The CAS server role in Exchange 2007 takes over some of the services previously done by a Front-End server in Exchange 2003.
Microsoft help describes the CAS as "Client Access Server This is the middle-tier server that hosts the client protocols, such as Post Office Protocol 3 (POP3), Internet Message Access Protocol 4 (IMAP4), Secure Hypertext Transfer Protocol (HTTPS), Outlook Anywhere, Availability service, and Autodiscover service. The Client Access Server also hosts Web services."
Some of these "services" are just new names for old tricks, some of them are new to us all. Within OWA, there is now the "Direct File Access" feature, Outlook anywhere replaces RPC over HTTP, Autodiscover configures Outlook 2007 and Mobile clients for us.
In this blog, and future blogs on the subject, I will discuss the new features provided, with an eye towards the best of the best. Our clients likely will be very interested in things like Direct File Access and the new features of ActiveSync.
The Client Access Role is similar to the role a Front-End server would play in an Exchange 2000/2003 organization. The Client Access server is the server that users connect to with their mail client, mobile device, or web browser. The Client Access server handles all connections whether they come from an application such as Outlook 2003 or 2007, Outlook Express, or any other MAPI, POP3 or IMAP4 client. The Client Access server also handles connections made from mobile devices such as a Windows Mobile 5 Smartphone, or any other device using Exchange ActiveSync. Exchange ActiveSync in Exchange 2007 supports all devices with PocketPC 2002/2003 and Windows Mobile 5.
This role also provides Outlook Web Access (OWA). OWA allows a user to access his or her mailbox from a web browser and have full access to all the information in the mailbox including task lists, calendar information, mail items and public folders. One of the hot new functions of OWA is Sharepoint and UNC access. Now users can access UNC shares (\servernameshare) and Sharepoint document libraries reducing the need for complex VPN configurations.
The CAS can also hold the OAB for download, if you can implement a public-folder free OAB solutiuon. It accomplishes this through the FDS (File Distribution Service). The OAB is generated and the copied to the CAS server on a 480 minute interval (default).
The process is as follows:
1. The OAB Generation Servers generates a Version 4 Offline Address List.
2. At the end of the generation the files will reside in the System Attendant Mailbox as this is the master location. The files are then copied from the System Attendant Mailbox to the local distribution share on the OAB Generation Server.
3. At this point the files can be downloaded from the OAB Generation Server by an Outlook client.
4. A notification is sent to the FDS service on the Client Access Server that there are files to be replicated.
5. The FDS will then start replication of the files to the remote distribution points where they may be.
When an Offline Address List has been successfully replicated you will see the below in the event log on the CAS.
Event Type: Information
Event Source: MSExchangeFDS
Event Category: FileReplication
Event ID: 1008
Date: XXX
Time: XXX
User: N/A
Computer: XXX
Description:
Process MSExchangeFDS.exe (PID=620). Offline Address Book data synchronization task has completed successfully. OAB name: "Test", Guid: 1fd83cb9-8887-4bbd-83f2-59c8a5ab29a4
The link http://www.microsoft.com/technet/prodtechnol/exchange/e2k7help/481ed6ca-674b-46d3-ae8a-375819bcc780.mspx?mfr=true has a great set of content on the individual tasks related to Mananging a CAS.
