Section 7: AWS Fundamentals: ELB + ASG

Question 1

What is ELB?

Answer 1

ELB (Elastic Load Balancer) is a managed load balancer. They are servers that forward traffic to multiple servers.

Question 2

What are the v2 (new generation) Load Balancers?

Answer 2

Application Load Balancer (ALB) compatible with HTTP, HTTPS, WebSocket

Network Load Balancer (NLB) compatible with TCP, TLS, UDP.

Question 3

What is the Load Balancer that allows to deal with TCP and UDP traffic to your instances?

Answer 3

Gateway Load Balancer (GWLB) which operates at layer 4 - IP Protocol

Question 4

How many ways can ELBs can be set up?

Answer 4

• Internal (Private)
• External (Public)

Question 5

What are Security Groups for ELBs?

Answer 5

• HTTP (80)
• HTTPS (443)
• Users will be able to hit Load Balancer with classic HTTP, HTTPS
• EC2 instances will only allow traffic from load balancer (security group)

Question 6

What type of Load Balancer would you pick to handle millions of requests per second?

Answer 6

Network Load Balancer

Question 7

Which Load Balancer should be chosen when is important to analyze the network traffic?

Answer 7

Gateway Load Balancer

Question 8

Which Load Balancer has less latency (~100ms)?

Answer 8

Network Load Balancer.

Question 9

Which Load Balancer has one static IP per Availability Zone?

Answer 9

Network Load Balancer.

Question 10

What are target groups for Network Load Balancers?

Answer 10

Target groups are a group of EC2 instances.

Question 11

Which Load Balancer uses the GENEVE protocol?

Answer 11

Gateway Load Balancer

Question 12

Which port does the GENEVE protocol implement?

Answer 12

Port 6081

Question 13

What are the target groups for Gateway Load Balancers?

Answer 13

• Group of EC2 instances
• IP Addresses (Must be private IPs).

Question 14

What are Sticky Sessions?

Answer 14

Also known as Session Affinity, a client is always redirected to the same instance behind a load balancer. Available for Application Load Balancer and Network Load Balancer.

Question 15

How Sticky Sessions are implemented?

Answer 15

Cookie is sent from client to load balancer. The cookie used for stickiness has an expiration date that can be controlled.

Question 16

What is a Pro and a Con of stickiness?

Answer 16

Pro: The user does not lose its session data.
Con: It may bring imbalance to the load over the backed EC2 instances.

Question 17

What are the types of Sticky Sessions?

Answer 17

1. Application-based cookies
   
   • Custom cookie
     Generated by the target
   • Application cookie
     Generated by the load balancer
2. Duration-based cookies
   Cookie generated by the load balancer

Question 18

How does With Cross-Zone Load Balancing work?

Answer 18

Each load balancer instance distributes evenly across all registered instances in all AZ.

Question 19

How does Without Cross-Zone Load Balancing work?

Answer 19

Request are distributed in the instances of the node of the Elastic Load Balancer

Question 20

Which type(s) of Load Balancer has cross-zone load balancing by default?

Answer 20

Application Load Balancing

Question 21

Why type(s) of Load Balancer has the cross-zone load balancing disabled by default?

Answer 21

Network and Gateway Load Balancers

Question 22

Which Load Balancer(s) will get charged if the cross-zone load balancing is enabled?

Answer 22

Network and Gateway Load Balancers

Question 23

What is connection draining?

Answer 23

AKA Deregistration Delay, while an instance is de-registering or becomes unhealthy, the LB will give enough time to complete requests. Once the instance is drained, the LB will stop sending requests to such instance.

Question 24

ALBs can route traffic to different Target Groups based on:

Answer 24

• URL Path
• Hostname
• HTTP Headers
• Query Strings

Question 25

What Load Balancer have a static IP address?

Answer 25

Network Load Balancer has one static IP address per AZ and you can attach an Elastic IP address to it.

Question 26

What is Server Name Indication?

Answer 26

Helps servers identify which SSL certificate to use when multiple domain names are hosted on the same IP address.

Question 27

What are the types of scaling policies?

Answer 27

1. Simple Scaling Policy: A single scaling adjustment that is applied whenever a CloudWatch alarm is triggered. For example, a CloudWatch alarm to trigger when CPU usage exceeds a certain threshold, and then set up a simple scaling policy to add or remove a fixed number of instances when that alarm is triggered.
2. Step Scaling Policy: Specific scaling adjustments for different levels of demand. For example, a step scaling policy to add one instance when CPU usage exceeds a certain threshold, add two instances when it exceeds a higher threshold, and so on.
3. Schedule Scaling Policy: Specify a schedule for adding or removing instances. For example, set up a schedule scaling policy to add two instances every weekday at 9am, and then remove them at 5pm.
4. Target Scaling Policy: Set a target value for a specific metric, such as CPU utilization or network traffic. The Auto Scaling group will then automatically adjust the number of instances to try to maintain that target value. For example, you could set a target scaling policy to maintain a target CPU utilization of 75%, and the Auto Scaling group will automatically add or remove instances as needed to keep the utilization at that level.

Question 28

What are the HTTP headers that are used by load balancers to provide information about the client’s connection to the origin server?

Answer 28

X-Forwarded-For: Identifies the IP address of the client that initiated the request.
X-Forwarded-Port: Indicates the port number that the client used to connect to the proxy or balancer.
X-Forwarded-Proto: Indicates the protocol (HTTP or HTTPS) that the client used to connect to the balancer. This is useful when the proxy or balancer is terminating SSL/TLS connections and forwarding plain HTTP traffic to the origin server. The X-Forwarded-Proto header allows the origin server to know whether the original request was made over a secure connection or not.