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ISA 3200 NETWORK SECURITY Chapter 2: An Introduction to Networking

Dec 25, 2015

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  • Slide 1
  • ISA 3200 NETWORK SECURITY Chapter 2: An Introduction to Networking
  • Slide 2
  • Learning Objectives Upon completion of this chapter, you should be able to: Describe the basic elements of computer-based data communication Know the key entities and organizations behind current networking standards, as well as the purpose of and intent behind the more widely used standards Explain the nature and intent of the OSI reference model and list and describe each of the models seven layers Describe the nature of the Internet and the relationship between the TCP/IP protocol and the Internet 2 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 3
  • Networking Fundamentals Fundamental exchange of information: sender communicates message to receiver over some medium Communication only occurs when recipient is able to receive, process, and comprehend message One-way flow of information is called a channel When recipient becomes a sender, for example by responding to original senders message, this two-way flow is called a circuit 3 5/31 and 6/2 ISA 3200---Summer 2010
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  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 4 Networking Fundamentals (continued) 4 Any medium may be subject to interference, called noise, which occurs in variety of forms Attenuation: loss of signal strength as signal moves across media Crosstalk: occurs when one transmission bleeds over to another Distortion: unintentional variation of communication over media 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 5
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 5 Networking Fundamentals (continued) 5 Any medium may be subject to interference, called noise, which occurs in variety of forms (continued) Echo: reflection of a signal due to equipment malfunction or poor design Impulse: sudden, short-lived increase in signal frequency or amplitude, also known as a spike Jitter: signal modification caused by malfunctioning equipment White noise: unwanted noise due to signal coming across medium at multiple frequencies 5/31 and 6/2 ISA 3200---Summer 2010
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  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 6 Reasons to Network 6 Data communications: exchange of messages across a medium Networking: interconnection of groups or systems with purpose of exchanging information Some reasons to build a network: To exchange information To share scarce or expensive resources To allow distributed organizations to act as if centrally located 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 7
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 7 Types of Networks 7 Networks can be categorized by: Components: peer-to-peer (P2P), server- based, distributed multi-server Size: local area network (LAN), metropolitan area network (MAN), wide area network (WAN) Layout or topology: physical (ring, bus, star, hierarchy, mesh, hybrid), logical (bus, star) Media: guided (wired), unguided (wireless) 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 8
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 8 Network Standards 8 Among the agencies that work on data communications standards are: Internet Society (ISOC) Internet Assigned Numbers Authority (IANA) American National Standards Institute (ANSI) International Telecommunication Union (ITU) Institute of Electrical and Electronics Engineers (IEEE) Telecommunications Industry Association (TIA) International Organization for Standardization (ISO) 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 9
  • Layered Schemes 5/31 and 6/2 ISA 3200---Summer 2010 9 Communication is so complex that it is very helpful to modularize the systems involved The scheme generally used is a layered scheme Each layer in a communication stack handles one aspect of communication over a network
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  • Logical vs. Actual 5/31 and 6/2 ISA 3200---Summer 2010 10 A layer operates by Receiving data from a higher layer Sending data to a lower layer Logically, a layer acts as if it is communicating with the associated layer on a different system
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  • 5/31 and 6/2 ISA 3200---Summer 2010 11 Layer 1 Layer 2 Layer 3 Host A Layer 1 Layer 2 Layer 3 Host B Logical Channels
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  • Hops 5/31 and 6/2 ISA 3200---Summer 2010 12 Connecting one network to another Some hosts belong to two or more networks Communication can move from physical network to physical network
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  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 13 OSI Reference Model and Security 13 OSI reference model allocates functions of network communications into seven distinct layers, each with its own functions and protocols Premise of model is information sent from one host is translated and encoded through various layers, from Application layer to Physical layer Physical layer initiates transmission to receiver Receiver translates and decodes message by processing information through each layer in reverse order 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 14
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 14 The Physical Layer 14 The primary function of the Physical layer is to place the transmission signal carrying the message onto the communications media that is, to put bits on a wire The functions of the Physical layer are: Establish and terminate the physical and logical connection to the media Manage the flow and communication on the media Embed the message onto the signal carried across the physical media 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 15
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 15 Network Media 15 Dominant media types and standards include: Coaxial cable Fiber-Optic cable Twisted-pair wire Wireless LAN Bluetooth Infrared 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 16
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 16 Embedding the Message 16 Method used to embed message on signal depends on type of message and type of signal Two types of message (or information): Analog information: continuously varying source (such as voice communications) Digital information: discrete, between a few values (such as computer communications) 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 17
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 17 Embedding the Message (continued) 17 Multiplexing combines several circuits to create high-bandwidth stream to carry multiple signals long distances Three dominant multiplexing methods are: Frequency division multiplexing (FDM): combines voice channels Time division multiplexing (TDM): assigns a time block to each client Wave division multiplexing (WDM): uses different frequencies of light so multiple signals can travel on same fiber-optic cable 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 18
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 18 Managing Communication 18 Bit (or signal) flow conducted in several ways: Simplex transmissions: flow one way through a medium Half-duplex transmissions: flow either way, but in only one direction at a time Full-duplex transmissions: can flow both ways at the same time Serial transmissions: flow one bit at a time down a single communications channel Parallel transmissions: flow multiple bits at a time down multiple channels 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 19
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 19 Managing Communication (continued) 19 Asynchronous (or timing-independent) Formulate data flow so each byte or character has its own start and stop bit Used in older modem-based data transfers to send individual characters between systems Synchronous (or timing-dependent) Use computer clocking to transmit data in continuous stream between two systems Clock synchronization makes it possible for end nodes to identify start and end of data flow This protocol is much more efficient 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 20
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 20 Data Link Layer 20 Primary networking support layer Referred to as first subnet layer because it provides addressing, packetizing, media access control, error control, and some flow control for local network In LANs, it handles client-to-client and client-to-server communications 5/31 and 6/2 ISA 3200---Summer 2010
  • Slide 21
  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 21 Data Link Layer (continued) 21 DLL is further divided into two sublayers: Logical Link Control (LLC) sublayer Primarily designed to support multiplexing and demultiplexing protocols transmitted over MAC layer Also provides flow control and error detection and retransmission Media Access Control (MAC) sublayer Designed to manage access to communications mediain other words, to regulate which clients are allowed to transmit and when 5/31 and 6/2 ISA 3200---Summer 2010
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  • Firewalls & Network Security, 2nd ed. - Chapter 2 Slide 22 DLL Protocols 22 Dominant protocol for local area networking is Ethernet for wired networks and Wi-Fi for wireless networks Other DLL LAN protocols include: Token ring Fiber Distributed Data Interface (FDDI) Point-to-Point Protocol (PPP) Point-to-Point Tunneling Protocol (PPTP) Layer Two Tunneling Protocol (L2TP) WANs typically use ATM and frame relay 5/31 and 6/2 ISA 3200---Summe
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