Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
2000-04-28
2004-04-20
Vu, Kim (Department: 2172)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C707S793000, C707S793000
Reexamination Certificate
active
06725218
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a computerized database system and method, and more specifically, to a distributed computerized database system and method. As used herein, a database “data record” comprises objects and other data items in a distributed computer database that may be accessed and/or modified by a database management or client process. Also as used herein, the “modification” of such a data record may comprise the creation of the data record.
2. Brief Description of Related Prior Art
Data communication in a computer network involves data exchange between two or more entities interconnected by communication links. These entities are typically software program processes executing on computer nodes, such as endstations and intermediate stations. Examples of an intermediate station may be a router or switch which interconnects the communication links and subnetworks to enable transmission of data between the endstations. A local area network (LAN) is an example of a subnetwork that provides relatively short distance communication among the interconnected stations, whereas a wide area network enables long distance communication over links provided by public or private telecommunications facilities.
Communication software executing on the endstations correlate and manage data communication with other endstations. The stations typically communicate by exchanging discrete packets or frames of data according to predefined protocols. In this context, a protocol consists of a set of rules defining how the stations interact with each other. In addition, network routing software executing on the routers allow expansion of communication to other endstations. Collectively, these hardware and software components comprise a communications network and their interconnections are defined by an underlying architecture.
Modern communications network architectures are typically organized as a series of hardware and software levels or “layers” within each station. These layers interact to format data for transfer between, e.g., a source station and a destination station communicating over the network. Predetermined services are performed on the data as it passes through each layer and the layers communicate with each other by means of the predefined protocols. The lower layers of these architectures are generally standardized and are typically implemented in the form of software running on the stations attached to the network. In one example of such a communications architecture there are five layers which are termed, in ascending interfacing order, physical interface, data link, network, transport and application layers. These layers are arranged to form a protocol stack in each communicating station of the network.
FIG. 1
illustrates a schematic block diagram of prior art protocol stacks
125
and
175
used to transmit data between a source station
110
and a destination station
150
, respectively, of a network
100
. As can be seen, the stacks
125
and
175
are physically connected through a communications medium
180
at the interface layers
120
and
160
. For ease of description, the protocol stack
125
will be described.
In general, the lower layers of the communications stack provide inter networking services and the upper layers, which are the users of these services, collectively provide common network application services. The application layer
112
provides services suitable for the different types of applications using the network, while the lower interface layer
120
accepts industry standards defining a flexible network architecture oriented to the implementation of LANs.
Specifically, the interface layer
120
comprises the physical interface layer
126
, which is concerned with the actual transmission of signals across the physical communications medium and defines the types of cabling, plugs and connectors used in connection with the channel or medium. The data link layer (i.e., “layer 2”)
121
is responsible for transmission of data from one station to another and may be further divided into two sublayers: Logical Link Control (LLC
122
) and Medium Access Control (MAC
124
).
The MAC sublayer
124
is primarily concerned with controlling access to the transmission medium in an orderly manner and, to that end, defines procedures by which the stations must abide in order to share the medium. In order for multiple stations to share the same medium and still uniquely identify each other, the MAC sublayer defines a hardware or data link address called a MAC address. This MAC address is unique for each station interfacing to a LAN. The LLC sublayer
122
manages communications between devices over a single link of the network.
The network layer
116
(i.e., “layer 3”) provides network routing and that relies on transport protocols for end-to-end reliability. An example of a network layer protocol is the Internet Protocol (“IP”). An example of such a transport protocol is the Transmission Control Protocol (TCP) contained within the transport layer
114
. The term TCP/IP is commonly used to refer to the Internet architecture.
Data transmission over the network
100
therefore consists of generating data in, e.g., sending process
104
executing on the source station
110
, passing that data to the application layer
112
and down through the layers of the protocol stack
125
, where the data are sequentially formatted as a frame for delivery onto the network communications medium
180
as bits. Those frame bits are then transmitted over an established connection of medium
180
to the protocol stack
175
of the destination station
150
where they are passed up the layers
166
,
160
,
164
,
162
,
156
,
154
, and
152
of that stack
175
to a receiving process
174
. Data flow is schematically illustrated by solid arrows.
Although actual data transmission occurs vertically through the stacks, each layer is programmed as though such transmission were horizontal. That is, each layer in the source station
110
is programmed to transmit data to its corresponding layer in the destination station
150
, as schematically shown by dotted arrows. To achieve this effect, each layer of the protocol stack
125
in the source station
110
typically adds information (in the form of a header) to the data generated by the sending process as the data descends the stack.
For example, the network layer encapsulates data presented to it by the transport layer within a packet having a network layer header. The network layer header contains, among other information, source and destination (logical) network addresses needed to complete the data transfer. The data link layer, in turn, encapsulates the packet in a frame that includes a data link layer header containing information required to complete the data link functions, such as (physical) MAC addresses. At the destination station
150
, these encapsulated headers are stripped off one-by-one as the frame propagates up the layers of the stack
175
until it arrives at the receiving process.
A “client/server network” is one conventional type of computer network architecture wherein data files stored or residing in one or more computer nodes (commonly termed “server” computer nodes or “servers”) in the network are shared, using a distributed computer file system, by multiple processes (commonly termed “client processes”) executing/residing in other computer nodes (commonly termed “client” computer nodes) in the network. That is, data files and their characteristics stored or residing in the one or more server computer nodes may be accessed and modified via the distributed file system, by multiple client processes executing/residing in the client computer nodes.
The client/server network architecture offers advantages over other types of network architectures. For example, since in a client/server network, data files residing in a server computer node may be accessed by client processes residing in the client computer nodes, copies of these files need not also resi
Cesari and McKenna LLP
Cisco Technology Inc.
Ly Anh
Vu Kim
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