Networking

Coaxial Cable Coaxial Cable, or Coax Cable, consists of a central conductor, insulating layer, metal shield, and an outer insulating layer. It was one of the earliest cable types used for network connectivity and still sees use today, especially in cable television (CATV) and broadband internet. Types of Coaxial Cable RG-59: Most Common Use: Cable TV. Advantages: Suitable for short-distance signals. RG-6: Most Common Use: Satellite TV and broadband internet. Advantages: Higher bandwidth and suitable for longer distances compared to RG-59. Uses of Coaxial Cable Cable Television: Historically used for transmitting television signals. Broadband Internet: Used in cable modems for internet access. Networking: In some older Ethernet setups (10BASE2), coaxial cable was used. Advantages and Disadvantages Advantages: Good Shielding: The metal shield prevents interference, making it reliable for signal transmission. Distance: It can transmit data over longer distances without significant loss in signal quality. Disadvantages: Bulky: Coaxial cables are thicker and less flexible compared to twisted pair cables. Limited Speed: They do not support high-speed data transmission as efficiently as fiber optics. For more details on Coaxial Cable, see Connectivity and Cable Types. ...

Twisted Pair Cable Twisted Pair Cable is a type of wiring used in many networks, including Ethernet. It consists of pairs of copper wires twisted together to reduce electromagnetic interference (EMI). It is one of the most commonly used cables in networking today, especially for local area networks (LANs). Types of Twisted Pair Cable Unshielded Twisted Pair (UTP): Most Common Use: Ethernet networks (Cat 5e, Cat 6, etc.). Advantages: Cost-effective, easy to install, and widely supported. Limitations: Susceptible to electromagnetic interference. Shielded Twisted Pair (STP): ...

🌐 Network Device: Gateway A Gateway is a device that operates at the Network Layer of the OSI model and acts as an entry/exit point between different networks, typically between a local network and the Internet. It is responsible for protocol conversion, address translation, and data routing, ensuring seamless communication between different systems or networks that may use different protocols. 🔹 What is a Gateway? A Gateway is a network device that connects two or more networks, which may be using different communication protocols or data formats. It translates data between these networks to enable communication. Gateways operate at various layers of the OSI model, often functioning between the Network Layer and higher layers, allowing communication between systems that otherwise wouldn’t be able to interact. ...

Local Area Network (LAN) Topologies A Local Area Network (LAN) is a network that connects computers and devices within a limited geographical area, such as a home, office, or campus. The layout or structure of a LAN is determined by its topology. LAN topologies define the way in which different devices and nodes are interconnected, and they play a crucial role in network performance, management, and troubleshooting. 🔹 Key Characteristics of LAN Geographical Scope: Limited to a single building or group of buildings (usually < 10 km). Ownership: Typically owned by a single organization or individual. Data Transfer Speed: High-speed communication, ranging from 100 Mbps (Fast Ethernet) to 10 Gbps (Gigabit Ethernet). Connectivity Medium: Wired (Ethernet cables) or wireless (Wi-Fi). 🔹 Common LAN Topologies There are several types of LAN topologies, each with its own advantages, disadvantages, and use cases. The main LAN topologies include: ...

Personal Area Network (PAN) A Personal Area Network (PAN) is a small-scale network typically used to connect devices within a very limited area, such as a single room or a few meters around a person. It is primarily used for personal devices like smartphones, laptops, tablets, smartwatches, printers, and other gadgets, enabling them to communicate with each other. 🔹 Key Characteristics of PAN Geographical Scope: Very short range (usually < 10 meters). Ownership: Fully personal and user-managed. Data Transfer Speed: Varies — from a few Kbps (classic Bluetooth) to over 24 Mbps (Bluetooth 5.0+). Connectivity Medium: Primarily wireless (Bluetooth, IR, ZigBee); sometimes wired (USB). Use Case: Connecting personal devices like smartphones, tablets, headsets, smartwatches, laptops. 🔹 Types of PAN 1. Wired PAN (WPAN) A Wired Personal Area Network (WPAN) uses physical cables to connect devices. The most common example is a USB (Universal Serial Bus) network, which connects devices like printers, storage devices, and audio systems to computers. ...

Metropolitan Area Network (MAN) A Metropolitan Area Network (MAN) is a type of network that spans a city or large campus, connecting multiple LANs within a metropolitan region. It provides higher data rates and interconnectivity between LANs located in different buildings or areas of a city. 🔹 Key Characteristics of MAN Geographical Scope: Covers 5–50 km (a city, industrial area, or university campus). Ownership: Usually maintained by governments, ISPs, or large enterprises. Speed: Medium to high (10 Mbps to 1 Gbps or more). Cost: Higher than LAN, but lower than WAN. Transmission Mediums: Fiber optics, coaxial cable, wireless microwave links. 🔹 Functions of a MAN Connect multiple LANs across a city (e.g., citywide library branches, hospitals). Acts as a high-speed backbone for regional communication. Provides internet access to LANs via a centralized gateway. Enables resource and data sharing between locations in the same city. 🖼️ Textual Diagram – MAN Connecting Multiple LANs +------------+ +------------+ +------------+ | Office 1 | | Office 2 | | Office 3 | | (LAN) | | (LAN) | | (LAN) | +------------+ +------------+ +------------+ \ | / \ | / +----------------------------------+ Metropolitan Area Network (Fiber/Wireless Links) | [Internet Gateway] 🔹 Technologies Used in MAN Technology Description Metro Ethernet Ethernet-based MAN services over fiber provided by ISPs. Wireless MAN (WMAN) WiMAX, microwave, or mmWave links across a city. SONET/SDH High-speed optical transmission for regional MAN backbones. FDDI (legacy) Fiber Distributed Data Interface used in earlier MANs. 🔹 MAN vs LAN vs WAN Feature MAN LAN WAN Coverage Area City or metropolitan area Room, building, campus Country, continent, globe Ownership Government/ISP Private ISP or public Speed Medium to high High Medium to low Cost Moderate Low High Technologies Fiber, wireless, MetroE Ethernet, Wi-Fi MPLS, satellite, leased lines 🔹 Advantages of MAN Efficient Citywide Connectivity: Connects multiple LANs across a region. High-Speed Data Transfer: Faster than WAN and suitable for regional operations. Cost Sharing: Often shared by multiple institutions or services. Supports Public and Private Use: Can be used by city governments, ISPs, or companies. 🔹

Wide Area Network (WAN) A Wide Area Network (WAN) is a telecommunications network that spans a large geographic area, often across countries or continents. It connects multiple smaller networks like LANs and MANs, enabling long-distance communication and data exchange. 🔹 Key Characteristics of WAN Geographical Scope: Covers vast areas — cities, countries, or the globe. Ownership: Often owned and maintained by telecom providers (ISPs). Speed: Generally lower than LAN, but improving with fiber, MPLS, and 5G. Cost: High due to infrastructure complexity and provider services. Mediums Used: Optical fiber, leased lines, satellite, MPLS, 4G/5G. 🔹 Functions of a WAN Connects branches of businesses, institutions, and governments across locations. Supports enterprise resource planning (ERP), cloud services, and communication systems. Facilitates internet access for homes and organizations. Enables remote work and video conferencing. 🖼️ Textual Diagram – WAN Connecting Multiple LANs [LAN - New York] [LAN - London] [LAN - Tokyo] | | | +--+--+ +---+---+ +---+---+ |Router| |Router | |Router | +--+--+ +---+---+ +---+---+ \ | / \ | / +-----------------+------------------+ [WAN] | [Internet Backbone] 🔹 Technologies Used in WAN Technology Description MPLS Multi-Protocol Label Switching – fast routing over WANs. Leased Lines Dedicated high-speed connections between locations. VSAT Satellite-based communication, useful in remote areas. VPN Secure tunneling over public WANs like the internet. 5G/4G LTE Wireless wide-area communication, especially for mobile WANs. 🔹 Protocols in WAN Communication IP (Internet Protocol) – basis for addressing and routing across WANs. TCP/UDP – provide end-to-end communication. BGP (Border Gateway Protocol) – used for routing between different autonomous systems on the internet. PPP (Point-to-Point Protocol) – used in leased line WAN links. Frame Relay / ATM – older but foundational WAN technologies. 🔹 Advantages of WAN Global Connectivity: Enables communication between far-off sites. Centralized Data: Facilitates access to centralized servers and applications. Scalability: Can grow with business or geographic expansion. Supports Remote Work: Essential for distributed teams. 🔹 Disadvantages of WAN High Cost: Due to infrastructure, leasing, and service provider fees. Complexity: Requires advanced management, configuration, and security. Latency: Longer distances can lead to higher latency and lower throughput. Dependency on ISPs: Quality and uptime depend on third parties. 🔹 WAN vs LAN vs MAN (Quick Comparison) Feature WAN LAN MAN Area Covered Country/Continent/Global Building or Campus City or Metro Area Speed Medium to High (variable) High Medium to High Ownership Telecom Providers (ISPs) Private Public or Private Cost High Low Medium Reliability Depends on provider High Moderate 🔹 Real-World Examples of WAN The Internet itself is the largest example of a WAN. Corporate WANs that connect multinational branch offices using MPLS or VPNs. Banking networks linking ATMs and branches securely. Military communication systems spanning regions and countries. 🔹 Summary A WAN is critical for enabling large-scale, cross-border communication and data exchange. It plays a foundational role in the internet, cloud computing, remote collaboration, and global business operations. While it introduces complexity and cost, its ability to unify geographically dispersed systems makes it indispensable. ...

Local Area Network (LAN) A Local Area Network (LAN) is a network confined to a small geographical area, such as a home, office, or campus. It enables fast, reliable communication and resource sharing among devices. 🔹 Key Characteristics of LAN Geographical Scope: Typically within 1 km² (building, floor, or campus). Ownership: Usually privately owned and managed. Data Transfer Speed: High — typically 100 Mbps to 10 Gbps or more. Latency: Low, due to proximity of devices. Transmission Medium: Twisted pair cables, fiber optics, or wireless (Wi-Fi). Maintenance: Managed internally by network administrators. 🔹 Functions of a LAN Sharing files, printers, and internet access. Centralized software and user management via servers. Facilitates local email and internal chat systems. Local hosting of web services and databases. 🖼️ Textual Diagram – Typical LAN Setup +-----------+ +-----------+ | Laptop | | Printer | +-----------+ +-----------+ \ / \ / +---------------------+ | Ethernet | ← Switch/Hub +---------------------+ / \ +-----------+ +-----------+ | Desktop 1 | | Desktop 2 | +-----------+ +-----------+ | +------------+ | Router | +------------+ | [Internet] 🔹 Types of LAN 1. Wired LAN Uses physical cables (typically Ethernet). Offers high speed, low interference. Common in offices and server rooms. 2. Wireless LAN (WLAN) Uses radio waves (Wi-Fi). More flexible and mobile. Common in homes and cafes. 🔹 LAN Protocols Protocol Description Ethernet (IEEE 802.3) Most widely used wired LAN protocol. Uses CSMA/CD. Wi-Fi (IEEE 802.11) Wireless LAN standard. Uses CSMA/CA. Token Ring (IEEE 802.5) Older LAN protocol; now mostly obsolete. MAC Addressing Uniquely identifies devices at the Data Link Layer. 🔹 Advantages of LAN High Speed: Up to 10 Gbps with modern Ethernet. Low Cost: Infrastructure and maintenance are affordable. Security: Managed internally with firewalls, access control. Resource Sharing: Centralized access to printers, storage, and internet. 🔹 Disadvantages of LAN Limited Range: Only suitable for small areas. Initial Setup Cost: Requires cabling, switches, routers. Maintenance: Needs network administration knowledge. 🔹 Use Cases Educational Institutions: For connecting labs, classrooms, libraries. Businesses: Centralize data and applications on servers. Homes: Sharing internet, streaming, file transfers between devices. 🔹 LAN Topologies LANs can be implemented using different topologies: ...

In virtualized environments, it’s common to have a VM running behind NAT, especially when using tools like QEMU, VirtualBox, or cloud labs. This setup means the VM can reach the host, but the host cannot directly initiate connections to the VM — including to web services like the Proxmox web GUI running on port 8006. Fortunately, this limitation is easy to bypass using reverse SSH tunneling. 🧠 Objective We want to: ...

🧩 VM Behind NAT? 🖥️ Scenario Your VM is running as root user. Your host machine has a user named rohan. The VM is behind NAT — it can talk to the host, but the host can’t directly talk to the VM. You want the host to be able to connect to the VM anyway. No worries — you can use a reverse SSH tunnel to solve this! ✅ Goal Allow your host (rohan@host) to SSH into your VM (root@vm) even though the VM is behind NAT. ...