Patent Publication Number: US-7725569-B2

Title: Method and system for configuration and download in a restricted architecture network

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This patent application is a continuation of copending U.S. patent application Ser. No. 10/136,237, filed May 1, 2002, allowed, herein incorporated by reference in its entirety. 

   FIELD OF THE INVENTION 
   The invention generally relates to computer networks and more particularly relates to a method and system of maintaining uniform software configurations of multiple computers in a restricted architecture network, such as in a system for providing passenger entertainment, communication or other services in the cabin of an airplane or other vehicle. 
   BACKGROUND OF THE INVENTION 
   A restricted architecture network is used, for example, to provide entertainment or other services to passengers on board an aircraft, commonly referred to as an in-flight entertainment system (IFES). In an IFES, a plurality of computers are connected to provide various functions. These computers include, for example, audio/video headend equipment, area distribution boxes, passenger service systems (PSS), and seat electronic boxes. In the modular environment of a restricted architecture network, each of these computers is referred to as a line replaceable unit (“LRU”). At least some of the LRUs act as client devices serving passenger seats individually or by seat groups to display video entertainment or instructional presentations, to receive input for selection of audio/video or PSS choices, to provide telephony or communication capabilities, to play interactive games, or to provide other similar kinds of services. 
   When a plurality of computers are run within a restricted architecture network, such as within an IFES, it is absolutely necessary for the software configurations on each of the respective computers to be maintained according to exact specifications. The software configuration, including an exact number of identifiable software components, must be maintained: all of the software components specified as part of the software configuration must be present; no software components not specified must be present. Proper IFES maintenance requires the checking of the software configurations of the various LRUs within the restricted architecture network and the subsequent downloading of software to the LRUs to update available selections and services or to diagnose and fix any problems. 
   Restricted architecture networks, thus, have serious constraints on their structure and function. Such a network usually has a limited amount of physical space available for the hardware and connections between discrete hardware components. The amount of power or bandwidth for connections available may be limited. The origin of these constraints, as well as the need for absolute consistency in software configuration within the restricted architecture network may arise from the requirements placed on such systems by external agencies, such as the Federal Aviation Administration (FAA). The FAA requires, for example, that only thoroughly tested software configurations be allowed to run within a restricted architecture network. The risk that an LRU with a slightly different software configuration might disable the function of the entire network, or of flight computers on the aircraft, is too great to allow a single discrepancy. Thus, a method for configuring LRUs within a restricted architecture network must be perfectly consistent and reproducible; but maintaining near perfect consistency often requires an expensive, labor intensive method. 
   The time availability for conducting IFES hardware and software maintenance is also limited to the short maintenance window between flights as a plane sits at a gate for unloading and loading. The software configuration of each of the computers within the IFES system must be setup and tested during this limited maintenance time window. In practice, if the IFES configuration and download method exceeds the otherwise scheduled maintenance period, operators will avoid initiating or abort the IFES maintenance. As a result, it is desirable to optimize the speed and efficiency of the method of configuring and downloading software to computers in an IFES. In conventional systems, during hardware installation, e.g., during the removal or addition of a seat electronics box, software cannot be updated or configured—the entire hardware configuration must be in place before software configuration can be begin. Accordingly, the required service time has been the time for hardware configuration plus software configuration. The time window of opportunity to perform such a service task while a plane is on the ground is very limited. 
   Maintenance personnel are expensive overhead for an airline. In order to minimize the number of required IFES maintenance personnel, and to minimize the required training and skill level for conducting basic IFES maintenance tasks, it is desirable to provide an IFES configuration and download method which is reproducable and reliable. 
   Conventional methods and systems for maintaining the software configuration on the plurality of computers within an IFES are not usually implemented in a network, and are based on the use of a “master” computer, hard-wired to other computers within the system, which polls each “slave” computer for its current configuration, tabulates a list of the software configuration on each computer, and downloads to or deletes from a particular computer the necessary software components. 
   The downloading, deleting or overwriting of software components has been conventionally performed in a sequential manner, software component by software component. Each computer must wait for each of a series of missing software components to be downloaded, one at a time. The conventional configuration method is initiated, for example, when an operator selects a particular software component to be downloaded to the plurality of computers within the system. Conventionally, the master computer downloads the selected software component in a sequential manner to a first slave computer, then to a second slave computer, then to a third slave computer, and so on. Furthermore, the IFES configuration and download method conventionally operates in a completely serial manner among the IFES computers, i.e., the master computer connects only to one slave computer at a time, and downloads only one software component to that slave computer at a time. 
   The conventional serial and sequential downloading techniques have impaired the development of IFES systems, as each additional computer or configurable software component increases the required maintenance time and method complexity, thereby increasing the possibility of system error and failure. At present, an IFES might consist of close to one thousand separate, configurable computers, each with a software configuration that must be perfectly maintained. The exceptional difficulty of accomplishing this task as the number of LRUs within a restricted architecture network multiplies makes it desirable to provide a configuration checking and software downloading method that operates in a parallel manner. More particularly, it is desirable to provide a system and method wherein a master computer connects to more than one slave computer at a time or downloads more than one software component to a slave computer at a time. 
   A conventional IFES has operated on custom, proprietary software and hardware, including proprietary protocols for signal transmission within the IFES network. Due to a complex and unique nature of such proprietary systems, problems in the IFES have been difficult to diagnose and fix. 
   As a result, a need exists for an improved method and system for configuring the software of a multi-computer system within a restricted architecture network. 
   SUMMARY OF THE INVENTION 
   The foregoing complications and difficulties attending the configuration and download of software within a restricted architecture network are overcome by the method and system for configuring and downloading software that is substantially described herein. 
   According to an embodiment of the present invention, software configuring and downloading is performed with the parallel, multi-access abilities of established Internet transfer protocols, such as Transmission Control Protocol/Internet Protocol (TCP/IP) and File Transfer Protocol (FTP). In an embodiment, an LRU within the system is selected to act as a configuration server, and an LRU within the system is selected to act as a download server. The LRU selected to act as the configuration server may act also as the download server, or the LRUs selected to act as servers may be two different LRUs. The system and method of the present invention provide for flexibility and modularity within the system by allowing for any of a plurality of LRUs within the system to act as either the configuration server, the download server, or both. In another embodiment of the present invention, more than one configuration or download server might be implemented, allowing for redundancy within the system, and for incremental increases in the capacity of the system. As is known to those of ordinary skill in the art, it is not necessary to the present invention that one particular LRU within the restricted architecture network be selected to act as either the configuration or the download server. 
   The configuration server is provided to check the configuration of multiple LRUs within the system. The download server is provided to allow for the download of software to multiple LRUs within the system. Configuration and download activities are thus limited only by the number of simultaneous FTP sessions that the configuration and download servers can handle. Hence, the time required for a complete configuration of the system is limited primarily by the network bandwidth and the performance of the configuration and download servers. 
   The steps provided herein for configuring and downloading are useful as a method for diagnosing and repairing problems in an IFES having a plurality of configurable LRUs. The steps are also useful for performing routine updating of an IFES to maintain a desired uniform configuration among at least a group of the LRUs or to provide new features and amenities. 
   In an embodiment, a method is provided for checking the configuration of a plurality of configurable LRUs in an IFES aboard an aircraft. The IFES includes at least one configuration server in communication over a network with the LRUs. The method for checking the configuration includes the following steps: (a) generating an LRU configuration file at the LRU, the LRU configuration file containing a list that identifies software components currently residing on the LRU; (b) sending the configuration file from the LRU to the configuration server, the configuration server holding the LRU configuration file in a working directory; (c) detecting the arrival of a configuration files in the working directory; (d) updating a system configuration data file (SCDF) that contains data representing current and previous LRU configurations by setting the current SCDF data to reflect the LRU configuration file generated by the generating step and by setting the previous SCDF data to reflect an LRU configuration file generated by the LRU during a previous running of the configuration checking method; and (e) deleting the LRU configuration file from the working directory. The foregoing steps are executable in parallel and independently for each respective LRU to be checked. Additionally, in an embodiment, at least part of the SCDF is stored, in a database on the configuration server, or on any of the LRUs within the system. Preferably, the step of sending the configuration file is performed under a standard network protocol, such as FTP. 
   In an embodiment, the step of generating the LRU configuration file is automatically performed upon startup of the respective LRU. Alternatively, the step of generating the LRU configuration file can be manually initiated, wherein the method further includes sending an initiation request from the configuration server to the LRU. 
   In some applications, it is desirable to maintain an event log containing a history of configuration changes. Therefore, in an embodiment, the method further includes comparing the LRU current configuration file to a previous configuration file from the LRU, determining inconsistencies therebetween, and writing the inconsistencies to an event log. 
   In the event that an LRU is slow to respond, it is desirable that the system does not passively wait an indefinite period for the LRU to report. Active polling steps are optionally provided to avoid problematic delays. More particularly, in an embodiment, the method further provides sending an initial instruction from the configuration server to the LRU to perform the generating step, waiting a first predetermined period, then checking the working directory after the first predetermined period to determine whether the LRU configuration file has been received by the configuration server. Furthermore, if the LRU configuration file has not been received, the method further actuates the sending of a second instruction from the configuration file to the LRU to perform the generating step, waiting a second predetermined period and then again checking the working directory to determine whether the LRU configuration file has been received. If the LRU configuration file has not been received after the second predetermined period, the configuration server indicates that the LRU has failed to report. 
   Preferably, the checking method includes the step of storing the configuration file at the associated LRU after the step of generating the configuration file. This is useful to expedite additional steps provided for downloading needed software components to the target LRUs. 
   In an embodiment, a method is further provided for downloading software from a download server to one or more configurable LRU computers in an IFES aboard an aircraft, the downloading method including: selecting a list of desired software components representing software desired to be loaded onto one or more target LRUs; sending the list of desired software components from the download server to each of the target LRUs; comparing the list of desired software components at each LRU against a respective list of current software components at each of the LRUs; determining needed software components from inconsistencies between the list of desired software components and the list of current software components; sending an instruction from each of the LRUs to the download server to download the needed software components to the respective LRU; downloading the needed files to the LRU; and deleting unnecessary software components from the LRU. The downloading method preferably implements a standard protocol such as FTP for file transferring steps, including the step of sending the list of desired software components from the download server to each of the LRUs. More particularly, the step of sending an instruction from each of the LRUs to download needed software components includes executing an FTP “get” command identifying the needed components. 
   Although the method for configuration and the method for download are independent in the system of the present invention, there are two places in which they overlap. In the first place, during the method of download, the LRUs receive the desired list of software components from the download server. The desired list of software components is compared with the current list of software components, which is generated with the configuration file during in a step of the method for configuring the LRUs. In the second place, during the method for download, the download server may present a list of the names or number of the LRUs that have reported their configuration. This number is provided in the present embodiment of the invention by the active polling steps in the configuration method. 
   The independence of the configuration server and the download server is an advantage to the present invention. In an embodiment, several of the LRUs may act as a configuration server, a download server, or both. The use of more than one configuration server or download server allows for network traffic to be dispersed more evenly, alleviating bandwidth related slowing of the method for configuring or the method for downloading software components. 
   Another aspect of the invention is that it provides a configurable system for use in a restricted architecture network. The system includes at least one server having a memory that maintains a working directory, a storage device that maintains a database, a data parser, and a network communication device. Additionally, the system includes a plurality of configurable LRUs, each of the LRUs including a configuration file generator operable to generate a configuration file representing current software components at the respective LRU; and a network communication device operable to send the configuration file to the server. The system further includes a network backbone for handling parallel communications between the LRUs and the server. For example, the network backbone can be an Ethernet network. The server receives the configuration files from the respective LRUs in the working directory, wherein the data parser is operable to update an SCDF stored in the database by writing the configuration files to a field of the system configuration data file that represents a current configuration, moving data from previously stored in the current field to a field representing the previous configuration. The LRUs preferably send the configuration data files to the server via FTP. 
   The system is equipped, in an embodiment, to update the LRU software components by downloading desired software over the network. Accordingly, each of the LRUs further includes a comparator to compare the configuration file to a list of desired components received from the configuration server to determine needed components, and wherein the network communication device of the LRU is further operable to send the configuration file to the request a download of the needed components from the server. 
   To facilitate a manual initiation of the system, in an embodiment, the system includes a management terminal operable to send an initiation request to cause the LRUs to generate the configuration files. Alternatively, the LRUs are operable to initiate themselves. More particularly, the configuration file generator at the LRU is operable to automatically generate the configuration file upon startup of the LRU. 
   A particular advantage of the present invention is that the sending of files is performed with a standard protocol, such as FTP, that has been established and tested outside restricted architecture networks. The use of standard protocols avoids complications and difficulties inherent in the use of a proprietary protocols within such environments. Standard protocol software, such as FTP client and FTP server software, are commonly provided with commercially available operating system software, and are otherwise simple to write and compile for platforms typically used in a restricted architecture network. Advantageously, the system and method of the invention avoid a need to create or use proprietary software protocols for use in maintaining a software configuration. In addition, the present invention avoids a need to combine individual software components to configure all of the computers. 
   A significant advantage of the present invention is that the software configuration of the computers within a restricted architecture network can be updated even when the hardware configuration is not complete. In a system including a plurality of line replaceable units (LRUs), a configuration checking method or downloading method can be performed on one or more selected LRUs or on all LRUs. Additionally, in an embodiment, the downloading of software is individualized to provide only software components needed by the respective LRU. As a result, there is no need for the entire system to be operational in order for one LRU to complete its software configuration. This results in restricted maintenance times and high operational efficiency. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, advantages, and features of the present invention will be apparent from the following detailed description and the accompanying drawings, in which: 
       FIG. 1  is a block diagram of a multi-computer system for checking the configuration of, and downloading software to, computers within a restricted architecture network according to an embodiment of the present invention; 
       FIG. 2   a  is a schematic diagram of a first portion of a restricted architecture network including headend components of an in-flight entertainment system having features according to teachings of the invention; 
       FIG. 2   b  is a schematic diagram of a second portion of the restricted architecture network including seat-level components; 
       FIG. 2   c  is a block diagram of a hardware layout for the digital server unit in accordance with an embodiment of the present invention; 
       FIG. 3   a  is a first portion of a flow chart of a method for checking the configuration of computers within a restricted architecture network according to teachings of the present invention; 
       FIG. 3   b  is a second portion of a flow chart of the method for checking the configuration of computers within a restricted architecture network according to teachings of the present invention; 
       FIG. 3   c  is a third portion of a flow chart of the method for checking the configuration of computers within a restricted architecture network according to teachings of the present invention; 
       FIG. 3   d  is a fourth portion of a flow chart of the method for checking the configuration of computers within a restricted architecture network, showing the active polling steps of the method according to teachings of the present invention; 
       FIG. 4   a  is a schematic diagram of a target LRUs sending configuration files to the configuration server; 
       FIG. 4   b  is a schematic diagram of the configuration server storing configuration files to the SCDF in a configuration database; 
       FIG. 5  is a flow chart a method for downloading software to target LRUs according to teachings of the invention; 
       FIG. 6   a  is a schematic diagram of the download server sending lists of desired software components to the target LRUs; 
       FIG. 6   b  is a schematic diagram of a configuration file data stack compared to a desired software list; 
       FIG. 6   c  is a schematic diagram of LRUs obtaining needed software components from the download server using an FTP “get” command; 
       FIG. 7  is a diagram of an exemplary system configuration GUI which can be used in accordance with a method of the invention; 
       FIG. 8  is a diagram of an exemplary media selection GUI which can be used in accordance with a method of the present invention; and 
       FIG. 9  is a diagram of an exemplary LRU selection GUI which can be used in accordance with a method of the present invention. 
   

   DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
   While the present invention is susceptible to various modifications and alternative forms, certain preferred embodiments are shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the description is not intended to limit the invention to the particular forms described; to the contrary, the description is intended to cover all modifications, alternatives, and equivalents falling within the spirit and scope of the invention defined by the appended claims. 
     FIG. 1  illustrates an exemplary network or system  1000  suitable for a restricted architecture network, such as an IFES. The block diagram of  FIG. 1  provides a general hardware layout of computers capable of executing electronic instructions and for running or storing software and data. According to an embodiment of the present invention, the system  1000  generally includes a management terminal  1100 , at least one server  1200 , and a plurality of configurable computers or LRUs (e.g., LRUs  1300 - 1 ,  1300 - 2  . . .  1300 - n ) which can be referred to generically herein as an “LRU  1300 ” or “LRUs  1300 ”), including a particular LRU  1300 - n  (labeled “LRUn”), which will be used for descriptive purposes as representative of any of the LRUs  1300  within the system  1000 . As indicated, the LRUs  1300 - 1 ,  1300 - 2  . . .  1300 - n  can be part of an LRU Group  1400 . The management terminal  1100  is operable to receive input data from, and to provide output data to, a user. For example, the management terminal  1100  preferably has a display on which a graphical user interface (GUI) can be provided. The management terminal  1100  can be an application specific device or a PC such as a laptop computer. Moreover, the management terminal  1100  can be constructed as either a permanently installed fixture or as a portable device installed as needed for development, management or troubleshooting of the system  1000 . In a connected state, the management terminal  1100  is in communication with each of the configuration servers  1200 . 
     FIG. 1  also includes the plurality of LRUs  1300 . The configurable LRUs  1300  represent the computer components or devices whose software configuration can be reliably and reproducibly controlled. In a restricted architecture network generally, the configurable LRUs  1300  are components that must be diagnosable and repairable in the field when software problems occur. In an aircraft, train, bus, or boat, the configurable LRU  1300  can be, for example, a passenger service or entertainment device integrated with a passenger seat environment. In other environments, the configurable LRU  1300  can be a device to measure and record data. Generally, the system and method of the invention are useful for a system  1000  in which a plurality LRUs  1300 . There may be more than a thousand LRUs  1300  within a system, although only three are labeled in  FIG. 1 . 
   The system  1000  is generally a LAN that operates according to suitable network standard, such as Ethernet, including 10 Base T, 100 Base T, or Gigabit Ethernet, or a standard other than Ethernet, such as a Token ring standard or a wireless standard. The use of such standards is generally known to those of skill in the art. 
     FIGS. 2   a - 2   c  illustrate in greater detail exemplary hardware comprising the system  1000  ( FIGS. 2   a - 2   b ) and an example of a digital server unit, which might be used as either the configuration server  1200 - 1  (see, e.g.,  FIGS. 4   a  and  4   b ), the download server  1200 - 2  (see, e.g.,  FIGS. 6   a  and  6   c ), or both ( FIG. 2   c ). 
   The system  1000  is generally a local area network (LAN) comprising a plurality of computer components that communicate over a network data backbone  1500  and an entertainment broadcast or RF backbone  1600 . The network data backbone  1500  preferably uses 100 base T Ethernet, and the broadcast RF backbone  1600  is preferably capable of carrying high-bandwidth RF transmissions containing video and audio signals. 
   Generally, the LRUs  1300  within the system  1000  include cabin management terminal  1100 , an audio/video controller  2120 , a digital server unit  2500 , one or more area distribution boxes  2150  and a plurality of tapping units  2130  in communication over the data backbone  1500 . The audio/video controller  2120 , digital server unit  2500 , and other auxiliary devices can provide audio and video signals over the RF broadcast backbone  1600  to the area distribution boxes  2150  or tapping units  2130 . The area distribution box  2150  passes the signal to one or more seat electronics boxes ( 2160  in  FIG. 2   b ) within its associated area. Alternatively, the tapping unit  2130  receives the entertainment signal from the broadcast backbone  1600  and sends the signal to one or more associated overhead display units  2140 . 
   Cabin Management Terminal 
   In  FIG. 2   a , the cabin management terminal  1100  is, in an embodiment, a central user interface to the IFE system for flight crewmembers. Through the cabin management terminal  1100 , a user can specify the software configurations of other hardware components within the IFE system  1000 . The cabin management terminal  1100  also allows a user to enable or disable the availability of audio/video content or the Internet to passengers on the plane. The cabin management terminal  1100  is connected, in an embodiment, to a 100 Base T Ethernet data network (heretofore “Ethernet”)  1500 . The local area network (LAN) switch  200  allows for each LRU node connected to the Ethernet network to be treated as a single segment, allowing for faster data transfer through the Ethernet network. Multiple LAN switches  200  could be used in another embodiment. The present invention could operate according to any appropriate networking communication standard, such as Ethernet 100 Base T, 10 Base 2, 10 Base 5, 1000 Base T, 1000 Base X, or Gigabit network. In yet another embodiment, the network could instead be an Asynchronous Transfer Mode (ATM), Token Ring, or other form of network. 
   In accordance with an aspect of the invention, the cabin management terminal  1100  can be used in the configuration checking method as described in connection with  FIGS. 1 and 3  and the downloading method described in connection with  FIGS. 5-9 . 
   Area Distribution Box 
   Turning to  FIG. 2   a , the area distribution box  2150  is generally a local seat-level routing device. The area distribution box  2150  controls the distribution of signals on the network data backbone  1500  and the RF backbone  1600  to a group of the seat electronics boxes  2160  ( FIG. 2   b ). The area distribution box  2150  maintains assigned network addresses of seat electronics boxes  2160  and, optionally, tapping units  2130 . The area distribution box  2150  preferably also includes built-in test equipment (BITE) capabilities. Additionally, the area distribution box  2150  controls and communicates with a corresponding zone passenger service system  2155  that includes, for example, overhead reading lights and attendant call indicators. 
   Optionally, the area distribution box  2150  further operates to control the tapping unit  2130  in a similar way to that described below in connection with the for the audio/video controller  2120 . 
   In an embodiment, the area distribution box  2150  may operate as either the configuration server, the download server, or both. Hence, the area distribution box  2150  may be a server  1200  as shown in  FIG. 1 , handling either the configuration checking or software downloading functions as will be described in greater detail in connection with  FIGS. 3 and 5 . It should be recognized, however, that in accordance with another aspect of operation of the invention, the area distribution box  2150  is capable of responding to a configuration check when prompted request from another device. In such an embodiment, the area distribution box acts as a configurable target LRU  1300  as described below in connection with the configuration checking method of  FIG. 3  or in connection with the downloading method  5000  of  FIG. 5 . 
   The area distribution box  2150  hardware includes one or more microprocessors with a memory, such as a flash memory, a network interface card, an RS485 interface, and radio frequency amplifiers. Additionally, in an embodiment, the area distribution box  2150  contains appropriate gain control circuitry for gain control of the RF distribution. In an embodiment, the software running or stored on the area distribution box  2150  might include multiple software components, such as an operating system (e.g., Linux), a web server (e.g., Apache), TCP/IP, FTP client, FTP server, and ports or connectors for interfacing with the tapping unit(s) and CSS. An appropriate interface includes a serial port, such as RS 485 interface, or a USB. 
   Audio Video Controller 
   The audio/video controller  2120  generally operates as an entertainment headend controller and can perform a variety of functions within the IFE system. The audio/video controller  2120  communicates with a plurality of input devices, such as cameras, video players, audio players, etc. The audio/video controller  2120  is in communication with both the data backbone  1500  and the broadcast backbone  1600 . The functions of the audio/video controller  2120  include, for example, distributing audio and video content, controlling the tapping units  2130  and overhead display units  2140 , and frequency modulation for various inputs such as video tape reproducer  2080  and audio reproducer unit  2090 . 
   Additionally, in an embodiment, the audio/video controller  2120  also operates as a headend controller of the passenger service system  2060  (PSS), which includes, for example, the public address system and warning indicators instructing passengers to fasten seat belts or not to smoke. Accordingly, the audio/video controller  2120  is connected to PSS related inputs such as the cockpit area microphone  2070 , which can interrupt other signals over the RF backbone  1600  for crew announcements. By incorporating PSS control functions into the audio/video controller  2120 , the need for a separate LRU  1300  for controlling those PSS functions is eliminated. 
   Furthermore, the audio/video controller  2120  operates the passenger flight information system (PFIS)  2100  as a point of access for system data, including data obtained from non-IFE system equipment, such as aircraft identification, current time, flight mode, flight number, latitude, longitude, and airspeed. To facilitate external communications, according to an embodiment, the audio/video controller  2120  is further in communication with a cabin telecom unit  2050  that can communicate with earth or satellite based communication stations through one or more satellite links  2020 . 
   In accordance with an aspect of the invention, the audio/video controller  2120  can operate as the configurable LRU  1300  described in connection with  FIG. 1  and  FIG. 3  below. The audio/video controller  2120  can respond to configuration request by generating a configuration file, transmitting the configuration file via FTP, and receiving a download of updated software components. In another embodiment, the audio/video controller  2120  may act as the configuration server, the download server, or both. 
   The audio/video controller  2120  hardware includes a microprocessor, an Ethernet switch, telephony interface components, an Aeronautical Radio, Inc. (ARINC) interface, an RS485 interface, and audio modulators for the public address and audio/video content distribution. The audio/video controller  2120  contains various software components including, for example, an operating system such as Linux, a web server such as Apache, TCP/IP, FTP client, FTP server, RS485 interfaces to the tapping units and CSS, and LAPD communications. 
   Digital Server Unit 
   The digital server unit  2500  provides analog and video outputs derived from digital content stored, for example, a hard disk drive, and is constructed modularly with a well-defined external interface. A rack mount is provided with electrical and physical interfaces as specified in ARINC 600. The digital server unit  2500  obtains power, connects to external control interfaces, provides 6 base-band video outputs with 2 stereo audio outputs associated with each video output and 12 stereo outputs and 1 RF output that combines 3 RF inputs with 6 modulated video signals (including 12 stereo video-audio) and 12 stereo modulated audio outputs at this connector. Auxiliary front mounted connectors are also provided for diagnostic access and expansion of the storage sub-system via a SCSI II interface.  FIG. 2   c  is a block diagram of an embodiment of the digital server unit  2500 . 
   The digital server unit  2500  is modular in construction, comprising a power supply  2530 , a connector  2540  (e.g., an ARINC 600 connector), an RF combiner  2590 , a BITE component  2610 , a connector  2620 , a TERM component  2630 , LEDs  2640 , a serial console  2650 , an E-net component  2655 , an SCSI component  2670 , and an I/O assembly  2605  with the ARINC connector and a back-plane that interfaces to modular circuit cards, as understood by one skilled in the art. These circuit cards provide control and interface functions, audio or video decoding, analog buffering, RF modulation, and multiplexing of the audio or video signals into a combined signal. The chassis provides mounting and cooling provisions for the modular circuit cards as well as mounting means for the disk drive  2520 . The mounting means for the disk drive  2520  is designed to extend the physical operating parameters, for example, the shock and vibration parameters of the disk drive  2520  for use in an aircraft. 
   The controller  2510  shown in  FIG. 2   c  includes a central processing unit (CPU), which in the presently preferred embodiment is an 8260 Power PC. The CPU accesses digital content stored in the disk drive  2520  and streams the content via 100 Base T Ethernet interfaces to video or audio clients where the digital data is decoded and converted to analog audio and/or video signals, which are then buffered and made available as differential base-band video and audio output at the ARINC connector for other LRUs  1300  within the network  1000 . The signals are also modulated into RF signals and combined with 3 RF input signals for distribution via the broadcast RF audio/video backbone  1500 . 
   The I/O assembly shown in  FIG. 2   c  includes: a primary domain full duplex 100 Base T Ethernet port; four secondary domain full duplex 100 Base T Ethernet ports; 2 RS-232 communication ports; 2 master or slave capable ARINC 485 communication ports; 12 master capable ARINC 485 communication ports; one CEPT E-1 digital telephone trunk-line; one four-wire modem with a differential 20 ohm, 0 dBM audio output and a 600 ohm, 0 dBM audio input; 17 ARINC 720 compliant keyline inputs; 11 ARINC 720 compliant keyline outputs; one standby input keyline; one 20 ohm, 0 dBM auxiliary audio output; one 20 ohm, 0 dBM PRAM audio output; one 20 ohm, 0 dBM BGM audio output; 9 discrete inputs to identify unit address and RF frequency blocks; six differential 100 ohm, 1 Vpp video outputs; 12 differential 20 ohm, 0 dBM stereo audio/video outputs; 12 differential 20 ohm, 0 dBM stereo audio outputs; one passively coupled combined RF input; two actively amplified and combine RF inputs; one RF output combining the three RF inputs with all internally RF modulated audio/video signals; and single phase, 115 VAC, 400 Hz power input. 
   The front panel of the digital server unit  2500  further includes one secondary domain full duplex 100 Base T Ethernet port; one RS-232 communication port; DC power supply voltages; one supervisory processor reset; one supervisory processor attention input; LED status indicators for AC OK, DC OK, BITE OK, SCSI activity; one SCSI expansion port; one Ethernet switch status interface; and one test mode keyline input. The connection of the digital server unit  2500  within the network  1000  may vary considerably. An embodiment is shown in  FIGS. 2   a  and  2   b.    
   The digital server unit  2500  provides video entertainment in a way similar to a videotape reproducer  2080  or audio tape reproducer  2090 . Instead of videotape, video content is stored in compressed format, compliant with the Motion Picture Expert Group (MPEG) format (MPEG-1 or MPEG-2). The video data is stored in multiplexed format including video and between one and sixteen audio tracks in the MPEG-2 transport stream format. The audio content is stored, instead of with audio tape, on a hard disk  2520  in compressed format, compliant with the MPEG-3 (MP3) format. The high performance disk drive  2520  is accessed via a wide and fast SCSI interface by the CPU on the controller  2510 . The digital content is then streamed via TCP/IP to client platforms  2550 ,  2560 ,  2570 , and  2580  on circuit cards within the digital server unit  2500 . 
   Two types of clients are implemented: video clients (two per circuit card), and audio clients (four per card). Each video client can generate one video output with two associated simultaneous stereo language tracks selected from up to sixteen language tracks multiplexed with the video. Each audio client can generate 3 or 4 audio outputs. The digital server unit  2500  contains three video client cards for a total of six video clients and six associated dual stereo video and audio/video outputs. Twelve of the audio outputs are general purpose in nature, while the 13th and 14th outputs are used to implement PRAM and BGM functions. As these two aircraft interfaces are generally monaural, MP3 programming for the 13th and 14th audio outputs is encoded and stored as monaural MP3, and only the left channel of the stereo decoder is connected to the appropriate aircraft public address system input. 
   The video clients are not only digital MPEG audio/video decoders, but are also general purpose PC compatible platforms, and may implement customized functions that are displayed as broadcast video channels through the broadcast backbone  1600 . A typical example of this use of a video client is the implementation of a Passenger Flight Information System (PFIS)  2100 . 
   The controller  2510  includes, according to an embodiment of the present invention, a Power PC processor running at 166 MHz; 4 megabytes (MB) of boot Flash ROM memory; 64 MB of application Flash ROM memory; 64 MB of disk on chip Flash ROM memory; 256 MB of RAM memory; 2 kB of non-volatile static RAM; a clock calendar powered by a super capacitor; a high performance SCSI controller; two 9-port 100 Base T Ethernet switches; a digital signal processor (DSP) sub-system operating at 320 MIPS with 320 kB of internal memory and 1 MB each of external Flash and RAM memory, used to provide voice over IP, echo cancellation, DTMF tone generation and decoding, and legacy modem support; and one temperature monitor positioned at the upper wedge-lock, with two additional sense points at the lower wedge-lock and the CPU. 
   In a preferred embodiment of the present invention, the digital server unit  2500  may act as the configuration server, the download server, or both. The digital server unit  2500 , as described in the foregoing, has the computing resources necessary to carry out both the configuration method and the download method of the present invention. In an embodiment of the present invention, there may be more than one digital server unit  2500  installed within the network  1000 , allowing for a higher volume of data to be communicated to other LRUs  1300  within the network  1000 . 
   In accordance with an aspect of the invention, the digital server unit  2500  is capable of responding to a configuration check request and to receive a software download in connection with the method described below in connection with  FIGS. 3 and 5 . In such an embodiment, the digital server unit  2500  is the target LRU  1300  in the configuration checking method  3000  described below in connection with  FIG. 3  and the downloading method described below in connection with  FIG. 5 . 
   Satellite Link 
   To communicate outside of the aircraft, the IFE system  1000  includes an optional satellite link  2020  in  FIG. 2   a , which provides additional sources of audio, video, voice, and data content to the IFE system. In connection with a multi-channel receiver module  2030 , it provides a plurality of video channels to the IFE system. In an embodiment, the multi-channel receiver module  2030  is connected to the RF backbone  1600  that connects to other LRUs  1300  within the IFE system. The satellite link  2020  may also provide Internet access in combination with a network storage unit  2040 , wherein a plurality of popular web pages are downloaded to the network storage unit  2040  while the aircraft is on the ground, when the satellite link bandwidth is not consumed with bandwidth intensive graphics or movies. In cooperation with the cabin telecommunications unit  2050 , the satellite link  2020  may also provide access to ground based telephone networks, such as the North American Telephone System (NATS). 
   Tapping Unit 
   Generally, the tapping unit  2130  is an addressable device for tapping the broadcast signal and distributing selectable or predetermined portions of the signal to one or more display units. Accordingly, the tapping unit  2130  is connected directly to one or more overhead display units  2140  mounted for viewing by a single passenger or by a group of passengers. The overhead display unit  2140  may be mounted, for example, to a bulkhead or ceiling in an overhead position, in the back of a seat in front of a viewer, an adjustable mounting structure, or in any appropriate location. In an embodiment, the IFE system  1000  includes multiple tapping units  2130 . The tapping unit functions to turn the display unit on or off, and to tune the tuner for audio or video channel selection. In an embodiment, the tapping unit  2130  is also used to report the status of the radio RF signal on the audio/video RF backbone  1600 . 
   In accordance with an aspect of the invention, the tapping unit  2130  is capable of responding to a configuration check request and to receive a software download in connection with the method described below in connection with  FIGS. 3 and 5 . The LRUs  1300  of  FIG. 1  may be the tapping unit  2130 . 
   Seat Electronics Box 
     FIG. 2   b  is a continuation of the block diagram of  FIG. 2   a , a plurality of seat electronics boxes  2160  are connected to the area distribution box  2150  through the network data backbone  1500 . Each of the seat electronics boxes  2160  provides an interface with individual passenger control units  2220 , personal digital gateways  2230 , video display units  2170 , or smart video display units  2175  available to the respective passengers on the aircraft. In another embodiment (not shown in  FIG. 2   b ), more than one video display unit  2170  or passenger control unit  2220  are connected to each seat electronics box  2160 . The seat electronics boxes  2160  also control the power to video display units  2170 , the audio and video channel selection, and volume. One or more universal serial buses  2180  or audio jacks  2200  are also connected to the seat electronics boxes  2160 , allowing a passenger to connect a laptop computer  2190  or headphones  2210  into the network  1000 . In an embodiment, hardware on a seat electronics box  2160  includes a microprocessor, RF tap, RF amplifier, RF level detection, RF gain control, and RF splitter, an FM tuner, and a digital signal processor (DSP) for handling voice over IP. 
   In view of the foregoing description of the hardware architecture of the network  1000 , described now will be steps of how the system  1000  is capable of performing a configuration checking method and downloading method by which LRU configurations can be checked, maintained, and repaired or updated. 
   Configuration Checking Method 
   Steps of a configuration checking method  3000  according to an embodiment of the present invention are illustrated in  FIGS. 3   a - d . Generally, the configuration checking method  3000  is performed by the system  1000  of  FIG. 2   a - c  to determine the software configuration or hardware configuration of each of the LRUs  1300 . It should be understood that “LRUn” as referred to herein could be any one of the target LRU computers  1300 , such as the audio/video controller  2120 , area distribution box  2150 , seat electronics box  2160 , etc. or any of the components described herein as being a configurable LRU  1300 . Although the configuration checking method  3000  can be performed to produce various results as needed for a particular application, the configuration checking method  3000  produces a system configuration data file (SCDF), as will be described in greater detail below, shows the configuration of each checked LRU  1300  and optionally an event log which shows inconsistencies or changes in the configuration of each LRU  1300  relative to previous or desired configurations. 
   The method  3000  can be started either manually or automatically. For example, at step  3010 , the method  3000  is manually initiated when a user enters an initiation command from the management terminal  1100  ( FIGS. 1 ,  2   a ) or alternatively from another device, such as a laptop  2190 , within in the system  1000 . The method  3000  may also be initiated automatically, as indicated at step  3040 , upon startup of the LRUn  1300 , for example, upon actuation by a switch on the LRUn, upon connection of the LRUn to a power supply, upon connection of the LRUn to a network, or upon rebooting of the LRUn or another component of the system  1000 . In either case, the configuration server hosts a URL which initiates the configuration check. With reference to  FIG. 2   a , the configuration server can be any component that is equipped with appropriate software and which is in communication with the data backbone  1500 . Preferably, the configuration server is the digital server unit  2500  or the area distribution box  2150 . 
   Furthermore, the server  1200  shown in  FIG. 1  might be either the configuration server or the download server. The layout of the system, as shown in  FIG. 1 , applies to both the method for configuring and the method for downloading software components on the LRUs  1300  within the system  1000 . The server  1200 , therefore, should be understood to represent either the configuration server or the download server; the server  1200  is capable of carrying out both functions either sequentially or in parallel, as described herein in relation to the methods of configuration and download. In another embodiment of the present invention (not shown in  FIG. 1 ), there may be more than one server  1200 . In such an embodiment, the LRUs  1300  within the system would be able to communicate through the network  1500  with more than one server  1200 . 
   In some cases when a user manually initiates the method  3000 , the user may want to review results from a previous configuration check, and accordingly, step  3015  provides an opportunity for choosing to review a previous configuration condition. If the previous results are to be viewed, step  3020  obtains a SCDF that was the result of a previous configuration check, and the results are displayed in step  3025 . An appropriate error message might be displayed in step  3025  if no previous results are available to the configuration server in step  3020 . 
   In the step  3020  of obtaining the SCDF for viewing in an embodiment wherein the SCDF is stored at the configuration server, the management terminal  1100  opens an FTP session with the configuration server and executes an FTP “get” command. In response, the SCDF is read from storage at the configuration server and transmitted back to the management terminal  1100  for displaying through a monitor or printing at step  3025  through a peripheral device, such as a printer. In an embodiment wherein the SCDF is stored at the management terminal, the SCDF could be read from the storage device at the management terminal. 
   Steps  3020  and  3025  are useful to access past configuration information in an expeditious manner. Past configuration information could be useful in a system wherein the LRU  1300  configurations do not often change. Time is saved by permitting a user to refer to older configuration data prior to, or instead of, performing a checking method that would likely return redundant information. 
   Where a user has initiated the checking method  3000  in real time at step  3010 , certain troubleshooting or updating applications may present a situation in which it is desirable to check the current configurations of some of the LRUs  1300 , but not all. Therefore, step  3030  provides an opportunity for user selection of one or more LRUs  1300  to be checked. According to an embodiment of the present invention the management terminal displays a menu of various LRU selections including, for example, individual units, groups of units, or all of the configurable units within the system. The configuration server then sends a configuration request to each selected LRU  1300  at step  3035 . For descriptive purposes, we will assume that a user of the system  1000  has selected only LRUn  1300  in step  3030 . 
   According to an embodiment of the present invention, the configuration requests sent to the selected LRUs at step  3035  are preferably in the form of an Ethernet broadcast (e.g., in the case of a single target LRU) or multicast (e.g., in the case of multiple target LRUs) using a standard protocol such as TCP or UDP appropriately addressed to each of the selected LRU  1300  destinations. In the presently preferred embodiment of the invention, UDP is used since the messages sent within the system  1000  are short, and may be resent if an error is detected. The error correction available for use with TCP is not needed for this reason. The configuration server maintains a configuration map that identifies the LRUs  1300  present, the corresponding IP addresses and the assigned seat numbers. Each of the configuration requests is generally an instruction for the LRUn  1300  to generate a configuration file CFn, which will be described in greater detail below in connection with Table 1. 
   The computer executable code operable to perform steps  3010 - 3035  is run at the management terminal  1100 , in an embodiment. The software necessary for performing the functions associated with steps  3010 - 3035  may be stored at the management terminal as well. Alternatively, the steps  3010 - 3035  can be performed at the configuration server  1200 . In an embodiment, the set of steps  3045 - 3052  are performed by software loaded on the LRUn  1300 , as shown in  FIG. 3   a.    
   After sending a request for a configuration file to the selected LRUs  1300 , there is an optional set of steps for active polling of the LRUs  1300 . The active polling steps are shown in  FIG. 3   d ; the steps of active polling begin after step  3035  in  FIG. 3   a , and continue with step  3045  in  FIG. 3   a  after control is returned in step  3230  of  FIG. 3   d.    
   In an embodiment, the active polling method of  FIG. 3   d  is carried out by an Java Applet running inside a Web page on the LRUn  1300  (or on any of the LRUs  1300 ). With the Applet running on the LRUn, the configuration server is capable of executing instructions in order to carry out the method shown in  FIG. 3   d . The configuration server listens on a particular socket, and increments for every new configuration file received. A progress bar indicates how many of the LRUs  1300  have reported. According to an embodiment of the present invention, the entire method of  FIGS. 3   a - d  might take less than a few minutes—much faster than any previously known method for configuring software within a restricted architecture network. 
   In the first step of active polling, step  3210 , the configuration server sends an initial instruction to the LRUs  1300  selected in step  3030 , such as LRUn, to perform the generating step. The configuration server then waits a first predetermined period, indicated by the arrow  3215  in  FIG. 3   d . A check is made, in step  3220 , of whether the configuration file (CFn) for LRUn has been received by the configuration server during the first predetermined period of time. If so, then the configuration method returns in step  3230  to the next set of steps shown in  FIG. 3   a , beginning with step  3045 . If not, then a second instruction is sent in step  3240  from the configuration server to the LRUn to perform the generating step. Step  3240  is performed by sending the request directly from the configuration server to the particular LRUn that has not reported before step  3220  (rather than a broadcast to all the LRUs  1300  selected in step  3030 ). After waiting a second predetermined period, which is indicated by the arrow labeled  3245  in  FIG. 3   d , the active polling method continues by again checking in step  3250  whether the LRU configuration file has been received. If the selected LRU has still not reported after step  3250 , then a “No Response” report is generated in step  3260 , and the method returns in step  3230  to the next set of steps shown in  FIG. 3   a , beginning with step  3045 . The steps  3200 - 3260  together comprise the method for active polling that is carried out as part of the method for configuring LRUs (e.g., designated here as  1300 - n ) within the system  1000  of the present invention. 
   Turning back to  FIG. 3   a , it is clear from the flow chart that whether the method  3000  has been initiated manually (steps  3010 - 3035 ) or automatically (step  3040 ), each selected or predetermined LRU  1300  respectively generates an associated current configuration file CFn at step  3045 . The configuration file CFn includes current software or hardware configuration information about the particular LRUn, e.g., unit identification, hardware parts numbers, serial numbers, Media Access Control (MAC) addresses, IP addresses, and software component parts numbers, or any other information concerning LRUn that is desirably tracked. When the configuration file CFn for the LRUn is generated, it is optionally stored on a storage device at the LRUn as indicated by step  3050  in  FIG. 2 . An exemplary configuration file CFn of LRUn is shown below in Table 1. 
   
     
       
         
             
           
             
               TABLE 1 
             
             
                 
             
             
               Configuration File (CFn) of LRUn 
             
             
                 
             
           
          
             
                 
             
          
         
         
             
             
             
          
             
                 
               65938 
               Computer Part Number 
             
             
                 
               51759 
               Serial Number 
             
             
                 
               12345 
               Software Component 1 
             
             
                 
               23456 
               Software Component 2 
             
             
                 
               34567 
               Software Component 3 
             
             
                 
                 
             
          
         
       
     
   
   When the configuration checking method  3000  has been started automatically at step  3040 , the LRUn automatically generates the configuration file CFn. As will be apparent to those of skill in the art, this can be accomplished in various ways, such as with appropriate instructions programmed into startup operations of an operating system at the LRU  1300 . 
   Each LRU then sends its configuration file to the configuration server at step  3050 . Preferably, the configuration checking method  3000  uses a standard protocol such as FTP for sending files over the restricted architecture network. FTP is a commonly known application that is commonly bundled with TCP/IP (also called the Internet Protocol Suite). Accordingly, to send the configuration file, LRUn opens an FTP session with the configuration server and executes an FTP “put” command to transmit the configuration file CFn from LRUn to the configuration server, as indicated by step  3052 . 
   The LRU operations of respectively generating associated configuration files CFn (step  3045 ) and sending the files to the configuration server (step  3050 ) can be executed in parallel among the plurality of LRUs  1300  within the system  1000 . This parallel configuration checking method is advantageous for its efficiency.  FIG. 3   a  is connected to  FIG. 3   b  with the circle labeled “A”  3054 , which is shown in both figures. When the configuration server has received the configuration file CFn at step  3055 , the configuration server may hold the configuration file CFn in a working directory in step  3058 . As is known to those of skill in the art, it is not necessary for the configuration file to be held in a working directory, and the configuration method could be carried out on the fly without storing the information kept in the configuration file, but it is advantageous in that the information may be reused if it is kept in a working directory in step  3058 . 
     FIG. 4   a  schematically illustrates the sending of configuration files from LRUs which serve seats  23  AB and C, seats  17  HJ and K and seats  7  A and C, respectively, and are thus designated as LRUs  1300 - 23 ,  1300 - 17  and  1300 - 7 , respectively in this figure as well as in  FIGS. 4   b ,  6   a  and  6   c  (only LRUs  1300 - 23  and  1300 - 17  are shown in  FIG. 6   c ). The LRUs independently generate and execute an FTP “put” to send their corresponding configuration files CF23ABC, CF17HJK and CF7AC to the configuration server, where the configuration files are placed in the working directory. 
   The configuration server continuously or periodically checks the working directory for a new configuration file. Referring back to the method  3000  as illustrated in  FIG. 3   a , when the configuration server detects the arrival of a new configuration file CFn in step  3059 , the configuration server then updates in step  3060  a portion of the SCDF with the data of the configuration file CFn. Step  3060  generally comprises a parsing operation, which allows a portion of CFn to be extracted and supplied to the SCDF in steps  3065  and  3070 . More specifically, configuration file CFn associated a particular LRUn is then generated (step  3065 ) into a portion of the SCDF referred to herein as a “record” indicated as element SCDFn. If a record SCDFn already exists, then the record is updated with the information parsed from the CFn in step  3070 . 
   Each of the individual records SCDFn comprises a comparison table that contains, for example, “CURRENT,” “PREVIOUS” and “DESIRED” sets of data. For a given record SCDFn, each of the “CURRENT,” “PREVIOUS” and “DESIRED” sets contains data representing the categories contained in a configuration file for LRUn, as described above. An exemplary SCDFn record is shown in Table 2 as follows: 
   
     
       
         
             
             
             
           
             
               TABLE 2 
             
             
                 
             
             
               CURRENT 
               PREVIOUS 
               DESIRED 
             
             
                 
             
           
          
             
                 
             
          
         
         
             
             
             
             
             
             
          
             
               65938 
               Computer Part Number 
               94740 
               Computer Part Number 
               65938 
               Computer Part Number 
             
             
               51759 
               Serial Number 
               59811 
               Serial Number 
               51759 
               Serial Number 
             
             
               12345 
               Software Component 1 
               12345 
               Software Component 1 
               12345 
               Software Component 1 
             
             
               23456 
               Software Component 2 
               34567 
               Software Component 3 
               23456 
               Software Component 2 
             
             
               34567 
               Software Component 3 
               — 
               — 
               34567 
               Software Component 3 
             
             
                 
             
          
         
       
     
   
   In the exemplary SCDFn of Table 2, the CURRENT configuration reveals, for example, a new computer that has part number, serial number, and software component numbers matching the DESIRED configuration. The column labeled “DESIRED” reflects a configuration which, in an embodiment, a user has designated as the desired configuration for a particular LRUn. The data in the DESIRED column is updated upon the selection by a user of desired software components from a software inventory in connection with a downloading method as will be described in greater detail below in connection with  FIG. 5 . The column labeled “DESIRED” can contain all, some or none of the configuration information that appears in the columns labeled “CURRENT” or “PREVIOUS”, depending upon what hardware or software a user of the system desires to keep uniform throughout the system. During the configuration checking method  3000 , the PREVIOUS data is replaced with the old CURRENT data, and the CURRENT column of the SCDFn record (Table 2) is updated by overwriting the CURRENT data with parsed CFn data (Table 1). 
   Each of the records SCDFn is a portion of an SCDF which contains records for all of the LRUs  1300 . The SCDF preferably contains a complete representation of the desired software or hardware configuration information of the system  1000 , and accordingly, the SCDF includes a plurality of records SCDFn respectively corresponding to the plurality of configurable LRUn  1300  of the system  1000 . The SCDF is updated with the new record SCDFn, and the updated SCDF is written to a storage device (e.g., a disc drive, an NVRAM, etc) at the configuration server. The SCDF is preferably restored to RAM of the configuration server upon startup. In an embodiment, all or part of the SCDF may be stored on any of the LRUs  1300  within the system. As is known to those of skill in the art, all that is required for the SCDF to be stored on a particular LRU  1300  is an available memory. The added data integrity provided by the redundancy of this embodiment is advantageous. Optionally, the CFn may be deleted from the working directory on the configuration server in step  3075  after the SCDF has been updated. After LRUn has reported, and SCDFn has been updated within the SCDF, the configuration server sends a message to the management terminal  1100  in step  3080 , confirming that LRUn has reported its configuration. 
   As illustrated schematically in  FIG. 4   b , the exemplary configuration files CF23ABC, CF17HJK and CF7AC are generated into corresponding records SCDF23ABC, SCDF17HJK and SCDF7AC, which are stored to thereby update the SCDF in the configuration database. 
   The circle labeled “B”  3100  connects the sequence of steps shown in  FIG. 3   b  to the next set of steps in  FIG. 3   c . Referring to  FIG. 3   b , the comparing step  3085  is performed to determine changes that have occurred in the respective configurations of the LRUs. In particular, the comparing step compares the CURRENT and PREVIOUS components to determine which of these do not match. Differences between the CURRENT and PREVIOUS configurations are optionally written in step  3090  to an event log that contains a history of changes to the configuration of software or hardware within the system  1000 . The event log is stored at a storage device at the configuration server or on another computer within the system, such as a management terminal  1100 . That is, as indicated in step  3095 , the SCDF is sent to the management terminal, and an event log is sent to the management terminal in step  3105 . The process then ends at step  3120 . 
   According to an aspect of the invention, the configuration information relating to the various LRUs  1300  is centrally shared and accessible, as compared to some conventional systems in which the configuration data of multiple LRU units was available by laborious testing of each slave computer. 
   After the parsing step  3060  is complete and the SCDF has been updated with each of the records SCDFn (e.g., Table 2) in steps  3065  and  3070 , the configuration file can be deleted from the working directory at the configuration server in step  3075 , as schematically illustrated in  FIG. 4   b . Additionally, the configuration server then notifies in step the management terminal  1100  that the configuration check has been completed for the particular LRUn. In an embodiment, the management terminal  1100  waits until all DESIRED LRUs  1300  have been checked before the management terminal displays the new configuration information. 
   Advantageously, efficiency and stability of the system  1000  is promoted by facilitating the checking of LRU  1300  configurations per individual LRU unit or by LRU groups. In troubleshooting a problem in the system  1000 , maintenance personnel can “zero in” on the problem, for example, by: (a) checking the configurations of all LRUs in the system; and (b) if problems become apparent, then checking LRU configurations individually or by group. LRU groups in which the LRUs  1300  all have the DESIRED configuration may be checked quickly. LRU groups that show differences can then be analyzed one unit at a time. By facilitating this approach to troubleshooting, system maintenance can be performed in a logical, systematic manner that is time efficient. The method  3000  advantageously avoids a need to serially check the entire system one LRU  1300  at a time, thereby avoiding errors and repetitive procedures that have plagued conventional systems. 
   Method for Downloading 
   After the configuration checking method has been performed to identify outdated, problematic or otherwise undesired software components, it is desirable to be able to update the LRU  1300  configurations by downloading software components or settings to LRU  1300  units in a pinpoint, as-needed manner. Therefore, according to another aspect of the invention, a downloading method is provided to update respective software components or settings of the LRUs  1300 . An exemplary downloading method  5000  is illustrated in  FIG. 5 . The downloading method is typically used in conjunction with the configuration checking method in order to configure LRUs  1300  with updated software in an efficient manner. 
   The downloading method is effective to modify LRU  1300  software components so that each LRU has a CURRENT configuration file that matches the DESIRED configuration specified in the SCDFn. The downloading method can be used for updating software components of each LRUn after the configuration checking method  3000  to eliminate discrepancies between the respective CURRENT and DESIRED sets of configuration data for each of the LRUn units. When the configuration checking method  3000  is repeated immediately after the downloading method, the respective CURRENT and DESIRED sets of configuration information will match for each individual LRU, absent some intervening event that has caused an LRU configuration to change. 
   With reference to  FIG. 1 , the downloading method generally operates to transmit software components from a software component inventory at the management terminal  1100  or from the server  1200  (which for the downloading method is a download server) to one, some or all LRUs  1300 , such as LRUn. Preferably, the downloading is targeted to specific LRU addresses via FTP in order to avoid needless consumption of network resources. 
   More particularly, turning back to  FIG. 5 , the software downloading method  5000  begins at an initiating step  5005  when a user, such as IFES maintenance personnel, inputs an instruction to begin the downloading method. In an embodiment, the initiating step  5005  is performed from management terminal  1100  or from an auxiliary maintenance computer, such as a laptop  2190 , adapted to interface with Ethernet data backbone  1500  ( FIG. 2   a ) of the system  1000 . 
   In order for the download server to be able to distribute software components needed by the LRUs  1300 , those software components must first be placed in a software inventory that resides in a storage device accessible by the download server. In the case of the example herein, the inventory contains the DESIRED software components that need to be stored at the LRUs, as discussed above in connection with Table 2. Accordingly, as illustrated in  FIG. 5 , the user is prompted at step  5010  to update the configuration server inventory. If so selected, the list of DESIRED software components (that constitute a software “inventory”) may be specified in step  5020 . Optionally, if the most recent SCDF is available, it may be displayed in step  5015  preceding step  5020 . According to an embodiment of the present invention, the menu may be an HTML page displayed on an HTML browser running on the management terminal  1100  or on the auxiliary maintenance laptop. The HTML might even be displayed on one of the passenger control units  2220  or personal digital gateways  2230  connected to the system  1000  (shown in  FIG. 2   b ). 
   In step  5020 , the user can select new software to become part of the DESIRED inventory. The new software components are available by loading in step  5025  from a storage medium readable by at least one component of the system  1000  ( FIGS. 1 and 2 ). For example, the available new software components may be initially provided on a CD-ROM, DVD, or a recordable medium such as a diskette or hard drive that can be read from the management terminal  1100 , from the download server, or from any device on the data backbone  1500 , as illustrated in  FIG. 2   a . The new software components can include, for example, entertainment files such as digitally stored movies, music, or system operational files, such as program objects, or graphics. Referring to the method  5000  of  FIG. 5 , at step  5025 , the selected new components are read from the storage device. An FTP “put” command is preferably used to transmit the selected components from the initial storage location to the download server. Alternatively, the selected components remain available for reading from a drive accessible from the download server. 
   The download server may optionally store locally the new software components in an inventory of DESIRED components in step  5030 . This step allows for more flexible distribution of the software components in the second set of steps ( 5055 - 5085 ) in the method for download. In the final step of the first set of steps, the display is refreshed in step  5040  to reflect the inventory as updated to contain the new DESIRED components. 
   In the second set of steps in the downloading method  5000  of  FIG. 5 , after the inventory has been updated at steps  5015 - 40 , step  5050  presents an opportunity to update target LRUs with software components from the inventory loaded into the system  1000  in the first set of steps  5015 - 5040 . If no updating is to occur, the processing proceeds from step  5050  to end at step  5090 . However, if updating is to occur, one or more LRUs  1300  to be updated are selected at step  5055 . In an embodiment, there may also be a facility for selecting all of the LRUs  1300 , or of predefined groups of LRUs  1300  within the system  1000 . A list of DESIRED software components is then created by selecting in step  5055  various software components from in the available inventory. 
   At step  5065 , the lists of DESIRED components are sent out to the selected LRUs.  FIG. 6   a  schematically illustrates the download server transmitting a “desired software list” (i.e., the list of DESIRED software components) to the various LRUs  1300  within the system  1000 . The download server preferably executes an FTP “put” command to send the list of DESIRED components. 
   Referring to step  5070  in the method of  FIG. 5 , each of the LRUs  1300  independently compares the list of DESIRED software components to its current configuration file to determine whether the LRU  1300  needs any DESIRED software components.  FIG. 6   b  illustrates an example comparison, which could be performed by the LRU  1300  wherein two of the current LRU  1300  software components match the DESIRED software components of the “desired software list,” and wherein a software component  15543  does not match the DESIRED software component  23456 . The LRU  1300  independently seeks to obtain only the software components that it needs. Referring back to  FIG. 5 , at step  5075  of the method  5000 , each LRU executes an FTP “get” command to retrieve the missing or needed components from the configuration server, as illustrated schematically in  FIG. 6   c . Also, importantly, if a software component exists in the list of CURRENT software components, but not in the list of DESIRED software components, then that software component is deleted independently by each of the LRUs  1300  within the system  1000  that is completing step  5075 . 
   The selection and deselection of software components could be performed from an exemplary system configuration GUI  7000  illustrated in  FIG. 7 . The sample system configuration GUI  7000  shows a table of three columns labeled “LRU”, “SOFTWARE”, and “PART NUMBER”. The LRU column lists the configurable LRUs within the system, e.g., “LRU1A”, “LRU1B”, “LRU2A”, and so on. The row labeled “System” corresponds to the computer component designated to act as the configuration server  1200  ( FIG. 1 ). (Various components of the system  1000  as illustrated in  FIG. 2   a  are capable of functioning as the configuration server). Still referring to the system configuration GUI  7000  of  FIG. 7 , the SOFTWARE column and the PART NUMBER column contain lists of software component names and corresponding parts numbers, respectively. The respective components for each of the LRUs is listed separately. The checkboxes on the left side of  FIG. 6  allow the user to indicate which software components are to be installed on the particular LRU (notice that checkboxes do not appear next to the rows with the names of each LRU). As will be appreciated from  FIG. 7 , more than one checkbox may be selected simultaneously. According to an embodiment (not shown in  FIG. 7 ), the system configuration GUI  7000  could additionally include a means for selecting or deselecting all of the checkboxes. 
   At the bottom of  FIG. 7  are shown menu buttons, labeled “JAZ”, “DELETE”, etc. The DELETE button is used to remove software components from the list shown for each LRU. To remove a software component from the list shown, a user checks the box next to that component, then presses DELETE (either with a mouse or with his or her finger if it is a touch-sensitive display). The display is preferably then refreshed to show the new system configuration with the deleted software components missing. (This step is indicated by step  5040  in the method  5000  of  FIG. 5 ). The PRINT button is used to generate a printed copy of the system configuration display through a printing device connected to the system. The DONE button is used to return a user of the system to the previous “Update System, Update LRUs, or Done?” menu, previously described. 
   The menu buttons at the bottom of the display, labeled “JAZ”, “CD ROM”, and “FLOPPY” are used to load software components into the system that are not already shown in the system configuration display of  FIG. 7 . When a user of the system presses one of these buttons, for example, the CD ROM button, another display of the software components that have been loaded from that media is shown. 
   An example, according to an embodiment of the present invention, a GUI  8000  for a media load display of a CD ROM is shown in  FIG. 8 . Notice that one column, the STATUS column, appears in the media display that does not appear in the system configuration display of  FIG. 7 . The STATUS column indicates whether or not the software components recorded on the media have successfully loaded onto the download server. In the GUI  8000   FIG. 8 , in the row labeled “LRU2A”, there is shown in the STATUS column the message “FAILED”; such a message might indicate, for example, that the download server has reached its memory limit and is therefore unable to store the desired software component for LRU2A. A user of the system, for example, a maintenance person could have to delete some files from the download server (or add an additional download server) in order to make room for the additional software components to be loaded. When a user is finished selecting software components from the CD ROM, referring to a bottom of the GUI, the user can either press an UPDATE button to refresh the media load display or a DONE button to return to the system configuration display. According to another embodiment, the media load display could include other buttons for additional features, as desired, such as a DELETE button or a PRINT button (not shown). 
   Before updating the LRUs with software available from the inventory configuration server, it is desirable to perform the configuration checking method  3000  described above in connection with  FIG. 3 . In particular, the real time “manually initiated” processing of configuration information is preferably performed close in time prior to the step of sending the “DESIRED” list from the server  1200  to the target LRUs  1300  because it is desirable to be operating from the most current configuration information. 
   When the LRUs have reported their respective current configuration files, it can be displayed using, for example, a LRU Loading GUI  9000  as illustrated in  FIG. 9 . GUI  9000  additionally provides section checkboxes button for a user to select a particular group of LRUs to be updated. The ALL button could be selected when all of the LRUs within the LRU group are to be updated. In an embodiment, pressing the SINGLE button while one or more checkboxes for LRU groups are checked causes displays a menu with a list of individual LRUs within an LRU group for selection for update. The final selections from the GUIs  7000 ,  8000 ,  9000  are also to define the DESIRED configuration lists sent to each LRU at step  5065  of the method of  FIG. 5  and as illustrated in  FIG. 6   a.    
   In the GUI  9000  of  FIG. 9 , the checkboxes can be disabled as shown, for example, next to the System software components. This can be done to ensure that the system remains uniform prior to an initial download, or to block out LRUs that are known to be off line or unavailable. These checkboxes could, however, be enabled for selection after a first configuration and download. It is noted that software configuration of a particular IFES is typically customer dependent and must be kept uniform with the specifications of the system designer. 
   As mentioned in connection with step  5065  of the downloading method  5000  of  FIG. 5 , after selecting LRU groups or individual LRUs with either the ALL or the SINGLE button, the download server a list of the DESIRED configuration to each selected LRU. According to an embodiment of the present invention, an Ethernet broadcast or multicast using UDP (rather than TCP) sends the list. Each LRU, upon receipt of the parts list, performs a comparison with its current configuration, and compiles a list of the software components missing from its current configuration, and the LRU  1300  then requests a download of each needed component from the download server. The LRU request, in an embodiment, is made by opening an FTP session with the download server, and by executing an FTP “get” command for each software component needed. A plurality of FTP sessions and downloads can occur in parallel as limited by the bandwidth of the system and processing capacity of the download server. Of course, it is most preferred that the system is capable of handling an FTP “get” request from every LRU simultaneously. It is advantageous for the restricted architecture network  1000  to be capable of downloading software in a substantially parallel manner, resulting in significant time savings for configuring and downloading software to the plurality of LRUs  1300 . 
   According to an embodiment, after the LRU  1300  has received all of the requested new software components, the LRU sends a message to the configuration server  1200  indicating that file transfers are complete. The configuration server marks that LRU as needing “unpack”, and if the LRU has received all of the software components necessary for its configuration, the LRU reboots as indicated in step  5080  of the downloading method of  FIG. 5 . In an embodiment, the unpacking step  5085  is carried out by decompressing a compressed file format, such as a tar, rar or zip file format. The integrity check of  5085  might be any suitable method of checking a file for errors that may have been incurred by the file transfer, which are likely if, for example, the UDP protocol is used for transferring the files rather than the TCP protocol; a suitable method might comprise the calculation of a checksum, a cyclical redundancy check (CRC), or some other integrity checking algorithm. 
   An advantage of the present invention is that the target LRUs do not need to wait for the configuration and download of software for other target LRUs within the system to be completed before reboot. In an embodiment of the present invention, some or most of the LRUs  1300  within the system may be disconnected or not operational when another LRU  1300  is being configured and is receiving a software download. This creates substantial time savings during design, testing, and troubleshooting of a plurality of computers connected within a restricted architecture network. 
   After rebooting in step  5080 , LRUs  1300  that find downloaded files in a predefined location in their memory begin an integrity check, and if passed, unpack the files, as indicated by step  5085  of  FIG. 5 . The integrity check is necessary since, in an embodiment, the transfer protocol used may not provide error correction (TCP does, UDP does not); the unpack is necessary since, in an embodiment, the software components might be sent in a compressed or “packed” state that allows them to be sent more quickly. 
   Finally, the LRU sends its configuration file to the server  1200  (in an embodiment, the configuration server). The new system configuration information is displayed either on a laptop connected to the system by maintenance personnel, or by the management terminal  1100 . 
   It should be understood that various changes and modifications to the presently preferred embodiments described herein would be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages.