DynamicAccess Server Features

Bidirectional Load Balancing

Bidirectional load balancing maximizes bandwidth at the server through the use of multiple parallel resilient server links (RSLs) that share the network load.

An RSL consists of two or more NICs that form a virtual NIC. Each virtual NIC has multiple physical NICs bound to it, forming a group. Each NIC in a group uses the same protocols and frame types. One NIC is designated the primary NIC and the others secondary NICs.

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   Figure 3 Types of Load Balancing Arrangements

    

Self-Healing Drivers

Self-healing drivers (SHDs) work together with RSLs to maintain the network connection. An SHD monitors the NIC continuously for error conditions and makes corrections. These corrections can include resetting the NIC, rebuilding software data structures, temporarily disabling features, or transferring all network traffic to secondary NICs (termed a failover event). An SHD can also continuously monitor the status of the physical NICs in a virtual NIC group before and after failover. Errors and actions are reported to the system console and to the system log file. Error threshold values can be configured at any time.

Failover

In addition to load balancing, RSLs provide failover fault tolerance between a server and a switch--if one NIC in a group fails, the others assume the network load of the failed NIC. The failover behavior of secondary NICs depends on how you set load balancing:

• In a transmit load balancing arrangement, the primary NIC is the only one that receives packets. If the primary NIC fails, a secondary NIC assumes the configuration profile, network traffic, and active status of the failed primary NIC.
• In a bidirectional load balancing arrangement, all NICs receive packets. If any NIC fails, receive load balancing is disabled, and the other NICs continue transmit-only load balancing activity. Receive load balancing is restored when new connections are established with clients.

Bidirectional load balancing is restored after a failure when applications create new connections and new clients log in.

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   Figure 4 Bidirectional Load Balancing Failover

    

VLANs

A VLAN is a group of location-independent and topology-independent devices that communicate as if they were on the same physical LAN. Network devices on different LAN segments and of different media types can be members of the same VLAN. Membership in a VLAN is determined by a VLAN tag that is transmitted with the Ethernet frame for use by a switch.

With VLANs, you can define a network according to:

• Organizational groups--For example, you can have one VLAN for the Marketing department and one for the Finance department.
• Application groups--For example, you can have one VLAN for e-mail users and one for multimedia users.

Implementing VLANs on a network has these advantages:

• It eases the change and movement of devices on IP networks.
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  With traditional IP networks, if users move to a different IP subnet, the IP addresses of each workstation must be updated manually. With VLANs installed, if an end station on VLAN 1 is moved to a port elsewhere on the network, you need only to specify that the new port is on VLAN 1.

  • It helps to control traffic.

  With traditional networks, congestion can be caused by broadcast traffic that is directed to all network devices whether they require it or not. Each VLAN can be set up to contain only those devices that need to communicate with each other, increasing network efficiency.

  • It provides extra security.

  Devices within each VLAN can communicate only with member devices in the same VLAN. If a device in VLAN 1 needs to communicate with devices in VLAN 2, the traffic must cross a router.

The DynamicAccess technology multiple VLAN capability supports IEEE 802.1Q VLAN tagging and works with any switch that is compliant with IEEE 802.1Q specifications. See your Ethernet switch documentation for more information on IEEE 802.1Q VLANs.