Abstract:
A method for structuring a content distribution overlay network for a peer-to-peer network is presented. The method includes receiving a request from a requesting node for content at a content node. The content node has processing capabilities to process the content for presentation to the requesting node. An overlay network, including the requesting node and the content node, is dynamically assembled after receiving the request for content, where the overlay network is self-organized from available nodes of the peer-to-peer network that are available at a time of the request and based on the content requested. Using the assembled overlay network, a head node of the overlay network determines if a child node in the overlay network has processing capabilities to process the content, where the child node is then assigned to process the content for presentation to the requesting node.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims priority from U.S. patent application Ser. No. 10/856,426 filed on May 28, 2004 and entitled “Content Distribution Overlay Network and Methods for operating same in a P2P Network”, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/476,084, filed on Jun. 4, 2003 and entitled “Virtual/Real World Dynamic Intercommunication Methods and Systems”, both of which are hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to peer-to-peer networks, and more specifically to managing the efficient distribution of content over the peer-to-peer network. 
         [0004]    2. Description of the Related Art 
         [0005]    A decentralized computing environment is defined by a number of computing systems interconnected to communicate with one another, wherein each computing system can perform both client and server functions. A peer-to-peer (P2P) network represents a decentralized computing environment in which each computing system within the P2P network is defined as a peer of every other computing system within the network. For discussion purposes, each peer computing system within the P2P network is referred to as a node. Additionally, each node within the P2P network is configured to execute software having substantially equivalent functionality. Therefore, each node is enabled to act as both a provider and a user of data and services across the P2P network. 
         [0006]    A common activity across a P2P network is to distribute content to certain requesting nodes of the P2P network. However, the distribution of content can be very processor intensive and can induce delays for requesting nodes to receive the content. For example, if a node requests video content, that content will have to be provided and transcoded into the format that the requesting node can use. The node that is assigned to transcode the content for the requesting node can be selected from any number of available nodes on the P2P network. 
         [0007]    In the prior art, there are a number of techniques for assigning certain nodes to transcode content for a requesting node, however, these algorithms are typically very arbitrary and do not take into account the capabilities of the transcoding node with respect to the requesting node. Due to this arbitrary assignment, the requesting node may not obtain the content in an efficient manner, and the transcoding node may become overloaded with tasks that could have been more efficiently handled by other nodes in the P2P network. 
         [0008]    In view of the foregoing, there is a need for a more comprehensive analysis of requesting nodes and nodes that are assigned to service the requesting nodes. 
       SUMMARY OF THE INVENTION 
       [0009]    Broadly speaking, the present invention provides methods, systems and architectures for a content distribution overlay network that is used in a peer-to-peer network. The content distribution overlay network is used to enable distribution of high demand content closer to end users in an efficient manner appropriate to the capabilities of each requesting end user. It should be appreciated that the present invention can be implemented in numerous ways, such as a process, an apparatus, a system, a device or a method on a computer readable medium. Several inventive embodiments of the present invention are described below. 
         [0010]    In one embodiment, a method for structuring a content distribution overlay network for a peer-to-peer network is disclosed. The method includes receiving a request from a requesting node for content at a content node. The content node has processing capabilities to process the content for presentation to the requesting node. An overlay network, including the requesting node and the content node, is dynamically assembled after receiving the request for content, where the overlay network is self-organized from available nodes of the peer-to-peer network that are available at a time of the request and based on the content requested. Using the assembled overlay network, a head node of the overlay network determines if a child node in the overlay network has processing capabilities to process the content. If the child node has processing capabilities to process the content for the requesting node, the child node assigned to process the content for presentation to the requesting node. 
         [0011]    Other aspects of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Embodiments of the invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings. 
           [0013]      FIG. 1  illustrates an example peer-to-peer network, where certain peers have different capabilities, in accordance with one embodiment of the present invention. 
           [0014]      FIGS. 1B-1  through  1 B- 4  illustrate an example procedure for communicating content to a higher capability node for distribution, in accordance with one embodiment of the present invention. 
           [0015]      FIGS. 2A-2C  illustrate examples of an overlay network structure in relation to the peer-to-peer network, in accordance with one embodiment of the present invention. 
           [0016]      FIGS. 3A and 3B  illustrate example overlay network tree structures having nodes organized by capability, in accordance with one embodiment of the present invention. 
           [0017]      FIG. 4  provides a pictorial illustration of the content distribution overlay network in relation to the peer-to-peer network, in accordance with one embodiment of the present invention. 
           [0018]      FIGS. 5 and 6  provide example flow charts of the method operations performed in functional examples of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The following embodiments define an overlay content distribution network, which is used to arrange certain nodes of a peer-to-peer network according to capability. In peer-to-peer networks, certain peers may request content from a node that may be holding the content. If this content is video data, for example, the node holding the content will be required to transcode the video data to a format of the requesting node. To assist in distributing the content to the requesting node, an overlay network is defined. The overlay network will consist of a head node that holds the content, and one or more levels of child nodes. The child nodes are nodes that can also provide transcoding services on the content. 
         [0020]    In the overlay network, each of the nodes are arranged in a hierarchy according to capability. The more capable nodes are at higher levels and the less capable nodes are at the lower levels. The head node, will be the highest capable node. Thus, transcoding will be provided to the requesting node by the lowest level child node that is capable of transcoding to the format desired by the requesting node. Although transcoding of video content from one format to another format is described in detail, it should be understood that any processing operation may be distributed using the overlay network that is used in conjunction with a peer-to-peer network. It will be obvious, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention. 
         [0021]    Peer-to-peer networks are decentralized computing systems made up of peers, which define nodes of the network. In some exemplary embodiments, a peer can include any computing device, such as a desktop-class computer, a server-class computer, a mobile device, a hand-held device, a cell phone, a PDA, a game machine, a game console, etc. However, in other embodiments, the peer can be a computing device that is capable of establishing communication with another computing device, as long as the computing devices are connected to the P2P network. 
         [0022]    In contrast with centralized computing systems, such as client/server environments, any peer in the P2P network can interact directly with any other peer in the P2P network. An example P2P network is a fully connected P2P network.  FIG. 1  illustrates a peer-to-peer network  100 , which is defined by a multitude of peers. For simplicity purposes, some example connections between the peers P 1 -P 10  are drawn, although more or less connections can exist at any one time. Thus, from time to time, more or less peers will be connected to the peer-to-peer network  100 . As is common in peer-to-peer networks, although the peers are interconnected, the capabilities of peers will differ. The capabilities of a peer can include, for example, processing power of the peer, network connection of the peer (e.g., high bandwidth connection or low bandwidth connection), other processing tasks of a peer, resource restrictions set by peer owners, stability of the peer, etc. As can be appreciated, there are a number of metrics that can be used to measure the capabilities of a peer. 
         [0023]    For illustration purposes, peer P 8  is identified as having low capability and Peer P 7  is identified as having high capability. If peer P 8  desires to efficiently share content  102 , peer P 8  will search for a high capability peer, such as peer P 7 . Peer P 8  will therefore provide the content to peer P 7  for ultimate distribution to other peers of the peer-to-peer network  100 . 
         [0024]      FIGS. 1B-1  through  1 B- 4  illustrate an example procedure that may be used to move the content from peer P 8  to peer P 7 . In  FIG. 1B-1 , peer P 8  may publish a request for a high capability node. Commonly there will be more than one high capability node that is part of the peer-to-peer network  100 . As will be discussed below, an overlay network tree will be defined for an identified high capability node, and children nodes will be associated with the identified high capability nodes. Thus, it is possible to construct multiple overlay network trees for each high capability node. In another embodiment, multiple overlay network trees will not be constructed, but alternatively, each of the high capability nodes will be made parent and children of each other. For ease of description, in the following examples reference will be made to a single high capability peer P 7 , and the resulting overlay network tree for that high capability peer P 7 . 
         [0025]    Returning to  FIG. 1B-1 , peer P 7  identified itself as a high capability peer to the published request of peer P 8 . In  FIG. 1B-2 , peer P 7  replies with information as to its availability to add the content of P 8  to its distribution list. If peer P 7  has availability, peer P 7  will obtain the content from peer P 8 . The content can be provided to peer P 7  by having peer P 8  stream the content to peer P 7  or peer P 7  can simply download it from peer P 8 . Once peer P 7  has the content in  FIG. 1B-4 , peer P 7  will publish its availability of content, noting that it is ready to service requests for the content. If the content is video content, peer P 7  will also be a node that can perform transcoding of the content from the format native to peer P 7  into a format this is native to another peer. 
         [0026]      FIG. 2A  illustrates a block diagram of an overlay content distribution network in accordance with one embodiment of the present invention. The overlay content distribution network is independent of the peer-to-peer network described in  FIG. 1 , although particular individual nodes of the peer-to-peer network define the nodes of the overlay content distribution network. The overlay content distribution network will include a parent transcoding node  152 , and at least one child transcoding node  154 . The parent transcoding node  152  is a node that has higher capability than its child transcoding nodes. The parent transcoding node  152  is a head node in a tree structure defined by nodes  152  and  154 . In general terms, the parent transcoding node  152  is capable of transcoding content from a first format to a second format. Preferably, the second format is the format native to the child transcoding node  154 . For example, the content may be video content, and the transcoding will allow the child transcoding node  154  to receive content in video format native to the child transcoding node  154 . The child transcoding node  154  will therefore receive the transcoded content from the parent transcoding node  152 , and will itself be capable of transcoding the content into a third format that is native to a requesting leaf node. As used herein, a leaf node is a node that receives content or services from one of the transcoding nodes or a pass-through node. A pass-through node is one that does not transcode the content, but can receive the transcoded content and pass the content to another node. With this basic definition in place, the parent transcoding node  152  and the child node  154  will define a multi-level parent-child overlay tree structure. 
         [0027]      FIG. 2B  illustrates an overlay content distribution network where the parent transcoding node  152  includes a number of child transcoding nodes  154 . The number of child transcoding nodes  154  that may be assigned to a particular parent transcoding node  152  will depend upon the bandwidth capabilities of the parent transcoding node  152 . For instance, the content being transcoded by the parent transcoding node  152  may have to be transcoded for a number of child transcoding nodes  154  that desire to receive the content. If the number of child transcoding nodes  154  grows to a larger number, the parent transcoding node  152  may not be able to provide transcoding services and the resulting content in a timely manner to each of the child transcoding nodes  154 . Thus, the set of children transcoding nodes  154  will be limited in number by the ability of the parent transcoding node  154 . Although only two levels of parent and child relationships have been shown with respect to the overlay content distribution network, it will be understood that the levels of parent-child relationships can be many depending upon the capabilities of the nodes that are part of a particular peer-to-peer network. 
         [0028]      FIG. 2C  illustrates a block diagram of a content distribution overlay network  200  that logically overlies a peer-to-peer network  100 . The peer-to-peer network  100  will function independent of the content distribution overlay network  200 . However, the content distribution overlay network  200  will be defined by peers of the underlying peer-to-peer network  100 . Each of the nodes that define the content distribution overlay network  200  will be selected from the peer-to-peer network based on the capability and availability of the particular nodes. In some embodiments, but not necessary, the geographic location of nodes may define whether specific nodes get added to the content distribution overlay network. 
         [0029]    In the examples of  FIGS. 2A and 2B , the parent transcoding node  152  will have a higher capability than the child transcoding nodes  152 . The larger the tree structure becomes, the organization of the child transcoding node levels will be defined such that higher levels will have higher capabilities than lower levels. In each level, there may be more than one node that has the same capability. Depending on the work load of particular child nodes, the transcoding may be delegated to selected child nodes that are less busy so that particular child nodes do not become overloaded. 
         [0030]      FIG. 3A  illustrates an exemplary content distribution overlay network  200 . In the content distribution overlay network  200 , a head transcoding node  202  is defined logically above transcoding nodes  204  and  206  which have lower capabilities than the head node  202 . Likewise, transcoding node  208  will have lower capabilities than transcoding node  204 . Transcoding node  208  is shown servicing leaf nodes  212   a  and  212   b , which are identified as PDAs (Personal Digital Assistants). 
         [0031]    Transcoding node  206  is shown servicing a node  210  that functions as a cell phone switch. Node  210  will then service sub-leaf nodes  214   a ,  214   b , and  214   c . Leaf nodes  214   a - 214   c  are defined by cell phones that use the services of node  210 . 
         [0032]    Thus, the content distribution overlay network  200  is defined based on capabilities of particular nodes that can provide transcoding services to a requesting node. A requesting node is part of the peer-to-peer network. The requesting node will request services and/or content from the head node which advertises the ability to distribute the content desired by the requesting node. Once a requesting node makes a request from the head transcoding node  202 , the head transcoding node  202  will identify whether there is a lower child node in the content distribution overlay network  200  that can handle providing the transcoded content to the requesting node. In one example, transcoding node  204  will be capable of providing transcoding services to the requesting node, which may be viewed as leaf node  212   a.    
         [0033]    However, transcoding node  204  will in turn, determine whether a child node of transcoding node  204  is capable of providing the transcoding services to the requesting node. In this example, transcoding node  208  is a child of transcoding node  204 . Transcoding node  204 , being the parent of transcoding node  208 , will provide transcoding services to transcoding node  208 . Transcoding node  208  will in turn provide transcoding services to the leaf node that requested the content initially from head transcoding node  202 . Thus, transcoding node  208  can provide the content transcoded into the format understood by leaf node  212   a . In the process described, the head transcoding node has an example transcoding bandwidth of 1600×1200×64 (100FP5 video). The example lower transcoding bandwidths for the other nodes are illustrated in the figures. Thus, the head transcoding node is capable of directly providing the transcoding services to the requesting node  212   a , however, the transcoding responsibility will be propagated downward from the head transcoding node  202  down to the lowest level capable child node in the content distribution overlay network  200 . The lowest level child node in the content distribution overlay network  200  may in one embodiment, however, have the capability of providing the transcoding services to the requesting node in terms of bandwidth, availability, and capabilities. If no capable child node exists, then the head transcoding node can directly provide the transcoding to the requesting node. 
         [0034]    For example, node  210  may also be a requesting node that requires cell phone switching functionality from the head transcoding node  202 . The capabilities required by the cell phone switch  210  are much higher than the capabilities that would be provided by either of transcoding nodes  204  and  208 . Therefore, the head transcoding node  202  could only delegate transcoding services through child node  206 . Child node  206  will therefore receive transcoding services from the parent head transcoding node  202 , and transcoding node  206  in turn will transcode to its child node  210 . Thus, the content distribution overlay network is defined by a plurality of transcoding nodes that lie beneath the head transcoding node. Each of the children of a particular node will have lower capability than the parent node. 
         [0035]    Accordingly, each transcoding node is organized in the content distribution overlay network tree based on its capabilities, where the lowest level node in the tree will have the lowest capabilities, and the highest level head node will have the highest capabilities. Then, based on the requesting node&#39;s capabilities and requirements, a transcoding node will be assigned to be directly providing transcoding services to the requesting node. 
         [0036]      FIG. 3B  illustrates a graphical representation of the content distribution overlay network  200  where the requesting peer P 10 , is the requesting node. In  FIG. 4 , peer P 10  is illustrated as providing a request for content  242 . The peer P 10  is part of the peer-to-peer network and is the requesting node in  FIG. 3B . Peer P 7  is the high capability peer in the peer-to-peer network, and is also defined as the head transcoding node  202  of the content distribution overlay network  200 . In one embodiment, the request that is received at the head transcoding node  202  is analyzed to determine whether the transcoding node  202  should service the requesting node directly or whether the transcoding should be delegated to a lower level node of the content distribution overlay network, depending on the capability requirements requested by the requesting node peer P 10 . 
         [0037]    In this example, leaf node  212   a  is defined by the peer P 10  node of the peer-to-peer network  100 . The capabilities of the requesting node peer P 10  are much lower than the capabilities of the head transcoding node  202 . In this example, the head transcoding node  202  will transcode the content to the format understood by transcoding node  204 . Transcoding node  204  is defined by peer P 6  as shown in  FIG. 4 . A determination again is made by transcoding node  204  as to whether the requesting node has a lower capability than that of the transcoding node  204 , and whether it is able to delegate the transcoding to a lower level child node of transcoding node  204 . In this example, transcoding node  204  (defined as peer P 6  in  FIG. 4 ), will delegate direct transcoding to transcoding node  208  that is defined as peer P 5  in  FIG. 4 . 
         [0038]    Once transcoding node  208  has received the transcoded content from transcoding node  204  (peer P 6 ), transcoding node  208  will again determine whether direct transcoding services should be delegated to a lower level node to enable transcoding for the requesting node peer P 10 . In this example, peer P 5 , which is defined by transcoding node  208  will be the lowest level child node that is capable of transcoding the content for the requesting node peer P 10 . Thus, transcoding node  208  (defined by peer P 5  in this example), will perform the transcoding of the content into the format requested by the requesting node peer P 10  (leaf node  212   a ). 
         [0039]    As shown in  FIG. 4 , the content that was provided by peer P 8  to peer P 7  for distribution was then distributed to the requesting node peer P 10 . However, the transcoding services for peer P 10  will not directly be provided by the high capability peer P 7 . Alternatively, the transcoding services provided to peer P 10  were provided by the lowest level child node in the content distribution network that is capable of providing transcoding services to the level requested by the requesting node. Therefore, the transcoding services were distributed among a number of nodes in the content distribution overlay network and are defined by the content distribution network path  240  in  FIG. 4 . 
         [0040]    Delegation, as used herein, does not mean that a node will simply pass the content through, but delegation means that a node will transcode the content and then pass the transcoded content for a lower child node where transcoding may again take place at a lower capability. Consequently, in the example, the high capability peer P 7  will simply transcode the content to a lower level capability format understood by peer P 6 , and peer P 6  will transcode the content to a lower capability level understood by peer P 5 , and peer P 5  will transcode information to the lower capability level requested by peer P 10 . However, if peer P 10  had a capability that was higher than peer P 5 , but still lower than peer P 6 , then peer P 10  would have received transcoded content from peer P 6  directly. Thus, the distribution of content across the peer-to-peer network will be managed according to the capability hierarchy defined by the content distribution overlay network, which is independent of the connections defined by the peer-to-peer network  100 . 
         [0041]      FIG. 5  illustrates a flowchart diagram of the method operations performed by a system that utilizes the content distribution overlay network in conjunction with a peer-to-peer network. The method begins in operation  302  where a request from a requesting node is received for content at a content holding node of a peer-to-peer network. The content holding node is assumed to be a node that is capable of distributing the content. A node that is capable of distributing the content should be a high capability node, such as node P 7  in  FIG. 1 . The requesting node can be any node that is part of the peer-to-peer network that desires to obtain the content from the content-holding node. 
         [0042]    The method then moves to operation  304  where upon the receipt of the request, reference is made to an overlay distribution network to identify a child node that is capable of processing the content for the requesting node. As mentioned above, if a child node of the content holding node is capable of providing the processing of the content for the requesting node, the content-holding node will delegate additional processing to the child node in the overlay distribution network. As mentioned above, the overlay distribution network tree structure is independent of the peer-to-peer network, and the overlay distribution tree is defined by at least a parent node that is capable of processing a request for content and a child that has less capability than the parent node, and is also capable of processing the request for content from a requesting node. As used in this method, the processing can include, for example, transcoding of video content. 
         [0043]    The method now moves to operation  306  where the identified child node that is capable of processing the content of the requesting node is assigned the duties to process the data for the requesting node. As mentioned above, the child node is a node that is capable of processing the content for the requesting node, but the child node has less capabilities than the parent node in accordance with the hierarchy defined by the overlay distribution network tree. The assigned child node will therefore provide the processing requested by the requesting node, and the requesting node will receive the content from the child node that is able to provide the content with the capability level that is at least able to satisfy the requesting node&#39;s capabilities. 
         [0044]    In broad terms, each parent in the tree is configured to process the content and then provide it to its child, which in turn can process the content for its child. 
         [0045]      FIG. 6  illustrates a flowchart diagram  350  of a more detailed processing example of using the overlay distribution network in conjunction with a peer-to-peer network. In operation  352 , the request from a requesting node is received for content at a content-holding node of a peer-to-peer network. As mentioned above, the content-holding node should be a node that is capable of distributing content to a number of peers and should also be a high capability node. In the example shown in  FIG. 1 , the high capability node may be the node peer P 7 . Peer P 7  will therefore define the head of the overlay distribution network, and other peers that are also capable of processing the content request by a requesting node may define child nodes of the head node in the overlay distribution network. 
         [0046]    In operation  354 , reference is made to an overlay distribution network to identify a child node of the content-holding node that is capable of transcoding the content for the requesting node. As mentioned earlier, the child node of the content-holding node should at least be capable of transcoding the content to the requesting node in order for the child node to be assigned the duties to transcode the content for the requesting node. If the child node is able to transcode the content for the requesting node, the method moves to operation  356  where the identified child node is assigned to transcode the content for the requesting node. The identified child node can be at any particular level in the parent-child tree structure of the overlay distribution network. 
         [0047]    The lower the identified node is, the lower the capabilities the node will have. However, the identified node must have the capabilities to transcode the content for the requesting node. If the requesting node is a high capability node, a child node may not be able to provide the transcoding services for the requesting node, and therefore the content-holding node (head node), may have to perform the transcoding of content directly to the requesting node. The method now moves to operation  358  where transcoding of the content begins to process at the content-holding node. 
         [0048]    At each child level below, each node will also complete a lower level transcoding of the content, until the lowest level assigned child node gets the content and transcodes the content for the requesting node. Thus, each parent in the overlay distribution network transcodes the content for its child node until the content is transcoded directly for the requesting node. 
         [0049]    In broad terms, a tree of nodes is constructed to define the overlay network, and each node in the tree is arranged based on capability. The highest node in the tree will have the highest capability. And, the parent nodes in the tree will provide transcoding of content that is to be provided to the child nodes. Each node, if it has children, will also provide transcoding of the content before it is passed to the child node. In some circumstances, a node may be a pass-through node, and no transcoding will occur at that particular node. Thus, in the peer-to-peer network, it is possible to move the transcoding out to lower capability child peers, which are closer in capability to the requesting peer. For instance, if a low capability device, such as a cell phone, requests video content, a lower capability child node can be charged with providing the transcoded content to the requesting cell phone. The upper level nodes also performed transcoding, but only to its immediate child nodes. Thus, the content can be distributed closer to the end users. 
         [0050]    This invention is particularly advantageous for streaming high demand content (e.g., video, audio, audio/video, and other data streams) to end users in an efficient manner that is appropriate to the capabilities of each end user. Thus, the overlay network is a capability-aware distribution forest of transcoding nodes, as a self-organizing overlay network of distributed peers. In one additional embodiment, the audio and video streams could be transmitted along the same path in a single overlay. This recognizes that audio is orders of magnitude smaller to transmit and less computationally complex. Thus reuse of the one overlay for both streams is warranted and leads to a major reduction in overlay maintenance. 
         [0051]    In another embodiment, the audio and video streams are transmitted along completely separate overlays. This recognizes that the overhead of audio is not as insignificant as we would like, so we need to manage its overlay separately to optimize its processing (transmission and transcoding). 
         [0052]    In still another embodiment, a hybrid model, where audio generally will take the same path as video, but can also find its own path at different levels of the hierarchy. This reaps some benefits of overlay maintenance sharing, and also allows audio streams to find mid-tree nodes that are better able to handle lower bandwidth audio, but cannot support even the lowest quality video. It should be noted that this also implies that 1 audio (or video) transcoding node could handle transcoding to N different output formats. 
         [0053]    The embodiments of the present invention can further be generalized. In state-of-the-art media presentations, there are many separate streams (referred to as “elementary streams”) which can encode audio, video,  3   d ,  3   d  animation, static images, etc. All of these are candidates for transcoding. Thus, the single fitness metric that we use to organize each node in the tree would have to be N-fitness metrics. Then, to globally and locally optimize the tree, weight would be given to the most expensive metric (likely to be video) and then organization would continue to optimize proceeding in order through the rest of the N metrics. In the hybrid mode defined above, although a bit more complex, a best balance can be achieved between redundant overlay maintenance overhead and finding optimal paths for each of the various elementary streams. As such, it should be understood that the defined embodiments were only exemplary and can be modified and combined to reach the desired outcome, depending on the type of data being exchanged over the peer-to-peer network. 
         [0054]    Embodiments of the present invention may be practiced with various computer system configurations including hand-held devices, microprocessor systems, microprocessor-based or programmable consumer electronics, minicomputers, mainframe computers and the like. The invention can also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a wire-based or wireless network. 
         [0055]    With the above embodiments in mind, it should be understood that the invention can employ various computer-implemented operations involving data stored in computer systems. These operations are those requiring physical manipulation of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared and otherwise manipulated. 
         [0056]    Any of the operations described herein that form part of the invention are useful machine operations. The invention also relates to a device or an apparatus for performing these operations. The apparatus can be specially constructed for the required purpose, or the apparatus can be a general-purpose computer selectively activated or configured by a computer program stored in the computer. In particular, various general-purpose machines can be used with computer programs written in accordance with the teachings herein, or it may be more convenient to construct a more specialized apparatus to perform the required operations. 
         [0057]    The invention can also be embodied as computer readable code on a computer readable medium. The computer readable medium is any data storage device that can store data, which can be thereafter be read by a computer system. Examples of the computer readable medium include hard drives, network attached storage (NAS), read-only memory, random-access memory, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes and other optical and non-optical data storage devices. The computer readable medium can also be distributed over a network-coupled computer system so that the computer readable code is stored and executed in a distributed fashion. 
         [0058]    Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications can be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.