Infoblox DNS Traffic Control (DTC) provides a load balancing solution by creating DNS responses based on DNS query source IP, server availability, and network topology. Through DTC, you can set up multiple global sites and configure supported objects and load balancing methods to direct DNS clients to the best available servers. For detailed information about how DNS Traffic Control handles DNS queries and responses, see DNS Traffic Control Querying Process below.
To use the DTC feature and bypass the standard DNS querying process, you must install the DNS Traffic Control license on designated Grid members. For information about license and admin requirements, see License Requirements and Admin Permissions. Members that are not authoritative for zones or members that do not have the DTC license installed will not process DNS queries through DTC. However, the appliance can process DNS queries through DNS Traffic Control for secondary servers in the Grid using the data replication method. 
DNS Traffic Control utilizes a load balancing mechanism to create DNS responses. It returns tailored DNS responses based on settings you configure for associated objects such as DTC servers, pools, and LBDNs. For more information about these objects, see Supported DNS Traffic Control Objects below and Managing DNS Traffic Control Objects. You can configure load balancing methods for pools and LBDNs based on the source IP address and other criteria. For more information, see Load Balancing Methods for DNS Traffic Control.
To ensure that DTC servers are reachable and can process DNS queries, you can configure health monitors that help you determine the availability of these servers. For more information, see Using DNS Traffic Control Health Monitors.
After you have set up DNS Traffic Control for specific DTC objects, you can monitor their status as described in the section Viewing DNS Traffic Control Objects. You can also view a visualization of the hierarchy of DNS Traffic Control objects that you configured. For more information, see Visualization for DNS Traffic Control Objects.
You can enable or disable logging for DNS Traffic Control load balancing and health monitors. The appliance logs this information to the syslog. For more information, see Setting DNS Logging Categories.
You can configure the DNS Traffic Control properties for the Grid and Grid members. For more information, see Configuring DNS Traffic Control Properties.

DNS Traffic Control Configuration Example

The DNS Traffic Control Example figure below illustrates the basic concept of DNS Traffic Control and how you can use it to direct DNS clients to the best available server using the Topology load balancing method. In the illustration, consider your company manages five data centers: California, Denver, New York, London, and Brussels. Each data center offers the same services and applications your users need. To optimize server utilization and minimize response time, you use DNS Traffic Control to provide DNS responses based on the source IP address and the geographic locations of your data centers. You define your data centers as DTC server objects, and then add them to a pool based on their locations. Data centers in California, Denver, and New York go into Pool USA while London and Brussels go into Pool EU. You also create a topology ruleset containing geography rules that is used when you configure Topology as the load balancing method for your LBDN and pools. To ensure that your data centers are available, you also configure health monitors so that your pools can check the health of its DTC servers.
In DNS Traffic Control, you complete the following to set up the above configuration:

1. Define a geography rule for the topology ruleset, as described in Configuring Topology Rules and Rulesets.

2. Configure each data center as a DTC server object, as described in Configuring DNS Traffic Control Servers.

3. Configure health monitors that NIOS will use to check the availability of DTC servers, as described in Using DNS Traffic Control Health Monitors.

4. Create two pools (USA and EU), which group your servers by geographical locations, configure health monitors that you created earlier, and then select Topology as the load balancing method. For information, see Configuring DNS Traffic Control Pools.

5. Define an LBDN and select Topology as the load balancing method and then associate it with a DNS zone. The appliance can then match the geography of the source IP addresses and direct the client to the best available server. For information, see Configuring DNS Traffic Control LBDNs.

DNS Traffic Control Example

 To achieve load balancing results for DNS Traffic Control, you can configure DTC objects in the following order:

1. Create DNS Traffic Control servers for each data center or server you want to manage. For information, see Configuring DNS Traffic Control Servers Configuring DNS Traffic Control Servers.

2. Optionally, if you want to monitor server health, configure health monitors and add them to your pools when you create them. For information, see Using DNS Traffic Control Health Monitors.

3. Configure any topology rulesets that will be used by DTC pools. For information, see Defining Topology Rulesets.

4. Configure DTC pools, as described in Configuring DNS Traffic Control Pools.

5. Configure any topology rulesets that will be used with LBDNs, as described in Configuring Topology Rules and Rulesets.

6. Configure DTC LBDNs, as described in Configuring DNS Traffic Control LBDNs.

DNS Traffic Control Querying Process

DNS Traffic Control handles a DNS query if the query name belongs to a zone for which the appliance is authoritative and matches an LBDN that is linked to the respective zone. Otherwise, the appliance processes DNS queries normally using the standard DNS query processing.
If you have configured persistence for DTC LBDN and the DTC cache contains a previous response for the same client, then DTC returns the cached response to the respective client. Otherwise, the DNS Traffic Control querying process first selects an LBDN, a pool, and then a specific server from that pool. A DNS record is synthesized from the address of the selected server and returns only DTC LBDN records to the client. Note that the configured DNS records are obscured by the DTC LBDN records. The obscured records are indicated by a strikethrough. For example, an obscured A record appears as A Record in Grid Manager.
When all the pools associated with the LBDNs are unavailable, the appliance returns DNS data for the zone. For information about how to configure availability and topology rules, see Configuring Topology Rules and Rulesets.
Following is a brief description of the DNS Traffic Control querying process:

1. The DNS Traffic Control querying process first checks an LBDN's DTC cache to verify if a response is available for the same client, same query and if the server in the cached response is online. If these conditions match, it returns the cached response to the client and refreshes the cache expiry time.

2. If the response is not available in the DNS Traffic Control cache, the DNS Traffic Control querying process occurs as follows:

   • Based on the FQDN in the request, the DNS Traffic Control querying process selects a matching LBDN based on its associated zone and pattern.

   • Based on the selected LBDN load balancing method, the DNS Traffic Control querying process selects an available pool. It does not select pools that are not available or do not have online servers associated with it. If pools are not available for the selected LBDN, the DNS Traffic Control querying process fails to determine the result.

   • After selecting a pool, the DNS Traffic Control querying process selects a server from the pool, based on the load balancing method that you have selected for the respective pool. The DNS Traffic Control querying process uses the preferred load balancing method of the pool by default and the alternate method only if the preferred method fails to return a result.

   • If the DNS Traffic Control querying process fails to determine a result, then the DNS server responds to the client with the matching DNS records configured for the respective zone. If matching DNS records are not configured, it returns an empty result. You can enable or disable the DTC to DNS fall through in the Grid DNS properties.

Supported DNS Traffic Control Objects

You can configure the following DNS Traffic Control objects in the Grid:

• Server: DNS Traffic Control synthesizes DNS records for the servers. For information about how to add and modify servers, see Configuring DNS Traffic Control Servers.

• Pool: A pool is a collection of servers that you can put together as possible responses to queries. For information about how to add and modify load balancing pools, see Configuring DNS Traffic Control Pools.

• LBDN: A DTC LBDN is a load balanced domain name object that is used by DNS Traffic Control to process DNS queries for load balanced resources. For more information about how to add and modify LBDN objects, see Configuring DNS Traffic Control LBDNs.