Exchange 2013 Architectural changes

Exchange 2010 released with 5 server roles as like Exchange 2007. With the release of Exchange 2013 Preview, there are only two serer roles (Mailbox and the Client Access Server Roles). The 4 Internal Server Roles, Mailbox, Client Access, HUB and the UM servers are combined into two servers roles in Exchange 2013. The support or the option for the Edge Server Role in Exchange 2013 is not yet informed. It may or may not be released (Jan or Feb of 2013) in Exchange 2013 RTM



With Exchange Server 2010, the Server Roles are tightly coupled in the perspective of functionality and versioning (If client access server role is upgraded to new release, the mailbox server role has to be updated). With Exchange Server 2013 Mailbox and Client Access server roles, it is loosely coupled and there is no dependant on Functionality and versioning (If we upgrading the client access server roles, there is no dependence that the Mailbox server to be upgraded

Above diagram represents that, the Client Access Server Role in Exchange 2013 is responsible for Authentication, Proxy and redirection, reset of the component related to other server roles are moved to Mailbox Server Role.

Two Server roles in Exchange 2013


Two server roles with Mailbox and Client Access Server roles in Exchange Server 2013, doesn't mean that HUB and UM server roles are removed in Exchange 2013. Functionality of HUB and UM components are split between those 2 available server roles

Layer (4) Hardware Load Balancer is enough


With the architectural changes by instead of using Session affinity at the Client Access connection to NLB to CAS, exchange 2013 uses TCP affinity for access, which allows the use of Layer 4 hardware load balancer.

Each Server is treated as an individual Island


In Exchange Server 2010, EWS on one server can directly talk to store component on the other server and it makes the servers roles tightly coupled with each server roles , this is no longer the case wit Exchange 2013 and next releases. Which means the EWS on server can talk one with EWS on other server and it cannot be directly talk with other components. This removes the tightly coupled functionality in Exchange 2013

Let me know if you are having any doubts on the architectural changes in Exchange 2013.