Overview of Networking Technologies
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Team uCertify October 05, 2006
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Team uCertify |
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Team uCertify
has written 8 articles for WebKnowHow. |
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A lot of processes are required for running a network in
addition to the network media through which the connections are made.
To ensure that all these processes operate flawlessly in complex
networking environments, there are some common standards and
technologies that are used for different types of networks.
The
Institute of Electrical and Electronic Engineers (IEEE) develops these
standards and technologies, which are followed by network engineers
throughout the world to design different types of networks. The
institute set up a task force known as the 802 committee in 1980 to
develop standards for establishing communication between different
computers in a network. These standards ensure the flow of data in the
data link layer of the OSI model. The most common data link protocols
directed by these standards and used in the present day networks are
Ethernet (IEEE 802.3), Token Ring (IEEE 802.5), and Wireless LAN (IEEE
802.11b). There is one more popular LAN protocol known as FDDI, which
is developed by American National Standards Institute (ANSI).
Ethernet (IEEE 802.3)
Conceived
in the 1960s, the Ethernet is the oldest and most popular data link
layer protocol (or network technology) used in today's networks.
Ethernet networks use a bus or star topology and control the flow of
data through the media access control (MAC) method, known as Carrier
Sense Multiple Access Collision Detection (CSMA/CD). The use of CSMA/CD
ensures that each computer in the network can send its signals over the
network. To send signals over the network, a computer waits for the
network to be free of any traffic; and if the network is free, it sends
its signals, which travel through the network and are received by the
destination computer. Sometimes, more than one computer sends its
signals over the network, which results in collision. Collisions in
these types of networks cannot be avoided, as CSMA/CD can detect them
only when they occur. It then sends the data over the network again to
compensate the data loss.
Ethernet networks run at the speeds of
10 to 1,000 Mbps, depending on the type of topology and cabling used.
Ethernet technology is widely implemented in Star topology using
coaxial or fiber optic cables and in bus topology using UTP cable.
Types of Ethernet
- 10 Base5
These
networks are also known as Thick Ethernet, as they use a thick coaxial
cable called RG 8 for data transmission. The number 10 specifies that
it provides a transmission speed of 10 Mbps for the network. The number
5 denotes that the maximum segment length provided by these networks is
500 meters. The maximum length of these networks can be increased up to
2.5 kilometers (1.5 mile) by using repeaters. 10 Base5 networks use bus
topology, and each computer is attached to the network by using
separate cables called Attachment Unit Interface (AUI). The important
specifications of these networks are stated in the table below:
Maximum segment length
| 500 meters
| Maximum segments
| 5
| Maximum repeaters
| 4
| Maximum overall length
| 2.5 kilometers
| Maximum AUI cable length
| 50 meters
| Topology
| Bus
| Cable
| Coaxial (RG 8)
|
- 10 Base2
The
common name used for these types of networks is Thin Ethernet as they
use a thin coaxial cable (RG 58), which is inexpensive, flexible and
easy to handle. 10 Base2 networks also use bus topology and provide a
speed of 10 Mbps with a maximum segment length of 185 meters. These
networks do not require an AUI, and the cables are connected directly
to the network interface cards of computers. The specifications of 10
Base2 networks are as follows:
Maximum segment length
| 185 meters
| Maximum segments
| 5
| Maximum repeaters
| 4
| Maximum overall length
| 925 meters
| Topology
| Bus
| Cable
| Coaxial (RG 58)
|
Note: 10 Base2 and 10 Base5 have been removed from the new Network+ objectives.
- 10 Base-T
These
networks use unshielded twisted pair cable that is more flexible, cost
effective, and easier to install than the coaxial cable. These networks
use star topology implemented logically as a bus in which a separate
cable to a hub connects every computer in the network. A 10 Base-T
network uses category 3, 4 or 5 cables with a maximum cable segment
length of 100 meters. These networks are cost effective and easy to
troubleshoot and provide a speed of 10 Mbps. 10 Base-T networks have
the following specifications:
Maximum segment length
| 100 meters
| Maximum segments
| 1024
| Maximum hubs
| 4
| Topology
| Star
| Cable
| UTP (Cat. 3, 4, or 5)
|
Maximum segment length
| 100 meters
| Speed
| 100 Mbps
| Topology
| Star
| Cable
| UTP (Cat. 5)
|
- 100 Base-T4
These
networks also run at the speed of 100 Mbps but use category 3 UTP
cable. 100 Base T4 networks use star topology, and the maximum segment
length of the cable is 100 meters. These networks use all the four
-wire- pairs of the category 3 cables, in which two pairs transmit and
receive data, and the other two carry the data in both directions to
provide high speed. These networks have the following specifications: - 100 Base-FX
This
is also a fast Ethernet network that runs at the speed of 100 Mbps
using Fiber optic cable with the segment lengths of up to 412 meters
for half duplex connections and 2,000 meters in full duplex
connections. The similarity between 100 Base FX and other fast Ethernet
specifications is the use of star topology. The following table lists
the 100 Base FX specifications:
Maximum segment length (half duplex)
| 412 meters
| Maximum segment length (full duplex)
| 2000 meters
| Speed
| 100 Mbps
| Topology
| Star
| Cable
| Fiber Optic
|
- 1000 Base-T
It
is a Gigabit Ethernet specification, which runs at a speed of 1000 Mbps
and has the maximum cable segment length of 100 meters. Although 1000
Base T requires category 6 UTP cable, it can also run on a category 5e
(enhanced) cable standard. These networks use all the four wire pairs
of the UTP cable for a faster flow of data in both directions
simultaneously. Computers in a 1000 Base T networks are connected using
a star topology. The main specifications of this standard are given
below:
Maximum segment length
| 100 meters
| Speed
| 1000 Mbps
| Topology
| Star
| Cable
| UTP(Cat 5e and higher)
|
- 1000 Base-CX
This
specification was in use before the launch of 1000 Base-T. It was used
for the networks spread over short distances, but it has now become
obsolete. These networks used shielded twisted pair (STP) cables, and
the maximum cable segment length was 25 meters.
- 1000 Base-SX
This
Ethernet specification utilizes the capabilities of fiber optic cables
to provide a speed of 1000 Mbps. SX stands for short wavelength laser
as it uses short wavelength laser over multimode fiber. The maximum
segment length for 1000 Base-SX is 550 meters.
- 1000 Base-LX
Like
1000 Base-SX, this specification is also a fiber optic variant of 1000
Base-CX, but it uses long wavelength laser over multimode and single
mode fiber to run at the speed of 1000 Mbps. The maximum segment length
of these networks is also 550 meters.
- 10GBase-SR
The
10 Gigabit Ethernet is the latest Ethernet standard approved by the
IEEE in June 2002. It uses only fiber optic cable and operates in full
duplex mode, providing the speed of 10 Gbps. These standards provide
the flexibility for use in LANs, MANs and WANs.
The 10Gbase-SR
operates on short wavelength (850 nm) multimode fiber and has a maximum
segment length of 2 meters to 300 meters depending on the type and
quality of the multimode fiber.
- 10GBase-LR
The
10Gbase-LR Ethernet specification operates on long wavelength (1310 nm)
single mode fiber. It provides a maximum segment length of 2 meters to
10 kilometers (or more), depending on the quality and type of the
single mode fiber cable.
- 10GBase-ER
This
is also a 10 GB Ethernet standard, which operates on extra long
wavelength (1550 nm) single mode fiber. The maximum segment length for
this specification is from 2 meters to 40 kilometers, depending on the
quality and type of cable used.
Token Ring (IEEE 802.5)
Originally
developed by IBM, the token ring is an intricate but highly dependable
networking technology that follows the IEEE 802.5 standard. The type of
topology used in this technology is physically a star, but implemented
logically as a ring, in which all the computers are attached to a
central unit called a multistation access unit (MAU OR MSAU). Token
ring networks use token passing to send their signals over the network.
Token is a type of data packet, which circulates in the entire network.
If the token is free, the computer waiting to send data takes it,
attaches the data and the destination address to the token, and sends
it. When the token reaches its destination computer, the data is
received. Then, the token gets back to the originator. If the
originator finds that the message has been received, it removes the
message from the token. Now, the token is free and can be used by the
other computers in the network to send data.
Token ring
networks are more fault-tolerant than the Ethernet, as the MSAU ensures
that the failure of a single computer does not bring the entire network
down. It is an intelligent device which can identify the failing
computer in the network, and then it bypasses it to correct the errors.
The modern day token ring networks use unshielded twisted pair
(UTP) cable and run at the speed of 16 Mbps as opposed to the original
token ring networks developed by IBM that used shielded twisted pair
(STP) cable and ran at 4 or 16 Mbps.
Wireless LAN (IEEE 802.11b)
The
IEEE 802.11b standard applies to wireless LAN Networks that use radio
waves as the transmission medium. These networks have their separate
media access control mechanism known as Carrier Sense Multiple Access
with Collision Avoidance (CSMS/CA), that works like the CSMA/CD
mechanism used by the Ethernet. The difference is that in this
protocol, when a computer sends its signals, the receiving computer
performs a cyclical redundancy check and sends an acknowledgement
message to the sending computer if no error is detected.
As
these networks are wireless, they do not use the traditional topologies
used by other networks. There are two types of wireless networks,
namely Ad hoc network and Infrastructure network. In an Ad hoc network,
a group of computers are connected using the IEE 802.11b data link
protocol and communicate as peers. In an Infrastructure network, the
computers are connected using wireless access points that are connected
to cables.
The wireless LANs run at the transmission speed of
11 Mbps with a fallback to 5.5, 2, and 1 Mbps in the 2.4 GHz bandwidth.
The radio transmission medium used by these networks is called Direct
Sequence Spread Spectrum (DSSS).
FDDI (Fiber Distributed Data Interface)
Developed
by the American National Standards Institute, FDDI is a ring-based
network that uses fiber optic cables to provide very fast and reliable
communication between the connected computers. It uses token passing to
control the network access, but unlike the token ring networks, it does
not use a hub; instead, it uses a central device called concentrator to
connect the computers in the network. In these networks the computers
are connected using physical ring topology.
There are two
types of configurations used by FDDI networks, namely class A and class
B configurations. In class A, a double ring topology is used in which
the computers are connected to two rings. The signals travel in
opposite directions on both the rings, and if there is a fault in one
ring, the receiving computer can still receive the signal through the
other ring. These networks provide a better fault tolerance. Class B
networks use a single physical ring and is, therefore, less fault
tolerant.
FDDI networks run at the speed of 100 Mbps and, as
they use fiber optic cables, they provide connectivity over long
distances. These networks have now been replaced by Fast Ethernet
networks that provide the same speed and are more fault tolerant.
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