Network Emulation

Links description

Enos allows to enforce network emulation in terms of latency and bandwidth limitations.

Network constraints (latency/bandwidth limitations) are enabled by the use of groups of nodes. Resources must be described using a topology description instead of a resources description. The following example will define 4 groups named grp1, grp2, grp3 and grp4 respectively:

topology:
  grp1:
    paravance:
      control: 1
      network: 1
  grp[2-4]:
    paravance:
      compute: 1

Constraints are then described under the network_constraints key in the configuration file:

network_constraints:
  enable: true
  default_delay: 25ms
  default_rate: 100mbit
  default_loss: 0.1%
  constraints:
    - src: grp1
      dst: grp[2-4]
      delay: 10ms
      rate: 1gbit
      loss: 0%
      symetric: true

To enforce the constraints, you can invoke:

enos tc

Note that The machines must be available, thus the up phase must have been called before.

As a result

• the network delay between every machines of grp1 and the machines of the other groups will be 20ms (2x10ms: symetric)

• the bandwidth between every machines of grp1 and the machines of the other groups will be 1 Gbit/s

• the packet loss percentage between every machines of grp1 and the machines of the other groups will be 0%.

• the network delay between every machines of grp2 and grp3 (resp. grp2 and grp4) (resp. grp3 and grp4) will be 50ms

• the bandwidth between every machines of grp2 and grp3 (resp. grp2 and grp4) (resp. grp3 and grp4) will be 100Mbit/s

• the packet loss percentage between every machines of grp2 and grp3 (resp. grp2 and grp4) (resp. grp3 and grp4) will be 0.1%

Checking the constraints

Invoking

enos tc --test

will generate various reports to validate the constraints. They are based on fping and flent latency and bandwidth measurements respectively. The reports will be located in the result directory.

Notes

• default_delay, default_rate, default_loss are mandatory

• To disable the network constraints you can specify enable: false under the network_constraints key and launch again enos tc

• To exclude a group from any tc rule, you can add an optionnal except key to the network_constraints:

network_constraints:
  enable: true
  default_delay: 25ms
  default_rate: 100mbit
  default_loss: 0%
  constraints:
    - src: grp[1-3]
      dst: grp[4-6]
      delay: 10ms
      rate: 1gbit
      symetric: true
  except:
    - grp1