TCP/IP is a set of communication protocols used to connect devices on the internet and other networks. It has two main protocols - TCP for reliable transmission of data between devices, and IP for addressing devices and routing packets across networks. TCP/IP uses ports to allow multiple applications to run simultaneously on a single device. Routers use IP addressing and routing tables to determine the best path for sending packets between devices on different networks.
TCP/IP have 5 layers, whereas OSI model have 7 layers in its Model. TCP/IP is known for the secured connection and comunication. I have explained all functions and definitions of layers in TCP/IP Model
Hello People.. Welcome to GURUKULA!!!
Have you ever thought that how the protocols that are required for the effective delivery of the messages from one place to anpther place take place in a real time internet..... This video explains about the concept called PROTOCOL LAYERING, where you can learn the way how the protocols are layered in such a way..
Simple examples are also used to make the concepts clean nd clear.
This video will help you to learn:
What is protocol layering in networks, OSI Model in Computer Networks, Layers of OSI Model, OSI Model, OSI Internet Module, OSI Layers and their Functions, Examples of OSI Models, 7 layers of OSI Models, Principles of Protocol Layering, Why layering the Protocols,
Thanks for Watching, Keep Supporting and Keep Sharing...
TCP/IP have 5 layers, whereas OSI model have 7 layers in its Model. TCP/IP is known for the secured connection and comunication. I have explained all functions and definitions of layers in TCP/IP Model
Hello People.. Welcome to GURUKULA!!!
Have you ever thought that how the protocols that are required for the effective delivery of the messages from one place to anpther place take place in a real time internet..... This video explains about the concept called PROTOCOL LAYERING, where you can learn the way how the protocols are layered in such a way..
Simple examples are also used to make the concepts clean nd clear.
This video will help you to learn:
What is protocol layering in networks, OSI Model in Computer Networks, Layers of OSI Model, OSI Model, OSI Internet Module, OSI Layers and their Functions, Examples of OSI Models, 7 layers of OSI Models, Principles of Protocol Layering, Why layering the Protocols,
Thanks for Watching, Keep Supporting and Keep Sharing...
INTRODUCTION
WHAT IS OSI?
OSI MODEL
TYPES OF LAYERS
PHYSICAL LAYER
DATA LINK LAYER
NETWORK LAYER
TRANSPORT LAYER
SESSION LAYER
PRESENTATION LAYER
APPLICATION LAYER
The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between adjacent network nodes in a wide area network (WAN) or between nodes on the same local area network (LAN) segment.
Although the OSI reference model is universally recognized, the historical and technical open standard of the Internet is Transmission Control Protocol / Internet Protocol (TCP/IP).
The TCP/IP reference model and the TCP/IP protocol stack make data communication possible between any two computers, anywhere in the world, at nearly the speed of light.
INTRODUCTION
WHAT IS OSI?
OSI MODEL
TYPES OF LAYERS
PHYSICAL LAYER
DATA LINK LAYER
NETWORK LAYER
TRANSPORT LAYER
SESSION LAYER
PRESENTATION LAYER
APPLICATION LAYER
The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between adjacent network nodes in a wide area network (WAN) or between nodes on the same local area network (LAN) segment.
Although the OSI reference model is universally recognized, the historical and technical open standard of the Internet is Transmission Control Protocol / Internet Protocol (TCP/IP).
The TCP/IP reference model and the TCP/IP protocol stack make data communication possible between any two computers, anywhere in the world, at nearly the speed of light.
The secret of TCP/IP and how it affects your PBXOlle E Johansson
The PBX was invited more than 50 years ago, SIP over 10 years. And we still just implement ISDN over IP. Time for a reboot, time to raise the bar and use the standards that has been developed during the last 10 years.
This talk, originally presented at Voip2day + ElastixWorld in Madrid 2012, presents the Edvina SIP 2012 reference profile, the thoughts behind it and where we are heading.
In this presentation, we will discuss in details about the TCP/ IP framework, the backbone of every ebusiness.
To know more about Welingkar School’s Distance Learning Program and courses offered, visit:
http://www.welingkaronline.org/distance-learning/online-mba.html
The TCP/IP protocol suite has a number of vulnerability and security flaws inherent in the protocols. Those vulnerabilities are often used by crackers for Denial of Service (DOS) attacks, connection hijacking and other attacks. The following are the major TCP/IP security problems:
TCP SYN attacks (or SYN Flooding) ¡§CThe TCP uses sequence numbers to ensure data is given to the user in the correct order. The sequence numbers are initially established during the opening phase of a TCP connection in the three-way handshake. TCP SYN attacks take advantage of a flaw in how most hosts implement TCP three-way handshake. When Host B receives the SYN request from A, it must keep track of the partially opened connection in a "listen queue" for at least 75 seconds and a host can only keep track of a very limited number of connections. A malicious host can exploit the small size of the listen queue by sending multiple SYN requests to a host, but never replying to the SYN&ACK the other host sends back. By doing so, the other host's listen queue is quickly filled up, and it will stop accepting new connections, until a partially opened connection in the queue is completed or times out. This ability to effectively remove a host from the network for at least 75 seconds can be used as a denial-of-service attack, or it can be used to implement other attacks, like IP Spoofing.
IP Spoofing - IP spoofing is an attack used to gain unauthorized access to computers, whereby the attacker sends messages to a computer with a forging IP address indicating that the message is coming from a trusted host. The IP layer assumes that the source address on any IP packet it receives is the same IP address as the system that actually sent the packet -- it does no authentication. Many higher level protocols and applications also make this assumption, so it seems that anyone able to forge the source address of an IP packet could get unauthorized privileges. There are few variations of IP Spoofing such as Blind and Non-blind spoofing, man-in-the-middle- attack (connection hijacking), etc. For details, please read the IP Spoofing section.
Routing attacks ¡§C This attack takes advantage of Routing Information Protocol (RIP), which is often an essential component in a TCP/IP network. RIP is used to distribute routing information within networks, such as shortest-paths, and advertising routes out from the local network. Like TCP/IP, RIP has no built in authentication, and the information provided
in a RIP packet is often used without verifying it. Attacks on RIP change where data goes to, not where it came from. For example, an attacker could forge a RIP packet, claiming his host "X" has the fastest path out of the network. All packets sent out from that network would then be routed through X, where they could be modified or examined. An attacker could also use RIP to effectively impersonate any host, by causing all traffic sent to that host to be sent to the attacker's machine
The TCP/IP protocol system is used by virtually every modern data network to quickly and reliably move data from node to node. This presentation covers what TCP/IP is, what it does, it’s most important features, and how it was developed.
it is a precise and well designed presentation regarding the topic "IP SPOOFING".It can be useful for any computer science student seeking a good topic for papre presentation.
TCP/IP Protocol Suite model Transmission Control Protocol27230106
TCP/IP is a set of protocols developed to allow cooperating computers to share resources across a network
TCP stands for “Transmission Control Protocol”
IP stands for “Internet Protocol”
They are Transport layer and Network layer protocols respectively of the protocol suite
The most well known network that adopted TCP/IP is Internet – the biggest WAN in the world
Slides for a college course at City College San Francisco. Based on "Hands-On Ethical Hacking and Network Defense, Third Edition" by Michael T. Simpson, Kent Backman, and James Corley -- ISBN: 9781285454610.
Instructor: Sam Bowne
Class website: https://samsclass.info/123/123_S17.shtml
Title Slide:
Title: Introduction to TCP/IP Networking
Subtitle: Understanding the Backbone of the Internet
Slide 1: Introduction to TCP/IP:
Brief overview of TCP/IP.
Explanation of its importance as the fundamental protocol suite of the Internet.
Slide 2: TCP/IP Layers:
Explanation of the four layers of the TCP/IP model: Link, Internet, Transport, and Application.
Briefly describe the purpose of each layer.
Slide 3: IP Addressing:
Explanation of IP addresses and their role in uniquely identifying devices on a network.
Differentiation between IPv4 and IPv6.
Slide 4: Subnetting:
Introduction to subnetting in TCP/IP networks.
Purpose and benefits of subnetting.
Slide 5: TCP (Transmission Control Protocol):
Overview of TCP and its role as a reliable, connection-oriented protocol.
Explanation of features like error checking, flow control, and sequencing.
Slide 6: UDP (User Datagram Protocol):
Overview of UDP and its role as a connectionless, lightweight protocol.
Comparison with TCP.
Slide 7: Ports and Sockets:
Explanation of ports and sockets in TCP/IP.
Role in enabling communication between applications.
Slide 8: DNS (Domain Name System):
Overview of DNS and its role in translating human-readable domain names into IP addresses.
Importance of DNS in Internet communication.
Slide 9: DHCP (Dynamic Host Configuration Protocol):
Explanation of DHCP and its role in dynamically assigning IP addresses to devices on a network.
Benefits of DHCP.
Slide 10: Routing and Routers:
Overview of routing in TCP/IP networks.
Role of routers in directing data between networks.
Slide 11: Security in TCP/IP:
Introduction to security considerations in TCP/IP networks.
Briefly cover topics like firewalls, VPNs, and encryption.
Slide 12: Future Trends:
Brief discussion on emerging technologies and trends in TCP/IP.
Topics like IoT (Internet of Things) and 5G.
Slide 13: Conclusion:
Summary of key points.
Emphasis on the ubiquity and importance of TCP/IP in modern networking.
An operating system (OS) is a software program that manages the resources of a computer system and provides a platform for running applications. Its primary functions include resource management, process management, memory management, file system management, and user interface. There are many different types of operating systems, such as desktop operating systems like Windows and macOS, server operating systems like Linux and Windows Server, and embedded operating systems like those used in mobile phones and other small devices. The choice of operating system depends on the type of device, the intended use, and other factors.
What is a Database?
Database creation steps
Benefits of using Database
Types of Table Relationships
What is a Database model
Database Management System
Users of Database
MS Access
Program, Language, & Programming Language
Object Oriented Programming vs Procedure Oriented Programming
About C
Why still Learn C?
Basic Terms
C Stuff
C Syntax
C Program
Algorithm
What is an algorithm?
How are mathematical statements and algorithms related?
What do algorithms have to do with computers?
Pseudo Code
What is pseudocode?
Writing pseudocode
Pseudo Code vs Algorithm
Components of Data Communication
Characteristics of Data Transmission
Communication Media
Communication Speed
Communication Hardware
Communication Software
OSI Model
Introduction
Syed Zaid Irshad
Rules (that You have to Follow)
Book Introduction
10 Chapters
Theoretical Chapters are 6
Practical Chapters are 4
Chapter 1: Basic Concept of Information Technology
Introduction of Computer
Definition
Characteristics
Parts of Computer
Input
Output
Memory
Primary Storage
Secondary Storage
Ports
Language Translator
Compiler
Interpreter
Generations of Programming Language
Ages of Computers
Generations of Computer
Classification of Computers
Chapter 2: Information Networks
Types of Network
LAN
WAN
MAN
GAN
Topologies
Star
Ring
Bus
Hybrid
File Transfer Protocol
World Wide Web
Chapter 3: Data Communication
Standards
Transmission
Simples
Half Duplex
Full Duplex
Media
Twisted Pair Cable
Coaxial Cable
Fiber Optic Cable
Microwave Transmission
Satellite Transmission
Open Systems Interconnection model (OSI model)
Chapter 4: Applications and Use of Computers
Difference Between Application and Use
Impacts of Computers
Chapter 5: Computer Architecture
Address of Memory Locations
Instruction Format
Fetch and Execute
Chapter 6: Security, Copyright and The Law
Computer Crime
Computer Viruses
Computer Privacy
Software Piracy and Law
Chapter 7: Operating System
User Interface
Graphical User Interface
Operating Systems
Chapter 8: Word Processing
Introduction to MS Word
Creating
Editing
Formatting
Printing
Chapter 9: Spreadsheet
Introduction to MS Excel
Creating
Editing
Formatting
Printing
Formulae
Project
Chapter 10: Internet Browsing and Using E-mail
Create Email ID
Send Mail
Download File
Upload File
Study Plan
Every Tuesday we perform Practical
Every Friday Half of the Lecture will be used as question answer session
Rest of the days are for Theoretical Stuff
Make WhatsApp Group for class where we can share stuff related to the Subject
1st Year Computer Science Book
Sindh Text Book Board Introduction
Introduction
Syed Zaid Irshad
Rules (that You have to Follow)
Book Introduction
10 Chapters
Theoretical Chapters are 6
Practical Chapters are 4
Chapter 1: Basic Concept of Information Technology
Introduction of Computer
Definition
Characteristics
Parts of Computer
Input
Output
Memory
Primary Storage
Secondary Storage
Ports
Language Translator
Compiler
Interpreter
Generations of Programming Language
Ages of Computers
Generations of Computer
Classification of Computers
Chapter 2: Information Networks
Types of Network
LAN
WAN
MAN
GAN
Topologies
Star
Ring
Bus
Hybrid
File Transfer Protocol
World Wide Web
Chapter 3: Data Communication
Standards
Transmission
Simples
Half Duplex
Full Duplex
Media
Twisted Pair Cable
Coaxial Cable
Fiber Optic Cable
Microwave Transmission
Satellite Transmission
Open Systems Interconnection model (OSI model)
Chapter 4: Applications and Use of Computers
Difference Between Application and Use
Impacts of Computers
Chapter 5: Computer Architecture
Address of Memory Locations
Instruction Format
Fetch and Execute
Chapter 6: Security, Copyright and The Law
Computer Crime
Computer Viruses
Computer Privacy
Software Piracy and Law
Chapter 7: Operating System
User Interface
Graphical User Interface
Operating Systems
Chapter 8: Word Processing
Introduction to MS Word
Creating
Editing
Formatting
Printing
Chapter 9: Spreadsheet
Introduction to MS Excel
Creating
Editing
Formatting
Printing
Formulae
Project
Chapter 10: Internet Browsing and Using E-mail
Create Email ID
Send Mail
Download File
Upload File
Study Plan
Every Tuesday we perform Practical
Every Friday Half of the Lecture will be used as question answer session
Rest of the days are for Theoretical Stuff
Make WhatsApp Group for class where we can share stuff related to the Subject
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
AIRCRAFT GENERAL
The Single Aisle is the most advanced family aircraft in service today, with fly-by-wire flight controls.
The A318, A319, A320 and A321 are twin-engine subsonic medium range aircraft.
The family offers a choice of engines
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
2. 2
A. What is TCP/IP?
• TCP/IP is a set of protocols developed to allow
cooperating computers to share resources across a
network
• TCP stands for “Transmission Control Protocol”
• IP stands for “Internet Protocol”
• They are Transport layer and Network layer
protocols respectively of the protocol suite
• The most well known network that adopted
TCP/IP is Internet – the biggest WAN in the world
3. 3
• A protocol is a collection of rules and procedures
for two computers to exchange information
• Protocol also defines the format of data that is
being exchanged
What is a protocol?
4. 4
Why TCP/IP is so popular?
• TCP/IP was developed very early
• Technologies were widely discussed and circulated
in documents called “Request for Comments”
(RFC) – free of charge
• Supported by UNIX operating system
5. 5
TCP/IP Model
• Because TCP/IP was developed earlier than the
OSI 7-layer mode, it does not have 7 layers but
only 4 layers
OSI 7-layerTCP/IP Protocol Suite
FTP, SMTP, Telnet,
HTTP,…
TCP, UDP
IP, ARP, ICMP
Network Interface
6. 6
• Application layer protocols define the rules when
implementing specific network applications
• Rely on the underlying layers to provide accurate
and efficient data delivery
• Typical protocols:
• FTP – File Transfer Protocol
• For file transfer
• Telnet – Remote terminal protocol
• For remote login on any other computer on the
network
• SMTP – Simple Mail Transfer Protocol
• For mail transfer
• HTTP – Hypertext Transfer Protocol
• For Web browsing
7. 7
• TCP/IP is built on “connectionless” technology,
each datagram finds its own way to its destination
• Transport Layer protocols define the rules of
• Dividing a chunk of data into segments
• Reassemble segments into the original chunk
• Typical protocols:
• TCP – Transmission Control Protocol
• Provide further the functions such as reordering
and data resend
• UDP – User Datagram Service
• Use when the message to be sent fit exactly into a
datagram
• Use also when a more simplified data format is
required
8. 8
• Network layer protocols define the rules of how to
find the routes for a packet to the destination
• It only gives best effort delivery. Packets can be
delayed, corrupted, lost, duplicated, out-of-order
• Typical protocols:
• IP – Internet Protocol
• Provide packet delivery
• ARP – Address Resolution Protocol
• Define the procedures of network address / MAC
address translation
• ICMP – Internet Control Message Protocol
• Define the procedures of error message transfer
11. 11
• The underlying layers have guaranteed accurate
data delivery
• We need to make a lot agreements with the server
in application layer before sending mail
1. Agree on how data is represented
• Binary or ASCII
2. Ensure the right recipient
• There may be 1000 users served by the server
3. Ensure the client has the right to send mail
• Some clients are not welcome
4. How to tell the server it is the end of the message
• All mail looks the same
:
12. 12
• Example: SMTP
The following mail is to be sent:
Date: Fri, 18 Jan 02 13:26:31 EDT
From: enpklun@polyu.edu.hk
To: tchsun@eee.hku.hk
Subject: meeting
Let’s get together Monday at 1pm.
13. 13
SMTP ServerClient
access port 25 of server
HELO polyu.edu.hk
MAIL From:
<enpklun@polyu.edu.hk>
220 eee.hku.hk SMTP Service
at 20 Jan 02 05:17:18 EDT
250 eee.hku.hk – Hello,
polyu.edu.hk
250 MAIL accepted
14. 14
Client SMTP Server
Date: Fri, 18 Jan 02 13:26:31 EDT
From: enpklun@polyu.edu.hk
To: tchsun@eee.hku.hk
Subject: meeting
Let’s get together Monday at 1pm.
.
RCPT To:<tchsun@eee.hku.hk>
DATA
250 Recipient accepted
354 Start mail input;
end with .
15. 15
• The agreement made in the SMTP protocol
• All messages use normal text
• All ASCII characters
• The responses all begin with numbers
• To indicate the status when receiving the command
• Some words are reserved words
• HELO, MAIL, RCPT…
• Mail ends with a line that contains only a period
• The information passed with the SMTP messages
• The recipient name
• The sender name
• The mail
16. 16
C. Domain Name (mentioned before)
• Every computer has a network address
• e.g. 158.132.161.99
• To access a computer, we need to specify its
network address
• Human beings are weak in memorizing numbers
• We prefer computer name or domain name
• e.g. hkpu10.polyu.edu.hk
• Need a machine on the Internet to convert name to
number
17. 17
Domain name hierarchy
Example:
hkpu10.polyu.edu.hk
Root domain name
other examples:
com – commercial company
org – general organization
net – major network centre
gov – government org.
mil – militrary group
edu – education org.
•The domain
within hk
•Note: edu.hk
is not the
same as edu
•The domain
within edu.hk
•One of the
educational
institutions in
H.K.
Computer name
18. 18
• An organization needs to register its domain name
• e.g. PolyU has registered its name to the domain
of edu.hk
• Once a domain name is assigned, the organization
is free to assign other names belong to its domain
• e.g. we can have
hkpu10.polyu.edu.hk
smtp.polyu.edu.hk
mail.polyu.edu.hk
19. 19
Client
Domain Name Server
(DNS) of polyu.edu.hk
Address of
www.yahoo.com
Where is
www.yahoo.com?
usually UDP
DNS of com
DNS of Yahoo.com
Where is
www.yahoo.com?
Address of
www.Yahoo.com
Where is
yahoo.com? Address of the
DNS of
Yahoo.com
Become
client
20. 20
• Nevertheless, such a complicated procedure needs
not perform in most cases
• Client computers usually remember the answers
that it got before
• It reduces the loading to the root DNS
• To further reduce loading, there can be many root
DNS on the Internet
• e.g. there are a few “com” root DNS
22. 22
D. TCP and UDP
• TCP is a connection-oriented protocol
• Does not mean it has a physical connection between
sender and receiver
• TCP provides the function to allow a connection
virtually exists – also called virtual circuit
• TCP provides the functions:
• Dividing a chunk of data into segments
• Reassembly segments into the original chunk
• Provide further the functions such as reordering and
data resend
• Offering a reliable byte-stream delivery service
TCP – Transmission Control Protocol
25. 25
• A Typical Procedure
• Sender
• TCP divides a message into segments
• Add sequence no.
• Send the segments in sequence and wait for
acknowledgement
• If an acknowledgement for a segment is not received
for a certain period of time, resend it until an
acknowledgement is received
• Recipient
• When receiving segments, send the
acknowledgement with correct number
• Reassembly the segments back to the message
26. 26
• A computer may perform a number of network
applications at the same time
• FTP + SMTP + HTTP, etc.
• Each computer has only one network address, how
can it serve so many applications at the same time?
Port Multiplexing
⇒ by port multiplexing
Network add:
158.132.161.99
Port 21 Port 25
Port 80
FTP SMTP
HTTP
27. 27
Well-known Port Numbers
• Some port numbers are reserved for some
purposes
• Port 21: FTP – file transfer
• Port 25: SMTP – mail transfer
• Port 23: TELNET – remote login
• Port 80: HTTP – Web access
• These port numbers are well known to all
computers in the network
• E.g. whenever a client access port 25 of the server,
it means the client needs SMTP service
28. 28
Client SMTP Server
Located by: network
address + TCP port
no.
Source Port
= 1357
Destination
Port = 25
Sequence Number
Acknowledgement
Number
Checksum
Message Data
SMTP port
= 1357
SMTP port
= 25
29. 29
Client A SMTP + FTP Server
Client B
SMTP port
= 1357
FTP port
= 1361
Network address:
158.132.161.99
SMTP port
= 25
FTP port
= 21
31. 31
E. Network Addresses and
Subnets
• A header is added to each segment in the
Network layer
IP3
Total
Length
Time to
Live
Protocol Header
CheckSum
Source Address
Destination Address
Segment
Segment
32. 32
• Total Length – Total length of a packet (up to
65535 bytes)
• Time to Live – How many times this packet can
be routed on the network (up to 255)
• Protocol – The transport layer protocol that
the packet belongs to
• TCP: 6
• UDP: 17
• ICMP: 1
• Source address – the network address of the
computer that sends the data
• Destination address – the network address of
the computer that the data is sending to
33. 33
• (Already mentioned)
• Each computer (host) must have a unique
network address (or IP address for TCP/IP suite)
• Each IP address is 32-bit long (four bytes)
• The four-byte address is written out as a.b.c.d
• e.g. Byte 1 Byte 2 Byte 3 Byte 4
158 132 161 99
• IP addresses are hierarchical
• network I.D. and host I.D.
• Each Network I.D. on the Internet needs to be
registered to the Internet Assigned Number
Authority
34. 34
Net I.D.
Class A – for very large network
Host I.D.0
1 bit 7 bits 24 bits
• Only 27
(63) networks can belong to this class
• Each network, there are 224
hosts or computers
• Very few class A networks in the world
• e.g. Arpanet – the earliest packet switched
WAN (started 40 years ago)
35. 35
Net I.D.
Class B – for medium size network
Host I.D.0
2 bits 14 bits 16 bits
• 214
(16384) networks can belong to this class
• Each network, there are 216
(65536) hosts or
computers
• Polyu’s address belongs to this group
• e.g. 158.132.14.1
1
1001 1110 1000 0100 0000 1110 0000 0001
Network I.D. Host I.D.
36. 36
Class C – for small network
Net I.D. Host I.D.0
3 bits 21 bits 8 bits
• 221
networks can belong to this class
• Each network, there are only 28
(256) hosts or
computers
11
37. 37
Class D – for multicast network
Group no.0
4 bits 28 bits
• Packets are addressed to a multicast group
• Not often supported on Internet
111
38. 38
Special Addresses
• Host I.D. = all ‘1’s ⇒ Directed broadcast
“Broadcast to all hosts in the network or
subnetwork”, not assigned
• Host I.D. = all ‘0’s ⇒ “This network”, not
assigned
• Network I.D. = 127 is reserved for loopback and
diagnostic purposes, not assigned
• Network I.D. + Host I.D. = all ‘1’s ⇒ Limited
broadcast
“Broadcast to all hosts in the current network”,
not assigned
39. 39
Subnets
• A class B address can have 65536 hosts
• Difficult to manage
• Usually subdivide into a few small subnets
• Subnetting can also help to reduce broadcasting
traffic
All traffic to
158.132.0.0
158.132.0.0
Total 65536 hosts
Router Router
All traffic to
158.132.0.0
158.132.1.0
158.132.2.0
158.132.3.0
Each subnet 256 hosts
40. 40
Subnet Mask
• How does the router know which subnet a packet
should go?
• For each interface of the router, a subnet mask is
provided to redefine which part of the address is
Net ID and which part is Host ID
• Become classless addressing
A subnet mask: 255.255.255.0
1111 1111.1111 1111. 1111 1111. 0000 0000
‘1’s Net ID ‘0’s Host ID
42. 42
F. Routing
• How a packet finds its way to a computer in a
network?
• By using Routers
• Routing is the selection of a path to guide a
packet from the source to the destination
• Criteria in selecting a path may be:
• Shortest path
• Quickest path
• Cheapest path
44. 44
• Each router has a table that records the
estimated distance to all other routers
• If a router knows the entire network topology,
the shortest path can be calculated
• To achieve this, routers broadcast Link State
Advertisement to all other routers periodically
• By means of routing protocol
• Each router knows the exact topology, and
then calculates the shortest path
• In practice, it is not possible for a router to all
paths. Only the nearer ones are kept
• Hence can give wrong estimation
45. 45
Host A
158.132.148.66
Default gateway: Router C
Host B
160.64.123.98
Router C
S0
T1
T1
S1
T0
S1
S1
T0
S0
T0
T0
Router A
Subnet
160.64.123.0
Router B
Routing Table
Subnet
158.132.166.0
S1 158.132.166.0
255.255.255.0
Direct
T1 160. 64. 0. 0
255.255. 0. 0
Forward
Subnet
160.64.124.0
Routing Table
S0
S0
S1
160. 64.124.0
255.255.255.0
160. 64.123.0
255.255.255.0
Direct
Direct
46. 46
1. Host A wants to send a packet to Host B with address
160.64.123.98
2. Host A checks that 160.64.123.98 is not in the same
network
3. Send packet to default gateway (Router C)
4. Default gateway finds that it cannot provide the best
route for the packet, inform Host A to send the
packet to Router A next time
5. Router C sends the packet to Router A
6. Router A checks from the table the packet should
forward to Router B
7. Router B receives the packet and checks in its table
the packet should directly deliver to subnet
160.64.123.0
8. Host B (160.64.123.98) receives the packet
47. 47
Data Link and
Physical Layers
Application
Transport
Network
Network Interface
Message
Segments
h M h M h M
h Mh h Mh h Mh
Packets
h Mh h Mhh h
Frames
48. 48
G. Ethernet Encapsulation and
ARP
• An IP packet should be encapsulated into a
frame for transmission by data link layer
• e.g. if Ethernet (or IEEE 802.3) is used:
Preamble Des. Add Sour. Add Length IP Packet FCS
7
Bytes
2/6
Bytes
2/6
Bytes
2
Bytes
46 - 1500 Bytes 4
Bytes
1
Byte
IEEE 802.3 Frame
49. 49
• Only the hardware address (MAC address) is
unique to a host
• Need to convert a network address to MAC
address
Ethernet
Ethernet
Frame
Ethernet address = ?
Packet
Destination IP = 158.132.148.132Source IP =
158.132.148.66
Packet
50. 50
ARP – Address Resolution Protocol
1. Broadcast: Who has got IP address
158.132.148.132? What’s your
Ethernet address?
2. Reply: I do. My Ethernet address is
00-60-8C-41-37-52
Case 1
Ethernet Frame3.
Ethernet address = 00-60-8C-41-37-52
51. 51
ARP – Address Resolution Protocol
Case 2
1. Broadcast: Who has got IP address
158.132.148.132? What’s your
Ethernet address?
2. Reply: The IP you indicated is not in your network.
You can give the packet to me first. My MAC address
is 00-60-8C-12-34-56
Router
3.
Ethernet Frame
Ethernet address = 00-60-8C-12-34-56
52. 52
ARP Cache
• Will have a heavy traffic if so many ARP
broadcast messages are generated
• Each host will have a cache to store the
mappings (from IP to MAC address) that were
obtained before
• An entry will only be kept in the cache for a
limited amount of time (say, 2 minutes)
IP Address MAC Address
158.132.148.80 00-60-8C-27-35-9A
158.132.148.28 02-60-8C-1A-37-49