ANS-C01 Question 63
Select 3You are designing a highly available web application hosted on AWS. The application serves dynamic content through an API and static content from an Amazon S3 bucket. To optimize performance and ensure appropriate routing of traffic, you decide to use an Elastic Load Balancer (ELB). Which combination of load balancers and configurations is most appropriate for routing traffic at different layers of the OSI model?
- A
Use a Network Load Balancer (NLB) to route API requests based on client IP and port, operating at Layer 4.
- B
Use an Application Load Balancer (ALB) to route API requests based on HTTP headers and paths, operating at Layer 7.
- C
Use a Network Load Balancer (NLB) to route static content requests to the S3 bucket, allowing Layer 3 packet forwarding.
- D
Use an Application Load Balancer (ALB) to route static content requests to the S3 bucket, leveraging host-based routing at Layer 7.
- E
Use a Classic Load Balancer to handle both API and static content requests across multiple Availability Zones, operating at Layer 4 and Layer 7.
Show answer and explanation
Correct answers: A, B, D
Explanation
The appropriate choice of load balancer depends on the layer of the OSI model where traffic routing occurs. Network Load Balancers are suitable for Layer 4 traffic, such as routing based on IP and port. Application Load Balancers are ideal for Layer 7 traffic, allowing routing based on HTTP headers, paths, or hosts. In this scenario, the API requests benefit from the ALB's Layer 7 capabilities for intelligent routing, while the static content requests are also best handled by an ALB to interact with the S3 bucket. The Classic Load Balancer is outdated and not the best choice for this use case.
- A. Correct.
Correct: A Network Load Balancer operates at Layer 4 (Transport Layer) and is appropriate for routing traffic based on client IP and port, such as for API requests requiring high performance and low latency.
- B. Correct.
Correct: An Application Load Balancer operates at Layer 7 (Application Layer) and can route traffic based on HTTP headers or request paths, making it ideal for API requests with specific routing requirements.
- C. Incorrect.
Incorrect: A Network Load Balancer does not support routing static content to an S3 bucket, as S3 requires Layer 7 (HTTP) interactions.
- D. Correct.
Correct: An Application Load Balancer can route static content requests to an S3 bucket using host-based or path-based routing, leveraging Layer 7 capabilities.
- E. Incorrect.
Incorrect: A Classic Load Balancer can operate at Layer 4 and Layer 7, but it is not recommended for modern architectures due to its limitations compared to ALB and NLB.