Intergraph WebScale User Manual page 76

WebScale™ User's Guide
servers at the client site.
Client request
A client request refers to a service request from an Internet-based client computer to a
server computer or to a cluster of computers running WebScale. WebScale forwards
each client request to a specific host within the cluster according to the system
administrator's load balancing policy.
WebScale associates an incoming TCP/IP datagram with a client request based on the
client's IP address, TCP or UDP port, and the destination port. Thus, all datagrams for
a single TCP connection are forwarded to the same host. Likewise, all UDP datagrams
with the same source IP address, source port, and destination port are forwarded to the
same host.
Note that several client requests are often needed to provide a higher level service, such
as downloading a single web page to a client. For these higher level services, WebScale
scales performance to a single client.
Cluster
A cluster is a set of computers that work together to provide a service. The use of a
cluster enhances both the availability of the service and the scalability of the computer
system that provides the service. WebScale provides a software solution for clustering
multiple Windows NT systems that provide networked services over the Internet and
over private intranets.
Cluster adapter card
When using multiple network adapter cards in each host of a WebScale cluster, the
cluster adapter card handles the network traffic for cluster operations, i.e., the traffic
for all hosts in the cluster. This card is programmed with host's cluster IP address. See
also, dedicated adapter card.
Convergence
A process by which WebScale hosts exchange messages to determine a new, consistent
state of the cluster and to elect the host with the highest host priority, known as the
default host. During convergence, a new load distribution is determined for hosts that
share the handling of network traffic for specific TCP or UDP ports.
Dedicated adapter card
When using multiple network adapter cards in each host of a WebScale cluster, the
dedicated adapter card handles network traffic not related to cluster operations, i.e., the
traffic for individual hosts on the network. This card is programmed with host's
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