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Software-Defined Wide Area Network

Software-Defined Wide Area Network (SD-WAN) takes the concept of Software-Defined Networks and scales it to the cloud. It uses a combination of various network technologies, including MPLS, cellular, and broadband:

A Software-defined Wide Area Network (SD-WAN) is a virtual WAN architecture that allows enterprises to leverage any combination of transport services—including MPLS, LTE and broadband internet services—to securely connect users to applications. An SD-WAN uses a centralized control function to securely and intelligently direct traffic across the WAN and directly to trusted SaaS and IaaS providers. This increases application performance and delivers a high-quality user experience, which increases business productivity and agility and reduces IT costs [10].

SD-WAN can automatically provide the best connection for any user or application:

“SD-WAN lets networks route traffic based on centrally managed roles and rules, no matter what the entry and exit points of the traffic are, and with full security. For example, if a user in a branch office is working in Office365, SD-WAN can route their traffic directly to the closest cloud data center for that app, improving network responsiveness for the user and lowering bandwidth costs for the business” [11].

Virtual eXtensible Local Area Network

Virtual eXtensible Local Area Network (VXLAN) extends the concept of VLANs (Virtual Local Area Networks, discussed later this chapter) to the cloud. VLAN support 4096 segment IDs (or VLANs), limiting their use in large cloud deployments. VXLAN supports 16 million segment IDs (hence the name “eXtensible”), allowing global scale. VXLAN encapsulates data via UDP port 4789; the encapsulation and de-encapsulation is done by VTEPs (Virtual Tunnel Endpoints).

Juniper describes VXLANs:

VXLAN is a technology that allows you to segment your networks (as VLANs do) but also solves the scaling limitation of VLANs and provides benefits that VLANs cannot. Some of the important benefits of using VXLANs include:

  • You can theoretically create as many as 16 million VXLANs in an administrative domain (as opposed to 4094 VLANs).
  • VXLANs provide network segmentation at the scale required by cloud builders to support very large numbers of tenants.
  • With traditional Layer 2 networks you are constrained by Layer 2 boundaries and forced to create large or geographically stretched Layer 2 domains. VXLAN’s functionality allows you to dynamically allocate resources within or between data centers and enables migration of virtual machines between servers that exist in separate Layer 2 domains by tunneling the traffic over Layer 3 networks [12].