This document provides an overview of the CIS 3360: Security in Computing course being taught by Cliff Zou in Spring 2012. The objectives of the course are to obtain basic knowledge of computer networking, the Internet, network applications and protocols like TCP/IP. It introduces some key concepts like the layered Internet protocol stack, packet switching, and the hierarchical structure of the Internet as a network of networks consisting of end systems, routers, and communication links. Example applications and protocols for each layer are also discussed at a high level.
A computer network is a collection of interconnected devices that can communicate with each other to share resources and information. These devices can include computers, servers, routers, switches, printers, and more. Networks can vary in size and complexity, from small local networks within a home or office to vast global networks like the internet.
The document provides an overview of computer networks and the Internet by introducing key concepts and terminology. It describes the Internet as a network of networks that interconnects millions of computing devices and communication links. Protocols control the sending and receiving of messages and define how network entities communicate. The network is organized into layers with different protocols at each layer, known as the Internet protocol stack.
This document discusses network access and physical media. It begins by defining the network edge as consisting of end systems or hosts that run applications. It then describes various access network types for connecting hosts, including DSL, cable, fiber, wireless networks, and mobile networks. It also covers the different physical media used for communication links, such as twisted pair copper wire, coaxial cable, fiber optic cable, and wireless radio spectrum.
This document provides an overview of computer networks and the Internet. It describes the nuts and bolts view of the basic components including end systems, communication links, routers, packets, and protocols. It also describes the service oriented view in which the Internet provides distributed applications with either a connection oriented reliable service or a connectionless unreliable service. Finally, it discusses network cores including circuit switching which reserves bandwidth for a call, and packet switching which transmits data in packets and allows statistical multiplexing and sharing of bandwidth.
The document discusses the history and applications of computer networks. It describes how computers can be connected together to share resources and information. Key aspects covered include common network uses like resource sharing, information sharing, communication and e-commerce. The client-server model and examples like web browsers and email clients are also summarized.
The document discusses fundamentals of computer networking, including definitions of key terms like networks, protocols, and packet switching. It explains networking concepts such as the layered OSI model and TCP/IP stacks. Examples of different types of networking devices, protocols, and technologies are provided such as Ethernet, IP addressing, DNS, WiFi, and Bluetooth.
The document discusses an introduction chapter from a computer networking textbook, covering topics such as what the Internet is, network structure including the edge, core, and access networks, protocols, and a brief history of the Internet. It provides an overview of key concepts and terms in computer networking and outlines the structure and content of the introduction chapter.
The document discusses slides created by authors JFK and KWR for their networking textbook. It states that the slides can be freely used and modified by others as long as the source and copyright are mentioned if used substantially unaltered or posted online. The authors thank readers for using the slides and enjoying them.
A computer network is a collection of interconnected devices that can communicate with each other to share resources and information. These devices can include computers, servers, routers, switches, printers, and more. Networks can vary in size and complexity, from small local networks within a home or office to vast global networks like the internet.
The document provides an overview of computer networks and the Internet by introducing key concepts and terminology. It describes the Internet as a network of networks that interconnects millions of computing devices and communication links. Protocols control the sending and receiving of messages and define how network entities communicate. The network is organized into layers with different protocols at each layer, known as the Internet protocol stack.
This document discusses network access and physical media. It begins by defining the network edge as consisting of end systems or hosts that run applications. It then describes various access network types for connecting hosts, including DSL, cable, fiber, wireless networks, and mobile networks. It also covers the different physical media used for communication links, such as twisted pair copper wire, coaxial cable, fiber optic cable, and wireless radio spectrum.
This document provides an overview of computer networks and the Internet. It describes the nuts and bolts view of the basic components including end systems, communication links, routers, packets, and protocols. It also describes the service oriented view in which the Internet provides distributed applications with either a connection oriented reliable service or a connectionless unreliable service. Finally, it discusses network cores including circuit switching which reserves bandwidth for a call, and packet switching which transmits data in packets and allows statistical multiplexing and sharing of bandwidth.
The document discusses the history and applications of computer networks. It describes how computers can be connected together to share resources and information. Key aspects covered include common network uses like resource sharing, information sharing, communication and e-commerce. The client-server model and examples like web browsers and email clients are also summarized.
The document discusses fundamentals of computer networking, including definitions of key terms like networks, protocols, and packet switching. It explains networking concepts such as the layered OSI model and TCP/IP stacks. Examples of different types of networking devices, protocols, and technologies are provided such as Ethernet, IP addressing, DNS, WiFi, and Bluetooth.
The document discusses an introduction chapter from a computer networking textbook, covering topics such as what the Internet is, network structure including the edge, core, and access networks, protocols, and a brief history of the Internet. It provides an overview of key concepts and terms in computer networking and outlines the structure and content of the introduction chapter.
The document discusses slides created by authors JFK and KWR for their networking textbook. It states that the slides can be freely used and modified by others as long as the source and copyright are mentioned if used substantially unaltered or posted online. The authors thank readers for using the slides and enjoying them.
The document summarizes key concepts in internetworking including protocol layering, encapsulation, and different types of network devices like hubs, bridges, and routers. It describes how the Internet Protocol (IP) allows interconnection of different networks by providing a global addressing scheme and best-effort delivery of packets across interconnected networks.
1. The document discusses basic networking concepts including protocols, protocol layers, and network interconnection. It provides details on network addressing, the Domain Name System, and port numbers.
2. Key protocol layers are examined, including the OSI 7-layer model and the TCP/IP 4-layer model. The roles and functions of each layer are defined.
3. Types of networks like WANs, LANs, Ethernet, Token Ring, and FDDI are introduced along with examples of interconnection devices like bridges, routers, and gateways.
The document summarizes key concepts in internetworking including protocol layering, encapsulation, and different types of network devices like hubs, bridges, and routers. It describes how the Internet Protocol (IP) allows interconnection of different networks by providing a global addressing scheme and best-effort delivery of packets between hosts.
A computer network connects independent computers that communicate over a shared network medium. The basic components of a network include at least two computers (servers or clients), networking interface cards, a connection medium like cables, and network operating system software. There are different types of networks including LANs, WANs, intranets, and the Internet. The OSI model defines seven layers of network functionality from the physical layer up to the application layer. TCP/IP is an open networking model used on the Internet with layers including physical, internet, and transport layers.
This document contains lecture notes on fundamentals of computer systems from Dr. Atif Shahzad. It covers topics such as logic, Boolean algebra, memory, CPU, registers, fetch-execute cycle, file management, networking, OSI model, LAN, WAN, communication protocols, latency, capacity, broadcast, firewalls, and network speeds. The document provides definitions and explanations of key computer science concepts.
The document provides an overview of the key topics that will be covered in Chapter 1 of the textbook "Computer Networking: A Top Down Approach". It outlines the major sections that will be discussed including what the Internet is, the structure of networks including the network edge, core, and hierarchy. It also summarizes that delay, loss, throughput, protocol layers, security, and history will be covered. The goal is to provide an introduction and "feel" for computer networking concepts and terminology that will be explored in more depth throughout the course.
This document provides an overview of IP networking and TCP/IP basics. It discusses the origins of TCP/IP in the ARPANET project and the distributed network design. It describes the OSI model and compares it to the TCP/IP architecture. It also covers IP addressing and numbering, client-server architecture, IP forwarding, and some common network troubleshooting tools.
ip net basic understanding slide show pptlolo749806
This document provides an overview of IP networking and TCP/IP basics. It discusses the origins of TCP/IP from the ARPANET project in the 1960s and its distributed network design. It also describes the OSI model and how TCP/IP maps to it, with layers for the application, transport, internet, and link levels. Finally, it covers client-server architecture and IP addressing fundamentals like public and private address spaces.
Jaimin chp-1 - introduction - 2011 batchJaimin Jani
The document summarizes the key topics covered in Chapter 1 of the book "Computer Networks, Fourth Edition" by Andrew S. Tanenbaum. It discusses the seven-layer OSI reference model and the five-layer TCP/IP reference model as the two main models for organizing computer network software. It also briefly describes the different layers of each model and compares the OSI and TCP/IP models.
The document provides an overview of computer networks and the Internet from multiple perspectives:
1) It describes the "nuts and bolts" view of the Internet as millions of connected devices communicating over physical links using packet switching and protocols.
2) It outlines a "service view" of the Internet as infrastructure providing services to applications like the web and email.
3) It introduces the concept of network protocols that govern all communication and defines common protocols like TCP and IP.
The document summarizes the history and development of Ethernet and TCP/IP networking protocols. It describes how ARPANET originally used packet switching in the 1960s, the development of TCP and IP in the 1970s, and how Ethernet was implemented as a standard for local area networks. It also provides an overview of how IP, TCP and common applications like HTTP operate and interconnect across network layers.
This document discusses computer networking and the OSI model. It provides an overview of how computers communicate at different layers, from the physical layer up to the application layer. It also discusses protocols like TCP/IP and how they map to the OSI model. The document compares OSI to the TCP/IP protocol suite and provides examples of protocols that operate at each layer.
The document provides information about the CCNA (Cisco Certified Network Associate) certification exam, including its introduction, syllabus, fees, number of questions, passing marks, and exam structure over two exams. It also includes summaries of the OSI reference model and TCP/IP model, which define standards for network communication and how data is packaged and transmitted between devices.
This document provides an overview of networking and internetworking concepts. It defines what a network is and some common network protocols like TCP/IP. It discusses how network speed is measured by bit rate and latency. It then covers local area networks, wide area networks, and the internet. The document explains the purpose of networks for file sharing, communication, and remote program execution. It also discusses network messaging and different network service models like the OSI reference model and TCP/IP model. Finally, it provides a simplified example of how the TCP/IP protocol functions to route a packet from a source to destination across multiple routers.
The document provides an overview of computer networking, including definitions of key terms like computer network and network topology. It discusses why networks are needed, how they work, common network models like OSI and TCP/IP. It also covers topics like IP addressing, different network types (LAN, MAN, WAN), common network devices, applications, and security concerns.
The document discusses network topologies and protocols. It covers basic topologies like bus, ring and star and derived topologies like tree and mesh. It then discusses protocols for unicast, multicast and broadcast transmission. Finally, it discusses concepts like packets, frames, bandwidth and different types of networks classified by size and physical medium.
FellowBuddy.com is an innovative platform that brings students together to share notes, exam papers, study guides, project reports and presentation for upcoming exams.
We connect Students who have an understanding of course material with Students who need help.
Benefits:-
# Students can catch up on notes they missed because of an absence.
# Underachievers can find peer developed notes that break down lecture and study material in a way that they can understand
# Students can earn better grades, save time and study effectively
Our Vision & Mission – Simplifying Students Life
Our Belief – “The great breakthrough in your life comes when you realize it, that you can learn anything you need to learn; to accomplish any goal that you have set for yourself. This means there are no limits on what you can be, have or do.”
Like Us - https://www.facebook.com/FellowBuddycom
This document provides an introduction to networking concepts and layered models. It begins with an overview of the Internet as a network of networks connecting billions of devices. Protocols are defined as sets of rules governing format and sequencing of messages between network entities. The network edge includes hosts, access networks using various physical media, and the network core uses packet switching across interconnected routers. Factors that impact performance such as packet loss, delay, and throughput are introduced. Network security concerns like malware, denial of service attacks, packet interception, and spoofing are covered at a high level. Finally, the document introduces the concept of organizing networks into layered models or architectures to provide structure in discussing their complex components and services.
The document discusses key concepts of networking including the three basic elements required: network hardware, software, and protocols. It describes common network types like LAN, WAN, and MAN and compares peer-to-peer and server-based networks. The OSI reference model and TCP/IP model are explained along with common network devices, cabling, and IP addressing schemes.
The document summarizes key concepts in internetworking including protocol layering, encapsulation, and different types of network devices like hubs, bridges, and routers. It describes how the Internet Protocol (IP) allows interconnection of different networks by providing a global addressing scheme and best-effort delivery of packets across interconnected networks.
1. The document discusses basic networking concepts including protocols, protocol layers, and network interconnection. It provides details on network addressing, the Domain Name System, and port numbers.
2. Key protocol layers are examined, including the OSI 7-layer model and the TCP/IP 4-layer model. The roles and functions of each layer are defined.
3. Types of networks like WANs, LANs, Ethernet, Token Ring, and FDDI are introduced along with examples of interconnection devices like bridges, routers, and gateways.
The document summarizes key concepts in internetworking including protocol layering, encapsulation, and different types of network devices like hubs, bridges, and routers. It describes how the Internet Protocol (IP) allows interconnection of different networks by providing a global addressing scheme and best-effort delivery of packets between hosts.
A computer network connects independent computers that communicate over a shared network medium. The basic components of a network include at least two computers (servers or clients), networking interface cards, a connection medium like cables, and network operating system software. There are different types of networks including LANs, WANs, intranets, and the Internet. The OSI model defines seven layers of network functionality from the physical layer up to the application layer. TCP/IP is an open networking model used on the Internet with layers including physical, internet, and transport layers.
This document contains lecture notes on fundamentals of computer systems from Dr. Atif Shahzad. It covers topics such as logic, Boolean algebra, memory, CPU, registers, fetch-execute cycle, file management, networking, OSI model, LAN, WAN, communication protocols, latency, capacity, broadcast, firewalls, and network speeds. The document provides definitions and explanations of key computer science concepts.
The document provides an overview of the key topics that will be covered in Chapter 1 of the textbook "Computer Networking: A Top Down Approach". It outlines the major sections that will be discussed including what the Internet is, the structure of networks including the network edge, core, and hierarchy. It also summarizes that delay, loss, throughput, protocol layers, security, and history will be covered. The goal is to provide an introduction and "feel" for computer networking concepts and terminology that will be explored in more depth throughout the course.
This document provides an overview of IP networking and TCP/IP basics. It discusses the origins of TCP/IP in the ARPANET project and the distributed network design. It describes the OSI model and compares it to the TCP/IP architecture. It also covers IP addressing and numbering, client-server architecture, IP forwarding, and some common network troubleshooting tools.
ip net basic understanding slide show pptlolo749806
This document provides an overview of IP networking and TCP/IP basics. It discusses the origins of TCP/IP from the ARPANET project in the 1960s and its distributed network design. It also describes the OSI model and how TCP/IP maps to it, with layers for the application, transport, internet, and link levels. Finally, it covers client-server architecture and IP addressing fundamentals like public and private address spaces.
Jaimin chp-1 - introduction - 2011 batchJaimin Jani
The document summarizes the key topics covered in Chapter 1 of the book "Computer Networks, Fourth Edition" by Andrew S. Tanenbaum. It discusses the seven-layer OSI reference model and the five-layer TCP/IP reference model as the two main models for organizing computer network software. It also briefly describes the different layers of each model and compares the OSI and TCP/IP models.
The document provides an overview of computer networks and the Internet from multiple perspectives:
1) It describes the "nuts and bolts" view of the Internet as millions of connected devices communicating over physical links using packet switching and protocols.
2) It outlines a "service view" of the Internet as infrastructure providing services to applications like the web and email.
3) It introduces the concept of network protocols that govern all communication and defines common protocols like TCP and IP.
The document summarizes the history and development of Ethernet and TCP/IP networking protocols. It describes how ARPANET originally used packet switching in the 1960s, the development of TCP and IP in the 1970s, and how Ethernet was implemented as a standard for local area networks. It also provides an overview of how IP, TCP and common applications like HTTP operate and interconnect across network layers.
This document discusses computer networking and the OSI model. It provides an overview of how computers communicate at different layers, from the physical layer up to the application layer. It also discusses protocols like TCP/IP and how they map to the OSI model. The document compares OSI to the TCP/IP protocol suite and provides examples of protocols that operate at each layer.
The document provides information about the CCNA (Cisco Certified Network Associate) certification exam, including its introduction, syllabus, fees, number of questions, passing marks, and exam structure over two exams. It also includes summaries of the OSI reference model and TCP/IP model, which define standards for network communication and how data is packaged and transmitted between devices.
This document provides an overview of networking and internetworking concepts. It defines what a network is and some common network protocols like TCP/IP. It discusses how network speed is measured by bit rate and latency. It then covers local area networks, wide area networks, and the internet. The document explains the purpose of networks for file sharing, communication, and remote program execution. It also discusses network messaging and different network service models like the OSI reference model and TCP/IP model. Finally, it provides a simplified example of how the TCP/IP protocol functions to route a packet from a source to destination across multiple routers.
The document provides an overview of computer networking, including definitions of key terms like computer network and network topology. It discusses why networks are needed, how they work, common network models like OSI and TCP/IP. It also covers topics like IP addressing, different network types (LAN, MAN, WAN), common network devices, applications, and security concerns.
The document discusses network topologies and protocols. It covers basic topologies like bus, ring and star and derived topologies like tree and mesh. It then discusses protocols for unicast, multicast and broadcast transmission. Finally, it discusses concepts like packets, frames, bandwidth and different types of networks classified by size and physical medium.
FellowBuddy.com is an innovative platform that brings students together to share notes, exam papers, study guides, project reports and presentation for upcoming exams.
We connect Students who have an understanding of course material with Students who need help.
Benefits:-
# Students can catch up on notes they missed because of an absence.
# Underachievers can find peer developed notes that break down lecture and study material in a way that they can understand
# Students can earn better grades, save time and study effectively
Our Vision & Mission – Simplifying Students Life
Our Belief – “The great breakthrough in your life comes when you realize it, that you can learn anything you need to learn; to accomplish any goal that you have set for yourself. This means there are no limits on what you can be, have or do.”
Like Us - https://www.facebook.com/FellowBuddycom
This document provides an introduction to networking concepts and layered models. It begins with an overview of the Internet as a network of networks connecting billions of devices. Protocols are defined as sets of rules governing format and sequencing of messages between network entities. The network edge includes hosts, access networks using various physical media, and the network core uses packet switching across interconnected routers. Factors that impact performance such as packet loss, delay, and throughput are introduced. Network security concerns like malware, denial of service attacks, packet interception, and spoofing are covered at a high level. Finally, the document introduces the concept of organizing networks into layered models or architectures to provide structure in discussing their complex components and services.
The document discusses key concepts of networking including the three basic elements required: network hardware, software, and protocols. It describes common network types like LAN, WAN, and MAN and compares peer-to-peer and server-based networks. The OSI reference model and TCP/IP model are explained along with common network devices, cabling, and IP addressing schemes.
Similar to preKnowledge-InternetNetworking.ppt (20)
Discover the benefits of outsourcing SEO to Indiadavidjhones387
"Discover the benefits of outsourcing SEO to India! From cost-effective services and expert professionals to round-the-clock work advantages, learn how your business can achieve digital success with Indian SEO solutions.
Ready to Unlock the Power of Blockchain!Toptal Tech
Imagine a world where data flows freely, yet remains secure. A world where trust is built into the fabric of every transaction. This is the promise of blockchain, a revolutionary technology poised to reshape our digital landscape.
Toptal Tech is at the forefront of this innovation, connecting you with the brightest minds in blockchain development. Together, we can unlock the potential of this transformative technology, building a future of transparency, security, and endless possibilities.
Understanding User Behavior with Google Analytics.pdfSEO Article Boost
Unlocking the full potential of Google Analytics is crucial for understanding and optimizing your website’s performance. This guide dives deep into the essential aspects of Google Analytics, from analyzing traffic sources to understanding user demographics and tracking user engagement.
Traffic Sources Analysis:
Discover where your website traffic originates. By examining the Acquisition section, you can identify whether visitors come from organic search, paid campaigns, direct visits, social media, or referral links. This knowledge helps in refining marketing strategies and optimizing resource allocation.
User Demographics Insights:
Gain a comprehensive view of your audience by exploring demographic data in the Audience section. Understand age, gender, and interests to tailor your marketing strategies effectively. Leverage this information to create personalized content and improve user engagement and conversion rates.
Tracking User Engagement:
Learn how to measure user interaction with your site through key metrics like bounce rate, average session duration, and pages per session. Enhance user experience by analyzing engagement metrics and implementing strategies to keep visitors engaged.
Conversion Rate Optimization:
Understand the importance of conversion rates and how to track them using Google Analytics. Set up Goals, analyze conversion funnels, segment your audience, and employ A/B testing to optimize your website for higher conversions. Utilize ecommerce tracking and multi-channel funnels for a detailed view of your sales performance and marketing channel contributions.
Custom Reports and Dashboards:
Create custom reports and dashboards to visualize and interpret data relevant to your business goals. Use advanced filters, segments, and visualization options to gain deeper insights. Incorporate custom dimensions and metrics for tailored data analysis. Integrate external data sources to enrich your analytics and make well-informed decisions.
This guide is designed to help you harness the power of Google Analytics for making data-driven decisions that enhance website performance and achieve your digital marketing objectives. Whether you are looking to improve SEO, refine your social media strategy, or boost conversion rates, understanding and utilizing Google Analytics is essential for your success.
Meet up Milano 14 _ Axpo Italia_ Migration from Mule3 (On-prem) to.pdfFlorence Consulting
Quattordicesimo Meetup di Milano, tenutosi a Milano il 23 Maggio 2024 dalle ore 17:00 alle ore 18:30 in presenza e da remoto.
Abbiamo parlato di come Axpo Italia S.p.A. ha ridotto il technical debt migrando le proprie APIs da Mule 3.9 a Mule 4.4 passando anche da on-premises a CloudHub 1.0.
Instagram has become one of the most popular social media platforms, allowing people to share photos, videos, and stories with their followers. Sometimes, though, you might want to view someone's story without them knowing.
Gen Z and the marketplaces - let's translate their needsLaura Szabó
The product workshop focused on exploring the requirements of Generation Z in relation to marketplace dynamics. We delved into their specific needs, examined the specifics in their shopping preferences, and analyzed their preferred methods for accessing information and making purchases within a marketplace. Through the study of real-life cases , we tried to gain valuable insights into enhancing the marketplace experience for Generation Z.
The workshop was held on the DMA Conference in Vienna June 2024.
1. CIS 3360: Security in Computing
Pre-Knowledge: Internet and Networking
Cliff Zou
Spring 2012
2. 2
Objectives
Obtain the basic knowledge of computer
networking and the Internet
Concepts of network applications, Internet
Basic knowledge of network protocols: TCP/IP
Reading assignment:
Wikipiedia tutorials:
http://en.wikipedia.org/wiki/Internet
http://en.wikipedia.org/wiki/TCP/IP
Reference book:
Computer Networking: A Top Down Approach
Featuring the Internet, 5th edition. Jim Kurose,
Keith Ross, Addison-Wesley, Pearson
Education, 2010
3. Lecture Materials
Some of these slides are adapted from the
slides copyrighted by
Jim Kurose, Keith Ross
Addison-Wesley, Pearson
Education2010.
Computer Networking: A Top Down
Approach Featuring the Internet, 5th
edition.
3
4. 4
A Little Bit of Internet History
1961: Kleinrock - queueing theory shows effectiveness of packet-
switching
1967: ARPAnet conceived by Advanced Research Projects Agency
1969: First ARPAnet node operational
1972: 15 nodes in ARPAnet; First e-mail program
1973: Metcalfe’s PhD thesis proposes Ethernet
1974: Cerf and Kahn - architecture for interconnecting networks
1983: deployment of TCP/IP
1982: smtp e-mail protocol defined
1983: DNS defined for name-to-IP-address translation
early 1990s: Web
Late 1990’s – 2000’s: instant messaging, P2P file sharing; network
security, est. 50 million host, 100 million+ users, backbone links
running at Gbps
5. 5
Cerf and Kahn’s internetworking principles:
minimalism, autonomy - no internal
changes required to interconnect
networks
best effort service model
stateless routers
decentralized control
define today’s Internet architecture
6. 6
What is the Internet?
Application Application
Network Network
Data Link
Transport Transport
Data Link
Physical
link
Web, Email…
TCP, UDP
IP
Ethernet, cellular
7. Some Internet applications
E-mail
Web
Instant messaging
Remote login
P2P file sharing
Multi-user network
games
Streaming stored video
clips
Internet telephone
Real-time video
conference
Massive parallel
computing
8. 8 8
Internet
Internet: loosely
hierarchical “network of
networks”
Major Components: Hosts,
Routers, Communication links
Protocols: for sending,
receiving of msgs
e.g., TCP, IP, HTTP, FTP, PPP
Internet standards
RFC: Request for comments
IETF: Internet Engineering Task
Force
local ISP
company
network
regional ISP
router workstation
server
mobile
9. 9 9
Internet: Three Components
End systems (hosts):
millions of connected
computing devices
executing network
applications
Routers: forwarding packets
(chunks of data)
Communication links:
Connecting hosts and
routers
fiber, copper, radio, satellite
transmission rate =
bandwidth
local ISP
company
network
regional ISP
router
workstation
server
mobile
10. 10
10
Internet Service
Communication infrastructure enables distributed
applications:
Web, email, games, e-commerce, file sharing
Communication services provided to applications:
Connectionless unreliable
connection-oriented reliable
11. 11
11
Internet structure: network of networks
roughly hierarchical
at center: “tier-1” ISPs (e.g., UUNet, BBN/Genuity, Sprint,
AT&T), national/international coverage
treat each other as equals
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
Tier-1
providers
interconnect
(peer)
privately
NAP
Tier-1 providers
also interconnect
at public network
access points
(NAPs)
12. 12
12
Internet structure: network of networks
“Tier-2” ISPs: smaller (often regional) ISPs
Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
NAP
Tier-2 ISP
Tier-2 ISP
Tier-2 ISP Tier-2 ISP
Tier-2 ISP
Tier-2 ISP pays
tier-1 ISP for
connectivity to
rest of Internet
tier-2 ISP is
customer of
tier-1 provider
Tier-2 ISPs
also peer
privately with
each other,
interconnect
at NAP
13. 13
13
Internet structure: network of networks
“Tier-3” ISPs and local ISPs
last hop (“access”) network (closest to end systems)
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
NAP
Tier-2 ISP
Tier-2 ISP
Tier-2 ISP Tier-2 ISP
Tier-2 ISP
local
ISP
local
ISP
local
ISP
local
ISP
local
ISP Tier 3
ISP
local
ISP
local
ISP
local
ISP
Local and
tier- 3 ISPs
are customers
of
higher tier
ISPs
connecting
them to rest
of Internet
14. 14
14
Internet structure: network of networks
a packet passes through many networks!
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
NAP
Tier-2 ISP
Tier-2 ISP
Tier-2 ISP Tier-2 ISP
Tier-2 ISP
local
ISP
local
ISP
local
ISP
local
ISP
local
ISP Tier 3
ISP
local
ISP
local
ISP
local
ISP
15. “Real” Internet delays and routes
What do “real” Internet delay & loss look like?
Traceroute program: provides delay measurement
from source to router along end-end Internet path
towards destination. For all i:
sends three packets that will reach router i on path towards
destination
router i will return packets to sender
sender times interval between transmission and reply.
3 probes
3 probes
3 probes
16. “Real” Internet delays and routes
1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms
2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms
3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms
4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms
5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms
6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms
7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms
8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms
9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms
10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms
11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms
12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms
13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms
14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms
15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms
16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms
17 * * *
18 * * *
19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms
traceroute: gaia.cs.umass.edu to www.eurecom.fr
Three delay measurements from
gaia.cs.umass.edu to cs-
gw.cs.umass.edu
* means no response (probe lost, router not replying)
trans-oceanic
link
Under Windows is “tracert”
19. Where a Router is Placed?
There are many public websites provide
IP location service
www.geobytes.com/iplocator.htm
http://www.iplocation.net/
Based on traceroute and IP locator, you
can know the complete routing path of a
connection
Major reason why many networks block
traceroute traffic
19
20. Protocol
network protocols:
all communication activity in Internet governed by
protocols
Protocols define format, order of
messages sent and received among network
entities, and actions taken on message
transmission, receipt
21. What’s a protocol?
a human protocol and a computer network protocol:
Hi
Hi
Got the
time?
2:00
TCP connection
request
TCP connection
response
Get http://www.awl.com/kurose-ross
<file>
time
22. 22
22
A closer look at network structure:
network edge:
applications and
hosts
network core:
routers
network of
networks
Connection:
communication
links
23. The network edge:
end systems (hosts):
run application programs
e.g. Web, email
at “edge of network”
client/server model
client host requests, receives
service from always-on server
e.g. Web browser/server; email
client/server
peer-peer model:
minimal (or no) use of
dedicated servers
e.g. Gnutella, KaZaA
24. Network edge: connection-oriented
service
TCP [ Transmission Control Protocol ]
reliable, in-order : byte-stream data transfer
loss: acknowledgements and retransmissions
flow control:
sender won’t overwhelm receiver
congestion control:
senders “slow down sending rate” when network congested
Examples of applications using TCP:
HTTP (Web), FTP (file transfer), SSH
(remote secure login), SMTP (email)
25. Network edge: connectionless service
UDP [User Datagram Protocol]
connectionless
unreliable data transfer
no flow control
no congestion control
Examples of applications using UDP:
streaming media, teleconferencing, DNS, Internet
telephony
26. The Network Core
mesh of interconnected
routers
data transfer methods
through net
circuit switching:
dedicated circuit per
call: telephone net
packet-switching:
data sent through
net in discrete
“chunks”
27. Circuit Switching
End-end resources
reserved for “call”
call setup required
link bandwidth, switch
capacity
dedicated resources: no
sharing
circuit-like (guaranteed)
performance
28. Packet-switched networks
Move packets through routers from source to
destination
datagram network:
destination address in packet determines next hop
routes may change during session
virtual circuit network:
each packet carries tag (virtual circuit ID), tag determines next
hop
fixed path determined at call setup time, remains fixed thru call
routers maintain per-call state
29. Internet protocol stack
application: supporting network
applications
FTP, SMTP, HTTP
transport: host-host data transfer
TCP, UDP
network: routing of datagrams from
source to destination
IP, routing protocols
link: data transfer between neighboring
network elements
PPP, Ethernet
physical: bits “on the wire or wireless”
application
transport
network
link
physical
31. Message Flow
transport segment from
sending to receiving host
on sending side
encapsulates segments
into datagrams
on receiving side, delivers
segments to transport
layer
network layer protocols in
every host, router
router examines header
fields in all IP datagrams
passing through it
application
transport
network
data link
physical
application
transport
network
data link
physical
network
data link
physical network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
31
33. TCP Transport Layer
IP Network Layer
Networking security mainly deals
with these two services/protocols
33
34. Transport Layer
TCP - connection-oriented service
Provide reliable data transmission
Used by most data-based, not time-sensitive
network applications
Email, Web, file transfer….
Require to set up TCP connection channel first
UDP – connectionless service
Unreliable data transmission
Error packets will be discarded without
retransmission
No additional delay for future incoming packets
Used for time-sensitive, error-tolerant applications
VOIP, video streaming, DNS….
34
35. Transport vs. network layer
network layer: logical communication between hosts
transport layer: logical communication between
processes
relies on, enhances, network layer services
A
B
C
D
Sport:4625
Dport: 80
Sport:8050
Dport: 25
36. Addressing processes
to receive messages, process must have identifier
identifier includes both IP address and port numbers
associated with process on host.
host device has unique 32-bit IP address
IP address is for addressing a host/computer
Example port numbers:
HTTP server: 80
Mail server: 25
to send HTTP message to gaia.cs.umass.edu web
server:
IP address: 128.119.245.12
Port number: 80
37. TCP and UDP Port Numbers
16 bits (0 – 65535)
Internet Assigned Numbers Authority
(IANA) www.iana.org
Well known ports (0 -1023)
Example: HTTP – 80, SMTP – 25
Registered ports (1024 – 49151)
Example: HTTP alternate 8080 used for web
proxy and caching server
Dynamic and/or private ports: (49152–
65535)
38. Each TCP connection is identified by
4-tuple:
source IP address
source port number
dest IP address
dest port number
These four values are widely used in
network filtering and intrusion
detection
38
39. UDP Packet Header
UDP packet
header is 8
bytes long
Port number is
16 bits long
Checksum for
verifying packet
error
39
source port # dest port #
32 bits
Application
data
(message)
UDP segment format
length checksum
Length, in
bytes of UDP
segment,
including
header
40. UDP Transmission Process
40
Host A
time
Host B
X
No acknowledgement
from recipient
Sending rate is
controlled by sender
(bounded by sender’s
bandwidth)
41. TCP Transmission Process (simplified
without considering piplining)
41
Need sequence # and acknowledge # to
distinguish each packet
42. TCP segment structure
(Header is 20 bytes normally)
source port # dest port #
32 bits
application
data
(variable length)
sequence number
acknowledgement number
Receive window
Urg data pnter
checksum
F
S
R
P
A
U
head
len
not
used
Options (variable length)
URG: urgent data
(generally not used)
ACK: ACK #
valid
PSH: push data now
RST, SYN, FIN:
connection estab
(setup, teardown
commands)
# bytes
rcvr willing
to accept
counting
by bytes
of data
(not segments!)
Internet
checksum
(as in UDP)
43. TCP seq. #’s and ACKs
Seq. #’s:
byte stream “number” of first byte in segment’s data
ACKs:
seq # of next byte expected from other side
Cumulative ack ack to receive all bytes until the
specified #
Q: how receiver handles out-of-order segments?
TCP spec doesn’t say
Practical approach: save in buffer
Q: How TCP implement duplex communication?
Seq. # for sending data, Ack# for receiving data
44. An example of TCP Duplex Communication
Host A Host B
User
host ACKs
receipt, send
back use
password
host ACKs
receipt, echoes
back ‘pass’
time
simple telnet scenario
42
79
Sequence number is
based on bytes, not packets!
45. ACK Only in Duplex Communication ?
45
host ACKs
receipt, send
back use
password
time
ACK only packet, seq# is the first byte
to be transmitted in the future
(the packet has no data section)
46. TCP: retransmission scenarios
Host A
time
premature timeout
Host B
Seq=92
timeout
Host A
loss
timeout
lost ACK scenario
Host B
X
time
Seq=92
timeout
SendBase
= 100
SendBase
= 120
SendBase
= 120
Sendbase
= 100
47. TCP retransmission scenarios
(more)
Host A
loss
timeout
Cumulative ACK scenario
Host B
X
time
SendBase
= 120
Host A
time
premature timeout
Host B
Seq=92
timeout
Seq=92
timeout
SendBase
= 120
SendBase
= 120
Sendbase
= 100
48. TCP Connection Setup ---
Three-Way Handshaking
Step 1: client host sends TCP SYN
segment to server
specifies initial seq #
no data
Step 2: server host receives SYN,
replies with SYN/ACK segment
server allocates buffers
specifies server initial seq. #
Step 3: client receives SYN/ACK,
replies with ACK segment, which
may contain data
client server
49. TCP Connection Setup
Most firewalls, packet capturing software,
and intrusion detection software use TCP
connection setup packets to determine
how to deal with the new connection
Very important to understand the three-way
handshake
49
50. TCP Connection Management (cont.)
Closing a connection:
close();
Step 1: client end system
sends TCP/FIN control
segment to server
Step 2: server receives FIN,
replies with ACK. Closes
connection, sends FIN.
client server
close
close
closed
timed
wait
51. TCP Connection Management (cont.)
Step 3: client receives FIN,
replies with ACK.
Enters “timed wait” - will
respond with ACK to
received FINs
Step 4: server, receives ACK.
Connection closed.
client server
closing
closing
closed
timed
wait closed
Some applications simply
send RST to terminate TCP
connections immediately