71192306_Topic: Local Area Network (LAN) Technologies REPORT
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Local Area Network (LAN) Technologies Report1
Introduction
Local Area Network, LAN, is a data communications network
connecting terminals, computers, and printers within a building or
other geographically limited areas (Haugdahl, 1999, p. 76). These
devices may be connected through wired cables or wireless links.
LAN is usually owned by an individual or a single entity such as an
organization, and the users communicate with each other by sending
e-mail or by chatting. In a LAN technology, applications are stored
in the LAN server (Haugdahl, 1999, p. 76), allowing the users to
exchange resources with each other at the LAN server. LANs can
transmit data at a rate faster than data transferred over a
telephone line, and can also be connected to other LANs. The major
LAN technologies are Ethernet and Token Ring. This paper discussed
these two technologies in detail.EthernetIntroduction Ethernet is
by far the most widely used Local Area Networking, LAN, technology
used in the world today. Ethernet was the brainchild of Bob
Metcalfe and David Boggs (Haugdahl, 1999, p 77) The standard was
created at Xerox Palo Alto Research Centre, PARC in 1973 (Haugdahl,
1999, p. 77), for networking a group of computers that could all
use a new Laser printer that Xerox had made. The original version
of the Ethernet operated at 2.9 Mbps (Haugdahl, 1999, p. 77), a
speed that was chosen because it was a multiple of the clock speed
of the original Alto computer created by Xerox in 1972 as a
personal computer targeted at research. The original Ethernet
standard was developed over the next few years, and this resulted
in a paper Ethernet: Distributed Packet-Switching for Local
Computer Networks published in the Communications of ACM, Vol. 19,
No. 5, July 1976, pp. 395-404 (Shepard, 2002, p. 84). Later a
consortium of three companies Digital Equipment Corporation, Intel,
and Xerox, further developed the Ethernet II or the DIX standard
(Mueller & Ogletree, 2003, p. 207). These companies used the
networking technology to add networking capabilities to their
product line. Ethernet has adapted over the years running on newer
devices and running media and can now run on coaxial cables,
twisted-pair wiring and fiber-optic coupling (Mueller &
Ogletree, 2003, p. 207).Purpose and Function The initial place for
the usage of Ethernet was for connecting office equipments, as is
seen above. The standard is pretty much an international standard
for this purpose even in the present days. Ethernet is basically a
bus structure in which all the signals are sequentially carried on
a single wire. The Ethernet standard extends only over hardware and
signal levels (Mueller & Ogletree, 2003, p. 207) An Ethernet
network can operate under a variety of network protocols (Mueller
& Ogletree, 2003, p. 207); it is even possible to support two
different network protocols simultaneously on an Ethernet
cable.Accepted places for usage Ethernet has established itself as
the de facto standard for PC networks (Mueller & Ogletree,
2003, p. 207). It has become the most widely used communications
medium. Due to its present wide acceptance, Ethernet has also been
suggested for use in many diverse application fields such as
automations, and even embedded systems (Mueller & Ogletree,
2003, p. 208).Pros and Cons Following are the advantages with
Ethernet
1. One of the major advantages of the Ethernet is that it is
already compatible with the existing industry-standard PC software
and hardware. PCs generally include Ethernet interfaces and all the
commercial operating systems have built-in Ethernet drivers
(Bedell, 2002, p. 28).
2. As compared to token-passing networks Ethernet has already
proved to be scalable with high performance. Ethernet also has
longer-range distances up to 150km when used in fiber based-LX
mode. The standard is full-duplex, symmetrical and switched
(Bedell, 2002, p. 28).3. A main reason for the Ethernet becoming a
de facto standard is because it is less expensive to implement.
Also since Ethernet has been evolving for about3 decades, there is
a large pool of professionals available who understand the standard
(Bedell, 2002, p. 28)4. Ethernet supports high bandwidth
applications and is a reliable medium with high level of security
(Bedell, 2002, p. 28)Following are the disadvantages with
Ethernet
1. Despite the low cost, Ethernet still requires new cables to
be installed for the home network
2. The Ethernet also requires a significant amount of
configurations by the users, which is not always easy 3. Ethernet
is a non-deterministic protocol and does not support any message
prioritization (Hristu-Varsakelis & Levine, 2005, p. 665).4.
Because of the required minimum valid frame size, Ethernet uses a
large frame size to transmit a small amount of data
(Hristu-Varsakelis & Levine, 2005, p. 665). This causes high
traffic loads, which are a major problem because they greatly
affect data throughput and time delays may become unbounded.
Market share - Ethernet dominates over 90 percent of the
installed networks worldwide (Ballew, 1997, p. 34). Ethernet
networks are used in all major industries where the requirement for
high-speed reliable communications is a necessity.Current level of
implementation There are three types of Ethernet, primarily
distinguished from one another by speed:1. 10-Mbps Ethernet This
was the original Ethernet standard which was enhanced in 1980 and
became known as IEEE 802.3 The Ethernet uses shielded twisted pair
cable, unshielded twisted pair cable or coaxial cable, and works at
a maximum speed of 10 M bits per second (Andrews, 2003, p.
469).
2. 100-Mbps Ethernet or Fast Ethernet This is the improved
version of 10-Mbps Ethernet, and is also known sometimes as
100BaseT. The maximum data speed is 100 M bits per second. This
standard uses either a shielded twisted pair cable or a unshielded
twisted pair cable. The standard is downward compatible with
10-Mbps Ethernet. Two variations of 100BaseT are 100BaseTX and
100BaseFX, the latter using optical fibers (Andrews, 2003, p.
469).
3. Gigabit Ethernet This is the latest version of Ethernet and
is also known as 1000-Mbps Ethernet, because of the maximum data
speed. The protocol uses twisted-pair cables or optical fibers. It
is used for high-speed LAN backbones and for server-to-server
connections (Andrews, 2003, p. 469). Token RingIntroduction Token
Ring is the second most widely used Local Area network, LAN,
technology after Ethernet. IBM originally developed the Token Ring
in 1970. The credit for the technology however goes to a fellow
named Olaf Soderblum, who developed the token ring passing network
to connect IBM mainframes in Sweden (Shipley, 2002, p. 24).
However, the IBM Token Ring Network, TRN, did not appear on the
scene until 1985, when the protocol was standardized by IEEE as
802.5 with a speed of 4Mbps (Shipley, 2002, p. 24). Soon IBM front
end processors, such as the IBM 3745s, were shipped with Token Ring
interfaces (Shipley, 2002, p. 24). At the time Token Ring provided
a fast LAN medium, and was an immediate success with IBM customers,
primarily because aside form PC Net, it was the only LAN that IBM
really endorsed at the time. The market share of Token Ring was
almost 35% till the middle 1990s (Shipley, 2002, p. 24), even
though it was an expensive alternative to the Ethernet. Purpose and
Function Token Ring is much more suitable than Ethernet for delay
sensitive applications like the IBM Systems Network Architecture,
SNA. Token Ring is also recommended for image applications
(Shipley, 2002, p. 24)Accepted places for usage Token Ring LANs,
like Ethernet LANs are common in office environments, linking
personal computers for the purpose of data file transfer,
electronic messaging, mainframe computer interaction and file
sharing. Token Ring is the best choice for a framework if the
performance of the network is the most important concern and not
the network up time (Mueller & Ogletree, 2003, p. 210).Pros and
Cons Following are the advantages with Token Rings1. The main
advantage of Token Ring is that all the nodes of the network have
equal chance of transmitting the data (Shinder, 2001, p. 145).
2. Token Ring network uses the available bandwidth more
efficiently than Ethernet (Shinder, 2001, p. 145).
3. Token Ring can provide duplicate MAC address support, which
Ethernet cannot provide (Shinder, 2001, p. 145).4. Token Ring is a
highly reliable architecture, and its token passing scheme
eliminates data collisions (Shinder, 2001, p. 145)5. Token Ring can
also detect and isolate a faulty node, so the network is not
brought down by the failure of one computer (Shinder, 2001, p.
145).
Following are the disadvantages with Token Rings
1. Ethernet devices are simpler than Token Ring devices
(Shinder, 2001, p. 145).2. Economies of scale make Ethernet much
less expensive than Token Ring (Shinder, 2001, p. 145).
3. Ethernet also overcomes its efficiency problem by being much
faster than the Token Ring (Shinder, 2001, p. 145).
4. A major limitation with the Token Ring is also its
availability, while many present day machines come equipped with
Ethernet, or one can be installed easily, the same cannot be said
for a Token Ring Interface (Ballew, 1997, p. 34).
Market share While Token ring networks are not nearly as
plentiful as Ethernet Networks, they are found at most major data
centers running IBM mainframes. The reason for this is because
Token ring networks are more expensive to implement than Ethernet
networks (Ballew, 1997, p. 34). Current level of implementation
Token Ring, as is mentioned above, is a set of network standards
developed by IBM that define a complete network system. The
standard is completely incompatible with Ethernet and is considered
as its competitor. Token Ring networks use a Ring topology, most
commonly today as a star ring. The topologies here are wired into a
star configuration using shielded twisted pair cable or unshielded
twisted pair cable. The networks are classified into: small movable
networks that support up to 96 nodes and 12 Multi-station Access
Units, MAU and, large non-movable networks that support up to 260
nodes and 30 MAUs (Barrett & King, 2005, p. 136-137).
References
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