Measuring packet latency, loss and jitter on RHEL & CentOS

If you experience quality issues on your network, you may want to look into monitoring your network to draw any clues about the issues. A tool called SmokePing comes handy in this case. SmokePing is one of the best network latency visualization tools available on Linux.

For latency visualization, SmokePing relies on a list of other probing utilities (e.g., fping, tcpping, etc.) to measure network latencies. The individual measurements generated by these probing utilities are then stored locally as time-series data. SmokePing use this data to visualize packet latency, loss and jitter over a time period.

In this tutorial, I will describe how to measure network latency, packet loss and jitter with SmokePing.

If SELinux is enabled on your system, SmokePing may not run properly. So make sure to disable SELinux on your system. To disable SELinux, edit /etc/selinux/config as follows, and reboot.

$ sudo vi /etc/selinux/config

To install SmokePing on Debian or Ubuntu, do the following:

$ sudo aptitude update
$ sudo aptitude install smokeping curl libauthen-radius-perl libnet-ldap-perl libnet-dns-perl libio-socket-ssl-perl libnet-telnet-perl libsocket6-perl libio-socket-inet6-perl apache2 sendmail

To install SmokePing on Fedora, run:

$ sudo yum install smokeping

Once you have installed SmokePing, configure it as follows.

$ sudo vi /etc/smokeping/config.d/General
cgiurl = http://ip_address_of_your_host/cgi-bin/smokeping.cgi

By default, SmokePing will measure network latencies for local host, by using fping. You can customize this default settings as you wish (e.g., add additional probing destinations, change probing tools, etc). Read on to learn how to customize SmokePing settings.

To configure probing tools to use in SmokePing, edit the following.

$ sudo vi /etc/smokeping/config.d/Probes
+ FPing

binary = /usr/bin/fping
offset = 50%
step = 60
timeout = 10
pings = 5

+ TCPPing

binary = /usr/bin/tcpping
forks = 5
offset = 50%
step = 60
timeout = 10
pings = 5

In the above example, I define two probing tools: fping and tcpping. The former uses ICMP packets to measure latencies, while the latter uses TCP packets. tcpping is useful when a destination host blocks ICMP packets.

  • binary: path for a given probing tool.
  • fork: how many processes to use for probing.
  • offset: how varied multiple concurrent probes are in terms of their launch time within a given time interval.
  • step: duration of time interval (in seconds) for probing.
  • timeout: timeout value to be used in a given probing tool.
  • pings: how many pings should be sent in each time interval.

To configure a list of destination hosts to probe, edit the following.

$ sudo vi /etc/smokeping/config.d/Targets
probe = FPing
menu = Latency
title = Latency Measurement
remark = SmokePing Latency Test.

+ Internal_Host
menu = Internal_Hosts
title = Cloud Latency Measurements

++ Home
title = Home
host =

++ Verizon_FIOS
title = Verizon FIOS
host =

++ Optimum
title = Optimum Online
host =

++ EC2
title = EC2 East
host =

++ Azure
title = Azure East
host =

+ External_Router
menu = External_Routers
title = Cloud Latency Measurements
probe = TCPPing

++ Verizon_DSL
title = Verizon DSL
probe = TCPPing
host =

You can customize the above file as you want. For each probing target (under “++”), you can define a custom probing tool to use (e.g., “probe = TCPPing”). For a complete list of probing tools that are compatible with SmokePing, refer to this list. Note that you will need to install any necessary probing tools separately if you decide to use them.

Whenever you change SmokePing configuration, be sure to restart SmokePing as follows.

On Ubuntu or Debian:

$ sudo /etc/init.d/smokeping restart

On Fedora:

$ sudo service smokeping restart

SmokePing may fail to restart if there are existing measurements collected based on the previous configuration, and the updated configuration is not compatible with existing measurements. In that case, you will need to remove previously collected measurements (located in /var/lib/smokeping) in order to be able to restart SmokePing.

You can browse latency measurements visualized by SmokePing at http://ip_address_of_your_host/cgi-bin/smokeping.cgi. This web page will automatically be refreshed as latency measurements are accumulated.

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