Intergraph WebScale User Manual page 5

WebScale™ Version 2, has exciting new features that make WebScale easier to install
and use. This version also incorporates several performance enhancements that take full
advantage of the latest, pipelined network drivers and adapter cards and ensure smooth
failover and failback behavior. The key changes are outlined in the following
subsections.
Removal of Single NIC Limitations
By default, WebScale now directs network traffic to the cluster NIC's using a multicast
cluster MAC address instead of by using a non-multicast cluster MAC address. The
WebScale driver no longer instructs the NIC driver (via the Windows NT Registry) to
load the cluster MAC address into the NIC card at system startup. This has several
important benefits:
Cluster hosts do not need two NIC cards to allow them to communicate with each
other. One cluster NIC can be used on each cluster host, and both the cluster's
primary IP address and the dedicated IP address can be bound to this card via
WebScale.
Cluster hosts now avoid the additional networking overhead associated with the
use of a single NIC card. In previous versions, all cluster hosts would receive
network traffic from outside the cluster that was intended for a particular host.
This overhead is now removed.
WebScale now works properly with Ethernet switches, which require that all
switch ports have unique MAC addresses.
WebScale now works with network adapter cards that do not allow their MAC
addresses to be changed. (Only a few, low-end cards have this limitation.)
WebScale's internal (one per second) messages now introduce less network
overhead on the subnet since only the cluster hosts receive them. They were
previously broadcast to all hosts.
WebScale automatically handles the resolution of the cluster IP address to its associated
multicast cluster MAC address by the Address Resolution Protocol (ARP). However,
the use of a multicast MAC address may not be supported by the ARP implementation
on some routers. In this case, it is necessary to create a static ARP entry within the
router.
For backward compatibility, WebScale supports non-multicast cluster IP addresses that
were used in previous versions. The WebScale Setup dialog lets you select between
multicast and non-multicast addressing. Starting with version 2.1, you can use a unicast
MAC address with switches.
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