Patent Publication Number: US-10762160-B2

Title: Delivering content to electronic devices using local caching servers

Description:
RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 13/631,551, filed on Sep. 28, 2012, which is a continuation-in-part of, and hereby claims priority under 35 U.S.C. § 120 to, pending U.S. patent application Ser. No. 13/563,433, titled “Delivering Content to Electronic Devices using Local Caching Servers,” by the same inventors, which was filed on 31 Jul. 2012, and which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     Field 
     The disclosed embodiments relate to content delivery. More specifically, the disclosed embodiments relate to techniques for delivering content to electronic devices using local caching servers in the same local area networks (LANs) as the electronic devices. 
     Related Art 
     Recent improvements in computing power and wireless networking technology have significantly increased the capabilities of electronic devices. For example, laptop computers, tablet computers, portable media players, smart phones, digital media receivers, video game consoles, and/or other modern computing devices are typically equipped with WiFi capabilities that allow the computing devices to retrieve web pages, stream audio and/or video, share desktops and/or user interfaces (UIs), and/or transfer files wirelessly among one another. 
     Such increases in the capabilities and numbers of electronic devices have also expanded software distribution and digital content delivery to the electronic devices. For example, users of the electronic devices may frequently download music, movies, pictures, books, software updates, and/or applications from Internet-based content providers and/or content delivery networks onto the electronic devices. 
     On the other hand, bandwidth consumed by software distribution and digital content delivery may interfere with Internet usage and/or access from the electronic devices. For example, a digital textbook may be more than one gigabyte in size and take hours or days to download using a slower Internet connection at a school. In turn, downloading of the textbook onto thousands of electronic devices, each of which is assigned to one of thousands of students at the school, may take over a thousand hours to complete. Similarly, such downloading activity may consume a majority of available bandwidth on the Internet connection and slow web browsing and/or other Internet usage for users sharing the same Internet connection. Finally, the transmission of gigabytes or terabytes of data to the electronic devices may exceed an Internet Service Provider&#39;s (ISP&#39;s) bandwidth cap for the Internet connection, causing further slowdowns and/or increased charges for Internet access for the school. Consequently, delivery of content to large numbers of electronic devices using the same Internet connection may negatively impact the deployment and/or usage of the electronic devices. 
     SUMMARY 
     The disclosed embodiments provide a system that delivers content to an electronic device. The system includes a content provider that obtains a public address of the electronic device from a first request for the content from the electronic device. Next, the content provider uses the public address and a global server list to identify a local caching server on a local area network (LAN) of the electronic device. Finally, the content provider provides a local address of the local caching server to the electronic device, wherein the local address is used by the electronic device to obtain the content from the local caching server and the LAN without accessing a content delivery network (CDN) outside the LAN. 
     In some embodiments, the system also includes the local caching server. First, the local caching server obtains a second request for the content from the electronic device. lithe content is available on the local caching server, the local caching server provides the content to the electronic device through the LAN. If the content is not available on the local caching server, the local caching server downloads the content from the CDN, caches the downloaded content, and provides the downloaded content to the electronic device through the LAN. 
     In some embodiments, the content provider also provides the C to the electronic device, wherein the CDN is used by the electronic device to obtain the content upon detecting an error associated with obtaining the content from the local caching server. 
     In some embodiments, the error is associated with at least one of an unavailability of the local caching server, a corruption of the content, and an unsupported network topology between the electronic device and the local caching server. 
     In some embodiments, the local caching server also verifies the downloaded content. Upon receiving a notification of corruption of the downloaded content from the electronic device, the local caching server expedites verification of the downloaded content. Upon verifying corruption of the downloaded content, the local caching server flushes the content from the local caching server. 
     In some embodiments, verifying the downloaded content at the local caching server includes calculating a first checksum from a block of the downloaded content, and comparing the first checksum with a second checksum for the block from the CDN, 
     In some embodiments, a registration server also registers the local caching server. In some embodiments, registering the local caching server includes: obtaining registration information for the local caching server and, upon verifying the registration information, adding the local caching server to the global server list of local caching servers. 
     In some embodiments, verifying the registration information includes obtaining a certificate for the local caching server from the registration information, and validating the certificate. 
     In some embodiments, the registration information includes at least one of the certificate, a public address of the local caching server, a local address of the local caching server, and a globally unique identifier (GUID) for the local caching server. 
     In some embodiments, the content includes at least one of audio, video, an image, a book, a font, “voices,” a language dictionary, an application, and a software update. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a schematic of a system in accordance with the disclosed embodiments. 
         FIG. 2  shows a system for setting up a local caching server in accordance with the disclosed embodiments. 
         FIG. 3  shows a system for providing content in accordance with the disclosed embodiments. 
         FIG. 4  shows a flowchart illustrating the process of delivering content to an electronic device in accordance with the disclosed embodiments. 
         FIG. 5  shows a flowchart illustrating the process of providing content in accordance with the disclosed embodiments. 
         FIG. 6  shows a computer system in accordance with the disclosed embodiments. 
     
    
    
     In the figures, like reference numerals refer to the same figure elements. 
     DETAILED DESCRIPTION 
     The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. 
     Data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by an electronic device with computing capabilities. For example, the computer-readable storage medium can include volatile memory or non-volatile memory, including flash memory, random access memory (RAM, SRAM, DRAM, RDRAM, DDR/DDR2/DDR3 SDRAM, etc.), magnetic or optical storage mediums (e.g., disk drives, magnetic tape, CDs, DVDs), or other mediums capable of storing data structures or code. Note that in the described embodiments, the computer-readable storage medium does not include non-statutory computer-readable storage mediums such as transmission signals. 
     The methods and processes described in this detailed description can be included in hardware modules. For example, the hardware modules can include, but are not limited to, processing subsystems, microprocessors, application-specific integrated circuit (ASIC) chips, field-programmable gate arrays (FPGAs), and other programmable-logic devices. When the hardware modules are activated, the hardware modules perform the methods and processes included within the hardware modules. In some embodiments, the hardware modules include one or more general-purpose circuits that are configured by executing instructions (program code, firmware, etc.) to perform the methods and processes. 
     The methods and processes described in the detailed description section can be embodied as code and/or data that can be stored in a computer-readable storage medium as described above. When an electronic device with computing capabilities reads and executes the code and/or data stored on the computer-readable storage medium, the electronic device performs the methods and processes embodied as data structures and code and stored within the computer-readable storage medium. For example, in some embodiments, a processing subsystem can read the code and/or data from a memory subsystem that comprises a computer-readable storage medium, and can execute code and/or use the data to perform the methods and processes. 
     In the following description, we refer to “some embodiments.” Note that “some embodiments” describes a subset of all of the possible embodiments, but does not always specify the same subset of the embodiments. 
     The disclosed embodiments provide a method and system for providing content to an electronic device. As shown in  FIG. 1 , an electronic device  102  may use an Internet  106  connection to download content from a content delivery network (CDN)  104 . For example, electronic device  102  may be a desktop computer, laptop computer, tablet computer, portable media player, mobile phone, and/or other network-enabled device. In addition, electronic device  102  may request content such as audio, video, a font, “voices,” a language dictionary, an image, a book, an application, and/or a software update from a digital media store, software vendor, software update server, and/or other type of content provider. The content provider may respond to the request with information (e.g., a Uniform Resource Locator (URL)) for CDN  104 , and electronic device  102  may use the information to connect to CDN  104  and download the content from CDN  104 , 
     However, increased downloading of content from CDN  104  and/or other network nodes on Internet  106  by electronic device  102  and/or other electronic devices sharing a local area network (LAN)  110  with electronic device  102  may negatively impact use of Internet  106  and/or the electronic devices. For example, bandwidth consumed by downloads between the electronic devices and CDN  104  may slow web browsing and/or other types of Internet  106  access by other users and/or electronic devices on LAN  110 . The downloads may also exceed a bandwidth cap for an Internet Service Provider (ISP) associated with LAN  110 , incurring further slowdowns in accessing Internet  106  and/or additional charges by the ISP. 
     In one or more embodiments, the system of  FIG. 1  includes functionality to provide content to electronic device  102  and/or other electronic devices on LAN  110  using a local caching server  108  on LAN  110 . As described in further detail below, local caching server  108  may download content from CDN  104 , cache the downloaded content, and subsequently provide the downloaded content to electronic device  102  and/or the other electronic devices through LAN  110 . In turn, most or all of the electronic devices on LAN  110  may obtain the content without accessing Internet  106  and/or CDN  104 , thus mitigating issues associated with increased bandwidth consumption caused by downloading large amounts of content from CDN  104  and/or other network node on Internet  106 . 
       FIG. 2  shows a system for setting up local caching server  108  in accordance with the disclosed embodiments. As mentioned above, local caching server  108  may be connected to a LAN  110  of an electronic device, such as electronic device  102  of  FIG. 1 . A router  202  may connect the electronic device, local caching server  108 , and/or other electronic devices on LAN  110  to Internet  106 . In addition, devices on LAN  110 , including local caching server  108 , may share a public address  210  (e.g., public Internet Protocol (IP) address) with router  202 . 
     In one or more embodiments, local caching server  108  includes functionality to provide content such as video, audio, images, books, fonts, “voices,” language dictionaries, applications, and/or software updates to electronic devices connected to LAN  110 . To enable use of local caching server  108  by electronic devices on LAN  110 , local caching server  108  may be registered with a registration server  206 . To enable registration of local caching server  108  with registration server  206 , local caching server  108  may provide a hardware key  212 . for local caching server  108  to a certificate server  204 . If hardware key  212  is valid (e.g., identifies a valid local caching server), certificate server  204  may transmit a certificate  208  to local caching server  108 . 
     Next, local caching server  108  and/or a user (e.g., system administrator) may provide registration information containing certificate  208 , public address  210 , a local address  214  (e.g., local IP address on LAN  110 ) for local caching server  108 , LAN-specific information about local caching server  108  (e.g., a number of local caching servers on LAN  110 , a set of addresses served by local caching server  108 , etc.), and/or a globally unique identifier (GUID)  216  for local caching server  108  to registration server  206 . Registration server  206  may verify the registration information by validating certificate  208 . If certificate  208  is not valid, registration server  206  may omit registration of local caching server  108 , effectively preventing subsequent use of local caching server  108  in delivering content to electronic devices on LAN  110 . 
     If certificate  208  is valid, registration server  206  may add local caching server  108  to a global server list  218  of local caching servers. For example, registration server  206  may create an entry for local caching server  108  in global server list  218  and add public address  210 , local address  214 , the LAN-specific information, and GUM  216  from the registration information to the entry. The entry may then be used by content provider  302  to deliver content to electronic devices using local caching server  108  over LAN  110  instead of using 
     CDN  104  to deliver the content over the Internet  106  (and/or the Internet  106  in combination with other networks between CDN  104  and the electronic devices), as discussed in further detail below with respect to  FIG. 3 . 
     Finally, local caching server  108  may maintain the registration with registration server  206  by periodically transmitting a communication to registration server  206 . For example, local caching server  108  may transmit a “heartbeat” over Internet  106  every hour to registration server  206  to notify registration server  206  that local caching server  108  is available, functioning, and/or connected to Internet  106 . Conversely, if registration server  206  does not receive a communication from local caching server  108  after the pre-specified heartbeat interval (e.g., one hour) has passed, registration server  206  may assume that local caching server  108  is down and/or disconnected from Internet  106  and remove local caching server  108  from global server list  218 . In some embodiments, the heartbeat interval is communicated from registration server  206  to local caching server  108 . 
       FIG. 3  shows a system for delivering content  316  to electronic device  102  in accordance with the disclosed embodiments. Electronic device  102  may be connected to LAN  110  and share public address  210  with router  202 , which connects LAN  110  to Internet  106 . To download content  316  such as audio, video, images, applications, and/or software updates, electronic device  102  may send a first request  306  for content  316  to a content provider  302  on Internet  106 , such as a digital media store, software vendor, and/or software update server. 
     Instead of directing electronic device  102  to CDN  104 , where content  316  is hosted, content provider  302  may obtain public address  210  from request  306  and use public address  210  to identify local caching server  108  on LAN  110  of electronic device  102 . For example, content provider  302  may match public address  210  to an entry in global server list  218  for local caching server  108 . As described above, the entry may be added to global server list  218  during registration of local caching server  108  with a registration server (e.g., registration server  206  of  FIG. 2 ). As described below, using the public address to identify a local caching server can comprise performing one or more operations (mathematical, logical, etc.) to select a particular local caching server in cases where two or more local caching servers are available on the LAN  110 . 
     Content provider  302  may then provide a response  312  to request  306  containing local address  214  of local caching server  108 , MID  216 , and/or other information that allows electronic device  102  to identify and locate local caching server  108  on LAN  110 . In particular, electronic device  102  may use local address  214 , GUID  216 , and/or another identifier for local caching server  108  from response  312  to send a second request  308  for content  316  to local caching server  108  and obtain content  316  from local caching server  108  and LAN  110  instead of CDN  104  and Internet  106 . 
     As mentioned above, local caching server  108  may cache content  316  and/or other content from CDN  104  to reduce Internet  106  bandwidth consumed by electronic device  102  and/or other electronic devices on LAN  110  during downloads of the content from CDN  104 . If the requested content  316  is available (e.g., cached) on local caching server  108 , local caching server  108  may provide content  316  to electronic device  102  through LAN  110 . 
     If content  316  is not available on local caching server  108 , local caching server  108  may download content  316  from CDN  104 , cache the downloaded content  316 , and provide the downloaded content  316  to electronic device  102  through LAN  110 . For example, local caching server  108  may transmit a block of content  316  to electronic device  102  after downloading the block is downloaded from CDN  104 . To secure the caching of content  316  on local caching server  108 , local caching server  108  may also encrypt the block prior to writing the block to disk. Once downloading and caching of content  316  are complete, local caching server  108  may handle subsequent requests for content  316  from other electronic devices on LAN  110  by transmitting the cached content  316  to the electronic devices without accessing CDN  104  and/or Internet  106 . 
     Content provider  302  may also use a number of techniques to direct electronic device  102  and/or content from CDN  104  to local caching server  108  and/or other local caching servers with the same public address  210  (e.g., if multiple local caching servers reside on LAN  110 ). First, content provider  302  may ensure that content  316  and/or other content from CDN  104  is not duplicated among multiple local caching servers on LAN  110  by calculating a unique hash from a uniform resource identifier (URI) of the content (or any other suitable identifying value for the content) and dividing the hash by the number of local caching servers on LAN  110  to obtain a numerical remainder. For example, if a query of global server list  218  returns three different listings for local caching servers on LAN  110  (meaning that there are three local caching servers resident on LAN  110 ), content provider  302  may obtain a numerical remainder of 0, 1, or 2 from the division of the hash by the number of local caching servers for each unit of content requested by electronic device  102  and/or other electronic devices on LAN  110 . Content provider  302  may then direct requests for the content to the local caching server corresponding to the numerical remainder. In other words, content provider  302  may use the hash value and numerical remainder to track the allocation of content (e.g., content  316 ) from CDN  104  to different local caching servers (e.g., local caching server  108 ) within the same LAN (e.g., LAN  110 ) in lieu of a more computationally expensive tracking mechanism, such as storing the allocated content in global server list  218 . 
     in some embodiments, instead of computing the hash value from the URI of the content (or other identifying value of the content) and performing the division described above, content provider  302  can use another algorithm to assist in identifying a local caching server from among two or more local caching servers available on a LAN. For example, content provider  302  can use a round-robin selection mechanism in which local caching servers are selected in a round-robin pattern. Alternatively, content provider  302  can use a random selection, a weighted random selection, etc. Generally, any selection algorithm can be used that enables content provider  302  and/or the local caching server(s) on a LAN to effectively store content items and respond to requests for copies of content items. In these embodiments, content provider  302  can compute a selection value for the requested content (or based on the requested content, as described above) Content provider  302  can then use the selection value and information about two or more local caching servers available to an electronic device  102  to assist in identifying a particular local caching server to provide content to a requesting electronic device  102 . 
     In addition, content provider  302  may facilitate access to cached content within LAN  110  by obtaining address information from global server list  218  and selecting an appropriate local caching server for use by electronic device  102  and/or other electronic devices in LAN  110  based on the address information. For example, during the registration process, the administrator may provide a subnet, a range of local addresses (e.g., local address  214 ), etc. to be served by each local caching server on LAN  110  to registration server  206 . Registration server  206  may then store this information as address information for the corresponding local caching server(s). Content provider  302  may subsequently obtain a local address  318  for electronic device  102  from request  306  and match local address  318  with a particular local caching server using the address information from global server list  218 . Content provider  302  may also provide the local address of the local caching server to electronic device  102  to enable electronic device  102  to obtain the requested content from the local caching server. Content provider  302  may thus expedite downloading of cached content by an electronic device by ensuring that the electronic device downloads the content from a particular local caching server (e.g., a geographically closest local caching server to electronic device  102 , a fastest LAN connection between the local caching server and electronic device  102 , etc.) instead of other available local caching servers. 
     The system of  FIG. 3  may additionally include a number of mechanisms to protect content  316  from unauthorized access. First, local caching server  108  may verify the validity of a request (e.g., request  308 ) for content  316  from electronic device  102  by passing an authorization token from electronic device  102  to CDN  104  and enabling downloading of content  316  only if CDN  104  verifies the validity of the authorization token. Second, content provider  302  may restrict caching of certain types of content (e.g., copyrighted content) by local caching server  108  if public address  210  is detected to be in a country with legal and/or tax-based restrictions on the serving of such content, Third, content provider  302  may transmit push notifications to local caching server  108  to flush some or all of the cached content on local caching server  108  in cases where content provider  302  can determine that some or all of content  316  should be flushed from local caching server  108 . For example, content provider  302  can send a push message requesting that the flush of some or all of content  316  be performed when the content is determined to be illegal and/or harmful, when public address  210  is associated with a country that does not license the sale of the content (e.g., after local caching server  108  is relocated from a first country/region to a second country/region), when content has expired/become outdated/been determined to have a bug/flaw, and/or when local caching server  108  has not been used for a pre-specified period (e.g., two months). Finally, in some embodiments, local caching server  108  itself can automatically flush some or all of the content  316  upon determining that some or all of content  316  should no longer be provided by local caching server  108 . For example, local caching server  108  can flush the content when the content is determined to be illegal and/or harmful, when public address  210  is associated with a country that does not license the sale of the content, when content has expired/become outdated, and/or when local caching server  108  has not been used (e.g., been unplugged and/or not communicated with) for a pre-specified period (e.g., two months). 
     Content provider  302  may also include CDN  104  in response  312  to allow CDN  104  to operate as a failover for local caching server  108 . For example, electronic device  102  may encounter an error associated with obtaining content  316  from local caching server  108  if local caching server is down  108  and/or an unsupported network topology (e.g., double network address translation 
     (NAT), guest network, etc.) exists between electronic device  102  and local caching server  108 . To enable timely detection of the error, request  308  may include a short (e.g., 500 ms to 1 second) timeout interval. If local caching server  108  is not reachable after the timeout interval has lapsed, electronic device  102  may obtain a URL and/or other identifier for CDN  104  from response  312  and fall back to downloading content  316  from CDN  104 . 
     CDN  104  may further be used as a failover if content  316  is corrupted, either during transmission over Internet  106  and/or LAN  110  or as a result of disk corruption and/or failure on local caching server  108 . To detect such corruption, content  316  may be verified by both electronic device  102  and local caching server  108  while content  316  is transmitted to electronic device  102  and local caching server  108  from local caching server  108  and CDN  104 , respectively. For example, electronic device  102  and local caching server  108  may each calculate a first checksum (e.g., an MDS checksum) from a block of newly downloaded content  316  and compare the first checksum with a second checksum that is passed from CDN  104  through local caching server  108  to electronic device  102 . If the first and second checksums do not match, the block may be corrupted. 
     Because local caching server  108  may handle both downloading of content  316  from CDN  104  and transmission of the downloaded content  316  to electronic device  102 , local caching server  108  may not perform verification of content  316  in real-time. Instead, electronic device  102  may verify content  316  at a faster rate and switch to downloading content  316  from CDN  104  after corrupted content  316  is found. Electronic device  102  may also transmit a notification of corruption to local caching server  108  to inform local caching server  108  of the corrupted content  316 . 
     Upon receiving a notification of corruption from electronic device  102 , local caching server  108  may expedite verification of the downloaded content  316  by, for example, prioritizing the verification over other processes and/or tasks executing on local caching server  108 . If corruption of the downloaded content  316  is verified, local caching server  108  may flush the corrupted blocks of content  316  and re-download the blocks from CDN  104 . If corruption of content  316  is widespread and/or extensive, local caching server  108  may flush all of content  316  and re-download content  316  from CDN  104 . 
     Alternatively, upon detecting corruption in a block of content  316 , electronic device  102  may provide the second checksum and the byte range associated with the corrupted content to local caching server  108 , and local caching server  108  may compare the second checksum with a third checksum calculated from the cached content  316  on local caching server  108 . If local caching server  108  also detects corruption in the cached content (e.g., if the checksums do not match), local caching server  108  may re-download content  316  from CDN  104 . If local caching server  108  does not detect corruption in the cached content e.g., if the checksums match), local caching server  108  may determine that the corruption was caused during or after transmission of content  316  to electronic device  102  and re-transmit cached content associated with the byte range to electronic device  102 . Finally, if electronic device  102  continues detecting corruption in the same byte range after obtaining the re-transmitted content from local caching server  108 , electronic device  102  may switch to downloading content  316  from CDN  104 . 
     Local caching server  108  may additionally include functionality to manage caching of content  316  and/or other content on limited storage space on local caching server  108 . For example, local caching server  108  may allow an administrator and/or other user to allocate a percentage of the disk drive on local caching server  108  towards caching downloaded content (e.g., content  316 ). Local caching server  108  may also provide status and/or activity information associated with the amount (e.g., number of objects and/or bytes) of cached content provided by local caching server  108  and/or flushed from local caching server  108  because of space constraints over a pre-specified period (e.g., an hour, a day, a week, etc.). Finally, CDN  104  and/or local caching server  108  may mark certain types of content as “sticky” to prevent the content from being flushed from local caching server  108  if local caching server  108  runs out of storage space while downloading and/or caching more content from CDN  104 . 
     By using local caching server  108  to cache and provide content (e.g., content  316 ) to electronic device  102  and/or other electronic devices on LAN  110 , the system of  FIG. 3  may reduce Internet  106  usage and/or bandwidth consumption by the electronic devices during downloading of the content from CDN  104 . In turn, the system of  FIG. 3  may deliver the content more quickly, efficiently, and/or cheaply to the electronic devices than if CDN  104  were used to deliver the content to the electronic devices. For example, local caching server  108  may download content  316  once, cache content  316 , and transmit content  316  to multiple electronic devices on LAN  110  through a fast network connection on LAN  110 , thus significantly reducing the amount of Internet  106  bandwidth and/or time required to download content  316  to the electronic devices. 
     Furthermore, content provider  302  may control the behavior of the electronic devices in obtaining the content. For example, content provider  302  may enable use of local caching server  108  in providing content to the electronic devices if local caching server  108  is verified and/or operating correctly. Conversely, content provider  302  may remove local caching server  108  from global server list  218  and/or omit information for local caching server  108  from response  312  if local caching server  108  is unavailable, invalid, and/or buggy. In other words, use of local caching server  108  by the electronic devices may be based on the configuration, state, and behavior of both of local caching server  108  and content provider  302 . 
     Those skilled in the art will appreciate that the system of  FIG. 3  may be implemented in a variety of ways. First, content provider  302  may be provided by one or more servers, hosts, and/or software components. For example, the functionality of the registration server and content provider  302  may be implemented by a single server and/or component, and global server list  218  may be stored on the server and/or component. Alternatively, content provider  302  may include a content source that provides content  316  and/or other content available to electronic device  102  and receives requests (e.g., request  306 ) for the content from electronic device  102 . The content source may provide public address  210  to a selection mechanism that looks up local caching server  108  in global server list  218  based on public address  210 . The content source may then provide local address  214 , GUID  216 , and/or other information associated with local caching server  108  to the content source. Finally, the content source may transmit a response (e.g., response  312 ) to the request containing both the information for locating and using local caching server  108  and information for locating and using CDN  104  to electronic device  102 . 
     Second, local caching server  108  may be provided by a computer system, router, wireless base station, wireless access point, and/or other network-enabled device on LAN  110 . Moreover, local caching server  108  may be located by electronic device  102  and/or other electronic devices on LAN  110  using a. number of techniques. For example, local caching server  108  may use a discovery protocol such as Bonjour (Bonjour™ is a registered trademark of Apple Inc.) to register with LAN  110  and advertise a local-caching service on LAN  110 . Electronic devices on LAN  110  may also use the discovery protocol to discover local caching server  108 , connect to local caching server  108 , and obtain content from local caching server  108 . Alternatively, the electronic devices may use the discovery protocol to discover local caching server  108  and/or other local caching servers on LAN  110  and query content provider  302  for the local caching server responsible for caching the type of content (e.g., books, movies, music, applications, software updates, etc.) requested by the electronic devices. 
       FIG. 4  shows a flowchart illustrating the process of delivering content to an electronic device in accordance with the disclosed embodiments. In one or more embodiments, one or more of the steps may be omitted, repeated, and/or performed in a different order. Accordingly, the specific arrangement of steps shown in  FIG. 4  should not be construed as limiting the scope of the technique. 
     Initially, a local caching server is registered to enable use of the local caching server (operation  402 ) by the electronic device. To register the local caching server, a registration server may obtain registration information for the local caching server, including a certificate for the local caching server. The registration server may then verify the registration information by, for example, validating the certificate. Once the registration information is verified, the registration server may add the local caching server to a global server list of local caching servers. 
     Next, a request for content may be received from the electronic device (operation  404 ). For example, the electronic device may request audio, video, images, books, applications, and/or software updates from the content provider. If no request for content is received, information associated with accessing the content is not provided to the electronic device. If a request for content is received, a public address of the electronic device is obtained from the request (operation  406 ), and the public address is used to identify the local caching server on the LAN of the electronic device (operation  408 ). For example, the local caching server may be identified by obtaining a public IP address of the electronic device from the request and matching the public IP address to an entry for the local caching server in the global server list. As described above, this operation can include using address information from the global server list to determine a particular one of two or more local caching servers on the same LAN as the electronic device that is to be used to acquire the requested content. 
     Once the local caching server is identified, the local address of the local caching server is provided to the electronic device (operation  410 ). For example, a local IP address and/or GUID of the local caching server on the LAN may be transmitted to the electronic device, and the electronic device may use the local IP address to obtain the content from the local caching server and the LAN without accessing a CDN outside the LAN. 
     The CDN may also be provided to the electronic device (operation  412 ). For example, a URL and/or other identifier for the CDN may be provided to the electronic device to allow the electronic device to obtain the content upon detecting an error (e.g., unavailability of the local caching server, corruption of the content, unsupported network topology, etc.)associated with obtaining the content from the local caching server. In other words, the CDN may serve as a failover for the local caching server. 
     Registration of the local caching server may be maintained (operation  414 ) independently of the handling of requests for content from the electronic device and/or other electronic devices on the LAN. For example, the local caching server may continue to be registered with the registration server as long as the local caching server transmits a periodic “heartbeat” to the registration server. If registration of the local caching server is to be maintained, requests for content from electronic devices in the same LAN as the local caching server may be processed by providing the local address of the local caching server and/or the CDN in responses to the requests (operations  404 - 412 ). Such directing of the requests for content to the local caching server may continue until the local caching server is no longer registered (i.e., is no longer listed on the global server list). 
       FIG. 5  shows a flowchart illustrating the process of providing content in accordance with the disclosed embodiments. In one or more embodiments, one or more of the steps may be omitted, repeated, and/or performed in a different order. Accordingly, the specific arrangement of steps shown in  FIG. 5  should not be construed as limiting the scope of the technique. 
     First, a local caching server is registered with a registration server outside a LAN of the local caching server (operation  502 ). To enable registration of the local caching server, the local caching server may provide a hardware key for the local caching server to a certificate server and obtain a certificate from the certificate server. The local caching server may then provide registration information containing the certificate, a public address of the local caching server, a local address of the local caching server, LAN-specific information, and/or a GUID for the local caching server to the registration server. If the registration information is verified by the registration server, the local caching server may be added to a global server list of local caching servers, as discussed above. 
     In some embodiments, the LAN-specific information provided for the local caching server during the registration operation can include any information that can subsequently be used to determine whether a given local caching server is to be selected to provide particular content. This includes any information that can subsequently be used to determine whether a given local caching server from among two or more local caching servers available on the LAN is to be selected to provide the particular content. For example, in some embodiments, the LAN-specific information comprises information such as a number and/or arrangement of local caching servers on the LAN, information about the subnets/network addresses served by the local caching server, configurations of the local caching servers, hardware/software available on the local caching servers, etc. For example, a system administrator and/or a local caching server can specify one or more subnets served by a local caching server during the registration process. In some embodiments, the registration server itself can determine or infer the LAN-specific information for local caching servers based on registration information provided by two or more local caching servers (e.g., matching public addresses, etc.) and can add the LAN-specific information to the global server list. 
     After the local caching server is registered, the local caching server may receive a request for content (operation  504 ) from an electronic device on the same LAN as the local caching server. For example, the electronic device may transmit the request for content to the local caching server after requesting the content from a content provider and obtaining a local address and/or GUM of the local caching server from the content provider. If no request for content is received, content is not provided by the local caching server. If a request for content is received, the request may be handled based on the availability of the content on the local caching server (operation  506 ). If the content is available (e.g., cached) on the local caching server, the local caching server is used to provide the content to the electronic device through the LAN (operation  508 ). 
     If the content is not available on the local caching server, the content is downloaded from the CDN (operation  510 ), and the downloaded content is verified (operation  512 ). For example, the content may be verified by calculating a first checksum from a block of the downloaded content and comparing the first checksum with a second checksum for the block from the CDN. Because the local caching server may verify the content more slowly than the electronic device, the local caching server may receive a notification of corruption (operation  514 ) of the downloaded content from the electronic device before detecting the corrupted content. If a notification of corruption is not received, the downloaded content is cached (operation  520 ), and the local caching server is used to provide the downloaded content to the electronic device through the LAN (operation  508 ). 
     If a notification of corruption is received, verification of the downloaded content is expedited (operation  516 ) while the electronic device switches to downloading the content from the CDN. Once the corruption is verified, the corrupted content is flushed from the local caching server (operation  518 ), re-downloaded (operation  510 ), and re-verified (operation  512 ). Downloading, verification, and caching of the content may continue (operation  510 - 520 ) until the content is fully downloaded, cached, and verified to not be corrupted. 
     Registration of the local caching server may be maintained (operation  522 ) independently of handling requests for content from electronic devices on the LAN. For example, registration of the local caching server may be maintained while the local caching server is available to provide content to the electronic devices. If registration of the local caching server is to be maintained, a communication is periodically transmitted from the local caching server to the registration server (operation  524 ). For example, the local caching server may transmit a “heartbeat” every hour to the registration server to notify the registration server that the local caching server is available, functioning, and connected to the Internet. The local caching server may thus continue handling requests for content from the electronic devices (operation  504 - 520 ) until the local caching server is no longer configured to provide content to the electronic devices and/or registered with the registration server. 
       FIG. 6  shows a computer system  600  in accordance with the disclosed embodiments. Computer system  600  may correspond to an apparatus that includes a processor  602 , memory  604 , storage  606 , and/or other components found in electronic computing devices. Processor  602  may support parallel processing and/or multi-threaded operation with other processors in computer system  600 . Computer system  600  may also include input/output (I/O) devices such as a keyboard  608 , a mouse  610 , and a display  612 . 
     Computer system  600  may include functionality to execute various components of the present embodiments. In particular, computer system  600  may include an operating system (not shown) that coordinates the use of hardware and software resources on computer system  600 , as well as one or more applications that perform specialized tasks for the user. To perform tasks for the user, applications may obtain the use of hardware resources on computer system  600  from the operating system, as well as interact with the user through a hardware and/or software framework provided by the operating system. 
     In one or more embodiments, computer system  600  provides a system for delivering content to an electronic device. The system may include a registration server that registers a local caching server to enable use of the local caching server by the electronic device (although in some embodiments, the registration server is implemented in one or more other computer systems  600 ). 
     The system may also include a content provider that obtains a public address of the electronic device from a first request for the content from the electronic device. Next, the content provider may use the public address to identify the local caching server on a LAN of the electronic device. Finally, the content provider may provide a local address of the local caching server to the electronic device. 
     The electronic device may then use the local address to obtain the content from the local caching server and the LAN without accessing a content delivery network (CDN) outside the LAN. 
     Alternatively, computer system  600  may implement the local caching server. The local caching server may obtain a second request for the content from the electronic device (e.g., after the electronic device obtains the local address of the local caching server from the content provider). If the content is available on the local caching server, the local caching server may provide the content to the electronic device through the LAN. If the content is not available on the local caching server, the local caching server may download the content from a content delivery network (CDN) outside the LAN, cache the downloaded content, and provide the downloaded content to the electronic device through the LAN. 
     In addition, one or more components of computer system  600  may be remotely located and connected to the other components over a network. Portions of the present embodiments (e.g., local caching server, certificate server, registration server, content provider, etc.) may also be located on different nodes of a distributed system that implements the embodiments. For example, the present embodiments may be implemented using a cloud computing system that directs a set of remote electronic devices to download content from a set of local caching servers on LANs of the electronic devices. 
     The foregoing descriptions of various embodiments have been presented only for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art Additionally, the above disclosure is not intended to limit the present invention.