02: Discover
How does SD-WAN Work?
As a very simple example between a hub and spoke, an SD-WAN policy enables how traffic between them will move on the underlay links that they are connected with. So, an SD-WAN policy can say that “Media traffic” from Site 1 takes “Link 1” to go to the Hub, and another SD-WAN Policy can say that “Collaboration” traffic from Site 1 takes “Link 2”, as it is a more reliable and faster link.
An SD-WAN Policy can further be configured to say that, all my “Collaboration” traffic from Spoke 1 takes “Link 2” as long as the quality of the traffic is meeting a certain threshold. If the quality threshold is not being met, switch over to Link 1 to ensure that the quality is being retained. The threshold that needs to be met is defines as an SLA profile (Service Level Agreement) Profile. The quality of the traffic between 2 sites is denoted by parameters like “Packet Loss”, “Latency”, “Jitter”.
When traffic is being sent from one campus to the other, it takes a data link to travel. Each link is classified into 8 different types of queues for 8 different types of classes of data. So for eg, there could be a separate queue for all the “Voice” traffic going on the link, a separate queue for “Video”, and a separate queue for “Important-Data” if certain type of data is classified like that.
Each of these queues can have their own configurations which define how the traffic moves in them, and QoS settings enables the network admin to define those properties for each queue.
02: Discover
How do you define an SD-WAN Policy?
For a Tenant network admin to define an SD-WAN Policy, they have to take a stepped approach, where first they familiarize themselves with something called a “Traffic Profile” which defines the configurations for the different queues that carry different classes or types of data. These traffic profiles define the different traffic types and their configuration.
Once familiarized, the Tenant Admin defines an SLA profile or a quality threshold, per traffic type, saying that “For my Video traffic, I want these quality parameters, and I want the traffic to take this link”. These "quality parameters" are stored in the SLA Profile as "SLA Parameters" and the link they prefer is denoted as "Path Preference".
Once an SLA profile is created, the Tenant Admin, defines the policy saying, “For my Social Applications from Campus 1, I want the data to maintain the quality parameters defined in SLA Profile 1”. Thus, selecting the Source Location, the Application, and the SLA Profile with the SLA parameters.