HP e-Commerce / XML director server appliance sa8250 - Users Guide

C H A P T E R 2 Services
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Layer 4 (HOT) Services
HOT services provide the fastest brokered performance and are
available on the SA8250. HOT services are defined in full by their
Virtual IP address (VIP) and port number.
In HOT or “Brokered” mode, the SA8250 performs Network Address
Translation (NAT) on all packets passing through the connection.
NAT changes the destination IP address and port of incoming packets
to those of the selected fulfillment server. The source IP address is
modified to be that of the SA8250.
Fulfillment servers can be addressable by IP address, and thus can be
on either local or wide area networks.
By default, in HOT mode the fulfillment server sees all connections
as coming from the SA8250 rather than from the client's address. In
some environments, it may be preferable to have the fulfillment
server see the requests as they were coming directly from the client.
Source Address Preservation (SAP) on the SA8250 allows this to
happen. For more details, see Source Address Preservation later in
this chapter.
Layer 7 (RICH) Services
The SA8250 allows more flexible service fulfillment for RICH (Real-
time Intelligent Content Handling) services. The service type
“RICH_HTTP” is available on the SA8250 and enables it to make
fulfillment decisions based on the URL content of each client HTTP
request. RICH services also include advanced error detection, and
automatic resubmission of HTTP requests under most error
conditions.
As with HOT services above, fulfillment servers can be addressable
by IP address, and thus can be on either local or wide area networks.
XML services are configured as RICH services.