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1. Computer Networks
Lecture # 7
Course Title: Computer Networks
Instructor: Tahira Malik (Lecturer)
Email Address: tahira@uosahiwal.edu.pk
Department of Computer Science
Term (Semester): Fall 2020
1
2. Transmission Media
• The physical path through which computers send and receive
signals is called transmission media
• Transmission media is what actually carries a signal from one
point to another
• Anything that can carry information from a source to a
destination.
• Classes of Transmission Media
• Two classes of Transmission Media:
Guided Media
Unguided Media
3. Transmission Media
• Guided Media
Guided media are those media that uses a physical path or conductor to
transmit the signals from one device to another
A medium such as copper wiring is referred to as bounded (guided) media
because it holds electronic signals
Fiber optic cable is also said to be bounded media as it holds light waves
• Unguided Media
Unguided media or wireless communication transport electromagnetic
waves without a physical conductor or media that do not physically
constrain signals are considered to be unbounded media (unguided)
Instead signals are broadcast through air and are available to anyone who
has a receiver capable of receiving them
4. Guided Media
• All types of cables generally fall under the guided media
• Cables have a central conductor that consists of a wire or fiber
surrounded by a plastic jacket
• It normally transmits signals using the lower end of the
electromagnetic spectrum, such as simple electricity and
sometimes radio waves
• Three types of cable media are
Twisted Pair Cable
Coaxial Cable
Fiber-Optic Cable
5. Twisted Pair Cable
The construction of TP is simple
Two insulated wires are twisted around one another
This is to help offset electrical disturbances which can affect TP
cable such as radio frequency interference (RFI) and
electromagnetic interference (EMI)
These "pairs" of wires are then bundled together and coated to
form a cable
• Twisted pair comes in two forms:
Unshielded Twisted Pair (UTP) cable
Shielded Twisted Pair (STP) cable
6. Unshielded Twisted Pair Cable
• UTP cable consists of a number of twisted pairs with a simple
casing (no shielding)
• It is commonly used in telephone systems and is easy to install
• Structure of the cable:
7. Unshielded Twisted Pair Cable
Characteristics:
• Cost: lowest (except cat5)
• Installation: easy
• Bandwidth Capacity: 1 – 500 Mbps (typically 10 Mbps)
• Node Capacity per Segment: 2
• Attenuation: 100 meters (high)
• EMI: More vulnerable to EMI and eavesdropping
• Connectors used with UTP included RJ-11 and RJ-45 modular
connectors, RJ-11 connectors accommodate 4 wires or 2 twisted
pairs, while RJ-45 houses 8 wires or 4 twisted pairs
8. Shielded Twisted Pair
• STP has a shield usually aluminum/polyester (foil or mesh)
between the outer jacket or casing and the wires
• This special layer is designed to help offset interference
problems
• It was the first TP cable used for LANs
• Structure of the cable:
9. Shielded Twisted Pair
• Characteristics:
• Cost: Moderate
• Installation: Fairly easy
• Bandwidth Capacity: 1 – 155 Mbps (typically 16 Mbps)
• Node Capacity per Segment: 2
• Attenuation: 100 meters (high)
• EMI: Less vulnerable to EMI and eavesdropping than UTP
• TP cabling has been around a while and is a tried and true medium.
It hasn't been able to support high speed data transmissions until
recently. New development is focusing on achieving 100 Mbps
throughput on UTP.
10. Coaxial Cable
• Coaxial cable or just "coax" has been perfect for applications
requiring stable transmission characteristics over fairly long
distances
• Construction-wise coax is a little more complex then TP
• It is typically composed of a copper conductor that serves as the
"core" of the cable
• This conductor is covered by a piece of insulating plastic, which is
covered by a foam or wire mesh serving as both a shield and second
conductor
• This second conductor is then coated by PVC (plastic) or other
coating
• The conductor within a conductor sharing a single axis is how the
name of the cable is derived
12. Coaxial Cable
• Characteristics:
• Cost: Moderate
• Installation: Simple
• Bandwidth Capacity: 10 Mbps
• Node Capacity per Segment: 30 - 100
• Attenuation: Few kilometers (low)
• EMI: Less vulnerable to EMI and eavesdropping
13. Fiber Optic Cable
• The crucial element for fiber is glass that makes up the core of the
cabling
• The glass core of a fiber optic cable is surrounded by and bound to
a glass tube called "cladding“
• Cladding adds strength to the cable while disallowing any stray light
wave from leaving the central core
• This cladding is then surrounded by a plastic or PVC outer jacket
which provides additional strength and protection for the innards
• Fiber optic is lightweight and is utilized often with LEDs (Light-
Emitting Diodes) and ILDs (Injection Laser Diodes)
• Fiber optic cable transmits light signals rather than electrical signals
• One optical fiber is the same diameter as a human hair
• It can only be banded at a specific angle
15. Fiber Optic Cable
• Optical fibers may be multimode or single mode
• Single mode fibers allow a single light path and are typically
used with laser signaling (ILDs)
• They allow greater bandwidth but are more expensive
• Multimode fibers use multiple paths
• The physical characteristic of the multimode fiber makes all
parts of the signal arrive at the same time, appearing to the
receiver as though they were one pulse
• They use LEDs and are less expensive
16. Fiber Optic Cable
• Characteristics:
• Cost: Highest
• Installation: Difficult
• Bandwidth Capacity: 2 Gbps (typically 100 Mbps)
• Node Capacity per Segment: 2
• Attenuation: Tens of kilometers (lowest)
• EMI: Not effected by EMI and eavesdropping
17. Unguided Media
↗ For unguided media, transmission and reception are achieved by means
of an Antenna
↗ For transmission, the antenna radiates electromagnetic energy into the
medium (usually air), and for reception, the antenna picks up
electromagnetic waves from the surrounding medium
There are basically two types of configurations for wireless transmission;
directional and omnidirectional
↗ For the directional configuration, the transmitting antenna puts out a
focused electromagnetic beam; the transmitting and receiving antennas
must therefore be carefully aligned
↗ In the omnidirectional case, the transmitted signal spreads out in all
directions and can be received by many antennas. In general, the higher
the frequency of a signal, the more it is possible to focus it into a
directional beam
18. Unguided Media
Three general ranges of frequencies are of interest in our
discussion of wireless
transmission.
1. Microwave
2. Broadcast Radio
3. Infrared
19. Unguided Media
Microwave
↗ Frequencies in the range of about 2 GHz to 40 GHz are referred to as
microwave frequencies
↗ At these frequencies, highly directional beams are possible, and
microwave is quite suitable for point-to-point transmission
↗ Microwave is also used for satellite communications
↗ Microwave is commonly used for both voice and television transmission
↗ A business can establish a microwave link to a long distance
telecommunications facility in the same city, bypassing the local
telephone company
↗ The higher the frequency used, the higher the potential bandwidth and
therefore the higher the potential data rate
20. Unguided Media
Broadcast Radio
↗ Frequencies in the range of 30 MHz to 1 GHz are suitable for
omnidirectional applications and are referred to as the broadcast radio
range
↗ This range is used for a number of data-networking applications
↗ The principal difference between broadcast radio and microwave is that
the former is omnidirectional and the latter is directional
↗ Thus, broadcast radio does not require dish-shaped antennas, and the
antennas need not be rigidly mounted to a precise alignment
↗ Transmission is limited to line of sight, and distant transmitters will not
interfere with each other due to reflection from the atmosphere
21. Unguided Media
Infrared
↗ Another important frequency range, for local applications, is the infrared
portion spectrum
↗ This covers, roughly, from 3 X 1011 to 2 X 1014 Hz
↗ Infrared is useful to local point-to-point and multipoint applications
within confined areas, such as a single room
↗ One important difference between infrared and microwave transmission
is that the former does not penetrate walls
↗ Transceivers must be in line of sight of each other
↗ Thus, the security and interference problems encountered in microwave
systems are not present
↗ Furthermore, there is no frequency allocation issue with infrared,
because no licensing is required
22. UTP Cable Installation
EIA/TIA 568A and 568B (standards)
↗ The T-568A standard is supposed to be used in new network installations
↗ Most off-the-shelf Ethernet cables are still of the T-568B standard; however, it
makes absolutely no functional difference in which you choose
23. UTP Cable Installation
UTP Cable Configurations
Straight-Through Cable:
Straight-through means that the color of wire on Pin 1 on one
end of the cable is the same as that of Pin 1 on the other end
Pin 2 is the same as Pin 2, and so on
The cable is wired to either EIA/TIA T568B or T568A
standards, which determines what color wire is on each pin
24. UTP Cable Installation
UTP Cable Configurations
Crossover Cable:
A crossover cable means that the second and third pairs on one end of the
cable will be reversed on the other end
The pin-outs are T568A on one end and T568B on the other end
If the crossover cable is used between switches, it's considered to be part
of the "vertical" cabling. Vertical cabling is also called backbone cabling
A crossover cable can be used as a backbone cable to connect two or more
switches in a LAN, or to connect two isolated hosts to create a mini-LAN
This will allow the connection of two hosts or a server and a host without
the need for a hub between them
26. UTP Cable Installation
UTP Cable Configurations
Rollover Cable:
A rollover cable can be used to connect a host or dumb terminal to the
console port on the back of a router or switch
Cable is called a rollover because the pins on one end are all reversed on
the other end as though one end of the cable was rotated or rolled over
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
Baseband :
It utilizes the entire media bandwidth for a single channel. It is low cast, simpler to implement. Used mostly on LAN. Ethernet or CSMA / CD protocols are used. Token Ring / Token Bus protocols of ring and bus topologies. With the help of these media access protocols the whole bandwidth is shared. It has limitations in capacity( data carrying capacity ) and distance. Baseband is commonly used for digital signaling, although it can also be used for analog signals.
Broadband :
High speed gigabit connectivity. In broadband the entire media bandwidth can be divided into multiple channels. Since each channel can carry a different analog signal, there is simultaneous communication over a single line. It has FDM. They are faster than Baseband. It does not allow broadcasting.
