Load Balancing CAS Services

This section provides step-by-step instructions on how to configure the LoadMaster to load balance the various services of Microsoft Exchange 2010.

Each service handled by the CAS role is briefly described below:

Outlook Web App: Outlook Web App (OWA) is enabled by default when you install the Client Access server role. OWA lets you access your mailbox from a web browser. In previous versions of Exchange, a specific version of Internet Explorer was required in order to get the OWA premium experience. With Exchange 2010, you can get the premium experience with Microsoft Internet Explorer, Mozilla Firefox and Apple Safari.

Control Panel: The Exchange Control Panel (ECP) is enabled by default when you install the Client Access server role. ECP is a new web module that lets an end-user or administrator manage the miscellaneous settings or perform other tasks for a mailbox from a web browser. It replaces the old OWA options page included with the previous version of Exchange Server.

Outlook Anywhere: Outlook Anywhere (OA), formerly known as RPC over HTTP, lets clients that use Microsoft Office Outlook 2010, Outlook 2007, or Outlook 2003 connect to their servers from outside the corporate network or over the Internet using the RPC over HTTP Windows networking component. The Windows RPC over HTTP Proxy component, which Outlook Anywhere clients use to connect, wraps RPCs with an HTTP layer. This allows traffic to traverse network firewalls without requiring RPC ports to be opened. In Exchange 2010, as in 2007, it's easy to deploy and manage this feature. To deploy Outlook Anywhere (OA) in your Exchange 2010 messaging environment, you should enable OA on all Internet-facing CASs using the “Enable Outlook Anywhere wizard” in the Management Console or the “Enable-OutlookAnywhere” cmdlet. In addition, you must set the external URLs for ECP, EWS and OAB unless only public folders are used for distributing the Offline Address Book (OAB).

ActiveSync: Exchange ActiveSync (EAS) is enabled by default when you install the CAS role. ECP lets you synchronize a mobile phone with your Exchange 2010 mailbox. EAS is a Microsoft synchronization protocol that's optimized to work together with high-latency and low-bandwidth networks. The protocol, based on HTTP and XML, lets mobile phones access an organization's information on a server that's running Microsoft. EAS enables mobile phone users to access their e-mail, calendar, contacts, and tasks and to continue to be able to access this information while they are working offline.

Offline Address Book: The Offline Address Book (OAB) is created by default when you install the mailbox server role. OAB is a copy of one or more address lists that's been downloaded so that an Outlook user can access the information it contains while disconnected from the server. Administrators can choose which address lists are made available to users who work offline, and they can also configure the method by which the OAB is distributed (web-based distribution or public folder distribution).

Web Services: The Exchange Web Services (EWS) is enabled by default when you install the CAS role. EWS is a web services Application Programming Interface (API) that can be used by 3^rd party applications to access mailbox data. It is also used by various Microsoft applications and devices for integration with Exchange.

Autodiscover Service: The Autodiscover Service (AS) is enabled by default when you install the CAS role. AS is a service that makes it easier to configure Outlook 2007 or Outlook 2010 and EAS-based mobile devices that support this service. AS cannot be used with earlier versions of Outlook, including Outlook 2003.

RPC Client Access Service: The RPC Client Access (RPC CA) service is enabled by default when the Exchange 2010 Client Access Server role is installed. The RPC CA service handles the Outlook MAPI connections. The change in Exchange 2010 to move all processing to the CAS was implemented to provide all data access through a single, common path of the CAS. This change improves consistency for applying business logic to clients, and provides a better client experience when failover occurs. This change also allows a higher number of concurrent connections per server and a higher number of mailboxes per server. In addition to moving processing of incoming Outlook connections to the CAS, in Exchange 2010, directory access is also handled by the CAS.

Address Book Service: The Exchange Address Book (EAB) service is enabled by default when you install the Exchange 2010 CAS role. The EAB service handles directory access requests from Outlook clients.

Post Office Protocol: Post Office Protocol (POP) is disabled by default when you install the Exchange 2010 CAS role. POP was designed to support offline mail processing. With POP3, e-mail messages are removed from the server and stored on the local POP3 client, unless the client has been set to leave mail on the server. This puts the data management and security responsibility in the hands of the user. POP3 does not offer advanced collaboration features such as calendaring, contacts, and tasks.

Internet Message Access Protocol: Internet Message Access Protocol (IMAP) is disabled by default when you install the Exchange 2010 CAS role. IMAP offers offline and online access, but like POP3, IMAP4 does not offer advanced collaboration features such as calendaring, contacts, and tasks.