Method, apparatus and related device for redirecting interconnection route of content distribution network

Abstract

The present disclosure provides a content distribution network interconnection routing redirection method and device and related equipment, and relates to the field of computer networks and information technology. The method is applied to a content distribution network interconnection system, the content distribution network interconnection system comprises multiple downstream content distribution networks, and the method comprises the following steps: receiving a redirection request sent by a downstream content distribution network to be redirected; and sending a target service request to a target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides target services. The present disclosure allows direct cooperation between downstream content distribution networks, and can reduce the dependence on real-time scheduling of upstream content distribution networks.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of computer networks and information technology, and particularly relates to a content delivery network interconnection routing redirection method and device and related equipment. BACKGROUND

[0002] A content delivery network (CDN) improves access speed and reduces latency by deploying edge nodes globally and caching content close to users. However, the coverage of a single CDN is usually limited by the geographical distribution and resource configuration of its infrastructure, making it difficult to achieve comprehensive coverage globally. This means that in some areas, users may not be able to obtain ideal service quality. To solve this problem, content delivery network interconnection (CDNI) has emerged. CDNI enables multiple independent CDNs to interconnect and work together through standardized interfaces and mechanisms, thereby expanding the coverage of content delivery and improving the availability and reliability of services. Through CDNI, content providers can utilize the combined resources of multiple CDNs to achieve more extensive content delivery and meet the needs of global users.

[0003] The CDNI architecture in the related art is a mechanism for coordinating multiple downstream CDNs for content services by an upstream CDN. Its core goal is to enable content service providers to interface with an upstream CDN through CDNI, and the CDN coverage of the upstream CDN can be extended to other CDNs. In the related art, the service scheduling of downstream CDNs needs to be decided uniformly by the upstream CDN. When a downstream CDN node needs to migrate services due to cache invalidation or performance degradation, the request must be returned to the upstream CDN for reallocation, which will cause the following problems:

[0004] 1) Increase the number of content service path hops, resulting in significant latency;

[0005] 2) The upstream CDN becomes a scheduling bottleneck, affecting the overall scalability of the system;

[0006] 3) Downstream CDNs cannot independently respond to temporary service emergencies and lack flexibility.

[0007] As shown in the prior art CDNI service migration process: Figure 1

[0008] 1) Downstream CDN1 has a service problem, triggers the migration process, and initiates a redirection request to the client;

[0009] 2) The client receives the redirection request and initiates a service request to the upstream CDN according to the redirection signaling;​

[0010] 3), the upstream CDN queries its service capability or other downstream CDN service capability, and guides the client to the downstream CDN 3 service through redirection, it can be seen that the process in the related art needs to dispatch the service request back to the upstream CDN and then dispatch it again by the upstream CDN.

[0011] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present disclosure, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0012] The present disclosure provides a content distribution network interconnection routing redirection method and device and related equipment, which at least reduces the dependence on real-time scheduling of the upstream CDN in the related art, and improves the service stability, response efficiency and scalability of the edge CDN.

[0013] Other characteristics and advantages of the present disclosure will become apparent from the following detailed description, or will be learned by practice of the present disclosure.

[0014] According to one aspect of the present disclosure, a content distribution network interconnection routing redirection method is provided, characterized in that it is applied to a content distribution network interconnection system including a plurality of downstream content distribution networks, and the method comprises: receiving a redirection request sent by a downstream content distribution network to be redirected; and sending a target service request to a target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides a target service.

[0015] In some exemplary embodiments of the present disclosure, based on the foregoing scheme, the content distribution network interconnection system includes an upstream content distribution network, and before receiving the redirection request sent by the downstream content distribution network to be redirected, the method further comprises: determining an interfacing strategy between the upstream content distribution network and a plurality of downstream content distribution networks based on a content distribution network interconnection protocol, the content distribution network interconnection protocol being used for the upstream content distribution network to identify and connect to the downstream content distribution network; and generating a core shared routing table according to the interfacing strategy, the core shared routing table being used to store network service configuration information of the upstream content distribution network and a plurality of downstream content distribution networks.

[0016] In some example embodiments of the present disclosure, based on the foregoing scheme, after the core shared routing table is generated, the method further comprises: based on the network service configuration information of the plurality of downstream content distribution networks in the core shared routing table, generating an associated shared routing table corresponding to the plurality of downstream content distribution networks, wherein the associated shared routing table is associated with the core shared routing table and is configured to store relevant information generated according to the data records in the core shared routing table.

[0017] In some example embodiments of the present disclosure, based on the foregoing scheme, the redirection request is generated according to the associated shared routing table corresponding to the downstream content distribution network to be redirected.

[0018] In some example embodiments of the present disclosure, based on the foregoing scheme, after the core shared routing table is generated according to the docking strategy, the method further comprises: updating the core shared routing table when the downstream content distribution network changes; and updating the associated shared routing table corresponding to the downstream content distribution network according to the network service configuration information of the downstream content distribution network in the updated core shared routing table.

[0019] In some example embodiments of the present disclosure, based on the foregoing scheme, before the target service request is sent to the target downstream content distribution network according to the redirection request, the method further comprises: controlling the downstream content distribution network to be redirected and the target downstream content distribution network to complete authentication through asymmetric key signature.

[0020] In some example embodiments of the present disclosure, based on the foregoing scheme, the downstream content distribution network only reads the associated shared routing table.

[0021] According to another aspect of the present disclosure, there is also provided a redirection device for content distribution network interconnection routing, characterized by being applied in a content distribution network interconnection system, the content distribution network interconnection system comprising a plurality of downstream content distribution networks, the device comprising: a redirection request receiving module configured to receive a redirection request sent by a downstream content distribution network to be redirected; and a target service request sending module configured to send a target service request to a target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides a target service.

[0022] According to still another aspect of the present disclosure, there is also provided a redirection system for content distribution network interconnection routing, characterized by comprising: a downstream content distribution network configured to send a redirection request and receive a target service request; and a client configured to receive a redirection request sent by a downstream content distribution network to be redirected, send a target service request to a target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides a target service.

[0023] According to still another aspect of the present disclosure, there is also provided an electronic device comprising: a processor; and a memory for storing executable instructions of the processor; wherein the processor is configured to perform the redirection method of interconnecting routing of content distribution networks of any of the above by executing the executable instructions.

[0024] According to yet another aspect of the present disclosure, there is also provided a computer-readable storage medium having stored thereon a computer program, the computer program being executed by a processor to implement the redirection method of interconnecting routing of content distribution networks of any of the above.

[0025] According to another aspect of the present disclosure, there is also provided a computer program product comprising: a computer program or instructions, the computer program or instructions being executed by a processor to implement the redirection method of interconnecting routing of content distribution networks of any of the above.

[0026] The redirection method of interconnecting routing of content distribution networks, apparatus and related device provided in the embodiments of the present disclosure, the downstream content distribution network to be redirected sends a redirection request, and sends a target service request to a target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides target service. Compared with the service scheduling of the related art downstream content distribution network, which needs to be uniformly decided by the upstream content distribution network, when the downstream content distribution network node needs to migrate service due to cache invalidation or performance decline, the request must be returned to the upstream content distribution network for reallocation. The embodiments of the present disclosure break through the bottleneck of traditional content distribution network interconnection relying on the upstream content distribution network, and when the service of a certain downstream content distribution network is abnormal, the user request can be redirected directly without passing through the upstream content distribution network, which greatly improves the migration efficiency and security.

[0027] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0028] The drawings incorporated into the specification and forming a part thereof illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the disclosure. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0029] Figure 1 A content distribution network interconnection service migration schematic diagram in the related art is shown;

[0030] Figure 2An exemplary application system architecture schematic diagram of a redirection method of content distribution network interconnection routing in an embodiment of the present disclosure is shown.

[0031] Figure 3 An exemplary application system architecture schematic diagram of a redirection method of content distribution network interconnection routing in an embodiment of the present disclosure is shown.

[0032] Figure 4 An exemplary application system architecture schematic diagram of a service migration of content distribution network interconnection in an embodiment of the present disclosure is shown.

[0033] Figure 5 An exemplary application system architecture schematic diagram of a generation and update process of core SRT and associated SRT in an embodiment of the present disclosure is shown.

[0034] Figure 6 An exemplary application system architecture schematic diagram of a redirection device of content distribution network interconnection routing in an embodiment of the present disclosure is shown.

[0035] Figure 7 An exemplary application system architecture schematic diagram of a redirection system of content distribution network interconnection routing in an embodiment of the present disclosure is shown.

[0036] Figure 8 An exemplary application system architecture schematic diagram of a redirection method of content distribution network interconnection routing in an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0037] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations can be implemented in any

[0038] Moreover, described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the techniques described can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, devices, implementations, and operations have not been shown or described in detail to avoid obscuring aspects of the disclosure.

[0039] The flow diagrams shown in the figures are merely exemplary and do not necessarily include all of the content and operations / acts, or necessarily include them in the order shown. For example, some operations / acts can be combined or separated into different operations / acts, and some operations / acts can be performed at the same time or in a different order than shown. Actual implementation can vary from the described example.

[0040] Figure 2 An exemplary application system architecture diagram to which the redirection method of the content distribution network interconnection routing in the embodiments of the present disclosure can be applied is shown. As shown in the figure, the system architecture can include a terminal device 201, a network 202, and a server 203. Figure 2

[0041] The network 202 is a medium for providing a communication link between the terminal device 201 and the server 203, which can be a wired network or a wireless network.

[0042] Optionally, the wireless network or the wired network described above uses standard communication technologies and / or protocols. The network is usually the Internet, but can also be any network, including but not limited to a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), a mobile, wired or wireless network, a private network or any combination of virtual private networks). In some embodiments, technologies and / or formats including Hyper Text Mark-up Language (HTML), Extensible Markup Language (XML), etc. are used to represent data exchanged through the network. In addition, all or some links can be encrypted using conventional encryption technologies such as Secure Socket Layer (SSL), Transport Layer Security (TLS), Virtual Private Network (VPN), Internet Protocol Security (IPsec), etc. In other embodiments, custom and / or dedicated data communication technologies can be used instead of or in addition to the above data communication technologies.

[0043] The terminal device 201 can be various electronic devices, including but not limited to a smartphone, a tablet computer, a laptop computer, a desktop computer, a wearable device, an augmented reality device, a virtual reality device, etc.

[0044] Optionally, the clients of the application programs installed in different terminal devices 201 are the same, or the clients of the same type of application programs based on different operating systems. Based on the difference in terminal platforms, the specific form of the client of the application program can also be different, for example, the application program client can be a mobile phone client, a PC client, etc.

[0045] ​The server 203 can be a server that provides various services, such as a background management server that provides support for operations performed by a user using the terminal device 201. The background management server can analyze and process received request data, and feed back the processing result to the terminal device.

[0046] Optionally, the server can be a standalone physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, CDN (Content Delivery Network), and basic cloud computing services such as big data and artificial intelligence platforms. The terminal can be a smartphone, a tablet computer, a notebook computer, a desktop computer, a smart speaker, a smart watch, and the like, but is not limited thereto. The terminal and the server can be directly or indirectly connected through wired or wireless communication, which is not limited in the present application.

[0047] Those skilled in the art can know that, Figure 2 The number of terminal devices, networks and servers in the above system architecture is only illustrative, and any number of terminal devices, networks and servers can be provided according to actual needs. The present disclosure does not limit this.

[0048] Under the above system architecture, the present disclosure provides a content distribution network interconnection routing redirection method, which can be executed by any electronic device with computing processing capability.

[0049] In some embodiments, the content distribution network interconnection routing redirection method provided in the present disclosure can be executed by the terminal device of the above system architecture; in other embodiments, the content distribution network interconnection routing redirection method provided in the present disclosure can be executed by the server in the above system architecture; in other embodiments, the content distribution network interconnection routing redirection method provided in the present disclosure can be realized by the terminal device and the server in the above system architecture through interaction.

[0050] For the convenience of subsequent understanding, the present disclosure will explain the professional terms designed below:

[0051] Content Delivery Network Interconnection (CDNI) is a set of interfaces and mechanisms for connecting two or more independent content delivery networks (CDN). Through CDNI, CDNs can work together to expand service coverage, improve service quality, reduce infrastructure costs, and enhance the availability and flexibility of content delivery.

[0052] Shared Routing Table (SRT) is a structure for coordinating service capabilities and routing information between upstream CDN (UCDN) and downstream CDN (DCDN), the core SRT is maintained by UCDN, containing service capabilities, load status, key information, etc. of each DCDN; the associated SRT is a read-only copy of the core SRT, distributed to each DCDN node, when a DCDN service is abnormal, it can autonomously select other DCDN for service migration based on the information of the associated SRT, without the real-time intervention of UCDN, thereby realizing more efficient content distribution and stronger system flexibility.

[0053] Firstly, the embodiment of the present disclosure provides a mechanism compatible with CDNI standard, allowing direct cooperation between DCDNs, breaking through the bottleneck of traditional CDNI relying on UCDN, designing a hierarchical SRT, realizing direct cooperation between DCDNs, UCDN dynamically generating a core SRT (containing service capabilities, key pool, URL conversion rules), and synchronizing a read-only associated SRT to each DCDN, when a DCDN service is abnormal, it can autonomously redirect requests to the optimal DCDN based on the service weight (such as load, delay) of the associated SRT, and complete token verification (issuer private key encryption, target public key decryption) using an asymmetric key signature mechanism, without the real-time intervention of dCDN cooperation; the embodiment of the present disclosure is compatible with CDNi standard, and can be applied to various scenarios such as interconnection of traditional CDN and edge CDN, CDN node disaster recovery, etc., and has the value of large-scale deployment.

[0054] Figure 3 A redirection method of content distribution network interconnection routing in the embodiment of the present disclosure is shown, the method is applied to a content distribution network interconnection system, the content distribution network interconnection system includes a plurality of downstream content distribution networks, including the following steps:

[0055] S302, receiving a redirection request sent by a downstream content distribution network to be redirected.

[0056] It should be noted that the DCDN in the embodiments of the present disclosure refers to a CDN node or system located close to the client in the network structure, responsible for directly providing services to users. It is assumed that a global video streaming company uses multiple CDNs to cover different geographic areas, and a CDN dedicated to serving the Asian region can be considered as a DCDN. In addition, the redirection request in the embodiments of the present disclosure is that when a certain DCDN cannot provide services to users due to excessive load, maintenance or other reasons, the DCDN will send a redirection request to another more suitable DCDN, requiring the user's request to be directed to the DCDN. For example, the DCDN in the Asian region detects that its server is close to full load operation, and it can send a redirection request to another DCDN in the European region to ensure that users can continue to watch videos smoothly.

[0057] S304, sending a target service request to the target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides a target service.

[0058] It should be noted that the target downstream content distribution network in the embodiments of the present disclosure refers to a CDN that is currently processing user requests but needs to transfer the request to other DCDNs for some reason; once the target DCDN is determined, the DCDN to be redirected will send a target service request to the target DCDN, informing it that it is ready to receive and provide the target service corresponding to the user's demand.

[0059] The redirection method of the content distribution network interconnection route provided in the embodiments of the present disclosure first receives the redirection request sent by the downstream content distribution network to be redirected; then, according to the redirection request, a target service request is sent to the target downstream content distribution network, so that the target downstream content distribution network provides a target service. Compared with the service scheduling of the related art downstream content distribution network, which needs to be uniformly decided by the upstream content distribution network, when the downstream content distribution network node needs to migrate services due to cache invalidation or performance degradation, the request must be returned to the upstream content distribution network for reallocation. The embodiments of the present disclosure break through the bottleneck of traditional content distribution network interconnection relying on the upstream content distribution network, and when a certain downstream content distribution network service is abnormal, the user request can be redirected directly through the upstream content distribution network, greatly improving the migration efficiency and security.

[0060] In some embodiments, the content distribution network interconnection system in the embodiments of the present disclosure includes an upstream content distribution network. Before receiving a redirection request sent by a downstream content distribution network to be redirected, the redirection method of the content distribution network interconnection in the embodiments of the present disclosure further includes: determining an interfacing strategy between the upstream content distribution network and a plurality of downstream content distribution networks based on a content distribution network interconnection protocol, the content distribution network interconnection protocol being used for enabling the upstream content distribution network to identify and connect to the downstream content distribution network; and generating a core shared routing table according to the interfacing strategy, the core shared routing table being used to store network service configuration information of the upstream content distribution network and the plurality of downstream content distribution networks. Specifically, through the core shared routing table, the UCDN can identify the service capabilities and states (such as geographic coverage, load condition, cache hit rate, etc.) of each DCDN, so as to dynamically select the optimal content distribution path according to the current network condition, which helps to reduce the delay and improve the content delivery speed. In addition, based on the information in the SRT, the UCDN can more reasonably allocate traffic to different DCDNs, avoid overloading of a single node, and ensure the stability and reliability of the overall system. In addition, the SRT in the embodiments of the present disclosure not only contains basic service configuration information, but also can store a key pool and content identifier conversion rules. For example, when sensitive data is transmitted, the security of the information can be protected by using the key provided by the quantum encryption technology. It should be noted that, in some embodiments, the network service configuration information in the embodiments of the present disclosure includes CDN service capabilities, metadata, a key pool, and service request uniform resource locator (URL) rules of each CDN, and the like.

[0061] In some embodiments, the embodiments of the present disclosure construct a hierarchical shared routing table structure with the core SRT and the associated SRT. Specifically, the UCDN maintains the core SRT, which records the service capabilities, load states, protocol support, key pool, and content identifier conversion rules of all CDN nodes. Each DCDN node holds a read-only copy of the associated SRT, and can decide whether to initiate service migration to other DCDNs based on the copy.

[0062] In some embodiments, the core SRT data structure in the embodiments of the present disclosure includes: CDN identification, service capability, content distribution network interconnection strategy, and key pool. Specifically, the CDN identification in the embodiments of the present disclosure is used to uniquely identify each CDN (for example, CDN-ID). The service capability in the embodiments of the present disclosure includes: geographical coverage (Footprint): geographical area (for example, country, city) supported by the CDN; load status: current load (for example, CPU usage, bandwidth utilization); cache hit rate: hit rate of content cache, reflecting content availability; delay performance: average distribution delay of the CDN (for example, calculated based on historical data); supported protocol: supported content distribution protocol (such as HTTP / 2, QUIC). The content distribution network interconnection strategy in the embodiments of the present disclosure includes: content distribution strategy: for example, geographical restriction, access control strategy; content identification definition: content identification (URL composition and parameter definition) of the CDN service. The key pool in the embodiments of the present disclosure includes: public key of the DCDN.

[0063] In some embodiments, the associated SRT data structure in the embodiments of the present disclosure includes: CDN identification, service routing identification, service routing weight, content identification conversion, and key pool. Specifically, the CDN identification in the embodiments of the present disclosure is used to uniquely identify each CDN. The service routing identification in the embodiments of the present disclosure is used to uniquely identify each service, including CDN-ID and service capability ID (HTTP2, QUIC, etc.). The service routing weight in the embodiments of the present disclosure is the service weight corresponding to each cooperative CDN (which can be represented by a Cost value), and the DCDN decides to which CDN (UCDN or other DCDN) to redirect the service according to the value. The content identification conversion in the embodiments of the present disclosure is used to convert the regular expression of the content service identification, which can convert the original service URL to the corresponding URL of the target CDN. The key pool in the embodiments of the present disclosure includes the public key of each CDN.

[0064] In some embodiments of this disclosure, after generating the core shared routing table, the method for redirecting interconnected routes of content delivery networks further includes: generating multiple associated shared routing tables corresponding to multiple downstream content delivery networks based on the network service configuration information of multiple downstream content delivery networks in the core shared routing table. The associated shared routing tables are associated with the core shared routing table and configured to store relevant information generated based on data records in the core shared routing table. Specifically, each DCDN in this disclosure can have a specially customized associated shared routing table according to its own characteristics and service needs. This allows the DCDN to more accurately manage and optimize its internal resource allocation and service strategies without relying on a general core SRT. Furthermore, since the associated SRT is generated based on data records in the core SRT, it typically only contains information relevant to that DCDN, reducing the amount of data queried and processed, and helping to speed up the decision-making process. Additionally, if a DCDN fails or becomes unavailable, other DCDNs can identify alternative service providers by checking their own associated SRTs, ensuring continued high-quality service even in the event of localized network problems.

[0065] In some embodiments, such as Figure 4 As shown in the embodiments of this disclosure, the device applying the redirection method for content delivery network interconnection routing needs to have UCDN and DCDN. UCDN includes UCDN nodes and a core SRT, and DCDN includes DCDN nodes and associated SRTs. More specifically, the core SRT is used to store information such as CDN service capabilities, metadata, key pool, and service request URL rules for each CDN. UCDN manages the core SRT and generates and periodically updates the associated SRTs of each DCDN based on the core SRT and the connection strategy between UCDN and DCDN. The associated SRT is used to store routing information and serves as the service capabilities and metadata of the DCDN. DCDN manages the associated SRT and migrates services to other DCDNs when the service quality cannot be met based on the associated SRT. The corresponding DCDN should be able to verify whether it can provide the corresponding service based on the migrated service request through its corresponding associated SRT.

[0066] In some embodiments, such as Figure 4As shown, the redirection request in the embodiment of the present disclosure is generated according to the associated shared routing table corresponding to the downstream content distribution network to be redirected. Specifically, the embodiment of the present disclosure sets a core SRT on the UCDN, sets an associated SRT on each DCDN, and the DCDN can directly redirect user requests to other DCDNs through the associated SRT. It should be noted that the SRT does not change the relationship between the UCDN and the DCDN in the existing content distribution network interconnection, but can skip the UCDN to directly redirect user requests, greatly improving the migration efficiency and security.

[0067] In some embodiments, as Figure 4 As shown, after generating the core shared routing table according to the docking strategy, the redirection method of the content distribution network interconnection routing in the embodiment of the present disclosure further includes: updating the core shared routing table when the downstream content distribution network changes; and updating the associated shared routing table corresponding to the downstream content distribution network according to the network service configuration information of the downstream content distribution network in the updated core shared routing table. Specifically, when the service capability, load state, protocol support, etc. of the DCDN change, timely updating the core SRT and the associated SRT can ensure that all relevant parties obtain the latest and accurate information, avoiding incorrect decisions or inefficient operations due to outdated information; and dynamically adjusting the core SRT and the associated SRT to reflect the latest network status and service requirements, so that the entire CDN system can quickly adapt to changes; in addition, the core SRT and the associated SRT not only contain basic service configuration information, but also may involve security-related information such as key pool and content identifier conversion rules, which are crucial for maintaining secure communication between DCDNs, especially when handling sensitive data, timely updating the core SRT and the associated SRT ensures that all participants use the latest and correct security parameters.

[0068] In some embodiments, as Figure 5 As shown, the generation and update process of the core SRT and the associated SRT in the embodiment of the present disclosure includes:

[0069] S502, the DCDN reports the service capability through the content distribution network interconnection protocol.

[0070] S504, after the UCDN receives the service capability of the DCDN, the UCDN updates the corresponding entry of the core SRT.

[0071] S506, the UCDN calculates the service weight of the corresponding entry of the associated SRT of the DCDN

[0072] S508, the UCDN updates the associated SRT of the DCDN.

[0073] In some embodiments, the generation and updating of the core SRT and the associated SRT in the embodiments of the present disclosure are provided by the UCDN interface content provider and determine which DCDN specifically provides the target service, the embodiments of the present disclosure do not change the interface logic of the content distribution network interconnection protocol, and the generation and updating of the associated SRT are determined by the core SRT; the DCDN can directly determine the service redirection corresponding DCDN from the associated SRT table, without the need for further transfer through the UCDN.

[0074] In some embodiments, before sending a target service request to a target downstream content distribution network according to a redirection request, the redirection method of the content distribution network interconnection route in the embodiments of the present disclosure further includes: completing the verification of the downstream content distribution network to be redirected and the target downstream content distribution network by asymmetric key signature. Specifically, the asymmetric key signature uses a pair of keys, a public key and a private key, the issuer uses its private key to sign the data (such as the token in the redirection request), and the receiver uses the public key of the issuer to verify the validity of the signature, ensuring that only entities with the correct private key can generate valid signatures, thereby preventing the redirection request from being forged or tampered with; even if the data transmitted in the network is intercepted, attackers cannot forge a legitimate redirection request because they do not have the corresponding private key; secondly, each DCDN has its own public key and private key pair, and in the redirection process, the DCDN to be redirected uses its private key to sign the token containing key information (such as issuer CDN-ID, target CDN-ID, URL hash value, expiration time, etc.), and the target DCDN can use the public key of the DCDN to be redirected to verify the token, confirming that it indeed comes from the specified DCDN and is not a fake, ensuring the authenticity and integrity of the redirection request; in addition, since each DCDN has an independent key pair and can obtain the public keys of other DCDNs through a public channel, it does not need to rely on a third-party authority for identity verification, and this decentralized trust model allows DCDNs to directly establish a secure connection and complete the necessary verification without the real-time intervention of the UCDN.

[0075] In some embodiments, the embodiments of the present disclosure take the DCDN1 service migration to DCDN2 service as an example, the migration in the embodiments of the present disclosure mainly includes: DCDN1 migration URL and token generation process and DCDN2 migration URL and token verification process, specifically, the DCDN1 migration URL and token generation process includes:

[0076] 1), redirection target CDN selection:

[0077] DCDN1 monitors that the service quality is poor, queries its associated SRT, and selects the DCDN2 with the lowest Cost value as the target CDN through the service routing query.

[0078] 2) Migration URL generation:

[0079] The original service URL is converted into the corresponding URL of DCDN2 through a regular expression of content service identification conversion.

[0080] 3) Token construction:

[0081] The token includes the following parameters: issued CDN-ID, target CDN-ID, hash value of the migration URL, expiration time; token signature: the token is signed using the private key of dCDN1 to generate the final token.

[0082] In some embodiments, the DCDN2 migration URL and token verification process in the embodiments of the present disclosure includes:

[0083] 1) Issuer public key acquisition:

[0084] The request source is obtained from the service request to be DCDN1, and the public key of DCDN1 is extracted from the CDN public key pool associated with the SRT;

[0085] 2) Token verification:

[0086] DCDN2 decrypts the token using the public key of DCDN1, checks the field integrity and timeliness (whether expired);

[0087] 3) Service provision:

[0088] If the token verification is passed, the service is provided.

[0089] In some embodiments, the DCDN1 migration URL and token generation process and the DCDN2 migration URL and token verification process in the embodiments of the present disclosure can completely remove the real-time participation of UCDN in the generation of a secure token process, realize direct cooperation between CDNs through the key information and strategies pre-set by the associated SRT, and realize decentralized trust; the core SRT is still managed and updated by the UCDN, but the strategy data (public key, route) is synchronized to the associated SRT regularly, which can support offline verification and realize dynamic strategy synchronization; in addition, the generation of a secure token process and the whole key verification process do not depend on the online interaction of the UCDN, and the decentralized permission verification is realized.

[0090] In some embodiments of this disclosure, when a DCDN detects insufficient service quality, it selects a target DCDN based on indicators such as the "service weight (Cost value)" in the associated SRT, constructs a redirect URL, and generates a service migration request. More specifically, to ensure compatibility with existing content delivery network interconnection strategies, the UCDN needs to dynamically calculate the associated SRT of each DCDN based on the core SRT data. When calculating the corresponding service weight, it is necessary to first filter DCDNs that meet the content delivery network interconnection strategy, and then calculate the service weight (Cost value) among the eligible DCDNs based on factors such as resource availability. The specific calculation process includes: strategy screening and resource evaluation.

[0091] In some embodiments, the policy screening in this disclosure involves the UCDN verifying each DCDN against the connection policies recorded in the core SRT. DCDNs that do not meet the following conditions are eliminated: Geographic coverage matching: The DCDN's geographic footprint must include the user's location to satisfy the geographical restrictions of content delivery network interconnection. If it does not match, it is eliminated. Protocol support: The DCDN must support the protocols requested by the client (such as HTTP / 2, QUIC). If it does not support them, it is eliminated. Access control policy: The DCDN must comply with the access control rules defined in the core SRT (such as content distribution blacklists and whitelists). If it does not comply, it is eliminated. Only DCDNs that pass the above policy screening can proceed to the subsequent service weight calculation stage.

[0092] In some embodiments of this disclosure, resource evaluation is performed in a DCDN that meets the content delivery network interconnection strategy, and the following resource availability factors are considered to calculate the service weight: Load status: Based on the current load of the DCDN recorded in the core SRT (such as CPU utilization and bandwidth utilization), the lower the load, the smaller the service weight and the higher the priority; Cache hit rate: Reflects the content availability of the DCDN. The higher the cache hit rate, the more readily the content can be provided, and the lower the service weight; Latency performance: Based on the historical average distribution latency of the DCDN recorded in the core SRT, the lower the latency, the smaller the service weight.

[0093] In some embodiments, this disclosure uses policy filtering and resource evaluation to ensure the efficiency and policy compliance of service migration.

[0094] In some embodiments, the downstream content distribution network in the embodiments of the present disclosure only reads the associated shared routing table. Specifically, by limiting the modification authority of the DCDN to the associated SRT, it is ensured that all service configuration information is uniformly maintained and updated by the UCDN, avoiding data inconsistency problems caused by decentralized management or misoperation, and ensuring that the information stored in the associated SRT is always up-to-date and accurate. Secondly, read-only access reduces potential security risks, preventing malicious tampering with routing strategies or other important configurations, and protecting user data and service integrity. In addition, centralized management and updating of the associated SRT by the UCDN reduces the complexity of multi-node synchronization and coordination in a distributed environment, and only the core SRT needs to be maintained, without worrying about whether the local configuration on each DCDN is correct. Not only does this save time and resources, but it also reduces the likelihood of errors and improves operational efficiency.

[0095] In some embodiments, the embodiments of the present disclosure enable DCDNs to directly cooperate through a hierarchical SRT structure and autonomous redirection mechanism, bypassing the UCDN, reducing the number of hops and latency of service migration, and significantly improving the efficiency of content distribution, service efficiency and flexibility. In addition, the decentralized design enhances system flexibility, and DCDNs can quickly respond to sudden service anomalies (such as load surges or node failures) to ensure service continuity. Furthermore, service weight calculation strictly follows content distribution network interconnection strategies (such as geographic restrictions and protocol support), ensuring seamless compatibility with existing content distribution network interconnection architectures, while filtering out unqualified DCDNs to improve the success rate of migration and policy compliance.

[0096] Based on the same inventive concept, the embodiments of the present disclosure also provide a redirection device for content distribution network interconnection routing, as follows. Since the principle of the device embodiments solves the problem similar to the above-mentioned method embodiments, the implementation of the device embodiments can be referred to the implementation of the above-mentioned method embodiments, and the repeated parts will not be described here.

[0097] Figure 6 A schematic diagram of a redirection device for content distribution network interconnection routing in the embodiments of the present disclosure is shown. The device is applied in a content distribution network interconnection system, which includes a plurality of downstream content distribution networks. The device includes:

[0098] The redirection request receiving module 601 is configured to receive a redirection request sent by a downstream content distribution network to be redirected.

[0099] The target service request sending module 602 is configured to send a target service request to a target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides a target service.

[0100] The redirection device for interconnection routing of a content distribution network provided in the embodiments of the present disclosure receives a redirection request sent by a downstream content distribution network to be redirected through a redirection request receiving module; and sends a target service request to a target downstream content distribution network according to the redirection request through a target service request sending module, so that the target downstream content distribution network provides target services. Compared with the service scheduling of a related technical downstream content distribution network, which needs to be uniformly decided by an upstream content distribution network, when a downstream content distribution network node needs to migrate services due to cache invalidation or performance decline, the request must be returned to the upstream content distribution network for reallocation. The embodiments of the present disclosure break through the bottleneck of traditional content distribution network interconnection relying on the upstream content distribution network, and when a certain downstream content distribution network service is abnormal, the user request can be redirected directly without passing through the upstream content distribution network, which greatly improves the migration efficiency and security.

[0101] In some embodiments, the content distribution network interconnection system in the embodiments of the present disclosure includes an upstream content distribution network, and the redirection device for interconnection routing of a content distribution network in the embodiments of the present disclosure further includes: a docking strategy determining module, configured to determine a docking strategy between the upstream content distribution network and a plurality of downstream content distribution networks based on a content distribution network interconnection protocol before receiving a redirection request sent by a downstream content distribution network to be redirected, the content distribution network interconnection protocol being used for the upstream content distribution network to identify and connect to the downstream content distribution network; and a core shared routing table generating module, configured to generate a core shared routing table according to the docking strategy, the core shared routing table being used to store network service configuration information of the upstream content distribution network and the plurality of downstream content distribution networks.

[0102] In some embodiments, the redirection device for interconnection routing of a content distribution network in the embodiments of the present disclosure further includes: an associated shared routing table generating module, configured to generate an associated shared routing table corresponding to the plurality of downstream content distribution networks based on the network service configuration information of the plurality of downstream content distribution networks in the core shared routing table after the core shared routing table is generated, wherein the associated shared routing table is associated with the core shared routing table and is configured to store relevant information generated according to data records in the core shared routing table.

[0103] In some embodiments, the redirection request is generated according to the associated shared routing table corresponding to the downstream content distribution network to be redirected.

[0104] In some embodiments, the redirection device for interconnection routing of a content distribution network in the embodiments of the present disclosure further comprises: a core shared routing table updating module, configured to update the core shared routing table when a change occurs in the downstream content distribution network after the core shared routing table is generated according to the interfacing strategy; and an associated shared routing table updating module, configured to update the associated shared routing table corresponding to the downstream content distribution network according to the network service configuration information of the downstream content distribution network in the updated core shared routing table.

[0105] In some embodiments, the redirection device for interconnection routing of a content distribution network in the embodiments of the present disclosure further comprises: a verification module, configured to control the downstream content distribution network to be redirected and the target downstream content distribution network to complete verification through asymmetric key signature before sending a target service request to the target downstream content distribution network according to the redirection request.

[0106] In some embodiments, the associated shared routing table of the downstream content distribution network in the embodiments of the present disclosure is read-only.

[0107] Based on the same inventive concept, the present disclosure further provides a redirection system for interconnection routing of a content distribution network, as follows. Since the principle of the system embodiments for solving the problem is similar to the above-mentioned method embodiments, the implementation of the system embodiments can be referred to the implementation of the above-mentioned method embodiments, and the repeated parts will not be described here.

[0108] A redirection system for interconnection routing of a content distribution network in the embodiments of the present disclosure is shown in the schematic diagram, which comprises:

[0109] A downstream content distribution network, configured to send a redirection request and receive a target service request;

[0110] A client, configured to receive the redirection request sent by the downstream content distribution network to be redirected, and send a target service request to the target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides a target service.

[0111] In some embodiments, as shown in Figure 7 The embodiments of the present disclosure set a core SRT on the UCDN, and set an associated SRT on each DCDN. The DCDN can directly redirect user requests to other DCDNs through the associated SRT. The SRT does not change the relationship between the UCDN and the DCDN in the existing content distribution network interconnection, but can skip the UCDN to directly redirect user requests, greatly improving the migration efficiency and security.

[0112] Those skilled in the art can understand that the various aspects of the present disclosure can be implemented as a system, a method or a program product. Therefore, the various aspects of the present disclosure can be embodied as a whole hardware implementation, a whole software implementation (including firmware, microcode, etc.), or a combination of hardware and software aspects, which can be collectively referred to as "circuitry", "module" or "system" here.

[0113] Based on the same inventive concept, the electronic device in the embodiments of the present disclosure also provides a kind of electronic device, comprising: processor;And memory, for storing the executable instruction of processor;Wherein, processor is configured to execute the redirection method of the content distribution network interconnection route of any one of the above by executing executable instruction.It is similar to the principle that the problem is solved by the above method embodiment, so the implementation of the electronic device embodiment can be referred to the implementation of the above method embodiment, and the repeated part will not be described here.

[0114] The electronic device 800 according to this embodiment of the present disclosure will be described below with reference to Figure 8 Figure 8 The display electronic device 800 is only an example, and should not bring any limitation to the function and use range of the embodiments of the present disclosure.

[0115] As Figure 8 The electronic device 800 is shown in the form of a general computing device. The components of the electronic device 800 can include, but are not limited to, the above-mentioned at least one processing unit 801, the above-mentioned at least one storage unit 802, and the bus 803 connecting different system components, including the storage unit 802 and the processing unit 801.

[0116] The storage unit stores program code, which can be executed by the processing unit 801, so that the processing unit 801 executes the steps according to various exemplary embodiments of the present disclosure described in the above "Exemplary Method" section of the present specification.

[0117] In some embodiments, when the electronic device is used to control, for example, the redirection method of the content distribution network interconnection route of the present disclosure, the processing unit 801 can execute the following steps of the above method embodiment:

[0118] Receiving a redirection request sent by a downstream content distribution network to be redirected; according to the redirection request, a target service request is sent to a target downstream content distribution network, so that the target downstream content distribution network provides target service.

[0119] The storage unit 802 can include a readable medium in the form of a volatile storage unit, such as a random access memory (RAM) 8021 and / or a cache memory unit 8022, and can further include a read-only memory (ROM) 8023.​

[0120] The storage unit 802 also includes a number of program modules 8025 that are stored in the memory 8024, including but not limited to an operating system, one or more application programs, other program modules, and program data, each of which performs one or more tasks that facilitate the implementation of the example embodiments.

[0121] The bus 803 can represent one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, a graphics acceleration bus, a processor or local bus using any of a variety of bus architectures, and so on.

[0122] The electronic device 800 can also communicate with one or more external devices 804 such as a keyboard or pointing device, a Bluetooth device, etc.; other devices that enable a user to interact with the electronic device 800; and / or one or more devices that enable the electronic device 800 to communicate with one or more other computing devices. Such communication can be facilitated by an Input / Output (I / O) interface 805. Still yet, the electronic device 800 can communicate with one or more networks, such as a local area network (LAN), a wide area network (WAN), and / or the Internet, through a network adapter 806. As depicted, the network adapter 806 can communicate with the other components of the electronic device 800 through the bus 803. It should be appreciated that although the network adapter 806 is depicted as a single component, the network adapter 806 can comprise two or more components that operate together to facilitate communications with one or more networks. It should be appreciated that the bus 803 can be implemented using any type of bus structures, including a memory bus or memory controller, a peripheral bus, a graphics acceleration bus, a processor or local bus using any of a variety of bus architectures.

[0123] Those skilled in the art will readily understand that the example embodiments described herein can be implemented by software and / or by hardware coupled with software, as described above. Thus, the technical solutions according to the embodiments of the present disclosure can be embodied in the form of a software product. The software product can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash disk, a mobile hard disk, or the like) or a network, and includes a number of instructions that cause a computing device (which can be a personal computer, a server, a terminal device, or a network device, etc.) to perform the methods according to the embodiments of the present disclosure.

[0124] Based on the same inventive concept, the disclosure further provides a computer readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the redirection method of the content distribution network interconnection routing of any of the above. Since the principle of solving problems of the computer readable storage medium embodiment is similar to that of the above method embodiment, the implementation of the computer readable storage medium embodiment can be referred to the implementation of the above method embodiment, and the repeated parts will not be described here.

[0125] More specific examples of the computer readable storage medium in the present disclosure can include, but are not limited to, an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0126] In the present disclosure, the computer readable storage medium can include a data signal carried in the baseband or as part of a carrier wave propagating through the program code readable. Such a propagating data signal can take various forms, including but not limited to an electromagnetic signal, an optical signal, or any suitable combination of the foregoing. The readable signal medium can also be any readable medium other than the readable storage medium, which can send, propagate or transmit programs for use by or in connection with instruction execution systems, apparatuses or devices.

[0127] Optionally, the program code contained on the computer readable storage medium can be transmitted by any suitable medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination of the foregoing.

[0128] In specific implementation, the program code for executing the operations of the present disclosure can be written in any combination of one or more programming languages, including object-oriented programming languages such as Java, C++, etc., and conventional procedural programming languages such as "C" language or similar programming languages. The program code can be executed entirely on the user computing device, partially on the user device, as an independent software package, partially on the user computing device and partially on the remote computing device, or entirely on the remote computing device or server. In the case involving remote computing device, the remote computing device can be connected to the user computing device through any kind of network, including local area network (LAN) or wide area network (WAN), or can be connected to external computing device (for example, using Internet service provider to connect through the Internet).

[0129] Based on the same inventive concept, the embodiments of the present disclosure further provide a computer program product, comprising a computer program product, comprising: a computer program or instructions, which, when executed by a processor, implements the redirection method of the content distribution network interconnection route according to any one of the above method embodiments. Since the problem solving principle of the computer program product embodiment is similar to the above method embodiments, the implementation of the computer program product embodiment can be referred to the implementation of the above method embodiments, and the repeated parts will not be described herein.

[0130] It should be noted that although several modules or units of the device for action execution are mentioned in the above detailed description, such division is not mandatory. Indeed, according to embodiments of the present disclosure, features and functionalities of two or more modules or units described above can be embodied in one module or unit. Conversely, features and functionalities of one module or unit described above can be further divided into several modules or units.

[0131] Furthermore, although the various steps of the methods of the present disclosure are described in a particular order in the figures, this is not required or implied in any way as to the order of the steps or that all of the steps be performed to achieve the desired result. Additionally or alternatively, certain steps can be omitted, several steps can be combined into one step, one step can be broken into several steps, and / or the like.

[0132] From the above description of the embodiments, those skilled in the art will readily appreciate that the example embodiments described herein can be implemented by software and / or by hardware. Embodiments according to the present disclosure can therefore be realized in a software selective form, which can be stored in a non-volatile storage medium, such as a CD-ROM, a USB flash drive, a mobile hard disk, or a network, and can include a number of instructions for making a computing device (which can be a personal computer, a server, a mobile terminal, or a network device, etc.) execute the methods according to the embodiments of the present disclosure.

[0133] Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the features of the present disclosure disclosed herein. It is intended that the present disclosure cover any and all variations of the present disclosure including those variations that can be incorporated into the above detailed description and making use of the general principles of the present disclosure. It is intended that the present disclosure include all such as fall within the scope of the appended claims and their equivalents. The specification and examples given herein are to be considered exemplary only, and the true scope and spirit of the disclosure being indicated by the appended claims.

Claims

1. A method for redirecting interconnection routes of a content distribution network, characterized in that, The method is applied to a content distribution network interconnection system, the content distribution network interconnection system comprising an upstream content distribution network and a plurality of downstream content distribution networks, and the method comprises: determining, based on a content distribution network interconnection protocol, a docking strategy between the upstream content distribution network and the plurality of downstream content distribution networks, the content distribution network interconnection protocol being used to enable the upstream content distribution network to identify and connect to the downstream content distribution networks; and generating, according to the docking strategy, a core shared routing table, the core shared routing table being used to store network service configuration information of the upstream content distribution network and the plurality of downstream content distribution networks; generating, based on the network service configuration information of the plurality of downstream content distribution networks in the core shared routing table, an associated shared routing table corresponding to each of the plurality of downstream content distribution networks, wherein the associated shared routing table is associated with the core shared routing table and is configured to store relevant information generated according to data records in the core shared routing table; receiving a redirection request sent by a downstream content distribution network to be redirected, the redirection request being generated according to the associated shared routing table corresponding to the downstream content distribution network to be redirected; sending a target service request to a target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides target services.

2. The redirection method of interconnecting routes of a content distribution network according to claim 1, characterized in that, After the core shared routing table is generated according to the docking strategy, the method further comprises: updating the core shared routing table when the downstream content distribution network changes; updating the associated shared routing table corresponding to the downstream content distribution network according to the network service configuration information of the downstream content distribution network in the updated core shared routing table.

3. The redirection method of interconnecting routes of a content distribution network according to claim 1, characterized in that, Before the target service request is sent to the target downstream content distribution network according to the redirection request, the method further comprises: controlling the downstream content distribution network to be redirected and the target downstream content distribution network to complete authentication through asymmetric key signature.

4. The method of redirecting inter-networking routes of a content distribution network of claim 1, wherein, The downstream content distribution network only reads the associated shared routing table.

5. A redirection apparatus of interconnection routing of a content distribution network, characterized by, The device is applied to a content distribution network interconnection system, the content distribution network interconnection system comprising an upstream content distribution network and a plurality of downstream content distribution networks, and the device comprises: a docking strategy determination module configured to determine, based on a content distribution network interconnection protocol, a docking strategy between the upstream content distribution network and the plurality of downstream content distribution networks, the content distribution network interconnection protocol being used to enable the upstream content distribution network to identify and connect to the downstream content distribution networks; a core shared routing table generation module configured to generate, according to the docking strategy, a core shared routing table, the core shared routing table being used to store network service configuration information of the upstream content distribution network and the plurality of downstream content distribution networks; The association shared routing table generation module is configured to generate an association shared routing table corresponding to each of the plurality of downstream content distribution networks based on the network service configuration information of the plurality of downstream content distribution networks in the core shared routing table, wherein the association shared routing table is associated with the core shared routing table and is configured to store relevant information generated according to the data records in the core shared routing table; The redirection request receiving module is configured to receive a redirection request sent by a downstream content distribution network to be redirected, wherein the redirection request is generated according to the association shared routing table corresponding to the downstream content distribution network to be redirected; The target service request sending module is configured to send a target service request to a target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides a target service.

6. A redirection system for interconnecting routes of a content distribution network, characterized in that Comprise: An upstream content distribution network; A downstream content distribution network configured to send a redirection request and receive a target service request; A client configured to determine an interfacing strategy between the upstream content distribution network and a plurality of downstream content distribution networks based on a content distribution network interconnection protocol, wherein the content distribution network interconnection protocol is used to enable the upstream content distribution network to identify and connect to the downstream content distribution networks; generate a core shared routing table according to the interfacing strategy, wherein the core shared routing table is used to store network service configuration information of the upstream content distribution network and the plurality of downstream content distribution networks; generate an association shared routing table corresponding to each of the plurality of downstream content distribution networks based on the network service configuration information of the plurality of downstream content distribution networks in the core shared routing table, wherein the association shared routing table is associated with the core shared routing table and is configured to store relevant information generated according to the data records in the core shared routing table; receive a redirection request sent by a downstream content distribution network to be redirected, wherein the redirection request is generated according to the association shared routing table corresponding to the downstream content distribution network to be redirected; and send a target service request to a target downstream content distribution network according to the redirection request, so that the target downstream content distribution network provides a target service.

7. An electronic device, comprising: Comprise: A processor; And A memory configured to store executable instructions of the processor; Wherein the processor is configured to execute the executable instructions to perform the content distribution network interconnection routing redirection method of any one of claims 1-4.

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the content distribution network interconnection routing redirection method of any one of claims 1-4.

9. A computer program product, comprising: Computer program or instructions, characterized in that the computer program or instructions are executed by the processor to implement the content distribution network interconnection routing redirection method of any one of claims 1-4.

Images