Patent Abstract:
A integrated circuit device for use in a line card of a digital networking system is capable of intercepting one or more control messages corresponding to a requested data channel sent from at least one customer premises equipment (CPE) device. The integrated circuit device is also capable of receiving a plurality of data channels from a data server of the digital networking system and providing the one or more requested data channels to the at least one CPE device, thereby providing faster data channel selecting and switching capabilities.

Full Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of digital networking systems and, more particularly, to improved techniques for providing data channels to end users in a digital network. 
     BACKGROUND OF THE INVENTION 
     Traditional data channel transmission techniques include for example, data channel multicasting, which may be employed in a digital subscriber line access multiplexer (DSLAM) network. A DSLAM network provides an end user, at a terminal or other endpoint, with the ability to switch between streams of data, or data channels, received from an upstream source. A DSLAM network is typically designed to accommodate a variety of different types of data channels, such as, for example, a number of video channels as well as channels associated with user data, voice and gaming traffic. The endpoints of a DSLAM platform are customer premises equipment (CPE) devices, which are commonly accessed by the network through modems at a residence or business. CPE devices may include, for example, televisions, computers, personal digital assistants (PDAs), telephones or other types of communication terminals. A DSLAM network enables the delivery of any of the available channels to an end user while simultaneously allowing the end user to use the data, voice and gaming channels. 
     An end user may select one data channel from a set of channels that are broadcasting at a given time. An Internet group multicast protocol (IGMP) signal has traditionally been used to effect this channel selection by sending an IGMP control message from the CPE device of the end user through the DSLAM network and to a broadband remote access server (B-RAS). The channel selection is conveyed upstream in order to effect the switch to a newly selected channel. Since the signal has to travel from the CPE device, and through the network to the B-RAS, the time required to effect the channel change is usually fairly long. In DSLAM applications utilizing a central office (CO), the CO in the network polls for IGMP control messages. A CO may support a large number of CPEs, thus, IGMP consolidation presents a significant challenge to the efficiency of the system. 
     Attempts to solve the problems of channel switching time and IGMP control message consolidation have resulted in the use of software controlled selective channel switching in an uplink card of the CO. In such attempts, channel switching time is reduced by receiving at the uplink card, those video channels considered popular, thereby anticipating end user requests. The channel switching speed between channels in this subset of popular channels is increased. However, the time required to join, or to switch to, channels that are not considered popular and have not been received at the uplink card, will remain fairly long. This is due to the fact that the IGMP control message for the unpopular channel travels back to the B-RAS so that the channel may be transmitted to and received at the uplink card of the CO. 
     These attempts also result in an additional delay within the CO. A line card in the CO sends the control message to the uplink card, which processes the control message. A delay occurs in this transmission due to the fact that a more complex switching is required in the CO instead of a simple broadcast of the data channels from the upstream equipment. Finally, IGMP control messages are also periodically generated from the CPE devices to ensure connectivity within the network. This connectivity check has the ability to flood the network with control messages. 
     Thus, a need remains for a technique that enables faster selection and switching of channels of a digital networking system, as well as a technique for decreasing the number of control messages sent over the network. 
     SUMMARY OF THE INVENTION 
     The present invention in an illustrative embodiment provides a digital networking system that transmits data channels to end users through an effective data channel selection and switching technique. 
     In accordance with one aspect of the invention, an integrated circuit device for use in a line card of a digital networking system is capable of intercepting one or more control messages from at least one CPE device corresponding to one or more requested data channels. The integrated circuit device is also capable of receiving a plurality of data channels from a data server of the digital networking system and providing the one or more requested data channels to the at least one CPE device. 
     An apparatus in accordance with this aspect of the present invention, used in a network node of digital networking system, comprises at least one line card. The line card comprises an integrated circuit device that is capable of intercepting one or more control messages from at least one CPE device corresponding to one or more requested data channels. The integrated circuit device is also capable of receiving the plurality of data channels from the data server of the digital networking system and providing the one or more requested channels to the CPE device. 
     A method of providing a data channel to a CPE device in a digital networking system in accordance with this aspect of the present invention comprises the receiving of a plurality of data channels at each of one or more line cards from a data server of the digital networking system. One or more control messages are intercepted, each corresponding to a requested data channel from the CPE device, at one or more line cards. The one or more requested data channels are provided to the at least one CPE device from the line card through a integrated circuit device of the line card. 
     Advantageously, an illustrative embodiment of the present invention ensures faster channel selection and switching. Each data channel is fed to the DSLAM central office and to the individual line cards, so that the channel switching time delay will be identical for all available data channels. The embodiments of the present invention may take advantage of large capacity backplane devices and an access network. By intercepting the control message at the line card, this architecture eliminates communication delay between the CO and the far-end data server, B-RAS. The processing delay involved in effecting the channel switchover is also reduced. Finally, the embodiments of the present invention prevent control messages from flooding the network. 
     These and other objects, features, and advantages of the present invention will become apparent from the following detailed description of the illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a DSLAM network, according to an embodiment of the present invention; 
         FIG. 2  is a diagram illustrating a general DSLAM central office architecture, according to an embodiment of the present invention; 
         FIG. 3  is a diagram illustrating a more detailed example implementation of the  FIG. 2  arrangement, according to an embodiment of the present invention; 
         FIG. 4  is a table illustrating channel selection at CPE devices in a DSLAM network, according to an embodiment of the present invention; 
         FIG. 5  is a diagram illustrating function blocks of an FPGA device in a DSLAM network, according to an embodiment of the present invention; and 
         FIG. 6  is a flow diagram illustrating a channel selection or switching methodology in a DSLAM network, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As will be described in detail below, the present invention in the illustrative embodiment relates generally to the field of digital networking systems and, more particularly, to improved techniques for providing data channels to end users in a digital network. 
     Referring initially to  FIG. 1 , a diagram illustrates a DSLAM network, according to an embodiment of the present invention. A plurality of data channels, for example, video channels, are sent from the far end of the network at B-RAS  102 , through a core network  104  and into an access network  106 . Core network  104  is in communication with access network  106  through an edge router  108 . Edge router  108  may communicate with a network node, or more specifically, CO  116 , through a metro core  110  of access network  106  via an asynchronous transfer mode (ATM)  112 , synchronous optical network (SONET) or synchronous digital hierarchy (SDH)  114 . SONET is the United States version of synchronous data transmission over fiber optic networks, while SDH is the international version of the standard. Edge router  108  may provide communication to and from several DSLAM central offices through metro core  110  of access network  106 . DSLAM central office  116  is in communication with DSL modems  118  at residences  120  and businesses  122  for use, for example, with a television  124 , computer  126 , or telephone  128 . 
     Through the DSLAM network provided in  FIG. 1 , the plurality of data channels may be transmitted to CO  116  for individual distribution to CPE devices  124 ,  126  and  128 , through DSL modems  118 , in response to control messages sent from CPE devices  124 ,  126  and  128 , to B-RAS  102 , and intercepted by CO  116 . 
     Referring now to  FIG. 2 , a diagram illustrates a general DSLAM central office architecture, according to an embodiment of the present invention. This may be considered a more detailed view of DSLAM central office  116  of  FIG. 1 . An uplink card  202  communicates with at least one line card  204   a ,  204   b . In this embodiment, uplink card  202  provides communication with upstream components of the DSLAM network through, for example, gigabit media independent interface (GMII) or serial media independent interface (SMII), through, for example, optical carrier  12  (OC-12, 622.08 Mbps) or optical carrier  3  (OC-3, 155.52 Mbps), at ATM or multi-protocol network processor  206 . 
     Network processor  206  may communicate with a backplane device  208  or a switching fabric  210  within uplink card  202 . Uplink card  202  having backplane device  208 , and uplink card  202  having switching fabric  210 , represent two separate embodiments of the present invention. If backplane device  208  is implemented in uplink card  202 , uplink card  202  communicates with one or more line cards  204   a , each having a backplane device  212 . Backplane device  212  may utilize a processor  214  in order to implement the invention. Backplane device  212  communicates with DSL modems through DSL modem stations  216 . The communication through DSL modem stations allows CPE devices to provide signals for interception by line card  204   a , and allows line card  204   a  to transmit a requested data channel to a requesting CPE device. 
     If switching fabric  210  is implemented in uplink card  202 , uplink card  202  communicates with one or more line cards  204   b , each having a universal bridge (UB)  218 . Universal bridge  218  utilizes a processor  220  in implementing the invention and communicating with DSL modem stations  216  of line card  204   b . DSL modem stations  216 , modems and CPE devices perform similar functions in embodiments utilizing line cards  204   a  and  204   b.    
     As shown in  FIG. 3 , a diagram illustrates a more detailed example implementation of the  FIG. 2  arrangement, according to an embodiment of the present invention. More specifically, this may be considered a detailed description of the general DSLAM central office architecture implementing a switching fabric in an uplink card. An uplink card  302  receives data channels and communicates user traffic through a network processor  306 , which corresponds to network processor  206  in  FIG. 2 . Network processor  306  may be implemented as part APP550, commonly available from Agere Systems Inc., of Allentown, Pa., USA. Network processor  306  is in communication with a UB  308 , which communicates with switching fabric  310 . In this embodiment of the present invention, UB  308  may be implemented as part UB2G5NP and switching fabric  310  may be implemented as parts PI40SAX, PI20SAX, which are also commonly available from Agere Systems Inc. Uplink card  302  also includes a clock  312 . Uplink card  302  transmits channels to one or more line cards  304 , while also receiving necessary user traffic. 
     In line card  304   a , a UB  314   a  communicates with uplink card  302  through switching fabric  310 . UB  314   a  is also in communication with FPGA  318   a  and microprocessor  320   a  within line card  304   a  in order to implement the invention. Line card  304   a  communicates with modems  316  through FPGA  318   a . The channels are transmitted to FPGA  318   a  from uplink card  302  and a control message is transmitted to FPGA  318   a  from a modem  316 . A similar communication system exists with regard to line card  304   b , UB  314   b , FPGA  318   b , and microprocessor  320   b . Both line cards  304   a ,  304   b  also include respective clocks  322   a ,  322   b.    
     FPGA  318   a ,  318   b  in communication with processor  320   a ,  320   b  may be considered a management device of line card  304   a ,  304   b . Such a management device of the line card may be viewed as one example of an integrated circuit device that implements the present invention. The management device maintains a table, as shown in  FIG. 4 . The table may be stored in an internal memory of the management device or an associated external memory. The table illustrates the channel selection at CPE devices for a specific line card. This table is used to provide and manage requested data channels for appropriate end users. When an end user at a CPE device switches a channel, the CPE device generates a control message, for example, IGMP, that is intended to be destined to the far-end server, B-RAS. The management device in the line card of the CO intercepts the control message and uses it to dynamically update the table and provide the requested channel to the CPE device. The management device is able to provide the data channel because every data channel is transmitted to the CO and transmitted to the individual line cards that comprise the management device. 
     The table is updated dynamically, utilizing in this embodiment a one-to-one signaling between the CPE device and the management device. An identification number of the data channel must be obtained from the control message sent from the CPE device. The table maintains the data channel ID, for example, a TV channel number, of the data channel requested by and transmitted to the CPE device. In addition, the table includes an enable/disable bit for each CPE device associated with the line card, to indicate whether it is on or off. The port column in the table represents the DSL modems at each residence or business. The table in  FIG. 4  illustrates 124 modems, each capable of supporting 4 CPE devices, for example, 4 set-top channel boxes in each house. Additional embodiments of the management device of the line card may maintain a table having 48 or 64 DSL modems. 
     Referring now to  FIG. 5 , a block diagram illustrates functional blocks of an FPGA device, according to an embodiment of the present invention. This may be considered a detailed description of FPGA device  318  in  FIG. 3 . A downstream signal is received at a UB receive interface block  510  from a UB, which may implemented as part UB2G5, commonly available from Agere Systems Inc. UB receive interface block  510  maintains the table indicating the channel selection at the CPE devices, as well as a cell header translation table if required. Capture FIFO  512 , extracts a signal generated from the UB for back pressure control purposes, as will be described below, and transmits to the microprocessor interface. A UB to modem interface block  514  receives transmissions from UB receive interface block  510  and provides transmission of requested channels to requesting CPE devices through modems. 
     If a modem&#39;s receive interface suffers from congestion, the modem should ignore the FPGA device&#39;s polling to avoid overflow in the modem. Specifically, when back pressure comes from the modem TXCLAV, the FPGA device should not send traffic to the modem and should maintain individual per port back pressure status. If the FPGA device suffers from congestion, it will generate a flow control message RENB and send it upstream. 
     A multi physical layer (MPHY) receive interface block  518  receives control messages from the CPE devices through modems. A modem to UB interface block  520  receives a transmission from MPHY receive interface block  518  and generates TM cells for transmission to UB2G5. Insertion FIFO  522  inserts a control message generated from a back pressure control block  516  and from the microprocessor. A polled-PHY transmit packet available (PTPA) is also received at modem to UB interface block  520  from the UB. 
     As shown in  FIG. 6 , a flow diagram illustrates a channel selection or switching methodology at a line card of a DSLAM network, according to an embodiment of the present invention. The methodology begins in block  610  where a plurality of data channels are received at each of one or more line cards from a data server of the digital networking system. In block  612 , one or more control messages, each corresponding to a requested data channel and from a CPE device, are intercepted at one or more line cards. In block  614 , a table relating to requested data channels and requesting CPE devices is dynamically updated through the integrated circuit device of the line card. Finally, in block  616 , one or more requested data channels are provided to one or more CPE devices from one or more line cards through an integrated circuit device of each line card, terminating the methodology. The methodology may repeat for each control message received at each line card in the DSLAM network. 
     Accordingly, as described herein, the present invention in the illustrative embodiment provides data channels to end users of a network through an effective data channel selection and switching technique. 
     Additional embodiments of the present invention may incorporate multiple numbers and combinations of COs, DSL modems and CPE devices. These embodiments may also incorporate different numbers and combinations of line cards associated with a single uplink card in the COs. The tables described above in each line card are based on the number of modems the line card communicates with and the number of CPE devices associated with each modem. Therefore, the number of ports and channels provided in the table may also differ in additional embodiments. In a specific embodiment of the present invention an ASIC device may be utilized in place of the FPGA device. Further, proprietary signaling from another application may be utilized in place of IGMP. The invention may be implemented when any type of control message is used. Finally, the invention is not limited to uplink card-line card configurations in the CO of the illustrative embodiments. The invention may also apply to single hierarchy configurations where only a line card is utilized. 
     As discussed above, the management device of the present invention may be considered an integrated circuit device. Regarding integrated circuits in general, a plurality of identical die are typically formed in a repeated pattern on a surface of a semiconductor wafer. Each die may include other structures or circuits. The individual die are cut or diced from the wafer, then packaged as an integrated circuit. One skilled in the art would know how to dice wafers and package die to produce integrated circuits. Integrated circuits so manufactured are considered part of this invention. 
     Therefore, although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be made by one skilled in the art without departing from the scope or spirit of the invention.

Technology Classification (CPC): 7