GTM Terminology

Defining Global Traffic Manager components

For the BIG-IP® Global Traffic Manager system to operate effectively, you need to define the components that make up the 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, you essentially build a network map that the Global Traffic Manager can use to direct Domain Name System (DNS) traffic to the best available resource.

The most basic configuration of the Global Traffic Manager includes:

·        A listener that is a specific virtual server that identifies network traffic for global traffic management

·        A data center that contains at least one server

·        A server that contains at least one resource, or virtual server

Once this basic configuration is complete, the Global Traffic Manager has enough information available to begin directing DNS traffic. You can increase the systems capabilities by adding additional network components as appropriate.

The components that you define in the Global Traffic Manager can be divided into two basic categories:

·        Physical components

·        Logical components

Introducing physical network components

Several components that you can configure on the Global Traffic Manager system have a direct correlation to a physical location or device on the network. These components include:

·        Data centers

·        Servers

·        Links

·        Virtual servers

Data centers
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. When you create a data center in the Global Traffic Manager, you define the servers (Global Traffic Manager systems, Local Traffic Manager systems, Link Controller systems, hosts, and routers) that reside at that location.
A data center can contain any type of server. For example, one data center can contain a Global Traffic Manager and a host, while another might contain two Global Traffic Manager systems and eight Local Traffic Manager systems.

Important: The data center name is limited to 63 characters.

 
Servers

A server is a physical device on which you can configure one or more virtual servers. The servers that you define for the Global Traffic Manager to manage can include both BIG-IP systems and third-party servers, for example, Local Traffic Manager systems and Windows® 2000 Servers.

One server that you must define is the Global Traffic Manager. This places the system on the network map. You can also define Local Traffic Manager systems, and the virtual servers that these servers manage.  

Important: The server name is limited to 63 characters.

Virtual servers

Servers, excluding Global Traffic Manager systems and Link Controller systems, contain at least one virtual server. A virtual server, in the context of the Global Traffic Manager, is a combination of an IP address and a port number that points to a resource that provides access to an application or data source on your 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. Virtual servers are the ultimate destination for connection requests.

Important: The virtual server name is limited to 63 characters.

 

Introducing logical network components

In addition to the physical components of your network, the Global Traffic Manager also handles DNS traffic over logical components. Logical network components consist of network elements that may not represent a physical location or device. These components include:

·        Listeners

·        Pools

·        Wide IPs

·        Distributed applications
 

Listeners

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 an object that monitors the network for DNS queries, and thus is critical for global traffic management. The listener instructs the system to monitor the network traffic destined for a specific IP address.

In most installations, when you define a listener for the Global Traffic Manager, you use the IP address of the Global Traffic Manager; however, there are many different ways you can configure listeners so that the system handles DNS traffic correctly.

Pools

A pool is a collection of virtual servers that can reside on multiple network servers. When you define the virtual servers to which the Global Traffic Manager directs DNS traffic, you combine those virtual servers into pools. You can then configure the Global Traffic Manager to direct traffic to a specific virtual server within a pool, using a specific load balancing method.

You can apply a different set of options to the same resources as a virtual server. When you add a virtual server to a pool, it becomes a pool member to which you can apply monitors, iRules®, and other configuration options.

Important: The pool name is limited to 63 characters.

    

Wide IPs

One of the most common logical components you create in the Global Traffic Manager is a wide IP. A wide IP maps a fully-qualified domain name to one or more pools of virtual servers that host the domains content.

When an local DNS 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.