Understanding Amazon ECS Task Definitions

Correct Answer: B.

The Docker networking mode to use for the containers in the task.

The valid values are none, bridge, awsvpc, and host.

The default Docker network mode is bridge.

If the network mode is a bridge, the task utilizes Docker's built-in virtual network which runs inside each container instance.

Incorrect Answers:

Option A is incorrect because only name and image are required as task definition parameters.

Option C is incorrect because If using the Fargate launch type, the awsvpc network mode is required.

If using the EC2 launch type, the allowable network mode depends on the underlying EC2 instance's operating system.

Option D is incorrect because Docker for Windows uses a different network mode (known as NAT) than Docker for Linux.

When you register a task definition with Windows containers, you must not specify a network mode.

References:

https://amzn.to/2Xv7mzc https://amzn.to/36De3n3

Sure, I can explain each option in detail:

A. Name, image, memory, and port mapping are task definition parameters required and used in most container definitions.

This option is correct. A task definition is a blueprint that describes how a Docker container should launch in Amazon ECS. It includes information like the container image, CPU and memory requirements, network configuration, and other settings. The name, image, memory, and port mapping are required parameters in a task definition that specify the container's image to use, the amount of memory allocated to it, and how it maps to the host ports.

B. If the network mode is a bridge, the task utilizes Docker's built-in virtual network which runs inside each container instance.

This option is also correct. Amazon ECS allows you to choose the network mode for your tasks, which determines how the containers communicate with each other and the host network. If you use the bridge network mode, each container gets its own IP address on a Docker virtual network, which runs inside each container instance. This mode provides basic isolation between containers and is suitable for most use cases.

C. If using the Fargate launch type, the awsvpc network mode is no longer required.

This option is correct. Fargate is a serverless launch type for Amazon ECS that allows you to run containers without managing the underlying EC2 instances. When you use the Fargate launch type, you can use the awsvpc network mode, which provides each task with its own elastic network interface (ENI). This means that each task has a unique IP address and can communicate directly with other tasks on the same ENI. Because Fargate manages the networking for you, you don't need to specify the awsvpc network mode in your task definition.

D. Docker for Windows offers host and awsvpc network modes as the highest networking performance so you can take advantage of dynamic host port mappings.

This option is incorrect. While Docker for Windows does offer host and awsvpc network modes, these modes are not specific to Windows and are available on other platforms as well. The host network mode allows the containers to share the host network stack, which can provide higher networking performance, but it also means that the containers can conflict with other processes running on the host. The awsvpc network mode, as mentioned earlier, is designed for Fargate and provides each task with its own ENI. Neither of these modes are required for dynamic host port mappings, which is a feature that allows you to specify a range of ports for the containers to use, rather than a specific port.