Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-09-23
2003-03-18
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S465000
Reexamination Certificate
active
06535509
ABSTRACT:
BACKGROUND OF THE INVENTION
Computer network industry analysts and experts agree that data traffic over large networks and, in particular, the Internet, is presently so heavy that the very nature in the way in which it is possible to use such networks may require fundamental changes. These difficulties are no doubt the result of continued exponential increases in the number of users, as well as in the number of large document files that these users expect to transfer. As a result of this unprecedented demand in the need for network bandwidth, Internet Service Providers (ISPs), backbone providers, and other carriers that provide the physical connections which implement the Internet face correspondingly unprecedented difficulty. This difficulty exists at all levels of network hierarchy, including the points of presence (POPs), central access nodes, network access points, and exchange points, such as metropolitan area exchanges.
To understand what has led to this situation, consider how the Internet is typically used. The most popular user environment, the World Wide Web, provides access to content on an equal basis through the use of the client and server communication model. In this structure, certain computers known as “servers” are used to store and provide information. Other computers in the network known as “clients” allow the users to view documents through the use of a computer program known as a browser that requests a copy of the document be sent from host servers down to the client. Documents are typically requested by the client browser program specifying an address which identifies the host server which stores the document. After the browser specifies a document such as by its so-called Internet Protocol (IP) address, the request is sent to a naming service in order to obtain instructions for how to establish a connection with the host server associated with the IP address. Once this connection is established, the server retrieves the document from its local disk and transmits the document over network to the client. The connection between the client and host server is then terminated.
A common solution for the present bottlenecks within the Internet is to deploy higher speed hardware. Such solutions include the deployment of digital subscriber line (xDSL) cable modem technology to speed up the physical layer communication paths between the end users and points of presence. Gigabit speed routers and optical fiber backbones are also being proposed to alleviate congestion within the network itself. At the server site, server clusters and load balancers are being deployed to assist with the dispatching of Web pages more efficiently.
While all of these solutions provide some expediency, each addresses only part of the problem and none provides an ultimate solution to the problem; the path between the client and server is only as fast or as slow as the slowest physical link.
As it turns out, much of the traffic on the Internet is redundant in the sense that different users request the same documents from the same servers over and over again. Therefore, it is becoming increasingly apparent that certain techniques, such as distributed document caching, may be deployed to reduce the demand for access to both the servers and to the network routing infrastructure. Document caching provides a way to intercept client requests for the same document with the cache serving copies of the original document to multiple client locations.
With a cache, the process for providing document files to the client computers changes from the normal process. In particular, when the client requests the connection, say to a given server, the intermediate cache server may instead be requested to obtain the document. While the document is being transmitted down to the client computer, a copy is stored at the intermediate cache server. Therefore, when another client computer connected to the same network path requests the same content as the first user, rather than requiring the request to travel all the way back to the host server, the request may be served from the local cache server.
However, cache techniques are typically sub-optimal in one way or another. For example, most Web browser programs have a built-in cache that keeps copies of recently viewed content within the client computer itself. If the same content is requested again, the browser simply retrieves it from local storage instead of going out to the network. However, when a browser cache services only one end user, content often expires before it can be reused.
A browser-redirected cache server may also be deployed to service multiple end users. Such a cache server is a separate computer that sits inside a gateway or other point of presence. End users configure their Web browsers to redirect all HTTP traffic to the cache server instead of the locations implied by the Uniform Resource Locators (URLs). The cache server then returns the requested Web page if it has a copy. Otherwise, it forwards the request to the originally specified server and saves a copy as the response flows back. Such a cache server therefore acts as a proxy, receiving all requests and examining them to determine if it can fulfill them locally.
However, even when using proxy servers, it is typically necessary to configure the client browser, proxy server, routers, or other network infrastructure equipment in order to cause the request messages to be redirected to the proxy server. This provides some configuration management difficulties in that reconfiguration of browsers typically requires administrative overhead on the part of the humans who manage the networks.
To improve the odds of locating desired content without having to traverse the entire Internet, local points of presence can be supported by additional caches placed deeper into the network, such as at peering centers. If a primary cache cannot satisfy a request, it queries a secondary cache which in turn may query a tierciery cache, and so forth. If none of the caches in the hierarchy has the desired content, the primary cache ultimately ends up forwarding the document request to the originally requested host.
These caching schemes also fall short in some way. Forced redirection of HTTP traffic turns such cache servers into single points of failure. If a cache server overloads or malfunctions, access to the network is blocked. Recovery is especially awkward with browser redirected caching since every end user's Web browser then has an explicit point to the broken server.
Forced redirection can also have a negative effect on network performance. Even if a browser is topologically closer to the real content server than to a cache server, all HTTP requests detour through the cache and any Web object not in the cache passes through the nearby router or switched twice—one when it travels from the originating server to the cache, and again as the cache forwards it back to the browser and furthermore passing messages from primary to secondary caches and back again at its noticeable latency and ultimately limits the scope of caching in larger networks.
Therefore, there is presently much controversy over the deployment of network caches for several reasons. Cache servers are, in particular, notoriously difficult to optimize. In certain configurations, they will quickly become overloaded in that the number of connections that they are expected to maintain with the user locations is more than the processing power can handle. Time spent determining whether to accept connections, cache documents, and/or refuse connections therefore overloads the cache server, which in turn reduces its performance on an exponential basis. In other situations, the cache servers are underloaded and not enough traffic is routed to them. They therefore represent a large investment of resources not providing optimum utilization and which are in effect underloaded.
SUMMARY OF THE INVENTION
The present invention involves tagging messages received at a network traffic interceptor to reduce redundant processing of messages. Received messa
Infolibria, Inc.
Pham Brenda
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