Chapter - 2
Network Fundamentals
Definition: Networking
• A network means collection of inter-connect
elements
• Example: network of friends
• The individual computer of a network are to
be connected by a medium
Network Categories
• Division Based On Scope
– PAN, LAN, MAN, WAN, internetworks
• Division based on connection
– Wired network, wireless network , MANet, sensor
network
• Division based on communication type
– Broadcast networks, point to point netwroks
• Division based on usage
– Home network, sensor network
Network components
•
•
•
•
•
Network interface card( NIC )
Cable for wired connection
Frequency band for wireless transmission
The Server and the nodes
Inte- connecting devices
–
–
–
–
–
Switch
hub
Repeater
Bridge
router
Division Based on Scope
•
•
•
•
PAN
LAN
MAN
WAN
PAN(Personal Area Network)
• Personal Area Network are usually confirmed to surrounding
of a single person typically within a range of 10 meters.
• The main device usually is the computer.
• Such as Printer, Scanner, PDA, Mobile Phones.
LAN(Local Area Network)
• A local area network(LAN) is a group of computers and
associated devices that share a common communication
line or wireless link
• Typically, Connected devices share the resources of a
single processor or server within a small geographic area.
• A local area network may serve as few as two or three
users or as many as thousands of users
• The communication cable and connectors are similar
• Scope of LAN is limited to an organization, we can
implement strict policy rules within the network.
• Ex: account data access by account department
• Gateway level filtering is possible.
• Gateway are devices between the LAN and outside world.
• LAN is secured from the attacks generated out side
– Ex- Gateway level spam filtering which filters
– Span at the getaway level does not allow them to enter
the LAN
• Congestion and flow control are not serious issues in a
LAN
• LAN are connected is know as topologies
• Various topologies are in possible in network
MAN(Metropolitan Area Network)
• A Metropolitan Area Network (MAN) is a network that is
utilized across multiple buildings
• Commonly used in school campuses or large companies
with multiple buildings
• Is larger than a LAN, but smaller than a WAN
• Is also used to mean the interconnection of several LANs
by bridging them together. This short of network is also
referred to as a campus network
• MAN aim was to provided enough bandwidth a large of
customers and provided services :
• Offer a platform on which citizens can connect to each
other like mail ,audio or video conferencing
• Facility to book train and air tickets in advance
• Make the hotels, theaters and restaurants of a city
accessible to it’s citizen directly
• Video on demand to customers who are interested
WAN(Wide Area Network)
• Is the largest network of all network types.
• The internet is the largest WAN in the world.
• WAN generally covers large distances such as states,
countries or continents.
• WAN is group of MANs or LANs or the mixture of both
network.
• An example in the society using WAN is the banking
organization.
Internetworks
• An internetworks is a connection that joins two network.
• The internet that we are used to is one such internetwork.
• WAN connect multiple nodes or networks into a single
union.
• Internetworks are also designed to do the same.
• WAN are also interconnected by the internet.
• The internet is sometimes referred to as ‘network of
network’ because it connect multiple networks together.
• WWW is not a internet.
• It is a service provided on top of the internet
• Interconnection between such documents is done using
hyperlinks using a protocol called HTTP.
Difference between Three types of
network connection
Division Based On Connection
•
•
•
•
Wired network
Wireless network
MANets
Sensor Networks
Wired Connection
• It is use some form of cables to connect to each other.
• Copper based UTP cat 5 cable for low end
• Various types of fiber optic cable for high end.
• The most popular wired network Ethernet network
• Modern network use either
• Fast Ethernet (100 MB/sec speed)
• Gigabit Ethernet (1 Gigabit/sec speed)
• 10G Ethernet (10 Gigabit/sec speed)
• Fiber optics may be the only wiring mechanisms in future.
• It uses wired made of pure glass.
• There are no elections, but light rays through the fiber.
• Major advantage of fiber optic cabling is the bandwidth
• Bandwidth in the order of gigabits.
• More bandwidth, as it can carry more data per second.
• Greater bandwidth can transmit bulky data without any
congestion.
• Ex: textual data consumes less bandwidth.
• Bandwidth also depend on the distance.
Wireless Connection
• This network are connected without wires.
• There are multiple ways network can be built.
• The nodes are connected to each other directly without having
any intermediary which sometimes called as the ad hoc
network
• First wireless network was known as ALOHA.
• The principle are used in ALOHA was also used in Ethernet
and also in various wireless network protocol today.
• Ethernet was designed for LANs which usually fits in a single
room, while ALOHA was design with a greater scope in mind.
• It was difficult for the sender in ALOHA to find if somebody
else is already transmitting at the same time.
• Ethernet could detect this and thus it performed far better.
• ALOHA is no more used in real sense.
• Other network like 802.11 and 802.16 are more use today
MENet
• A mobile ad hoc network is a continuously self-configuring,
infrastructure less network of mobile devices connected
without wires.
• Each device in a MENet is free to move independently in any
direction and will therefore change its links to other devices
frequently.
• The communication in MENet is take place by using multi-hop
paths.
• Nodes in the MENet share the wireless medium.
•
The topology of the network changes erratically and dynamically.
•
In MENet breaking of communication link is very frequent as
nodes are free to move anywhere.
•
Services of MANets
1. One can access the internet from the hotel by joining its network.
2. We can join the network of a railway station and get the latest details
of incoming and outgoing trains.
3. A student can access the collage network from the parking slot or from
the lobby of the classroom.
4. We can exchange files during a flight with co-passengers.
5. Students can exchange class notes without writing anything manually
•
Issues in MANet
1. Dynamic topology
2. Power consumption
3. Security
Sensor network
•
Sensor network is a network of micro, electro, mechanical devices.
•
Which are design to sense some characteristics of the
surroundings.
•
–
Ex: temperature sensor
–
Habit detector
We do not get to see sensor network in our day to day life but there
access is increasing .
•
When hundreds of sensor are use in a network keeping the cost of
the individual sensor low becomes very imporatant therefore
sensor are design with less memory and processing power
•
Issues of sensor network:
–
Less memory
–
Less processing power
–
Battery life
Difference between
Sensor Network
MANets
No of nodes is usually very large.
A moderately size network can easily
contain thousands of nodes.
A large MANets may have hundreds of
nodes
Sensor can be immobile
All nodes may be mobile nodes
Nodes of Sensor network are not only
small in size, less processing power and
less memory
Compare to sensor node greeter
processing power and large memory
Sensor nodes may not be individually
addressable
Ex: Temperature
May be addressable
Power consumption is more
Power consumption is less then sensor
network
Sensor nodes may be placed in unfriendly
MANets nodes are movable
Division based on Communication type
•
Here categorized networks into two categories:
– One that uses broadcast as a means of communication
– Another that use point to point communication to delivery
messages.
•
Ex: analogy of broadcast and point to point networks.
•
Class room communication by two ways:
– Announce the message to all (broadcasting)
– To locate the exact location of the position of the
recipient and pass the message via other members of
the group (point to point)
Broadcast network
•
Broadcasting is used to pass message.
•
The sender broadcast the message which is received by its
intended recipient.
•
Other reject it.
•
It appears wasteful as it requires the attention of every node.
•
Broadcasting uses in following cases:
1. Better when a very low probability of more than one user
transmitting simultaneously
2. It is useful when the network is inherently a broadcast
network.
3. Better when routing through neighbors or addressing each
node of the network is not required
4. Broadcasting helps when the topology is not fixed.
Broadcast network
Point to point network
•
P2P network have a number of connections between
individual nodes and hence a message can use multiple
route to reach a particular destination.
•
The sender can either transmit directly or take the help of
its neighbor to pass the message indirectly
•
P2P communication sounds as a better option than
broadcast.
•
P2P communication consumes less bandwidth, as it restrict
itself to a single channel from the sender to the receiver and
not other channel.
•
It is important to mention here that there may be multiple
P2P connections require for a single transmission.
•
The helping neighbors that we mentioned earlier are called
routers in networking area .
• P2P Issues :
– P2p requires to know where the receipt
– Sender must know where each router is similar each
router must be aware of where other routers are located
– For inherently broadcast network (like wireless
network) P2P communication is not possible.
– Simple broadcasting solution is preferable to complex
P2P.
Division based on usage
•
Networks are generic and are used for a variety of operations
such as remote database access, remote s/w maintenance file
sharing, etc.
•
There are two areas where the research is already on and we
may be able to see much more growth in nearest future
– Home network
– Wireless sensor network
•
Wireless sensor network are designed for very different type
of usage than normal networks.
•
There are other areas like wearable computers and general
computing where some sort of networking is used.
Home Network
Imagine the following scenario:
•
Refrigerator reminds about buying vegetables
•
Stranger trying to break into your house
•
Babysitter is sleeping
•
TV has a serious problem and it conveys
•
Electric bulb tells us if it is going down
•
Lamp dims itself when you are asleep
•
Night lamp automatically switches on and off
•
Smart spectacles helps old people for finding out.
•
Smart Keys (where is my key?)
•
A phone receiver transfers the call automatically ( like
upstairs to downstairs )
•
Control house via Internet or phone.(if u forgot to switch
off the lights so you can off via internet)
•
The shower adjusts the temperature
•
Single remote control for many home devices (like TV, AC,
video player etc.)
•
Home network issues:
– Robustness (refrigerator not generate error for i)
– Cost ( programming refrigerator are costly then simple)
– Security issues (using remotely anyone access your
home control)
– Regular upgrades (upgrade new version of software )
– Maintenance and availability (after few years processor
will not work properly)
– Wired or Wireless (if we shift our house)
– Holding the vendor responsible
Sensor network
•
Is a network of micro elctromicanical device called sensor.
•
Develop to sense some sensory information.
•
sensor networks are used for specific purposes like
monitoring a process or recording the outcomes of a
continues experiments.
•
Sensor network areas:
– Fire erupts
– Whether forecasting
– Disaster management (monitoring building and record
vibration data confirmed)
Other categorization of Network
• Pervasive computing and wearable computers are current area
of network .
Network Components
•
•
•
•
•
Network interface card( NIC )
Cable for wired connection
Frequency band for wireless transmission
The Server and the nodes
Interconnecting devices
– Switch
– hub
– Repeater
– Bridge
– router
Network interface card( NIC )
• Network interface card also called as NIC or LAN card
• NIC is plugged into the motherboard and it is connected to the
network by a cable
• LAN card is also termed as a LAN adapter
• NIC card is the first step towards getting connected to a
network.
Cable for wired connection
• We are connected to the network in a wired way, cable must
connect to our NIC.
• Cable can be of different types.
• Cat-5 is the most commonly used cable.
• It made up of copper
• It is known as Unshielded Twisted Pair category 5 (UTP cat-5)
• Another is fiber optic cable
• Its run on light rays
• It is made up of pure glass which is transparent
• Both cable used based on characteristics.
•
Most important property is bandwidth
• Bandwidth is directly Propositional to the data per unit time that
can pass through the cable
• The capability to send data across a long distance.
• But bandwidth gradually decreases as we increased the
distance.
• A fiber optic cable can send the signal to a long distance in the
range of 5 to 10 kilometers.
• With less bandwidth
• Cat 5 has a less interference than cat 3 and thereby it supports
greater bandwidth.
• Same thing for cat 6 and cat 7
• Fiber optic cable almost eliminate the probability of
interference and thus better than the rest.
Frequency band for wireless
transmission
• Frequency for wireless transmission is similar
to having wire for wired communication.
The Server and the nodes
• Networked machine in the networking parlance is known as a
node.
• It also known as a host
• Communication is to take place between the server and the host.
• Server are machine which can provide services to nodes or hosts.
• Server design for a specific service.
• Like internet server, database server, mail server etc.
• Nodes can be communicate with these servers either in a wired or
wireless way.
Interconnecting devices
• An intermediate device s used which has one connection for
the server and multiple connections for the client.
• So here different categories of devices are:
– HUB
– Switch
– Repeater
– Bridge
– Router
TOPOLOGY
STAR
RING
BUS
ARCHITECTURE
TYPES
PEER TO PEER
CLIENT-SERVER
LAN
MAN
WAN
TECHNOLOGY
INTRANET
EXTRANET
INTERNET
DEVICES
NIC
HUB
ROUTER
MODEM
ACCESS
POINT
NETWORK
MEDIUM
PYSHICAL / WIRELESS
TWISTED PAIR, COAXIAL, FIBRE OPTIC
INFRARED, RADIOWAVE, SATELLITE
PROTOCOL
192.168.1.3
TCP/IP
SOFTWARE
NETWORK OPERATING SYSTEM
CLIENT SOFTWARE
HUB
• A hub is interconnected devices that connects a server with its
clients through wires.
• A device used to connect several computers together
• Is a fairly unsophisticated device as it doesn’t manage the
traffic through it
• There are two types of hubs
1) Active Hub
2) Passive Hub
• Active HUB :
– Amplify or repeat signals that pass through them
• Passive HUB:
– Merely connects cables on a network and provides no
signal regeneration
• Hubs regenerate and retime network signals
• Hub spread signals through the network
• They cannot filter network traffic
• They cannot determine best path
• They are used as network focus on point
• It has multiple ports for clients and a single port for the server.
• Hub have capability to receive data on any port and transmit
the same to all other ports.
Switch
• A device used to segment networks into sub-networks, which
prevents traffic overloading in network
• It is a sophisticated device, is responsible for filtering and
forwarding data
• In environments where there is a need for a great deal of
analysis of network performance and security
•
There is a condition of a firewall, network interruption
detection and performance analysis modules that can plug into
switch ports.
• Data-link layer device
• Replaces bridges and sometimes routers
• Similar in appearance to a hub
• Forwards incoming traffic out to the destination port only
• Converts a shared network medium to a dedicated one
• Offers advantages such as reduced network congestion and the
use of full network bandwidth
• Can operate in full-duplex mode
Repeater
• A device used to expand the boundaries of a wired or wireless
LAN.
• Amplify the data signals before sending them on to the
uplinked segment, thereby countering signal fall down that
occurs over extended lengths of wire.
• Receives a signal and retransmits it at a higher level and/or
higher power, or onto the other side of an obstruction, so that
the signal can cover longer distances.
Repeaters (continued)
Bridge
• Connects multiple network segments.
• Similar to repeaters or network hubs, however, can manage
data from one network rather than simply rebroadcast to
adjacent network segments.
• Analyze incoming data packets to determine if the bridge is
able to send the given packet to another segment of the
network.
Advantages and Disadvantages
ADVANTAGES OF BRIDGES
DISADVANTAGES OF
BRIDGES
Simple bridges are inexpensive
Does not scale to extremely large
networks
LANs interconnected are separate
Buffering and processing
introduces delays
Helps minimize bandwidth usage
Bridges are more expensive than
repeaters or hubs
Router
• Device that interconnects two or more computer networks, and
selectively interchanges packets of data between them
• It works like a bridge but can handle diff. protocols
• Each data packet contains address information that a router can
use to determine if the source and destination are on the same
network, or if the data packet must be transferred from one
network to another
• In case of an unknown destination, a router sends the traffic to
another router
The Connection
• Connection-Oriented connection
• Connectionless connection
• Connection-oriented connection on top of
connectionless connection
• Connectionless connection on top of
connectionless connection
• Addressing issues
The Connection
• The first meaning is related to having a physical connection of
a node or a server to the network
• It is either wired or wireless
• A physical connection can be implemented using a network
interface card,
• A USB connection and serial or parallel port connection
• No data communication can take place without having a
physical connection.
• In networking parlance the word ‘Physical’ is not always
something which is physical.
• There is a frequency band which is allocated and used.
• Before the communication begins if the sender sends a request
and waits for an acknowledgement
• Then a logical connection is said to be established between the
sender and the receiver.
• A formal request for connection is made and a response is
required.
• A connection oriented case must establish a connection before
initiating a communication.
• It also require the logical connection to be terminated after the
communication is over.
• In a connectionless transfer, a logical connection is not
established beforehand.
• Even in that case, a physical connection must be established.
The Physical Connection
• The physical connection between a machine and its network
can either be wired or wireless.
– Connection by the network interface card
– Other types of connection
• Serial connection
• Parallel connection
• Connection using a modem
• Universal serial bus connection
Connection by the network
interface card
• This method having a physical connection to the network
• Some latest motherboards come set with a switch.
• Either the card is near the access point to send and receive
message or near some other computer with a wireless card.
• The Ethernet NIC contains a ROM chip which contains a
unique 48-bit physical address burned into it by the
manufacturer.
• The NIC is also referred to as a network interface controller or
a LAN adapter.
• It operates on Physical and the data link layer.
• It construct the frame, adds checksum from the network
• It concerts the bits into electro. mechanical signals while
sending and vice versa while receiving
• If the NIC is wired
• It sends the EM signals over wires
Other types of connections
• Establish connection with a network but there are other ways:
– Serial connection
– Parallel connection
– Connecting using a modern
– Universal serial Bus connection
Parallel port
Serial port
Serial connection
• A serial connection is done by using either RS-232 or RS-449
cable which is inserted at the machine’s serial.
• There are one or two such ports on the machine’s
motherboard.
• The other end serial port must terminate directly into the
recipient's machine.
• It is possible to connect a node with the server using this port
• The problem of multiple nodes with one server and limitation
of the distance.
• It is better to use USB then RS-232 or RS-449
Parallel Connection
• A parallel connection can be achieved using the machine’s
parallel port.
• the distance not suitable for connecting devices.
• Both serial and parallel ports are used for connecting to other
devices.
• Like printers.
Connection Using A Modem
• When we dial the customer care number of our mobile service
provider
• We get connected to a computer system at the other end.
• We choose an option from the supplied menu to get the desired
information we want.
• So how do we connect computer system with voice-based
phone system?
• So its possible using a device called modem.
• Its job is to send digital data over a voice channel.
• Modems were used to connect remote networks using phone
lines.
• Our computer connects to a modem which in turn connects to
the telephone line.
• When the computer sends zeros and ones
• The modem converts them to different voice frequencies
• At the other end there is another modem
• Which converts those voices back to zeros and once
Universal serial bus connection
• The universal serial bus (USB) is fast replacing serial and
parallel ports for a large range of devices.
• It not replace the LAN card
• USB is an alternative to the LAN card.
Layers and services
• The lower layers provide services to the upper layers.
• Each layers can act both as a service provides as well as a
service consumer.
Design of layers as service provide and
Users
• The physical layer’s job is to send the frames bit by bit and see that
they are received at the other end.
• The data link layer takes data from the network layer, constructs a
frame out of it and passes it to the physical layer in a way that It. it
also ensures error free data transmission.
• The network layer takes the data from the data link layer and
provides routing services to decide who the next immediate
recipient is.
• It takes help from the routing table to decide the address of the
actual recipient.
• Once the address is finalized, it passes the information to the
data link layer.
• The data link layer gives the information to the physical layer.
• The physical layer transmits the frame bit by bit to the next
immediate recipient.
• The data link layer takes the services of the physical layer to
transmit frames to the other end.
• The network layer takes the services of the data link layer to
send packets to the next immediate location.
• The data travels from the physical layer to the network layer
back.
• The transport and application layer are not involved in the
process.
• The application and transport layers are considered end to end
layers.
• The sender application layer gets commands from the sender
application (a client)
• It travels down to the physical layer and then to the next
intermediary’s physical layer.
• It then travels up to the network layer where it decides the next
immediate destination.
• It then travel back to the physical layer and proceeds to the
next immediate destination’s physical layer.
• After it reaches at final destination the data goes up to the
application layer which passes it to the application (the server)
Standardization of services
1. Each layer using the services of the layer immediate below it,
interacts with its peers.
2. Each layer sends and receive data in a format which can only
be understood by the peer in the recipient.
3. Ex: a network layer packet, once encapsulated in a data link
layer frame its received by only a network layer of recipients.
4. Each layer, while talking to a peer, uses a specific protocol to
communicate.
a protocol not only decides the syntax to be followed but also
the order in which they are executed.
• Ex: when a SMTP client talk to a server its send a HELO
message first and the server always respond with and OK
message.
• Then SMTP client send MAIL FROM message and the server
send OK message As its ack.
• Then the client send MAIL TO message and receives an OK
message in detail
• The protocol governs the syntax and sequence of messages.
• Why do we need these protocols in the first place?
– If the peers are designed by two independent parties then
they can interact only if there is a standard protocol that
governs the design and functioning of both the layers.
– Ex: an email client developed by a programmer in India can
easily talk to an email server based in US provided both of
them are governed by standard protocol.
– A protocol once standardize can make arbitrary application
to talk to any other application at the same layer.
• Two networks having different physical characteristics (one is
wired and other is wireless)may have a different physical layer
and data link layer, but if they have standardize network layer
they can still communicate.
• In this case when a wired frame is received by a router
• The router after extracting the network layer packet from the
frame, construct a wireless frame which is equal to the wired
frame and pushes the extracted packet inside and forward it.
• So we can say that an email may be passed through many
intermediate heterogeneous networks to reach destination
application
• A machine containing and Ethernet card for coma pay X must
be able to work with a switch or hub from company while(data
link layer standardization.
Quality of Service Issues
• Refers to fulfilling the expectation of customers
• Ex: customer want the data transmission to be error free and in
order
– Suppose the requirement is to have 95% correct receipt for
a network sending and receiving data.
– Then the remaining has to be retransmitted two achieved
100% correct result.
• Ex: to have 90% video frames reaching the destination intact.
• Thus only the few black screens are seen by the receiver in this
case.
• It is to be noted that we can not transmit lost frames here for
the problem of sequencing and the real time distribution needs.
• That’s why we need QoS is important factor in services like
audio and video.
• A customer wants grater bandwidth and faster accessibility to
their favorite websites.
• X-ray, Indian idol contest required VoIP qaulity.
• The internet gives an application developer the choice between
a reliable, stream oriented transport service(TCP) and
unreliable connection less service (UDP).
Applications of computer network
• Computer networks have become so common place that any
application of computer can also the thought of as an
application of computer network.
• there are very few applications that are purely desktop oriented
• Even office application consider to be pure desktop
applications sometime back, are now accessed through the
networks.
– We will discuss the applications of 3 different types of
computer networks.
1. Home networking applications
2. Mobile networking applications
3. Wireless network applications.