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The
Fundamental of Computer Network
What's Network?
Computer Network is a group of computers
(at least 2 computers) that connected and shared resources to each
other for example: Internet, printer, CD-ROM, etc.
Computers in computer network can be connected to each other by
using Cable, Telephone line, Radio wave, Satellite or Infrared.
Type of Computer network.
Normally, they separate computer network
into 3 types depended on the size of each network:
- Local Area Network (LAN): a small network that covers small area
for example: computer network in an office, in same building.
- Metropolitan Area Network (MAN): a middle network that covers
more area than LAN for example: computer network inside the same
province. MAN might use telephone line, cable or wireless to connect
computers inside its network.
- Wide Area Network (WANs): a large network that covers more area
than MAN and LAN for example: computer network between province,
countries. This kind of network always use high-speed media because
a large amount of data will be exchanged among the sub-networks.
LAN Topology.
There are 3 kind of LAN Topology:
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1. STAR: all computers will
connect to each other through a HUB. |
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2. BUS: all computers will
connect to main cable (BUS). Each computer can connect directly
to each other. |
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3. RING: all computers
will connect serially to each other. Each computer will send
data as cycle. |
Media Access Control.
Computer network is the system that computer
share cable to send data. So, it's important to control cable-sharing
system. There are 2 kind of cable sharing system:
CSMA/CD (Carrier Sense Multiple Access /
Collision Detection)
In CSMA/CD, sending machine will wait for 'carrier detection' signal,
if cable frees it will send data to destination computer. If data
lost or error, it will resend data until destination computer can
get data. This system is not complication but it'll slow down and
percent of data error will increase when there are more computers
in network.
Token-passing
System will work in order of Token signal. When a computer get Token
signal, that computer can send data and finish sending data by 'End
Token signal'. If it doesn't want to send any data, it'll send Token
signal to other computer. This system is more believable.
Standard of LAN system.
1. Ethernet (IEEE 802.3) is used in
BUS Topology and STAR Topology. This system uses CSMA/CD standard
at speed of 10 Mbps or 100 Mbps Fast Ethernet (IEEE 802.3u). Hardware
has to support one of this standard or both to connect to network.
LAN's cable standard.
- 10Base2 - Ethernet specification for thin coaxial cable, transmits
signals at 10 Mbps (megabits per second) with a distance limit of
185 meters per segment.
- 10Base5 - Ethernet specification for thick coaxial cable, transmits
signals at 10 Mbps with a distance limit of 500 meters per segment.
- 10BaseF - Ethernet specification for fiber optic cable, transmits
signals at 10 Mbps with a distance limit of 2000 meters per segment.
- 10BaseT - Ethernet specification for unshielded twisted pair cable
(category 3, 4, or 5), transmits signals at 10 Mbps with a distance
limit of 100 meters per segment.
- 100BaseT - Ethernet specification for unshielded twisted pair
cabling that is used to transmit data at 100 Mbps with a distance
limit of 100 meters per segment.
- 100BaseTX -Ethernet specification for unshielded twisted pair
cabling that is used to transmit data at 1 Gbps with a distance
limitation of 220 meters per segment.
- AUI Connector (Attachment Unit Interface) - A 15 pin connector
found on Ethernet cards that can be used for attaching coaxial,
fiber optic, or twisted pair cable.
2. Arcnet: is STAR connection by using
Coaxial cable connecting between computer to HUB. This standard
is using cheaper equipment but have speed limited at 2.5 Mbps. It's
not used now.
3. Token-Ring (IEEE 802.5): is developed
by IBM. All computer will connect to each other as ring or using
HUB(special HUB that can't use with other standard) called Media
Access Unit(MAU) at speed of 4 Mbps and 16 Mbps.
Notice: There are many NIC and HUB standard
and can't use instead of other standard.
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