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Global Server Load Balancing

What is Global Server Load Balancing and how it works ?

An Introduction

Load balancing is a technique that is used for distributing the workload evenly across computing machines, networks, processing units etc. It basically enhances utilization of resources and enables maximum throughput with minimum response time hence avoiding overloading of a single server.

An extension of the same technology is the Global Server Load Balancing. With this technology the Internet traffic can be distributed among different data-centers located at different locations of the planet. This technology is highly efficient in avoiding local downtimes and downtimes. There is a Master GSLB which monitors the health and responsiveness of the Slave sites, which inturn identifies the sites are available and can offer the best response.Cloud Servers

Ideally GSLB would include:
I. Redirection of requests to other closest sites (DC) incase the usual DC or server does not respond.
II. Forwarding the visitor requests to the site that is most closer to the place from where the request is raised from a geographic point of view.
III. Incase a threshold is reached at a site, the requests are forwarded to other site which may be at a different geo-location. It algorithm would calculate the shortest distance from when the request has been raised.

Scenarios and Requirements:

In Global Server Load Balancing (GSLB), a website or services are hosted on different servers located at different geo-locations. Lets consider, a visitor is browsing www.eukhost.com from US, in usual web hosting, this request would be sent straight to the server where it is hosted, and the request would be served from the UK server only. But in a Global Load Balancing architecture, since the website is hosted on servers across different servers located in different geo-locations, the user trying to access the website from US, would be served from the server that is located in US. The GSLB in a regular time interval checks the health of the slave servers for providing the best response hence directing the traffic to those servers.

There aren’t any special requirements for implementing Global Load Balancing for your website. You simply need to choose a server as you do in the usual way, but since you intend to apply load balancing acoss the globe, you are required to select servers in different locations. With Eukhost Ltd. you can choose between 3 locations i.e. UK, US and India. Your website data is placed on servers of your choice in all the three locations.

Note: For Global Load Balancing, it is recommended to choose servers of equivalent configurations.

There are ideally two methods how GSLB can be configured :
A. GLB – Global Load BalancingCloud Computing
B. DNS Load Balance

A. GLB – Global Load Balancing : In the technique of GLB, we use a primary server also known as the Master Server and is connected to Slave Servers located in different geo-locations ie. different DC’s. Whenever a request is raised, the Master Server checks the location from where it was initiated. Then cookies are set and it redirects the request to the nearest server location.

Process Flow :

i. The user (in this case user is in US) types the website url http://www.eukhost.com in the browser. Since global load balancing is applied, the request would first go to the Master server which is located in UK datacenter.

ii.
The Master Server would send a query to the requester for querying IP address, upon confirmation of the users IP address, cookies are set which contains every information on the user system.

iii. This information is forwarded to the Master Server which is in the meantime checking the health and level of responsiveness of the slave servers.

iv. Now the Master Server in the GSLB architecture, would redirect the request to nearest Slave Server (ie. in US).

v. The users gets a response and is able to view the website which is served from the US server and not the UK servers.

All these processes happens in fraction of seconds without the knowledge of the users.

A constant synchronisation takes place between Master and Slave servers across all the DC’s.

B. Global DNS Load Balance: Load Balancing can be fulfilled using DNS. In this the response to the DNS requests depends on requester’s geographic IP location and the response from DNS. Lets consider a similar example as above : If a user requests for http://www.eukhost.com, it is sent to GLB DNS Server which would check the IP of the visitor. Then it would identify the server that is closest to the location or to the one that has the minimum response time, and the traffic is forwarded or redirected.

Process Flow :

i. The user based in Malaysia tries to access the site eukhost.com. In this case the DNS Request is sent to the ISP and further to the GSLB DNS Server.

ii. Then, the GSLB DNS Server forwards the request to NameServers of all the Countries or to the GSLB Server located various geo-locations.

iii. Within fraction of second, the GSLB receives the response from every server, it then analyses the response time and identifies the Closest Server Location from the Users Request and then redirects it to that server.

iv. The users in this way get connected to the closest server. In this scenario, the user request is initiated from Malaysia, hence the closest server as identified by GSLB is located in India, hence the website gets served from server located in the Indian DataCenter.

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