Update the description of ECS_DYNAMIC_HOST_PORT_RANGE

ECS_DYNAMIC_HOST_PORT_RANGE supports both container port range and singular container ports use cases,
starting from ECS Agent version 1.70.0. Details of this change are available in aws#3601.

Author: chienhanlin

README.md

@@ -255,7 +255,7 @@ additional details on each available environment variable.
 | `NO_PROXY` | <For Linux: 169.254.169.254,169.254.170.2,/var/run/docker.sock &#124; For Windows: 169.254.169.254,169.254.170.2,\\.\pipe\docker_engine> | The HTTP traffic that should not be forwarded to the specified HTTP_PROXY. You must specify 169.254.169.254,/var/run/docker.sock to filter Amazon EC2 instance metadata and Docker daemon traffic from the proxy. | `null` | `null` |
 | `CREDENTIALS_FETCHER_HOST`   | `unix:///var/credentials-fetcher/socket/credentials_fetcher.sock` | Used to create a connection to the [credentials-fetcher daemon](https://github.com/aws/credentials-fetcher); to support gMSA on Linux. The default is fine for most users, only needs to be modified if user is configuring a custom credentials-fetcher socket path, ie, [CF_UNIX_DOMAIN_SOCKET_DIR](https://github.com/aws/credentials-fetcher#default-environment-variables). | `unix:///var/credentials-fetcher/socket/credentials_fetcher.sock` | Not Applicable |
 | `CREDENTIALS_FETCHER_SECRET_NAME_FOR_DOMAINLESS_GMSA`   | `secretmanager-secretname` | Used to support scaling option for gMSA on Linux [credentials-fetcher daemon](https://github.com/aws/credentials-fetcher). If user is configuring gMSA on a non-domain joined instance, they need to create an Active Directory user with access to retrieve principals for the gMSA account and store it in secrets manager | `secretmanager-secretname` | Not Applicable |
-| `ECS_DYNAMIC_HOST_PORT_RANGE` | `100-200` | This specifies the dynamic host port range that the agent uses to assign host ports from, for a container port range mapping. | Defined by `/proc/sys/net/ipv4/ip_local_port_range` | `49152-65535` |
+| `ECS_DYNAMIC_HOST_PORT_RANGE` | `100-200` | This specifies the dynamic host port range that the agent uses to assign host ports from, for container ports mapping. If there are no available ports in the range for containers, including customer containers and Service Connect Agent containers if Service Connect is enabled, service deployments would fail. | Defined by `/proc/sys/net/ipv4/ip_local_port_range` | `49152-65535` |
 
 Additionally, the following environment variable(s) can be used to configure the behavior of the ecs-init service. When using ECS-Init, all env variables, including the ECS Agent variables above, are read from path `/etc/ecs/ecs.config`:
 | Environment Variable Name | Example Value(s)            | Description | Default value |