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10  An Efficient Framework for Running Applications on Clusters, Grids, and Clouds

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10.3.3  Technical Solutions for Deployment over Heterogeneous Infrastructures

In the best possible scenario, all the machines involved in one computation are externally accessible through a public IP without any network restriction. In practice, this rarely occurs and machines are usually isolated by firewall and NAT. Hence, we must explore more sophisticated strategies to make the communication possible among processes located in different domains.

10.3.3.1  Virtual Private Network (VPN)

A Virtual Private Network (VPN) is an overlay network built on top of an existing larger one. It is often installed to provide a secure extension of a private network into an insecure environment such as the Internet. Thus, communication between nodes is tunneled through the underlying network, bypassing firewalls.

In order to expose a private network to the Internet to allow some external machines to connect, a VPN Gateway, which will be the entry point of the network, must be configured. This gateway will be a part of the private network, but also has access to the Internet. Then, each client machine wishing to join the VPN will connect to the gateway. Regarding firewalls, client and gateway must be defiltered for both input and output VPN traffic.

A VPN can thus offer a way to add external resources to an IaaS, or add IaaS resources to a private infrastructure.

10.3.3.2  Amazon Virtual Private Cloud (VPC)

Amazon Virtual Private Cloud (VPC) service provides a private subnetwork within the Amazon Cloud. All EC2 nodes, composing this Amazon VPC, are isolated and can only be reached through a VPN connection from a private network. This allows seamless extension of an existing infrastructure and EC2 resources can be managed as private ones.

This service allows extending existing security and management policies of a private IT infrastructure to the VPC. By doing so, it allows applications to be seamlessly executed in multi-domain environments.

10.3.3.3  Message Forwarding and Tunneling

The ProActive middleware also offers a solution to address network restrictions such as firewalls and NAT, which is built-in and lightweight, based on SSH. This solution also provides a seamless integration of forwarding and tunneling, but at the application level (i.e. no need to configure routing at the OS and network levels).

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