‫Okay, so let's summarize the section
‫on the ELB and the ASG.
‫So first, we discussed the concept of high availability.
‫Scalability would be vertical and horizontal,
‫elasticity and agility in the Cloud.
‫It is very important for you to understand
‫to which concept corresponds to which features.
‫For example, high availability
‫means that you are having your applications
‫across multiple availability zone.
‫Vertical scaling means that you're increasing the size
‫of an instance.
‫And horizontal scaling,
‫is that you are increasing the number of instances.
‫Elasticity is the ability to scale up and down
‫based on demand.
‫And agility is a concept of the Cloud that is going
‫to be able to make you work faster,
‫because you can create and delete resources
‫very, very quickly.
‫Now, our load balancers, or ELB,
‫are allowing us to distribute traffic
‫across backend EC2 instances, and they can be spread out
‫across multiple availability zones.
‫We support health checks to make sure
‫that the backend EC2 instances are indeed healthy.
‫And we have four kinds of load bouncers.
‫The classic one is old and retired.
‫We have the application balancer for HTTP type of workload
‫at the layer seven.
‫Network load balancer for very high performance
‫and TCP level load balancing, layer four.
‫And finally, the gateway load balancer, layer three,
‫to route the network itself, and make it go by, for example,
‫through some virtual appliances.
‫We have auto scaling groups that allow us
‫to implement elasticity for our application,
‫therefore spreading our load across multiple AZ
‫and scaling accordingly.
‫So we scale these EC2 instances
‫based on the demand on your system,
‫and we can replace unhealthy instances.
‫There's a tight integration between the ASG and the ELB.
‫So this is why they are a great combination,
‫and together, we achieve high availability, scalability,
‫elasticity, and agility in the Cloud.
‫All right, that's it.
‫I hope you liked it and I will see you in the next lecture.