Control Link Impairment Parameters

The netlab tc command can be used to disable, enable, display, or modify link impairment parameters on libvirt virtual machines or containerlab-created Docker containers.

Warning

You cannot configure link impairment on point-to-point links between ‌libvirt virtual machines that do not have ‌tc attributes; you have to change them into Linux bridges (more details).

The netlab tc command has several subcommands:

• netlab tc disable disables traffic control on one or more interfaces

• netlab tc enable restores the link impairment parameters specified in the lab topology

• netlab tc show display the netem traffic control policies configured on the specified interfaces

• netlab tc set replaces or modifies netem traffic control parameters on the specified interfaces

Usage

usage: netlab tc [-h] [-v] [-q] [--instance INSTANCE] {enable,disable,show,set} ...

Link impairment and traffic control utilities

options:
  -h, --help            show this help message and exit
  -v, --verbose         Verbose logging (add multiple flags for increased verbosity)
  -q, --quiet           Report only major errors
  --instance INSTANCE   Specify lab instance to work on

netlab clab subcommands:
  {enable,disable,show,set}

Use 'netlab tc subcommand -h' to get subcommand usage guidelines

Disable the Link Impairment

usage: netlab tc disable [-h] [-n NODE] [-i INTF] [--all]

Disable link impairments

options:
  -h, --help            show this help message and exit
  -n NODE, --node NODE  Disable traffic control only on selected node
  -i INTF, --interface INTF
                        Disable traffic control only on selected interface
  --all                 Disable traffic control on all lab links

You can use the netlab tc disable command to remove netem traffic control policy from:

• Individual interfaces (specify --node and --interface parameters)

• All interfaces of a specified node (specify only the --node parameter)

• All interfaces having tc attributes in the lab topology (omit --node and --interface parameters)

• All lab interfaces (with the --all flag)

Restore the Lab Topology Link Impairment Parameters

usage: netlab tc enable [-h] [-n NODE] [-i INTF]

Enable topology-defined link impairments

options:
  -h, --help            show this help message and exit
  -n NODE, --node NODE  Enable traffic control only on selected node
  -i INTF, --interface INTF
                        Enable traffic control only on selected interface

You can use the netlab tc enable command to restore the link impairment parameters specified in the lab topology on:

• Individual interfaces (specify --node and --interface parameters)

• All interfaces of a specified node (specify only the --node parameter)

• All interfaces having tc attributes in the lab topology (omit --node and --interface parameters)

Display the Link Impairment Parameters

$ netlab tc show -h
usage: netlab tc show [-h] [-n NODE] [-i INTF]

Display configured traffic control

options:
  -h, --help            show this help message and exit
  -n NODE, --node NODE  Display traffic control only on selected node
  -i INTF, --interface INTF
                        Display traffic control only on selected interface

Use the netlab tc show command to display netem traffic control parameters configured on specified nodes, interfaces, or the whole lab (when you execute the command without --node or --interface parameter).

Example:

$ netlab tc show
[INFO]    Traffic control on n1 eth2: limit 1000 rate 200Kbit
[INFO]    Traffic control on n2 eth2: limit 1000 delay 300ms

Set or Modify the Link Impairment Parameters

usage: netlab tc set [-h] [-n NODE] [-i INTF] [--corrupt CORRUPT] [--delay DELAY]
                     [--duplicate DUPLICATE] [--jitter JITTER] [--loss LOSS]
                     [--rate RATE] [--reorder REORDER] [--modify]

Set or modify traffic control parameters

options:
  -h, --help            show this help message and exit
  -n NODE, --node NODE  Change traffic control only on selected node
  -i INTF, --interface INTF
                        Change traffic control only on selected interface
  --corrupt CORRUPT     Percentage of corrupt packets
  --delay DELAY         Delay in msec
  --duplicate DUPLICATE
                        Percentage of duplicate packets
  --jitter JITTER       Jitter in msec
  --loss LOSS           Percentage of lost packets
  --rate RATE           Rate in kbps
  --reorder REORDER     Percentage of reordered packets
  --modify              Modify existing traffic control parameters

Use the netlab tc set command to set or modify netem traffic control parameters on specified nodes, interfaces, or all lab interfaces (when you execute the command without --node or --interface parameter).

Unless you use the --modify keyword, the specified parameters will overwrite the current link impairment parameters.

Example:

$ netlab tc show
[INFO]    Traffic control on n1 eth2: limit 1000 rate 200Kbit
[INFO]    Traffic control on n2 eth2: limit 1000 delay 300ms

$ netlab tc set --node n1 --interface eth2 --delay 10
[INFO]    Traffic control on n1 eth2: delay 10.0ms 0ms

$ netlab tc show
[INFO]    Traffic control on n1 eth2: limit 1000 delay 10ms
[INFO]    Traffic control on n2 eth2: limit 1000 delay 300ms

$ netlab tc set --node n1 --interface eth2 --rate 200 --modify
[INFO]    Traffic control on n1 eth2: rate 200000.0

$ netlab tc show
[INFO]    Traffic control on n1 eth2: limit 1000 rate 200Kbit
[INFO]    Traffic control on n2 eth2: limit 1000 delay 300ms