Networking

Question 1

Public vs Private Services

Answer 1

We have three different network zones:
- The public internet
- The AWS public: used for services that have a public endpoint, like S3
- The AWS private: used by services behind a VPC

Question 2

AWS Regions, Availability Zones, Edge Locations

Answer 2

• Regions: full data centre spread across the globe. A country can have multiple AWS Regions
• Availability Zones: physically isolated data centre or set of data centres within a Region
• Edge Locations: local distribution points, mainly used to deliver content

Question 3

AWS Regions characteristics

Answer 3

1 - Geographic separation - Isolated by design to ensure fault tolerance
2 - Geopolitical separation - Different governance based on local laws
3 - Location control - Tune architecture for performance

Question 4

AWS Availability Zones (AZ) characteristics

Answer 4

AWS AZ is a physically isolated data centre or set of data centres within a Region. Each AZ is designed to operate independently, meaning a failure in one AZ doesn’t affect others. Multiple Availability Zones (AZs) within a Region provide redundancy and fault tolerance, ensuring applications can continue to operate even if one AZ experiences an outage.

Question 5

Service Resilience

Answer 5

• Global resilience: services that are placed globally and can tolerate Region failures. Examples: IAM and Route 53
• Region resilience: services that are placed regionally and can tolerate AZ failures, but not Region failures
• AZ Resilience: services that are placed on an AZ and will fail if the AZ fails

Question 6

VPC (Virtual Private Cloud)

Answer 6

• A default VPC is created once per region when an AWS account is first created
• There can only be one default VPC per region, and they can be deleted and recreated from the console UI
• They always have the same IP range and the same ‘1 subnet per AZ’ architecture

Question 8

The default VPC

Answer 8

• Always configured as 172.31.0.0/16
• The Region’s resilience is granted by dividing the CIDR across the AZs. The default is 1 “/20” subnet for each AZ
• It is possible to delete the default VPC without having to recreate it. Meaning no default VPC is present, but bear in mind that some services might rely on it
• Provides an Internet Gateway (IGW), Security (SG) and Network Access Control List (NACL)
  -The subnets assign public IPv4 addresses by default