used by individual connections, it cannot report the process name/id involved in the particular socket connection. But being based on the pcap library, iftop is able to filter the traffic and report bandwidth usage over selected host connections as specified by the filter.$ sudo iftop -nThe n option prevents iftop from resolving ip addresses to hostname, which causes additional network traffic of its own.Install iftop - Ubuntu/Debian/Fedora users get it from default repos. CentOS users get it from Epel.# fedora or centosyum install iftop -y# ubuntu or debian$ sudo apt-get install iftop3. iptrafIptraf is an interactive and colorful IP Lan monitor. It shows individual connections and the amount of data flowing between the hosts. Here is a screenshot$ sudo iptrafInstall iptraf# Centos (base repo)$ yum install iptraf# fedora or centos (with epel)$ yum install iptraf-ng -y# ubuntu or debian$ sudo apt-get install iptraf iptraf-ng4. nethogsNethogs is a small 'net top' tool that shows the bandwidth used by individual processes and sorts the list putting the most intensive processes on top. In the event of a sudden bandwidth spike, quickly open nethogs and find the process responsible. Nethogs reports the PID, user and the path of the program.$ sudo nethogsInstall Nethogs - Ubuntu, Debian, Fedora users get from default repos. CentOS users need Epel# ubuntu or debian (default repos)$ sudo apt-get install nethogs# fedora or centos (from epel)$ sudo yum install nethogs -y5. bmonBmon (Bandwidth Monitor) is a tool similar to nload that shows the traffic load over all the network interfaces on the system. The output also consists of a graph and a section with packet level details.Install Bmon - Ubuntu, Debian and Fedora users can install from default repos. CentOS users need to setup repoforge, since its not available in Epel.# ubuntu or debian$ sudo apt-get install bmon# fedora or centos (from repoforge)$ sudo yum install bmonBmon supports many options and is capable of producing reports in html format. Check the man page for more information6. slurmSlurm is 'yet' another network load monitor that shows device statistics along with an ascii graph. It supports 3 different styles of graphs each of which can be activated using the c, s and l keys. Simple in features, slurm does not display any further details about the network load.$ slurm -s -i eth0Install slurm# debian or ubuntu$ sudo apt-get install slurm# fedora or centos$ sudo yum install slurm -y7. tcptrackTcptrack is similar to iftop, and uses the pcap library to capture packets and calculate various statistics like the bandwidth used in each connection. It also supports the standard pcap filters that can be used to monitor specific connections.Install tcptrack - Ubuntu, Debian and Fedora have it in default repos. CentOS users need to get it from RepoForge as it is not available in Epel either.# ubuntu, debian$ sudo apt-get install tcptrack# fedora, centos (from repoforge repository)$ sudo yum install tcptrack8. VnstatVnstat is bit different from most of the other tools. It actually runs a background service/daemon and keeps recording the size of data transfer all the time. Next it can be used to generate