The Amazon cloud got fitter for the enterprise Tuesday, creating a hurdle for rivals.

Its 19-month-old Virtual Private Cloud (VPC) - which involves infrastructure off in a secure, private part of its cloud - no longer requires a secure virtual private network (VPN) connection. It can now be gotten to through the Internet.

Users can specify which Amazon VPC resources they want to be directly accessible over the Internet and which they don't.

That means they can set up public-facing EC2 and S3 subnets by setting up virtual networks in the Amazon cloud and keep their back-end databases and application servers sacrosanct.

Amazon blogged that "Enterprises can now define a virtual network topology in Amazon VPC that closely resembles a traditional network that they might operate in their own data center. Customers have complete control over the virtual networking environment, including selection of IP address range, creation of subnets and configuration of route tables and network gateways. Enterprises can continue to choose to connect Amazon VPC to their own existing IT infrastructure with an encrypted VPN connection, extending enterprises' existing security and management policies to Amazon VPC instances as if they were running within an existing data center."

It says the enterprise can:

• Create an Amazon Virtual Private Cloud on AWS' scalable infrastructure, and specify its private IP address range from any range they choose.
• Divide Amazon VPC's private IP address range into one or more public or private subnets to facilitate running applications and services in Amazon VPC.
• Control inbound and outbound access to and from individual subnets using network access control lists.
• Store data in Amazon S3 and set permissions so the data can only be accessed from within Amazon VPC.
• Attach an Amazon Elastic IP Address to any Amazon VPC instance so it can be reached directly from the Internet.
• Bridge Amazon VPC and an enterprise's own IT infrastructure with an encrypted VPN connection, extending enterprises' existing security and management policies to Amazon VPC instances as if they were running within an existing datacenter.

Remember too that Amazon has recently added the Elastic Beanstalk PaaS service and CloudFormation configuration widgetry to make it more appealing to the non-developer.

See http://aws.amazon.com/vpc/.