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What's the difference between thin and thick SD-WAN branch offices?

When rolling out software-defined WAN, you'll need to consider the current makeup of your branch offices. For instance, are applications on-site or in the cloud?

For branch offices, IT typically chooses a thick or thin strategy, primarily driven by bandwidth considerations and on-site support. The former is primarily used with some on-site support and if bandwidth is constrained. The latter is typically chosen if there is no on-site support, applications are primarily cloud-based or the bandwidth is plentiful.

Software-defined WAN (SD-WAN) deployment decisions can be highly dependent on whether a thick or thin branch strategy is in place. To understand this nuance of networking further, let's dissect the differences between thin and thick SD-WAN branch offices.

For thick branches, applications usually run at the branch, so there is less reliance on the WAN connection to keep operations running. Thick customers may migrate to SD-WAN at a slower rate for two key reasons.

First, because IT resources are typically on-site, the SD-WAN orchestration benefits may not seem as compelling. Second, because applications run at the branch, bandwidth requirements are lower, meaning the existing transport -- typically, MPLS -- is probably not as oversubscribed. Application and database updates can be batched together and executed late in the evening to help minimize operational impact.

On the other hand, thin branches are more amenable to the SD-WAN benefits because these branches rely more heavily on the connection to headquarters. It is more likely, in a thin branch environment, that multiple transports are used because of the greater traffic requirements. An SD-WAN will better manage traffic across multiple transports, especially disparate transports.

As applications in a thin branch environment are more likely to be cloud-based, it will be easier to manage security and access through the centralized control that SD-WAN delivers. As on-site support is less likely, an SD-WAN's automation and orchestration will be a welcome relief for the headquarters IT teams that have to deal with remote support of the SD-WAN branch office.

Edge networking and security converge

In its 2019 Magic Quadrant for WAN Edge Infrastructure, analyst firm Gartner said one of the major decisions that businesses will increasingly need to make in the next few years is whether to select a thick or thin branch.

With a thick branch, Gartner said, all functions are deployed at the customer branch location. With a thin branch, some functions are on the WAN edge, which is supplemented by functions hosted in the cloud. A thick branch would be for organizations with stronger IT groups that want more control. A thin branch is for leaner IT groups seeking more operational flexibility.

The decision of thin branch vs. thick branch will also be a factor as networking and security services merge. As the security perimeter changes and customers seek to distribute internet access, SD-WAN branch locations will need to manage the internet transport. As a result, customers may look for vendors with a combined security and networking service.

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