Waste not, WAN

Our existing circuits comfortably handle terabytes of new Office 365 traffic with Cisco SD-WAN technology

Before migrating to Office 365 in early 2019 we needed to make sure we had enough WAN capacity. At the outset we’d be transferring 500 TB of email—the equivalent of 19 years of streaming HD video1—from our on-premises Exchange servers to Microsoft’s cloud. After the initial transfer we’d need enough bandwidth to deliver a great ongoing experience with Office 365—and all our other cloud applications.

We successfully migrated the 500 TB—and without buying more WAN capacity. Instead we optimized the capacity we already had, using network peering and an SD-WAN technique called intelligent traffic steering.

Cutting out the “middleman” by linking our switches directly with Microsoft’s

Network peering keeps our WAN service provider costs down by getting rid of the “middleman” (Internet service providers). Large cloud providers like Microsoft host their services in carrier-neutral facilities called peering points. We have switches in many of the same facilities, including San Jose, Dallas, Hong Kong, and Singapore. In these facilities we have a direct peering relationship with Microsoft capable of bandwidth connections of up to 20Gbps. This architecture, which we call Cloudport, adds very little network overhead and provides a great user experience. We’re also using it for traffic destined to service providers, including Apple, Google, and Akamai.

The process was straightforward. We just went to www.peeringdb.com to see which data centers we and Microsoft were already both located in, emailed a request, paid a fee, and ran the fiber.

Steering Office 365 traffic to a direct Internet link

The other technique we use to optimize existing WAN capacity is called intelligent traffic steering. The idea is to steer Office 365 traffic to the best of an office’s two WAN links based on current conditions. We use traffic steering in our midsize offices, which have an MPLS leased line and an Internet link for backup.

Here’s how it works. Cisco SD-WAN Cloud OnRamp for SaaS (our intelligent traffic steering solution) detects if a request is going to Office 365. If so, it sends the request over the otherwise-idle Internet link if conditions are good. One advantage of intelligent traffic steering is creating a highly distributed content-delivery network (CDN) for Office 365. Another is improving Office 365 performance by sending traffic directly to the Internet instead of back-hauling it over the WAN to the corporate hub. Yet another is preserving MPLS bandwidth for applications that benefit from MPLS Quality of Service (QoS), like video. (Email and document access, in contrast, can tolerate a small amount of latency without anyone noticing.)

We’re currently running a production pilot with Cloud OnRamp for SaaS. The pilot includes 10 midsize offices connected to three network hubs. Currently, more than 90% of Office 365 traffic from our medium branch offices flows over Internet links. We’re “customer zero” for Cloud OnRamp, sharing our experiences with customers to help them deploy quickly.

Could we steer Office 365 traffic to the Internet link without Cloud OnRamp? Yes, in theory—but only with an enormous amount of ongoing work. We’d have to build access control lists (ACLs) to whitelist traffic to each of Microsoft’s Office 365 servers. That’s complicated because each server has a range of IP addresses, and our security teams rightly insist on knowing the device associated with every whitelisted IP address. We’d also need to update the ACLs monthly, whenever Microsoft changes its services—a huge operational burden. And all Office 365 traffic would be steered to the Internet, even if the MPLS link was a better path at the time. With Cloud OnRamp we have none of those problems.

Fast migration, fast WAN

With the combination of Cloud OnRamp and network peering, we migrated 500 TB of data from our data center to the Office 365 cloud without slowing down any applications. With more than enough bandwidth, we were able to migrate users’ data as fast as we could train them—5000 a week.

The application experience remains great. Our users can open SharePoint and OneDrive documents and access email as fast as they could before we moved to Office 365. In fact, when Microsoft reps were onsite to help us with Office 365 migration, a 150MB PowerPoint opened so fast that they assumed the file was cached. (Nope!)

To sum up, Cisco SD-WAN technologies are helping us get more from our existing circuits so that we can deliver a great Office 365 experience without higher WAN costs.

How have your cloud services affected WAN performance and costs? Ask questions here.