Patent Publication Number: US-8990417-B2

Title: Peer-to-peer transmission system for data streams

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a US nationalization of PCT/EP 2010/056826, filed May 18, 2010, which claims priority to German Application No. DE 10 2009 022 207.3, filed on May 20, 2009, the entire contents of which are incorporated herein by specific reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a peer-to-peer transmission for data streams. Such a transmission system is, for example, known from the book “Peer-to-Peer-Systems and Applications” authored by Ralf Steinmetz and Klaus Wehrle, Springer Publishing, 2005, ISBN 3-540-29192-X. 
     2. Present State of the Art 
     Peer-to-peer (P2P) systems are network architectures of higher level, consisting of computers having equal rights (Peers), which participate at a collective data transmission and may thereby undertake both receiving and transmitting tasks. The total behavior of the system results from the local interactions between the peers. No central coordination of the interactions between the peers and no central data basis exist. On the contrary, each individual peer merely stores a part of the data present in the entire system and provides the other peers with this part. All stored data are thus available in the entire system. No peer administrates the entire existing content of data. 
     An example for a known peer-to-peer (P2P) system having a collective of peers  10 ,  20 ,  30  and a peer-to-peer transmission mechanism  40  is shown in  FIG. 1 . A data stream is fed to a transmitting peer  10  via its data input  11  by another peer of the collective. A data partitioner  12  in the transmitting peer  10  logically and with regard to time divides the incoming data stream into different parts, which are buffered in a volatile memory  13  so that the individual parts may be transmitted, on different paths by means of the peer-to-peer transmission mechanism  40 , to the receiving peers  20 ,  30  via connections  41 . The peer-to-peer transmission mechanism  40  is a transmission mechanism in a collective of peers, in which the data is distributed from at least one point (transmitting peer) to at least a point (receiving peer) in a non-central manner, namely by forwarding it between receiving peers. 
     The parts of the subdivided data stream, received from the receiving peer  20  via the connection  41 , are therein buffered in a volatile memory  21  and reassembled into a complete data stream, which is available at a data output  23 . A semiconductor main memory may, for example, be provided as the volatile memory  21 . Further, from the volatile memory  21 , the buffered parts of the subdivided data stream may be forwarded to other receiving peers in the collective  30  via the connections  42  and the peer-to-peer mechanism  40 , whereby the receiving peer  20  assumes the role of a submitting peer at least partially. The parts of the subdivided data stream, buffered by the volatile memory  21 , are further copied into a persistent memory  22  of the receiving peer  20  in order to copy them back into the volatile memory  21  at a later point in time if necessary. A disc drive memory may, for example, be provided as the persistent memory  22 . The copied-back parts of the subdivided data stream may in turn be forwarded from the volatile memory  21  to other receiving peers in the collective  30  via the connections  42  and the peer-to-peer transmission mechanism  40 , whereby, in this case as well, the receiving peer  20  assumes the role of a transmitting peer at least partially. 
     SUMMARY OF THE INVENTION 
     With regard to the above described peer-to-peer (P2P) system, the object of the invention is to reduce the amount of data to be stored persistently. 
     This object is solved, in accordance with the invention, in that a fraction of the received data is excluded from persistent storing, wherein this exclusion is performed by selecting parts of the subdivided data stream. 
     Preferably, the excluded fraction is small with regard to the remaining rest of data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of a known peer-to-peer transmission system for data streams; and 
         FIGS. 2 and 3  are schematic representation of novel peer-to-peer transmission systems for data streams. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The exclusion of a fraction of the received data from persistent storing according to the invention is described in more detail for two modifications of the system according to  FIG. 1  by means of  FIGS. 2 and 3 . 
     In the modification according to  FIG. 2 , the system of  FIG. 1  is extended by a second, secondary transmission mechanism. The data of the input data stream subdivided by the data partitioner  12  are fed into a data selector  14 , which selects a fraction of the data parts from the subdivided data (data parts). This selected fraction of subdivided data is excluded from buffering in the volatile memory and the subsequent transmission via the mechanism  40  in that the selected fraction is separated from the remaining data of the subdivided data and rerouted into a secondary transmission mechanism  50  by the data selector  14 . The remaining data of the subdivided data are, as in  FIG. 1 , buffered in the volatile memory  13  and therefrom fed into the primary transmission mechanism  40 . The selection of the to-be-excluded parts of the subdivided data is determined by a controller in the transmitting peer  10 , which is integrated in the data selector  14 . 
     All peers  20 ,  30  comprise a data combiner  24 , which is connected to the secondary transmission mechanism  50  via a connection  51 . Via the connection  51 , the peers  20 ,  30  are directly provided with the separated, rerouted fraction of the subdivided data from the transmitting peer  10  if necessary. The data combiner  24  combines the separated, rerouted fraction of the subdivided data with the remaining data of the subdivided data, which have been transmitted in the primary transmission mechanism  40  and buffered in the volatile memory  21 . At the output of the data combiner  24  (which represents the data output  23  of the peer  20 ), the complete data stream of the data subdivided in the peer  10  by the data partitioner  12  is then available. 
     For the modification according to  FIG. 3 , the system according to  FIG. 1  is provided with a data selector  25  in the receiving peer  20 , which selects a fraction from the subdivided data (data parts) buffered in the volatile memory  21 . This selected fraction of the subdivided data is separated in the data selector  25  and fed into a deleting unit  26 , which deletes the selected fraction. The remaining rest of the buffered, subdivided data (data parts) is fed into the persistent memory  22  by the data selector  25  and a copy thereof is there made. The copied remaining rest is copied back from the persistent memory  22  into the volatile memory  21  at a later point in time if necessary. 
     The selection of the to-be-excluded fraction of the subdivided data is determined by a controller in the transmitting or in the receiving peer. The selection is determined so that, in each individual receiving peer  20 , not the same data parts are affected by the deletion. This unequal selection may be performed by means of a counter or by means of a random generator. In case the receiving peer  20  requires the separated and deleted fraction of the subdivided data at a later point in time, in order to assume the role of a transmitting peer at least partially, then this deleted fraction is again transmitted by means of the peer-to-peer transmission mechanism  40 .