Problem : The CAS server role is equated with the Exchange 2000/2003 front-end
server, but it works quite differently and seems to have more features
involved to administrate. What does the CAS role do and how do you
administer its many features?
Solution : It’s true that the front-end servers of Exchange 2000/2003 are similar
in nature to the CAS server role in that all non-MAPI connections are
made through the CAS. However, more processing power was given to the
CAS server than previously with front-end servers to offload some of the
processing load placed upon the mailbox servers.
The CAS server is the first one you install if you
are breaking up your server installations into roles. You need to ensure
you have a CAS server in every site that has a mailbox server because
the two work hand in hand with each other.
Administration can be
performed through the Exchange Management Console (EMC) and the Exchange
Management Shell (EMS), as you will soon see. However, because of the
extensive use of Internet Information Server (IIS), you might find
yourself using the IIS Manager to handle certain aspects of CAS as well,
especially when working with SSL certificates for more secure
connections.
The primary features of the Client Access Server include the following:
Outlook Web Access (OWA)—
Provides your users with the browser-based connection to their
mailboxes. If configured to allow incoming connections from the outside,
users can check their email from home using OWA.
Note
One of the problems
for your users using pre-Outlook 2007 software is that some of the
mailbox features provided by Exchange (such as the new Out of Office
changes) are not available to them. However, one of the benefits of the
CAS server is that they can enable those features through an OWA
connection because the CAS server provides the latest flavor of OWA, and
therefore, it provides the latest features, too.
Exchange ActiveSync (EAS)—
Provides access to users with mobile devices. This includes all devices
that have the ActiveSync protocol (this means BlackBerrys and the
earlier iPhones will not work). You need to confirm that your devices
can make the Exchange ActiveSync connection. With Exchange Exchange
2007 SP1, some stronger policy settings are in place, so if you haven’t
purchased the mobile devices for your users just yet, you might want
the latest version of Mobile. ActiveSync policy settings are controlled
at the Organizational Configuration work center level.
Outlook Anywhere—
Previously called RPC over HTTP in Exchange 2003, this enables users to
use Outlook from a home or laptop connection outside the company, but
with the level of security you would expect if you were sitting at your
desk. This is done without a VPN tunnel. Outlook Anywhere instead
encapsulates the RPC packets inside of HTTP packets, which can go over
the Internet to your Exchange server, which then peels off the HTTP
packet. (Note: Only Outlook 2003 and Outlook 2007 are supported for
these types of connections.)
POP3 and IMAP4—
These protocols are still heavily used to work with your Outlook
Express clients, Mozilla Thunderbird clients, and Windows Mail clients.
With these protocols, not many features are supported, but they do
provide the basics and sometimes that is all you need.
Autodiscover Service—
This provides users with Outlook 2007 the capability to locate and
connect automatically with the Exchange server that houses their
mailbox.
Availability Service—
This used to be called free/busy data, and it is essentially for
Outlook 2007 clients or those using OWA on an Exchange 2007 system. The
availability service retrieves live free/busy information for mailboxes
from Public Folders, views attendee working hours, and shows meeting
time suggestions. This used to be part of the Public Folder structure,
but now the CAS server handles these loose ends.
IIS Integration
IIS is an integral part to
the CAS role. This is easy to see if you simply open the IIS Manager
from within Administrative Tools and note that the default website
includes many of the features we have discussed through virtual folders,
as you can see in Figure 1.
Table 7.1 provides a list of virtual folders and their purpose:
Table 7.1. IIS Virtual Folders for Exchange 2007
| Virtual Folder | Purpose |
|---|
| Autodiscover | Handles auto-provisioning for clients |
| EWS | Exchange Web Services |
| Exchweb | For OWA clients that connect to legacy mailboxes (Exchange 2000/2003) |
| Exchange | For OWA clients that connect to legacy mailboxes (Exchange 2000/2003) |
| Microsoft-Server-ActiveSync | Handles mobile connections from supported devices |
| OAB | Provides Outlook 2007 Offline Address Book distribution |
| OWA | For OWA connections to Exchange 2007 |
| Public | For OWA access to Public Folders |
| UnifiedMessaging | For access to some UM information |
Of course, knowing what the CAS server does is half the battle. The next part is managing it all.
