Microsoft Technology Licensing, LLC

Microsoft Corporation

Stuart Ranson

John L Miller

Christos Gkantsidis

Manuel Costa

Pablo Rodriguez Rodriguez

Pablo Rodriguez

Armando Garcia-Mendoza

John Miller

The invention provides methods of encoding content for distribution over a network and methods for decoding encoded content which has been distributed over the network. In a first example in which the content is divided into a plurality of segments and each segment comprising a plurality of blocks of data, the method comprises selecting a segment from the plurality of segments and selecting at least two blocks of the selected segment from a store of blocks. A new encoded block is created from a linear combination of the selected blocks.

Encoding and decoding optimisations

Managing content by influencing its distribution in the form of blocks or other units is crucial to the performance of a peer-to-peer content distribution system. We provide a content management module at each peer node to achieve this. The content management module implements a content request/response cycle in order to negotiate about blocks of content with other peer nodes. This cycle comprises an offer request, offer reply and a block request. These steps are preferably followed by data exchange and verification. The negotiation protocol used by our content management module provides a generic method that is advantageously used in conjunction with different encoding schemes such as full network coding and group network coding. In one embodiment we use group network coding and add information to the offer request and offer reply to facilitate efficient content distribution. Block request messages are selected to promote the use of on-the-fly decoding where possible.

Content management in peer-to-peer content distribution clouds

A wire protocol is described which implements connection management and other methods to give enhanced peer-to-peer content distribution. Connections between nodes can be placed in a 'notify' state when they are idle but may soon yield useful content. This notify state is also used together with a content request/response cycle to allow a peer to evaluate content available at a neighbour. If no suitable content is available a notify state is entered. When new content is later received at the neighbour it is able to inform the requesting node to allow it to restart the content request/response cycle.

Peer-to-peer message format data structure

A topology management process is implemented which involves removing or 'tearing down' connections between nodes in certain situations in order to try to replace those connections with more optimal ones. Idle connections are torn down unless those are in a 'notify' state; a notify state being one in which a request for content has been made to a neighbour but that neighbour has no available content as yet. Idle connections in a notify state are torn down only if they remain idle for a longer time than that required before an idle connection is torn down. To avoid problems caused by clusters of node forming and of loners being unable to join the cloud, network churn algorithms are taught. These involve requiring nodes to drop connections when specified conditions are met. Relative content distribution between connections is monitored and this information used to influence selection of those connections to drop.

Growing community of inventors

Cambridge, United Kingdom

Stuart Ranson