool called SVM (SNMP-based visualization monitor) for QoS monitoring via access to QoS MIBs in DiffServ routers.