A Comprehensive Guide to IBM WebSphere Host Publisher Version 3.5

Chapter 19. Cloning and Workload Management (WLM) 597

19.1.4 Load balancing of cloned EJBs

EJB requests directed from a client to an EJB are also load balanced. This type

of load balancing is referred to as Workload Management (WLM). Load

balancing of EJB requests is performed by the smart stub code that runs on the

EJB client to perform the remote invocation of the EJB. This topic is discussed at

length in the IBM Redbook WebSphere Scalability: WLM and Clustering Using

WebSphere Application Server Advanced Edition, SG24-6153.

19.2 Network Dispatcher

Network Dispatcher is load balancing software that improves the performance of

servers by distributing TCP/IP session requests to different servers belonging to

a group of servers. It allows multiple Host Publisher Servers to share the load of

multiple browser requests. If one server is unavailable, other servers pick up the

additional load, giving fault tolerance to the system. It also allows Host Publisher

to be installed on multiple platforms (see Figure 19-3 on page 598).

Note: Network Dispatcher is a component of the WebSphere Edge Server and it

is not provided with Host Publisher Version 3.5. For technical information about

this product, see for example WebSphere Edge Server: Working with Web Traffic

Express and Network Dispatcher (SG24-6172).

19.2.1 How Network Dispatcher works

Network Dispatcher (ND) allows many servers to serve the client while

maintaining the single server outward appearance. It identifies the least loaded

server and forwards the request to that server. Network Dispatcher also forwards

the original client’s IP address, so the server then responds to the client directly

without interaction with Network Dispatcher.

Since the Host Publisher application can contain many Integration Objects, some

of which may be chained together sharing the same back-end session, it

becomes important to allow a particular client to use the same server for series

of requests. The sticky port option in Network Dispatcher allows the client to be

assigned to a specific server for a period of time; each request will reset the

timer. The value of the timer is customizable.