Network Systems PDF

1. Basic Network Concepts and Models Network Types: ○ Personal Area Network (PAN): Small range (like 3-5 meters), usually connects personal devices like phones, smartwatches, headphones. Think Bluetooth. ○ Local Area Network (LAN): Covers small to medium area...

1. Basic Network Concepts and Models Network Types: ○ Personal Area Network (PAN): Small range (like 3-5 meters), usually connects personal devices like phones, smartwatches, headphones. Think Bluetooth. ○ Local Area Network (LAN): Covers small to medium areas, max range ~100m. Mostly Ethernet-based (wired/wireless). You’ll see these at home, in small offices. ○ Campus Area Network (CAN): Think of a larger network covering a campus (like schools, universities) or multiple buildings. ○ Wide Area Network (WAN): These are huge, spanning cities, countries, even continents. WANs use a bunch of different technologies to keep things connected. OSI vs. TCP/IP Models: ○ OSI Model: 7 layers (Physical, Data Link, Network, Transport, Session, Presentation, Application). Each layer has its own job: Application (7): Manages network requests from software applications. Physical (1): Deals with raw bits and actual hardware. ○ TCP/IP Model: This one’s more compact (4 layers: Network Access, Internet, Transport, Application). It’s widely used and covers what we actually need in real networking, but OSI is still a go-to for learning. Standards and Organizations: ○ IANA: Assigns IP addresses. ○ IEEE: Sets physical equipment standards (like MAC addresses). ○ ANSI, ITU, ISO: Manage international and U.S. standards for everything from Wi-Fi to fiber optics. Basically, they help make sure all our gear plays nice with each other. Flashcard Prompts: What are the OSI Model’s seven layers? Describe the difference between PAN, LAN, CAN, and WAN. 2. Physical Layer (Layer 1) What it Does: Sends and receives raw bits (0s and 1s) over a medium. It’s responsible for all hardware concerns, like cables and voltage. Transmission Types: ○ Simplex: One-way transmission (like a radio). ○ Half-Duplex: Two-way, but only one at a time (like walkie-talkies). ○ Full Duplex: Two-way communication at the same time (like a phone call). Transmission Media:  ○ Copper (Twisted Pair): Cheap, common for Ethernet, but can pick up interference. Comes in UTP (unshielded) and STP (shielded) forms. ○ Fiber Optic: Fast, long-range. Can be single-mode (long distances, high speeds) or multi-mode (shorter distances). ○ Wireless: Works over radio frequencies (like Wi-Fi at 2.4 GHz or Bluetooth at 2.45 GHz). Connectors: ○ RJ-45: Main connector for Ethernet cables. ○ RJ-11: Smaller, used for landlines. Flashcard Prompts: What are Simplex, Half-Duplex, and Full Duplex modes? What’s the difference between UTP and STP cables? 3. Data Link Layer (Layer 2) Role: Manages data transfer within the same network. This layer has two sublayers: ○ MAC (Media Access Control): Deals with hardware-level access to the network. ○ LLC (Logical Link Control): Ensures data is formatted correctly for Layer 3. Switching & Frame Structure: ○ Switches vs. Hubs: Switches are smart, using MAC addresses to send data directly to the device that needs it. Hubs are “dumb”—they send data to all devices. ○ Frame Structure: Every frame has a header with MAC addresses and a trailer with error-check info. Frames are like “envelopes” for network data. Key Protocols: ○ Ethernet: Standard for most local networks, using MAC addresses. ○ HDLC (High-Level Data Link Control): Often used on leased lines for WAN connections. ○ MPLS (Multi-Protocol Label Switching): Speeds up data flow by using labels instead of IP addresses. Spanning Tree Protocol (STP): Stops loops in networks with multiple paths by “blocking” some links. Flashcard Prompts: What does the Data Link Layer do? How does STP prevent network loops? 4. Network Layer (Layer 3)  Main Job: Routes data between different networks, based on IP addresses. IPv4 and IPv6: ○ IPv4: 32-bit addresses, e.g., 192.168.1.1. Has ~4.29 billion possible addresses, but we’ve run out. ○ IPv6: 128-bit addresses, written in hexadecimal (e.g., 2001:0db8::85a3). Tons more space for devices. Subnetting & Addressing: ○ Subnet Mask: Divides an IP into network and host sections (e.g., 255.255.255.0). ○ CIDR Notation: A more efficient way to write subnets (like /24 for 255.255.255.0). ○ NAT (Network Address Translation): Translates private IPs (like 192.168.x.x) into a public IP for internet access. Flashcard Prompts: What’s the difference between IPv4 and IPv6? Explain what a subnet mask does. 5. Transport Layer (Layer 4) Goal: Ensures data moves from one end to the other reliably or quickly. Key Protocols: ○ TCP (Transmission Control Protocol): Reliable, uses a three-way handshake to establish connections, resends lost data. Good for things that can’t miss a beat, like file transfers. ○ UDP (User Datagram Protocol): Fast, but doesn’t check for lost data. Perfect for streaming where some data loss is okay. Ports: ○ Ports identify different applications. E.g., HTTP is port 80, HTTPS is port 443. ○ Well-known Ports (0–1023): Used by major protocols. ○ Registered Ports (1024–49151): Managed by IANA for specific services. ○ Dynamic/Private Ports (49152–65535): Used temporarily by devices. Flashcard Prompts: What’s the difference between TCP and UDP? Why do we need port numbers? 6. Application Layer (Layer 7)  Common Protocols: ○ HTTP/HTTPS: For web traffic; HTTPS is the secure version. ○ DNS: Translates domain names (like google.com) to IP addresses. ○ DHCP: Automatically assigns IP addresses to devices on a network. ○ FTP: Transfers files; has secure versions (FTPS/SFTP) that add encryption. Architectures: ○ Client-Server: Centralized server provides services, clients connect to it (think Google Drive). ○ Peer-to-Peer: Decentralized, each node can act as both client and server (e.g., torrenting). Flashcard Prompts: What’s the purpose of DNS? Describe client-server vs. peer-to-peer architectures. 7. Troubleshooting Methodology Troubleshooting Steps: ○ Identify the Problem: Gather info, replicate if possible. ○ Establish a Theory: Form an educated guess on the cause. ○ Test the Theory: See if it fixes the problem; if not, try something else. ○ Implement Solution: If the theory works, go ahead with the fix. ○ Verify Full System Functionality: Check that everything’s back to normal. ○ Document Findings: Record the problem and solution for future use. Useful Tools: ○ Packet Sniffer (Wireshark): Captures network data for analysis. ○ Ping & Traceroute: Test connection and paths to other devices. ○ Protocol Analyzer: Checks what protocols are active and if they’re working correctly. Flashcard Prompts: What are the main steps in troubleshooting? Name three useful troubleshooting tools. 8. API and Scripting Basics API Overview: ○ What it is: APIs are like middlemen that let software components talk to each other.  ○ Types of APIs: REST: The most common; stateless, uses HTTP. SOAP: Old-school, uses XML, mostly phased out for REST. ○ Security: API Keys: Identifies who’s accessing the API. Tokens: Used to authenticate that the user has access rights. Automation: APIs are huge for automating things like data sync between apps, automatic backups, etc. Flashcard Prompts: What does API stand for, and what does it do? Describe the difference between REST and SOAP APIs.