As shown in this diagram, AWS PrivateLink services can be accessed privately and securely from on-premises users or applications via AWS Direct Connect or VPN connections. Additionally, if a service consumer wants to access a PrivateLink service from multiple VPCs in multiple regions, they could decide to deploy a PrivateLink endpoint in each VPC, and this would work just fine. Or the service consumer could decide to deploy the PrivateLink endpoint into a centralized AWS account, which functions as a network hub. 

VPC peering connections could then be used to allow VPCs in different regions access to the PrivateLink resources through the centralized PrivateLink endpoint. As it relates to AWS PrivateLink, there are a few AWS service quotas to be mindful of. 1, Interface and Gateway Load Balancer Endpoints per VPC. By default, the combined number of Interface and Gateway Load Balancer endpoints allowed per VPC is 50. However, this number is adjustable.

So, if an organization needed to create 52 PrivateLink endpoints to support their SaaS and partner connections, they must expand this quota to do so. 2, Gateway VPC Endpoints per Region. A Gateway Load Balancer is typically used to distribute traffic to network appliances for the purposes of traffic, security, compliance, and policy inspection. A service provider can make these types of services available over PrivateLink via a Gateway endpoint. 

AWS allows 20 Gateway VPC endpoints to be created per region, but this quota is also adjustable. 3, VPC Endpoint Policy Size. A VPC endpoint policy is an IAM resource policy that can be attached to a PrivateLink endpoint to control which AWS principles can use the endpoint to access endpoint services. The default PrivateLink endpoint policy allows all actions by all principles. The default policy can be modified or replaced, but the maximum number of characters supported within the policy, including white spaces, is 20,480 characters, and this quota is not adjustable.

Metrics are published to CloudWatch for any PrivateLink endpoint that is created. PrivateLink sends metrics to CloudWatch in one-minute intervals at no additional cost. These metrics can be used to monitor the performance of the PrivateLink connection to ensure that the system is performing as expected. The relevant metrics are shown on this table. ActiveConnection represents the number of concurrent active connections. 

BytesProcessed shows the number of bytes exchanged between endpoints, and this metrics will be helpful in determining the cost of a PrivateLink connection. NewConnections represents the number of new connections established through the endpoint. PacketsDropped displays the number of packets dropped by the endpoint. If this value increases, it could indicate a problem with either the consumer or the provider side of the connection. RstPacketsReceived displays the number of RST packets received by the endpoint. If this value increases, it could indicate a problem with the endpoint service provider.