For the Global Traffic Manager to operate effectively, you need to define
the different components that make up the relevant segments of your network. These components include physical components, such as data centers and servers, as well as logical components, such as wide IPs, addresses, and pools. By defining these components in the Global Traffic Manager, you essentially build a network map that the Global Traffic Manager can use to direct DNS traffic to the best available resource.
Once this basic configuration is complete, the Global Traffic Manager has
enough information available to direct DNS traffic, although obviously in a very limited sense. You can increase the systems capabilities by adding additional network components as appropriate.
Several components within the Global Traffic Managers configuration have
direct correlation to a physical location or device on the network. These components include:
Data centers are the top level of your physical network setup. You must
configure one data center for each physical location in your global network. The data center element of your configuration defines the servers (Global Traffic Managers, Local Traffic Managers, hosts, and routers) that reside at that location.
A data center can contain any type of server. For example, one data center
could contain a Global Traffic Manager and a host, while another could contain two Global Traffic Manager systems and eight Local Traffic Manager systems.
The data center servers that you define in the network setup include both
BIG-IP systems and third-party servers. One server component that you must define is the Global Traffic Manager itself, so it knows its place in the network map. You can also define Local Traffic Managers, and the virtual servers that these servers manage. Virtual servers are the ultimate destination for connection requests.
Each data center in your network has at least one connection to the Internet.
Within the Global Traffic Manager, these connections are identified as links. You can assign as many links to the appropriate data centers as needed. Configuring links is optional for the Global Traffic Manager, although they are very useful when determining resource availability.
Any server, excluding Global Traffic Managers and Link Controllers,
contains at least one virtual server. A virtual server
, in the context of the Global Traffic Manager, is a specific IP address and port number that points to a resource on the network. In the case of host servers, this IP address and port number likely point to the resource itself. With load balancing systems, such as the Local Traffic Manager, these virtual servers are often proxies that allow the load balancing server to manage the resource request across a multitude of resources.
In addition to the physical components of your network, the Global Traffic
Manager also handles DNS traffic over logical components. Logical components
consist of network elements that may not represent a physical location or device. These components include:
To communicate with the rest of your network, you must configure the
Global Traffic Manager so that it can correctly identify the resolution requests for which it is responsible. A listener is a resource that instructs the Global Traffic Manager to listen for requests destined to a specific IP address. In most installations, the listener you define for the Global Traffic Manager is the same as its IP address; however, there are many different ways you can configure listeners so that the Global Traffic Manager handles DNS traffic correctly.
One of the most common logical components you create in the Global
Traffic Manager is a wide IP. A wide IP
maps a domain name to a collection of pools, and it specifies the load balancing modes that the Global Traffic Manager uses to choose a select a pool.
When a local DNS server requests a connection to a specific domain name,
the wide IP definition specifies which pools of virtual servers are eligible to answer the request, and which load balancing modes to use in choosing a pool. The Global Traffic Manager then load balances the request across the virtual servers within that pool to resolve the request.
When you define the virtual servers to which the Global Traffic Manager
directs DNS traffic, you will want to combine those virtual servers into specific groups, or pools. You can then configure the Global Traffic Manager to direct traffic to a virtual server within a pool using a specific load balancing method.
One of the important aspects of pools that you must consider is that any
virtual server you add to that pool becomes a pool member. A pool member is a representation of a virtual server within a pool. This distinction is important because you can apply monitors, iRules, and other configuration options to a pool member, and then apply a different set of options to the same resource as a virtual server.
In situations where the Global Traffic Manager is configured with several
wide IPs, you can organize wide IPs that share responsibilities into a comprehensive whole, or distributed application. A distributed application
is a collection of one or more wide IPs. Through a distributed application, you can arrange dependencies based on the data centers, servers, and links that compose each wide IP. For example, if the New York data center goes offline, this information causes the wide IP and its corresponding distributed application to become unavailable. Consequently, the Global Traffic Manager does not send any resolution requests to any of these resources, until the entire application becomes available again.