Open vSwitchにおけるin-band controlとout-of-band control

devstackでNeutron周りの設定ではまっているわけですが、Open vSwitchの設定に関してin-band controllがどうのこうのって話があってin-band controllが何なのかわからなかったので調べてみた。


管理用のNWを別途持つのがout-of-band controlで管理されるNWに一緒に管理情報も流しちゃうのがin-band controlって感じか。

In-Band Control


An OpenFlow switch must establish and maintain a TCP network connection to its controller.  There are two basic ways to categorize the network that this connection traverses: either it is completely separate from the one that the switch is otherwise controlling, or its path may overlap the network that the switch controls.  We call the former case "out-of-band control", the latter case "in-band control".

Out-of-band control has the following benefits:

  - Simplicity: Out-of-band control slightly simplifies the switch implementation.
  - Reliability: Excessive switch traffic volume cannot interfere with control traffic.
  - Integrity: Machines not on the control network cannot impersonate a switch or a controller.
  - Confidentiality: Machines not on the control network cannot snoop on control traffic.

In-band control, on the other hand, has the following advantages:

  - No dedicated port: There is no need to dedicate a physical switch port to control, which is important on switches that have few ports (e.g. wireless routers, low-end embedded platforms).
  - No dedicated network: There is no need to build and maintain a separate control network. This is important in many environments because it reduces proliferation of switches and wiring.