CAN U PLS SHARE THE CODE FOR LOAD BALANCING IN CLOUD USING NEURAL NETWORKS

code in matlab for load balancing

What is Load Balancing?

Load balancing is a core networking solution responsible for distributing incoming traffic among servers hosting the same application content. By balancing application requests across multiple servers, a load balancer prevents any application server from becoming a single point of failure, thus improving overall application availability and responsiveness. For example, when one application server becomes unavailable, the load balancer simply directs all new application requests to other available servers in the pool.

Load balancers also improve server utilization and maximize availability. Load balancing is the most straightforward method of scaling out an application server infrastructure. As application demand increases, new servers can be easily added to the resource pool, and the load balancer will immediately begin sending traffic to the new server.

How does Citrix help with load balancing?

Early generation server load balancers are tried and true solutions for improving the availability and scalability of an organization’s application infrastructure. Nonetheless, enterprises that persist in using such products run the risk of exposing themselves and their customers to increasingly poor application performance and a seemingly endless stream of application layer security threats.

As a leader in cloud networking and security solutions, the Citrix NetScaler line of products provide a much more efficient and effective approach – replacing the old server load balancers with new Application Delivery Controllers. These tightly integrated physical and virtual appliances not only provide core load-balancing capabilities, but also deliver the highest levels of security and performance for today’s business critical Web applications.

In computing, 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.

Load balancing differs from channel bonding in that load balancing divides traffic between network interfaces on a network socket (OSI model layer 4) basis, while channel bonding implies a division of traffic between physical interfaces at a lower level, either per packet (OSI model Layer 3) or on a data page link (OSI model Layer 2) basis.

One of the most commonly used applications of load balancing is to provide a single Internet service from multiple servers, sometimes known as a server farm. Commonly load-balanced systems include popular web sites, large Internet Relay Chat networks, high-bandwidth File Transfer Protocol sites, Network News Transfer Protocol (NNTP) servers, Domain Name System (DNS) servers, and databases.

For Internet services, the load balancer is usually a software program that is listening on the port where external clients connect to access services. The load balancer forwards requests to one of the "backend" servers, which usually replies to the load balancer. This allows the load balancer to reply to the client without the client ever knowing about the internal separation of functions. It also prevents clients from contacting back-end servers directly, which may have security benefits by hiding the structure of the internal network and preventing attacks on the kernel's network stack or unrelated services running on other ports.

Some load balancers provide a mechanism for doing something special in the event that all backend servers are unavailable. This might include forwarding to a backup load balancer, or displaying a message regarding the outage.

It is also important that the load balancer itself does not become a single point of failure. Usually load balancers are implemented in high-availability pairs which may also replicate session persistence data if required by the specific application

An alternate method of load balancing, which does not necessarily require a dedicated software or hardware node, is called round robin DNS. In this technique, multiple IP addresses are associated with a single domain name; clients are expected to choose which server to connect to. Unlike the use of a dedicated load balancer, this technique exposes to clients the existence of multiple backend servers. The technique has other advantages and disadvantages, depending on the degree of control over the DNS server and the granularity of load balancing desired.

Another more effective technique for load-balancing using DNS is to delegate example.org as a sub-domain whose zone is served by each of the same servers that are serving the web site. This technique works particularly well where individual servers are spread geographically on the Internet

Load balancer features[edit]
Hardware and software load balancers may have a variety of special features. The fundamental feature of a load balancer is to be able to distribute incoming requests over a number of backend servers in the cluster according to a scheduling algorithm. Most of the following features are vendor specific:

Asymmetric load: A ratio can be manually assigned to cause some backend servers to get a greater share of the workload than others. This is sometimes used as a crude way to account for some servers having more capacity than others and may not always work as desired.
Priority activation: When the number of available servers drops below a certain number, or load gets too high, standby servers can be brought online.
SSL Offload and Acceleration: Depending on the workload, processing the encryption and authentication requirements of an SSL request can become a major part of the demand on the Web Server's CPU; as the demand increases, users will see slower response times, as the SSL overhead is distributed among Web servers. To remove this demand on Web servers, a balancer can terminate SSL connections, passing HTTPS requests as HTTP requests to the Web servers. If the balancer itself is not overloaded, this does not noticeably degrade the performance perceived by end users. The downside of this approach is that all of the SSL processing is concentrated on a single device (the balancer) which can become a new bottleneck. Some load balancer appliances include specialized hardware to process SSL. Instead of upgrading the load balancer, which is quite expensive dedicated hardware, it may be cheaper to forgo SSL offload and add a few Web servers. Also, some server vendors such as Oracle/Sun now incorporate cryptographic acceleration hardware into their CPUs such as the T2000. F5 Networks incorporates a dedicated SSL acceleration hardware card in their local traffic manager (LTM) which is used for encrypting and decrypting SSL traffic. One clear benefit to SSL offloading in the balancer is that it enables it to do balancing or content switching based on data in the HTTPS request.
Distributed Denial of Service (DDoS) attack protection: load balancers can provide features such as SYN cookies and delayed-binding (the back-end servers don't see the client until it finishes its TCP handshake) to mitigate SYN flood attacks and generally offload work from the servers to a more efficient platform.
HTTP compression: reduces amount of data to be transferred for HTTP objects by utilizing gzip compression available in all modern web browsers. The larger the response and the further away the client is, the more this feature can improve response times. The tradeoff is that this feature puts additional CPU demand on the Load Balancer and could be done by Web servers instead.

TCP offload: different vendors use different terms for this, but the idea is that normally each HTTP request from each client is a different TCP connection. This feature utilizes HTTP/1.1 to consolidate multiple HTTP requests from multiple clients into a single TCP socket to the back-end servers.

TCP buffering: the load balancer can buffer responses from the server and spoon-feed the data out to slow clients, allowing the web server to free a thread for other tasks faster than it would if it had to send the entire request to the client directly.

Direct Server Return: an option for asymmetrical load distribution, where request and reply have different network paths.

Health checking: the balancer polls servers for application layer health and removes failed servers from the pool.

HTTP caching: the balancer stores static content so that some requests can be handled without contacting the servers.

Content filtering: some balancers can arbitrarily modify traffic on the way through.

HTTP security: some balancers can hide HTTP error pages, remove server identification headers from HTTP responses, and encrypt cookies so that end users cannot manipulate them.

Priority queuing: also known as rate shaping, the ability to give different priority to different traffic.
Content-aware switching: most load balancers can send requests to different servers based on the URL being requested, assuming the request is not encrypted (HTTP) or if it is encrypted (via HTTPS) that the HTTPS request is terminated (decrypted) at the load balancer.

Client authentication: authenticate users against a variety of authentication sources before allowing them access to a website.
Programmatic traffic manipulation: at least one balancer allows the use of a scripting language to allow custom balancing methods, arbitrary traffic manipulations, and more.

Firewall: direct connections to backend servers are prevented, for network security reasons Firewall is a set of rules that decide whether the traffic may pass through an interface or not.
Intrusion prevention system: offer application layer security in addition to network/transport layer offered by firewall security.

Load Balancing


Google Compute Engine offers server-side load balancing so you can distribute incoming network traffic across multiple virtual machine instances. Load balancing provides the following benefits with either network load balancing or HTTP(S) load balancing:

Scale your application
Support heavy traffic
Detect unhealthy virtual machines instances
Balance loads across regions
Route traffic to the closest virtual machine
Support content-based routing
Google Compute Engine load balancing uses forwarding rule resources to match certain types of traffic and forward it to a load balancer. For example, a forwarding rule can match TCP traffic destined to port 80 IP address 192.0.2.1. Such traffic is matched by this forwarding rule and then directed to healthy virtual machine instances.

Compute Engine load balancing is a managed service, which means its components are redundant and highly available. If a load balancing component fails, it is restarted or replaced automatically and immediately.

Google offers two types of load balancing that differ in capabilities, usage scenarios, and how you configure them. The scenarios below can help you decide whether Network or HTTP(S) best meet your needs.

Network Load Balancing

Assume that you are running a website on Apache and you are starting to get a high enough level of traffic and load that you need to add additional Apache instances to help respond to this load. You can add additional Google Compute Engine instances and configure load balancing to spread the load between these instances. In this situation, you would serve the same content from each of the instances. As your site becomes more popular, you would continue increasing the number of instances that are available to respond to requests.

In this situation, you would choose network load balancing to map incoming TCP/IP requests on port 80 (forwarding rules) to your target pool of virtual machines in the same region. You would configure a forwarding rule resource, a target pool that lists the instances to receive traffic, and health checks rules.

Cross Region Load Balancing

The network load balancing scenario above scales well for a single region, but to extend the service across regions, you would need to employ unwieldy and sometimes problematic solutions. By using HTTP(S) load balancing in this situation, you can use a global IP address that is a special IP that can intelligently route users based on proximity. You can increase performance and system reliability for a global user base by defining a simple topology.

In this situation, you define global forwarding rules that map to a target HTTP(S) proxy, which routes requests to the closest instances within a back-end service. The back-end service resource defines the groups of instances that are able to handle the requests.

Content Based Load Balancing

Content-based or content-aware load balancing uses HTTP(S) load balancing to distribute traffic to different instances based on the incoming HTTP(S) URI. For example, you have a site that serves static content (CSS, images), dynamic content, and video uploads. You can architect your load balancing configuration to serve the traffic from different sets of instances that are optimized for the type of content that they are serving.

In this situation, your global forwarding rules map to a target HTTP(S) proxy, which checks requests against a URL map to determine which back-end service is appropriate for the request. The back-end service then distributes the request to one of its resource groups that has one or more virtual machine instances.