One common method used to alleviate server bottlenecks involves segmenting the network across multiple NIC's in the server. Figure 1 illustrates a typical setup utilizing four NIC's to segment the network so that if a failure occurs on one segment, it should not affect the other segments. If one segment fails, access to the server is lost for all clients on the failed segment. To get the clients on the failed segment back online the whole server has to be brought downed. Each segment is also limited to the throughput of a single NIC between the server and the switch or hub. During peak access times, bottlenecks can still occur.
Figure 1: Segmented Network Server with 4 NIC's
DFE-570TX NIC Design
DFE-570TX takes the segmented server concept one step further to provide for optimal use of all network adapters and guaranteed up time for all users across the network. Instead of assigning one network adapter to each segment, adapters are grouped together and treated as one logical adapter. Network traffic can then be balanced across all of the adapters so that a bottleneck does not occur at each network segment. Also, if any one connection or adapter fails, traffic is rebalanced over the remaining adapters so that all connections to the server are maintained. Figure 2 shows the same network with a single DFE-570TX represented by 4 adapters connecting to 4 segments.
Figure 2: NIC Express Server with a 4 NIC Array
Multi-Segment DFE-570TX
DFE-570TX can allow for segmenting the network at the server level. Figure 3 is an example of an Intranet server for which the network has been divided into two separate segments. Engineering and Accounting are on the first segment and Sales and remote users are on the second segment. Unlike the first example, this design provides for maximum throughput and fault tolerance for each segment. Each segment consists of an array of two network adapters with failover and load balancing being provided within each segment.
Figure 3: Segmenting a NIC Express Server with Two Arrays
DFE-570TX Driver Architecture
DFE-570TX for Windows NT is designed to be easily installed and unintrusive to the operating system. It is designed as an NT Intermediate NDIS driver similar to other network drivers for NT and that it sits on top of existing NIC drivers. The DFE-570TX driver shields the multiple adapters from NT and creates one virtual driver for each network segment installed.
In Figure 4 illustrated below, two network segments are created with each containing an array of two adapters. The DFE-570TX driver borrows the MAC address of the primary card in each array and advertises this single address to the NT Protocols stack. The Protocol Stack sees only one port to the network thus creating a virtual port for the operating system.
Figure 4: NIC Express Architecture
The NDIS driver handles all software functions for load balancing and dynamic failover in the NT Kernel. Kernel mode operation insures maximum performance with little to no latency. Also by operating in the kernel mode, DFE-570TX does not affect applications running in user mode thereby making compatibility issues moot.
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