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.
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. For more information on designing large and complex Exchange Server implementations, see Chapter 4.
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.