HW for Chapter 3

2.1
Exercises:
38, 45, 47, 48
MIDTERM 1 – WEEK OF
MARCH 8th
Ch.1, Ch.2, 3.1 & 3.6, Ch.7, 8.18.3
McGraw-Hill
2
©The McGraw-Hill Companies, Inc., 2000
Chapter 7
Transmission Media
7.3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Transmission medium and physical layer
A transmission media defined as anything that carry
information between a source to a destination
- Located below the physical layer and are directly
controlled by the physical layer
7.4
Classes of Transmission Media
7.5
7-1 GUIDED MEDIA
Guided media, which are those that provide a conduit
from one device to another, include twisted-pair cable,
coaxial cable, and fiber-optic cable.
Twisted –pair cables and coaxial cable:
use metallic (copper) conductors that transport
signals in the form of electric current
Optical fiber : transport signals in the form of
the light
7.6
Twisted-pair cable
•One of the wire used to carry signal and the other as a
ground. The receiver uses the difference between the
two.
•If the two wires are parallel, the effect of interference
noise and crosstalk is big
•Twisting the pair of wire balance the effect of unwanted
signal and reduce it.
The number of twists per unit of length
effects on the quality of the cable
7.7
Applications of Twisted pair
Used in
1.telephone lines to provide voice and data
channels (local loop)
2.The DSL lines that are used by the telephone
companies to provide high-data-rate connections
3.Local area networks, such as 10-base-Tand
100base-T
7.8
Figure 7.6 UTP performance
7.9
Coaxial cable
Coax cable carries signals of higher frequency ranges
than those in Twisted pair cable because the two media
are constructed quite differently.
The outer conductor serves both as a shield against
noise and as second conductor, which complete the
circuit
7.10
Applications of coaxial cable
1.Analog telephone network where a single cable could
carry 10,000 voice signals. Later it was used in Digital
telephone networks where cable can carry 600Mbps
2.Cable TV network: hybrid network use coaxial cable
only at the network boundaries , near the consumer.
Cable TV use RG-59
3.Traditional Ethernet LANs.
10-base-2 or “Thin Ethernet”, uses RG-58 coax cable
to transmit data at 10 Mbps with a range of 185m.
10-base-5,or “Thick Ethernet”, uses RG-11 to
transmit 10 Mbps with rang of 500 m
7.11
Figure 7.9 Coaxial cable performance
7.12
Fiber Optic Cable
Is made of glass or plastic and transmit signals in the form of light.
Light travels in a straight line as long as it is moving through a single uniform
substance. If a ray of light traveling through one substance enters another
substance of different density , the ray change direction as shown:
I: angle of incidence: the angle the ray makes with line
perpendicular to the interface between the two substances
Critical angle: property of substance, its value differs from
one substance to another
7.13
Optical fiber
Fiber Optical : uses reflection to guide light
through a channel. A glass or plastic core is
surrounded by a cladding of less dense glass or
plastic
7.14
Applications for Fiber Optic cable
Used in :
1.Cable TV network: hybrid network use a
combination of optical fiber and coax cable. Optical
provides the backbone while coaxial cable provide
the connation to the user.
2.Local area networks such as 100base-FX(fast
Ethernet) and 1000base-XLANs.
3.Backbone networks because its wide bandwidth
7.15
Advantages of fiber-optical
1.Higher Bandwidth
2.Less signal attenuation it needs repeater every
50km, where twisted and coaxial need it every 5km.
3.Immunity to electromagnetic interference (noise)
4.Resistance to corrosive materials. Glass is more
resistance to corrosive material than copper
5.Light weight. Fiber cables are much lighter than
copper cables
6.Greater immunity to tapping: copper cables create
antenna effects that can easily be tapped
7.16
Disadvantages of fiber-optical
1.Installation and maintenance. It’s a new technology.
Its installation and maintenance require expertise that
is not yet available every where.
2.Unidirectional light propagation. If we need
bidirectional , two fibers are needed.
3.Cost. The cable and the interfaces are more
expensive than those of other guided media. If the
demand of BW is not high , often use of optical fiber
can not be justified
7.17
HW for Chapter 7

Review Questions:
1, 2, 3, 4, 8
2.18
Ch. 8: Switching & Datagram
Networks
McGraw-Hill
7.19
©The McGraw-Hill Companies, Inc., 2000
Building large networks


A network is a set of connected devices.
When ever we have multiple devices, we
have the problem of how to connect them!


7.20
Point-to-point (mesh or star topology):
impossible for large networks.
Multipoint (bus topology): does not work for
large network since the distances between
devices and the total number of devices
increase beyond the capacity of the media
and equipments.
Switching is the solution


7.21
A switched network consists of a series of
interlinked nodes, called switches.
Switches are devices capable of making
temporary connections between any two
or more devices connected to the switch.
Figure 8.1 Switched network
8.22
Figure 8.2 Taxonomy of switched networks
8.23
8-1 CIRCUIT-SWITCHED NETWORKS
A circuit-switched network consists of a set of switches
connected by physical links. A connection between two
stations is a dedicated path made of one or more links.
However, each connection uses only one dedicated
channel on each link. Each link is normally divided
into n channels by using FDM or TDM.
Topics discussed in this section:
Three Phases
Efficiency
Delay
Circuit-Switched Technology in Telephone Networks
8.24
Note
A circuit-switched network is made of a
set of switches connected by physical
links, in which each link is
divided into n channels.
8.25
Figure 8.3 A trivial circuit-switched network
8.26
Note
In circuit switching, the resources need
to be reserved during the setup phase;
the resources remain dedicated for the
entire duration of data transfer until the
teardown phase.
8.27
Note
Switching at the physical layer in the
traditional telephone network uses
the circuit-switching approach.
8.28
8-2 DATAGRAM NETWORKS
In data communications, we need to send messages
from one end system to another. If the message is
going to pass through a packet-switched network, it
needs to be divided into packets of fixed or variable
size. The size of the packet is determined by the
network and the governing protocol.
Topics discussed in this section:
Routing Table
Efficiency
Delay
Datagram Networks in the Internet
8.29
Note
In a packet-switched network, there
is no resource reservation;
resources are allocated on demand.
8.30
Figure 8.7 A datagram network with four switches (routers)
8.31
Figure 8.8 Routing table in a datagram network
8.32
Note
A switch in a datagram network uses a
routing table that is based on the
destination address.
8.33
Note
The destination address in the header of
a packet in a datagram network
remains the same during the entire
journey of the packet.
8.34
Figure 8.9 Delay in a datagram network
8.35
Note
Switching in the Internet is done by
using the datagram approach
to packet switching at
the network layer.
8.36
8-3 VIRTUAL-CIRCUIT NETWORKS
A virtual-circuit network is a cross between a circuitswitched network and a datagram network. It has
some characteristics of both.
Topics discussed in this section:
Addressing
Three Phases
Efficiency
Delay
Circuit-Switched Technology in WANs
8.37
Figure 8.10 Virtual-circuit network
8.38
Figure 8.11 Virtual-circuit identifier
8.39
Figure 8.12 Switch and tables in a virtual-circuit network
8.40
Figure 8.13 Source-to-destination data transfer in a virtual-circuit network
8.41
Figure 8.14 Setup request in a virtual-circuit network
8.42
Figure 8.15 Setup acknowledgment in a virtual-circuit network
8.43
Note
In virtual-circuit switching, all packets
belonging to the same source and
destination travel the same path;
but the packets may arrive at the
destination with different delays
if resource allocation is on demand.
8.44
Figure 8.16 Delay in a virtual-circuit network
8.45
Note
Switching at the data link layer in a
switched WAN is normally
implemented by using
virtual-circuit techniques.
8.46
HW for Chapter 2

Review Questions:
1, 2, 3, 4, 5, 6

2.47
Exercises:
11 (a,c), 14, 16, 17, 18