3. Determining Exchange Server 2013 Placement
Previous
versions of Exchange Server essentially forced many organizations into
deploying servers in sites with relatively few users. With the concept
of site consolidation in more recent versions of Exchange, smaller
numbers of Exchange servers can service clients in multiple locations,
even if they are separated by slow WAN links. For small and
medium-sized organizations, this essentially means that fewer servers
are required. In addition, Exchange Server 2013 introduces new
consolidated server role concepts, which should be understood so that
the right server can be deployed in the right location.
3.1 Understanding Exchange Server 2013 Server Roles
Exchange
Server 2013 firmed up the server role concept outlined with Exchange
Server 2007 and 2010 and simplified them. Before Exchange Server 2007,
server functionality was based on how a server was used rather than the
components that were installed, such as referring to an Exchange server
as a front-end, bridgehead, or back-end server. In reality, there was
no official terminology that was used for Exchange server roles; these
terms evolved through common use. Exchange Server 2007 and 2010
introduced new roles that were very specific, but Microsoft found that
most clients were seldom deploying all of those roles on separate
servers and were combining them together, especially the Hub Transport
and Client Access Server roles.
Microsoft
has combined server roles in Exchange Server 2013, but more for
technical rather than usage reasons. The server roles included in
Exchange Server 2013 include the following:
• Client Access Server—The
CAS role allows for client connections via nonstandard methods such as
OWA, Exchange ActiveSync, Post Office Protocol 3 (POP3), and Internet
Message Access Protocol (IMAP). Exchange Server 2013 also forces MAPI
traffic and effectively all client traffic through the CAS layer. CAS
servers in Exchange Server 2013 are also completely stateless, so they
can be load-balanced for redundancy purposes using any number of
load-balancing technologies, including simple solutions such as DNS
Round Robin (though this is not recommended). As with the other server
roles, the CAS role can coexist with other roles for smaller
organizations with a single server, for example.
• Mailbox server—The
Mailbox server role is intuitive; it acts as the storehouse for mail
data in users’ mailboxes and down-level public folders if required. All
connections to the mailbox servers are proxied through the CAS servers.
The Mailbox server role also handles the previous Hub Transport and
Unified Messaging capabilities that were separate roles in the past.
• Edge Transport server—The
Edge Transport server is unchanged from Exchange Server 2010, providing
a gateway for SMTP traffic for message hygiene and recipient filtering.
Note that the RTM version of Exchange Server 2013 does not support a
2013 server being installed with the Edge Transport role, though it
does support existing Exchange Server 2010 Edge Transport servers. This
is expected to be remedied in later releases of Exchange Server.
The
first two roles can be installed on a single server or on multiple
servers. For smaller organizations, a single server holding all
Exchange Server roles is sufficient. For larger organizations, a more
complex configuration might be required.
3.2 Understanding Environment Sizing Considerations
In
some cases with very small organizations, the number of users is small
enough to warrant the installation of all AD DS and Exchange Server
2013 components on a single server. This scenario is possible, as long
as all necessary components—DNS, a global catalog domain controller,
and Exchange Server 2013—are installed on the same hardware. In
general, however, it is best and highly recommended to separate AD DS
and Exchange Server onto separate servers wherever possible.
Identifying Client Access Points
At
its core, Exchange Server 2013 essentially acts as a storehouse for
mailbox data. Access to the mail within the mailboxes can take place
through multiple means, some of which might be required by specific
services or applications in the environment. A good understanding of
what these services are and if and how your design should support them
is warranted.
Outlining Full Outlook Client Access
The
“heavy” client of Outlook is in its latest 2013 version and has gone
through a significant number of changes, both to the look and feel of
the application and to the back-end mail functionality. The look and
feel has been streamlined based on Microsoft research and customer
feedback. The latest Outlook client, Outlook 2013, uses the Office
Ribbon introduced with Office 2007 to improve the client experience.
Outlook connects to Exchange CAS servers, improving the scalability of
the environment.
In addition to MAPI
compression, Outlook 2013 expands upon Outlook’s ability to run in
cached mode, which automatically detects slow connections between
client and server and adjusts Outlook functionality to match the speed
of the link. When a slow link is detected, Outlook can be configured to
download only email header information. When emails are opened, the
entire email is downloaded, including attachments if necessary. This
drastically reduces the amount of bits across the wire that is sent
because only those emails that are required are sent across the
connection.
The Outlook client is the most
effective and full-functioning client for users who are physically
located close to an Exchange server. With the enhancements in cached
mode functionality, however, Outlook can also be effectively used in
remote locations. When making the decision about which client to deploy
as part of a design, you should keep these concepts in mind.
Accessing Exchange Server with OWA
The
OWA client in Exchange Server 2013 has been enhanced and optimized for
performance and usability. There is now less difference between the
full-functioning client and OWA. The most recent
improvement is the ability to take OWA content offline and work on a
cached version of a mailbox from an offline browser. Also new is
updated support for non-Microsoft browsers, such as Firefox, Safari,
and Chrome.
Using Exchange ActiveSync (EAS)
Exchange
ActiveSync (EAS) support in Exchange Server 2013 allows a mobile
client, such as an iPhone, Android phone, iPad, Android tablet, or
Windows Phone device, to synchronize with the Exchange server, allowing
for access to email from a handheld device.
Understanding the SMTP
The
SMTP is the standard protocol for Internet email delivery. SMTP is
built in to Exchange servers and is used by Exchange Server systems for
relaying mail messages from one system to another, similar to the way
that mail is relayed across SMTP servers on the Internet.
By
default, Exchange Server 2013 uses DNS to route messages destined for
the Internet out of the Exchange Server topology. If, however, a user
wants to forward messages to a smart host before they are transmitted
to the Internet, a Send connector can be so configured.
Using Outlook Anywhere (Previously Known as RPC over HTTP)
One
very effective and improved client access method to Exchange Server
2013 is known as Outlook Anywhere. This technology was previously
referred to as RPC over HTTP(S). This technology enables standard
Outlook 2013/2010/2007 access using a protocol that firewalls typically
allow to pass. The Outlook client encapsulates Outlook RPC packets into
HTTP or HTTPS packets and sends them across standard web ports (80 and
443), where they are then extracted by the Exchange Server 2013 system.
Outlook Anywhere also obviates the need for a virtual private network
(VPN) connection for Outlook connectivity to the Exchange server.
