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Archived Manual Chapter: 3-DNS Admin Guide, v4.5:Configuring a Globally-Distributed Network
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6

Configuring a Globally-Distributed Network


Understanding a globally-distributed network

When you are familiar with your traffic patterns and are expanding into a global marketplace, you can use the 3-DNS Controller to distribute requests in an efficient and seamless manner using Topology load balancing. When you use Topology load balancing, the 3-DNS Controller compares the location information derived from the DNS query message to the topology records in the topology statement. The system then distributes the request according to the topology record that best matches the location information.

Figure 6.1 Topology load balancing in a globally-distributed network

Using Topology load balancing

The Topology load balancing mode is optimal for organizations that have data centers in more than one country or on more than one continent. The 3-DNS Controller enables topology-based load balancing by resolving DNS requests to the geographically closest server. The traditional topology load balancing mode, which provides basic topology mapping functionality, uses IP subnets of virtual servers and known LDNS servers. This can result in a very large list of IP subnets to manage when you want to map a specific geographic region.

To simplify topology load balancing, the 3-DNS Controller contains a classifier that maps IP addresses to geographic locations. With this classifier, the 3-DNS Controller resolves DNS requests to the geographically closest LDNS server at either the country or the continent level. The system then load balances the request to virtual servers in IP subnets, wide IP pools, or data centers.

You can set up Topology load balancing either between wide IP pools or within a wide IP pool. For the example in Figure 6.1 , we configure Topology load balancing between wide IP pools.

Setting up a globally-distributed network configuration

By going through the following setup tasks, you can configure the 3-DNS Controller to process requests, using Topology, in a globally-distributed network. This configuration is based on the following assumptions:

  • You have more than one data center.

  • You have a 3-DNS Controller in each data center.

  • You have BIG-IP systems, or other load balancing hosts, in the data centers.

  • You want to load balance requests to the geographically closest virtual server.

If you use a CDN for some or all of your content delivery, please refer to Chapter 7, Configuring a Content Delivery Network , to set up this configuration.

The following sections describe, in order, the specific configuration tasks you perform to set up a globally-distributed network. Please review the tasks before you actually perform them, so that you are familiar with the process.

     

Adding data centers to the globally-distributed network configuration

The first task you perform is to add your data centers to the 3-DNS configuration.

To add data centers using the Configuration utility
  1. In the navigation pane, click Data Centers.
    The Data Centers screen opens.

  2. Click Add Data Center on the toolbar.
    The Add Data Centers screen opens.

  3. Add your data center information. For information and help on the specific settings on this screen, click Help on the toolbar.

  4. Repeat the previous steps to add all of your data centers to the configuration.

    Configuration notes

For the globally-distributed network configuration shown in Figure 6.1 , we have added two data centers labeled
West Coast - DC and Europe - DC.

     

Adding 3-DNS Controllers to the globally-distributed network configuration

Once you have added all of your data centers to the 3-DNS configuration, you are ready to notify the 3-DNS Controller that you are configuring about the 3-DNS Controllers in your network, including the 3-DNS Controller you are configuring.

Note


Please note that when you are working with more than one 3-DNS Controller, you create your entire configuration on one system and then add the second system using the 3dns_add script. The 3dns_add script copies the entire configuration from the first (or existing) system onto the second (new) system, and synchronizes all of the settings. For details on configuring additional 3-DNS Controllers in existing networks, using the 3dns_add script, see Chapter 10, Adding a 3-DNS Controller to an Existing Network .

 

To add 3-DNS Controllers using the Configuration utility
  1. In the navigation pane, expand the Servers item, then click 3-DNS.
    The 3-DNS List screen opens.

  2. Click Add 3-DNS on the toolbar.
    The Add New 3-DNS screen opens.

    For information and help on the specific settings on any screen in the Configuration utility, click Help on the toolbar.

  3. Add the 3-DNS Controller information.

  4. Repeat the previous steps to add any additional 3-DNS Controllers to the configuration.

    Configuration notes

For the globally-distributed network configuration shown in Figure 6.1 , we have a 3-DNS Controller in each data center, West Coast - DC and Europe - DC. The system we are configuring is labeled 3-DNS_01, and is in the West Coast - DC data center. The additional system is in the Europe - DC data center, and is labeled 3-DNS_02.

     

Adding BIG-IP systems to the globally-distributed network configuration

Now you are ready to let the 3-DNS Controller know about any BIG-IP systems, or other servers, that you have in your network. Remember that the 3-DNS Controller load balances requests to the virtual servers managed by the BIG-IP systems, EDGE-FX systems, or host servers in your network. In this example configuration, we set up BIG-IP systems. For information on adding EDGE-FX systems or host servers to your network, please refer to Setting up servers .

The following steps outline how to add BIG-IP systems to your configuration.

To add BIG-IP systems using the Configuration utility
  1. In the navigation pane, expand the Servers item, then click BIG-IP.
    The BIG-IP List screen opens.

  2. Click Add BIG-IP on the toolbar.
    The Add New BIG-IP screen opens.

  3. Enter the BIG-IP system information, and click Next.

  4. In the Data Centers screen, select the data center where the BIG-IP system is located, and click Next.

  5. In the Configure Virtual Server screen, specify the information for the first virtual server managed by the BIG-IP system, and click Finish.

  6. To add more virtual servers to your configuration, click Add Virtual Server on the toolbar.

  7. Once you have configured your first BIG-IP system, you can repeat the previous steps to add all of the additional BIG-IP systems to the 3-DNS configuration.

Tip


For information and help on the specific settings on any screen in the Configuration utility, click Help on the toolbar.

 

Adding wide IPs to the globally-distributed network configuration

Once you have added all the physical elements to your 3-DNS configuration, you can begin configuring wide IPs and pools for load balancing. Before you start adding wide IPs, verify that you have configured all the virtual servers you need for load balancing. In order to optimize the Topology load balancing mode, you need to properly configure the wide IPs and pools, as follows.

To add a wide IP and pool using the Configuration utility
  1. In the navigation pane, click Wide IPs.
    The Wide IP List screen opens.

  2. Click Add Wide IP on the toolbar.
    The Add a New Wide IP screen opens.

  3. Specify the wide IP address, name, and port information.

  4. For the Pool LB Mode, select Topology, and click Next.
    The Configure Load Balancing for New Pool screen opens.

  5. Specify the pool name and click Next.
    The Select Virtual Servers screen opens.

  6. In the Select Virtual Servers screen, check the virtual servers among which you want the 3-DNS Controller to load balance DNS requests, and click Finish.
    The 3-DNS Controller adds the wide IP and settings to the configuration.

  7. If you want to create additional pools for load balancing, click the name of the wide IP you just created in the Wide IPs List screen. When the Modify Wide IP screen opens, click Add Pool on the toolbar.

  8. Repeat the previous procedure to add as many wide IPs and pools as are required for your network.

Tip


For information and help on the specific settings on any screen in the Configuration utility, click Help on the toolbar.

 

Configuration notes

For the globally-distributed network configuration shown in Figure 6.1 , we have set up one wide IP, labeled www.siterequest.com, and we added two pools to the wide IP, americas_pool and europe_pool. When you configure the topology records, as explained in the next section, we designate these two pools to process the load balancing requests based on the geographic location of the local DNS server or client making the request.

Configuring topology records for the globally-distributed network configuration

You must configure topology records before the 3-DNS Controller can use the Topology load balancing mode. The Topology load balancing mode distributes connections after evaluating and scoring the topology records in the topology statement. If you have no topology records in the topology statement, or if the scores returned for two or more records are equal, the 3-DNS Controller load balances the virtual servers using the Random load balancing mode.

The following procedure explains how to configure topology records in the Configuration utility. For more information on how the 3-DNS Controller uses the topology records, and how to configure topology in the wideip.conf file, please review Chapter 3, Topology , in the 3-DNS Reference Guide.

To configure topology records using the Configuration utility
  1. In the navigation pane, click Topology.
    The Manage Topology Records screen opens.

  2. Specify the settings for the topology records.

  3. Click Add.

Tip


For information and help on the specific settings on any screen in the Configuration utility, click Help on the toolbar.

 

For the globally-distributed network configuration shown in Figure 6.1 , we added topology records, as shown in Figure 6.2 .

Figure 6.2 Example of a topology statement


//server ldns score
pool.americas_pool cont.North America 100
pool.europe_pool !cont.North America 100
 

 

With this topology statement, in our example configuration, queries to resolve www.siterequest.com from local DNS servers somewhere in North America get responses from virtual servers in the pool americas_pool. All other queries to resolve www.siterequest.com get responses from virtual servers in the pool europe_pool.

Additional configuration settings and tools

The following optional settings and tools can help you refine your load balancing configuration.

Setting limits thresholds

When you set limits thresholds for availability, the 3-DNS Controller can detect when a managed server or virtual server is low on system resources, and can redirect the traffic to another virtual server. Setting limits helps eliminate any negative impact on a virtual server's performance of service tasks that may be time critical, require high bandwidth, or put high demand on system resources. The system resources for which you can set limits are:

  • CPU

  • Disk

  • Memory

  • Packet rate

  • Kilobytes per second (throughput rate)

  • Current connections

To set limits thresholds for BIG-IP systems
  1. In the navigation pane, expand the Servers item, and click BIG-IP.

  2. In the Limits Settings column of the BIG-IP system for which you want to set limit thresholds, click the Configure Limits button .
    The Modify Server Limits Settings screen opens.

  3. Check the metrics for which you want to set limits, and type values based on your network resources. For more information and help on this screen, click Help on the toolbar.

    You can also set limits thresholds on virtual server resources. Please note that if a server meets or exceeds its limits settings, both the server and the virtual servers it manages are marked as unavailable for load balancing. You can quickly review the availability of any of your servers or virtual servers in the Statistics screens in the Configuration utility.

Other resources

In addition to setting limits, the 3-DNS Controller provides the following resources to help you maintain your configuration and monitor system performance.

Monitoring system performance

The Statistics screens in the Configuration utility provide a great deal of information about the 3-DNS Controller. For example, you can monitor server performance and view limits settings in the Server and Virtual Server Metrics statistics screen. For more information, see the 3-DNS Reference Guide, Chapter 6, Administration and Monitoring .

Viewing your configuration

The Network Map provides an interactive map of your configuration. You can see how the data centers, servers, and virtual servers you configured are related to the wide IPs and pools you created for load balancing. You can also make real-time changes to your configuration from the Network Map. For more information, see the 3-DNS Reference Guide, Chapter 6, Administration and Monitoring

To view the Network Map
  1. In the navigation pane, click Network Map.
    The Network Map screen opens.

  2. To open the Network Map in a separate popup screen, click Undock. (This is useful if you are making a series of changes and want to see how it affects your configuration.)



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