beneficial is Network Load Balancing?

Network Load Balancing is superior to other software solutions such as round robin DNS (RRDNS), which distributes workload among multiple servers but does not provide a mechanism for server availability. If a server within the host fails, RRDNS, unlike Network Load Balancing, will continue to send it work until a network administrator detects the failure and removes the server from the DNS address list. This results in service disruption for clients. Network Load Balancing also has advantages over other load balancing solutions—both hardware- and software-based—that introduce single points of failure or performance bottlenecks by using a centralized dispatcher. Because Network Load Balancing has no proprietary hardware requirements, any industry-standard compatible computer can be used. This provides significant cost savings when compared to proprietary hardware load balancing solutions.

The unique and fully distributed software architecture of Network Load Balancing enables it to deliver the industry's best load balancing performance and availability. The specific advantages of this architecture are described below in the "Network Load Balancing Architecture" section.

Installing and Managing Network Load Balancing

Network Load Balancing is automatically installed and can be optionally enabled on the Advanced Server and Datacenter Server versions of the Windows 2000 operating system. It operates as an optional service for local area network (LAN) connections and can be enabled for one LAN connection in the system; this LAN connection is known as the cluster adapter. No hardware changes are required to install and run Network Load Balancing. Since it is compatible with almost all Ethernet and Fiber Distributed Data Interface (FDDI) network adapters, it has no specific hardware compatibility list.

IP Addresses

Once Network Load Balancing is enabled, its parameters are configured using its Properties dialog box, as described in the online help guide. The cluster is assigned a primary IP address, which represents a virtual IP address to which all cluster hosts respond. The remote control program provided as a part of Network Load Balancing uses this IP address to identify a target cluster. Each cluster host also can be assigned a dedicated IP address for network traffic unique to that particular host within the cluster. Network Load Balancing never load-balances traffic for the dedicated IP address. Instead, it load-balances incoming traffic from all IP addresses other than the dedicated IP address.

When configuring Network Load Balancing, it is important to enter the dedicated IP address, primary IP address, and other optional virtual IP addresses into the TCP/IP Properties dialog box in order to enable the host's TCP/IP stack to respond to these IP addresses. The dedicated IP address is always entered first so that outgoing connections from the cluster host are sourced with this IP address instead of a virtual IP address. Otherwise, replies to the cluster host could be inadvertently load-balanced by Network Load Balancing and delivered to another cluster host. Some services, such as the Point-to-Point Tunneling Protocol (PPTP) server, do not allow outgoing connections to be sourced from a different IP address, and thus a dedicated IP address cannot be used with them.

Host Priorities

Each cluster host is assigned a unique host priority in the range of 1 to 32, where lower numbers denote higher priorities. The host with the highest host priority (lowest numeric value) is called the default host. It handles all client traffic for the virtual IP addresses that is not specifically intended to be load-balanced. This ensures that server applications not configured for load balancing only receive client traffic on a single host. If the default host fails, the host with the next highest priority takes over as default host.

beneficial is Network Load Balancing?