Elastic Load Balancing

Elastic Load Balancing

Elastic Load Balancing

With the help of Elastic load balancing, you can distribute traffic across group of EC2 instance in one or more Availability Zones. Elastic Load balancing support Routing, and load balancing of HTTP, HTTPS, TCP and SSL traffic to EC2 instances. It provides the single CNAME entry for DNS configuration and support both Internet facing and internal facing load balancers.

Types of load balancers:

There are following types of load balancers:

  • Internet-facing Load Balancers: It takes requests from client from internet and distribute them to Amazon EC2 instance that are registered with load balancer.
  • Internal Load balancers: Internal Load balancers are used to distribute the traffic between Amazon EC2 instances in VPC with private subnets.
  • HTTPS Load balancers: In this traffic is encrypted between your load balancers and clients that initiates HTTPS sessions. In order to use SSL, a SSL certificate must be installed on the load balancer where connection is terminated and traffic is decrypted and is then sent to Amazon EC2 instance.


A listener must be configured which checks for connection requests. Every Listener is configured with a protocol and port for a front-end connection and protocol and port for back-end connection. Elastic load balancing supports following protocols:

  • HTTP
  • TCP
  • SSL

Configuring Elastic load balancing:

Idle Connection Timeout:

When a client’s send request to load balancer, it maintains Connections, One connection between clients and Load balancer and another connection between Load balancer and EC2 instance. For each connection Load balancer manages an idle timeout which is triggered when no data is sent over connection for specified time period. , once idle time out is expired Load balancer closes that connection.

By default idle time out is 60 sec for both connection. If HTTP and HTTPS connection are going to be used, Keep-alive option must be enabled for your Amazon EC2 instances.


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