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Selasa, 13 Julai 2010

NETWORK ARCHITECTURE

Definition:
The applications architecture is specified on the basis of business requirements. This involves defining the interaction between application packages, databases, and middleware systems in terms of functional coverage. This helps identify any integration problems or gaps in functional coverage. A migration plan can then be drawn up for systems which are at the end of the software life cycle or which have inherent technological risks.
Applications Architecture means managing how multiple applications are poised to work together. It is different from Software Architecture which deals with design concerns of one application.[citation needed]
[edit] Application Architecture Strategy
Strategy by definition is a stance and does not involve any action. Application Architecture Strategy involves ensuring the applications and the integrations align with the growth strategy of the Organization. If an organization is a manufacturing organization with fast growth plans through acquisitions, the application architecture should be nimble enough to encompass inherited legacy systems as well as other large competing applications.
[edit] Application Architecture Patterns
Applications can be classified in various types depending on the Application Architecture Pattern they follow.
A "pattern" has been defined as: "an idea that has been useful in one practical context and will probably be useful in others”
To create patterns, one needs building blocks. Building blocks are components of software, mostly reusable, which can be utilised to create certain functions. Patterns are a way of putting building blocks into context and describe how to use the building blocks to address one or multiple architectural concerns.
An application is a compilation of various functionalities all typically following the same pattern. This pattern defines the application’s pattern
All applications follow one of the following industry-standard Application Architecture Patterns
Client-Proxy Server: Acts as a concentrator for many low-speed links to access a server.
Customer Support: Supports complex customer contact across multiple organisations.
Reactor: Decouples an event from its processing.
Replicated Servers: Replicates servers to reduce burden on central server.
Layered Architecture: A decomposition of services such that most interactions occur only between neighboring layers.
Pipe and Filter Architecture: Transforms information in a series of incremental steps or processes.
Subsystem Interface: Manages the dependencies between cohesive groups of functions (subsystems).
Service: Users accessing transactions on a 24x7 basis (a.k.a. user-to-business)
Collaboration: Users working with one another to share data and information (a.k.a. user-to-user)
Information Aggregation: Data from multiple sources aggregated and presented across multiple channels (a.k.a. user-to-data)
Extended Enterprise: Integrating data and processes across enterprise boundaries (a.k.a. business-to-business)
The right application pattern depends on the organisation's industry and use of the component applications. An organisation could have a mix of multiple patterns if it has grown both organically and through acquisitions

Selasa, 6 Julai 2010

DEFINITION OF LAN, MAN , AND , WAN

LAN OR LOCAL AREA NETWORK:

A local area network (LAN) is a network that connects computers and other devices in a relatively small area, typically a single building or a group of buildings.

Most LANs connect workstations and personal computers and enable users to access data and devices (e.g., printers and modems) anywhere on the network. Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions.

LANs can be characterized by their topology, protocols and media. Topology is the geometric arrangement of devices on the network. For example, devices can be arranged in a ring or in a straight line. Protocols are the rules and encoding specifications for sending data. They also determine whether the network uses a peer-to-peer or client/server architecture. The most common type of LAN is Ethernet. Media is what is used to connect the devices, i.e., twisted-pair copper wire, coaxial cables, fiber optic cables or radio waves.

LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line because of their short distances and the fact that they do not have to rely on copper wire media (with its limited capacity). However, the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN.

Computers on a smaller LAN typically share the resources of a single server, which provides application programs and datastorage. Users who need an application can download it once and then run it from their local hard disk drive (HDD). They can order printing and other services as needed through applications that run on the LAN server.

A local area network may serve as few as one or two users (for example, in a home network) or as many as thousands of users (for example, in a large company).

LANs can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN).

MAN OR METROPOLITAN AREA NETWORK:
A Metropolitan Area Network, or MAN, is a series of LANs (Local Area Networks) that are interconnected through various means in a Metropolitan area such as a city and its subburbs.

If a company has a few offices in the same city, and the computer users at each location are able to share data between the two offices, they are generally doing this over a MAN.

WAN OR WIDE AREA NETWORK:

Definition: A WAN spans a large geographic area, such as a state, province or country. WANs often connect multiple smaller networks, such as local area networks (LANs) or metro area networks (MANs).
The world's most popular WAN is the Internet. Some segments of the Internet, like
VPN-based extranets, are also WANs in themselves. Finally, many WANs are corporate or research networks that utilize leased lines.
WANs generally utilize different and much more expensive networking equipment than do LANs. Key technologies often found in WANs include
SONET, Frame Relay, and ATM.

COMPUTER NETWORKS AND COMMUNICATIONS

COMPUTER NETWORK

Meaning:
A computer network, often simply referred to as a network, is a collection of computers and devices connected by communications channels that facilitates communications among users and allows users to share resources with other users. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of types and categories and also presents the basic components of a network.
TYPE OF COMPUTER NETWORK:
LOCAL AREA NETWORK (LAN), METROPOLITAN AREA NETWORK (MAN), WIDE AREA NETWORK (WAN).