Lakhasly

This text introduces computer networking, covering various aspects from basic concepts to advanced topics. Section 1 defines computer networks, their purposes (information sharing, resource access, e-commerce, etc.), and elements (clients, servers, media, devices). Network types are categorized physically (PAN, LAN, CAN, MAN, WAN) and logically (peer-to-peer, client-server). Topologies (bus, ring, star, mesh, wireless) are explained, focusing on the advantages of star topology. Section 2 details transmission media (guided and unguided), describing copper (coaxial, twisted-pair) and fiber optic cables, their types, connectors (RJ-45), and crimping. Straight-through and crossover cables are differentiated based on their use cases. Section 3 discusses Medium Access Control (MAC) methods (CSMA/CD, CSMA/CA, Token Ring), communication methods (unicast, multicast, broadcast), and transmission types (simplex, half-duplex, full-duplex). The seven-layer OSI model is presented, detailing each layer's functions and protocols (TCP, UDP, IP, etc.). Section 5 covers network devices: hubs (layer 1), switches (layer 2), bridges (layer 2), and routers (layer 3), explaining their functionalities and the ARP protocol for IP-to-MAC address resolution. ICMP's error reporting and diagnostic functions are also discussed. Section 6 explains IP addresses, their components (network and host addresses), classes (A, B, C), and types (private, public, static, dynamic). DHCP's automatic IP allocation and DNS's domain name resolution are described, including the loopback IP (127.0.0.1). Finally, Section 7 covers subnet masks, their binary and decimal representation, and their role in subnetting, illustrating how subnetting divides a network for efficiency and security. Binary-to-decimal IP address conversion is explained, and examples of subnetting calculations are provided, showing how to determine subnet masks and the number of usable hosts per subnet.

Introduction to networking
Section_1
E.M.A
What is the computer network ?
• Computer network is a group of devices connected with others through
any type of medium (medium or wireless).
• The purpose of network connection is to share common resource or to
exchange information.
• The first computer network was ARPAnet, it started to work on October
1969, it was between US research institutes, and marking the born of
internet.
• ARPAnet transformed to use TCP/IP in 1983.
Purpose of network?
• Easy access and sharing of information.
• Sharing of files and network resources (printers , scanners, fax,).
• Networks (e-commerce, IP telephony, Video on Demand, Video
conferencing).
• Electronic mail.
• Anautomated teller machine (ATM).
• Ability to use network software.
Network elements
• Clients [known as endpoints, users, or nodes].
• Servers [offer service to clients].
• Media or medium [cables or WIFI signal connect clients and servers
to others or to network devices].
• Network devices [devices provide easy way to connect multiple
clients to same server].
Types of networks
We can divide networks according two types as follow :
• Physical types of network (depending on the network’s area).
• Logical types of networks (depending on the network’s management).
The Physical types:
Based on the geographic dispersion of network components, networks can be classified
into various categories, including the following:
• Personal-area network (PAN).
• Local-area network (LAN).
• Campus-area network (CAN).
• Metropolitan-area network (MAN).
• Wide-area network (WAN).
PERSONAL-AREA NETWORK (PAN)
• A“PAN” is a network whose scale is even smaller than a LAN. For example, a
connection between a PC and a digital camera via a universal serial bus (USB)
cable could be considered a PAN.
LOCAL-AREA NETWORK (LAN)
• A LAN interconnects network components within a local area (for example,
within a building).
• It connect many devices in small area to share the data and resources like a
home ,office , building, school , or airport
• It is a group of network components that work within small area .
Campus-area network (CAN)
• A campus area network is larger than a local area network LAN since it may span
multiple buildings within a specific area. Most CANs are comprised of several LANs
connected via switches and routers that combine to create a single network.
• A campus area network (CAN) is a network of multiple interconnected local area
networks (LAN) in a limited geographical area. A CAN is smaller than a wide area
network (WAN) or metropolitan area network (MAN).
Metropolitan area network (MAN)
• A metropolitan area network (MAN) is a network with a size greater than LAN. It normally
comprises networked interconnections within a city that also offers a connection to the
Internet.
• It is a group of LANs that are interconnected within small area.
Wide-area network (WAN)
• Awideareanetwork (WAN) is anetwork that existsovera large-scalegeographical
area. AWANconnects different smaller networks, including local area networks
(LANs)andmetroareanetworks(MANs).
The logical types of networks:
• Peer-to-Peer networking.
• Server-base networking.
Peer to peer (Workgroups)
• Peer-to-peer networks allow interconnected devices (for example, PCs) to share their
resources with one another. Those resources could be, for example, files or printers and so
on.
• Each PC that's a member of the group can access the resources being shared by other PCs
and in turn can share its own if configured to do so.
• Windows workgroups can be found in homes, schools and small businesses.
• In computer networking, a workgroup is a collection of computers on a local area network
(LAN) that share common resources and responsibilities.
Client-Server Architecture
• Client-server architecture is an architecture of a computer network in which many clients
(remote processors) request and receive service from a centralized server (host
computer). Client computers provide an interface to allow a computer user to request
services of the server and to display the results the server returns.
• Servers wait for requests to arrive from clients and then respond to them.
• Clients are often situated at workstations or on personal computers, while servers are
located elsewhere on the network, usually on more powerful machines.
Network Topologies:
• The way in which devices are interconnected to form a network is called network
topology.
• Topology- Physical and logical network layout
➢Physical– actual layout of the computer cables and other network devices.
➢Logical– the way in which the network appears to the devices that use it.
• Common topologies:
➢Bus, ring, star, mesh and wireless.

Bus-Topology:
• The devices are connected using cable that called carrier because it carries data.
• It has terminators at the beginning and at the end of the cable.
• Devices are connected to the cable using T-connectors or taps.
Ring-Topology:
• Data travels in circular fashion from one computer to another on the network.
• Has no terminators because it has no beginning or end.
• Every device retransmit the received signal. Therefore, the signal keep strong for a long
distance.
• Has the same disadvantages of bus-topology.
Ring-topology cont.
Mesh-Topology:
• Each computer connects to every other.
• High level of redundancy.
• Rarely used.
➢ Wiring is very complicated
➢ Cabling cost is high
➢ Troubleshooting a failed cable is tricky
Star-Topology:
• All computers/devices connect to a central device called hub
• Each device requires a single cable.
or switch
.
• Point-to-point connection between the device and the switch.
• Most widely implemented.
Advantages of the star-topology:
• Easily expanded without disruption to the network.
• Cable failure affects only a single user.
• Easy to troubleshoot and isolate problems.

Wireless networking :
• Donotrequirephysicalcabling.
• Particularlyuseful forremoteaccessfor laptopusers.
• Eliminatecablefaultsandcablebreaks.
• Signal interferenceandsecurityissu Introduction to networking
Section_2

E.M.A
Transmission Media:
For any networking to be effective, raw stream of data is to be transported from
one device to other over some medium. Various transmission media can be used
for transfer of data. These transmission media may be of two types:
➢Guided: In guided media, transmitted data travels through cabling system that
has a fixed path. For example, copper wires, fiber optic wires, etc.
➢Unguided: In unguided media, transmitted data travels through free space in
form of electromagnetic signal. For example, radio waves, lasers, etc.
Transmission Media:
Types of cables & connectors:
➢ Copper cable:
• Coaxial.
▪ Ticknet.
▪ Thinnet.
• Twisted-Pair.
▪ Shield Twisted Pair (STP).
▪ Unshielded Twisted Pair(UTP).
➢ Fiber cable:
• Fiber-optic cable.
❑ Twisted-pair is considered the most-used one.
CoaxialCable:
Coaxial cables, often shortened to coax, are a type of electrical
cable that is used to transmit radio frequency (RF) signals. They
are made up of four main parts:
➢ Inner conductor: This is the central wire that carries the
signal. It can be made of copper, aluminum, or another metal.
➢ Dielectric: This is the insulating material that surrounds the
inner conductor and separates it from the outer shield. It is
typically made of plastic or foam.
➢ Outer shield: This is a braided or foil conductor that
surrounds the dielectric and the inner conductor. It helps to
block interference from external sources.
➢ Outer jacket: This is a protective layer that protects the cable
from damage. It is typically made of PVC or another type of
plastic.
Coaxial cables are used in a wide variety of
applications,including:
➢CableTV:Coaxial cables areused toconnect cableTVboxes to
set-topboxes.
➢SatelliteTV:Coaxial cables areused toconnect satellitedishes to
set-topboxes.
➢ Internet: Coaxial cables are used to connect cablemodems to
computers.
▪ Coaxial cablesareavailable inavarietyof lengthsand impedances.
Themostcommontypeofcoaxial cable isRG-6,whichisusedfor
cableTVandsatelliteTV.
Twisted-pair cables:
Twisted-pair cables are a type of cabling that consists of twoormore insulated copperwires twisted
together inpairs. The twisting of thewires helps to cancel out electromagnetic interference (EMI) and
crosstalk,whichcandegrade thequalityof thesignal being transmitted. Twisted-pair cables arecommonly
usedfortelephoneanddatacommunications, includingEthernetnetworks.
Types of Twisted-pair Cables:
❑ There are two main types of twisted-pair cables:
➢ Unshielded Twisted-Pair (UTP): This is the most common type of
twisted-pair cable. It is less expensive and easier to install than shielded
twisted-pair cable, but it is also more susceptible to interference. UTP
cables are typically used for short-distance applications, such as
connecting computers to a network switch or router.
➢ Shielded Twisted-Pair (STP): This type of cable has a foil or braided
shield around each pair of wires. The shield helps to block interference
from external sources, such as power cables and fluorescent lights. STP
cables are more expensive and difficult to install than UTP cables, but
they offer better performance in high-interference environments. STP
cables are typically used for longer-distance applications, such as
connecting buildings or for critical data applications.
There are different categories of twisted-pair cables, which
are rated for different speeds and bandwidths. The most
commoncategoriesare:
➢ Category 5 (Cat 5): This is the most basic type of twisted-pair cable, and it is rated for
speeds of up to 100 Mbps.
➢ Category 5e (Cat 5e): This is an improved version of Cat 5, and it is rated for speeds
of up to 1 Gbps.
➢ Category 6 (Cat 6): This is a higher-performance cable than Cat 5e, and it is rated for
speeds of up to 10 Gbps.
➢ Category 6a (Cat 6a): This is an improved version of Cat 6, and it is rated for speeds
of up to 10 Gbps over longer distances.
➢ Category 8 (Cat 8): This is the latest category of twisted-pair cable, and it is rated for
speeds of up to 40 Gbps.
▪ Twisted-pair cables are typically terminated with RJ-45 connectors, which are the same
type of connectors used for Ethernet cables.
Crimping Twisted-Pair Cables:
Crimping twisted-pair cables involves attaching specialized connectors, like RJ-45s, to their ends for network
connections. Itrequiressometoolsandspecificstepstoensureasecureandfunctionalconnection.
Equipment:
➢Crimpingtool:Chooseaqualitytool foryourcablecategory(Cat5e,Cat6,etc.).
➢RJ-45connectors:Matchthecategorytoyourcable.
➢Cablestripper:Removesoutersheathandinner insulation.
➢Cablecutter:Precisecutsforproperwirelength.
➢Wirecutter/stripper(optional):For individualwirestrippingifneeded.
T568A And T568B Wiring Standard Basis :
ARJ45 connector is a modular 8 position, 8 pin connector used for terminating Cat5e patch
cableorCat6cable. Apinout is a specific arrangement ofwires that dictatehowthe connector is
terminated.TherearetwostandardsrecognizedbyANSI,TIAandEIAforwiringEthernetcables.The
first is theT568AwiringstandardandthesecondisT568B.T568Bhassurpassed568Aandisseenas
thedefaultwiringschemefortwistedpairstructuredcabling. Ifyouareunsureofwhichtouse, choose
568B.
Straight Through Cable:
Astraight throughcableisatypeof twistedpaircablethat isusedinlocal areanetworkstoconnectacomputerto
anetworkhubsuchasarouter. This typeof cable isalsosometimescalledapatchcableand isanalternativeto
wirelessconnectionswhereoneormorecomputersaccessarouterthroughawirelesssignal.Onastraight through
cable, thewiredpinsmatch.Straightthroughcableuseonewiringstandard:bothendsuseT568Awiringstandardor
bothendsuseT568Bwiringstandard.Thefollowing figureshowsastraight throughcableofwhichbothendsare
wiredastheT568Bstandard.
Crossover Cable:
AcrossoverEthernetcable isatypeofEthernetcableusedtoconnectcomputingdevices togetherdirectly.
Unlikestraightthroughcable, theRJ45crossovercableusestwodifferentwiringstandards:oneendusesthe
T568Awiringstandard, andtheotherenduses theT568Bwiringstandard.The internalwiringofEthernet
crossovercablesreversesthetransmitandreceivesignals. It ismostoftenusedtoconnecttwodevicesof the
sametype:e.g. twocomputers(vianetworkinterfacecontroller)ortwoswitchestoeachother.
Straight Throughvs Crossover Cable, which to choose?
Usually, straight through cables are primarily used for
connectingunlikedevices. Andcrossover cables areuse for
connectingalikedevices.
UsestraightthroughEthernetcablefor
thefollowingcabling:
➢Switchtorouter.
➢SwitchtoPCorserver.
➢HubtoPCorserver.
Usecrossovercablesfor
thefollowingcabling:
➢Switchtoswitch.
➢Switchtohub.
➢Hubtohub.
➢Routertorouter.
➢RouterEthernetporttoPCNIC.
➢PCtoPC.
Fiber-optic cables:
Fiber optic cables are thin, flexible strands of glass or plastic that transmit
information using light pulses instead of electrical signals. This technology allows for
significantly higher bandwidth and longer transmission distances compared to
traditional copper cables.
Advantages:
➢ High Bandwidth: Fiber optic cables can transmit massive amounts of
data, reaching speeds of terabits per second (Tbps), making them ideal for
high-demand applications like internet, streaming, and cloud computing.
➢ Long Distance Transmission: Signals travel farther with minimal attenuation
(weakening) in fiber optic cables, enabling connections over hundreds of
kilometers without needing repeaters.
➢ Immunity to Interference: Unlike copper cables susceptible to electromagnetic
interference (EMI), fiber optic cables are immune to such disruptions, ensuring
reliable signal transmission.
➢ Security: Interception of light signals within the cable is much harder
compared to electrical signals, offering enhanced data security.
Wireless Transmission:
• Wireless transmission is a form of unguided
media. Wireless communication
involves no physical link established between two or more devices, communicating
wirelessly. Wireless signals are spread over in the air.
• This type uses several methods such as radio waves, satellite waves, and Microwaves.
Introduction to networking
Section_3
E.M.A
Medium Access Control :
Medium Access Control (MAC), also known as Media Access Control, is a set of rules and procedures that
govern how multiple devices share a single shared transmission medium in a network. It's a crucial
component of the data link layer (Layer 2) of the OSI model.
Common Media access control methods:
➢ Carrier Sense Multiple Access with Collision Detection (CSMA/CD): Widely used in early Ethernet
networks, where devices listen for ongoing transmissions before sending data and implement backoff
mechanisms in case of collisions.
➢ Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA): Used in Wi-Fi and other wireless
networks, where devices avoid collisions by sending a request to transmit (RTS) before sending data and
waiting for a clear to send (CTS) response.
➢ Token Ring: Devices pass a special token around the network in a circular fashion. Only the device holding
the token can transmit data, ensuring orderly and efficient communication.
Communication methods:
➢ Unicast: one-to-one communication, where data is transmitted from a single source
to a single destination.
➢ Multicast: One-to-many communication, where data is sent to a group of devices
simultaneously.
➢ Broadcast: One-to-all communication, where data is sent to every device on the
network.
Transmission Types:
Transmission types refer to the different methods used to transmit data between devices in a communication
system. They define how information is packaged, sent, and received, ensuring reliable and efficient data
exchange.
Common transmission types based on direction:
➢ Simplex: Data transmission occurs in one direction only. Information flows from a single source device to
a destination device, but not the other way around. Examples include:
▪ Television broadcasting: Signals are sent from a single source (broadcasting station) to many receivers
(TVs).
➢ Half-duplex: Communication can happen in two directions, but only one direction at a time. Devices take
turns transmitting and receiving data. Examples include:
▪ Walkie-talkies: Users can only talk one at a time, requiring them to press a button to transmit and release
it to receive.
➢ Full-duplex: Enables simultaneous transmission and reception of data in both directions. This is commonly
used in:
• Telephone conversations: Both parties can speak and hear each other at the same time.
• Ethernet networks: Devices can send and receive data packets concurrently.
• Video conferencing: Participants can see and hear each other simultaneously.
The OSI 7-layers model
TheOSImodel,alsoknownastheOpenSystems Interconnectionmodel, isaconceptual frameworkusedto
describe network communication. It defines sevendifferent layers, eachwith specific functionalities and
responsibilities.
Layer 7: Application
➢ Function: Provides network services directly to user applications. Offers functionalities like:
▪ File transfer (FTP)
▪ Web browsing (HTTP)
▪ Email (SMTP, POP3, IMAP)
▪ Remote access (SSH)
▪ Video conferencing
➢ Protocols: HTTP, FTP,etc.
Layer 6: Presentation
➢ Function: Deals with data formatting and presentation, ensuring compatibility between
different systems. Handles tasks like:
▪ Encryption and decryption of data for secure communication.
▪ Data compression to optimize transmission efficiency.
▪ Character set conversion (e.g., ASCII to EBCDIC).
Layer 5: Session
➢ Managing communication sessions
➢ TheSession Layer provides process to process communications between two or more networked hosts.
This layer is responsible for maintaining proper communication by establishing, managing and terminating
sessions (a property of TCP) between two nodes. It takes care of gracefully closing sessions and for
session check pointing and recovery.
➢ Controls whether the data being exchanged in a session are transmitted as full or half duplex
messages.
Layer 4: Transport
➢ Function: Provides reliable and efficient data transfer services between applications on different devices.
Offers two main service types:
▪ Connection-oriented: Guarantees in-order delivery of data packets and error-free transmission (e.g.,
TCP).
▪ Connectionless: Offers faster, less reliable data transfer without establishing a connection (e.g., UDP).
➢ Protocols: Transmission Control Protocol (TCP), User Datagram Protocol (UDP), port numbers.
UDP & TCP protocols
➢ User Datagram Protocol (UDP
): UDP is a connectionless protocol that does not provide reliable data
transport. No acknowledgments are transmitted. This protocol gives a higher throughput and shorter
latency and is often used for multicasting, broadcasting and real-time multimedia communication
where occasional packet loss is acceptable. Messages sent with UDP are referred to as datagrams.
➢ Transmission Control Protocol (TCP
): TCP is a connection-orientated protocol that offers greater
reliability when it comes to transporting data than what UDP provides. With TCP, the application
which sends the data receives acknowledgment or verification that the data was actually received. It is
used for many protocols, including HTTP web browsing and email transfer where lossless data
transfer is important. Individual units of data transmission in the TCP protocol are referred to
as segments.
Layer 3: Network
➢ Function: Responsible for routing data packets across networks based on their logical addresses (IP
addresses). Uses routing protocols like Open Shortest Path First (OSPF) or Border Gateway Protocol
(BGP) to determine the best path for data to travel.
➢ Protocols: Internet Protocol (IP), Address Resolution Protocol (ARP).
➢ Additional functionalities: Performs network address translation (NAT) to allow private IP addresses to
communicate on the public internet.
Layer 2: Data-link
➢ Function: Packages data into frames, adds error detection and correction mechanisms (like checksums),
and controls access to the physical medium using protocols like Carrier Sense Multiple Access with
Collision Detection (CSMA/CD).
➢ Protocols: Ethernet, Wi-Fi (IEEE 802.11), Frame Relay, Point-to-Point Protocol (PPP).
➢ Additional functionalities: Provides logical addressing (MAC addresses) for identifying devices on the same
network segment.
Layer 1: Physical
➢ Function: Establishes the physical connection between devices and transmits raw data bits through a
physical medium like cables (copper, fiber optic) or wireless signals (radio waves).
➢ Protocols: Defines the electrical, mechanical, and operational specifications for transmitting data, including
voltage levels, cable pinouts, and signal encoding/decoding.
Introduction to networking
Section_5
E.M.A
Network devices:
• Hub.
• Switch.
• Bridge.
• Router.
Hub
• Ahub operates at the physical layer (Layer 1) of the OSI (Open Systems Interconnection) model.
It receives incoming data packets from one device connected to a port and then broadcasts those
packets to all other devices connected to its remaining ports. This broadcasting behavior makes a
hub a "dumb" device, as it lacks the intelligence to selectively send packets to specific devices.
• This broadcasting nature of hubs creates a single collision domain on the network. This means if
two devices attempt to transmit data at the same time, a collision occurs, corrupting the data and
requiring retransmission. This can significantly slow down network performance, especially with
more devices connected.
• Due to these limitations, hubs are not widely used in modern networks. However, they may still
be found in some older installations or for very basic network setups where cost is a major
concern.
Switch
• Anetwork switch is a multi-ported device that connects devices on a network together.
It learns the MAC addresses of the devices connected to its ports and forwards data
packets only to the intended recipient. This improves network performance by reducing
congestion.
Howaswitchworks:
• A device on the network sends out a data packet. This packet contains the destination
MAC address (a unique identifier for each device on the network) of the device the data
is intended for.
• The switch receives the data packet and reads the destination MAC address.
• The switch consults its internal MAC address table, which maps MAC addresses to
switch ports.
• The switch forwards the data packet to the port that the destination device is connected
to.
Bridge
• Abridge is a networking device that operates at the data link layer (Layer 2) of the OSI
model. Its primary function is to connect multiple network segments or LANs and
forward data packets between them. Bridges are designed to improve network
performance and efficiency by reducing network congestion and limiting the scope of
broadcast domains.
• actslike a more sophisticated version of a hub but simpler than a switch.
Router
• Arouter, a key player in the networking world, acts as a traffic director for data packets across different
networks. Unlike a switch that manages devices within a single network, a router is responsible for
efficiently routing data between networks, including your home network and the vast internet.
Howarouterworks:
• Data Arrival: A device on your network sends data packets containing the destination IP address
(unique identifier for devices on the internet) and the data itself.
• IPAddress Deciphering: The router receives the data packet and analyzes the destination IP address.
• Routing Table Consultation: The router maintains a routing table that stores information about
connected networks and the best paths to reach them. It consults this table to determine the most
efficient route for the data packet.
• Packet Forwarding: Based on the routing table, the router forwards the data packet to the appropriate
network interface for it to reach its final destination.
ARP protocol
• The Address Resolution Protocol (ARP) is a crucial protocol used on local area
networks (LANs) to map Internet Protocol (IP) addresses, which are logical
addresses used for network communication, to Media Access Control (MAC)
addresses, which are the physical hardware addresses assigned to network devices.
ARP works behind the scenes to ensure data gets delivered to the correct device on
the network.
• ARPenables smooth communication by dynamically translating IP addresses to MAC
addresses, facilitating data delivery to the correct network device.
• ARP works seamlessly in the background, and users typically aren't aware of its
operations.
How does ARP work?
1.Data Transmission Initiation: A device on your network wants to send data to another device. It has the
destination device's IP address but not its MAC address, which is required for actual data transmission on the
network layer.
2.ARP Request Broadcast: The sending device broadcasts an ARP request packet across the network. This packet
contains the target device's IP address and a query asking "who has this IP address? What is your MAC address?"
3.Listening Devices: All devices on the network receive the ARP request broadcast.
4.Matching IP Address: The device with the matching IP address in the ARP request recognizes itself as the
intended recipient.
5.ARP Response: The matching device sends an ARP response packet directly back to the sender. This response
packet contains the device's MAC address.
6.MAC Address Storage: The sending device receives the ARP response and stores the target device's IP address
MAC address association in a cache for a certain period. This cache helps expedite future communication with
the same device.
7.Data Transmission: With the MAC address acquired, the sending device can now encapsulate the data within a
frame using the target device's MAC address, ensuring the data reaches the intended recipient.
ICMP protocol
• ICMP, which stands for Internet Control Message Protocol, is a foundational protocol in the TCP/IP suite.
It operates on the network layer (Layer 3) and acts as a messenger for network devices, exchanging
critical information about the status of data transmission. ICMP itself doesn't transmit data but rather
sends control messages that provide error reporting and diagnostic capabilities.
TypesofICMPMessages:
▪ There are various ICMP message types, each serving a specific purpose:
InformationalMessages:
• Echo Request/Reply (Ping): These messages form the basis of the ping command, a network utility
tool for testing connectivity between devices. The source device sends an Echo Request, and if
reachable, the target device responds with an Echo Reply.
ErrorReportingMessages:
• Destination Unreachable: Informs the sender that the intended recipient (device or network) cannot
be reached, often due to reasons like incorrect addressing or unreachable network.
• Time Exceeded: Indicates that a data packet surpassed its allotted time to reach its destination,
signifying potential network congestion or other issues.
Introductiontonetworking
section_6
E.M.A
IP understanding
• IP address is a unique number assigned to each device connected to a computer
network. More specifically, it identifies the network hardware of the device.
• Remember, every computer connected to the Internet must have an IP address.
• Again, think of it like phone number. Obviously, if you don’t have a phone number
you cannot make or receive calls. The same logic applies to IP addresses.
• An IP address serves two primary functions: (1) identification, and (2) addressing.
For example: your first and last name indicates who you are. But your home
address indicates where you live. Consequently, IP addresses have two
components: One part identifies the actual network that the computer is
connected to. This is known as the Network ID. The other part of the IP address
identifies a specific device or machine within the network. This is known as the
Host ID.
IP Address
An IP address (Internet Protocol address) serves as a unique identifier assigned to
devices on a network, enabling them to communicate with each other. It's essentially a
digital address that functions similarly to a physical address for your house, but for the
internet realm.
What they are:
• Numerical labels: Represented by a set of four numbers separated by dots (e.g.,
192.168.1.1). Each number ranges from 0 to 255.
• Unique identifiers: Assigned to devices to distinguish them on a network.
IP Addresses’ purpose:
• Communication facilitation: Allow devices to send and receive data packets across the
network.
• Addressing mechanism: Similar to how a postal address directs mail, IP addresses guide
data packets to their intended recipients on the network.
How IP is represented ?
IP components
•An IP address can be further divided into two parts:
• Network address: Identifies the network to which a device belongs (like a city in a
physical address).
• Host address: Uniquely identifies a specific device within the network (like a street
address and house number).
IP Address
Subnet Mask
OriginallyIPaddressesweredividedintofivedifferentcategoriescalledclasses.These
divided IPclasses areclassA, classB, classC, classD, andclass E.Out of these,
classesA,B,andCaremost important.
IP classes
Class A:
• Class A addresses are for networks with large number of total hosts. Class A
address uses only first higher order octet (byte) to identify the network prefix,
and remaining three octets (bytes) are used to define the individual host
addresses.
• The class A address ranges between 0.0.0.0 to 127.255.255.255. The first bit
of the first octet is always set to 0 (zero), and next 7 bits determine network
address, and the remaining 24 bits determine host address. So the first octet
ranges from 0 to 127 (00000000 to 01111111).
Class B:
• Class B addresses are for medium to large sized networks. Class B addresses use
the initial two octets (two bytes) to identify the network prefix, and the
remaining two octets (two bytes) define host addresses. The class B addresses
are range between 128.0.0.0 to 191.255.255.255.
• The first two bits of the first higher octet is always set to 10 (one and zero bit),
and next 14 bits determines the network address and remaining 16 bits
determines the host address. So the first octet ranges from 128 to 191
(10000000 to 10111111).
Class C:
• Class C addresses are used in small local area networks (LANs). Class C addresses
use the first three octets (three bytes) to identify the network prefix, and the
remaining last octet (one byte) defines the host address. The class C address ranges
between 192.0.0.0 to 223.255.255.255.
• The first three bit of the first octet is always set to 110, and next 21 bits specify
network address and remaining 8 bits specify the host address. Its first octet ranges
from 192 to 223 (11000000 to 11011111).
Classification of IP Address:
AnIPAddress isbasicallyclassifiedintotwotypes:
• Private IP Address
• Public IP Address
What is a Private IP Address?
The Private
IP Address of a system is the IP address that is used to communicate within the
same network. Using private IP data or information can be sent or received within the
same network. The router basically assigns these types of addresses to the device. Unique
private IP Addresses are provided to each and every device that is present on the network.
These things make Private IP Addresses more secure than Public IP Addresses
What is a Public IP Address?
The Public IP Address of a system is the IP address that is used to communicate outside the
network. A public IP address is basically assigned by the ISP
(Internet Service Provider).
Public IP Address is basically of two types:
• Dynamic IP Address
:
Dynamic IP Addresses are addresses that change over time. After
establishing a connection of a smartphone or computer with the Internet, ISP provides an
IP Address to the device, these random addresses are called Dynamic IP Address.
• Static IP Address
:
Static Addresses are those addresses that do not change with time.
These are stated as permanent internet addresses. Mostly these are used by the DNS
(Domain Name System) Servers.
DHCP and static IP:
DHCP and static IP address refer to two different methods of assigning IP addresses to devices
on a network:
DHCP(DynamicHostConfigurationProtocol):
• DHCPuses a server to automatically allocate IP addresses to devices joining the network.
• This eliminates the need for manual configuration on each device.
• As devices come and go, the DHCP server can reuse freed-up addresses for new
connections.
StaticIP:
• Astatic IP address is manually assigned to a specific device and remains constant.
• This method offers more control over network configuration, ensuring a device always has
the same address.
• However, it requires manual setup on each device and careful planning to avoid conflicts.
DNS (Domain Name System):
• DNS, or Domain Name System, is essentially the phonebook of the internet. It translates human
readable domain names (like [invalid URL removed] or wikipedia.org) into numerical IP addresses that
computers use to connect to websites.
How does DNS work?
• You enter a domain name: When you try to visit a website in your web browser, you enter a
domain name in the address bar.
• Your device asks a DNS server: Your device (computer, phone, etc.) doesn't understand domain
names, so it contacts a DNS server to look up the IP address.
• DNS server lookup: The DNS server checks its records to find the IP address associated with the
domain name. There's a hierarchy of DNS servers involved in this process, but that's the technical
nitty-gritty.
• IP address retrieved: The DNS server sends the IP address back to your device.
• Connection to website: Your device uses the IP address to connect to the web server hosting the
website. Then, the website content loads in your browser.
Loopback-IP
• Aloopback IP address is a special IP address that is used to test network connectivity on a local device
without the need for external network resources. It is often referred to as the loopback interface or
loopback address. The loopback IP address is reserved and assigned to the device's network interface,
allowing it to communicate with itself.
• The most commonly used loopback IP address is 127.0.0.1.
• It is used for troubleshooting.
Notes:
• The first IP in the network is reserved for the network’s name.
• The last IP in the network is reserved for the broadcasting.
• To make a connection between devices on two different networks, each device have
to has a default gateway “the router or network device IP”
Introductiontonetworking
Section_7
E.M.A
Subnet mask:
• The subnet mask, a 32-bit number like the IP address, plays a critical role in subnetting. It acts as a gatekeeper,
defining which bits in the IP address belong to the network portion (subnet) and which belong to the host
portion.
• Subnet Mask Bits: A 1 in the subnet mask corresponds to the network (subnet) bits in the IP address.
• Host Mask Bits: A 0 in the subnet mask corresponds to the host bits in the IP address.
Example:
Consider the IP address 192.168.1.10 and a subnet mask of 255.255.255.0 (commonly written as /24 in CIDR
notation).
• Subnet
Mask
(255.255.255.0):
This
translates
to
a
binary
of
11111111.11111111.11111111.00000000. The first three octets (24 bits) are set to 1, indicating they belong
to the network portion.
representation
• IP Address (192.168.1.10): Converting it to binary, we get 11000000.10101000.00000001.00001010.
• Applying the Mask: Performing a bitwise AND operation between the IP address and the subnet mask, we
isolate the network portion:
• Subnet Mask (Binary) : 11111111.11111111.11111111.00000000
• IPAddress (Binary) : 11000000.10101000.00000001.00001010
How to convert Ip address from binary to decimal and vice versa?
128 64 32 16 8 4 2 1
1 0 0 0 0 0 0 0 128
128 64 32 16 8 4 2 1
1 1 0 0 0 0 0 0 192 = 128+64
128 64 32 16 8 4 2 1
1 1 1 0 0 0 0 0 224 = 128+ 64+32
195 = 128 + 64 +2+1 128 64 32 16 8 4 2 1
1 1 0 0 0 0 1 1
Examples on binary to decimal conversion:
Subnetting
• Subnetting is the process of dividing a large network into smaller, logical subnetworks. It's
like creating neighborhoods within a big city. This creates a more efficient and manageable
network structure.
• By dividing the network into subnets, traffic only needs to be routed within the relevant
subnet, reducing congestion on the main network.
• Subnetting allows for isolating different departments or user groups, enhancing security
by limiting access to specific network segments.
How does subnetting work ?
• An IP address consists of two parts: the network address and the host address.
Subnetting borrows bits from the host portion of the address to create a subnet
mask. This mask defines the subnet portion of the IP address, identifying which
devices belong to the same subnet.
• There are different classes of IP addresses (A, B, and C) that have predefined bit
allocations for network and host addresses. Subnetting involves manipulating these
bits to create subnets with the desired number of usable hosts.
IfwehaveanetworkID:192.168.1.0withasubnetmask:255.255.255.0
Let’spresentthat inbinary:
NetworkID:11000000.10101000.00000001.00000000
Subnetmask:11111111.11111111.11111111.00000000
▪ Todoasubnettingforthisnetworkwefocusontheoctet thatusedforhostwhicheverybit initequal
tozero.
▪ Asweseeif thebitsareequal to1inthesubnetmaskthatmeansthecorrespondingbit intheIpisused
forthenetworkandif itequal to0thatmeansthecorrespondingbit intheIPusedforhost.
▪ Andtheonesshouldbeinsequencewithoutzerosamongthem.
▪ Therefore, todoasubnettingweflipweflipa0ormoreintoa1fromthelastoctet.
NetworkID:11000000.10101000.00000001.00000000
Subnetmask:11111111.11111111.11111111.10000000
Subnetmaskindecimal :255.255.255.128
That gives 21 probability = 2 networks.
Network_1 : 0 –127 , id=0, broadcast=127
Network_2: 128-255, id =128, broadcast=255
Network ID : 11000000. 10101000.00000001.00000000
Subnet mask: 11111111.11111111.11111111.11000000
Subnet mask in decimal : 255.255.255.192
• We can also write the network id and the subnet mask as
follow : 192.168.1.0/26 ➔ /26 refers to the number of ones in
the subnet mask.
That gives 22 probability = 4 networks.
Network_1 : 0 – 63 , id=0, broadcast=63
Network_2: 64-127, id =64, broadcast=127
Network_3 : 128 – 191 , id=128, broadcast=191
Network_4 : 192 – 255 , id=192, broadcast=255
We have 4 probabilities (networks), we can get the id and broadcast of them as
follows :
00000000 ➔ 0 - 63
01000000 ➔ 64 -127
10000000 ➔ 128 - 191
11000000 ➔ 192 - 255
Subnet mask values:
Example
192.168.5.0/24
5 subnet, 30 host
Solution
2n-2 >= 5 ➔ n is the number of bits will be network in the last octet in the subnet mask
We used (-2) for the future growth (2 networks for reserve)
n = 3
Subnet mask = 11111111.11111111.11111111.11100000
In decimal =255.255.255.244
Class C :
25 26 27 28 29 30 31 32
128 64 32 16 8 4 2 1
128 192 224 240 248 252 254 255

• =
  For the previous Example:
  N=3
  Length = 27 ➔192.168.5.0/27
  Subnet mask = 224
  The number of hosts for each network will be = 32
  N1➔0 –31 , N_ID=0, broadcast=31
  N2➔32 –63 , N_ID=32, broadcast=63
  N3➔64 –95 , N_ID=64, broadcast=95
  N4➔96 –127 , N_ID=96, broadcast=127
  N5➔128 –159 , N_ID=128, broadcast=159
  N6➔160 –191 , N_ID=160, broadcast=191
  N7➔192 –223 , N_ID=192, broadcast=223
  N8➔224 –255, N_ID=224, broadcast=255
  Example
  192.168.5.0/24
  12 subnet
  Solution
  2n-2>=12
  n = 4
  Subnet mask = 11111111.11111111.11111111.11110000
  In decimal = 255.255.255.240
  25 26 27 28 29 30 31 32
  128 64 32 16 8 4 2 1
  128 192 224 240 248 252 254 255
  For the previous Example:
  N=4
  Length = 28 ➔192.168.5.0/28
  Subnet mask = 240
  The number of hosts for each network will be = 16
  N1➔0 –15 , N_ID=0, broadcast=15
  N2➔16–31 , N_ID=16, broadcast=31
  N3➔32–47 , N_ID=32, broadcast=47
  N4➔48–63 , N_ID=48, broadcast=63
  N5➔64–79 , N_ID=64, broadcast=79
  N6➔80 –95 , N_ID=80, broadcast=95
  N7➔96–111 , N_ID=96, broadcast=111
  N8➔112 –127, N_ID=112, broadcast=127
  N9➔128–143 , N_ID=128, broadcast=143
  N10➔144 –159 , N_ID=144, broadcast=159
  N11➔160 –175 , N_ID=160, broadcast=175
  N12➔176–191 , N_ID=176, broadcast=191
  N13➔192 –207 , N_ID=192, broadcast=207
  N14➔208–223 , N_ID=208, broadcast=223
  N15➔224–239 , N_ID=224, broadcast=239
  N16➔240 –255, N_ID=240, broadcast=255