In computer networks, network traffic measurement is the process of measuring the amount and type of traffic on a particular network. This is especially important with regard to effective bandwidth management.
Network performance could be measured using either active or passive techniques. Active techniques (e.g. Iperf) are more intrusive but are arguably more accurate. Passive techniques are of less network overhead and hence can run in the background to be used to trigger network management actions.
A range of studies have been performed from various points on the Internet. The AMS-IX (Amsterdam Internet Exchange) is one of the worlds largest Internet exchanges. It produces a constant supply of simple Internet statistics. There are also numerous academic studies that have produced a range of measurement studies   on frame size distributions, TCP/UDP ratios and TCP/IP options.
Some of the available tools include:
- Argus processes packets into detailed network flow audit data for operations, performance and security management.
- Cacti allows a user to poll services at predetermined intervals and graph the resulting data.
- cFosSpeed performs traffic classification and lets the user display, shape, tag or rate-limit protocols or programs under Windows.
- FlowMon is a complete solution for NetFlow monitoring and analysis including probes up to 10 Gbit/s, collectors and other supervision systems.
- InterMapper Originally developed for the Macintosh Classic in 1994 by the network manager of Dartmouth College this application uses SNMP, Ping and Netflow to build a graphical network map similar to HP Openview which shows bandwidth usage by port information and protocol. VLAN aware. Supported platforms: MacOS X, Linux and Windows.
- LiveAction provides real-time routing layer visualizations that allow the user to see and troubleshoot routes and implement policy-based routing.
- NetLimiter is a traffic monitoring and shaping software for Windows.
- ntopng is an open-source, real-time, web-based traffic monitoring for Unix (Linux, MacOS X, FreeBSD) and Window systems.
- OmniPeek is an end-to-end network monitoring solution, offering support for many packet adapters and remote collectors.
- Observium is an autodiscovering network monitoring application focusing on extensive data collection and graphing of network infrastructure.
- PRTG runs on Windows, with graphical and web interfaces. It captures packets using Cisco Netflow or packet sniffing or uses SNMP to monitor bandwidth usages.
- Wireshark network packet logger, visualizer, inspector, some analyses.
- PacketTrap Networks – Traffic and Traffic Flow Analyzer
- Scrutinizer NetFlow and sFlow Analyzer provides deep visibility into network traffic behavior and trends. Leveraging NetFlow, J-Flow, and sFlow data, NetFlow Traffic Analyzer identifies which users and applications are consuming the most bandwidth.
- Sparrowiq Packet-based network traffic monitoring and analytics.
- Sandvine Intelligent Network Solutions measure and manage network traffic using Policy Traffic Switches
- SevOne Network Performance Monitoring System.
everybody says thanks to wikipedia