IT 271 Computer Networks Fundamentals PDF

IT 271 Computer Networks Fundamentals 1 Module 1 Explaining Network Topologies 2 Learning Objectives Explain network types and characteristics. Compare and contrast OSI model layers. Configure SOHO networks. Explain CompTIA...

IT 271 Computer Networks Fundamentals 1 Module 1 Explaining Network Topologies 2 Learning Objectives Explain network types and characteristics. Compare and contrast OSI model layers. Configure SOHO networks. Explain CompTIA’s troubleshooting methodology. 3 Lesson 1.1 Networking Overview 4 Think About It How would you define your social network? 5 How are Personal and IT Networks Similar? Social Network IT Network A collection of computers and A collection of friends, family, other devices connected by coworkers, and acquaintances transmission medium Provides emotional support, Provides an opportunity for advice, and opportunities in shared resources personal matters Helps in communication, Helps with communication information sharing, and and information sharing in a social connections digital environment 6 What’s A computer Network ? "A computer network is a system of interconnected devices that communicate using standard protocols to share resources, exchange data, and provide services, using wired or wireless connection." 7 Networks working architecture Peer-to-Peer Client-Server 8 Networks working architecture (Cont’d) 1. Peer-to-Peer (P2P) Network In a P2P network, each device (called a peer) is both a client and a server. All devices in the network have equal responsibilities and can directly communicate with each other, sharing resources without a central authority. It is typically used in smaller networks or for specific applications like file sharing. Advantages: Simple to set up. No need for a central server. Each device can act as a server Disadvantages: Not as scalable for large networks. Limited security and management features. 9 Networks working architecture (Cont’d) 2. Client-Server Network In a Client-Server network, there is a clear distinction between the client and the server. The server is a central system that manages resources, and clients are devices (e.g., computers, smartphones) that request services or resources from the server. It is widely used in larger, more complex networks, such as corporate environments and web applications (e.g., websites, email servers). Advantages: Centralized control and management. Easier to secure and manage, especially for large networks. Better suited for scalability and handling large amounts of traffic. Disadvantages: Requires dedicated servers and more complex setup. If the server goes down, clients lose access to resources. 10 Peer-to-Peer Client-Server 11 Network classification by size and coverage area Network Type Definition Example Range A network for personal devices Bluetooth connection between a PAN (Personal Area Network) A few meters (around a person). within a small area. phone and smartwatch. A network that connects devices Office network with computers and Up to several kilometers (building LAN (Local Area Network) within a limited area such as a printers connected to a router. or campus). building. Company branches within a city MAN (Metropolitan Area A network that covers a city or Up to tens of kilometers (city- connected via network Network) large campus. wide). infrastructure. A network that covers broad The Internet, connecting networks Can cover countries, continents, WAN (Wide Area Network) areas, connecting multiple LANs. across the world. or even globally. 12 Local Area Networks A local area network (LAN) is confined to a single geographical location. SOHO Enterprise LAN Datacenter 13 Activity: Quick Search Point-to-Point Star Topology Topology Mesh Topology 14 Network Topologies Topology Description Advantages Disadvantages Example If the backbone fails, the All devices share a single Simple to set up, uses less cabling whole network goes down; Bus communication line or backbone, Early Ethernet networks. than other topologies. performance decreases with and data is sent to all devices. more devices. Devices are connected in a A failure in any one Fiber Distributed Data circular loop, with data traveling in Easy to install and troubleshoot, Ring connection can disrupt the Interface (FDDI) and some one direction until it reaches its predictable data transmission times. entire network. LANs. destination. Every device is connected to Expensive and complex to High redundancy, reliable, no single Military and mission-critical Mesh every other device, allowing set up due to the number of point of failure. networks. multiple paths for data to travel. connections needed. All devices are connected to a Easy to manage and troubleshoot, Central hub is a single point Most modern home and Star central hub or switch, which failure of one device doesn’t affect of failure; if it goes down, the office networks using routers manages data flow. the network. entire network is affected. or switches. 15 Network Topologies Ring Bus Star Mesh 16 Network Topologies: Point-to-Point 17 Network Topologies: Star 18 Lesson Summary Network: Connected devices sharing data (computers, protocols, transmission medium) Client-Server Network: Central server provides resources and services to client devices Local Area Network (LAN): Connects devices within a limited area (home, office) Network Topology: Layout of connections between network devices (star, mesh, point-to-point) 19 Lesson 1.2 OSI Model Concepts 20 The OSI Model Packet Flow 7 Application 1 Physical Sender Receiver 6 Presentation 2 Data Link 5 Session 3 Network 4 Transport 4 Transport 3 Network 5 Session 2 Data Link 6 Presentation 1 Physical 7 Application 21 The OSI Model Mnemonic Please Do Not Throw Sausage Pizza Away P D N T S P A Physical Data Link Network Transport Session Presentation Application 22 Responsibility of the Network 7 Application 6 Presentation 5 Session 4 Transport 3 Network Responsibility 2 Data Link of the Network 1 Physical 23 Layer 1 – Physical 7 Application Functions and Examples Transmit bits from sending source over network 6 Presentation communications to physical layer of receiving device Data transmitted using cables or wireless media 5 Session Examples: Coax and fiber cables, hubs and repeaters, modem, transceiver 4 Transport 3 Network 2 Data Link Bit Stream Sender Receiver 1 Physical 24 Layer 2 – Data Link 7 Application Functions and Examples 6 Presentation Transfers data between nodes on the same logical segment using hardware addresses 5 Session Encapsulation: organizes stream of bits arriving from the Physical layer into frames Examples: NIC, bridge, switch, wireless access point 4 Transport 3 Network G1 Host AA 2 Data Link G2 Host AB 1 Physical G3 Host AC 25 Layer 3 – Network Functions and Examples 7 Application Moving data around a network of networks 6 Presentation using network and host IDs Packets given a destination IP address and 5 Session forwarded to the destination network Examples: Router, IP, ACL, Basic Firewall 4 Transport 3 Network Network 9 2 Data Link Router A Router B: 1.254 2.254 1 Physical Network 1 Network 1 (Hosts 1.1, 1.2, 1.3) (Hosts 2.1, 2.2, 2.3) 26 Layer 4 - Transport 7 Application Functions and Examples 6 Presentation Tracks communication between applications on source and destination hosts 5 Session Segments data and manages each data piece Reassembles segments into application data 4 Transport Examples: Multilayer switches, advanced 3 Network firewalls, intrusion detection systems (IDSs) 2 Data Link 1 Physical 27 Layer 4 – Transport 28 Responsibility of Host 7 Application Responsibility 6 Presentation of the Host 5 Session 4 Transport 3 Network 2 Data Link 1 Physical 29 Layer 5 - Session 7 Application Functions and Examples 6 Presentation Establishes and manages the 5 Session connections between applications Examples: ASP, ADSP, NetBIOS, PAP 4 Transport 3 Network Authentication Request 2 Data Link Session Established 1 Physical Respond 30 Layer 6 - Presentation Functions and Examples 7 Application Delivers data across network 6 Presentation connections Examples: MIME, 5 Session Encryption/Decryption Services 4 Transport Application Layer Data Application Layer Data 3 Network Presentation Layer Presentation Layer 2 Data Link Decrypted, Decoded, and Encrypted, Encoded, Compressed Decompressed 1 Physical Session Layer Data Session Layer Data 24 Layer 7 - Application Functions and Examples 7 Application Interacts directly with end-user’s 6 Presentation software applications for network 5 Session service Examples: SMTP, DNS, FTP 4 Transport 3 Network 2 Data Link Human Machine 1 Physical Readable Readable 32 Activity: Unscramble the OSI Model Network Physical Presentation Physical Data Link Network Transport Session Presentation Application 33 Lesson 1.3 SOHO Networks 34 Think About It What is a SOHO router? And what is it used for? 35 SOHO Router – Physical Layer 36 SOHO Router – Data Link Layer Ethernet switch Wireless access point Each host interface identified by a MAC address 37 SOHO Router – Network Layer Forwards between local private network and public internet Runs a DHCP server to provide each host with an IP address Router’s WAN interface given a public IP address 38 SOHO Router – Transport and Application Application Layer Request and Response Transport Transport Layer Layer Segmentation Reassembly 39 SOHO Router – The Internet WAN: SOHO connection to Internet Public switched telephone network (PSTN) High-bandwidth trunks connecting IXPs ISP links between networks in IXP datacenter 40 Binary Numbers – Base 10 Ten-millions One- Hundred- Ten- One- Hundreds Tens Ones millions thousands thousands thousands Digit Digit Digit Digit Digit Digit Digit Digit x 10,000,000 x 1,000,000 x x x x x x 100,000 10,000 1,000 100 10 1 41 Binary Numbers – Base 10 128 64 32 16 8 4 2 1 Digit x 128 Digit x 64 Digit x 32 Digit x 16 Digit x 8 Digit x 4 Digit x 2 Digit x 1 42 Binary Conversion Let's look at how to convert 205 into binary. 128 64 32 16 8 4 2 1 Digit x 128 Digit x 64 Digit x 32 Digit x 16 Digit x 8 Digit x 4 Digit x 2 Digit x 1 1 1 0 0 1 1 0 1 43 Activity: Binary Conversion Convert 132 into binary. 128 64 32 16 8 4 2 1 Digit x 128 Digit x 64 Digit x 32 Digit x 16 Digit x 8 Digit x 4 Digit x 2 Digit x 1 1 0 0 0 0 1 0 0 44 Lesson 1.4 Troubleshooting Methodology 45 Discussion: Think About It What is troubleshooting? What steps should be involved in the troubleshooting process? 46 Troubleshooting Methodology Document Establish a Test the Identify Establish a Implement findings, theory of theory to Verify the the plan of the actions, probable determine solution problem action solution and cause cause outcomes 47 Identify the Problem Gather information System documentation Installation and maintenance logs Vendor support sites Question users Open questions to uncover information Closed question to invite a yes or no or fixed response 48 Identify Problem Symptoms Identify symptoms Physical inspection Logs and diagnostic software Try to duplicate the problem Determine if anything has changed Did it ever work? What has changed since it was last working? Approach problems individually Verify symptoms are related before treating them as one single issue 49 Establish a Theory of Probable Cause Troubleshooting styles Question the obvious Methodically prove the functionality of each component OSI Model Approach Top-down approach Bottom-up approach 50 Test the Theory to Determine the Cause Question the obvious Use one or more method-based approaches Don’t jump to conclusions Escalation Problem is beyond your knowledge or ability Problem falls under a system warranty Scope of the problem is very large Customer is difficult or abusive 51 Implement, Verify, and Document Implement changes Implement fixes Escalate if higher authorization is needed Verify the solution Make sure the system seems to work for you Make sure the system seems to work for customer Document Document findings, actions, and outcomes Logs are useful for future troubleshooting 52 Activity: Troubleshooting Several office employees report their computers are unable to connect to the Internet, affecting workflow and productivity. Document Establish a Test the Identify Establish a Implement findings, theory of theory to Verify the the plan of the actions, probable determine solution problem action solution and cause cause outcomes 53 Summary Remember OSI model’s 7 layers (physical, data link, network, transport, session, presentation, and application) Plan network structure and troubleshoot issues using OSI model layers Implement methodical approach to troubleshooting (identification, planning, execution, verification, and documentation) Use strategies like top-to-bottom, bottom-to-top, and divide-and- conquer 54