A network is any collection of two or more independent computers that communicate with one another over a shared network medium. When these computers are joined in a network, people can share files and peripherals such as modems, printers, tape backup drives, or CD-ROM drives.
Putting together a network is not as simple as cabling two PCs together. For a fully functional network, three primary components must be involved, they include; server, clients or workstations and resource. No network would be complete without these components working together.
Computer networks can be categorized in severe different ways; such as Local Area Networks (LANs) that reaches across a single home, Wide Area Networks (WANs) that reaches across cities, states and even across the world, and wireless LANs and WANs.
Computer network also differ in their design, the two types of high-level network design are client-server and peer-to-peer design. The client/server model is basically an implementation of distributed or cooperative processing.It is the most efficient way to provide:
• Databases and management of applications such as Spreadsheets, Accounting, Communications and Document management.
• Network management.
• Centralized file storage.
In peer-to-peer networking there are no dedicated servers or hierarchy among the computers. All of the computers are equal and that is why the word Peer is used. Peer-to-peer networks are good choices for needs of small organizations where the users are allocated in the same general area.
The layout or structure of computer network from the point of view of data flow also differ, we have for instance bus, star, mesh ring structure.
In networking, the communication language used by computer devices is called protocols; a networking protocol is a set of standards that governs communications among computing systems. These protocols include TCP/IP, HTTP and SMTP (Simple Mail Transport Protocol is the primary application layer protocol for electronic mail).
Network also work with addresses that gives the computer unique identities that they can use to communicate with each other, these addresses include IP addresses and MAC addresses.
Router: a specialized network device that determines the next network point to which it can forward a data packet towards the destination of the packet. Unlike a gateway, it cannot interface different protocols. It operates at OSI layer 3.
Bridge: a device that connects multiple network segments along the data link layer. This device works on OSI layer 2.
Switch: a device that allocates traffic from one network segment to certain lines (intended destination(s)) which connect the segment to another network segment. So unlike a hub a switch splits the network traffic and sends it to different destinations rather than to all systems on the network. It also works on OSI layer 2.
Hub: connects multiple Ethernet segments together making them act as a single segment. When using a hub, every attached all the objects, compared to switches, which provide a dedicated connection between individual nodes. Works on OSI layer 1.
Repeater: device to amplify or regenerate digital signals received while sending them from one part of a network into another. Works on OSI layer 1.
Some hybrid network devices:
Multilayer Switch: a switch which, in addition to switching on OSI layer 2 provides functionality at higher protocol layers.
Protocol Converter: a hardware device that converts between two different types of transmissions, such as asynchronous and synchronous transmissions.
Bridge Router (B router): Combines router and bridge functionality and are therefore working on OSI layers 2 and 3.
Hardware or software components that typically sit on the connection point of different networks, e.g. between an internal network and an external network:
Proxy: computer network service which allows clients to make indirect network connections to other network services
Firewall: a piece of hardware or software put on the network to prevent some communications forbidden by the network policy. It is mainly used for network security.
Network Address Translator: network service provide as hardware or software that converts internal to external network addresses and vice versa
Other hardware for establishing networks or dial-up connections:
Multiplexer: device that combines several electrical signals into a single signal
Network interface controller a piece of computer hardware to allow the attached computer to communicate by network
Wireless network interface controller a piece of computer hardware to allow the attached computer to communicate by LAN
Modem: device that modulates an analog "carrier" signal (such as sound), to encode digital information, and that also demodulates such a carrier signal to decode the transmitted information, as a computer communicating with another computer over the telephone network
ISDN terminal adapter (TA): a specialized gateway for ISDN
Line Driver: a device to increase transmission distance by amplifying the signal. Base-band networks only.
ABBREVIATIONS USED
OSI – Open System Interconnection
TA - Terminal Adapter
TCP/IP – Transmission Control Protocol/Internet Protocol
HTTP – Hyper Text Transfer Protocol
SMTP – Simple Mail Transfer Protocol
WAN – Wide Area Network
LAN – Local Area Network
CD-ROM – Compact Disk-Read Only Memory
PCs – Personal Computers
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