This invention relates to methods for controlling and monitoring access to network servers. In particular, the process described in the invention includes client-server sessions over the Internet. In this environment, when the user attempts to access an access-controlled file, the server subjects the request to a secondary server which determines whether the client has an authorization or valid account. Upon such verification, the user is provided with a session identification which allows the user to access to the requested file as well as any other files within the present protection domain.

Internet server access control and monitoring systems

This paper discusses the design and performance of a hierarchical proxy-cache designed to make Internet information systems scale better. The design was motivated by our earlier trace-driven simulation study of Internet traffic. We challenge the conventional wisdom that the benefits of hierarchical file caching do not merit the costs, and believe the issue merits reconsideration in the Internet environment.

The cache implementation supports a highly concurrent stream of requests. We present performance measurements that show that our cache outperforms other popular Internet cache implementations by an order of magnitude under concurrent load. These measurements indicate that hierarchy does not measurably increase access latency. Our software can also be configured as a Web-server accelerator; we present data that our httpd-accelerator is ten times faster than Netscape's Netsite and NCSA 1.4 servers.

Finally, we relate our experience fitting the cache into the increasingly complex and operational world of Internet information systems, including issues related to security, transparency to cache-unaware clients, and the role of file systems in support of ubiquitous wide-area information systems.

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A hierarchical internet object cache

A universal electronic resource denotation, request and delivery system allows a user to locate information on a distributed computer system or network such as the Internet by knowing or guessing a short mnemonic alias of an electronic resource without the user having to know the physical or other location denotation such as the universal resource locator (URL) of the desired resource. The system hardware includes a client computer, a local server, a central registry server, a value added server, and a root server. The universal electronic resource denotation, request and delivery system supports a personal aliasing (nicknaming) feature, a universal resource accessing feature for finding location information such as URLs relating to a query term, a "see also" feature for including information about related documents or resources within the record of a resource, a feature for updating local servers and client machines by periodically deleting those records which have changed, a "try again" and "mirroring" feature for aiding a user in obtaining the resource under adverse hardware or software conditions, and an authentication and administration feature that allows a user to administer the aliases and related data which pertain to his/her resources.

Universal electronic resource denotation, request and delivery system

Zebra is a network file system that increases throughput by striping the file data across multiple servers. Rather than striping each file separately, Zebra forms all the new data from each client into a single stream, which it then stripes using an approach similar to a log-structured file system. This provides high performance for writes of small files as well as for reads and writes of large files. Zebra also writes parity information in each stripe in the style of RAID disk arrays; this increases storage costs slightly, but allows the system to continue operation while a single storage server is unavailable. A prototype implementation of Zebra, built in the Sprite operating system, provides 4–5 times the throughput of the standard Sprite file system or NFS for large files and a 15–300% improvement for writing small files.

Zebra striped network file system

In a distributed environment several data processing systems are interconnected across a network system. A distributed services program installed on the systems in the network allows the processors to access data files distributed across the various nodes of the network without regard to the location of the data file in the network. The processing system accessing file, referred to as the client processing system, utilizes a client cache within its operating system to store the data file. Utilizing the client cache minimizes the number of reads and writes that must go over the network to the server processing system where the file physically resides. The system and method of this invention prevents a process in the client processing system from accessing data in the client cache that has been modified at another node in the network. The blocks of data in the client cache are tested for validity in the client processing system by using modification times as measured by the server processing system. If the cache data blocks are determined to be valid, the data blocks are determined to be invalid, the data blocks are discarded, and the file is accessed from the server processing system.

A system and method for using cached data at a local node after re-opening a file at a remote node in a distributed networking environment

m tively slow and inexpensive source of information and a uch faster consumer of that information. The cache c capacity is relatively small and expensive, but quickly ac essible. The goal is for the cache behavior to dominate e c performance but the large storage facility to dominat osts, thus giving the illusion of a large, fast, inexpensive a s storage system. Successful operation depends both on ubstantial level of locality being exhibited by the consut mer, and careful strategies being chosen for cache opera ion disciplines for replacement of contents, update syn-

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Robert Lindell

Papers

Name Service Locality and Cache Design in a Distributed Operating System.