Computer networking is the scientific and engineering discipline
communication between computer systems. Such networks
involve at least two computers separated by a few inches (e.g. via
Bluetooth) or thousands of miles (e.g. via the Internet). Computer
networking is sometimes considered a sub-discipline of
Types of Networks
Local Area Netword
A local area network (LAN) is a computer network covering a small
local area, like a home, office, or small group of buildings such as a
home, office, or college. Current LANs are most likely to be based on
switched Ethernet or Wi-Fi technology running at 10, 100 or 1,000 Mbit/s
(1,000 Mbit/s is also known as 1 Gbit/s).
The defining characteristics of LANs in contrast to WANs are: a) much
higher data rates, b) smaller geographic range - at most a few
kilometers - and c) they do not involve leased telecommunication lines.
"LAN" usually does not refer to data running over local analog
telephone lines, as on a private branch exchange (PBX).
Wider Area Network
A wide area network or WAN is a computer network covering a wide
geographical area, involving a vast array of computers. This is
different from personal area networks (PANs), metropolitan area networks
(MANs) or local area networks (LANs) that are usually limited to a room,
building or campus. The most well-known example of a WAN is the
WANs are used to connect local area networks (LANs) together, so that
users and computers in one location can communicate with users and
computers in other locations. Many WANs are built for one particular
organization and are private. Others, built by Internet service
providers, provide connections from an organization's LAN to the
Internet. WANs are most often built using leased lines. At each end of
the leased line, a router connects to the LAN on one side and a hub
within the WAN on the other. Network protocols including TCP/IP deliver
transport and addressing functions. Protocols including Packet over
SONET/SDH, MPLS, ATM and Frame relay are often used by service providers
to deliver the links that are used in WANs. X.25 was an important early
WAN protocol, and is often considered to be the "grandfather"
of Frame Relay as many of the underlying protocols and functions of X.25
are still in use today (with upgrades) by Frame Relay.
Metropolitan Area Network
Metropolitan Area Networks or MANs are large computer networks
usually spanning a campus or a city. They typically use wireless
infrastructure or optical fiber connections to link their sites. For
instance a university or college may have a MAN that joins together many
of their local area networks (LANs) situated around site of a fraction
of a square kilometer. Then from their MAN they could have several wide
area network (WAN) links to other universities or the Internet.
Some technologies used for this purpose are ATM, FDDI and SMDS. These
older technologies are in the process of being displaced by
Ethernet-based MANs (e.g. Metro Ethernet) in most areas. MAN links
between LANs have been built without cables using either microwave,
radio, or infra-red free-space optical communication links. DQDB,
Distributed Queue Dual Bus, is the Metropolitan Area Network standard
for data communication. It is specified in the IEEE 802.6 standard.
Using DQDB, networks can be up to 30 miles long and operate at speeds of
34 to 155 Mbit/s. Several notable networks started as MANs, such as the
Internet peering points MAE-West and MAE-East and the Sohonet media
Personal Area Network
A personal area network (PAN) is a computer network used for
communication among computer devices (including telephones and personal
digital assistants) close to one person. The devices may or may not
belong to the person in question. The reach of a PAN is typically a few
meters. PANs can be used for communication among the personal devices
themselves (intrapersonal communication), or for connecting to a higher
level network and the Internet (an uplink).
Personal area networks may be wired with computer buses such as USB
and FireWire. A wireless personal area network (WPAN) can also be made
possible with network technologies such as IrDA and Bluetooth.
The Internet, or simply the Net, is the publicly accessible worldwide
system of interconnected computer networks that transmit data by packet
switching using a standardized Internet Protocol (IP). It is made up of
thousands of smaller commercial, academic, domestic, and government
networks. It carries various information and services, such as
electronic mail, online chat, and the interlinked Web pages and other
documents of the World Wide Web.
Contrary to some common usage, the Internet and the World Wide Web
are not synonymous: the Internet is a collection of interconnected
computer networks, linked by copper wires, fiber-optic cables, wireless
connections etc.; the Web is a collection of interconnected documents,
linked by hyperlinks and URLs, and is accessible using the Internet.
A network topology is the pattern of links connecting pairs of nodes
of a network. A given node has one or more links to others, and the
links can appear in a variety of different shapes. The simplest
connection is a one-way link between two devices. A second return link
can be added for two-way communication. Modern communications cables
usually include more than one wire in order to facilitate this, although
very simple bus-based networks have two-way communication on a single
wire. Network topology is determined only by the configuration of
connections between nodes; it is therefore a part of graph theory.
Distances between nodes, physical interconnections, transmission rates,
and/or signal types are not a matter of network topology, although they
may be affected by it in an actual physical network.
A bus network is a network architecture in which a set of clients are
connected via a shared communications line, called a bus. There are
several common instances of the bus architecture, including one in the
motherboard of most computers, and those in some versions of Ethernet
Star networks are one of the most common computer network topologies.
In its simplest form, a star network consists of one central switch, or
hub computer which acts as a router to transmit messages.
A ring network is a topology of computer networks where each node is
connected to two other nodes, so as to create a ring. The most popular
example is a token ring network. Ring networks tend to be inefficient
when compared to star networks because data must travel through more
points before reaching its destination. For example, if a given ring
network has eight computers on it, to get from computer one to computer
four, data must travel from computer one, through computers two and
three, and to its destination at computer four. It could also go from
computer one through eight, seven, six, and five until reaching four,
but this method is slower because it travels through more computers.
Mesh networking is a way to route data, voice and instructions
between nodes. It allows for continuous connections and reconfiguration
around blocked paths by "hopping" from node to node until a
connection can be established. Mesh networks are self-healing: the
network can still operate even when a node breaks down or a connection
goes bad. As a result, a very reliable network is formed. This concept
is applicable to wireless networks, wired networks, and software
A star-bus network is a combination of a star network and a bus
network. A hub (or concentrator) is used to connect the nodes to the
network. It is a combination of the linear bus and star topologies and
operates over one main communication line.
Computer networking devices are units that mediate data in a computer
network. Computer networking devices are also called network equipment,
Intermediate Systems (IS) or InterWorking Unit (IWU). Units which are
the last receiver or generate data are called hosts or data terminal
Common basic network devices:
- Gateway: device sitting at a network node for interfacing with
another network that uses different protocols. Works on OSI layers 4
- Router: a specialized network device that determines the next
network point to which to forward a data packet toward its
destination. Unlike a gateway, it cannot interface different
protocols. Works on OSI layer 3.
- Bridge: a device that connects multiple network segments along the
data link layer. 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. Works on OSI layer 2.
- Hub: connects multiple Ethernet segments together making them act
as a single segment. When using a hub, every attached device shares
the same broadcast domain and the same collision domain. Therefore,
only one computer connected to the hub is able to transmit at a
time. Depending on the network topology, the hub provides a basic
level 1 OSI model connection among the network objects
(workstations, servers, etc). It provides bandwidth which is shared
among 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 setting them from one part of a network into another. Works on
OSI layer 1.
The term network monitoring describes the use of a system that
constantly monitors a computer network for slow or failing systems and
that notifies the
network administrator in case of outages via email,
pager or other alarms. It is a subset of the functions involved in
While an intrusion detection system monitors a network for threats
from the outside, a network monitoring system monitors the network for
problems due to overloaded and/or crashed servers, network connections
or other devices.
For example, to determine the status of a webserver, monitoring
software may periodically send an HTTP request to fetch a page; for
email servers, a test message might be sent through SMTP and retrieved
by IMAP or POP3.
Status request failures, such as when a connection cannot be
established, it times-out, or the document or message cannot be
retrieved, usually produce an action from the monitoring system. These
actions vary: an alarm may be sent out to the resident sysadmin,
automatic failover systems may be activated to remove the troubled
server from duty until it can be repaired, etcetera.
Monitoring the performance of a network uplink is also known as
network traffic measurement, and more software is listed there. [Source:
compiled from many articles at wikipedia]
Links to Computer Networking
ITtoolbox: Provides a knowledge network and support environment for the IT industry. As IT professionals or business decision-makers need information to complete a task or make a decision, they turn to ITtoolbox to quickly get specific answers to their unique questions.ITtoolbox provides a knowledge network and support environment for the IT industry. As IT professionals or business decision-makers need information to complete a task or make a decision, they turn to ITtoolbox to quickly get specific answers to their unique questions.
Networking on the Network: "Networking on the Network" includes good advice accumulated from dozens of people over many years, and I want to get it into the hands of every PhD student in the world. If you could help me out with this goal, I would much appreciate it.
ZDNet Networking: Regular updates, news, articles, features and more. ZDNET provides an invaluable perspective and resources so that users can get the most out of their investments in technology.
Cisco Networking Academy Program: The Cisco Networking Academy Program is a partnership between Cisco Systems, education, business, government, and community organizations around the world. The Networking Academy curriculum centers on teaching students to design, build, and maintain computer networks. The Program prepares students for the 21st Century workplace, while serving as a valuable model for e-learning.
Networking Search Engine & Resource Our goal is to: Unearth networking information buried out there! Disseminate networking knowledge! Our task is to determine who solved a given network problem first. Alternately, who published first a publication on a given computer network field. It is a sort of computer network historian job. That is why you see dates at the end of the links. If you know a good reference with early date please let us know. We surely appreciate your input.
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Cisco Systems - Networking for the Internet - If anyone can lay claim to a 'heritage' in an industry as young as global networking, then it is Cisco. Not only does 85 per cent of Internet traffic travel across Cisco's systems, we also use the Internet to run our on business online, from product orders and inventory management through to staff communications and travel expenses.
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MyTutorials.com - MyTutorials.com is the first collaborative learning site. MyTutorials.com allows the Internet community to ask for assistance, teach others about a topic, and find answers to their questions. Each of the tutorials on the site is editable by anyone and everyone. The best suggestions and improvements are combined into the final tutorial - making MyTutorials the destination for online learning.
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