Networking Introduction Part 2
Ethernet
Ethernet is the most popular
physical layer LAN technology in use today. It defines the number of conductors
that are required for a connection, the performance thresholds that can be
expected, and provides the framework for data transmission. A standard Ethernet
network can transmit data at a rate up to 10 Megabits per second (10 Mbps).
Other LAN types include Token Ring, Fast Ethernet, Gigabit Ethernet, 10 Gigabit
Ethernet, Fiber Distributed Data Interface (FDDI), Asynchronous Transfer Mode
(ATM) and LocalTalk.
Ethernet is popular because it
strikes a good balance between speed, cost and ease of installation. These
benefits, combined with wide acceptance in the computer marketplace and the
ability to support virtually all popular network protocols, make Ethernet an
ideal networking technology for most computer users today.
The Institute for Electrical and
Electronic Engineers developed an Ethernet standard known as IEEE Standard
802.3. This standard defines rules for configuring an Ethernet network and also
specifies how the elements in an Ethernet network interact with one another. By
adhering to the IEEE standard, network equipment and network protocols can
communicate efficiently.
Fast
Ethernet
The Fast Ethernet standard (IEEE
802.3u) has been established for Ethernet networks that need higher
transmission speeds. This standard raises the Ethernet speed limit from 10 Mbps
to 100 Mbps with only minimal changes to the existing cable structure. Fast
Ethernet provides faster throughput for video, multimedia, graphics, Internet
surfing and stronger error detection and correction.
There are three types of Fast
Ethernet: 100BASE-TX for use with level 5 UTP cable; 100BASE-FX for use with
fiber-optic cable; and 100BASE-T4 which utilizes an extra two wires for use
with level 3 UTP cable. The 100BASE-TX standard has become the most popular due
to its close compatibility with the 10BASE-T Ethernet standard.
Network managers who want to
incorporate Fast Ethernet into an existing configuration are required to make many
decisions. The number of users in each site on the network that need the higher
throughput must be determined; which segments of the backbone need to be
reconfigured specifically for 100BASE-T; plus what hardware is necessary in
order to connect the 100BASE-T segments with existing 10BASE-T segments.
Gigabit Ethernet is a future technology that promises a migration path beyond
Fast Ethernet so the next generation of networks will support even higher data
transfer speeds.
Gigabit
Ethernet
Gigabit Ethernet was developed to
meet the need for faster communication networks with applications such as
multimedia and Voice over IP (VoIP). Also known as
“gigabit-Ethernet-over-copper” or 1000Base-T, GigE is a version of Ethernet
that runs at speeds 10 times faster than 100Base-T. It is defined in the IEEE
802.3 standard and is currently used as an enterprise backbone. Existing
Ethernet LANs with 10 and 100 Mbps cards can feed into a Gigabit Ethernet
backbone to interconnect high performance switches, routers and servers.
From the data link layer of the OSI
model upward, the look and implementation of Gigabit Ethernet is identical to
that of Ethernet. The most important differences between Gigabit Ethernet and
Fast Ethernet include the additional support of full duplex operation in the
MAC layer and the data rates.
10
Gigabit Ethernet
10 Gigabit Ethernet is the fastest
and most recent of the Ethernet standards. IEEE 802.3ae defines a version of
Ethernet with a nominal rate of 10Gbits/s that makes it 10 times faster than
Gigabit Ethernet.
Unlike other Ethernet systems, 10
Gigabit Ethernet is based entirely on the use of optical fiber connections.
This developing standard is moving away from a LAN design that broadcasts to
all nodes, toward a system which includes some elements of wide area routing.
As it is still very new, which of the standards will gain commercial acceptance
has yet to be determined.
Asynchronous
Transfer Mode (ATM)
ATM is a cell-based fast-packet
communication technique that can support data-transfer rates from sub-T1 speeds
to 10 Gbps. ATM achieves its high speeds in part by transmitting data in
fixed-size cells and dispensing with error-correction protocols. It relies on
the inherent integrity of digital lines to ensure data integrity.
ATM can be integrated into an
existing network as needed without having to update the entire network. Its
fixed-length cell-relay operation is the signaling technology of the future and
offers more predictable performance than variable length frames. Networks are
extremely versatile and an ATM network can connect points in a building, or
across the country, and still be treated as a single network.
Power
over Ethernet (PoE)
PoE is a solution in which an
electrical current is run to networking hardware over the Ethernet Category 5
cable or higher. This solution does not require an extra AC power cord at the
product location. This minimizes the amount of cable needed as well as
eliminates the difficulties and cost of installing extra outlets.
LAN
Technology Specifications
Name
|
IEEE Standard
|
Data Rate
|
Media Type
|
Maximum Distance
|
Ethernet
|
802.3
|
10 Mbps
|
10Base-T
|
100 meters
|
Fast Ethernet/
100Base-T |
802.3u
|
100 Mbps
|
100Base-TX
100Base-FX |
100 meters
2000 meters |
Gigabit Ethernet/
GigE |
802.3z
|
1000 Mbps
|
1000Base-T
1000Base-SX 1000Base-LX |
100 meters
275/550 meters 550/5000 meters |
10 Gigabit Ethernet
|
IEEE 802.3ae
|
10 Gbps
|
10GBase-SR
10GBase-LX4 10GBase-LR/ER 10GBase-SW/LW/EW |
300 meters
300m MMF/ 10km SMF 10km/40km 300m/10km/40km |
Token
Ring
Token Ring is another form of
network configuration. It differs from Ethernet in that all messages are
transferred in one direction along the ring at all times. Token Ring networks
sequentially pass a “token” to each connected device. When the token arrives at
a particular computer (or device), the recipient is allowed to transmit data
onto the network. Since only one device may be transmitting at any given time,
no data collisions occur. Access to the network is guaranteed, and
time-sensitive applications can be supported. However, these benefits come at a
price. Component costs are usually higher, and the networks themselves are
considered to be more complex and difficult to implement. Various PC vendors
have been proponents
Token Ring networks.
Token Ring networks.
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