AWS Load Balancing { Part - I }
Using AWS Load Balancing to Optimize Traffic and Ensure Availability
What is Elastic Load Balancing?
Incoming traffic is uniformly distributed among several targets, such as EC2 instances, containers, or IP addresses, thanks to elastic load balancing.
For increased redundancy and dependability, it operates across one or more Availability Zones.
Keeps a close eye on the condition of every registered target to make sure traffic is only sent to healthy ones.
Automatically modifies the load balancer's capacity to accommodate variations in traffic demand.
Guarantees high availability and seamless scaling for applications with varying traffic.
Benefits
To distribute the workload, a load balancer divides traffic among several servers.
It enhances your apps availability and dependability.
Servers can be added or removed as needed without affecting the traffic flow of your application.
Health checks make ensuring that the load balancer only sends requests to servers that are in good health.
Your servers can concentrate on other duties by using load balancers to handle encryption and decryption.
How ELB works?
Across several Availability Zones, a load balancer controls incoming client traffic and directs it to registered targets, such as EC2 instances.
It only sends traffic to destinations that are healthy after keeping an eye on their condition.
The load balancer will cease transmitting traffic to a target until it recovers if it becomes unhealthy.
Listeners, which provide the protocol and port for incoming and outgoing traffic, are used to configure a load balancer.
Connections between the load balancer and the targets and between clients and the load balancer are managed by listeners.
Four different kinds of load balancers are available with AWS Elastic Load Balancing:
Application Load Balancers (ALB): For HTTP/HTTPS traffic and advanced routing.
Network Load Balancers (NLB): For high performance with TCP/UDP traffic.
Gateway Load Balancers (GWLB): For controlling external equipment, such as firewalls.
Classic Load Balancers (CLB): A legacy option for basic load balancing (previous generation).
Target groups are used by ALBs, NLBs, and GWLBs to control and direct traffic to particular targets.
CLBs are regarded as a previous generation since they register instances directly with the load balancer rather than through target groups.
What is an Application Load Balancer?
In the OSI architecture, an Application Load Balancer (ALB) functions at the application layer, or Layer 7.
Upon receiving a request, the load balancer determines which listener rule to apply by prioritizing the rules.
The load balancer directs traffic to the relevant target group based on the chosen rule.
Depending on the requests content (such as URL paths), you can set up listener rules to direct traffic to various target groups.
Even if a target is a member of more than one group, routing is managed independently for each target group.
Although round robin is the default routing mechanism, you can select the least number of pending requests.
The load balancer allows targets to be added or withdrawn without impacting the request flow.
When traffic to your application rises or falls, Elastic Load Balancing automatically adjusts the load balancer.
It is possible to set up health checks to guarantee that only healthy targets receive traffic.
What is a Network Load Balancer?
Operating at Layer 3 of the OSI model, a Network Load Balancer (NLB) has the capacity to process millions of requests per second.
The NLB tries to create a TCP connection on the designated port after receiving a connection request, choosing a target from the target group according to the default rule.
A load balancer node is created inside an availability zone when it is enabled. By default, unless cross-zone load balancing is enabled, traffic is exclusively dispersed within the same Availability Zone.
By distributing traffic throughout all enabled Availability Zones, cross-zone load balancing enhances load distribution.
Enable several Availability Zones and make sure each target group has targets in each zone to improve fault tolerance.
The IP address for that subnet is deleted from DNS if a target group loses a healthy target in an Availability Zone, although traffic can still be routed by the load balancer in other zones.
The load balancer chooses a target for TCP traffic using a flow hash method that takes into account different connection information (protocol, IPs, ports, and sequence numbers).
The flow hash technique for UDP traffic is based on the protocol, IPs, and ports, guaranteeing that every flow is consistently sent to the same destination.
Each configured Availability Zone has a network interface created by Elastic Load Balancing, which is utilized to provide each node a static IP address.
You have the option to assign an Elastic IP address to every subnet when building a load balancer that faces the network.
You provide the target type (such as EC2 instances, IP addresses, or an Application Load Balancer) when creating the target group, which affects target registration and client IP protection.
Elastic Load Balancing adapts seamlessly to variations in application traffic, and you can add or delete targets from your load balancer without disrupting traffic flow.
By keeping an eye on targets health, health checks make sure that only healthy ones receive traffic.
What is a Gateway Load Balancer?
Gateway load balancers assist in the deployment, scaling, and administration of virtual appliances such as intrusion detection systems and firewalls.
It distributes traffic to virtual appliances and serves as a single point of entry and exit for all traffic, expanding in response to demand.
Handles all IP packets across ports and forwards traffic in accordance with listener rules while operating at Layer 3 (network layer) of the OSI model.
Guarantees flow stickiness to particular appliances by employing the 2-, 3-, or 5-tuple approach.
Exchanges data between registered virtual appliances and the Gateway Load Balancer via the GENEVE protocol on port 6081.
Secure traffic exchange between VPCs is made possible by Gateway Load Balancer endpoints, which guarantee private communication between servers and appliances across VPC boundaries.
The virtual appliances are registered with a target group when the load balancer is deployed in the same VPC.
Route tables are used to control traffic to and from the Gateway Load Balancer endpoint.
Through the Gateway Load Balancer, traffic moves from the service consumer VPC to the service provider VPC and back again.
In order to configure the Gateway Load Balancer endpoint as the next hop in the route table, the endpoint and application servers need to be on different subnets.
Availability Zones and load balancer nodes
When a load balancers availability zone is enabled, a load balancer node is created in that zone.
Traffic will not reach targets that are registered in an Availability Zone unless the zone is also activated.
Make sure there is at least one registered target in each activated Availability Zone for optimal efficacy.
To increase reliability, it is advised that all load balancers have several Availability Zones enabled.
At least two Availability Zones must be enabled for Application Load Balancers.
In the event that one Availability Zone is inaccessible or does not have healthy targets, this configuration guarantees that traffic can still be routed.
When an Availability Zone is disabled, the load balancer stops sending traffic to the targets, but the targets are not deregistered.
Best Practices for ELB
To increase availability and fault tolerance, enable several Availability Zones.
To guarantee that traffic is only sent to healthy instances, set up health checks for each target.
To dynamically modify the number of targets in response to traffic demand, integrate your load balancer with Auto Scaling.
Your application servers will be less burdened if SSL/TLS decryption is offloaded to the load balancer.
Limit which resources can communicate with your load balancer by implementing strong security group restrictions.
Turn on access logs to keep an eye on traffic trends and record complete details about incoming requests.
Set up alerts for any problems and keep an eye on your load balancer's health and performance with AWS CloudWatch.
Applications that need users to be redirected to the same server for the duration of their session should use session stickiness, also known as session affinity.
To better organize and manage traffic, route it to various target groups using hostnames or URL routes.
Network load balancers can distribute traffic evenly among all targets in several zones by turning on cross-zone load balancing.
To minimize resource utilization and prevent holding pointless connections open, set the proper idle timeouts.
Make sure your target groups accurately represent the state of your infrastructure by reviewing and updating them on a regular basis.
Use AWS Web Application Firewall (WAF) together with your load balancer to defend against frequent online threats and vulnerabilities.
Use Cases
Web Applications : To improve performance and uptime, use ELB to split up web traffic among several web servers for load distribution and high availability.
E-Commerce Platforms : By allocating load among several instances and automatically modifying resources in response to demand, ELB assists in scaling web traffic during periods of high shopping demand.
Microservices Architectures : ELB can improve the management of complicated applications in a microservices context by directing traffic to the relevant microservice based on hostnames or URL routes.
Hybrid Cloud Deployments : ELB ensures smooth integration by distributing traffic between on-premises servers and cloud services in hybrid cloud situations.
Secure Online Services : Payment information and other sensitive client data are securely handled by outsourcing SSL/TLS encryption and decryption to ELB without affecting server performance.
Conclusion
By effectively distributing traffic among several resources, Elastic Load Balancing (ELB) improves application performance and availability.
It ensures that your infrastructure adjusts without human intervention by scaling automatically to match variations in traffic.
ELB improves the dependability and fault tolerance of your applications by performing health checks and directing traffic only to healthy targets.
Various load balancer kinds, such as ALB, NLB, and GWLB, allow you to optimize traffic routing according to the particular requirements of your application.
Your applications will continue to be robust, safe, and economical if you follow best practices like turning on multiple Availability Zones and integrating with Auto Scaling.