Red Hat NETSCAPE ENTREPRISE SERVER 6.1 - 08-2002 ADMINISTRATOR Technical Information download pdf (Page 109)

Chapter 6. A brief introduction to Layer 4-7 Switching 97

Figure 6-1 Sample L4-7 configuration

Figure 6-1 shows how services can be deployed using Layer 4-7 Switching. Using the

GbESM in the BladeCenter, all server resources can be configured to support all applications,

with the GbESM spreading the load among them at all times. As the loads on Sales and

Marketing vary throughout the day or week or month, resources are automatically allocated in

real time to meet the need.

In this scenario, to provide load balancing for any particular type of service, each server blade

in the pool must have access to identical content, either directly (duplicated on each server)

or through a back-end network (mounting the same file system or database server).

The GbESM acts as a front end to the servers, interpreting user session requests and

distributing them among the available servers. Load balancing in the GbESM can be done in

the following ways.

Virtual server-based load balancing

This is the traditional load-balancing method. The switch is configured to act as a virtual

server and is given a V_IP for each service it will distribute. Each virtual server is assigned a

list of the IP addresses (or range of addresses) of the real servers in the pool where its

services reside. When the user stations request connections to a service, they will

communicate with a virtual server on the switch. When the switch receives the request, it

binds the session to the IP address of the best available real server and remaps the fields in

each frame from virtual addresses to real addresses. HTTP, IP, FTP, RTSP, IDS, and static

session WAP are examples of some of the services that use virtual servers for load

balancing.

Filter-based load balancing

A filter allows you to control the types of traffic permitted through the switch. Filters are

configured to allow, deny, or redirect traffic according to the IP address, protocol, or Layer 4

port criteria. In filter-based load balancing, a filter is used to redirect traffic to a real server

group. If the group is configured with more than one real server entry, redirected traffic is load

balanced among the available real servers in the group. Firewalls, WAP with RADIUS

snooping, IDS, and WAN links use redirection filters to load balance traffic.

Content-based load balancing

Content-based load balancing uses Layer 7 application data (such as URL, cookies, and Host

Headers) to make intelligent load balancing decisions. URL-based load balancing,

browser-smart load balancing, and cookie-based preferential load balancing are a few

examples of content-based load balancing.

GbESM

Server Blade

Sales

Market i ng

BladeCenter

Sales

Marketing

Sample L4-7 GbESM Configuration

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