Software Defined - Wide Area Network (SD-WAN) Services And Their Implementation On An Open Source Linux Based Platform

This first EveryWAN version support a set of services considered essentials for and SD-WAN solution. The services supported for the EveryEdge routers are Authentication, Registration, and Configuration which will be discussed later. The main service provided is the creation of Overlay networks through VxLAN encapsulation technique (and also SRv6) over the WAN link. An Overlay is a set of tunnels that carry traffic of a given type of service, and the tunnels are created between end-point (VTEP) of different involved EveryEdges. The Overlay can be created among Edges of the same tenant to interconnect different branch office of the same company in a full-mash topology.

The Overlays are used to interconnect the Slices that span on multiple sites, creating in this way an End-to-End Slice. A network Slice is an independent logical network that carry a specific type of service and is local to an Edge, as shown in Figure 17 the service type carry by a Slice can be IP-TV, VoIP, File-Transfer etc. An End-to-End Slice is a Slice that thanks to an Overlay expands across multiple customer sites. In EveryWAN implementation the ingress classification of the Slices is static and is based on the physical/virtual network interface using the so called VRF Lite approach, where each Slice Interface is individually mapped to an Overlay. On a given site there may be more than one Slice (i.e. LAN interfaces) that carry the same service. A given Slice interface can support a single subnet or can be set up several broadcasting domains behind it using a multi-subnet configuration. Using the VRF Lite approach brings the advantages of having traffic and routing isolation between different Slices and due to routing isolation the Overlay addressing can be reused. In a given Edge we can set the same IP address for all the Overlay end-points (VTEPs), in this way we are using just a single subnet for the Overlay addressing and no other private subnets are wasted, leaving them free for the customer Slicing addressing. Thanks to the Slice approach different services can run on different Slice and obtain the needed isolation requirements sharing the same connectivity. The isolation is maintained also on the transport network thanks to the use of VxLAN VNI, each set of tunnels which constitute an Overlay use the same VNI therefore different Overlay will have different VNI. The Overlays can use the VNIs from 2 to 224, instead the VNI 0 is reserved for VxLAN management tunnels. Our Overlays are based on tunnels that carry L3 traffic, this mean that the Slices spread on different Sites must have different broadcasting domains and each site’s end-pint acts as a getaway for the remote broadcasting domains. Thanks to the routing isolation the subnets can be reused among different Slices.

Using an overlaying approach introduce the advantages of abstracting the transport layer and being less dependent on the service providers and their network. Building an Overlay, we configure a logical instance of a multipoint network ensuring end-to-end connectivity through “virtual link” over the same WAN. We implemented a service-oriented SD-WAN where the tenants can redirect the traffic of a specific service over defined Overlay. In this way was facilitating the improvement of feature work in adopting multiple WAN networks, in which will be necessary to select which WAN interface to use for the forwarding of the traffic belonging to a particular Slice based on a customer defined policy.