Web-Server Load Balancing, a process that distributes the load of various incoming requests to several servers (e.g. using a gateway that functions as a dispatcher), in an effort to balance the load among these servers in an optimal way. This thesis inspects the various methods and strategies of server load balancing, clearly identifying the advantages and disadvantages of each strategy. We present a working, high performance implementation of the content-aware traffic redirection strategy, using the most well known scheduling algorithms. We also present the results of testing the effectiveness of the implementation and the scheduling algorithms in several scenarios. Finally, based on our work, we concluded that what seem to be the best scheduling algorithms in the case of identical requests are the least CPU usage and the weighted random scheduling algorithms which have the best response time and the best throughput. While in the case of non-identical requests the weighted round robin and the least CPU usage have the least response time and the greatest throughput. By: Abdul-Lateef Haji-Ali, Yael Jari, Bashar Shehadeh, Mhd. Mamdouh Tarabishi Wael Tayara Supervised by: Dr. Ghassan Saba

1. Web Server Load Balancing
By: Abdul-Lateef Haji-Ali, Yael Jari,
Bashar Shehadeh, Mhd. Mamdouh Tarabishi
Wael Tayara
Supervised by: Dr. Ghassan Saba

2. Outline
 What is SLB
 Scope of Project
 SLB Strategies
 Gateway Based Strategy
 Server Choosing Algorithms
 Implementation & Demo
 Testing & Results
 Future Work

3. What is Server Load
Balancing (SLB)?
• SLB is a process and technology that
distributes site traffic among several
servers.
• Transparent to the end user.
• A single URL can have hundreds of
servers

4. What is Server Load Balancing
(SLB)?

5. Scope of Project
 A study of most well known strategies.
 A study of most well known scheduling
algorithms.
 A working implementation of a single
chosen strategy for HTTP.
 A brief analysis of the implementation
and different algorithms.

6. SLB Strategies
 Geographic Load Balancing
 DNS Load Balancing
 Clustering
 Gateway based, redirection

7. Gateway Based Strategy
 Broad range of features
◦ Availability Scalability, Manageability,
Security, QoS
◦ Compression, caching, and packing
requests and responses
 Persistence using
◦ Cookies, source address, SSL, SIP
 Traffic redirection
◦ Transport layer
◦ Application Layer

8. Server Choosing Algorithms
 Scheduling
 Numerous, we chose 7
◦ Random
◦ Round Robin
◦ Weighted Random
◦ Weighted Round Robin
◦ Least Connections
◦ Least CPU Usage
◦ Dynamic Random

9. Least CPU Load (under focus)
 Constant monitoring of the servers for
their CPU load
 Pass the request to the one with the
least CPU load
 Pros: Most correct scheduling
decision, if updates are not too far
from each other
 Cons: If updates are slow, it can
cause congestion. Increased
overhead

10. Implementation
 4 Parts
◦ Core
◦ HTTP gateway implementation
◦ HTTP protocol support classes
◦ Other support classes
 Demo…

11. Testing
 Identical and non-identical requests
 Single server, no gateway
 Single server through gateway
◦ Overhead: 1.82%
 Two and three servers through
gateway
◦ All algorithms

12. Results

13. Results (cont.)
 Mostly agrees with literature
 Least CPU Usage has least response
time and greatest throughput

14. Future Work
 More algorithms
 More applications
 Caching
 Answer to: Is there a point where SLB
doesn’t increase performance?

15. Questions?