CastGate

CastGate is an attempt from the ETRO-TELE research group at the Vrije Universiteit Brussel

Vrije Universiteit Brussel

The Vrije Universiteit Brussel is a Flemish university located in Brussels, Belgium. It has two campuses referred to as Etterbeek and Jette.The university's name is sometimes abbreviated by "VUB" or translated to "Free University of Brussels"...

 to break the chicken and egg problem of multicast

Multicast

In computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires...

 adoption on the internet

Internet

The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

.

Although multicast allows an internet user to receive rich media and other content without placing a high burden on the net, it is still virtually unavailable to normal internet users. The CastGate project tries to fix this by allowing end users to connect through an automatically configured tunnel network over networks which do not natively support multicast.
The idea behind this is that if more users have multicast capability, more content providers will see the benefit of streaming content over multicast.
If enough content providers and users are using this service, then more internet service providers

Internet service provider

An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...

 will start to enable multicast natively to their customers.

CastGate supplies a software client for both Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 and Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

 to connect to the CastGate tunnel network.
It also supplies tools to add tunnel servers and tools to receive SAP

Session Announcement Protocol

Session Announcement Protocol is a protocol for broadcasting multicast session information.A SAP listening application can listen to the SAP multicast IP address and construct a guide of all advertised multicast sessions...

announcements from the multicast network with video and audio streams.