Abstract:
A method is provided for monitoring multicasting traffic in an internetwork between a multicasting source in a first domain and a multicasting destination in a second domain. The multicasting source offers connections to a predetermined multicast stream according to predetermined multicast group information. The multicasting destination sends a join message to a router within the internetwork in order to initiate routing of the predetermined multicast stream to the multicasting destination. A notification of the joining is sent from the router to a ledger application, the notification including identifying information of the multicasting destination and the multicasting source. The multicasting source transmitting datagrams of the predetermined multicast stream to the multicasting destination via the router. The ledger application receives and logs the notification as a transaction event. The transaction events are aggregated in response to the first domain of the multicasting source and in response to the second domain of the multicasting destination, thereby allowing reimbursement of costs between domains for transporting the multicasting traffic.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates in general to the multicasting of computer network datagrams to a plurality of recipients, and, more specifically, to monitoring multicast traffic and providing a means for a network domain that performs replication and transport of multicast datagrams to be compensated by the network domain or service that initiates the multicast traffic. 
     Packets or datagrams transported over a computer network can be sent as unicast, broadcast, or multicast messages. In the IP protocol, multicast messages use reserved IP addresses (Class D) set aside for multicast groups. For example, a source server or host may distribute streaming multimedia (e.g., video and/or audio) or other information as datagrams specifying a particular multicast group number in the destination address. The datagrams propagate via multicast-enabled routers which typically maintain local group databases identifying next-hop routers and/or end user destinations that have requested receiving datagrams from the multicast group. If a router&#39;s database identifies more than one destination for a multicast group, the router replicates the datagram and sends it to each destination. 
     The IP protocol suite includes the Internet Group Management Protocol (IGMP) for managing the interaction between destinations (e.g., end user clients) and multicast-enabled routers. So that multicast traffic does not have to be sent to clients or routers not interested in the particular traffic, multicast group databases maintained in the routers are constantly updated to identify clients or other routers that should receive traffic belonging to specific multicast groups. In most implementations, a client must send a join request to its neighboring router(s) in order to receive multicast group messages. When a client is no longer interested in a multicast stream, it sends a “leave” message to exit the multicast group. 
     When a router receives a join message for a multicast group that it is not currently receiving, then the router uses a multicast routing protocol such as Protocol-Independent Multicast (PIM) to create the necessary links from a source of the multicast stream to itself. When no longer needed, the router eliminates or prunes multicast distribution links to it that are no longer needed. 
     For certain kinds of traffic, multicasting can result in significantly more efficient use of overall network resources since multiple copies of the same information packets between any sender/receiver pair are avoided. The greatest savings are realized by the originating server of the multicast content since it does not have to originate separate traffic streams to each destination. Lesser saving are realized by the network backbone and there may be little or no savings in overhead for the destination network (e.g., an Internet service provider (ISP) operating a local area network (LAN) of a destination client). 
     In the current business model, the backbone provider and the ISP or other destination network have little motivation to provide multicast-enabled networks. The backbone provider receives compensation from the content provider based on the capacity of the purchased access. Since any particular content received as multicast traffic is no different than the same content obtained using unicast transmission (i.e., multicast content is not distinguishable from unicast content from the perspective of the destination client), there is no obvious improvement gained by an ISP&#39;s investment in multicast-enabled networks. Thus, an ISP is unlikely to be able to increase prices charged to end users for being multicast-enabled. 
     The extra costs of terminating multicast streams at the destination end of the network multicasts are borne by entities that derive the least benefit from the reduced network traffic realizable with multicasting. Since the deployment of widespread multicasting requires broad support from backbone providers and destination network providers, the current Internet business model has failed to motivate adoption of multicasting technologies. 
     SUMMARY OF THE INVENTION 
     The present invention provides a multicasting system and methods for encouraging widespread support of multicasting within all segments of an internetwork. 
     In one aspect of the invention, a method is provided for monitoring multicasting traffic in an internetwork between a multicasting source in a first domain and a multicasting destination in a second domain. The multicasting source offers connections to a predetermined multicast stream according to predetermined multicast group information. The multicasting destination sends a join message to a router within the internetwork in order to initiate routing of the predetermined multicast stream to the multicasting destination. A notification of the joining is sent from the router to a ledger application, the notification including identifying information of the multicasting destination and the multicasting source. The multicasting source transmits datagrams of the predetermined multicast stream to the multicasting destination via the router. The ledger application receives and logs the notification as a transaction event. The transaction events are aggregated in response to the first domain of the multicasting source and in response to the second domain of the multicasting destination, thereby allowing reimbursement of costs between domains for transporting the multicasting traffic. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a connection of networks in an internetwork for transporting multicast traffic over a backbone to end users. 
         FIG. 2  is a block diagram of communication with a ledger application of the present invention. 
         FIG. 3  is a flowchart showing a preferred embodiment of the present invention. 
         FIG. 4  is a flowchart showing operation of a source server providing multicast streams according to the present invention. 
         FIG. 5  is a flowchart showing operation of a network router according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , an internetwork such as the global Internet  10  comprises the interconnection of multiple networks such as Internet Service Provider (ISP) networks  11 ,  12 , and  13 , which each may be comprised of a LAN, MAN, RAN, WAN, or other network type. An internetwork backbone  13  provides interconnectivity to carry traffic between remote networks. 
     With regard to streaming of multicast traffic, a source (i.e., origin) server  15  in ISP  11  transmits multicast datagrams into Internet  10  via a router  16  in ISP  11  which interfaces to backbone  14 . ISP  12  has a router  17  interfacing end users  18  to the rest of Internet  10 . Likewise, a router  20  in ISP  13  routes traffic between end users  21  and Internet  10 . In addition, ISP&#39;s may be directly connected separately from the backbone, as shown by the direct connection between routers  17  and  20 . End users become a destination client when receiving the streamed multicast traffic from source server  15 . 
     Each respective network may comprise a specific domain within the addressing scheme of the internetwork. As used herein, domain also refers to subdomains within a domain. For example, a particular host identified using a respective subdomain name (e.g., source server  15 ) is included in the meaning of domain. Thus, the monitoring and accounting of multicasting traffic of the present invention is adaptable to aggregating information for any domain or subdomain level desired. 
     Various protocols have been defined for establishing multicast traffic distribution, and the present invention is useful no matter what multicast protocols or standards are employed. By way of example, a typical multicasting process requires each end user desiring to receive certain multicast traffic to inform its neighboring router(s) of the multicast group it is interested in (e.g. via a join message). The router checks whether it is currently receiving traffic according to the multicast group number. If not currently receiving it, then further neighboring routers are contacted until a complete path is created back to the multicasting source. 
       FIG. 2  shows a first embodiment of the invention wherein a ledger application runs on a ledger application host  25  for monitoring usage of multicast traffic feeds and for aggregating usage according to domains of multicasting sources and multicasting destinations, thereby providing a mechanism for domains supporting multicast reception by their users to be compensated by the multicasting sources. Host  25  can be located anywhere in Internet  10 , but may preferably reside in a computer within the central backbone. Host  25  receives messages itemizing individual multicasting transaction events (e.g., joins and leaves) to be processed by the ledger application. 
     When end user  18  sends a join message to router  17 , the destination IP address of end user  18  is added to a local group database  26  along with the multicast group number. Known protocols may be used (e.g., PIM) to establish a chain of routers for forwarding multicast datagrams of the multicast group from source server  15 , through routers  27  and  28 , and to router  17 . One or more of the multicast-enabled routers (or intermediary devices) are programmed according to the present invention for notifying the ledger application of multicasting activities. 
     In a preferred embodiment as shown in  FIG. 3 , a user browses in step  30  (e.g., using a world wide web browser) to a web page representing the multicast source server in order to request reception of a particular stream of multicast traffic (e.g., a video and/or audio stream for display by a multimedia player). The Web page need not be located on the same server as the stream source. Unless the source server does not charge an access fee and gives access to any anonymous requestors, the user may be authenticated in step  31 . The user may be required to supply a user ID and password or provide billing information as part of the authentication process. Thus, it is expected that the domain of the source server derives revenue from the transmission of the multicast traffic (e.g., directly from the user or indirectly through advertising). 
     Once a user is authenticated, the source server sends the multicast group ID of the requested stream to the end user in step  32 . This information is sent as a unicast message and provides the information needed by the end user client to construct a join message which it sends to its router in step  33 . The source server may also send stream control commands to the streaming source. In connection with digital rights management, a decoding key may also be sent to the end user to be used in decoding a content stream where an encrypted stream is to be sent via multicasting. In step  34 , the content source may be authenticated to ensure proper identification of the bill paying entity. In some instances, the content source authentication might not occur until multicast traffic is actually received (thereby identifying the source IP address or domain). 
     In step  35 , a router responds to the joining of the end user (or the end user&#39;s domain) by notifying the ledger application of the join. The notification can take place immediately when the join occurs, later after the join is terminated, or later as part of periodic batch updates to the ledger application. It may also be desirable to defer notification until multicast traffic is actually received and forwarded to the end destination. 
     In step  36 , the router servicing the end user (destination client) employs a multicast routing protocol to create a multicast router chain back to the stream from the source server or other closer point receiving the stream (if the router is not already receiving the multicast group on behalf of other destinations). Thereafter, the router receives and forwards multicast datagrams within the multicast group to the requesting destination client in step  37 . If desired, the router may update the ledger application with elapsed time status as the destination client continues to participate in the multicast group. The status update should be periodic, based either upon elapsed time interval since the last update or the amount of transported data. Updating for each received packet would result in excessive overhead. 
     When a user terminates reception of the multicast stream (e.g., by closing their media player or other action to terminate the stream), their client application sends a leave message to the router in step  38 . The router notifies the ledger application of the leaving of the particular end user in step  39 . In a prior version of a multicasting protocol that did not use “leave” messages, the router periodically polled the users in the local group database to determine if any were still interested in the multicast content. Once any interested destination responded, others would see the first user&#39;s response and then would drop their own response in order to reduce network congestion. Thus, the router would not know the identities of all the destinations still interested in the multicast traffic. For the present invention, the destination clients would have to be modified to answer a poll regardless of answers from other clients. Due to the increased network congestion, however, the use of explicit leave messages is preferred. 
     The ledger application stores and accumulates transaction events over a predetermined period (e.g., a one month billing cycle). Preferably, each transaction event may correspond to an individual multicast session between a user (as identified by a reception domain) and a stream source (as identified by a sending domain, the time, and the group ID). Multiple copies of the ledger application may be deployed, each handling separate regions within the internetwork, for example. 
     In step  40 , the ledger application aggregates its stored transaction events, preferably sorted according to sending domains and reception domains. Using the aggregated events, payments are collected from the sending domains and disbursed to the reception domains and intermediate domains that transported the multicast traffic (e.g., the backbone network) in step  41 . 
     In an alternative embodiment, the present invention can be used within an internal business enterprise for allocating costs between subdivisions of the enterprise. Thus, individual groups or cost centers can be charged back for bandwidth taken up by multicasting traffic within a private network. The ledger application can be located at any convenient location within the private network. 
     Operation of the source server is shown in greater detail in  FIG. 4 . The server is initialized in step  45  so that it can advertise its content streams via browsable Web pages in step  46 . Eventually, a request for a content stream is received in step  47 . The source server attempts to authenticate the requesting user in step  48  (e.g., determining requestor ID and a billing account ID). A check is made in step  49  to determine whether the user has been authenticated. If not, then an error may be logged in step  50  and a return is made to step  47  for handling further requests. 
     If the user is properly authenticated and their request is valid, then a unicast message is sent from the source server to the end user destination client in step  51  informing it of the multicast group ID being used for the requested stream. A check is made in step  52  to determine whether the requested stream is already being transmitted. If it is, then a return is made to step  47 . If not already streaming that multicast group then the stream is initiated in step  53 . 
     Router operation is shown in greater detail in  FIG. 5 . Although the operation is shown primarily in the context of a neighboring router directly servicing a destination network, some or all of the same functions may be performed in routers or other devices at other locations in the multicast distribution chain. 
     After initialization in step  60 , the router receives multicast-related packets. In step  61  a check is made to determine whether a join message is being received. If so, then any necessary authentication is performed and the ledger application is notified of the join in step  62 . The notification includes identifying information of the multicasting destination (e.g., the domain where the end user resides) and an identification of the multicasting source (e.g., the domain where the source server resides or the multicast group number and timestamp which may be subsequently correlated with the correct domain by the ledger application). In step  63 , the router checks to determine whether the multicast stream identified by the multicast group ID is already available to the router. If so, then a return is made to step  61 ; otherwise the router sets up a multicast routing chain of the multicast group ID in step  64  before returning to step  61 . 
     If a join message is not detected in step  61  then a check is made in step  65  to determine whether a leave message is being received (or if periodic polling of destinations is being used then whether a time-out has occurred after polling a user identified in the group database). If yes, then the router notifies the ledger application of the leave in step  66 . The notification of the leave message may include a duration of time between a join message and a corresponding leave message and a transmission count or error count, for example. A check for other users of the stream is made in step  67 . If other users exist in the group database for the particular multicast group ID then a return is made to step  61 ; otherwise the multicast routing chain is pruned in step  68  prior to returning to step  61 . 
     If a leave message is not detected in step  65 , then a check is made in step  70  for a multicast datagram being transmitted in the stream. If the packet is not a datagram, then an error may be logged in step  71  before returning to step  61 . If a datagram is present, then the router looks up the multicast group ID in step  72 . If database entries are found, then the datagram is replicated and sent to each interested destination (e.g., end users or further routers in a chain) in step  73 . If desired, the ledger application can be updated of the ongoing usage of the multicast traffic by the identified users (i.e., domains) in step  74 , and a return is made to step  61 . Preferably, any updates occur at predetermined intervals of time or predetermined amounts of data transported. 
     In an alternative embodiment of the present invention, network protocols other than the multicast protocols themselves can be used to identify the reception of multicast traffic. For example, protocols for monitoring use of copyrighted content can be employed since such content is frequently distributed in multicast streams. Thus, a user may enroll to receive a copyright restricted feed (by generating a license acknowledgement message or payment authorization, for example), and the ledger application is notified of the enrollment (together with the source and destination domains, the duration of the transmission, and an action identifier, for example).