Patent Publication Number: US-10771834-B2

Title: Personalized content

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of and claims the benefit of priority to U.S. patent application Ser. No. 15/703,931 filed Sep. 17, 2017 which is a continuation of and claims the benefit of priority to U.S. patent application Ser. No. 15/219,970 filed Jun. 26, 2016 now U.S. Pat. No. 9,788,038, which is a continuation of and claims the benefit of priority to U.S. patent application Ser. No. 14/523,158 filed Oct. 24, 2014 now U.S. Pat. No. 9,414,103, which is a continuation of and claims the benefit of priority to Ser. No. 11/563,663 filed Nov. 27, 2006 now U.S. Pat. No. 8,893,196, which is a continuation of and claims the benefit of priority to U.S. patent application Ser. No. 10/329,766, filed Dec. 27, 2002 all of which are incorporated herein by reference in their entirety. This application also incorporates by reference U.S. Provisional Application No. 60/286,964, titled “Generating Multiple Data Streams from a Single Content Source” and filed Apr. 30, 2001; U.S. Provisional Application No. 60/343,182, titled “Duplicating Digital Streams for Digital Conferencing Using Switching” and filed Dec. 1, 2001; U.S. Provisional Application No. 60/373,329, titled “Stream Management” and filed Apr. 18, 2002; U.S. application Ser. No. 09/893,692, titled “Generating Multiple Data Streams from a Single Content Source” and filed Jun. 29, 2001; U.S. application Ser. No. 10/090,727, titled “A Duplication Switch for Streaming Data Units to a Terminal” and filed Mar. 6, 2002; U.S. application Ser. No. 10/134,439, titled “Duplicating Digital Steams for Digital Conferencing Using Switching Technologies” and filed Apr. 30, 2002; and U.S. application Ser. No. 10/134,552, titled “Managing Access To Streams Hosted on Duplicating Switches” and filed Apr. 30, 2002. 
    
    
     TECHNICAL FIELD 
     This application relates to networking. 
     BACKGROUND 
     Content may be distributed through a cable system by a cumbersome collection of tapes, modulators, and filters that may be referred to as legacy infrastructure. Generally, this legacy infrastructure poses challenges to the implementation of next-generation services. Typically, the legacy infrastructure maps content analogous to television station signals onto the spectrum of a cable. While content may be delivered through other delivery mechanisms, the legacy infrastructure represents an enormous investment, which makes a system capable of offering next-generation services through this legacy infrastructure desirable. 
     SUMMARY 
     In one general sense, requested content may be accessed by receiving a content request from a terminal for a first piece of content to be distributed over a cable system and identifying a personal channel within resources available in the cable system to distribute the first piece of content to the terminal. Access information may be transmitted to the terminal to enable the terminal to access the first piece of content through the personal channel. A cable headend may be interfaced with to provide the first piece of content on the personal channel. 
     Implementations may include one or more of the following features. For example, the personal channel may be dedicated to a single terminal and may include a modulated channel of the cable system. The personal channel may be accessed by tuning to a frequency and accessing data having a particular process identification number and transmitted at the frequency. The first piece of content may include non-video content. The first piece of content may be accessed by adding terminal address information to a list of addresses supported by a broadcasting switch and/or an on-demand switch. Adding terminal address information to the list of addresses supported by the on-demand switch may include adding a play marker indicating the temporal location of the terminal in receiving the first piece of content. 
     Implementations may include a system and program capable of achieving the above features. Implementations also may include a sequence of steps performed on a media switch. The media switch may include a broadcasting switch and an on-demand switch. Other features will be apparent from the following description, including the drawings, and the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of a communications system capable of using a duplicating switch to generate a stream of data units. 
         FIG. 2  is an exemplary component diagram of a duplicating switch suitable for use in the communications system of  FIG. 1 . 
         FIG. 3A  is an exemplary block diagram of a duplicating switch that uses memory to store a media stream for subsequent playback. 
         FIG. 3B  is an exemplary block diagram of a duplicating switch that uses storage to store a media stream for subsequent playback. 
         FIG. 4  is a block diagram of a precoder for use in a duplicating switch. 
         FIG. 5  is a flow chart of a procedure for processing a received data unit using a duplicating switch in a communications system, such as the communications system of  FIG. 1 . 
         FIG. 6  is a flow chart of a procedure for providing a stream of data units in a communications system, such as the communications system of in  FIG. 1 . 
         FIG. 7A  illustrates a duplicating switch structured and arranged to store multiple instances of a stream of data units. 
         FIG. 7B  illustrates a duplicating switch structured and arranged to store multiple location identifiers. 
         FIG. 8  is a flow chart of a procedure for time-shifting content in a communications system, such as the communications system of  FIG. 1 . 
         FIG. 9  is a diagram of a cable system that may be used to distribute personalized content through a cable system. 
         FIG. 10  is a block diagram of a media switch that may enable access to personalized content in a cable system. 
         FIG. 11  is a frequency spectrum diagram that shows how content may be mapped over a cable system. 
         FIG. 12  is a flow chart showing how a cable system may enable a terminal to access personalized content from a media switch through a cable system. 
         FIG. 13  is a flow chart showing how a terminal may access a particular episode by interfacing with a media switch through a cable headend. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. For brevity, several elements in the figures described below are represented as monolithic entities. However, as would be understood by one skilled in the art, these elements each may include numerous interconnected computers and components designed to perform a set of specified operations and/or dedicated to a particular geographical region. 
     DETAILED DESCRIPTION 
     In general, a media switch interfaces with a terminal across a cable system to enable personalized access to content. When the media switch receives a content request for a first piece of content over the cable system, the media switch relates the content request to one or more available resources to determine if the content may be accessed from an existing resource. If the content request may be accessed from an existing resource, the media switch transmits access information to the terminal so that the terminal may use the existing resource to access the content indicated in the content request. If the content is not available from an existing resource, the content may be sent to the terminal over the cable system. 
     Also, a media switch may enable a terminal to access a personalized channel on a cable system. The media switch may receive a content request and enable the terminal to access the requested content over the personalized channel. The personalized channel may be created by exchanging location information (e.g., a frequency and a process identification number) indicative of where the terminal may access the personalized content on the cable system. 
     For illustrative purposes,  FIGS. 1-8  describe a communications system that uses a duplicating switch to stream data units to a terminal. For illustrative purposes,  FIG. 1  depicts a communications system  100  that implements techniques using a duplicating switch to stream data units to two or more terminals. Communications system  100  may be structured and arranged to include a source system  110 , one or more terminals  150 , and communication software and hardware that enable communications between source system  110  and terminals  150 . More particularly, the communications system  100  typically includes the source system  110 , a network  120 , a duplicating switch  130 , a network  140 , and terminals  150 . In actual implementations, the source system  110  generally transmits one or more data units in a stream of data units across network  120  to one or more duplicating switches  130 . The duplicating switches store, duplicate and transmit content from the data units to one or more terminals  150  through network  140  in an on-demand manner. 
     The source system  110  provides the duplicating switch  130  with a stream of one or more data units across the network  120 . Typically, the source system  110  is structured and arranged to convert a media source (e.g., a video or audio feed) into data units for transmission across the network  120 . The source system  110  may include a general-purpose computer having a central processor unit (CPU), and memory/storage devices that store data and various programs such as an operating system and one or more application programs. Other implementations of the source system  110  include a workstation, a server, a device, a special purpose device or component, other equipment, or some combination thereof capable of responding to and executing instructions in a defined manner. The source system  110  also typically includes an input/output (I/O) device (e.g., video and audio input and conversion capability), and peripheral equipment such as a display communications card or device (e.g., a modem or a network adapter) for exchanging data with the network  120 . 
     Implementations of the source system  110  also may include a media system that transmits one of more pieces of media content across a network  120 . For example, a source system  110  may transmit across a network to a cable headend signals formatted according to European Telecommunications Standards Institute (ETSI), Digital Video Broadcasting (DVB), Advanced Television Systems Committee (ATSC), or European Cable Communications Association (ECCA) standards. In another implementation, a cable provider may transmit or direct video signals to a cable headend for distribution in a cable network. 
     A communications link  115  is used to communicate data between source system  110  and network  120 . Communications link  115  may include wired or wireless modes of communication, such as a telephone line, a wireless network link, a cable network, or a direct connection. 
     The network  120  typically includes hardware and/or software capable of enabling direct or indirect communications between the source system  110  and the duplicating switch  130 . The network  120  may include a direct link between the source system  110  and the duplicating switch  130 , or it may include one or more networks or subnetworks between them (not explicitly shown). Each network or subnetwork may include, for example, a wired or wireless data pathway capable of carrying and receiving data. Examples of network  120  include the Internet, the World Wide Web, WANs (“Wide Area Network”), LANs (“Local Area Networks”), analog or digital wired and wireless telephone networks (e.g., PSTN (“Public Switched Telephone Network”), ISDN (“Integrated Services Digital Network”), or xDSL (“any form of Digital Subscriber Loop”)), radio, television, cable, satellite, and/or other delivery mechanisms for carrying data. 
     Generally, the duplicating switch  130  is structured and arranged to store a received stream of data units for time-shifted transmission to more than one terminal. Implementations of the duplicating switch  130  may store one or more streams of data units. For example, the duplicating switch  130  may be capable of receiving a stream of IP (“Internet Protocol”) video and storing that video for subsequent transmission. Implementations of duplicating switch  130  also may include hardware or software capable of transmitting or receiving media feeds not resembling a stream of data units. For example, the duplicating switch may include a cable headend system that is capable of receiving or transmitting signals formatted according to ETSI, DVB, ATSC, or ECCA standards for transmission on a cable distribution system. The cable headend system may receive a satellite broadcast feed, convert the feed into a format suitable for storage, and thereafter convert the feed back to a different format for time-shifted transmission. 
     The network  140  generally includes one or more of links between the duplicating switch  130  and the terminals  150 . For example, the network  140  may include a direct physical link or a series of links connected by various pieces of network equipment. Generally, aspects of network  140  may resemble aspects of network  120 . For example, network  120  and network  140  may share one or more hardware or software devices. In another example, networks  120  and  140  may use the same type of circuits and/or equipment. 
     The terminal  150  may include one or more devices capable of receiving the stream of data units transmitted by duplicating switch  130  through network  140 . The terminal  150  may include a controller (not shown) that processes instructions received from or generated by a software application, a program, a piece of code, a device, a computer, a computer system, or a combination thereof, which independently or collectively direct operations of the terminal  150 . The instructions may be embodied permanently or temporarily in any type of machine, component, equipment, storage medium, or propagated signal that is capable of being delivered to the terminal  150  or that may reside with the controller at the terminal  150 . The terminal  150  may include a general-purpose computer (e.g., a personal computer) capable of responding to and executing instructions in a defined manner, a workstation, a laptop, a PDA (“Personal Digital Assistant”), a wireless phone, a component, other equipment, or some combination of these items that is capable of responding to and executing instructions. 
     For instance, in one implementation, the terminal  150  includes one or more information retrieval software applications (e.g., a browser, a mail application, an instant messaging client, an Internet service provider client, or an AOL TV (“America Online Television”) or other integrated client) capable of receiving one or more data units. The information retrieval applications may run on a general-purpose operating system and a hardware platform that includes a general-purpose processor and specialized hardware for graphics, communications and/or other capabilities. In another implementation, terminal  150  may include a wireless telephone running a micro-browser application on a reduced operating system with general purpose and specialized hardware capable of operating in mobile environments. 
     In another implementation, the terminal  150  may include a simplified device capable of receiving a video signal not encapsulated in a traditional data unit. For example, the duplicating switch  130  may transmit a raw video feed formatted in accordance with ETSI, DVB, ATSC, or ECCA standards for transmission directly to a cable tuner or television. 
       FIG. 2  illustrates a duplicating switch  200  structured and arranged to receive a stream, store content from the stream, generate data units from the stream, and transmit the generated data units as a stream. The duplicating switch  200  generally corresponds to the duplicating switch  130  in  FIG. 1 . The duplicating switch  200  generally includes a storage system  210  for storing the stream of data units, a high speed interconnect  220  between the various subsystems in the duplicating switch  200 , a switching engine  230  for modifying and transmitting the stream of data units to two or more clients, a first communications interface  240  for receiving a stream of data units from a source system, and a second communications interface  250  for transmitting a stream of data units to two or more clients. 
     The storage system  210  enables the duplicating switch  200  to store at least the content portion of the data unit. The storage system  210  may be volatile or nonvolatile and may include memory (e.g., RAM) and/or storage (e.g., HDDS). Implementations of storage system  210  may include a hard disk drive or a more portable media, e.g., a compact disk, a tape drive, or an optical memory device. Implementations also may include combinations of memory and storage. 
     The high speed interconnect  220  generally refers to a device that connects a component of the duplicating switch  200  with other elements of the duplicating switch  200 . Examples of the high speed interconnect  220  may include, but are not limited to, SCSI (“Small Computer Serial Interface”), Fibre Channel, UTOPIA (“Universal Test and Operations PHY interface for ATM (“Asynchronous Transfer Mode”)), Infiniband, and other protocols and connection methods. The high speed interconnect may include physical, logical, timing and electrical connections and standards as well as protocols that enable these high speed interconnects to exchange data. 
     Generally, a switching engine  230  includes a device that performs network operations in hardware (e.g., a chip or part of chip). In some implementations, the switching engine  230  may include an ASIC (“Application Specific Integrated Circuit”) implementing network operations logic directly on a chip (e.g., logical gates fabricated on a silicon wafer then manufactured into a chip). For example, an ASIC chip may include a logical gate structure implemented in silicon and configured to receive a packet and filter based on examining an IP address. 
     Implementations of the switching engine  230  may include a FPGA (“Field Programmable Gate Array”). An FPGA generally is defined as a chip fabricated to allow third parties to implement a variety of logical designs (e.g., group of gates) on the chip. For example, one designer may load a design that replaces the IP address of received IP packets with a different IP address. Another example may include a design that performs segmentation and reassembly of IP packets as they are modified during transmission of the IP packet through different networks. 
     Implementations of the switching engine  230  also may include a network processor. A network processor generally is defined as a chip that, among other features, allows software to specify which network operations should be performed. One example of a network processor may include several interconnected RISC (“Reduced Instruction Set Computer”) processors fabricated in a network processor chip. The network processor chip may implement on some of the RISC processors software that changes an IP address of an IP packet. Other RISC processors in the network processor may implement software that controls which terminals receive an IP stream. 
     The switching engine  230  may include a precoder (not shown) that is structured and arranged to receive a data unit, extract a content piece from the payload portion of the data unit, determine where the content piece will be stored, and store the content piece in a structured manner so that retrieval (e.g., playback) involves retrieving neighboring content pieces, packaging data units around the content pieces, and transmitting the data units to one or more requestors. This process will be described further with respect to  FIG. 4 . 
     The first communications interface  240  generally is structured and arranged to receive a stream of data units from a device such as the source system  110 . Implementations of the communications interface may include a LAN or WAN interface with the ability to direct the data units to one or more locations in the duplicating switch  200 , using, for example, the high speed interconnect  220 . Implementations also may include other forms of transmitting a media signal, including transmission according to ETSI, DVB, ATSC, or ECCA standards. 
     The second communications interface  250  generally is structured and arranged to transmit a stream of data units from the memory system  210  to one or more devices that generally correspond with recipients, such as terminal  150  described with respect to  FIG. 1 . Implementations of the second communications interface  250  may include a LAN or WAN interface with the ability to direct the data units to one or more locations in the duplicating switch  200  using, for example, the high speed interconnect  220 . Implementations also may include other forms or transmitting a media signal other than by IP networking. In addition, the second communications interface  250  is not limited to the same type of format as the first communications interface  240 , though the interfaces may include the same format and even the same physical interface. For example, the first communications interface  240  may include a POS (“Packet-over-SONET”) interface while the second communications interface  250  may include some form of Ethernet (e.g., 100-Base-T or Gigabit Ethernet). 
       FIG. 3A  provides an exemplary block diagram of a duplicating switch (e.g., duplicating switch  130  in  FIG. 1 ) with a memory implementation. The duplicating switch  300 A includes a RAM array  320 A, a switching engine  330 A and a network interface  340 A. 
     The RAM array  320 A may include one or more RAM memory banks structured and arranged to store one or more pieces of content. The RAM array  320 A may store just a portion of the stream of data units. For example, a provider streaming out a movie may store one portion of the movie for several users to watch at one time. The RAM array  320 A may store a window (e.g., a ten-minute window) of the movie that a user may use to time-shift the movie (e.g., pause, stop playing, or rewind) while staying current with the movie being broadcast. 
     Within the RAM array  320 A, there may be location identifiers to monitor or indicate which content piece to package and/or transmit to a terminal. For example, an OSP (“Online Service Provider”) may schedule a stream of data units to be transmitted to terminals at a certain time. In one example, the duplicating switch loads a portion of the stream of data units indicated by the location identifier to the RAM array  320 A. In this example, the duplicating switch may use one or more pointers to indicate which data units (e.g., frames) should be transmitted to which user. In another example, an on-demand system may load a larger portion of the data units to memory and may use a first pointer to transmit one stream of data units and a second pointer to transmit a second stream of data units simultaneously or otherwise. 
     The switching engine  330 A is structured and arranged to manage the content being stored in and retrieved from the RAM array  320 A. Aspects of the switching engine  330 A generally correspond to aspects of the switching engine  230  in  FIG. 2 . The switching engine  330 A generally loads and retrieves content to/from the RAM array  320 A. Examples of content that may be loaded and retrieved by switching engine  330 A include content pieces without wrappers (e.g., OSI wrappers), such as datagrams having MPEG (“Motion Picture Experts Group”) I, P, and B frames removed, video frames and differential checksum values that describe frame-to-frame changes, and frames with one or more added wrappers (e.g., a layer 4 datagram). In one implementation, the switching engine  330 A may implement a system of pointers designed to monitor where in time or sequence number the terminals are with respect to the available stored content. The switching engine  330 A may include a device, a program, a software controller, or another system or device in combination with the above. In another implementation, the switching engine  330 A may manage overall system utilization and refuse subsequent requests for services or attempt to serve more than one terminal from one stream of data units. The network interface  340 A is designed to transmit and receive a stream of data units and generally corresponds to the first communications interface  240  and second communications interface  250  described in  FIG. 2 . 
       FIG. 3B  provides another exemplary block diagram of a duplicating switch  300 B with a storage implementation. The duplicating switch  300 B includes a stream platform  310 B, a switching engine  330 B, and a network interface  340 B. 
     The stream platform  310 B is structured and arranged to store content from within a stream of data units. The stream platform  310 B includes a hard disk drive  312 B (or a tape drive or other magnetic memory) and optical memory  316 B. Generally, the stream platform  310 B includes memory components with low bandwidth performance but high capacities. For example, storage may include solid-state-memory (not shown) that is slower than solid-state memory used in other applications. Typically, because of the greater storage available with less bandwidth, the stream platform  310 B will store a larger portion of a stream (e.g., a movie), but will limit access to fewer simultaneous streams absent RAM or other cache interfaces. 
     Implementations of the storage platform  310 B may include the disk storage  312 B with a RAM interface to the switching engine  330 B. For example, the duplicating switch may include a RAM bank and disk storage. Content pieces may be loaded to the disk storage such that the content pieces are retrieved in the order that they are transmitted. As the content pieces are being retrieved, they are loaded to the RAM bank. The higher throughput performance of the RAM banks may enable more terminals to access the same content piece. Terminals accessing the stream of data units may use a pointer to the content pieces in the RAM bank to monitor and load the data units they need in the stream of data units. 
     The switching engine  330 B is structured and arranged to manage the content being stored and retrieved in the stream platform  310 B. The switching engine  330 B generally corresponds to the switching engine  330 A described with respect to  FIG. 3A . The network interface  340 B is designed to transmit and receive a stream of data units and generally corresponds to the first communications interface  240  and second communications interface  250  described with respect to  FIG. 2 . 
     The RAM-based and storage-based systems described with respect to  FIGS. 3A and 3B  illustrate implementations that are designed to account for common limitations of existing memory and storage systems (e.g., solid-state RAM offers high throughput but less storage while hard drives and optical memory offer higher storage but less throughput). However, implementations are not limited to those shown, nor are memory or storage devices necessarily subject to these constraints. For example, a disk drive may be used to implement a system managing multiple pointers and may offer higher bandwidth, while solid-state memory may offer higher density storage than the disk drive storage. 
       FIG. 4  shows an example of a duplicating switch  400  with precoder functionality. The duplicating switch  400  generally corresponds to the duplicating switch  130  of  FIG. 1 . The duplicating switch  400  includes a data unit interface  410 , a content extraction system  420 , a content arrangement system  440 , and a content store  450 . 
     The data unit interface  410  generally is structured and arranged to interface with a network to transmit and receive a data unit from the content store  440 . Generally, the functionality of the data unit interface  410  corresponds to the functionality of the first communications interface  240  and the second communications interface  250  of  FIG. 2 . Data unit interface  410  also may be configured to segment and reassemble a data unit that has been separated during transmission, or to handle unconventional data units. For example, the data unit interface  410  may be configured to transmit/receive one or more media frames (e.g., frames formatted according to one of the ETSI, DVB, ATSC, or ECCA standards). In one instance, if the duplicating switch  400  receives an analog signal, the data unit interface  410  may convert the signal to a recognized format that the frame or content piece may store. 
     The content extraction system  420  is structured and arranged to remove a data unit wrapper that is added around content for transmission. For example, the content extraction system  420  may remove one or more bits associated with OSI (“Open Systems Interconnect”) information encapsulated along with the content for transmission. The content extraction system  420  also is capable of adding the wrapper when the data is retrieved from the content store  450  for subsequent transmission. For example, the content extraction system  420  may remove wrapper information when storing a stream of data units in the content store  450  and may add a different wrapper when transmitting the stream of data units from the content store  450 . 
     The content arranger  440  is structured and arranged to direct storage and retrieval of the content information such that the content information may be retrieved in a determinate manner. For example, the content may be arranged so that the addressing information may be updated in predictable increments. In another example, the content may be arranged such that the difference between frames of content may be calculated by analyzing an associated checksum that then may be stored. 
     Determining where a content piece may be stored and storing the content piece may include using hard disk drive constraints to store the content piece. For example, the content store  450  (e.g., hard drive) may store the content pieces such that the same “read” or data retrieval will retrieve related content pieces that are frequently transmitted in close proximity to one another (e.g., adjacent frames in a movie or adjacent I, P, and B MPEG frames). 
     Determining where a content piece may be stored and storing the content piece may include using solid-state storage (e.g., various forms of RAM) to store the content piece. For example, the solid-state storage may store all or a portion of the stream in an array of RAM memory. If a portion of the RAM memory is used to store the content piece, the RAM may load a certain window of content for transmission to one or more terminals. In some implementations, the duplicating switch may store more than one instance of the stream of data units in the array of RAM. 
     The content store  450  is structured and arranged to store content pieces or frames. As described above with respect to the content arranger  440 , the content is generally structured and arranged to be retrieved in a manner enabling transmission of related content pieces to one or more terminals. The content store  450  generally corresponds to the memory system  210  of  FIG. 2 , the RAM array  320 A of  FIG. 3A , and the storage platform  310 B of  FIG. 3B . 
       FIG. 5  illustrates a procedure  500  for storing and transmitting a data unit using a duplicating switch. In general, the procedure  500  may be performed using one of the duplicating switches described with respect to  FIGS. 1-4 . 
     Initially, the duplicating switch receives a data unit (step  505 ) and selects the content piece from the data unit (step  510 ). Typically, selecting the content piece of the data unit (step  510 ) involves identifying fields or portions of the data unit that correspond to the content, and removing some or all aspects not related to the content. For example, a duplicating switch may remove one or more layers of an OSI (“Open Systems Interconnection”) header and store the remainder of the data unit as the content piece. In another example, selecting the content may include creating or modifying location identifiers to identify which portion of the data unit should be stored when the data unit is loaded to memory. 
     Selecting the content (step  510 ) may include enabling one or more portions of other aspects of the data unit to be retained with the content. For example, one or more fields of the OSI header may be preserved and stored as content. 
     Implementations may include using a pro-coder to modify or adjust the content for storage. For example, the pre-coder may compress the content so that less bandwidth is consumed during transmission. In another example, the pre-coder may calculate a checksum or shortcut describing intra-content differences. This checksum or shortcut may be stored in place of storing some of the content pieces. 
     The duplicating switch determines the location in the memory system in which to store the content piece (step  520 ). Typically, the location for storage of the content piece is selected so that related content pieces may be retrieved in related operations. Examples of related content may include sequential frames in a video and/or content in a time slice. The duplicating switch then stores the content piece in the determined location (step  530 ). 
     At some later time, the duplicating switch receives a request for a content piece (step  540 ). Receiving a request for a content piece may include receiving a user (e.g., terminal  150  in  FIG. 1 ) request display of a video stream on the user&#39;s home computer. Implementations also may include having other devices request the content piece. For example, a cable modem acting as a set top box may request a content piece for display to a television. 
     Implementations also may include having a request originate from a source other than the intended destination. For example, a cable system administrator may generate a request for the content piece on behalf of one or more subscribers. 
     The duplicating switch  130  determines which content piece has been requested (step  550 ). The requestor may designate a content piece to send. For example, a terminal may keep track of which content has been received, and may generate a request for one or more pieces of content (e.g., frame number  100  is missing). Implementations also may include having the duplicating switch track which content piece is required. For example, a duplicating switch may attempt to transmit the same content piece to several users. 
     The duplicating switch  130  determines where the content piece is located (step  560 ). To do so, the duplicating switch may use the location identifiers described with respect to  FIGS. 2 and 3 . Other implementations may employ a file and/or an archiving system maintained to manage access to content pieces. 
     The duplicating switch  130  retrieves the content piece (step  570 ). The duplicating switch may do so by reading a memory location specified by a location identifier. Other implementations may include retrieving multiple pieces of content information (e.g., reading a sector on a disk). 
     The duplicating switch  130  packages the content piece in a data unit (step  580 ). For example, the duplicating switch may add one or more layers of OSI information (e.g., addressing information). Implementations where one or more aspects of the data unit other than content are stored with the content piece may include modifying one or more parameters in those fields. For example, if an Internet Protocol packet is stored, the destination address may be modified to the addresses of requesting users. 
     Finally, the duplicating switch transmits the data unit to one or more terminals (step  590 ). The data unit may be transmitted in formats other than IP addressing. For example, transmitting the data unit may include transmitting an on-demand channel over a network. 
     Referring to  FIG. 6 , the function of a communications system  600  will now be described. Communications system  600  generally includes a source system  602 , a manager  604 , a duplicating switch  606 , and terminals  608  and  610 . In general, the source system  602  corresponds to the source system  110  of  FIG. 1 , duplicating switch  606  corresponds to duplicating switch  130  in  FIG. 1 , and terminals  608  and  610  correspond to terminals  150  of  FIG. 1 . The manager  604  may include a cable system operator, an OSP, a content provider, or an entity capable of providing instructions or direction to the duplicating switch  606 . 
     As shown, the source system  602  generates a stream of data units (step  613 ). The source system  602  transmits the stream of data units to the duplicating switch  606  (step  616 ). 
     The duplicating switch  606  receives the stream of data units (step  625 ). The duplicating switch  606  then stores at least the content pieces from the stream of data units (step  627 ). 
     The stream may be transmitted in a variety of ways. In some implementations, the manager  604  waits for a condition to occur (step  618 ). For example, the manager may be a scheduler that is programmed to direct a duplicating switch “broadcast.” When the condition occurs (step  620 ), the manager  604  transmits a request to the duplicating switch  606  to transmit the stream of data units (step  623 ). 
     Alternatively, a terminal  608  may generate a request for a stream (step  633 ). For example, the terminal  608  may generate a request to view a particular video stream. The duplicating switch  606  receives the request (step  630 ). 
     In an implementation generally corresponding to the system described with respect to  FIG. 3B , the duplicating switch  606  may load one or more content pieces into fast memory (e.g., RAM) (step  631 ). For example, the duplicating switch  606  may determine that there is inadequate bandwidth to the existing storage of the content and may load frequently-accessed content pieces to the faster memory to increase capacity. 
     Regardless of the mechanism used to indicate when to transmit the stream of data units to a terminal, the duplicating switch  606  may transmit the stream of data units to two or more terminals  608 ,  610  (step  636 ). In some implementations, a terminal receives a stream that has been broadcast or otherwise automatically transmitted to the stream recipient without requesting the stream of data units. In either case, terminals  608  and  610  receive the stream of data units (step  640  and  640 A). Depending on the implementation, a different “stack” of content pieces may be loaded into memory to support terminal  610 . 
     In some implementations, the terminal  608  may generate and transmit a pause message (step  645 ). For example, a terminal may wish to “pause” a video on-demand stream and return to the stream at a later point. When the duplicating switch  606  receives the pause message (step  650 ), the duplicating switch  606  pauses transmitting to the terminal  608  (step  655 ). The duplicating switch  606  may still transmit a stream of data units to terminal  610  (not shown). The pause message may be implemented in a variety of ways. For example, terminal  608  may keep track of which data units have been received and resume where it left off by generating and transmitting a resume message (step  660 ). Another example may include having the terminal  608  transmit a stop message and the duplicating switch  606  keep track of where to resume when the transmit resume message is received (step  660 ). 
     If and when the duplicating switch  606  receives the resume message (step  665 ), the duplicating switch  606  transmits the stream of data units  670  to the terminal (step  670 ). The terminal  608  then receives the stream of data units (step  675 ). 
       FIG. 7A  depicts a duplicating switch  700 A structured and arranged to store multiple  30   o  instances of the stream of data units. The duplicating switch  700 A transmits two streams of data units, stream A and stream A 1 . Stream A occupies memory storage  710 A in the memory bank, while stream A 1  occupies memory storage  720 A in the memory bank. In one implementation, a first pointer  715 A to the memory storage  710 A indicates which content piece, relative to other content pieces, should be encapsulated as a data unit and transmitted to a terminal requesting Stream A. As mentioned previously, implementations may include storing a portion of the content pieces in the memory bank. For example, if problematic network conditions prevent a terminal from receiving some of the stream of data units, the terminal may not receive some of the content pieces and may experience gaps in receiving the stream of data units (e.g., missing time in a movie). 
     A second pointer  725 A to the memory storage  720 A indicates which portions of content pieces encapsulated in a stream of data units are being transmitted to several terminals. One or more terminals wishing to receive one or more data units in the stream of data units receive the content piece corresponding to the second pointer  725 A, which is continuously advanced to the next content piece. In some implementations, the second pointer  725 A may advance several content pieces and encapsulate more than one content piece in a data unit. 
       FIG. 7B  depicts a duplicating switch  700 B structured and arranged to store multiple location identifiers. In this example, duplicating switch  700 B includes five content pieces in stream A: A 1   710 , A 2   720 , A 3   730 , A 4   740 , and A 5   750 . Duplicating switch  700 B also includes an area of memory allocated for an expected content piece A 6   760 . 
     In one example, the duplicating switch  700 B enables each of terminals T, U and V to receive its own stream of data units. Each of the terminals manages a location identifier (e.g., pointer) to direct the duplicating switch to select the appropriate content piece to be transmitted. For example, terminals T, U, and V may begin by requesting content piece A 1   710  simultaneously. 
     After some content pieces have been transmitted, and as shown in  FIG. 7B , the location identifier  725  for terminal T may be referencing content piece A 2   720 , while the location identifier  742  and the location identifier  744  for terminals U and V are referencing content piece A 4   740  that corresponds to a different time-shift than content piece A 2 . This offset may have occurred because, for example, terminal T paused receipt of the stream of data units, and is now receiving content pieces that are delayed relative to those received by terminals U and V. 
     In another example, duplicating switch  700 B includes five content pieces in stream B: B 1   770 , B 2   771 , B 3   772 , B 4   773 , and B 5   780 . Duplicating switch  700 B also includes an area of memory allocated for an expected content piece B 6   790 . In one implementation, stream B may be part of the same stream of data units as stream A, but may correspond to a different portion of the stream of data units. For example, stream A may be a “video” stream 40 minutes into a video stream while stream B is five minutes into the same video stream. In another example, stream B may be identical to stream A but was added to implement better system performance. In yet another example, stream A and stream B may represent completely different video streams (e.g., two different television channels). 
       FIG. 8  illustrates a procedure  800  for implementing a “Pause” function on a duplicating switch, such as the duplicating switches described with respect to  FIGS. 1-7 . Initially, the duplicating switch receives a stream of data units (step  810 ) and stores content pieces from the stream of data units (step  820 ). With the content stored and ready for transmission, the duplicating switch waits to receive a request to play the stream of data units (step  830 ). Though the duplicating switch may wait for a request-to-play message, in some implementations, the duplicating switch may begin to transmit (e.g., play) upon receipt of the stream. In this configuration, the content might only be stored when a user requests pausing of the stream. 
     In an optional implementation, the duplicating switch may load the stream (content pieces) to fast memory (step  840 ). This generally corresponds to loading the stream to fast memory as described with respect to  FIG. 6 . 
     The duplicating switch transmits the stream of data units (step  850 ). While transmitting the stream, the duplicating switch  130  may receive a pause request (step  860 ). If the duplicating switch  130  receives a pause request, the duplicating switch stops transmitting the stream of data units to the terminal (step  865 ). With the stream of data units paused, the duplicating switch  130  may wait to receive a play request (step  870 ). 
     If the play request is received, the duplicating switch  130  continues to transmit the stream of data units where the terminal left off (step  880 ). If not, the duplicating switch  130  waits for the resume request. When the terminal resumes receiving the stream of data units, the duplicating switch checks for a new pause request (step  860 ). 
     If the duplicating switch  130  does not receive a pause request, the duplicating switch may receive a stop request or reach the end of the stream (step  885 ). If the stop request is received or the end of the stream of data units is reached, the duplicating switch ceases transmitting (step  890 ). If not, the duplicating switch  130  continues transmitting and returns to waiting for a pause request (step  860 ). 
     Referring to  FIG. 9 , a cable system  900  enables a media switch  930  to transmit content (e.g., video) to a terminal  950 . The media switch  930  is connected through a network  935  to cable headend gear  940 , which is connected through a network  945  to the terminal  950 . Aspects of cable system  900  generally relate to aspects of the communications systems described previously with respect to  FIGS. 1-8 . However,  FIG. 9  illustrates how aspects of the duplicating switch described previously may be used in a media switch in the context of a cable system. Specifically, cable system  900  may enable access to terminal-specific content through a cable system, for example, by mapping content onto frequency/process identification numbers used by the cable system and exchanging the access information with the terminal. 
     Generally, media switch  930  includes aspects of a duplicating switch, such as the switch  130  illustrated in various of  FIGS. 1-8 , which is configured to interface with the cable headend  940  and the terminal  950  to enable access to content. Typically, media switch  930  includes communications interfaces that may be used to send and receive content. For example, the media switch  930  may receive content from an upstream node (e.g., a source system  110 ). This received content may be transmitted to other devices (e.g., PCs (not shown in  FIG. 9 ), cable headends  940 , and terminals  950 ). The received content also may be stored to enable on-demand access to the content. 
     The media switch  930  is not limited to video content. For example, the media switch  930  may include audio content for cable-based radio stations, text and imaging content for displays and slide shows, and overlay content to be displayed with video content and/or as an alternative to the video programming. 
     The network  935  may include one or more communications paths between the media switch  930  and the cable headend  940 . Generally, aspects of the network  935  may relate to aspects of the networks  120  and  140  described previously. However, network  935  may be configured to address one or more issues arising in the context of distributing content to a cable headend  940 . For example, network  935  may use certain transmission parameters (e.g., to control jitter, quality of service, and/or comply with reception requirements of the cable headend  940 ). Other aspects relating to interfacing with a cable headend  940  may include channelization control and/or scheduling. For example, a piece of content may be configured as an IP stream so that minimal processing is required to map the  1 P stream into the feed transmitted over the cable system. 
     Cable headend  940  typically is structured and arranged to receive a stream of content from the media switch  930  and to transmit the content across the network  945  to the terminal  950 . This may involve mapping received streams of content to a system of channels used by a set top box. For example, in the case of QAM (Quadrature Amplitude Modulation), the content may be mapped to a frequency/PID (“Process Identification Number”) pair. A set-top box accessing the cable system may know that a particular pair (e.g., 1/112) corresponds to a particular channel (e.g., channel 2), while another pair (e.g., 3/115) corresponds to another channel (e.g., channel 45). In this manner, the appearance of “channels” may be maintained for users, independent of the underlying cable system. 
     Typically, network  945  includes part of a cable system from which the terminal  950  may access a cable signal. For example, the cable signal may distribute  100  channels for a consumer to access. The cable system may include one-way and two-way communications. To illustrate, a portion of the available bandwidth may be allocated for high-speed Internet access to enable a terminal to send and receive data. In another illustration, the channel may include a one-way video signal being distributed to set-top boxes. 
     Typically, the terminal  950  enables a consumer to access a cable system (e.g., via network  945 ) to receive content. Examples of the terminal  950  may include a set-top system, a tuner, a personal computer, and an Internet access device. The terminal  950  may include a proxy and one or more other access devices behind the proxy. For example, a consumer may have a tuner system that demultiplexes a signal and sends content signals to one or more home appliances (e.g., a television). 
     Generally, the terminal  950  is configured to select a channel of content within the overall group of channels. For example, a terminal  950  may select a particular frequency/PID pair (e.g., 1/112) to access a particular television channel (e.g., channel 2). The tuner  950  generally is able to exchange data with one or more other systems (e.g., media switch  930  or cable headend  940 ). 
     One example of the communications capability may include accessing the communications link  960 . The communications link  960  may use the same communications channel as the content being distributed (e.g., in-band communications), or it may include out-of-band communications. For example, an in-band communications link  960  may include having the terminal  950  use a cable channel dedicated to Internet access to transmit content requests to the media switch  930  and/or the cable headend  940 , for example, through networks  935  and  945 . An example of an out-of-band communications link may include a modem that accesses a phone line and/or a wireless modem designed to access a wireless network (e.g., a TDMA (“Time Division Multiple Access”) or 802.11 (b) network). 
     The communications link  960  may interface through one or more intermediate devices to access the other systems. For example, the cable headend  940  may act as a proxy for communications from the terminal  950  to the media switch  930 . The cable headend  940  may receive communications formatted in a first protocol and convert them to a second protocol for transmission on the network  935 . 
       FIG. 10  is a block diagram of media switch  930 . Media switch  930  includes a first communications interface  1010 , a broadcasting switch  1020 , an on-demand switch  1030 , a switch controller  1040 , and a second communications interface  1050 . In general, the media switch  930  is configured to access content from a content source and to enable one or more terminals to access the content in real-time and/or on-demand. 
     Generally, the first communications interface  1010  accesses one or more sources of content for the media switch  930 . In one example, the first communications interface  1010  is a software controller that pulls content from a source system. In another example, the first communications interface  1010  is configured to receive pushed content. 
     The first communications interface  1010  may include a data network interface (e.g., an Ethernet interface), or it may include media-oriented interfaces. For example, the interface may be configured to receive MPEG2 content from a satellite. 
     The broadcasting switch  1020  typically is configured to enable real-time or near real-time access to media content. For example, the broadcasting switch  1020  may receive a feed and may transmit the content to several devices. In general, the label “broadcast” refers to the real time nature of the content, rather than the ability of the content to be seen by more than one terminal (e.g., an IP multicast). However, depending on the configuration of the cable system, the broadcast content may be seen by more than one user. 
     The on-demand switch  1030  enables on-demand access to stored content. For example, premium content involving additional costs may be stored to a disk drive. Access to this content on the disk drive may be managed through a collection of location identifiers that each indicate the location at which one terminal receives the content. If a user wishes to pause a feed, the location identifier may be stopped at its present location so that the content may be subsequently accessed at the same point when the user wishes to resume. 
     Typically, the switch controller  1040  may be used to control the systems in the media switch  930 . For example, the switch controller  1040  may include a scheduling program to coordinate timely delivery of content to other devices, such as, for example, the cable headend  940 . This scheduling program may enable stored on-demand content to be sent out as “live content” by coordinating a nearly simultaneous delivery of stored content to the cable headend  940 . Thus, the stored content can be mapped into predefined channels so that a user can tune in to the advertised channel at the advertised time. Similar scheduling also may be performed using the broadcasting switch  1020 . 
     The switch controller  1040  also may interface with one or more off-device systems. For example, the switch controller  1040  may interface with a terminal  950  to receive content requests. In another example, the switch controller  1040  may interface with a cable headend  940  to control frequency/PID mappings. 
     Typically, the second communications interface  1050  exchanges data with a cable headend  940  and/or terminal  950 . For example, the media switch  930  may use the second communications interface  1050  to transmit content to cable headend  940  for distribution to a terminal  950 . In another example, the second communications interface  1050  may receive content requests from the terminal  950 . 
     Referring to  FIG. 11 , frequency spectrum diagram  1100  shows the frequency/bandwidth allocation structure that may be used in a cable system (e.g., network  945 ). A typical cable system may use multiple frequencies and PIDs within each frequency. However, for exemplary purposes, three frequency base bands are shown, Frequency Band (FB)  1110 , FB  1130 , and FB  1150 . Typically, each frequency band represents a base band around which multiple channels/PIDs within the frequency are used. For example, several frequencies may be modulated around a higher base band frequency. In another example, several channels may be time-division multiplexed around the base band frequency. In yet another example, each channel may be Quadrature Amplitude Multiplexed around a base band signal. Additionally, there is typically a guard band (not shown) that separates adjacent signals. 
     FB  1130  illustrates how 4 PIDs (e.g., channels) may be multiplexed into the one frequency band. FB  1130  includes PIDs  1131 ,  1132 ,  1133 , and  1134 . Each of these PIDs may be a channel accessible by several terminals or a personalized channel. The channels may be dynamically accessible and/or programmable. For example, implementing a personalized channel may involve allocating a frequency/PID pair for each terminal. The media switch  930  then coordinates content requests with the cable headend to ensure that the required content is transmitted to the cable headend for mapping onto the specified frequency/PID. In another example, a terminal  950  may receive a message indicating which frequency/PID pair will be used to transmit the requested content. These frequency/PID pairs may be reused and shared, depending on the state and configuration of the network  945 . 
     Referring to  FIG. 12 , a flow chart  1200  shows how a media switch  930  may interface with a terminal  950  to enable the terminal  950  to request content. Initially, the terminal  950  determines a content requirement (step  1210 ). Determining a content requirement may include perceiving a user selection of content, explicitly, implicitly, or intentionally. For instance, in a cable television environment, determining a content requirement may include having a consumer interface with an automated programming guide showing programming content and available times for the programming content. In another example, determining a content requirement may include selecting a piece of on-demand content from a list of on-demand offerings. In yet another example, determining a content requirement may include changing a channel to which the user is tuned. The appearance of changing channels may involve interfacing through an intermediary interface so that the user cycles through preferred channels in order of preference. The preferred channels list may be generated in a seamless manner without requiring user intervention. 
     With the content requirement, the terminal  950  transmits a content request (step  1220 ). Transmitting a content request may be performed through in-band or out-of-band communications. The media switch  930  receives the content request (step  1230 ). 
     The media switch  930  accesses content (step  1235 ). Accessing content may include requesting content from an on-demand device, a broadcasting switch, and/or an on-demand switch. Accessing content may include loading the content to the broadcasting switch and/or the on-demand-switch. If the first piece of content has been loaded to either of these switches, accessing content may include adding terminal address information to a list of addresses on the duplicating switch. For example, if the terminal requests live content being duplicated on a broadcasting switch, an IP address related to the terminal may be added to the list of devices to which the broadcasting switch is sending content. For example, the broadcasting switch may receive a virtual IP address for a cable headend interface that maps the streamed content to a personal channel over the cable system. 
     Accessing content also may include receiving content automatically (e.g., from a satellite or an analog feed), or in response to a scheduled pushing program designed to ensure timely delivery of the content. 
     The media switch  930  identifies a personal channel (step  1240 ). Identifying a personal channel generally includes identifying a resource (e.g., a modulated channel) within the cable system available to distribute the content to the terminal. The personal channel may be dedicated to a single terminal. For example, identifying the personal channel may include accessing a database of modulated channels (e.g., a frequency/PID pair) not being used and allocating one of the available channels for exclusive use by the requesting terminal. In another example, the personal channel may be identified in advance and identifying the personal channel may include determining that the personal channel exists and is being used by the requesting terminal. 
     Identifying a personal channel (step  1240 ) may include identifying access information that enables the terminal  950  to access the personal channel. The access information may include parameters describing the frequency and the process identification number within the frequency. In another example, the access information may include a label that serves as a proxy for this information. For example, the terminal  950  may include a mapping function that converts a label into the frequency and the process identification number. 
     In any event, the media switch  930  transmits the access information to the terminal  930  (step  1250 ), which receives the access information (step  1260 ). 
     The media switch  930  interfaces with a cable headend  940  (step  1270 ). Typically, interfacing a cable headend  940  includes enabling content sent by the media switch  930  to be distributed by the cable headend  940  on the personal channel. The cable headend  940  interfaces with the media switch  930  (step  1280 ). One example of interfacing may include determining a mapping of content into a personal channel as a frequency/PID pair. In another example, interfacing may include accessing a configuration database describing the frequency/content mapping. In yet another example, interfacing between the media switch  930  and the cable headend  940  may include managing reception of an IP stream or other transport stream with the requested content from the media switch  930  to the cable headend  940 . Although an exemplary IP stream has been described, the cable system is not limited to using IP to distribute requested content. 
     Interfacing with the cable headend  940  may be performed in conjunction with other operations that have been described. For example, the cable headend  940  may determine what frequency/PID pairs are available, map the requested content to a selected pair in the available pairs, and transmit those parameters to the media switch  930  for transmission to the terminal  950 . In another example, the media switch  930  also manages the frequency/PID mappings and directs the cable headend  940  to map the content to the designated frequency/PID. 
     In any event, the terminal receives the content by referencing the location indicated in the access information (step  1290 ). In the example where the personal channel is already created and being used, accessing content information may include receiving the newly requested content on the personal channel already being used. 
     Although the operations described are described in a sequential order, the operations described above may be performed in parallel and/or a different order. For example, the content may be accessed before the content request is received. Similarly, the media switch  930  may interface with the cable headend  940  before or in conjunction with accessing content. Other sequences and combinations may be used. 
       FIG. 13  is an exemplary flow chart  1300  showing a terminal accessing personalized content through a media switch. Generally, the systems shown in  FIG. 13  relate to the systems described previously. For example, the media switch  930 , the cable headend  940  and the terminal  950  may relate to the media switch  930 , the cable headend  940 , and the terminal  950  described with respect to  FIGS. 9-12 . However, flow chart  1300  illustrates how a terminal accesses a particular television episode. 
     Initially, the terminal  950  determines episode A of television show B should be accessed (step  1310 ). For example, the user may have missed the scheduled transmission of episode A and elect to watch the missed episode. Alternatively, the user may enjoy the particular series, or be participating in a distance-learning course. 
     The terminal  950  transmits a request for episode A to the media switch  930  (step  1320 ). The media switch  930  receives the request, either through the cable system (e.g., cable headend  940 ), or through alternate channels (not shown) (step  1330 ). The media switch accesses episode A (step  1335 ). In one instance, accessing episode A involves accessing a data store local to the media switch  930  that is used to store recently broadcast content. Alternatively, the user associated with terminal  950  may be allocated a personal data store on the media switch  930 . The user may actively manage this personalized data store on the media switch  930 , or the media switch administrator may proactively manage content on the user&#39;s behalf. For example, the media switch may determine that the user routinely requests television show B and ensure that several episodes from television show B are stored and available for the user to access. 
     The media switch  930  identifies a personal channel so that the terminal  950  may access episode A (step  1340 ). For example, the media switch determines that frequency X and PID Y may be used to transmit episode A. Identifying the personal channel may include scheduling the transmission so that the transmission does not conflict with other scheduled transmissions. For example, if the media switch  930  determines that, due to terminal  950  “pausing” the stream, episode A would overlap a subsequent transmission on frequency X and PID Y, the overlapping conflict may be resolved. In one case, the time-shifting ability of the current transmission may be limited. For example, the user may be precluded from pausing episode A. The media switch  930  also may reschedule the subsequent transmission to a different frequency and channel. Other options may include, but are not limited to, canceling either the present or the subsequent transmission. 
     The media switch  930  instructs the terminal to access frequency X and PID Y to access the personal channel (step  1350 ). The terminal  950  receives the access information (step  1360 ). The media switch  930  interfaces with the media switch  930  to transmit episode A on frequency X and PID Y (step  1370 ). The cable headend then may transmit episode A on frequency X and PID Y (step  1380 ), the terminal  950  then receiving episode A by accessing frequency X and PID Y (step  1390 ). 
     Although flow chart  1300  is shown as a sequence of events, one or more of the operations may be performed concurrently or in an alternate order. For example, the terminal  950  may access frequency X and PID Y (step  1390 ) before or concurrent with the media switch  930  interfacing with the cable headend  940  (steps  1370  and  1380 ). 
     Although the media switch  930  and the cable headend  940  are described in the context of network operations, the media switch  930 , the cable headend  940 , and/or the terminal  950  may use one or more proxy signals or messages instead of network packets to negotiate the transmission of the personal channel. For example, the cable headend  940  may act as a bridge between IP commands and cable system commands used to communicate with the terminal  950 . 
     Other implementations are within the scope of the following claims. For example, the media switch  930  may relate the content request to available resources. Typically, relating the content request to available resources includes determining whether the piece of content requested is already being hosted on existing resources. For example, a user may request the same movie that another user has requested. The transmission of the movie may be coordinated so that the users may share the same resource (e.g., frequency/PID pair). In support of this, a longer series of trailers may be transmitted so that multiple users may access the same resource without missing the featured content. 
     Another example of relating the content to available resources may include determining the state of demand for resources so that allocation of the frequency/PID pairs accommodates the largest number of users and/or the priorities of the cable provider. For example, a cable provider may determine that utilization is approaching the system capacity. As a result, some resources, such as Internet access channels, may be reallocated to accommodate premium access channels. 
     The media switch  930  may determine if the existing resources (e.g., existing content being transmitted) may be used to enable access to the content requested. If so, the media switch  930  transmits access information for the existing resource to the terminal (e.g., frequency/PID pair already providing the content). If not, the media switch  930  transmits the content to the cable headend  940 . The cable headend  950  receives the content and maps the content into the prescribed access information. 
     The media switch  930  may include a controller structured and arranged to accommodate changing cable system architectures. For example, the media switch  930  may include a broadcasting switch and a scheduling controller, while other on-demand servers provide on-demand content. The scheduling controller may interface with these on-demand servers to direct content to the cable headend  940 . In one instance, the scheduling controller may interface with off-device on-demand content to map it to the access information. 
     Although operations have been described in the context of a pause fimnction, similar functionality such as fast forward, rewind, and stop operations may be implemented. Other operations may include, but are not limited to, track selection so that a particular program may be advanced program-by-program by selecting an icon or figure to advance to the next piece of content, e.g., the next show on television. Although it has been described in the context of a cable system, implementations of a cable system may include fiber (optical), and/or wireless links. For example, a wireless local loop may be used to distribute video content to one or more users. Alternatively, fiber may be distributed to a user&#39;s home for distribution. 
     Although the media switch and the headend have been described in the context of different systems, the media switch and the headend may be combined in one or more systems. This system may include broadcast and on-demand functionality. Indeed, depending on the timing constraints in the system configuration, the broadcast switch and the on-demand switch may be the same system. For example, a broadcast switch may include a switch with a very short buffer designed to keep content that is being transmitted within a narrow window of time. In contrast, an on-demand switch may be configured to store content configured to correspond to a large period of time.