Networks, Security, and Privacy 158.235
Dr Hooman Alavizadeh Massey University
(Today covers chapter 1 in the textbook)
1-1
Housekeeping
• Textbooks
– J. FitzGerald and A. Dennis, “Business Data Communications &
Networking”, 12th edition. Wiley, 2012. Networking part (Weeks 1-6)
– W. Stallings and L. Brown, “Computer Security: Principles and Practice”, Global Edition eBook (4e), Pearson, 2018
Security & Privacy part (Weeks 7-12)
• Delivery
– One Lecture (2-hour) per week, wk1 – wk12 (12 weeks)
– One lab (1-hour) per week, wk2 – 11 (10 weeks)
1-2
Housekeeping
• Assessments (Computer Works) – Internal Assessments (80%)
• 2 assignments throughout the semester (40% each) – Lab Reports (20%)
• 10 lab reports to be submitted after each lab session (2% each)
• Software
– Wireshark (www.wireshark.org) :
• network traffic capture & analysis
– Packet tracer (https://www.netacad.com/about-networking-
academy/packet-tracer/) • Network simulation
1-3
Our goal:
❖ get “feel” and terminology
❖ more depth, detail later in course
❖ approach:
▪ use Internet as example
overview:
❖ Network components ❖ types of network
❖ protocol layers ▪ ISO 7 layer
▪ Internet 5 layer
❖ what’s a protocol? ❖ network standards
Introduction
1-4
Components of a Network
1-5
Components of a Network
network devices
Circuit (pathway) Network Media
1-6
Network Types (based on Scale)
mobile network
global ISP
regional ISP
home network
institutional network
1-7
Network Types (based on Scale)
• Local Area Networks (LAN) – room, building
– a group of PCs that share a circuit • Backbone Networks (BN) – less
than few kms
– a high speed backbone linking together organizational LANs at various locations.
• Metropolitan Area Networks (MAN) – (more than a few kms)
– connects LANs and BNs across different locations
– Often uses leased lines or other services (expensive, high transfer rate; ISP alternative)
• Wide Area Networks (WANs) – (far greater than 10 kms)
– Same as MAN except wider scale
1-8
Network: nuts and bolts
• millions of connected computing devices:
PC server
wireless laptop
smartphone
– hosts = end systems – runningnetworkapps
mobile network
global ISP
home
network
regional ISP
institutional network
router
wireless links
wired links
❖ Network devices: forward packets (chunks of data)
▪ routers and switches ❖ communication links
▪ fiber, copper, radio, satellite
▪ transmission rate: bandwidth
1-9
Network: nuts and bolts
• protocols control sending, receiving of msgs
– e.g., TCP, IP, HTTP, Skype, 802.11
• Internet standards
– RFC: Request for comments
– IETF: Internet Engineering Task Force
• Internet: “network of networks”
– InterconnectedISPs
mobile network
global ISP
home
network
regional ISP
institutional network
1 – 10
What is a protocol?
human protocols (rules):
• “what’s the time?”
• “I have a question” • introductions
… specific msgs sent
… specific actions taken when msgs received, or other events
network protocols:
• machines rather than humans
• all communication activity in Internet governed by protocols
protocols define format, order of msgs sent and received
among network entities, and actions taken on msg
transmission, receipt
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What is a protocol?
a human protocol and a computer network protocol:
Hi Hi
TCP connection request
TCP connection response
Get http://www.awl.com/kurose-ross
Got the time?
2:00
time
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Network Protocols
• Used by network model layers
• Sets of standardized rules to define how to communicate at each layer and how to interface with adjacent layers
Layer N+1
Layer N Layer N-1
Layer N+1 Layer N
Layer N-1
sender
receiver
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Networks are complex, with many “pieces”:
– hosts
– Routers/switches
– links of various media
– protocols
– applications
– hardware,software
Question:
is there any hope of organizing structure
of network?
Protocol “layers”
1 – 14
Layered Implementation
Single layer
implementation
-Networking with large components is complex to understand and implement
Multi layer
implementation -Breaking down into smaller components -Easier to implement
Applications OS
Applications OS
Applications OS
Applications OS
1 – 15
Multi-layer Network Models
• The two most important such network models: OSI and Internet
• Open Systems Interconnection Model (OSI)
– Created by International Standards Organization (ISO)
as a framework for computer network standards in 1984
– Based on 7 layers
• Internet Model (also called TCP/IP model)
– Created by DARPA originally in early 1970’s
– Developed to solve the problem of internetworking
– Based on 5 layers
– Based on Transmission Control Protocol/ Internet Protocol (TCP/IP) suite
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7-Layer Model of OSI
“Please Do Not Touch Steve’s Pet Alligators”
• Application Layer
– set of utilities used by application programs
• Presentation Layer
– formats data for presentation to the user
– provides data interfaces, data compression and translation between different data formats
• Session Layer
– initiates, maintains and terminates each logical session between sender and receiver
Physical
DataLink
Network
Transport
Session
Presentation Application
1 – 17
7-Layer Model of OSI
• Transport Layer
– deals with end-to-end issues such as segmenting the message for network transport, and maintaining the logical connections between sender and receiver
• Network Layer
– responsible for making routing decisions from source to
destination
• Data Link Layer
– Responsible for moving messages from one device to another reliably
• Physical Layer
– defines how individual bits are formatted to be transmitted through the network
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Internet’s 5-Layer Model
“Please Do Not Touch Alligators”
• Application Layer –
– Combines Application, Presentation, session layer of OSI model
• Transport Layer – Same as transport layer of OSI model
• Network Layer – Same as OSI model
• Data Link Layer – Same as OSI model
• Physical Layer – Same as OSI model
Physical
DataLink
Network
Transport Application
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Comparison of Network Models
1 – 20
Network models
• Protocol defines the language of transmission – It specifies the rules, functionality, and
messages for communication at the layer
• Protocol Data Unit (PDU) contains layer-specific information necessary for a message to be transmitted through a network
– Each layer adds a PDU
– PDUs act like nested envelopes
– Encapsulation occurs when a higher level PDU is placed inside of a lower level PDU
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Network Models
Layer
Purpose
Example Protocols / Standards
PDU
5. Application
User’s access to network, software to perform work
HTTP, SMTP, DNS, FTP, DHCP, IMAP, POP, SSL
Packet (or Data)
4. Transport
End-to-End Management
1.Link application layer to network 2.Segmenting and tracking 3.Flow control
TCP, UDP
Segment
3. Network
Deciding where the message goes 1.Addressing
2.Routing
IP, ICMP
Packet
2. Data Link
Move a message from one device to the next 1.Controls hardware
2.Formats the message
3.Error checking
Ethernet
Frame
1. Physical
Transmits the message
100BASE-T, 802.11n
1 – 22
Sender PDU Receiver
Application
HTTP Request
Message
HTTP Request
Transport
TCPP HTTP Request
Segment
TCP
HTTP Request
Network
IP
TCP
HTTP Request
Packet/ Datagram
IP
TCP
HTTP Request
Data Link
Ethernet
IP
TCP
HTTP Request
Frame
Ethernet
IP
TCP
HTTP Request
Physical
23
Points about Network Layer View
• Layers allow simplicity of networking in some ways
– Easy to develop new software that fits each layer
– Relatively simple to change the software at any level
• Matching layers communicate between different computers and computer platforms
– Accomplished by standards that we all agree on
– e.g., Physical layer at the sending computer must
match up with the same layer in the receiving computer
• Somewhat inefficient
– Involves many software packages and packets
– Packet overhead (slower transmission, processing time)
– Interoperability achieved at the expense of perfectly streamlined communication
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Network Standards
• Why?
– Provide a “fixed” way for hardware and/or software
systems (different companies) to communicate
– Help promote competition and decrease the price
• Types of Standards – Formal standards
• Developed by an industry or government standards- making body
– De-factostandards
• Emerge in the marketplace and widely used
• Lack official backing by a standards-making body
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Major Standards Bodies
• ISO (International Organization for Standardization)
– One of the most important standard making bodies
– Makes technical recommendations about data
communication interfaces
• ANSI (American National Standards Institute) – Coordinating organization for the US national system of
standards for both technology and nontechnology
• IEEE (Institute of Electrical and Electronic Engineers)
– Makes standards for LANs
• IETF (Internet Engineering Task Force) – Makes standards for Internet
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