1. LAN Technologies
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2. Objectives
• Understand different types of LAN technologies.
• Understand LAN transmission methods.
• Understand LAN topology.
• Explain different LAN media access methods.
• Understand several types of cabling used with LAN.
• Understand different types of protocols.
• Understand Ethernet technology.
• Understand different types of Ethernet collisions.
• Explain different causes of physical frame
corruption.
• Understand LAN segmentation.
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3. LAN Technology
A local area network (LAN) is a group of computers and
associated devices that share a common communications
line or wireless link and typically share the resources of a
single processor or server within a small geographic area.
The most common local area networking technologies are:
• Ethernet
• LocalTalk
• Token Ring
• FDDI
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4. LAN Technology contd..
Ethernet
The Ethernet protocol is by far the most widely used.
Ethernet uses an access method called CSMA/CD (Carrier
Sense Multiple Access/Collision Detection).
The Ethernet protocol allows for linear bus, star, or tree
topologies.
Data can be transmitted over twisted pair, coaxial, or fiber
optic cable at a speed of 10 Mbps.
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5. LAN Technology contd..
LocalTalk
LocalTalk is a network protocol that was developed by
Apple Computer Inc. for Macintosh computers.
The method used by LocalTalk is called CSMA/CA (Carrier
Sense Multiple Access with Collision Avoidance).
LocalTalk adapters and special twisted pair cables can be
used to connect a series of computers through the serial
port.
The LocalTalk protocol allows for linear bus, star, or tree
topologies using twisted pair cable. A primary disadvantage
of LocalTalk is speed. Its speed of transmission is only 230
Kbps.
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6. LAN Technology contd..
Token Ring
The Token Ring technology was developed by IBM in the
mid 1980s.
The access method used involves token-passing.
In Token Ring, the computers are so connected that the
signal travels around the network from one computer to
another in a logical ring.
Token Ring protocol requires a star-wired ring using twisted
pair or fiber optic cable. It can operate at transmission
speeds of 4 Mbps or 16 Mbps.
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7. Token Ring contd..
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8. LAN Technology contd..
FDDI
Fiber Distributed Data Interface (FDDI) is a network protocol
that is used primarily to interconnect two or more local area
networks, often over large distances.
The access method used by FDDI involves token-passing.
FDDI uses a dual ring physical topology.
A major advantage of FDDI is speed. It operates over fiber
optic cable at 100 Mbps.
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9. LAN Technology contd..
Summary of General LAN Technologies
LAN
Cable Speed Topology
Technology
Twisted Pair, Coaxial, Linear Bus, Star,
Ethernet 10 Mbps
Fiber Tree
Fast Ethernet Twisted Pair, Fiber 100 Mbps Star
LocalTalk Twisted Pair .23 Mbps Linear Bus or Star
4 Mbps - 16
Token Ring Twisted Pair Star-Wired Ring
Mbps
FDDI Fiber 100 Mbps Dual ring
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10. LAN Types
To understand a LAN we need to explore the manner in
which network attached resources are shared in a LAN. The
two prevailing types are:
• Peer-to-Peer
• Client/Server
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11. LAN Types contd..
Peer-to-Peer
Peer-to-peer access control allows users to share
resources and files located on their computers and to
access shared resources found on other computers.
In a peer-to-peer network, all computers are considered
equal.
Peer-to-peer networks are designed primarily for small to
medium local area networks.
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12. Peer-to-Peer contd..
Some operating systems, like AppleShare, Windows for
Workgroups and Windows 95/98 are specially featured for
peer-to-peer network access.
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13. LAN Types contd..
Client/Server
Client/server network operating systems allow the network
to centralize functions and applications in one or more
dedicated file servers.
Novell Netware and Windows NT Server are examples of
client/server network operating systems.
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14. LAN Types contd..
Advantages
• Centralized
• Scalability
• Flexibility
• Interoperability
• Accessibility
Disadvantages
• Expense
• Maintenance
• Dependence
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15. LAN Transmission Methods
LAN data transmissions fall into three classifications:
• Unicast: A single packet is sent from the source to a
destination on a network
• Multicast: A single data packet that is copied and sent
to a specific subset of nodes on the network.
• Broadcast: A single data packet that is copied and sent
to all nodes on the network.
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16. Topology
The physical topology of a network refers to the
configuration of cables, computers and other peripherals.
There are four principal topologies used in LANs.
• Bus Topology
• Ring Topology
• Star Topology
• Tree Topology
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17. Topology contd..
Bus Topology
Bus topology consists of a main run of cable with a
terminator at each end.
All nodes such as, file server, workstations and other
peripherals, are connected to the main cable.
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18. Topology contd..
Ring Topology
Ring topology consists of nodes arranged in a ring pattern.
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19. Topology contd..
Star Topology
Star topology is designed with each node (file server,
workstations and peripherals) connected directly to a central
Network HUB.
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20. Topology contd..
Tree Topology
Tree topology combines BUS and STAR topologies. It
consists of a group of star-configured workstations
connected to a Bus backbone cable.
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21. LAN Media-Access Methods
Media contention occurs when two or more network devices
have data to send at the same time.
Multiple devices cannot talk on the network simultaneously,
some type of method must be used to allow one device
access to the network media at a time. This is done in two
main ways:
• Carrier Sense Multiple Access Collision Detect
(CSMA/CD)
• Token Passing
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22. Cabling
Cable is the medium through which information usually
moves from one network device to another.
The type of cable chosen for a network is related to the
network's topology, protocol, and size.
There are several types of cable which are commonly used
with LANs. Some of them are as follows:
• Twisted-Pair Cable
• Coaxial Cable
• Fiber Optic Cable
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23. Cabling contd..
Twisted-Pair Cable
Twisted pair cabling comes in two varieties:
• Shielded Twisted-Pair Cable
• Unshielded Twisted-Pair Cable
Shielded Twisted-Pair (STP) Cable
Shielded twisted pair (STP) is suitable for environments with
electrical interference; however, the extra shielding can
make the cables quite bulky. Shielded twisted pair is often
used on networks using Token Ring topology.
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24. Twisted-Pair Cable contd..
Unshielded Twisted-Pair Cable
UTP cable has four pairs of wires inside the jacket. Each
pair is twisted with a different number of twists per inch to
help eliminate interference from adjacent pairs and other
electrical devices.
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25. Cabling contd..
Coaxial Cable
Coaxial cables consist of one or more cables in a protective
cover. It has a single copper conductor at its center. A
plastic layer provides insulation between the center
conductor and an outer metal shield.
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26. Coaxial Cable contd..
The two types of coaxial cabling are:
• Thick coaxial
• Thin coaxial
Coaxial Cable Connectors
The most common type of connector used with coaxial
cables is the Bayone-Neill-Concelman (BNC) connector.
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27. Cabling contd..
Fiber Optic Cable
Fiber optic cabling consists of a center glass core
surrounded by several layers of protective materials. Outer
insulating jacket is made of Teflon or PVC. Center (core) is
made of Glass or plastic fibers. A plastic coating is used to
cushion the fiber center.
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28. Cabling contd..
Ethernet Cable Summary
Specification Cable type Maximum length
10BaseT Unshielded Twisted Pair 100 meters
10Base2 Thin Coaxial 185 meters
10Base5 Thick Coaxial 500 meters
10BaseF Fiber Optic 2000 meters
100BaseT Unshielded Twisted Pair 100 meters
100BaseTX Unshielded Twisted Pair 220 meters
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29. Protocols
Internet Protocol (IP): A network protocol that specifies
the format of packets, also called datagrams, and the
addressing scheme.
Terminal Control Protocol (TCP): A primary protocol in
TCP/IP networks. TCP allows two "hosts" in a TCP/IP
network to establish a connection and exchange streams
of data.
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30. Ethernet Technology
Ethernet is the most widely installed local area network
(LAN) technology.
• Traditional Ethernet supports data transfers at the
rate of 10 Megabits per second (Mbps).
• Fast Ethernet extends traditional Ethernet
performance up to 100 Mbps.
• Gigabit Ethernet boasts the same order-of-magnitude
improvement over Fast Ethernet by offering speeds of
1000 Megabits (1 Gigabit).
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31. Ethernet Technology contd..
Details of Traditional Ethernet Technologies
Segment Length
Name Cable
(Max.)
10Base5 500m / 1640ft. RG-8 or RG-11 coaxial
10Base2 185m / 606ft. RG 58 A/U or RG 58 C/U coaxial
Category 3 or better unshielded
10Base-T 100m / 328ft.
twisted pair
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32. Ethernet Technology contd..
Fast Ethernet
Fast Ethernet technology matured and met its design
goals of:
• increasing the performance of traditional Ethernet
• avoiding the need to completely re-cable existing
Ethernet networks
Fast Ethernet comes in two major varieties:
• 100Base-T (using unshielded twisted pair cable)
• 100Base-FX (using fiber optic cable)
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33. Ethernet Technology contd..
Gigabit Ethernet
Gigabit Ethernet was first made to travel over optical and
copper cabling, but the 1000Base-T standard
successfully supports it as well. 1000Base-T uses
Category 5 cabling similar to 100 Mbps Ethernet,
although achieving gigabit speed requires the use of
additional wire pairs.
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34. Half-Duplex
Half-Duplex data transmission means that data can be
transmitted in both directions on a signal carrier, but not at
the same time.
Example: Walkie-talkie; push button to talk, one speaker at
a time.
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35. Full Duplex
Full-duplex data transmission means that data can be
transmitted in both directions on a signal carrier at the
same time. When switches are introduced, full-duplex
operation is possible.
Example: Telephone; both parties can speak and hear at
the same time.
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36. Ethernet Collisions
A collision is an event that happens on an Ethernet
network when two stations simultaneously "talk" on the
wire.
There are two different type of collisions namely:
• Early Ethernet Collisions
• Late Ethernet Collisions
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37. Ethernet Collisions contd..
Early Collisions
An early collision is any collision that occurs before 512
bits of the frame have been put onto the wire.
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38. Ethernet Collisions contd..
Late Collisions
A late collision is defined as any collision that occurs after
512 bits of the frame have been transmitted.
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39. Physical Frame Corruption
When troubleshooting your Ethernet network, the first thing
to look for is physical frame corruption.
The following are the four possible causes of physical
frame corruption in an Ethernet Network.
• Collisions: Caused by faulty hardware.
• Signal Reflections: Caused by un-terminated cables,
impedance mismatch and exceeding the maximum
allowable bend radius of the cable.
• Electrical Noise: Caused by nearby power grids,
fluorescent lighting, X-ray machines etc.
• Malfunctioning Hardware: Caused by gremlins,
helpful users, natural disasters etc.
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40. LAN Segmentation
When separate networks are needed or if a network has
reached its physical limitations, segmentation is used.
Segmenting a LAN can extend the network, reduce
congestion, isolate network problems, and improve
security.
The advantages of LAN segmentation are as follows:
• Extending the Network
• Reduce Congestion
• Isolate Network Problems
• Improve Security
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41. LAN Segmentation contd..
LAN Segmentation Using Bridges
The term bridging refers to a technology in which a device
(known as a bridge) connects two or more LAN segments.
A bridge transmits datagrams from one segment to their
destinations on other segments.
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42. LAN Segmentation contd..
LAN Segmentation Using Routers
Segments are interconnected by routers to enable
communication between LANs while blocking other types
of traffic.
LAN Segmentation Using Switches
Switches are data link layer devices that, like bridges,
enable multiple physical LAN segments to be
interconnected into a single larger network.
LAN switches can be used to segment networks into
logically defined virtual workgroups (VLANs).
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43. LAN Segmentation contd..
Benefits of Network Segmentation with
Bridges
Transparent bridges successfully isolate intrasegment
traffic, thereby reducing the traffic seen on each individual
segment. This usually improves network response times,
as seen by the user.
Benefits of Network Segmentation with
Routers
• Media Transition
• Broadcast Control
• Packet Filtering
• VLAN Communications
• Large Packets
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44. LAN Segmentation contd..
Benefits of Network Segmentation with
Switches
The benefits of network segmentation with switches are as
follows:
• Allow multiple data streams to pass simultaneously.
• Provides dedicated, collision-free communication
between network devices, with support for multiple
simultaneous conversations.
• Reduce collisions on network segments.
• Provide excellent performance for individual users by
allocating dedicated bandwidth to each switch port.
• Deliver dedicated bandwidth to users.
• Group individual ports into logical switched workgroups
called VLANs.
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