April 02, 2017

Overlay & Underlay Drivers

Overlay and Underlay Drivers

  • Overlay
  • Overlay network driver creates networking tunnels to enable communication across hosts. Containers on this network behave as if they are on the same machine by tunneling network subnets from one host to the next. It spans one network across multiple hosts. Several tunneling technologies are supported, e.g. virtual extensible local area network (VXLAN)
    • The overlay driver creates an overlay network that supports multi-host networks
    • uses a combination of local Linux bridges and VXLAN to overlay container-to-container communications over physical network infrastructure
    • utilizes an industry-standard VXLAN data plane that decouples the container network from the underlying physical network (the underlay)
    • encapsulates container traffic in a VXLAN header which allows the traffic to traverse the physical Layer 2 or Layer 3 network
    • Created when a Swarm is instantiated
  • Underlay
  • Underlay network drivers expose host interfaces, e.g. eth0, directly to containers running on the host. An example of an underlay driver is the Media Access Control virtual local area network (MACvlan).
    • Allows direct connection to the hosts' physical interface
    • MACvlan eliminates the need for the Linux bridge, NAT and port-mapping
    • The MACvlan establishes a connection between container interfaces and the host interface (or sub-interfaces)
    • used to provide IP addresses to containers that are routable on the physical network

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