The Wide Area Network (WAN) is the backbone of the business. It ties together the remote locations, headquarters and data centers into an integrated network. Yet, the role of the WAN has evolved in recent years. Beyond physical locations, we now need to provide optimized and secure access to Cloud-based resources for a global and mobile workforce. The existing WAN optimization and security solutions, designed for physical locations and point-to-point architectures, are stretched to support this transformation.
This paper discusses the different connectivity, optimization and security options for the ‘Next Generation WAN’ (NG-WAN). The NG-WAN calls for a new architecture to extend the WAN to incorporate the dynamics of cloud and mobility, where the traditional network perimeter is all but gone.
The Wide Area Network (WAN) connects all business locations into a single operating network. Traditionally, WAN design had to consider the secure connectivity of remote offices to a headquarters or a data center which hosted the enterprise applications and databases.
Let’s look at evolution of the WAN
First Generation: Legacy WAN Connectivity
Currently, there are 2 WAN connectivity options which offer a basic trade off between cost, availability and latency:
Option 1: MPLS
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With MPLS, a telecommunication provider provisions two or more business locations with a managed connection and routes traffic between these locations over their private backbone. In theory, since the traffic does not traverse the internet, encryption is optional. Because the connection is managed by the telco, end to end, it can commit to availability and latency SLAs. This commitment is expensive and is priced by bandwidth. Enterprises choose MPLS if they need to support applications with stringent up-time requirements and minimal quality of service (such as Voice over IP (VOIP).
To maximize the usage of MPLS links, WAN optimization equipment is deployed at each end of the line, to prioritize and reduce different types of application traffic. The effectiveness of such optimizations is protocol and application specific (for example, compressed streams benefit less from WAN optimization).
Option 2: Internet
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Internet connection procured from the ISP, typically offers nearly unlimited last mile capacity for a low monthly price. An unmanaged internet connection doesn’t have the high availability and low-latency benefits of MPLS but it is inexpensive and quick to deploy. IT establishes an encrypted VPN tunnel between the branch office firewall and the headquarters/data center firewall. The connection itself is going through the internet, with no guarantee of service levels because it is not possible to control the number of carriers or the number of hops a packet has to cross. This can cause unpredictable application behavior due to increased latency and packet loss. Internet-based connectivity forces customers to deploy and manage branch office security equipment.
Second Generation: Appliance-based SD-WAN
The cost/performance trade off between internet and MPLS, gave rise to SD-WAN. SD-WAN is using both MPLS and internet links to handle WAN traffic. Latency sensitive apps are using the MPLS links, while the rest of the traffic is using the internet link. The challenge customers face is to dynamically assign application traffic to the appropriate link.
SD-WAN: Augmenting MPLS with Internet Links
SD-WAN solutions offer the management capabilities to direct the relevant traffic according to its required class of service, offloading MPLS links and delaying the need to upgrade capacity. SD-WAN solutions, however, are limited in a few key aspects:
Footprint: Similar to WAN optimization equipment, SD-WAN solutions must have a box deployed at each side of the link.
Connectivity: SD-WAN can’t replace the MPLS link because its internet “leg” is exposed to the unpredictable nature of an unmanaged internet connection (namely, its unpredictable latency, packet drops and availability).
Deployment: SD-WAN, like the other WAN connectivity options, is agnostic to the increased role of internet, Cloud and mobility within the enterprise network. It focuses, for the most part on optimizing the legacy, physical WAN.