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Overlay network, Network overlays |
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Overlay networks is a term for network that run on top of
existing infrastructure but provide certain additional functionality. Overlays
are created for a number of different reasons. Some overlays are created to
provide testbeds for novel protocols and distributed
systems that are hard to test on existing networks (for example, multicast and
IPv6 experiments). Other overlay networks are used in production to provide
features non-existent in the original protocols and infrastructure – for
instance, to provide additional security features to transactions done over
mainstream TCP and IP protocols that were not designed with security in mind. Another
example of features overlay networks can provide without drastic,
hard-to-implement changes to the existing infrastructure is quality of service
control.
The term is rather general, since depending on the goal of an overlay, their designs and uses may differ greatly. Some overlay network designs address the problems of reliable and flexible routing – perhaps, without a particular immediate application, but rather as a building block for other overlays. Sometimes, such “building block” overlay networks are referred to as “underlays”. An example of such technology – the distributed hash tables – is used in “higher-level” peer-to-peer networks and security overlay networks. Other overlay systems which exist both in production and as research prototypes, make use of existing lower-level overlay networks to provide routing and security, fitting them to a particular application. The mainstream networking protocols have been developed a few decades ago, whereas the shape, the uses and problems of the Internet have been changing and evolving on the regular basis. Yet, their universal acceptance makes any possible updates, changes or a complete switch to new technologies infeasible. Overlay networks provide a relatively inexpensive and easy way to test novel concepts, or to address unique concerns of a certain application while avoiding drastic, costly or incompatible changes. Virtual private networks (VPN) can also be considered as a type of an overlay. Secure VPN's help people cooperate all over the world every day. This website is dedicated to various overlay technologies. We have articles and news on various kinds of overlays used in research and production. |
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