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Client connectivity Applies To: Office 365 Admin, Microsoft 365 Business
Summary: Explains how client computers connect to Office 365 tenants, depending on the location of the client computer and Office 365 tenant datacenter. Office 365 resides in Microsoft datacenters around the world which help keep the service up and running even when there’s a major problem in one region, such as an earthquake or a power outage. When you connect to your Office 365 tenant, the client connection will be directed to the appropriate datacenter where your tenant is being hosted. The rules that determine where your tenant can be hosted are defined by your agreement with Microsoft. The rules that determine how your client acquires the data from that datacenter location depend on the architecture of the service you're using. For example, when you log on to the Office 365 portal, you’re usually connected to the closest datacenter to the client and then directed depending on the service you use next. If you launch email, the initial connection to display the UI may still come from the nearest datacenter, but a second connection might be opened between the nearest datacenter and the datacenter where your tenant is located to show you what’s in the emails you read. Microsoft operates one of the top ten networks in the world resulting in incredibly fast datacenter-to-datacenter connections fast. After you read the article, you’ll likely understand why we don’t provide Office 365 URLs and IP address ranges per datacenter, they are simply too interconnected and reliant on each other to make that feasible. If you’re using Azure ExpressRoute for Office 365, in most cases your connectivity will go over a private connection to Office 365 instead of the public connection described here. The principles about how clients connect are still accurate. Learn more about Azure ExpressRoute for Office 365. For more depth on Skype for Business network requests, read the article Media Quality and Network Connectivity Performance in Skype for Business Online.
This article is part of Network planning and performance tuning for Office 365
Note: We take great care to manage customer data so it’s secure and private in our datacenters. Details about the steps we take to manage privacy are included in the Trust Center.
Connecting to the nearest datacenter This is the most common type of connection, and it’s used by both the Office 365 portal and Exchange Online. In this situation, when clients attempt to connect to Office 365, their computer’s DNS query determines the region of the world their computer is coming from, and Office 365 redirects the request to the nearest datacenter. Connections to the portal stop at the nearest datacenter, and the client computer is presented with information about the client’s tenant from that location. Exchange Online goes a step further. Once the client computer is connected to the nearest datacenter, an Exchange server in that datacenter connects to the datacenter where the tenant is actually located as illustrated in the How does this work section below. The Exchange Online servers in the nearest datacenter then proxy the requests from the client computer to the mailbox server. This speeds up the experience for the client computer by moving the heavy lifting of retrieving emails and calendar items to the Microsoft network. How does this work for standard cloud offerings? How does this work for sovereign cloud offerings?
Connecting to the active datacenter Connecting to the active datacenter is designed for heavier data transfer workloads and is currently used by SharePoint Online. In this situation, when clients attempt to connect to Office 365, their browser is redirected to the active datacenter for their SharePoint Online tenant. How does this work?
Connecting over Virtual Private Networks (VPNs) This type of connection applies only when a virtual private network (VPN) is used by client computers. In reality, Office 365 behavior isn’t changed simply because a VPN is used, but VPNs are commonly used to control how client computers establish connections to Office 365 and usually results in a degraded experience, so it’s important to cover. How does this work?
See Also Managing Office 365 endpoints Network connectivity to Office 365
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