The document discusses different network topologies including token ring, linear bus, star, and tree topologies. It also covers transmission media such as twisted pair, coaxial cable, and optical fiber. Key aspects summarized include that token ring networks use a ring topology with a token passing protocol to ensure only one device can transmit at a time, while star topologies connect devices through a central hub to isolate devices. Linear bus topologies use a main cable to connect all devices.

2. Overview
 Network Topologies
 Transmission Media (Cable Types)
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3. Network Topologies
 Token Ring
 Linear Bus
 Star
 Tree (Expanded Star)
 Considerations When Choosing a Topology
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4. Token Ring
• Uses a ring topology, where
devices in the network are
logically arranged in a closed
ring/circle.
• It also uses a token passing
protocol, so that a machine
can only use the network
when it has control of the
Token.
• This ensures that there are no
collisions because only one
machine can use the network
at any given time.
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5.  It is considered to be an active topology, as computers
in the ring re-transmit the packet they receive to the
next computer in the ring.
 The token is a special packet of data, if a computer
wants to send data onto the network, it has to wait
until it has possession of the token, else it passes it on
to the next computer.
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6.  Upon start up, the machine with the highest MAC address
is chosen as the 'Active Monitor‘, and all other machines
become 'Standby Monitors'.
 Active Monitors are in charge of monitoring the network
and performing “Ring Polling”, by which other computers
find their “Nearest Active Upstream Neighbor (NAUN)”.
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7.  Advantages
 Very orderly network where every device has access to the token and
the opportunity to transmit.
 Performs better than a star topology under heavy network load.
 Can create much larger network using Token Ring.
 Does not require network server to manage the connectivity
between the computers.
 Disadvantages
 One malfunctioning workstation or bad port in the MAU can create
problems for the entire network.
 Moves, adds and changes of devices can affect the network.
 Network adapter cards and MAU's are much more expensive than
Ethernet cards and hubs.
 Much slower than an Ethernet network under normal load.
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8. Linear Bus
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9.  A linear bus topology consists of a main run of cable with a
terminator at each end. All nodes (file server, workstations,
and peripherals) are connected to the linear cable.
 A signal from the source travels in both directions to all
machines connected on the bus cable until it finds the
intended recipient. If the machine address does not match
the intended address for the data, the machine ignores the
data.
 Uses CSMA/CD, or CSMA/CA to manage and minimize
collisions.
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10.  Linear bus
 The type of network topology in which all of the nodes of the network
are connected to a common transmission medium which has exactly
two endpoints (also commonly referred to as the backbone, or trunk) –
all data transmitted between nodes in the network is sent over the
backbone and can be received by all nodes in the network
simultaneously.
 Distributed bus
 The type of network topology in which all of the nodes of the network
are connected to a common transmission medium which has more
than two endpoints (that are created by adding branches to the main
section of the transmission medium).
 Notes:
 The linear bus topology is sometimes considered to be a special case of the
distributed bus topology – i.e., a distributed bus with no branching segments.
 The physical distributed bus topology is sometimes incorrectly referred to as a
physical tree topology.
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11.  Advantages of a Linear Bus Topology
 Easy to connect a computer or peripheral to a linear bus.
 Requires less cable length than a star topology.
 Disadvantages of a Linear Bus Topology
 Entire network shuts down if there is a break in the main
cable.
 Terminators are required at both ends of the backbone cable.
 Difficult to identify the problem if the entire network shuts
down.
 Not meant to be used as a stand-alone solution in a large
building.
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12. Star Topology
 Each computer in a star topology is connected with its own
cable (typically twisted-pair cable) to a port on the hub or
some central component unit.
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13.  Star LANs also use the same type of wait-and-listen
strategy to access data or send data as characterized by the
bus topology.
 Advantages
 Better performance.
 Passing of Data Packet through unnecessary nodes is prevented by
this topology. This topology induces a huge overhead on the central
hub, however if the central hub has adequate capacity, then very
high network utilization by one device in the network does not affect
the other devices in the network.
 Isolation of devices.
 Each device is inherently isolated by the link that connects it to the
hub. This makes the isolation of the individual devices fairly
straightforward. This isolated nature also prevents any non-centralized
failure to affect the network.
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14.  Benefits from centralization.
 Easy to increase the capacity of the central hub, add
additional devices to the star (can scale the network very
easily). The central nature also allows the inspection traffic
through the network.
 Simplicity.
 The topology is easy to understand, establish, and navigate.
 Unobtrusive.
 Minimal effect on users.
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15.  Disadvantages.
 High dependence of the system on the functioning of
the central hub.
 Performance and scalability of the network also depend
on the capabilities of the hub.
 Number of connections in the star also depends on the
how many connections the hub can support.
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16. Tree Topology (Expanded Star)
 Tree topology is a combination of Bus and Star
topology.
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17.  It consists of groups of star-configured workstations connected to a
linear bus backbone cable.
 5-4-3 Rule
 Between any two nodes on the network there can only be a maximum
of 5 segments, connected through 4 repeaters/concentrators. In
addition, only 3 of the segments may be populated (trunk) segments if
they are made of coaxial cable.
 Advantages
 Point-to-point wiring for individual segments.
 Supported by several hardware and software venders.
 Disadvantages
 Overall length of each segment is limited by the type of cabling used.
 If the backbone line breaks, the entire segment goes down.
 More difficult to configure and wire than other topologies.
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18. Considerations When Choosing a
Topology
 Money.
 A linear bus network may be the least expensive way to install a
network; you do not have to purchase concentrators.
 Cable Length.
 The linear bus network uses shorter lengths of cable.
 Future growth.
 With a star topology, expanding a network is easily done by adding
another concentrator.
 Cable type.
 The most common cable in schools is unshielded twisted pair, which is
most often used with star topologies.
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19. Topology Summery
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20. Transmission Media
 Twisted Pair
 Coaxial Cable
 Optical fiber
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21. Twisted Pair
Applications
• Most common medium
• Telephone network
 Between house and local exchange (subscriber loop)
• Within buildings
To private branch exchange (PBX)
• For local area networks (LAN)
10Mbps or 100Mbps
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22. Pros
 Cheap
 Easy to work with
Cons
 Low data rate
 Short range
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23. • Shielded Twisted Pair (STP)
— Metal braid or sheathing that
reduces interference
— More expensive
— Harder to handle (thick, heavy)
• Unshielded Twisted Pair (UTP)
— Ordinary telephone wire
— Cheapest
— Easiest to install
— Suffers from external EM
interference
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24.  Cross-Over Cable
• Crossover cables have pairs of wires that crisscross. This
allows for two devices to communicate at the same time.
• Used to connect two like devices, like,
• Routers and computers.
• Switches and hubs.
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25. • Straight-Through Cable.
• Straight-through cables are primarily used for
connecting unlike devices.
• Between (Computers and Routers) and (Switches and Hubs).
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26. • Rollover Cable (Console cable).
• Rollover cables essentially have one end of the cable wired
exactly opposite from the other.
• Used to connect Computers and devices to a routers
console port.
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27. Category Maximum data rate Usual application
CAT 1 Less than 1 Mbps analog voice (plain old telephone service)
Integrated Services Digital Network Basic Rate
Interface in ISDN Doorbell wiring
CAT 2 4 Mbps Mainly used in the IBM Cabling System for token
ring networks
CAT 3 16 Mbps Voice and data on 10BASE-T Ethernet (certify
16Mhz signal)
CAT 4 20 Mbps Used in 16Mbps Token Ring
Otherwise not used much
CAT 5 100 Mbps 100 Mbps TPDDI
155 Mbps asynchronous transfer mode (certify
100 Mhz signal)
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28. Crimping Tools
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29. Coaxial Cable
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Applications
• Most versatile medium
• Television distribution
— Ariel to TV
— Cable TV
• Long distance telephone transmission
— Can carry 10,000 voice calls simultaneously
— Being replaced by fiber optic
• Short distance computer systems links
• Local area networks

30.  Two types of coaxial cable are used for networking
computers:
 Thicknet
 A heavy-gauge coaxial cable that is fairly inflexible and requires
special equipment (over and above a simple network card) to
connect the computer to the network backbone.
 Thinnet.
 Thinnet (RG-58 coaxial cable) was the cable of choice at one time because of
its relative ease of installation and its low cost.
 Thinnet LANs employ a bus topology, where a T-connector is attached to
each computer’s network card. The computers are then chained together
using appropriate lengths of cable. Thinnet installations require that each
end of the network be terminated, and terminators are placed on the
downside T-connector of the computers that reside on either end of the
network.
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31. Optical Fiber
 Optical fibers are based entirely on the principle of
total internal reflection.
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32.  Fiber Modes.
 Single Mode.
 Multi Mode.
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34. Overview
 5-4-3 rule
 In the Ethernet protocol, a signal sent out over the
collision domain must reach every part of the network
within a specified length of time.
 Thus comes the “IEEE Way”/5-4-3 rule, which states that
“In a given collision domain, only 5 segments, 4
repeaters, and 3 populated segments may exist.”.
 The populated segments are ‘user’ segments, and the
unpopulated ones are known as ‘link’.
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35.  The rule only applies to shared-access Ethernet
backbones. The rule does not apply to switched
Ethernet because each port on a switch constitutes a
separate collision domain.
 Point-to-point Network
 The simplest topology is a permanent link between
two endpoints.
 There are two types of such networks.
 Permanent
 Switched
 Circuit switched
 Packet switched
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36. The eight steps
 The most important part of troubleshooting any
problem is to divide the tasks of problem resolution
into a systematic process of elimination. Cisco has
broken this process into eight steps:
Define the problem.
 Gather detailed information.
 Consider probable cause for the failure.
 Devise a plan to solve the problem.
 Implement the plan.
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37.  Observe the results of the implementation.
 Repeat the process if the plan does not resolve the
problem.
 Document the changes made to solve the problem.
 In case of networks,
 Identify the topology.
 Identify any special features.
 Work from the bottom up.
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38. QUESTIONS
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