VILLASnode supports the emulation of wide-area network characterisics.

This emulation can be configured on a per-node basis for outgoing (egress) data only. Incoming data is not processed by the network emulation!

This network emulation is handled by Linux' netem queuing discipline which is part of the traffic control subsystem. Take a look at the following manual page for supported metrics: tc-netem(8).

VILLASnode only takes care of setup and initalizing the netem queuing discipline inside the kernel. For this the iproute2 software package (ip & tc commands) must be installed. The configuration is done via the config file. Look at etc/example.conf for a section called netem or tc-netem(8) for more details.

Fix for Fedora

For some reason, Fedora installs the delay distribution profiles under /usr/lib64/tc/. But libnl3 only seraches /usr/lib/tc/. This results in the following error when using netem:

Invalid delay distribution 'normal' in netem config in

To fix this error please add a symlink: ln -s /usr/lib64/tc /usr/lib/tc

Custom delay distribution

Netem supports loading custom delay distributions.

Load and compile the netem tools from: https://git.kernel.org/cgit/linux/kernel/git/shemminger/iproute2.git/tree/netem
Create a custom distribution by following the steps described here: https://git.kernel.org/cgit/linux/kernel/git/shemminger/iproute2.git/tree/README.distribution
Put the generated distrubtion with the suffix .dist in the tc lib directory: /usr/lib/tc/.
Load the distribution specifying the basename in the server config.

Further information

Weather or not network emulation is active.

Additional latency in micro seconds.

Packet delay jitter in micro seconds.

Distribution of delay: uniform, normal, pareto, paretonormal

Packet loss in percent.

Packet duplication in percent.

Packet corruption in percent.

Example

nodes = {
        udp_node = {                                    # The dictionary is indexed by the name of the node.
                type = "socket",                        # For a list of available node-types run: 'villas-node -h'
        ### The following settings are specific to the socket node-type!! ###
                format  = "gtnet",                      # For a list of available node-types run: 'villas-node -h'
                in = {
                        address = "127.0.0.1:12001"     # This node only received messages on this IP:Port pair
                },
                out = {
                        address = "127.0.0.1:12000",    # This node sents outgoing messages to this IP:Port pair
                
                        netem = {                       # Network emulation settings
                                enabled = true,
                                                        # Those settings can be specified for each node invidually!
                                delay = 100000,         # Additional latency in microseconds
                                jitter = 30000,         # Jitter in uS
                                distribution = "normal", # Distribution of delay: uniform, normal, pareto, paretonormal
                                loss = 10               # Packet loss in percent
                                duplicate = 10,         # Duplication in percent
                                corrupt = 10            # Corruption in percent
                        }
                }
        }
}