Just as applications migrated from physical servers to VMs, network functions are moving from dedicated hardware to VMs. In order to provide rich networking for virtualized applications, it is important that SDN solutions support the ability to redirect application traffic through different network functions such as firewalls, DPI, load balancers, and so on. This ability of the SDN platform is referred to as service chaining and the specialized network functions are referred to as service instances.
Advanced network services such as firewalls, IDP, load balancers, and so on, usually operate at L4 to L7 of the networking stack. This means that an L3-based overlay network is well suited to support chaining since OpenContrail takes care of L3 packet forwarding. Service chaining in OpenContrail mostly deals with traffic steering, which is the ability to force network traffic in a well-defined and controlled manner so that the traffic flows can be processed...