Abstract:
Methods and apparatus for efficiently communicating across an asymmetric digital subscriber loop are disclosed. According to one aspect of the present invention, a method for communicating between a computer in a central office and a remote computer across DSL communications links involves sending a first set of data from the central office computer across a first DSL communications link. The first DSL communications link couples the central office computer to a switch. The method also includes selecting a second DSL communications link, which couples the switch and the remote computer, and sending the first set of data from the switch to the remote computer across the second DSL communications link.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates generally to methods and apparatus for communicating across a computer network. More particularly, the present invention relates to methods and apparatus for efficiently communicating across a digital subscriber loop (DSL). 
     2. Description of the Relevant Art 
     As computer usage becomes increasingly prevalent, the ability to share resources between computers has also increased. Computer systems at many different locations are often linked by a network such that information may be shared between the computer systems, e.g., data may be transferred between the computer systems. 
     Many different protocols may be used to transfer data between computer systems. By way of example, some protocols include an integrated services digital network (ISDN) and a digital subscriber loop (DSL), which are well known to those skilled in the art. Recently, due to the popularity of the Internet, as the volume of data which is transferred between computer systems increases, the demand for the ability to transfer large volumes of information in relatively short periods of time is growing. Accordingly, DSL technology is constantly being improved to address growing demands. 
     Subscriber loops, as for example DSLs, are commonly used to enable computers to communicate over a network. FIG. 1 is a diagrammatic representation of different subscriber loops in communication with a wide area network (WAN) in accordance with prior art. WAN  104  is essentially the network over which various entities  108   a-d  are allowed to communicate in order to transfer data. Entities  108   a-d  may generally include small customers, which are often “residences,” e.g., residence customer  108   a , that have computer systems and/or entertainment systems that are linked to WAN  104 . Entities  108   a-d  may also include large customers or “businesses,” e.g., business customer  108   c , which have computer systems that are in communication with WAN  104 . 
     Business customer  108   c  may often require bi-directional high speed data transfer. By way of example, business customer  108   c  may need to readily access and update databases located in WAN  104 . As such, business customer  108   c  is typically linked to WAN  104  using data lines which are capable of supporting bi-directional high speed data transfer. A T 1  line  112  may be used to link business customer  108   c  to a node  116  within WAN  104 . T 1  line  112  has a data transfer rate of up to approximately 1.544 megabits-per-second (Mbps), and uses a single wire to bi-directionally transfer data. 
     As shown, a high speed DSL (HDSL) line  120  may be used to link business customer  108   c  to a node  124  within WAN  104 . HDSL line  120 , like T 1  line  112 , has a data transfer rate of up to approximately 1.544 Mbps. However, for reliability purposes, HDSL line  120  includes two bi-directional lines which transfer data between node  124  and business customer  108   c.    
     Another type of communications link, an integrated DSL (IDSL), is created when ISDN technologies are applied to DSL. An IDSL line is capable of bi-directionally transferring data at rates of up to approximately 128 Kbps, which is typically sufficient for transmitting voice information between touch-tone (TT) phones. A first IDSL line  136  may be used to connect a TT phone associated with an entity, e.g., residence customer  108   b , across WAN  104 , to a TT phone associated with another entity, e.g., residence customer  108   d , which is connected to a second IDSL line  140 . When voice data is to be transmitted from residence customer  108   b  to residence customer  108   d , the voice data is transmitted in analog form across IDSL line  136 , which is a copper wire, to a node  144  where the voice data is digitized. The digitized voice data is then routed over WAN to another node  146 , where the digitized voice data is converted back into analog form, and sent over IDSL line  140  to residence customer  108   d.    
     Residence customer  108   a , unlike business customer  108   c , may not require bi-directional high speed data transfer, due to that fact that residence customer  108   a  is typically more likely to download information, e.g., video data for video-on-demand technologies, through WAN  104  than to upload information through WAN  104 . Accordingly, residence customer  108 a generally uses an asymmetric DSL (ADSL) connection  128  which includes a “downloading” line that is arranged transfer data downloaded from a node  132 , or a central office port, to residence customer  108   a  at rates of up to approximately 8 Mbps. ADSL connection  128  also includes an “uploading” line which is arranged to transfer data uploaded from residence customer  108   a  to node  132  at rates of up to approximately 384 kilobytes-per-second (Kbps). 
     In general, an IDSL connection is considered to be sufficient to transfer voice data between TT phones because the volume of data transfer is relatively low. However, in order to transfer data relating to the Internet, e.g., World Wide Web pages and video-on-demand data, to Internet customers such as residence customers, an ADSL connection is typically preferred over an IDSL connection. Internet usage typically involves downloading information to a computer system, as for example a computer system associated with the residence customer. Hence, since an ADSL connection is arranged to provide the capability to quickly download relatively high volumes of data to a computer system, while still enabling data to be uploaded from the computer system when necessary, an ADSL connection is particularly suitable for use by customers who generally download data. 
     Although an ADSL connection is effective for use in transferring data over the Internet, an ADSL connection typically requires a dedicated node, e.g., a dedicated central office port with an ADSL card, as well as dedicated power for each Internet customer. FIG. 2 is a diagrammatic representation of conventional point-to-point ADSL connections to a central office (CO). As shown, a system with point-to-point ADSL connections  202  includes customers  204   a-l , e.g., residences, which are each linked to a central office  206  via ADSL connections  210   a-l . Specifically, customers  204   a-l  are linked via ADSL connections  210   a-l  to dedicated ports  214   a-l  associated with central office  206 . 
     Each customer  204   a-l  generally has a point-to-point ADSL card which is connected to an appropriate ADSL connection  210   a-l . The appropriate ADSL connection  210   a-l  is connected to a point-to-point ADSL card at central office  206  (not shown) which is associated with an appropriate port  214   a-l . ADSL cards include point-to-point ADSL cards, such as those which are available commercially from Interphase Corporation of Dallas, Texas. 
     An ADSL connection, as for example ADSL connection  210   a  is generally comprised of a copper twisted pair over which data is transmitted downstream to customer  204   a , and upstream from customer  204   a  to central office  206 . Due to the fact that availability of copper wire is relatively fixed in the current communications network infrastructure, and, further, that separate ports, such as port  214   a , are required for each customer  204   a-l , the implementation of point-to-point ADSL is often expensive. 
     Since data transferred over the Internet is bursty data, as will be appreciated by those skilled in the art, ADSL connections, e.g., ADSL connections  210   a-l , are not active, or in use, much of the time. Therefore, as the full bandwidth associated with the ADSL connections is largely unused, resources associated with the ADSL connections are often essentially wasted. Further, as the length of an ADSL connection increases, the effective data transfer rate decreases. In other words, as the distances between a central office and an Internet customer increases, the data transfer rate across an ADSL connection between the central office and the customer decreases. As a result, while ADSL connections may transfer data at rates of between approximately 6 Mbps to approximately 8 Mbps, due to noise and attenuation which increase as the distance from a central office increases, many ADSL connections transfer data at substantially lower rates, as for example at approximately 384 Kbps. For example, with reference to FIG. 2, the maximum data transfer rate associated with ADSL connection  210   f , which is relatively close to central office  206 , may be approximately 6 Mbps to approximately 8 Mbps, while the maximum data transfer rate associated with ADSL connection  210   a , which is relatively far removed from central office  206 , may be approximately 384 Kbps. 
     Since the costs associated with an ADSL connection are generally high, as mentioned above, when an ADSL connection is only able to download data at rates of up to approximately 384 Kbps due to the length of the ADSL connection, the use of the ADSL connection may be considered to be inefficient. In addition, allowing an ADSL connection to a central office to remain idle while awaiting the transmission of data characterized as bursty data is an inefficient use of ADSL technology, as well as central office, resources. 
     Therefore, what is desired is an efficient method for utilizing DSL connections and central office resources, while maintaining an acceptable data transfer rate over the DSL connections, especially ADSL connections. 
     SUMMARY OF THE INVENTION 
     Methods and apparatus for efficiently communicating across a digital subscriber loop are disclosed. According to one aspect of the present invention, a method for communicating between a computer in a central office and a remote computer across DSL communications links includes sending a first set of data from the central office computer across a first DSL communications link. The first DSL communications link couples the central office computer to a switching mechanism. The method also includes selecting a second DSL communications link, which couples the switching mechanism and the remote computer, and sending the first set of data from the switching mechanism to the remote computer across the second DSL communications link. In preferred embodiments, the DSL communications links may be ADSL communications links. 
     In one embodiment, the method further includes sending a second set of data from the remote computer across the second DSL communications link to the switching mechanism, and sending the second set of data from the switching mechanism to the central office computer across the first DSL communications link. In such an embodiment, the method may include determining the availability of the first DSL communications link prior to sending the second set of data across the first DSL communications link, and delaying sending the second set of data from the switching mechanism to the central office across the first DSL communications link when it is decided that the first DSL communications link is not available. 
     According to another aspect of the present invention, an apparatus for enabling a remote computer to exchange data bi-directionally with a central office across DSL communications links includes a central office port which is associated with the central office, as well as a switching assembly which is coupled to the central office port through a first DSL communications link. The apparatus also includes a plurality of distribution links. At least one of the distribution links couples the switching assembly with the remote computer in order to facilitate the exchange of data between the central office and the remote computer through the switching assembly. In one embodiment, the central office port is associated with a first DSL card, the switching assembly is associated with a second DSL card, and the remote computer is associated with a third DSL card. In another embodiment, the first DSL communications link includes a first uploading cable for uploading the data to the central office and a first downloading cable for downloading the data to the remote computer. In such an embodiment, the selected distribution link includes a second uploading cable for uploading the data to the central office and a second downloading cable for downloading the data to the remote computer. 
     In accordance with still another aspect of the present invention, a method for transferring data from a first end point to a second end point includes transferring the data from the first end point over a first DSL communications link to a switching mechanism. A connection between the first DSL communications link and a second DSL communications link is effected using the switching mechanism, and data is transferred over a second DSL communications link to the second end point. In one embodiment, the data is transferred over the first DSL communications link at a data transfer rate of up to approximately 8 Mbps. In such an embodiment, the data transfer rate over the first DSL communications link may be in the range of approximately 384 kbps to approximately 8 Mbps. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a diagrammatic representation of different subscriber loops interfacing with a wide area network in accordance with prior art. 
     FIG. 2 is a diagrammatic representation of point-to-point ADSL connections to a central office in accordance with prior art. 
     FIG. 3 is a diagrammatic representation of “switched” ADSL connections to a central office in accordance with a first embodiment of the present invention. 
     FIG. 4 is a diagrammatic representation of a plurality of switched ADSL connections to a central office in accordance with the first embodiment of the present invention. 
     FIG. 5 is a diagrammatic block diagram representation of switched ADSL connections to a central office in accordance with the first embodiment of the present invention. 
     FIG. 6 is a diagrammatic representation of switched Ethernet connections to a central office in accordance with a second embodiment of the present invention. 
     FIG. 7 is a diagrammatic block diagram representation of switched Ethernet connections to a central office in accordance with the second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the description that follows, preferred embodiments of the invention that utilize ADSL connections will be described. The invention, however, is not limited to any one connection or hardware configuration. Accordingly, the description that follows is for illustration and not limitation. 
     Much of the data transferred over the Internet may be characterized as bursty data. Hence, ADSL connections between Internet customers and a central office are idle much of the time. Allowing ADSL connections, as well as central office ports, to remain idle may be considered to be an inefficient use of resources, since ADSL connections and dedicated central office ports are expensive to implement and maintain. In addition, the length of an ADSL connection affects the data transfer rate also decrease. As a result, data transferred across ADSL connections are often transferred at rates which are substantially lower than the maximum data transfer rates which are typically attributed to ADSL connections. 
     In order to increase the efficiency of ADSL connections, as well as to increase the available data transfer rates associated with ADSL connections which may be located relatively far from a central office, a “switched” ADSL architecture may be implemented. Implementing a switched ADSL architecture may entail the use of a switching mechanism which multiplexes a plurality of customers, or computers, to a single ADSL connection that is associated with a central office port. By multiplexing a plurality of customers to a single central office port, the customer base associated with a particular central office may be increased, thereby increasing the efficiency of the central office. Multiplexing customers through a switching mechanism enables a single ADSL connection to service a plurality of customers, thereby increasing the utilization of the available bandwidth of the ADSL connection. The use of a switching mechanism in conjunction with a shared ADSL connection also reduces the effect of the physical distance between a specific customer and a central office on the data transmission rate between the customer and the central office. 
     With reference to FIG. 3, switched ADSL connections to a central office will be described in accordance with a first embodiment of the present invention. Using a system of switched ADSL connections  302 , a single port  306  in a central office  308  may serve aplurality of customers  310   a-l . Customers  310   a-l  are generally computer service subscribers, or entities with computer systems which are in communication with a wide area network (WAN) via central office  308 . In one embodiment, customers  310   a-l  are Internet customers with central processing units (CPUs) which are linked to the Internet. 
     A shared ADSL connection  312 , or a feeder cable, is coupled to single port  306  and an ADSL switch  316 . Distribution cables  320   a-l , or individual ADSL connections, which are linked to customers  310   a-l , are used to enable data to be transferred, or otherwise exchanged, between customers  310   a-l  and ADSL switch  316 . Each distribution cable  320   a-l , together with shared ADSL connection  312 , forms a subscriber loop or, more specifically, an ADSL. It should be appreciated that although each distribution cable  320   a-l  has been represented by a single line, each distribution cable  320   a-l  is generally a twisted pair of wires, e.g., a twisted pair of copper wires. 
     As shown, the use of shared ADSL connection  310  enables single port  306  to serve twelve customers  310   a-l , thereby providing for easier management of central office  308 . The wiring, e.g., copper wiring, and the bandwidth associated with shared ADSL connection  310  are more efficiently used when shared ADSL connection  310  is used by multiple customers, since a common length of wire is shared, and the idle time of shared ADSL connection  310  is reduced. Further, the space requirements associated with central office  308  are reduced, as rather than providing a separate port and power for each customer connected to central office  308 , multiple customers may be serviced with each port. 
     The number of customers, e.g., customers  320   a-l , which may be serviced by a single port  306  typically varies as a function of the desired information downloading rate. As such, the number of customers serviced by single port  306  may generally be widely varied. By way of example, in the described embodiment, if it is desired for customers to download information at a data transfer rate of approximately 6 Mbps, then single port  306  and ADSL switch  316  may support up to approximately twelve customers. Alternatively, if information downloaded at a data transfer rate of approximately 1.544 Mbps is acceptable, then single port  306  and ADSL switch  316  may support up to approximately fifty customers. 
     In general, it should be appreciated that the data transmission rate between central office  308  and ADSL switch  316  is also a function of the length of shared ADSL connection  312 . It has been observed that splitting the length of an ADSL by placing a switch in the loop enables data to be transmitted at a relatively high data rate, e.g., approximately 6 Mbps to approximately 8 Mbps, on both ends of the split loop, whereas if the length of the ADSL is not split, the data transmission rate will generally be lower. Therefore, when loops are split, the relative lengths of distribution cables  320   a-l  have less of an effect on the rate of data transfer to customers  310   a-l.    
     ADSL switch  316  is arranged to route data between central office  308  and customers  310   a-l , and is essentially a multiplexing mechanism. When data is to be transferred from central office  308  to a specific customer, e.g., customer  310   a , when both shared ADSL connection  312  and distribution cable  320   a  are free, the data is then routed across shared ADSL connection  312 , through ADSL switch  316 , and across distribution cable  320   a  to customer  310   a . In one embodiment, ADSL switch  316  may be arranged to determine the availability of distribution cables  320   a-l , wait for the appropriate distribution cable to become available, then transfer data across the free distribution cable. The routing of data between central office  308  and customers  300   a-l  will be described in more detail below with respect to FIG.  5 . 
     In one embodiment, ADSL switch  316  may include buffers including a buffer that is arranged to hold data transferred across shared ADSL connection  312 . Such a buffer may hold the data until the appropriate distribution cable, as for example distribution cable  320   b , is available for data transfer. When distribution cable  320   b  is available, then data held in the buffer may be transferred over distribution cable  320   b . In other words, if a customer such as customer  310   a  sends data to central office  308  over distribution cable  320   a , but shared ADSL connection  312  is unavailable, then the buffer may store the data. 
     In general, components used in ADSL switch  316  may be widely varied. ADSL switch  316 , in one embodiment, may include switch components, or cards, such as those available commercially from I 3  of San Jose, Calif. ADSL switch  316  may further include ADSL cards, such as those which are often used for conventional point-to-point ADSL architectures. Each distribution cable  320   a-l  may be associated with an ADSL card within ADSL switch  316 . Suitable ADSL cards include, but are not limited to, ADSL cards which are available commercially from Interphase of Dallas, Tex. Typically, an ADSL card, or unit, is also included at port  306 , and at each customer  310   a-l . In one embodiment, ADSL switch  316  may include a switch component and an ADSL card on a single motherboard. 
     In general, central office  308  may include any number of systems of switched ADSL connections  302 . FIG. 4 is a diagrammatic representation of a plurality of systems of switched ADSL connections to central office  308  in accordance with the first embodiment of the present invention. Each system  302 ,  402 ,  403 ,  404  includes an ADSL switch  316 ,  416 ,  417 ,  418 , respectively. ADSL switches  316 ,  416 ,  417 ,  418 , in turn, are each coupled to a separate port  306 ,  406 ,  408 ,  410  through a shared ADSL connection  312 , 420 , 422 , 424 , respectively. 
     As shown, each port  306 ,  406 ,  408 ,  410  in central office  308  may support multiple customers, e.g., twelve customers. Therefore, the capacity of customers which may be served by central office  308  may be increased by providing each port  306 ,  406 ,  408 ,  410  with the capability to support more than one customer. Further, in addition to reducing the number of ports necessary to support a given customer base, the volume of wire which is needed to support the customer base is reduced through the use of shared ADSL connections  312 ,  420 ,  422 ,  424 . In general, the number of ports and, also, the number of switches linked to central office  308  is dependent on a variety of different factors, including, but not limited to, the performance and quality levels which are considered to be acceptable. 
     Referring next to FIG. 5, the routing of data between central office  308  and customers  310   a-l , as shown in FIG. 3, will be described in accordance with the first embodiment of the present invention. In other words, the routing of data from a wide area network (WAN), which includes central office  308 , across ADSL connections will be described. Data is transferred between central office  308  and customers  310   a-c  over a bus, as for example a Peripheral Component Interconnect (PCI) protocol bus  512 , which includes ADSL connections and distribution cables. The transfer of data between central office  308  and a customer, i.e., one of customers  310   a-c , is bi-directional. That is, data may be transferred from central office  308  to a customer across PCI bus  512 , and data may be transferred from a customer to central office  308  across PCI bus  512 . 
     In general, the rate at which data may be transferred between central office  308  and customers  310   a-c  may vary depending upon factors including the number of customers associated with central office  308 . As such, the data transfer, or exchange, rate may be widely varied. In one embodiment, the data transfer rate associated with downloading data from central office  308  to customers  310   a-c  may be up to approximately 8 Mbps, as for example in the range of approximately 6 Mbps to 8 Mbps, or in the range of approximately 128 Kbps to approximately 1.544 Mbps. In such an embodiment, the data transfer rate associated with uploading data from customers  310   a-c  to central office  308  may be up to approximately 384 Kbps, as for example in the range of approximately 32 Kbps to approximately 384 Kbps. It should be appreciated that although the data transfer rate associated with transferring data between ADSL switch  316  and central office  308  is generally substantially the same as the data transfer rate associated with transferring data between ADSL switch  316  and customers  310   a-c , the data transfer rates may also be varied. 
     When a customer, as for example customer  310   a , wishes to download data via central office  308 , central office  308  may process, e.g., route, data using an ADSL card  516 . From ADSL card  516 , data is transferred through ADSL switch  316  and a CPU  524  which are coupled together. CPU  524  generally executes software which allows the components within ADSL switch  316  to essentially multiplex or demultiplex data, as appropriate. 
     As shown, customer  310   a  has a browser  526  on which data transferred from central office  308  may be viewed. In one embodiment, browser  526  may be arranged to display video data requested using video-on-demand applications. It should be appreciated that customers may generally be arranged to download data from central office  308  for a variety of different purposes. By way of example, customers  310   b ,  310   c  may include CPUs  530   a ,  530   b , respectively, which are arranged to process data obtained from central office  308 . It should be appreciated that CPUs  530   a ,  530   b  may be coupled to any suitable computer storage media, e.g., disks, such that data obtained from central office  308  may be stored. 
     ADSL switch  316 , which includes ADSL cards and a switch card as mentioned above, together with CPU  524 , serves to route data transferred from central office  504  through PCI bus  512  to the appropriate receiving customer, e.g., customer  310   a . In other words, ADSL switch  316  essentially functions as a de-multiplexer. From ADSL switch  520  and CPU  524 , data is transferred to an ADSL card  528   a  that is associated with, or otherwise linked with, receiving customer  310   a . Once data is downloaded to customer  310   a , the data may be displayed accordingly on browser  526 . 
     Similarly, when data is to be uploaded from customer  310   a  to central office  308 , the data is processed by ADSL card  528   a , and routed over PCI bus  512 , e.g., a distribution cable associated with PCI bus  512 , to ADSL switch  316  and, hence, CPU  524 . When data is uploaded from customer  310   a , ADSL switch  316  basically multiplexes the data and routes the data to central office  308  when PCI bus  512  is available, i.e., available for routing the data to central office  308 . 
     As previously mentioned, allowing an ADSL connection and a single port associated with a central office to be shared by a plurality of customers increases the use of the available bandwidth of a given ADSL connection. A shared ADSL connection also allows the overall data transfer rate of a given customer base to be increased over a given loop length. In order to further increase the transfer rate of data transferred over a given loop length, a “fat pipe” may be implemented within the loop. That is, Ethernet traffic may be carried via a fat pipe, which is generally multiple pairs of wire over which data may be transferred, as will be appreciated by those skilled in the art. In one embodiment, multiple wires may be used to allow data to be substantially simultaneously transferred over the wires. The implementation of a fat pipe, therefore, increases the rate at which data, such as Internet data, may be transferred between a central office and a customer. 
     Although a fat pipe may generally be used as either a distribution cable or a feeder cable, in one embodiment, a fat pipe is used as a feeder cable. FIG. 6 is a diagrammatic representation of a customer base which is in communication with a central office through switched connections to a fat pipe in accordance with a second embodiment of the present invention. A customer base with switched ADSL connections  602  is linked to a single port  606  in a central office  608 . In general, port  606  in central office  608  may serve multiple customers  610   a-l . Distribution cables  620   a-l  link customers  610   a-l , respectively, to an ADSL switch  626 . A fat pipe assembly  630  serves as a feeder cable to link port  606  of central office  608  to ADSL switch  626 . Hence, Ethernet traffic may essentially be carried between port  606  and customers  610   a-l , using fat pipe assembly  630 . 
     In general, fat pipe assembly  630  includes a plurality of pairs wires which enable data to be transferred over a plurality of wires at the same time. It should be appreciated that the amount of time associated with transferring a fixed amount of data may decrease as the number of wires increases. As data is essentially sent over fat pipe assembly  630  in series form, data must generally be reconstructed after it is sent over fat pipe assembly  630 . In one embodiment, fat pipe assembly  630  may include mechanisms which allow data being transferred across the plurality of data lines in fat pipe assembly  630  to be synchronized such that after data is received at one end of fat pipe assembly  630 , the data may be reconstructed into its original form. 
     The flow of traffic through fat pipe  620  and distribution cables  620   a-l  will be described in accordance with FIG. 7, which is a representation of switched Ethernet connections to central office  608  in accordance with the second embodiment of the present invention. That is, the routing of data from a wide area network (WAN), which includes central office  608 , across Ethernet connections will be described. Data is transferred between an Ethernet port  636 , central office  608 , and customers  610   a-c  using a bus, as for example a PCI protocol bus  642  which include distribution cables. Data that is being transferred may take on many suitable forms. By way of example, the data may be embodied as a carrier wave for transfer over bus  642 . 
     The transfer of data between central office  608  and a selected customer  310   a-c  is largely bi-directional. That is, data may be downloaded from central office  608  to a customer across bus  642 , and data may be uploaded from a selected customer  610   a-c  to central office  608  across bus  642 . 
     When a customer, as for example customer  610   a , wishes to download data via central office  608 , central office  608  may process, e.g., route, data using a data synchronizing mechanism  650 , or a synchronizing N-media access (N-MAC) controller. In general, synchronizing mechanism  650  includes data buffers which are used to synchronize data over different wires  654   a-c  which are associated with fat pipe assembly  630 . It should be appreciated that data may be synchronized for transport and “de-synchronized” for receipt. Synchronizing mechanism  650  may further be arranged to correct for crossed wires, e.g., wires  654   a-c.    
     Data is transferred across wires  654   a-c  associated with fat pipe assembly  630 . Wires  654   a-c  are each coupled to a selected ADSL card  656   a-c , as shown. From ADSL cards  656   a-c , data is transferred through wires  660   a-c  to ADSL cards  664   a-c , respectively. From ADSL cards  664   a-c , data is transferred across wires  668   a-c  to a data synchronizing mechanism  672 . Like data synchronizing mechanism  650 , data synchronizing mechanism  672  generally includes data buffers, and is arranged to synchronize and desynchronize data as necessary. Data synchronizing mechanism  672  is coupled to bus  642 , and serves to transfer data to bus  642 . 
     ADSL switch  626  and a CPU  676  are coupled together on bus  642 . In one embodiment, CPU  676  generally executes software which allows the components within ADSL switch  626  to essentially multiplex or demultiplex data, as appropriate. Components in ADSL switch  626  generally include ADSL cards and a switch card. ADSL switch  626 , together with CPU  676 , routes data transferred from central office  608 , through fat pipe assembly  630  and bus  512  to the appropriate receiving customer, e.g., customer  610   a . From ADSL switch  626  and CPU  676 , data is transferred to an ADSL card  680   a  that is associated with receiving customer  610   a . In general, data may be transferred to the appropriate ADSL card  680   a-c  for a selected receiving customer  610   a-c , as will be appreciated by those skilled in the art. 
     When data is to be uploaded from customer  610   a  to central office  608 , the data is processed by ADSL card  680   a , and routed over bus  642 , e.g., a distribution cable associated with bus  642 , to ADSL switch  626  and, hence, CPU  676 . From ADSL switch  626  and CPU  676 , data is transferred to synchronizing mechanism  672 , which processes the data and sends the data over lines  668   a-c  to ADSL cards  664   a-c . From ADSL cards  664   a-c , data is transferred over wires  660   a-c  to ADSL cards  656   a-c . Final, the data is sent over wires  654   a-c  to synchronizing mechanism  650  and Ethernet port  636 , which is associated with central office  608 . 
     Although only a few embodiments of the present invention have been described, it should be understood that the present invention may be embodied in many other specific forms without departing from the spirit or the scope of the present invention. By way of example, while the ADSLs of the present invention have been discussed in terms of being implemented with wires such as copper wires, the ADSLs may also generally be implemented using any suitable material. Suitable materials may include, but are not limited to, various fibers without departing from the spirit or the scope of the present invention. 
     The use of ADSL switches has been described in association with using a single ADSL switch, or an “initial” ADSL switch, to enable a single port in a central office to be used by a shared ADSL connection. However, “secondary” ADSL switches, which enable multiple customers to be linked to a previously “individual” distribution cable, may be implemented in addition to the initial ADSL switch without departing from the spirit or the scope of the present invention. That is, secondary switches may be implemented to allow distribution cables between a customer site and an initial ADSL switch to be shared. In such an implementation, a secondary ADSL switch may be shared by multiple customers and, in turn, multiple secondary ADSL switches may be linked to an initial ADSL switch. Implementing secondary switches may generally be effective in increasing the customer base which may be supported by a given central office. However, in some embodiments, the use of secondary switches may compromise the performance and quality of data transfer between a central office and a customer. Therefore, the present examples 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 of the appended claims.