MeyersCompTIANet+Gde6eChap001PPT-edit

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Jan 12, 2025

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M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Objectives•Describe how models such as the OSI seven-layer model and the TCP/IP model help technicians understand and troubleshoot networks•Explain the major functions of network hardware with the OSI seven-layer model•Describe the major functions of networks with the TCP/IP model

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Two Network Models•The OSI seven-layer and TCP/IP models provide:–A powerful tool for diagnosing problems–A common language to describe networks

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Models•What does “model” mean to you?•All models are a simplified representation of the real thing

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.ModelsFigure 1.2 Types of modelsComputer models that predict weather, plastic model airplane, fashion model

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.A Model: An Example•A model has all the major functions of the real itemFigure 1.3 Simple model airplane

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Network Models: Overview•What functions define all networks?•What details can be omitted?•ISO (International Organization for Standardization) proposed the OSI seven-layer model

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Layer 7 - ApplicationLayer 6 - PresentationLayer 5 - SessionLayer 4 - TransportLayer 3 - NetworkLayer 2 - Data LinkLayer 1 - PhysicalThe OSI Model

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•One of the workers has just completed a new employee handbook–She needs to transfer the Word document to the other worker for review•She Could:–Copy the file to a flash drive and walk it over to the other person (Sneakernet)–Transfer the file using the networkOSI Model in Action (an example)

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Let’s Get Physical—Network Hardware and Layers 1–2

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•Most networks use unshielded twisted pair (UTP) cable as a physical channel to move the bits of data between systemsCablingFigure 1.5 UTP cabling

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Central Box•Each computer system has a cable leading to a central box–The central box sends the data received from one system to all the other systems attached to itFigure 1.6 Typical central box

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.NIC to Central Box Connections•Cables run from the NIC to a jack on the wall–Inside the wall another cable runs all the way back to the central boxFigure 1.9 Dongle NIC with cable connecting the laptop to the wall jack

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•Each system must have a unique identifier•Media access control address or MAC address–A unique address burned into a ROM chip on the NIC–Each MAC address is 12 hex characters or 48 bits in lengthThe NIC

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•MAC addresses are 48 bits long–Usually represented using hexadecimal characters (12 hex digits = 48 bits)•A typical MAC address: 00-40-05-60-7D-49–No two MAC addresses are ever the same!MAC AddressesOrganizationally Unique Identifier (OUI)Device ID

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Frames•A frame is basically a container for a chunk of data moving across a network–Contains the recipient’s MAC address, the sender’s MAC address, the Type field, the data itself, and a frame check sequence (FCS)Figure 1.18 Generic frame

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Frames•Frame Sequence Checking (FCS) uses binary math called cyclic redundancy check (CRC) for error checking•Frame can be thought of as having three sections–Header (MAC addresses and Type), payload and trailer•NIC does not care what is inside the data part of the frame

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Frame Size•Different types of networks use different sizes of frames•Many frames hold at most 1500 bytes of data•The sending software breaks up large amounts of data into smaller chunks•The receiving system’s software must recombine the data chunks

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Into the Central Box•When a system sends a frame out on the network, the frame goes into the central box•The technology of the central box determines the next steps for the frame

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•In the early days, the central box was called a hub–The hub made copies of a frame and sent a copy to every other system on the network–Every frame sent on a network was received by every NIC–Only the NIC with the matching MAC address would process that particular frameThe Central Box: Hubs

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•Switches replaced hubs–A frame is sent only to the correct recipient MAC address•Switches maintain a table that maps MAC addresses to switch portsThe Central Box: Switches

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Getting the Data on the Line•Since the cable is shared, only one system may speak at a time•Networks use frames to restrict the amount of data a NIC can send at once•NICs handle these and other issues on their own without our help

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Getting to Know You•Usually two devices have talked before, so the destination MAC address is already known•If the MAC address is not known, a broadcast message is sent over the network–The destination device will respond by sending its MAC address–The MAC broadcast address is FF-FF-FF-FF-FF-FF

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•The receiving NIC uses the FCS to verify that the data is valid•If the data is valid, the receiving NIC strips off all the framing information and sends the data to the software—the operating system—for processing After the Frame is Received

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.The Two Aspects of NICs•Logical Link Control (LLC): the aspect of the NIC that talks to the system’s operating system (usually via device drivers)–Handles multiple network protocols and provides flow control•Media Access Control (MAC): the role in which frames are created and addressed

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Beyond the Single Wire— Network Softwareand Layers 3–7

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•A logical addressing method:–Ignores the hardware–Enables breaking a large network into subnets •A network protocol creates:–Unique identifiers for each system–A set of communication rules for issues, e.g. how to get packets from one subnet to anotherHow Does Data Get from One System to Another in Large Networks?

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•Packets are created and addressed•The Internet Protocol is the primary logical addressing protocol for TCP/IP•A router connects each of the subnets–The IP address is used to forward dataIP—Playing on Layer 3, the Network Layer

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Packets Within Frames•To send data successfully in a TCP/IP network–Data is wrapped up in two distinct containers–Inner container is called a packetFigure 1.30 IP packet

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Packets Within Frames•IP packet is handed to the NIC–NIC encloses the IP packet in a regular frameFigure 1.31 IP packet in a frame (as a canister)

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Packets Within Frames•Packet is enclosed within a frame–Contains sending and receiving MAC addressesFigure 1.32 IP packet in a frame

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.The Process of Sending Data•Data sent from one computer to another on a TCP/IP network can go through many routers•Each router strips off the incoming frame–Examines the IP address in the packet to determine where to send the data–Creates a new frame needed for the connection (e.g., cable or DSL network)–Sends the packet within the new frame to next router

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•Once the packet reaches the destination subnet’s router, that router:–Strips off the incoming frame–Looks at the destination address–Adds a frame with the appropriate MAC address•Receiving NIC strips away the Ethernet frame–Passes the remaining packet off to the software–The networking software built into the operating system handles the rest of the workThe Process of Sending Data (cont’d.)

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•Most data is much larger than a single frame•The transport protocol –Breaks up the data into chunks called segments or datagrams (depending on the specific transport protocol used) –Gives each segment some type of sequence number Assembly and Disassembly—Layer 4, the Transport Layer

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•The transport protocol breaks data into segments and gives each segment a sequence number•The sequence numbers notify the receiving system of the total number of segments and how to put them together–Similar to the numbering of boxes by UPSAssembly and Disassembly—Layer 4, the Transport Layer (cont’d.)

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•It is the assembler/disassembler software•Also initializes requests for packets that were not received in good orderThe Functions of the Transport Layer

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Segmentation and Reassembly—Layer 4, the Transport Layer•Connection-oriented vs. connectionless communication–Connection-oriented protocols require a connection between client and server before communication can start•Transmission Control Protocol (TCP)–Connectionless protocols start communicating without first verifying a connection exists•User Data Protocol (UDP)

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Segmentation and Reassembly—Layer 4, the Transport Layer•Segments within packets–TCP segment•Remains after stripping away IP addresses from an IP packet and contains many fields–TCP segment port•A number between 1 and 65,536—a logical value assigned to specific applications or services•Example: Web server “listens” or looks for TCP segments with the destination port numbers 80 or 443

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Segmentation and Reassembly—Layer 4, the Transport Layer•Transport layer receives application layer data –Breaks the application data into chunks–Adds port numbers and sequence numbers–Creates the TCP segment–Hands the TCP segment to the Network layer, which creates the IP packet•TCP/IP network uses TCP at the Transport layer

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Segmentation and Reassembly—Layer 4, the Transport Layer•UDP datagram created in the Transport layer–Includes port and length numbers plus a checksum as a header–Combines that header with data•UDP datagram lacks most of the extra fields found in TCP segments–Does not care if receiving computer gets its data

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•One system may be talking to many other systems simultaneously•Session software connects applications to applications•Session layer handles all the sessions–Initiates sessions, accepts incoming sessions, and opens and closes existing sessions•IP address and port number used for a sessionTalking on a Network—Layer 5,the Session Layer

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.•The Presentation layer translates data from lower layers into a format usable by the Application layer, and vice versa–TCP/IP networks do not necessarily map directly to the OSI model •Many protocols function on more than one OSI layer and can include Layer 6, Presentation–e.g. Transport Layer Security (TLS) protocolTranslation—Layer 6, the Presentation Layer

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Network Applications—Layer 7, the Application Layer•People use software applications to exchange data on a network–Network applet in Windows 10, Web browsers, and e-mail applications•Applications may include additional functions–Examples: encryption, user authentication, and tools to control the look of data

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.Network Applications—Layer 7, the Application Layer (cont’d)•Application layer (Layer 7) of the OSI model–Refers to code built into all operating systems that enables network-aware applications•Application Programming Interfaces (APIs)–Included in all operating systems–Used to make programs network-aware–Provide a standard way for programmers to enhance or extend an application’s capabilities

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.The OSI Seven-Layer Model and Remote Work (1 of 7)•A day in the life of a remote data analyst–Analyst connects to Internet wirelessly with a laptop–Accesses online services through a browser•Note that the OSI layers apply in a wireless network

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.The OSI Seven-Layer Model and Remote Work (3 of 7)•Layer 1 examples–Wireless radio waves connecting the laptop to a wireless access point (WAP)–Physical wires connecting the WAP to the router, Internet service provider (ISP), and all the routers in between there and a corporate network and other Internet-based services

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.The OSI Seven-Layer Model and Remote Work (6 of 7)•Layer 2 examples–Wireless NIC in the laptop has a MAC address and connects to the WAP with frames–The WAP uses MAC addresses to connect to the local switch•Layer 3 examples–TCP/IP is used for connections and interactions–By definition, the laptop must have a valid IP address or two

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Sixth Edition (Exam N10-008)Copyright © 2022 by McGraw-Hill Education. All rights reserved.The OSI Seven-Layer Model and Remote Work (7 of 7)•Layer 4 examples–TCP/IP is used for connections and interactions–The laptop must encapsulate/decapsulate segments and datagrams at the Transport layer•Layer 7 examples–Web-based tools today rely on HTTP and TLS (HTTPS)

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Fifth Edition (Exam N10-007)Copyright © 2018 by McGraw-Hill Education. All rights reserved.•Encapsulation: the entire process of preparing data to go onto a network–All the steps from the application to the Application, Presentation, Session, Transport, Network, and Data Link layers•De-encapsulation: the reverse process of encapsulation–Stripping all the extra header information out as the data goes up the stackEncapsulation and De-Encapsulation

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Fifth Edition (Exam N10-007)Copyright © 2018 by McGraw-Hill Education. All rights reserved.•TCP/IP does not have a standards body –Results in a number of variations on the TCP/IP model•Version 1 (four layers) is used by Cisco, Microsoft, and other major companiesThe TCP/IP Model (cont’d.)

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Fifth Edition (Exam N10-007)Copyright © 2018 by McGraw-Hill Education. All rights reserved.•Corresponds to OSI model Layers 1 and 2 •Handles “physical” elements (cabling, hubs, physical addresses, and NICs)•Any part of the network that deals with complete frames is in the Link layer–Once the frame information is stripped away from an IP packet, we move into the Internet layerThe Link (Network Interface) Layer

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Fifth Edition (Exam N10-007)Copyright © 2018 by McGraw-Hill Education. All rights reserved.Figure 2.43 TCP/IP Link layer compared to OSI Layers 1 and 2

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Fifth Edition (Exam N10-007)Copyright © 2018 by McGraw-Hill Education. All rights reserved.•The “IP packet” layer•Deals with any device or application that uses IP protocols and IP addressing and routing•Routers function at this layer•Maps to the Network layer (Layer 3) of the OSI model•IP packets are created in this layerThe Internet Layer

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Fifth Edition (Exam N10-007)Copyright © 2018 by McGraw-Hill Education. All rights reserved.•Maps to OSI Transport layer, Session layer, and some of the Application layer•Involved with assembly and disassembly of data•Provides both connection-oriented and connectionless communicationsThe Transport Layer

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Fifth Edition (Exam N10-007)Copyright © 2018 by McGraw-Hill Education. All rights reserved.•The TCP/IP Application layer maps to the top three layers of the OSI model–Uses a unique port numbering system that gives each application a unique number between 1 and 65,535–Allows Presentation layer formats, such as MIME•Every TCP/IP application must be a part of a network to functionThe Application Layer

M ike M eyers’ CompTIA Network+®Guide to M anaging and Troubleshooting Networks, Fifth Edition (Exam N10-007)Copyright © 2018 by McGraw-Hill Education. All rights reserved.•Application layer: create the data•Transport layer: breaks the data into chunks, i.e., into TCP/UDP segments•Internet layer: adds the IP addressing and creates the IP packets•Link layer: wraps the IP packet into a frame, with the MAC address information and a frame check sequence (FCS)Frames, Packets, and Segments/Datagrams, Oh My!