NETWORK FUNDAMENTALS important concepts.ppt

The Computer Network
 A computer network is a group of computers/devices(Nodes)
that use a set of common communication protocols over digital
interconnections for the purpose of sharing resources located on
or provided by the network nodes.
 The nodes of a computer network may include personal
computers, servers, networking hardware, or other specialised or
general-purpose hosts.
 The interconnections between nodes are formed from a broad
spectrum of telecommunication network technologies, based on
physically wired, optical, and wireless technologies.
 A communication protocol is a set of rules for exchanging
information over a network. physically wired, optical, and
wireless

The Network Diagram
(Click on the Words Below and Learn More About Each Component)
The Internet
Other LANS
Firewall
Router
Fiber Optic Network Cable
Server
PC
Wireless Network
Wired Network
Switch

The Advantages/Uses of Network
Simultaneous Access
 There are moments in any business when several workers may
need to use the same data at the same time.
Shared Peripheral Devices
Personal Communications
 Videoconferencing
 Voice over Internet Protocol (VoIP):-VoIP transmits the sound of
voice over a computer network using the Internet Protocol (IP )
rather than sending the signal over traditional phone wires
Easier Data Backup

Peer to Peer vs. Client-Server
Networks
• In peer to peer Network, there is no centralized management or
security and each computer is in charge of its own local users and
file and folder permissions. Since there is no centralized user
management, any user who wants access to resources on another
computer will need to have an account on that specific computer.
• So, if a user wants access to files on ten different computers, then
that user will need ten separate user accounts. Computers on a
peer to peer network are usually connected together through a
simple hub or network switch

client-server network
• A client-server network has clients (workstations) as well as a server (or many
servers). As you can see in figure 1.2, the clients are labeled Computer A,
Computer B, Laptop A, and so on.
• There is also a file server and a directory server, which is used to manage user
accounts and access controls.
• The main advantage here is that every user account is created on the directory server, and then
each computer, laptop, and other servers are joined to a domain where authentication is
centralized for logins and resource permissions.
• domain is a centralized way to manage computers, users, and resources, and each computer
joins the domain and each user is created as a domain user.
• Using a switch rather than a hub reduces broadcast traffic because the switch knows what port
each computer is connected to and doesn’t have to go to each computer or server to find the one
it is trying to get to. Switches can be thought of as "smart" hubs, or hubs can be thought of as
"dumb" switches.
• The client-server model is also very scalable, and the amount of concurrent connections to a
server is only limited to the licensing model in place and eventually the hardware limits in
regards to network bandwidth and server capacity.

Client Server model
• The downsides of the client-server model include:
• Increased costs because servers are more expensive than computers and network switches
are more expensive than hubs.
• More difficult to implement and maintain because of its complexity.
• Single point of failure if a directory server goes down and none of your users can log in.
This is often bypassed by having multiple directory servers (or domain controllers).
• Overall, if your environment has many resources and you want to centralize management of
your users and computers, then you should go with the clientserver model. If you only have
a few computers and users, then a peer to peer configuration should work just fine. Plus,
you can reconfigure it to a clientserver model in the future if needed.

The Networking Devices(Nodes)
1. NIC Card
2. Repeater
3. Hub
4. Switch
5. Bridge
6. Router
7. Gateway
8. Firewall

1. Network Interface Card
 NIC is used to physically connect
host devices to the network
media.
 A NIC is a printed circuit board
that fits into the expansion slot of
a bus on a computer
motherboard.
 It can also be a peripheral device.
NICs are sometimes called
network adapters.
 Each NIC is identified by a
unique code called a Media
Access Control (MAC) address.
 This address is used to control
data communication for the host
on the network.

2. Repeaters
 A repeater is a network device used to
regenerate a signal.
 Repeaters regenerate analog or digital
signals that are distorted by transmission
loss due to attenuation.
 A repeater does not make an intelligent
decision concerning forwarding packets

3. Hubs
 Hubs concentrate on connections.
 In other words, they take a group of
hosts and allow the network to see
them as a single unit. This is done
passively, without any other effect
on the data transmission.
 Active hubs concentrate hosts and
also regenerate signals.

4. Bridges
 Bridges convert network data
formats and perform basic data
transmission management.
 Bridges provide connections
between LANs.
 They also check data to
determine if it should cross the
bridge. This makes each part of
the network more efficient

5. Switches
 Switches add more intelligence to data transfer management.
 They can determine if data should remain on a LAN and transfer
data only to the connection that needs it.
 Another difference between a bridge and switch is that a switch
does not convert data transmission formats

6. Routers
 Routers have all the capabilities listed
above.
 Routers can regenerate signals,
concentrate multiple connections, convert
data transmission formats, and manage
data transfers.
 They can also connect to a WAN, which
allows them to connect LANs that are
separated by great distances.

7. Gateway
 A gateway is a piece of networking
hardware used in telecommunications
for telecommunications networks that
allows data to flow from one discrete
network to another.
 Gateways are distinct from routers or
switches in that they communicate
using more than one protocol to
connect a bunch of networks

8. Firewall
 A firewall is a network device or
software for controlling network security
and access rules.
 Firewalls are inserted in connections
between secure internal networks and
potentially insecure external networks
such as the Internet.
 Firewalls are typically configured to
reject access requests from
unrecognized sources while allowing
actions from recognized ones.
 The vital role firewalls play in network
security grows in parallel with the
constant increase in cyber attacks.

Network Media
The function of the media is to carry a flow of information through a LAN.
A.Wired Media:- A widely adopted family that uses copper and fiber media in
local area network (LAN) technology are collectively known as Ethernet
1. Copper Cable
a. Coaxial Cables
b. Shielded Twisted Pair(STP)
c. Unshielded Twisted Pair
2. Fibre Optic Cable
B.Wireless Media:- use the atmosphere, or space, as the medium.

1. Copper Cable
 The most common, easiest, quickest, and
cheapest form of network media to install.
 The disadvantage of sending data over
copper wire is that the further the signal
travels, the weaker it becomes.

a. Coaxial Cable
 It can be run longer distances than Twisted pair Cables.
• Speed: 10-100Mbps
• Cost: Inexpensive
• Media and connector size: Medium
• Maximum cable length: 500m

b. Shielded Twisted Pair(STP)
• Speed: 0-100Mbps
• Cost: Moderate
• Media and connector size: Medium to large
• Maximum cable length: 100m

c. Unshielded Twisted Pair
 UTP is a four-pair wire medium
used in a variety of networks.
 Each of the eight copper wires
in the UTP cable is covered by
insulating material
Speed: 10-100-1000 Mbps*
Cost: Least Expensive
Media and connector size: Small
Maximum cable length: 100m * (Depending
on the quality/category of cable)

UTP Implementation
 EIA/TIA specifies an RJ-45 connector for
UTP cable.
 The letters RJ stand for registered jack.

Fiber Optic Cable
 Glass fiber carrying light pulses, each pulse a
bit.
 Based on the Total Internal Reflection of
Light.
 High-speed point-to-point transmission
10-100’s Gbps
 low error rate:
 repeaters spaced far apart
 immune to electromagnetic noise

Communication Protocols
Internet Protocol Suite
 Also called TCP/IP, is the foundation of all modern
networking.
 It defines the addressing, identification, and routing
specifications for IPv4 and for IPv6.
 It is the defining set of protocols for the Internet.
IEEE 802
 It is a family of IEEE standards dealing with local area networks
and metropolitan area networks.
 They operate mostly at levels 1 and 2 of the OSI model.
Ethernet
 It is a family of protocols used in wired LANs, described by a set
of standards together called IEEE 802.3

Communication Protocols
Wireless LAN
 It is standardized by IEEE 802.11 and shares many properties with wired
Ethernet.
SONET/SDH
 Synchronous optical networking (SONET) and Synchronous Digital
Hierarchy (SDH) are standardized multiplexing protocols that transfer
multiple digital bit streams over optical Fibre using lasers.
Asynchronous Transfer Mode(ATM)
 It uses asynchronous time-division multiplexing and encodes data into
small, fixed-sized cells.
 Good choice for a network that handle both traditional high-throughput data
traffic, and real-time, low-latency content such as voice and video.

Types of Networks
1. Personal Area Network (PAN)
2. Local Area Network (LAN)
3. Campus Area Network (CAN)
4. Metropolitan Area Network (MAN)
5. Wide Area Network (WAN)
6. Storage-Area Network (SAN)
7. Virtual Private Network (VPN)
8. Client Server Network
9. Peer to Peer Network (P2P)

1. Personal Area Network
1. Personal Area Network (PAN) is a
computer network used for data
transmission amongst devices such
as computers, telephones, tablets
and personal digital assistants.
2. Also Known as HAN (Home Area
Network)
3. PANs can be used for
communication amongst the
personal devices themselves
(interpersonal communication), or for
connecting to a higher level network
and the Internet (an uplink) where
one "master" device takes up the
role as internet router.

2. Local Area Network
 Xerox Corporation worked in
collaboration with DEC and Intel
to create Ethernet, which is the
most pervasive LAN architecture
used today.
 Ethernet has evolved and has
seen significant improvements in
regard to speed and efficiency.
 An upside of a LAN is fast data transfer with data speed that can reach up
to 10Gbps.
 Other significant LAN technologies are Fiber Distributed Data Interface
(FDDI) and token ring.

3. Campus Area Network
 Larger than LANs, but smaller
than metropolitan area networks
these types of networks are
typically seen in universities, large
K-12 school districts or small
businesses.
 They can be spread across
several buildings that are fairly
close to each other so users can
share resources

4. Metropolitan Area Network
1. A MAN is larger than a LAN but smaller than or equal in size to a WAN.
2. The size range anywhere from 5 to 50km in diameter.
3. MANs are typically owned and managed by a single entity.
4. This could be an ISP or telecommunications company that sells its services to
end-users in that metropolitan area.
5. For all intents and purposes, a MAN has the same characteristics as a WAN
with distance constraints.

5. Wide Area Network
• A Wide Area Network exist over a large area
• Data travels through telephone or cable lines
• Usually requires a Modem
• The world’s largest Wide Area Network in the Internet

6. Storage Area Network
 SAN may be referred to as a Sub network or special purpose network.
 Its special purpose is to allow users on a larger network to connect various
data storage devices with clusters of data servers.
 SANs can be accessed in the same fashion as a drive attached to a server.

7. Virtual Private Network
 VPN is a private network that can access
public networks remotely. VPN uses
encryption and security protocols to
retain privacy while it accesses outside
resources.
 When employed on a network, VPN
enables an end user to create a virtual
tunnel to a remote location. Typically,
telecommuters use VPN to log in to their
company networks from home.
 Authentication is provided to validate the identities of the two peers.
 Confidentiality provides encryption of the data to keep it private from prying
eyes.
 Integrity is used to ensure that the data sent between the two devices or
sites has not been tampered with.

8. Client/Server Network
In a client/server arrangement,
network services are located on a
dedicated computer called a server.
 The server responds to the requests
of clients.
The server is a central computer that
is continuously available to respond to
requests from clients for file, print,
application, and other services.
 Most network operating systems adopt the form of a client/server
relationship.
 Typically, desktop computers function as clients, and one or more
computers with additional processing power, memory, and specialized
software function as servers.

9. Peer to Peer Network
 Usually very small networks
 Each workstation has equivalent capabilities and responsibilities
 Does not require a switch or a hub.
 These types of networks do not perform well under heavy data
loads.

Network Topologies
Network topology defines the structure of the network.
A.Physical topology:- It define the actual layout of the wire or media.
1. Bus
2. Ring
3. Star
4. Tree(Hierarchical)
5. Mesh
B.Logical topology:- It defines how the hosts access the media to send data.
1. Broadcast
2. Token passing
C.Hybrid Topology

1. Bus Topology
T
T
All devices are connected to a central
cable, called bus or backbone.
There are terminators at each end of the
bus that stops the signal and keeps it
from traveling backwards.
Disadvantages:
1.It is possible that more than one station may attempt
transmission simultaneously (collision or contention).
2.Difficult reconfiguration and fault isolation.
3.A fault or break in the bus cable stops all transmission,
even between devices on the same side of the problem.
4.The damaged area reflects signals in the direction of
origin, creating noise in both directions
Advantages:
1.There is no central controller.
2.Control resides in each station
3.The less interconnecting wire is required.
4.Ease of installation.
5.Backbone cable can be laid along the
most efficient path, and then connected to
the nodes by drop lines of various lengths

2. Ring Topology
• All devices are connected to one another in the shape of
a closed loop.
• Each device is connected directly to two other devices,
one on either side of it.
Advantages:
1.Avoids the collisions that are possible in the bus topology.
2.Each pair of stations has a point-to-point connection.
3.A signal is passed along the ring in one direction, from device to another,
until it reaches its destination.
4.Each device incorporates a repeater.
5.Relatively easy to install and reconfigure.
6.Fault isolation is simplified.
Disadvantages:
1.A break in the ring (such as station disabled) can disable the entire
network.
2.Unidirectional traffic.

3. Star Topology
• All devices are connected to a central hub.
• Nodes communicate across the network by passing data
through the hub or switch.
Advantages:
1. Easy to install and reconfigure.
2. Robustness, if one link fails; only that link is affected. All other links
remain active.
3. Easy fault identification and isolation. As long as the hub is working,
it can be used to monitor link problems and bypass defective links.
Disadvantages:
1. The devices are not linked to each other.
2. If one device wants to send data to another, it sends it to the
controller, which then relays the data to the other connected device.

4. Tree/Hierarchical Topology
Advantages:
1.It allows more devices to be attached to a single
central hub and can therefore increase the
distance a signal can travel between devices.
2.It allows the network to isolate and prioritize
communications from different computers.
Disadvantages:
1.The devices are not linked to each other.
2.If one device wants to send data to another, it
sends it to the controller, which then relays the
data to the other connected device.
3.The addition of secondary hubs brings two
further advantages.

6. Mesh Topology
Each host has its connections to all other hosts.
Mesh topology is implemented to provide as much
protection as possible from interruption of service.
1.A nuclear power plant might use a mesh topology in
the networked control systems.
2.Although the Internet has multiple paths to any one
location, it does not adopt the full mesh topology.
Disadvantages:
1. A large amount of cabling required.
2. A large amount of I/O ports required.
3. Installation and reconfiguration are difficult.
4. The sheer bulk of the wiring can be greater
than the available space (in the walls, ceiling,
or floors) can accommodate.
5. The hardware required to connect each link
(I/O ports and cables) can be prohibitively
expensive.
Advantages:
1. The use of dedicated links guarantees that each
connection can carry its data load, thus eliminating the
traffic problems that can occur when links must be
shared by multiple devices.
2. It is robust, if one link becomes unusable, it does not
incapacitate (affect) the entire system.
3. Privacy and Security (every message sent travels
along a dedicated line; only the intended recipient sees
it).
4. Point-to-point links make fault identification and fault
isolation easy.

Types of Networks
• Local Area Network (LAN) – It is a group of network
components that work within small area.
• Wide Area Network (WAN) – It is a group of LANs that are
interconnected within large area.

LAYERED TASKS
LAYERED TASKS
 A network model is a layered architecture
 Task broken into subtasks
 Implemented separately in layers in stack
 Functions need in both systems
 Peer layers communicate
 Protocol:
 A set of rules that governs data communication
 It represents an agreement between the communicating
devices
1.46

Tasks involved in sending a letter
Sender, Receiver, and Carrier
Hierarchy (services)
Topics discussed in this section:
Topics discussed in this section:
1.47

THE OSI MODEL
THE OSI MODEL
Established in 1947, the International Standards
Established in 1947, the International Standards
Organization (
Organization (ISO
ISO) is a multinational body
) is a multinational body
dedicated to worldwide agreement on
dedicated to worldwide agreement on
international standards.
international standards.
An ISO is the Open Systems Interconnection (
An ISO is the Open Systems Interconnection (OSI
OSI)
)
model is the standard that covers all aspects of
model is the standard that covers all aspects of
network communications from ISO. It was first
network communications from ISO. It was first
introduced in the late 1970s.
introduced in the late 1970s.
1.48

Seven layers of the OSI model
Layered Architecture
Layers
Layer 7. Application
Layer 6. Presentation
Layer 5. Session
Layer 4. Transport
Layer 3. Network
Layer 2. Data Link
Layer 1. Physical Sender
Receiver
Layers 1-4 relate to communications technology.
Layers 5-7 relate to user applications.

Layered Architecture
 A layered model
 Each layer performs a subset of the required
communication functions
 Each layer relies on the next lower layer to
perform more primitive functions
 Each layer provides services to the next
higher layer
 Changes in one layer should not require
changes in other layers
 The processes on each machine at a given
layer are called peer-to-peer process

 Communication must move downward through the
layers on the sending device, over the
communication channel, and upward to the receiving
device
 Each layer in the sending device adds its own
information to the message it receives from the layer
just above it and passes the whole package to the
layer just below it
 At the receiving device, the message is unwrapped
layer by layer, with each process receiving and
removing the data meant for it
PEER – TO – PEER PROCESS

PEER – TO – PEER PROCESS
 The passing of the data and network information
down through the layers of the sending device and
backup through the layers of the receiving device is
made possible by interface between each pair of
adjacent layers
 Interface defines what information and services a
layer must provide for the layer above it.

The interaction between layers in the OSI model

An exchange using the OSI model

LAYERS IN THE OSI MODEL
LAYERS IN THE OSI MODEL
1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer

The physical layer is responsible for movements of
individual bits from one hop (node) to the next.
 Function
 Physical characteristics of interfaces and media
 Representation of bits
 Data rate
 Synchronization of bits
 Line configuration (point-to-point or multipoint)
 Physical topology (mesh, star, ring or bus)
 Transmission mode ( simplex, half-duplex or
duplex)
Physical Layer

The data link layer is responsible for moving
frames from one hop (node) to the next.
 Function
 Framing
 Physical addressing
 Flow control
 Error control
 Access control
Data Link Layer

Example 1
Example 1
In following Figure a node with physical address 10 sends a frame to a node
with physical address 87. The two nodes are connected by a link. At the
data link level this frame contains physical addresses in the header. These
are the only addresses needed. The rest of the header contains other
information needed at this level. The trailer usually contains extra bits
needed for error detection

The network layer is responsible for the
delivery of individual packets from
the source host to the destination host.
 Source-to-destination delivery
 Responsible from the delivery of packets from the
original source to the final destination
 Functions
 Logical addressing
 routing
Network Layer

Source-to-destination delivery

Example 2
Example 2
We want to send data from a
node with network address A and
physical address 10, located on
one LAN, to a node with a
network address P and physical
address 95, located on another
LAN. Because the two devices are
located on different networks, we
cannot use physical addresses
only; the physical addresses only
have local influence. What we
need here are universal addresses
that can pass through the LAN
boundaries. The network (logical)
addresses have this characteristic.

The transport layer is responsible for the delivery
of a message from one process to another.
 Process-to- process delivery
 Functions
 Port addressing
 Segmentation and reassembly
 Connection control ( Connection-oriented or connection-
less)
 Flow control
 Error control
Transport Layer

Transport layer
Segmentation and reassembly

Reliable process-to-process delivery of a message

Example 3
Example 3
Data coming from the
upper layers have port
addresses j and k (j is the
address of the sending
process, and k is the
address of the receiving
process). Since the data size
is larger than the network
layer can handle, the data
are split into two packets,
each packet retaining the
port addresses (j and k).
Then in the network layer,
network addresses (A and
P) are added to each
packet.

The session layer is responsible for dialog
control and synchronization.
Session Layer
 It establishes, maintains and synchronize the
interaction between communicating system
 Function
 Dialog control
 Synchronization (checkpoints)

The presentation layer is responsible for translation,
compression, and encryption.
Presentation Layer
 Concerned with the syntax and semantics of the
information exchanged between two system
 Functions
 Translation ( EBCDIC-coded text file  ASCII-coded
file)
 Encryption and Decryption
 Compression

The application layer is responsible for
providing services to the user.
 Functions
 Network virtual terminal (Remote log-in)
 File transfer and access
 Mail services
 Directory services (Distributed Database)
 Accessing the World Wide Web
Application Layer

Summary of layers
OSI Model
Data
unit
Layer Function
User
support
layers
Data
7. Application Network process to application
6. Presentation Data representation and encryption
5. Session Inter-host communication
User
Network
Segment 4. Transport End-to-end connections and reliability
Network
support
layers
Packet 3. Network
Path determination and logical
addressing
Frame 2. Data Link Physical addressing
Bit 1. Physical Media, signal and binary transmission
Sender
Receiver

• Explicit
Presentation and
session layers
missing in Internet
Protocols
• Data Link and
Network Layers
redesigned
Internet Protocols vs OSI
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
TCP
IP
Network Interface
Hardware

• In OSI model, each layer provide services to layer above,
and ‘consumes’ services provided by layer below.
• Active elements in a layer called entities.
• Entities in same layer in different machines called peer
entities.
Services in the OSI Model

• Layer N provides service to layer N+1
Layering Principles
(N+1) Entity
Service User
(N) Entity
Service Provider
(N+1) Entity
Service User
(N) Entity
Service Provider
Layer N Service
Access Point (SAP)
Layer N protocol
N+1
PDU
Layer N+1 protocol
SDU
PDU - Protocol Data Unit
SDU - Service Data Unit
N
PDU
N
PDU

• Layers can offer connection-oriented or connectionless
services.
• Connection-oriented like telephone system.
• Connectionless like postal system.
• Each service has an associated Quality-of-service (e.g.
reliable or unreliable).
Connections

• Reliable services never lose/corrupt data.
• Reliable service costs more.
• Typical application for reliable service is file transfer.
• Typical application not needing reliable service is voice
traffic.
• Not all applications need connections.
Reliability

Packets, Frames, and Headers
• A network packet (also called a datagram) is a formatted unit of data that not only has the information
that is meant to be sent to its destination (the payload) but also contains control information such as
the source and destination address
• . Networks that use packets to send data are called packet switched networks at the Network Layer
(layer 3).
Frames
• Frames are also considered to be a unit of data themselves, and operate at the Data Link layer (layer
2).
• They are very similar to packets in the way the work is constructed, but their structure is different.
Frames are used to transport data on the same network and use source and destination MAC addresses
(discussed in Chapter 5) rather than IP addresses.
• A frame is sent over the network and an Ethernet switch checks the destination address of the frame
against a MAC lookup table in its memory

Headers
•Headers are used as part of the process of packaging of data for transfer over
•network connections. There are two types of headers, and they are TCP and UDP
•(TCP and UDP are discussed in Chapter 6). TCP headers contain 20 bytes while
•UDP headers contain 8 bytes.
•A header can contain the following information:
•The version of IP (IPv4 or IPv6)
•The sender’s IP address
•The receiver’s IP address
•The number of packets in the message
•The protocol being used
•The time to live
•The packet length (if applicable)
•Synchronization data

What is a Collision Domain?
• What is a Collision?
Ethernet uses
CSMA/CD for determining when a
computer is free to transmit data thru
the medium. Using CSMA/CD all
computers monitor the transmission
medium and wait until the medium is
free before transmitting. If two
computers try to transmit at the same
time a collision will occur.
• What is a Collision Domain?
Only one device in the collision
domain may transmit at any one
time, and the other devices in
the domain listen to the network in
order to avoid data collisions.

What is a Broadcast Domain?
• A Broadcast Domain consists of all the
devices that will receive any broadcast
packet originating from any device
within the network segment.
• In the picture, "Computer A" is
sending a broadcast and switch will
forward it to every ports and all the
switches will get a copy of broadcast
packet. Every switch will flood the
broadcast packet to all the ports.
Router also will get a copy of
broadcast packet, but the Router will
not forward the packet to the next
network segment.

ADDRESSING
ADDRESSING
Four levels of addresses are used in an
Four levels of addresses are used in an
internet employing the TCP/IP protocols:
internet employing the TCP/IP protocols:
physical
physical,
, logical
logical,
, port
port, and
, and specific
specific.
.

Relationship of layers and addresses in TCP/IP

Physical addresses are imprinted on the
NIC. Most local-area networks (Ethernet)
use a 48-bit (6-byte) physical address written
as 12 hexadecimal digits; every byte (2
hexadecimal digits) is separated by a colon.
Physical Address
Example:
07:01:02:01:2C:4B
A 6-byte (12 hexadecimal digits) physical
address.

The physical addresses in the datagram may change
from hop to hop.
• known also as the MAC address
• Is the address of a node as defined by its
LAN or WAN
• It is included in the frame used by data link
layer
Physical Address

The physical addresses will change from hop to hop,
but the logical addresses usually remain the same.
 IP addresses are necessary for universal
communications that are independent of physical
network.
 No two host address on the internet can have the
same IP address
 IP addresses in the Internet are 32-bit address that
uniquely define a host.
Logical Address

Port address is a 16-bit address represented by one
decimal number ranged from (0-65535) to choose a
process among multiple processes on the destination
host.
Destination port number is needed for delivery.
Source port number is needed for receiving a reply as an
acknowledgments.
In TCP/IP , a 16-bit port address represented
as one single number. Example: 753
The physical addresses change from hop to hop,
but the logical and port addresses usually remain the same.
Port addresses

Specific addresses
E-mail address (user1@vcet.ac.in)
Universal Resource Locator (URL) (www.vcet.ac.in)
The Domain Name System (DNS) translates human-friendly
computer hostnames ( URL) into IP addresses. For example,
www.example.com is translated to 208.77.188.166

NETWORK FUNDAMENTALS important concepts.ppt

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