Classic Load Balancer

                                      Classic Load Balancer

Classic Load Balancer provides basic load balancing across multiple Amazon EC2 instances and operates at both the request level and connection level. Classic Load Balancer is intended for applications that were built within the EC2-Classic network. We recommend Application Load Balancer for Layer 7 and Network Load Balancer for Layer 4 when using Virtual Private Cloud (VPC).

1.Layer 7 load balancing operates at the high-level application layer, which deals with the actual content of each message. HTTP is the predominant Layer 7 protocol for website traffic on the Internet. ...

 A Layer 7 load balancer terminates the network traffic and reads the message within.

2. Layer 4 load balancing uses information defined at the networking transport layer(Layer 4) as the basis for deciding how to distribute client requests across a group of servers.

For Internet traffic specifically, a Layer 4 load balancer bases the load-balancing decision on the source and destination IP addresses and ports recorded in the packet header, without considering the content of the packet.

At Layer 4, a load balancer has visibility on network information such as application ports and protocol (TCP/UDP).

The load balancer delivers traffic by combining this limited network information with a load balancing algorithm such as round-robin and by calculating the best destination server based on the least connections or server response times.


                         

Key Features

High Availability
You can distribute incoming traffic across your Amazon EC2 instances in a single Availability Zone or multiple Availability Zones. Classic Load Balancer automatically scales its request handling capacity in response to incoming application traffic.

Health Checks
Classic Load Balancer can detect the health of Amazon EC2 instances. When it detects unhealthy EC2 instances, it no longer routes traffic to those instances and spreads the load across the remaining healthy instances.

Security Features
When using Amazon Virtual Private Cloud (Amazon VPC), you can create and manage security groups associated with Classic Load Balancer to provide additional networking and security options. You can also create a Classic Load Balancer without public IP addresses to serve as an internal (non-internet-facing) load balancer.

SSL Offloading
Classic Load Balancer supports SSL termination, including offloading SSL decryption from application instances, centralized management of SSL certificates, and encryption to back-end instances with optional public key authentication. Flexible cipher support allows you to control the ciphers and protocols the load balancer presents to clients.

Sticky Sessions
Classic Load Balancer supports the ability to stick user sessions to specific Amazon EC2 instances using cookies. Traffic will be routed to the same instances as the user continues to access your application.

IPv6 Support
Classic Load Balancer supports the use of both the Internet Protocol version 4 and 6 (IPv4 and IPv6) for EC2-Classic networks.

Layer 4 or Layer 7 Load Balancing
You can load balance HTTP/HTTPS applications and use Layer 7-specific features, such as X-Forwarded and sticky sessions. You can also use strict Layer 4 load balancing for applications that rely purely on the TCP protocol.

Operational Monitoring
Classic Load Balancer metrics such as request count and request latency are reported by Amazon CloudWatch.

Logging
Use the Access Logs feature to record all requests sent to your load balancer, and store the logs in Amazon S3 for later analysis. The logs are useful for diagnosing application failures and analyzing web traffic. You can use AWS CloudTrail to record Classic Load Balancer API calls for your account and deliver log files. The API call history enables you to perform security analysis, resource change tracking, and compliance auditing.