Monday, August 31, 2015

F5-CA - Application Delivery Fundamentals - Load Balancing Essentials

Objective 3.01: Discuss the purpose of, use cases for, and key considerations related to load balancing

Explain the purpose of distribution of load across multiple servers

load balancing distributes workloads across multiple computing resources, such as computers, a computer cluster, network links, central processing units or disk drives. Load balancing aims to optimize resource use, maximize throughput, minimize response time, and avoid overload of any single resource. Using multiple components with load balancing instead of a single component may increase reliability and availability through redundancy. Load balancing usually involves dedicated software or hardware, such as a multilayer switch or a Domain Name System server process.

Given an environment, determine the appropriate load balancing algorithm that achieves a desired result

Explain the concept of persistence

Using the BIG-IP® local traffic management system, you can configure session persistence. When you configure session persistence, the BIG-IP system tracks and stores session data, such as the specific pool member that serviced a client request. The primary reason for tracking and storing session data is to ensure that client requests are directed to the same pool member throughout the life of a session or during subsequent sessions.
In addition, session persistence can track and store other types of information, such as user preferences or a user name and password.

More Information:

Load Balancing Wiki
Load Balancing 101
Load Balancing Algorithms
Load Balancing Least Connection, Fastest, Observed, and Predictive
Load Balancing Algorithm Dynamic Ratio
Load Balancing Algorithm Least Sessions
Session Persistence

Objective 3.02: Differentiate between a client and server 

Given a scenario, identify the client/server

In general, all of the machines on the Internet can be categorized as two types: servers and clients. Those machines that provide services (like Web servers or FTP servers) to other machines are servers. And the machines that are used to connect to those services are clients. When you connect to Yahoo! at to read a page, Yahoo! is providing a machine (probably a cluster of very large machines), for use on the Internet, to service your request. Yahoo! is providing a server. Your machine, on the other hand, is probably providing no services to anyone else on the Internet. Therefore, it is a user machine, also known as a client.

Explain the role of a client

The role of a client is to consume the services/resources provided by a server

Explain the role of a server

The role of a server is to provide one or more services to their clients.

More Information:

Client-server model

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