Welcome to the 3DNS® Controller Administrator Guide. This guide describes how to set up the 3DNS Controller hardware and how to set up your network and load balancing configurations, as well as other 3DNS Controller features. The Administrator guide also includes the software specifications for the 3DNS Controller platform, and it offers some sample configurations that can help you in planning your own configuration.
The 3DNS Controller is a network appliance that manages and balances traffic over global networks. The 3DNS Controller manages network traffic patterns using load balancing algorithms, topology-based routing, and production rules that control and distribute traffic according to specific policies. The system is highly configurable, and its web-based and command line configuration utilities allow for easy system set up and monitoring.
The 3DNS Controller provides a variety of features that meet special customer needs including:
The 3DNS Controller supports both standard DNS protocol and the F5 iQuery protocol (a protocol used for collecting dynamic load balancing information). The 3DNS Controller also supports administrative protocols, such as Simple Network Management Protocol (SNMP), and Simple Mail Transfer Protocol (SMTP) (outbound only), for performance monitoring and notification of system events. For administrative purposes, you can use the F-Secure SSH client (distributed only in the US), which provides a secure shell connection, rsh, Telnet, and FTP. The F5 Configuration utility supports secure connections via SSL (distributed only in the US), as well as standard HTTP connections.
The 3DNS Controller's SNMP agent allows you to monitor status and current traffic flow using popular network management tools, including the F5 Configuration utility. The SNMP agent provides detailed data such as current connections being handled for each virtual server.
The 3DNS Controller offers a variety of security features that can help prevent hostile attacks on your site or equipment.
The 3DNS Controller is a highly scalable and versatile solution. You can configure the 3DNS Controller to manage up to several hundred domain names, including full support of domain name aliases. The 3DNS Controller supports a variety of media options, including Fast Ethernet, Gigabit Ethernet, and FDDI, and also supports multiple network interface cards that can provide redundant or alternate paths to the network.
The 3DNS Controller provides the following web-based and command line administrative tools that make for easy set up and configuration.
The First-Time Boot utility is a wizard that walks you through the initial system set up. The utility helps you quickly define basic system settings, such as a root password and the IP addresses for the interfaces that connect the 3DNS Controller to the network. The First-Time Boot utility also helps you configure access to the 3DNS web server, which hosts the web-based F5 Configuration utility, as well as the NameSurfer application that you can use for DNS zone file management.
The F5 Configuration utility is a web-based application that you use to configure and monitor the 3DNS Controller. Using the F5 Configuration utility, you can define the load balancing configuration, along with the network set up, including data centers, sync groups, and servers used for load balancing and path probing. In addition, you can configure advanced features such as topology settings, IP filters, and the SNMP agent. The F5 Configuration utility also monitors network traffic, current connections, load balancing statistics, and the operating system itself.
The 3DNS web server, which hosts the F5 Configuration utility, provides convenient access to downloads such as the SNMP MIB and documentation for third-party applications such as NameSurfer.
The NameSurferTM application is a third-party application, produced by Data Fellows, that automatically configures DNS zone files associated with domains handled by the 3DNS Controller. You can use NameSurfer to configure and maintain additional DNS zone files on 3DNS Controllers that run as master DNS servers. The F5 Configuration utility provides direct access to the NameSurfer application, as well as the corresponding documentation for the application.
The 3DNS Maintenance menu is a command line utility that executes scripts which assist you in configuration and administrative tasks, such as installing the latest version of the big3d agent on all your systems, or editing the load balancing configuration files. You can use the 3DNS Maintenance menu directly on the 3DNS Controller, or you can use the menu when connected to the controller via a remote shell, such as the SSH client (US only), or a standard rsh client.
The F5 Configuration utility, which provides web-based access to the 3DNS Controller system configuration and features, supports the following browser versions:
The 3DNS Controller sync group feature allows you to automatically synchronize configurations from one 3DNS Controller to the other 3DNS Controllers in the network, allowing for simplified administrative management. The synchronization feature offers a high degree of administrative control. For example, you can set the controller to synchronize a specific configuration file set, and you can also set which 3DNS Controllers in the network receive the synchronized information and which ones do not.
The 3DNS Controller platform includes a big3d agent, which is an integral part of 3DNS Controller load balancing. The big3d agent continually monitors the availability of the servers that the 3DNS Controller load balances. It also monitors the integrity of the network paths between the servers that host the domain and the various client local DNS servers looking to connect to the domain. The big3d agent runs on 3DNS Controllers and BIG/ip Controllers distributed in various locations in your network. Each big3d agent broadcasts its collected data to all of the 3DNS Controllers in your network, ensuring that all 3DNS Controllers work with the latest information.
The big3d agent offers a variety of configuration options that allow you to choose the types of data collection methods you want to use. For example, you can configure the big3d agent to track the number of hops along a given network path, and you can also set the big3d agent to collect host server performance information using the SNMP protocol.
A redundant system is essentially a pair of 3DNS Controller units, one operating as an active unit responding to DNS queries, and one operating as a standby unit. If the active unit fails, the standby unit takes over and begins to respond to DNS queries while the other controller reboots and becomes a standby unit.
The 3DNS Controller actually supports two methods of checking status of the peer system:
Note: In a network-based fail-over configuration, the standby 3DNS Controller immediately takes over if the active unit fails. If a client had queried the failed controller, and not received an answer, it automatically re-issues the request (after 5 seconds) and the standby unit, functioning as the active controller, responds.
The 3DNS Controller supports easy configuration of the BSD operating system method of IP packet filtering. In the F5 Configuration utility, you can configure individual IP packet filters, which can control both in-bound and out-bound network traffic. For example, you can specify a single IP address, or a range of IP addresses, from which the 3DNS Controller either accepts or denies network traffic. You can also specify one or more IP addresses to which you specifically want to allow or prevent out-bound connections.
The 3DNS Controller offers several different load balancing modes, including static modes that base load balancing on a pre-defined distribution pattern, and dynamic modes that base load balancing on current network information such as the round trip time between a requesting client and a web server.
Static load balancing distributes connections based on pre-defined distribution patterns, and does not take current server or network performance into account. The 3DNS Controller supports the following static load balancing modes:
Dynamic load balancing bases connection distribution on current server and network performance information gathered by the big3d agent. The different dynamic load balancing modes incorporate different performance factors.
This section provides a brief overview of how 3DNS Controllers work within a global network and how they interact with other BIG/ip Controllers and host machines in the network. The section also illustrates how the 3DNS Controller works with the big3d agents that run in various locations in the network, as well as the local DNS servers that make DNS requests on behalf of clients connecting to the Internet.
The following sample configuration shows 3DNS Controllers that load balance connections for a sample Internet domain named domain.com.
3DNS Controllers sit in specific data centers in your network and they work in conjunction with BIG/ip Controllers and with generic host servers that also sit in your network data centers. All 3DNS Controllers in the network can receive and respond to DNS resolution requests from the local DNS servers that clients use to connect to the domain.
Figure 1.1 illustrates the layout of the 3DNS Controllers, BIG/ip Controllers, and host servers in the three data centers. The Los Angeles data center houses one 3DNS Controller and one BIG/ip Controller, as does the New York data center. The Tokyo data center houses only one 3DNS Controller and one host server.
In the Los Angeles and New York data centers, the big3d agent runs on the BIG/ip Controller, but in the Tokyo data center, the big3d agent runs on the 3DNS Controller. Each big3d agent collects information about the network path between the data center where it is running and the client's local DNS server in Chicago, as illustrated by the red lines. Each big3d agent also broadcasts the network path information it collects to the 3DNS Controllers running in each data center, as illustrated by the green, blue, and purple lines.
3DNS Controllers typically work in sync groups where a group of controllers shares load balancing configuration settings. In a sync group, any controller that has new configuration changes can broadcast the changes to any other controller in the sync group, allowing for easy administrative maintenance. To distribute metrics data among the controllers in a sync group, the principal 3DNS Controller sends requests to the big3d agents in the network, asking them to collect specific performance and path data. Once the big3d agents collect the data, they each broadcast the collected data to all controllers in the network, again allowing for simple and reliable metrics distribution.
When a client requests a DNS resolution for a domain name, DNS sends the request to the 3DNS Controller that is authoritative for the zone (running as a master DNS server for the domain). The 3DNS Controller chooses the best available virtual server out of a pool, and then returns a standard DNS answer record (an A record) to the requesting local DNS server. The local DNS server uses the answer for the period of time defined within the A record. Once the answer expires, however, the local DNS server must request name resolution all over again to get a fresh answer.
Figure 1.2 illustrates the specific steps in the name resolution process.
Note: The dotted portion of line 5 indicates that the actual hardware for this step is not shown, due to the number of ways ISPs can configure their networks. The actual machines that handle all other transaction events are shown, so all other lines are solid.
Each of the 3DNS Controller load balancing modes can provide efficient load balancing for any network configuration. The 3DNS Controller bases load balancing on pools of virtual servers. When a client requests a DNS resolution, the 3DNS Controller uses the specified load balancing mode to choose a virtual server from a pool of virtual servers. The resulting answer to this resolution request is returned as a standard A record.
Although some load balancing configurations can get complex, most load balancing configurations are relatively simple, whether you use a static load balancing mode or a dynamic load balancing mode. More advanced configurations can incorporate multiple pools, as well as advanced traffic control features, such as topology or production rules. (For a list of individual load balancing modes, see Load balancing modes , on page 1-7).
The 3DNS Controller balances connections across a group of virtual servers that run in different data centers throughout the network. You can manage virtual servers from the following types of products:
Figure 1.3 illustrates the hierarchy of virtual server management in our sample configuration.
While both controllers provide load balancing, one of the significant differences between the 3DNS Controller and the BIG/ip Controller is that the 3DNS Controller responds to DNS requests issued by an LDNS on behalf of a client, while the BIG/ip Controller provides connection management between the client and the back-end server.
Once the 3DNS Controller returns a DNS answer to an LDNS, the conversation between the LDNS and the 3DNS Controller ends, and the client connects to the IP address returned by the 3DNS Controller. Unlike 3DNS, the BIG/ip Controller sits between the client and the content servers. It manages the client's entire conversation with the content server.
The 3DNS Controller offers the following major new features in version 2.0.
The 3DNS Controller now supports the following configuration and monitoring tools:
The 3DNS Controller now offers two types of redundant system configurations:
All 3DNS Controller products now support two network interface cards. Use of the second network interface card is optional, and it can provide you an additional layer of redundancy. The separate network interface cards can connect through different routers or gateways to the same network, allowing for more than one available network path.
The new data center feature allows you to map out the network layout of the 3DNS Controllers, BIG/ip Controllers, and host machines that you use for load balancing. One major benefit of the data center feature is that you can use the big3d agent on one controller in the data center to collect network path data on behalf of all controllers and hosts that run in the same data center.
The 3DNS Controller now supports sync groups, which you can use to define one or more groups of controllers that share configuration settings and path statistics. A sync group contains a principal 3DNS Controller that broadcasts its configuration settings and path statistics at set intervals to the remaining 3DNS Controllers, referred to as receiver 3DNS Controllers, in the sync group. This can make system administration across a global network much easier, because it requires you to make configuration changes to only one controller, instead of all controllers running in the network.
Note that the big3d agent now uses broadcasting to distribute current path statistics and server status to all 3DNS Controllers running in the network. The principal controller in a sync group issues requests to the big3d agent, and once the big3d agent retrieves the requested information, it sends the information not only to the principal 3DNS Controller, but to all controllers. When the principal controller in a sync group broadcasts its configuration setting and path statistics to the receiver controllers, it includes the path statistics only as a backup to the path statistics that the controller should receive from the broadcasting big3d agent.
You can use the production rules feature to dynamically change the load balancing configuration depending on current network traffic patterns, or time of day. The F5 Configuration utility provides easy configuration for production rules, and the sample wideip.conf file provided in Appendix A includes two examples of the production rule language.
The 3DNS Controller now supports the following enhancements for dynamic load balancing:
The wideip.conf file now supports include statements. The new default structure of the wideip.conf file includes only the load balancing configuration settings. The metrics data, which was previously stored in the file, is now stored separately from the wideip.conf file and included only by reference.
You can find additional technical documentation about the 3DNS Controller in the following locations: