Electrical computers and digital processing systems: multicomput – Computer-to-computer protocol implementing – Computer-to-computer data transfer regulating
Reexamination Certificate
2000-05-10
2004-05-25
Najjar, Saleh (Department: 2157)
Electrical computers and digital processing systems: multicomput
Computer-to-computer protocol implementing
Computer-to-computer data transfer regulating
C709S225000, C709S226000, C709S227000, C709S229000, C709S238000
Reexamination Certificate
active
06742044
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to data networks, and more specifically to a technique for distributed load balancing of network traffic across a data network.
2. Background
Content providers on the World Wide Web are willing to pay a great deal of money to guarantee that their content is delivered quickly and accurately to any given client. Accordingly, a great deal of research has been conducted to address the problem of speeding up HTTP transactions conducted between a client and a server, particularly in situations where there is a relatively large propagation delay between the client and the server.
Although the speed of data transmission across the Internet is continuing to increase, the propagation delay associated with the speed of an electrical signal traveling through a wire or fiberoptic cable (i.e. the speed of light) cannot be reduced. Such delays are becoming a significant factor in the overall propagation delay between the server and client. In order to reduce the overall propagation delay between a given server and a given client, conventional techniques have resorted to replicating the server system, and placing multiple copies of the replicated server system at locations as near as possible to the client.
Thus, for example, a common technique used by content providers is to store content from the host server in co-location spaces that are geographically distributed over a wide area. The co-location spaces form an overlay network that is more costly and less flexible, but provide better service than the traditional Internet. Typically the ISPs which manage the co-location spaces charge the content provider for each megabyte stored in the co-location space. The co-location spaces may be implemented as proxy servers, which pull specific data from the host server in response to specific client requests, or may be implemented as fully replicated servers which include all the information of the host server.
Although the use of co-location spaces will help reduce the overall propagation delay between a server and client, another issue which arises relates to the problem of determining how an arbitrary client is redirected to the nearest replica or proxy server, particularly where it is not known ahead of time which clients will be asking for information and where the clients are located. Some conventional techniques have been implemented to address this problem, but typically require the use of a gateway router.
An alternate technique for predicting, for a given client, the nearest replica or proxy server to that client has been developed by Akamai Technologies, Inc. (of Cambridge, Mass.). The proprietary Akamai routing technique involves constructing a network map of the Internet topology. The network map information is stored in a central network operating center or NOC which is located on a specific Akamai server. When a client attempts to access a content provider's site which is part of the Akamai overlay network of co-location servers, the client will initiate a DNS resolution request, which is resolved by the NOC server. The NOC dynamically resolves the requested domain name to a co-location server address that is nearest topologically to the client, using information from the network map.
However, in order for Akamai's routing technique to be successfully implemented, the network topology map must be continually updated and maintained. According to at least one school of thought, however, maintaining an accurate Internet topology may be nearly impossible since the Internet topology is dynamically changing and is exponentially growing in size and complexity each day.
More importantly, the Akaimi routing technique is limited only to resolving DNS queries implemented using DNS protocol. Currently, the Akaimi technique for re-routing clients to a nearest proxy server is not extendable to other protocols such as, for example, TCP. Thus, for example, when a client obtains a particular IP address of a server, and subsequently attempts to initiate a TCP connection with that server, the Akaimi technique can not be used to re-route the client to establish a TCP connection with a topologically closer proxy server.
Accordingly, in light of the foregoing, there exists a continual need to develop alternative solutions for providing fast and efficient routing and load balancing of web traffic across data networks.
SUMMARY OF THE INVENTION
According to specific embodiments of the present invention, a technique is provided for routing a client device to access a specific client server in a data network. The data network may include at least one host server, a sub-network of client servers associated with the at least one host server, and at least one client system. According to one embodiment, the data network corresponds to the Internet, wherein the at least one host server corresponds to the host server of a content provider, the sub-network of client servers corresponds to an overlay network of proxy or replica servers.
The technique of the present invention provides a solution to the problem of routing or redirecting a given client to a replica or proxy server which has a relatively shortest propagation delay to the client. According to the technique of the present invention, a network device referred to as an intercept server sits in front of a host server, and intercepts packets routed to the host server. When desired, packets which are intercepted by the intercept server are replicated, encapsulated and tunneled to selected client servers in the overlay network. The tunneled packets are received and processed by each of the selected client servers, whereupon each of the selected client servers generates a respective spoofed response to the source device identified in the header of the originally intercepted packet. Further, according to the technique of the present invention, each of the selected client servers transmits its respective spoofed response to the identified source device at substantially the same time. The client server associated with the spoofed response which is first received at the identified source device is considered to have the relatively shortest propagation delay to the identified source device, and is identified as the successful client server. Thereafter, the source device will be directed or redirected to communicate directly with the successful client server when subsequently attempting to access information from the host server.
Other embodiments of the present invention are directed to a method and computer program product for routing a client device to access a specific server in a data network. The data network includes a sub-network of client servers which are configured to include information corresponding to information stored on at least one host server. A first packet is received from a source device. Information relating to the first packet is then forwarded to a first portion of client servers in the sub-network. Each of the first portion of client servers is then caused to transmit, at substantially the same time, a respective spoofed response to the source device. Each spoofed response may be generated using information from the first packet. According to a specific embodiment, a successful client server may then be identified as being associated with generating a particular spoofed response that was first received at the source device. An ID of the source device may then be binded with an ID of the successful client server in order to cause subsequent requests from the source device to access information from the host server to be routed to the successful client server device for processing. Further, according to a specific implementation, the first packet received from the source device may correspond to a SYN segment of a TCP protocol for communicating with the host server. Additionally, each spoofed response may comprise a SYN, ACK segment which includes a unique sequence number relating to an identity of the client server which generated the spoofed r
Aviani James
Baker Frederick
Gnagy Matthew Richard
Mueller, II Kenneth E.
Swanson David Eric
Beyer Weaver & Thomas LLP.
Cisco Technology Inc.
Najjar Saleh
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