The team determined the best way to meet current connection needs and also put Exchange in the position to innovate more quickly was to start with a new simplified architecture. Consider connections from cellular networks, home networks, or in-flight wireless networks as a few examples. The original Outlook Anywhere architecture wasn’t designed for today’s reality of clients connecting from a wide variety of network types – many of these are not as fast or reliable as what was originally expected when Outlook Anywhere was designed. You are probably asking yourself why the Exchange team would create a complete replacement for something so well-known and used. Depending on the number of Outlook clients reconnecting, the re-establishing of so many RPC/HTTP connections might strain the resources of the mailbox server, and possibly extend the outage in scope (to Outlook clients connected to multiple servers) and time, caused by a single server-side network blip.
Additionally in the past, an unexpected server-side network blip would result in all client sessions being invalidated and a surge of reconnections being made to a mailbox server.
This is extremely helpful for users who might be connecting from low quality networks. In MAPI/HTTP when a network connection is lost the session itself is not reset for 15 minutes and the client can simply reconnect and continue where it left off before the network level interruption took place. With Outlook Anywhere connectivity, if a network connection was lost between client and server, the session was invalidated and had to be reestablished all over again, which is a time-consuming and expensive operation. MAPI/HTTP removes the RPC encapsulation within HTTP packets sent across the network making MAPI/HTTP a more well understood and predictable HTTP payload.Īn additional network level change is that MAPI/HTTP decouples the client/server session from the underlying network connection. Outlook Anywhere also essentially double wrapped all of the communications with Exchange adding to the complexity.
MAPI/HTTP will generate a maximum of 2 current connections generating one long lived connection and an additional on-demand short-lived connection. This change will reduce the number of concurrent TCP connections established between the client and server. Gone are the twin RPC_DATA_IN and RPC_DATA_OUT connections required in the past for each RPC/HTTP session. MAPI/HTTP moves connectivity to a true HTTP request/response pattern and no longer requires two long-lived TCP connections to be open for each session between Outlook and Exchange. MAPI/HTTP removes the complexity of Outlook Anywhere’s dependency on the legacy RPC technology. It is the long term replacement for RPC over HTTP connectivity (commonly referred to as Outlook Anywhere). MAPI/HTTP was first delivered with Exchange 2013 SP1 and Outlook 2013 SP1 and begins gradually rolling out in Office 365 in May. MAPI over HTTP is a new transport used to connect Outlook and Exchange.
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We’ve seen a lot of interest about this new connection method and today we’ll give you a full explanation of what it is, what it provides, where it will take us in the future, and finally some tips of how and where to get started enabling this for your users. Among the many new features delivered in Exchange 2013 SP1 is a new method of connectivity to Outlook we refer to as MAPI over HTTP (or MAPI/HTTP for short).