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Dr. Arshad Ali
[email protected]
Mobile # 03008798543
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MSCS & PhD level course
3 credit hour course
15-16 weeks/lecture
Assignments
Quizzes
Presentations
Term project
Mid term Exam
Final Exam
Party to Comprehensive Exam (for PhDs)
Dr. Arshad Ali
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Fundamentals of Computer Communication & Networks
Fundamental aspects of wireless networks
Overview of wireless technologies
The IEEE 802.11 wireless standards
Probability
Queuing theory and simulations
Mobile radio propagation
Multiple division techniques,
Mobility support
Channel allocation and coding
Dr. Arshad Ali
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Mobile ad-hoc networks
Green cellular networks
Delay Tolerant Networks
Cognitive Radios
Wireless sensor networks
Routing and Transport protocols
Emerging research issues in WNs with emphasis on current and nextgeneration wireless networks
Industry trends and discuss some innovative ideas that have recently been
developed.
Some of the course material will be drawn from research papers, industry
white papers and Internet RFCs.
Dr. Arshad Ali
1: Wireless Communications and Networks, 2nd Edition
Author: William Stallings
2: Introduction to Wireless and Mobile Systems, Third Edition
Author: Qing-An Zeng
Dr. Arshad Ali
Dr. Arshad Ali
Acknowledgment
Dr. Arshad Ali
Data Communication
“Data Communication is the exchange of information from
one entity to the other using a transmission medium”.
Data refers to information presented in whatever form is
agreed upon by the parties creating and using the data
For Data Communication to occur
The communicating devices must be a part of a
communication system made up of some specific kind of
hardware (Physical equipment) and software (Programs),
This type of a system is known as a “Data Communication
System”
Characteristics of
Data Communication System
 The effectiveness of a data communications system depends on
Delivery of data to the correct destination
Accuracy: data must be delivered accurately (as it is)
 Timeliness: data must be delivered on time
Real time transmission of audio and video data
A data communication system must transmit data to the
correct destination in an accurate and timely manner
Source :http://howdoesinternetwork.com/2013/jitter/jitter-2
Components Of
Data Communication System
Data Representation
Forms of Information
 Text
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Numbers
Images
Audio
Video
Data Flow
 Simplex
 Half Duplex
 Full Duplex
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To understand hard problem the computer networks need
to solve
the design strategies which have proven valuable for
solving difficult problems
Why should you bother learning these fundamentals as
opposed to learning about how the internet works today?
◦ WiFi (a new technology known to many among us), we
might talk about it a lot
◦ But might not know much about satellite networks
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Apply to all computer networks
 Many of the networking fundamentals also apply to satellite networks
 So, a little extra learning enables to transfer knowledge to other kinds
of networks
Change / reinvention (most important reason)
 The internet is not static (constantly being re-invented)
 understanding the fundamentals gives long term knowledge
◦ helps to understand the internet of the future which is continuing to
change and evolve
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Today’s internet is different from yesterday’s
◦ Tomorrow’s will also be different
◦ But fundamentals remain the same
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What is a network?
 A network is a set of devices (often referred to as nodes) and
connected by communication transmission channels (links) that
allow people to communicate over distances, large and small
 A node can be a computer, printer, or any other device capable
of sending and/or receiving data generated by other nodes on the
network.
 A link can be a cable, air, optical fiber, or any medium which
can transport a signal carrying information
The Internet and telephone networks span the globe
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Computer Networks: a collection of autonomous
computers interconnected by a single technology
Two computers are said to be interconnected if they are
able to exchange information
Networks are usually connected together to make larger
networks (network of networks)
Internet: the most well-known example of a network of
networks
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How to achieve connectivity between computers,
networks and people?
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Variety of transmission methods
Wired transmission
 Coaxial cable, twisted pair wiring, fiber optics
Wireless transmission
Microwave, satellites, cellular systems, ad hoc networks, wireless
sensor networks
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Network Criteria
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Performance
◦ Measured in many ways
 Transmit time: amount of time required for a message to
travel from one device to another
 Response time: elapsed time between an inquiry and
response
◦ Depends on a number of factors
 Number of users
 Type of transmission medium
 Hardware capabilities and efficiency of the software
◦ Evaluated in terms of delay and throughput
 We need more throughput and less delay
Network Criteria
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Reliability
◦ Measured by the failure rate of network components,
availability (the time taken by a link to recover from
failure), and network’s robustness (tolerance to errors)
◦ Measured in terms of availability/robustness
Security
◦ Data protection against corruption/loss of data due to:
 Errors
 Malicious users
Physical Structures
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Type of Connection
◦ A network is two or more devices connected through
links.
◦ A link is a communications pathway that transfers data
from one device to another.
◦ Imagine any link as a line drawn between two points
(For visualization purposes ).
◦ For communication to occur, two devices must be
connected in some way to the same link at the same
time.
Physical Structures: Types of connections
For communication to occur, two devices must be connected in some way to
the same link at the same time
Two possible types of connections
Point to Point: single transmitter and receiver
Provides dedicated link between two devices
Multipoint: multiple recipients of single transmission
More than two specific devices share a single link
Spatially shared: if several can use the link simultaneously
Temporally shared: If users use the link in turns (timeshared)
Physical Structures
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Physical Topology refers to the way in which a network is laid out
physically
◦ Two or more devices connect to a link and two or more links
form a topology
◦ Topology is geometric representation of the relationship of all
the links and nodes (devices connected to one another through
links)
Categories of Networks
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Distance: Important classification metric
THE INTERNET
An internet is two or more networks that can communicate
with each other . The most notable internet is called
Internet (composed of thousands of interconnected
networks)
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Principals
◦ Create a layer where a different abstraction is needed
◦ Each layer should perform a well-defined function
◦ The function of each layer should be chosen
 With target for standardization
◦ Minimize information flow across layer boundaries
◦ Number of layers
 Large: distinct functions are not in the same layer
 Small : architecture does not become complex
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Consists of 7 separate but related layers, each of which
defines a part of the process of moving information across a
network
Seven layers of the OSI model
An exchange using the OSI model
Header: An information structure that precedes/leads and
identifies the information that follows, such as a block of
bytes in communication
Trailer: An information typically occupying several bytes,
at the tail end of a block of transmitted data and often
containing a checksum or other error-checking data useful
for confirming the accuracy and status of the transmission
FUNCTIONS OF LAYERS IN THE OSI MODEL
The physical layer is responsible for movements of
individual bits from one hop (node) to the next.
Concerned with Physical characteristics of interfaces
and medium; Representation of bits; data rate;
physical topology
FUNCTIONS OF LAYERS IN THE OSI MODEL
The data link layer is responsible for moving
frames from one hop (node) to the next.
Error control (masking the real errors from the
network layer);How to keep a fast transmitter from
drowning a slow receiver in data (flow control); how
to control access to the shared channel (MAC)
FUNCTIONS OF LAYERS IN THE OSI MODEL
The network layer is responsible for the delivery of
individual packets from the source host to the
destination host. It controls the operations of the subnet
How packets are routed from source to destination;
congestion control (too many packets at subnet at the
same time can form bottlenecks); QoS issues(delay, transit
time, jitter); how to allow heterogeneous networks to be
interconnected (due to different addressing used in
Source-to-destination delivery
FUNCTIONS OF LAYERS IN THE OSI MODEL
The transport layer is responsible for the delivery
of a message from one process to another; true
end-to-end layer
What type of services to be provided to sessions
layer and network users; error free point to point
channel for delivering the messages in the sent
order; message broadcast to multiple destinations;
Reliable process-to-process
delivery of a message
FUNCTIONS OF LAYERS IN THE OSI MODEL
The session layer is responsible for
dialog control: keeping track of whose turn it is to transmit
token management: preventing two parties from the same critical
operation simultaneously, and
Synchronization: checkpointing long transmissions to allow them to
pick up from where they left off in the event of a crash and subsequent
recovery
FUNCTIONS OF LAYERS IN THE OSI MODEL
The presentation layer is concerned with syntax and
semantics of information transmitted (how
information is formatted); responsible for
translation, compression, and encryption
FUNCTIONS OF LAYERS IN THE OSI MODEL
The application layer is responsible for providing
services to the user; contains protocols needed by
users like HTTP (basis for WWW); other applications
protocols are used for file transfer, mail and network
news
Summary of layers
TCP/IP PROTOCOL SUITE
The layers in the TCP/IP protocol suite do not exactly
match those in the OSI model. The original TCP/IP
protocol suite was defined as having four layers: host-tonetwork, internet, transport, and application. However,
when TCP/IP is compared to OSI, we can say that the
TCP/IP protocol suite is made of five layers: physical,
data link, network, transport, and application.
TCP/IP is a protocol suit used in the Internet today
TCP/IP model with some protocols to be studied
ADDRESSING
Any communication that involves two parties needs two addresses:
source address and destination address
Four levels of addresses are used in an internet employing the
TCP/IP protocols: physical, logical, port, and specific.
No address required at physical layer as the unit of data
exchange is a bit which does not definitely cannot have any
address
Relationship of layers and addresses in TCP/IP
ADDRESSING
Physical Address (also known as the link address)
 is the address of a node as defined by its LAN or WAN
is included in the frame used by the data link layer
is the lowest-level address
The physical addresses have authority over the network (LAN or
WAN)
The size and format of these addresses vary depending on the
network. For example, Ethernet uses a 6-byte (48-bit) physical
address that is imprinted on the network interface card (NIC).
Example 1
a node with physical address 10 sends a frame to a node with
physical address 87. The two nodes are connected by a link (bus
topology LAN). As the figure shows, the computer with physical
address 10 is the sender, and the computer with physical address 87
is the receiver.
Example 2
Most local-area networks such as Ethernet a 48-bit (6byte) physical address written as 12 hexadecimal digits;
every byte (2 hexadecimal digits) is separated by a colon,
as shown below:
07:01:02:01:2C:4B
A 6-byte (12 hexadecimal digits) physical address.
ADDRESSING
Logical Address
 Logical addresses are necessary for universal communications that
are independent of underlying physical networks
Physical addresses are not adequate in an internetwork
environment where different networks can have different address
formats.
A universal addressing system is needed in which each host can be
identified uniquely, regardless of the underlying physical network.
The logical addresses are designed for this purpose.
A logical address in the Internet is currently a 32-bit address that can
uniquely define a host connected to the Internet
Example: IP address
Figure shows a part of an
internet with two routers
connecting three LANs.
Each device (computer or
router) has a pair of addresses
(logical and physical) for each
connection.
Here, each computer is
connected to only one link and
therefore has only one pair of
addresses.
Each router, however, is
connected to three networks
(only two are shown in the
figure).
So each router has three pairs
of addresses, one for each
connection.
ADDRESSING
Port Address:
There are many application running on the computer.
Each application run with a port no.(logically) on the
computer.
This port no. for application is decided by the Karnal of
the OS.
This port no. is called port address.
Example: Port Address
Figure shows two computers
communicating via the
Internet.
The
sending
computer is running three
processes at this time with
port addresses a, b, and c.
The receiving computer is
running two processes at this
time with port addresses j
and k. Process a in the
sending computer needs to
communicate with process j
in the receiving computer.
Note that although physical
addresses change from hop
to hop, logical and port
addresses remain the same
from
the
source
to
Example: Port Address
A port address is a 16-bit address represented by one
decimal number as shown.
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A 16-bit port address represented
as one single number
ADDRESSING
Specific Address:
Some applications have user-friendly addresses that are designed for
that specific address.
Examples: e-mail address (for example, [email protected]) and the
Universal Resource Locator (URL) (for example, www.mhhe.com).
The first defines the recipient of an e-mail; the second is used to find
a document on the World Wide Web
These addresses, however, get changed to the corresponding port and
logical addresses by the sending computer
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Capacity of transmission medium usually exceeds
capacity required for transmission of a single signal
If the bandwidth of a link is greater than the bandwidth
needs of the devices connected to it, the bandwidth is
wasted
◦ So a medium linking two devices can be shared whenever the
bandwidth of the medium is greater than the bandwidth needs of
the devices
Multiplexing allows to make more efficient use of transmission
medium by carrying multiple signals simultaneously on a single
medium.
So Multiplexing is a set of techniques that allows the
simultaneous transmission of multiple signals across a single
data link
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Multiplexer (MUX)
◦ Combines multiple streams into a single stream (many to
one) and transmits over higher capacity data link
De-multiplexer (DEMUX)
◦ Separates the stream back into its component transmission
(one to many) and directs them to their correct lines.
Channel refers to the portion of a link that carries a transmission between
a given pair of lines. One link can have many (n) channels
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Frequency-Division Multiplexing(FDM),
Wavelength-Division Multiplexing (WDM)
Time-Division Multiplexing(TDM)
Code Division Multiplexing (CDM)
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Switching Strategies
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Circuit Switched Networks
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Packet Switched Networks
 Datagram approach
 Virtual circuit approach
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A virtual-circuit network
◦ normally implemented in the data link layer
circuit-switched network
◦ implemented in the physical layer
A datagram network
◦ Implemented in the network layer
Network Layer:
Logical (IP) Addressing
Protocols which route data from a node or hop
to another hop between two end hosts in a
network are called network-layer protocols.
In the Internet, the only currently available
network-layer protocol is IP
IPv4 ADDRESSES
An IPv4 address is a 32-bit address that uniquely and universally
defines the connection of a device (for example, a computer or a
router) to the Internet.
Finding the classes in binary and dotted-decimal notation
In classful addressing, the address space is divided into five classes:
A, B, C, D, and E
Number of blocks and block size in classful IPv4 addressing
Netid and Hostid
Network addresses cannot be all 0s
Hostid: Cannot be all 0s
If host portion is all 0s, represents a network address.
Hostid: Cannot be all 1s
If host portion is all 1s, represents broadcast address.
1
2
Router
124.x.y.z
3
Router
192.121.73.z
131.107.y.z
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1
124.0.0.27
2
124.0.0.1
3
192.121.73.
131.107.0.27
2
124.0.0.28
Router
Router
192.121.73.
131.107.0.1
131.107.0.28
1
124.x.y.z
124.0.0.29
192.121.73.z
131.107.0.z
131.107.0.29
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Subnet and Subnetting
A logical, visible subdivision of an IP network is called
subnet or subnetwork.
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It is created by dividing the host identifier
Subnetting is the practice of dividing a network into two
or more networks.
In subnetting, a class A or class B block is divided into
several subnets (each subnet with larger prefix length than
the original network).
For example, divide the class A into four subnets, then
each subnet will have prefix length as 10 (take two bits
from host id part in order to obtain subnets).
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Classless Addressing
• How to find the prefix length if an address is given?
• As prefix length is not inherent in the address
• Need to separately give the length of the prefix
• So, Prefix length is added to the address, separated by
a slash
• The notation is informally referred to as slash
notation and formally as classless interdomain
routing or CIDR
Format of classless addressing address
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Example: An organization is granted a block of addresses starting
with 17.12.14.0/26 (64 addresses). The organization needs to have
three subblocks of addresses to use in its three subnets: one subblock
of 32 addresses, and two subblocks of 16 addresees each.
Design the subblocks and find out how many addresses are still
available after these allocations.
Configuration and addresses in a subnetted network
Example (CIDR)
Example: An ISP is granted a block of addresses starting
with 190.100.0.0/16 (65,536 addresses). The ISP needs to
distribute these addresses to three groups of customers as
follows:
a. The first group has 64 customers; each needs 256
addresses.
b. The second group has 128 customers; each needs 128
addresses.
c. The third group has 128 customers; each needs 64
addresses.
Design the subblocks and find out how many addresses are
still available after these allocations.