load Balancing

Abstract

One of the greatest challenges to any organization is the maintaining of continuous and economical Web and application infrastructure and uptime. Business-critical Web sites and intranets face many challenges, from user traffic spikes to server bog down to handle compute-intensive SSL transactions, large and numerous data file requests and IO and memory overloads and hackers try to flood servers with malicious attacks.

The key components in dealing with increased and unpredictable Web traffic and enabling of high availability for both Web-facing and Internet applications is the application delivery and load balancing appliance.

 
Introduction

Load balancing is the process by which inbound internet protocol (IP) traffic can be distributed across multiple servers. Load balancing enhances the performance of the servers, leads to their optimal utilization and ensures that no single server is overwhelmed. Load balancing is particularly important for busy networks, where it is difficult to predict the number of requests that will be issued to a server.

Typically, two or more web serves are employed in a load balancing scheme. In case one of the servers begins to get overloaded, the requests are forwarded to another server. Load balancing brings down the service time by allowing multiple servers to handle the requests. This service time is reduced by using a load balancer to identify which server has the appropriate availability to receive the traffic.
 
 

Load Balancing in Server Network

The IT infrastructure is playing an increasingly important role in the success of a business. Market share, customer satisfaction and company image are all intertwined with the consistent availability of a company’s web site. Network servers are now frequently used to host ERP, e-commerce and a myriad of other applications. The foundation of these sites – the e-business infrastructure – is expected to provide high performance, high availability, and secure and scalable solutions to support all applications at all times.

However, the availability of these applications is often threatened by network overloads as well as server and application failures. Resource utilization is often out of balance, resulting in the low-performance resources being overloaded with requests while the high-performance resources remain idle. Server load balancing is a widely adopted solution to performance and availability problems.

Figure 2 General Network Diagram to Deploy Load Balance

End-user requests are sent to a load-balancing device that determines which server is most capable of processing the request. It then forwards the request to that server. Server load balancing can also distribute workloads to firewalls and redirect requests to proxy servers and caching servers.

Benefits to Use Load Balancer

Load balancing is the process of distributing service requests across a cluster of servers. There are many benefits to this process, these include:

• Improves performance - The highest performance is achieved when the processing power of servers is used intelligently. Advanced server load balancing products can direct end-user service requests to the servers that are least busy and therefore capable of providing the fastest response times.
• Creates Resilience - high-availability pairs for load balancer resilience, and creates fault-tolerance for back-end servers.
• Adds Intelligence - Content inspection rules allow sending requests for certain web pages to specific groups of servers.
• Improves Reliability - By continually monitoring the health of back-end servers, failed servers are automatically detected and removed from the cluster until they recover.
• Ease of Use - Easy to install and configure, and include a secure, web-based graphical user interface which provides you with visual alerting, health monitoring and cluster diagnostics.
• One-Click Session Persistence - If sticky sessions are required for web application, just turn on session affinity with one click.
• Improved flexibility and scalability - Many content intensive applications have scaled beyond the point where a single server can provide adequate processing power. Both enterprises and service providers need the flexibility to deploy additional servers quickly and transparently to end-users.
• Enhanced availability - server load balancing is its ability to improve application availability. If an application or server fails, load balancing can automatically redistribute end-user service requests to other servers within a server farm or to servers in another location.
• Less disruption - Server load balancing also prevents planned outages for software or hardware maintenance from disrupting service to end users.

Load Balancing Algorithms

A key feature of server load balancing is its ability to intelligently direct service requests to the most appropriate server. Extreme Networks switches offer the following integrated server load-balancing algorithms to successfully accomplish this.

• Round-robin. A round-robin algorithm distributes the load equally to each server, regardless of the current number of connections or the response time. Round-robin is suitable when the servers in the cluster have equal processing capabilities; otherwise, some servers may receive more requests than they can process while others are using only part of their resources.
• Weighted round-robin. A weighted round-robin algorithm accounts for the different processing capabilities of each server. Administrators manually assign a performance weight to each server, and a scheduling sequence is automatically generated according to the server weight. Requests are then directed to the different servers according to a round-robin scheduling sequence.
• Least-connection. A least-connection algorithm sends requests to servers in a cluster, based on which server is currently serving the fewest connections.
• Load-based. A load-based algorithm sends requests to servers in a cluster, based on which server currently has the lowest load.

Additionally, some load balancers incorporate failure detection. The load balancer keeps track of the server or the application running on the server and stops sending requests to a server after a failure.
 

Cisco Ace Load Balancer

The Cisco ACE Application Control Engine Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers is a next-generation load-balancing and application-delivery solution.

• Helps ensure business continuity by increasing application availability
• Improves business productivity by accelerating application and server performance
• Reduces data centre power, space, and cooling needs through a virtualized architecture
• Helps lower operational costs associated with application provisioning and scaling

It achieves these goals through intelligent load-balancing and content-switching technologies integrated with acceleration and security capabilities. A virtualized architecture and role-based administration helps to provision and deliver multiple applications from a single module to increase data centre scalability




Figure 3 Network Diagram to Deploy Cisco Ace

 

F5 Load Balancer

The F5 BIG-IP load balancer is an application delivery networking system that provides the most intelligent and adaptable solution to secure, optimize, and deliver applications, enabling organizations to effectively and competitively run their business. F5 BIG-IP load balancer is the only system that features a set of unified application infrastructure services that deliver total control, vision, and flexibility into application security, performance, and delivery. The result? Greater business agility and successful outcomes for the lifeblood of today's organization -- the application itself.

• Secure - It provides a suite of security services that play a significant role in bolstering network and application security, BIG-IP LB is deployed at a critical gateway to your most precious resources the applications that run your business.
• Fast - F5 BIG-IP LB provides a powerful solution for organizations looking to improve their application performance, increase the capacity of their existing infrastructure, lower infrastructure costs, and accelerate their applications.
• Available - F5 BIG-IP LB removes single points of failure and virtualizes the network and applications using industry-leading L7 intelligence. This ensures that all sites are always on, more scalable, and easier to manage than ever before

Alteon Load Balancer

The Alteon WSM is designed to enable a highly available data centre with no single point of failure. The Alteon WSM can operate in active/active, active/standby, and hot standby modes to ensure non-stop operations while providing parallel processing of Web traffic.

• Provides Local and Global Server Load Balancing and health checks, to optimize existing server infrastructure and minimize costs
• Enables Firewall and VPN Load Balancing, which can run simultaneously with server load balancing, for economical security deployments without bottleneck.
• Delivers Content Intelligent Switching and session-level persistence to maximize profitability while minimizing infrastructure impact.

 

Figure 4 Network Diagram to Deploy Alteon

Summary
 

The Cisco Ace and F5 both are great load balancer in their work and features but still companies prefer to switch to the F5 this is because they have the flexibility to monitor the servers in the datacentres.
The real things that need to look at are Cisco has cli skills, the F5 has a simple web front end and the Cisco GUI just can't compare.
Alteon is also a competitor of Ace and F5 but in performance it is not that much good and considered as compared to Ace and F5.

Conclusion

Server load balancing is a powerful technique for improving application availability and performance in service provider, web content provider and enterprise networks, but piecemeal implementation can also increase network cost and complexity. Server load balancing devices that don’t operate at wire speed can also create their own performance bottlenecks. Extreme Networks provides the key benefits of server load balancing while eliminating the potential cost, complexity, and performance issues.
Distributed server load balancing products can also provide disaster recovery services by redirecting service requests to a backup location when a catastrophic failure disables the primary site.