Electrical computers and digital processing systems: multicomput – Computer-to-computer data modifying – Compressing/decompressing
Reexamination Certificate
2000-12-20
2003-09-02
Lim, Krisna (Department: 2153)
Electrical computers and digital processing systems: multicomput
Computer-to-computer data modifying
Compressing/decompressing
C709S217000, C709S218000
Reexamination Certificate
active
06615275
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to data access in a file/object oriented network system. More particularly, the present invention is directed to a client-agent-server utility which increases the speed in which data in the form of files, objects and directories are accessed across slow link communications via remote node caching and provides verification, selective object compression, processor capacity monitoring in order to disable process intensive components such as compression, selective prefetch and concatenation of fresh objects and indicators of cache correctness.
2. Related Art
There exist operating systems which are equipped to handle caching and verifying as well as compression of data. Traditionally, in a remote client's caching system, optimization in retrieving data is limited to prefetching. In other words an application program in a remote client requests from a file server transmission of a predetermined number of bytes of information (e.g., x bytes) and the operating system on the client prefetches the requested data plus another number of bytes of information (e.g., x+y bytes). Thus, when the application requests the bytes, it already exists in its readily accessible memory (cache).
In addition, there also exist problems with verification of directories in existing systems. It has been found, for example, that two remote clients concurrently accessing data and attempting to verify a directory will not necessarily obtain the same data due to the fact that the data from the file server computer will not necessarily send out the data in the same order to each of the remote clients. Thus, there is no clear indication whether the directory data is current.
In a desktop caching system, a high speed memory is used to cache data that is stored on a hard disk. While a desk-top cache program, such as Microsoft's SmartDrive, is a useful tool to increase performance from the random access memory (RAM), this type of caching technique is not applicable to remote environments because of its inability to correctly handle multiple remote clients accessing the same data files concurrently, i.e., it is likely to corrupt the data.
File servers have employed caching techniques which parallel techniques of the desktop. Here, the file server deviates in protecting against multiple common data user access by implementing or providing a file locking service to clients.
Many object oriented network systems include web browsers which commonly manifest themselves on an object retrieval side of the remote client, such as Netscape's Navigator or as Lotus Notes clients, and include web servers which commonly manifest themselves on the object server side, such as Notes servers, are equipped to maintain a cache of objects to avoid unnecessary retrieval of objects from a network of object providers. Cache correctness is determined through a given technique.
Many existing object oriented network systems employ inefficient data communication protocols to transfer object updates to replicas of an object collection. For example, during the replication process that takes place between a Lotus Notes™ client and server each object update is requested separately which results in extra packet exchanges and inefficiency.
Existing object oriented network systems often employ a client-agent-server utility (the “agent”) to further reduce unnecessary retrieval of objects from a network of object provider. These agents are often termed as “proxy servers” since they retrieve objects from a network of object providers on behalf of a set of clients. In this situation, the agent maintains a cache of objects and monitors and responds to object retrieval requests from one or more remote clients. The agent may fulfill the request which emanates from a client by retrieving the object from its cache rather than forwarding the request to the network of object providers.
As shown in
FIG. 1
, the related art includes a remote client computer having an operating system (OS) with a file system interface (FSI). Operatively connected to the FSI is a local file system (LFS) which in turn is operatively connected to a RAM based disk cacher (RBDC), disk driver (DD) and permanent storage disk (PSD). The PSD may include object retrieval application cache (ORAC) and object collection Replicas (OCRs).
Object retrieval applications (ORAs) exist in the remote client which have the ability to retrieve objects and to store OCRs into the PSD via the LFS via the FSI. These OCRs are retrieved through an Object Retrival/Storage interface (ORSI) which employs an Object Retriever (OR).
Operatively connected to the FSI is a network file redirector (NFR) with prefetch capability, and a network transport layer (NTL) connected to a WAN driver. Aside from the OS, there exist application programs (AP) which employs the OS via the FSI. A communication server (CS) connects to the remote client computer and includes a WAN. driver, routing layer and LAN driver. The CS connects through a LAN link to a file server computer.
The file/object server computer has an OS. The file/object server computer OS includes an NTL connected to a LAN driver and an FSI connected to LFS which in turn is connected to an RBDC, a DD and a PSD. Aside from the OS, there exists a file/object server application which employs the OS via the FSI.
An object proxy server (OPS) may also exist operatively connected to the communication server and the file object server. The OPS includes and ORSI, and OR, NTL, LAN driver, FSI, RBDC and DD as shown in FIG.
1
. The OPS maintains an object cache for the purpose of maintaining an object cache on PSD via an FSI. The OPS retrieves objects via an ORSI which is operatively connected to an Object Retriever (OR).
A further problem associated with these prior systems is their inability to provide a remote client user with greater speed of access to object collection updates because of inefficient or “chatty” data communication protocols. This chattiness usually manifests itself in extra packet exchanges to accomplish the communication of the object collection updates by requesting each object update individually. In a satellite based communication link, latency is an important factor where the send/receive acknowledgment cycle of even the smallest data unit can take several seconds to accomplish.
The problem associated with these prior systems is their inability to provide a remote client user with greater speed of access to file/object server data and/or file/object server directories. This is especially so because of the type of link in which the remote client may be accessing the data through, such as a modem phone link. In the context of the present invention, “remote client” is defined as a user, accessing data over a relatively slow link, such as a modem phone link. A typical modem phone link provides a transfer rate of about 28.8 kilobits of information per second. This is contrasted with a link in a LAN connection which can transfer at about 10 Megabits per second. These remote clients are thus greatly limited in speed of access.
As described in a parent application, an incoherent data with the that of the file/object server, employs a compression mechanism for transmitting the “flesh” block of data to the remote client. This provided performance gains via using a method of concatenating the object updates into a contiguous stream of data and intelligently applying data compression to the portions of the data stream which would benefit from the compression. The determination of when to apply data compression is based on weighing the benefits of the data reduction that would be achieved and the speed of the communication link versus the time it would take to perform the data compression, IE the slower the communication link and the more data reduction that would be achieved, the more likely that data compression will be applied to the data stream.
While these improvements have aided the speed of access in data over a network, there remains a need to improve the s
Hertzog Scott
Morris Brian C.
Penner Jon J.
Yohe Thomas Patrick
Graham R. William
Lim Krisna
Stampede Technologies, Inc.
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