Skip to content

Networking

alt text

Basic Networking

What is a Network?

Definition: According to Merriam Webster, a Network is usually an informally interconnected group or association of different entities (e.g., a person, computers, radio stations).

Computer Network: A system of peripherals or computers interconnected with each other.

  • Has a standard communication channel established between them.
  • Used to exchange different types of information and data.
  • Example: Dominos has a network of 1232 branches across India.

Importance of Computer Networks

  • connects all different network-enabled devices.
  • Enables data and information sharing between devices.
  • Considered a core part of technical interviews and daily life.

Network Classifications

Network types are classified based on the area of distribution.

Distance and Region Breakdown

  • 1m (Square meter): Personal Area Network
  • 10m (Room) - 1km (Campus): Local Area Network
  • 10km (City): Metropolitan Area Network
  • 100km (Country) - 1000km (Continent): Wide Area Network
  • 10,000km (Planet): The Internet (Global Area Network)
flowchart LR
    A["1m<br/>PAN"] --> B["10m-1km<br/>LAN"]
    B --> C["10km<br/>MAN"]
    C --> D["100-1000km<br/>WAN"]
    D --> E["10000km<br/>GAN"]
    style A fill:#1a7fab,color:#fff
    style B fill:#2a94c5,color:#fff
    style C fill:#3da8d5,color:#fff
    style D fill:#4eb6e0,color:#fff
    style E fill:#5bc4e6,color:#fff

Types of Networks

  1. PAN (Personal Area Network)
    • Lets devices connect and communicate over the range of a person.
    • Example: Connecting Bluetooth devices.
  2. LAN (Local Area Network)
    • A privately owned network operating within and nearby a single building (home, office, factory).
    • alt text
    • Widely used to connect computers/laptops and consumer electronics.
    • Enables sharing of resources (printers, fax machines) and information exchange.
    • Enterprise Networks: LANs used by companies or organizations.
    • Types:
      • Wireless LAN: No wires involved; achieved using Wi-Fi. Popular where installing wire is difficult.
      • Wired LAN: Achieved using LAN cable.
  3. MAN (Metropolitan Area Network)
    • Connects and covers the whole city.
    • Example: TV Cable connection over the city.
  4. WAN (Wide Area Network)
    • Spans a large geographical area, often a country or continent.
    • Example: The Internet is the largest WAN.
  5. GAN (Global Area Network)
    • Also known as the Internet.
    • Connects the globe using satellites.
    • Called the Network of WANs.

alt text

VPN (Virtual Private Network)

Definition

A VPN is a private WAN built on the internet.

  • Allows creation of a secured tunnel (protected network) between different networks using the internet (public network).
  • Enables clients to connect to an organization’s network remotely.
  • alt text

Advantages

  • Connects offices in different geographical locations remotely.
  • Cheaper compared to WAN connections.
  • Used for secure transactions and confidential data transfer between multiple offices.
  • Keeps organization information secured against threats or intrusions via virtualization.
  • Encrypts internet traffic and disguises online identity.

Types of VPN

  1. Access VPN
    • Provides connectivity to remote mobile users and telecommuters.
    • Alternative to dial-up or ISDN connections.
    • Low-cost solution with a wide range of connectivity.
  2. Site-to-Site VPN (Router-to-Router)
    • Connects the network of one office to another in different locations.
    • Common in large companies with multiple branches.
    • Sub-categories:
      • Intranet VPN: Connects remote offices using shared infrastructure (internet connectivity and servers) with the same accessibility policies as a private WAN.
      • Extranet VPN: Uses shared infrastructure over an intranet to connect suppliers, customers, partners, and other entities using dedicated connections.
flowchart TD
    VPN["Virtual Private Network<br/>VPN"]
    VPN --> ACCESS["Access VPN<br/>Remote Users"]
    VPN --> SITE["Site-to-Site VPN<br/>Office to Office"]
    SITE --> INTRANET["Intranet VPN<br/>Internal Offices"]
    SITE --> EXTRANET["Extranet VPN<br/>Partners & Suppliers"]
    style VPN fill:#b8860b,color:#fff
    style ACCESS fill:#daa520,color:#fff
    style SITE fill:#daa520,color:#fff
    style INTRANET fill:#ffa500,color:#000
    style EXTRANET fill:#ffa500,color:#000

Network Fundamentals

alt text

  • Node: Any communicating device in a network.
    • Point of intersection in a network.
    • Can send/receive data.
    • Examples: Computers, laptops, printers, servers, modems.
  • Link: The connectivity (edge) between two nodes in the network.
    • Includes the type of connectivity (wired/wireless).
    • Includes protocols used for communication.

Network Topology

Definition: The physical layout of the network connecting different nodes using links. It depicts connectivity between computers, devices, and cables.

Types of Topologies

  1. Bus Topology
    • All nodes connected using a central link known as the bus.
    • Pros: Useful for a smaller number of devices.
    • Cons: If the main cable gets damaged, the whole network is damaged.
  2. Star Topology
    • All nodes connected to one single central node.
    • Pros: More robust; easy to troubleshoot. Mainly used in home/office networks.
    • Cons: If the central node fails, the complete network is damaged.
  3. Ring Topology
    • Each node connected to exactly two nodes, forming a ring structure.
    • Cons: Rare usage; expensive; hard to install and manage. If one node is damaged, the whole network is damaged.
  4. Mesh Topology
    • Each node connected to one or many nodes.
    • Pros: Robust (failure in one link only disconnects that node).
    • Cons: Rare usage; installation and management are difficult.
  5. Tree Topology
    • Combination of star and bus topology (Extended Bus Topology).
    • All smaller star networks are connected to a single bus.
    • Cons: If the main bus fails, the whole network is damaged.
  6. Hybrid Topology
    • Combination of different topologies to form a new one.
    • Pros: Ignores drawbacks of specific topologies and picks strengths from others.

IP Addressing

IPv4 Address

  • Definition: A 32-bit dynamic address of a node in the network.
  • Structure: 4 octets of 8-bits each (values up to 255).

IPv4 Classes

Classes are based on the first octet and the number of hosts supported.

Class IPv4 Start Address IPv4 End Address Usage
A 0.0.0.0 127.255.255.255 Large Network
B 128.0.0.0 191.255.255.255 Medium Size Network
C 192.0.0.0 223.255.255.255 Local Area Network
D 224.0.0.0 239.255.255.255 Reserved for Multicasting
E 240.0.0.0 255.255.255.254 Study and R&D

Private and Special IP Addresses

Private Address: Specific IPs reserved for private use only. Non-routable on the Internet.

Class Private IPv4 Start Address Private IPv4 End Address
A 10.0.0.0 10.255.255.255
B 172.16.0.0 172.31.255.255
C 192.168.0.0 192.168.255.255

Special Address: Range 127.0.0.1 to 127.255.255.255.

  • Known as loopback addresses.
  • Used for network testing.

Subnet

  • Definition: A network inside a network achieved by subnetting.
  • alt text
  • Purpose:
    • Divides a network into subnets.
    • Higher routing efficiency.
    • Enhances network security.
    • Reduces time to extract host address from routing table.

Reference Models

OSI Reference Model

Open System Interconnections (OSI) is a network architecture model based on ISO standards.

  • Deals with connecting systems open for communication.
  • Has seven layers.

Principles

  • Create a new layer if a different abstraction is needed.
  • Each layer has a well-defined function.
  • Functions chosen based on internationally standardized protocols.

The 7 Layers

  1. Physical (Hardware Layer)
    • Unit: Bit.
    • Description: Transmits raw bits over communication channel. Selects transmission mode (Simplex, Half Duplex, Full Duplex).
  2. Data Link (Hardware Layer)
  3. Network (Hardware Layer)
  4. Transport (Heart of OSI)
  5. Session (Software Layer)
  6. Presentation (Software Layer)
  7. Application (Software Layer).
flowchart TB
    L7["7. Application<br/>HTTP, SMTP, DNS, FTP"]
    L6["6. Presentation<br/>Encryption, Compression"]
    L5["5. Session<br/>Connections"]
    L4["4. Transport<br/>TCP, UDP"]
    L3["3. Network<br/>IP, Routers"]
    L2["2. Data Link<br/>Frames, MAC"]
    L1["1. Physical<br/>Bits, Cables"]
    L7 --> L6 --> L5 --> L4 --> L3 --> L2 --> L1
    style L7 fill:#ba68c8,color:#fff
    style L6 fill:#ba68c8,color:#fff
    style L5 fill:#ba68c8,color:#fff
    style L4 fill:#9c27b0,color:#fff
    style L3 fill:#7b1fa2,color:#fff
    style L2 fill:#6a4c93,color:#fff
    style L1 fill:#5d4e78,color:#fff

TCP/IP Reference Model

Compressed version of the OSI model with 4 layers.

  • Developed by US DoD in the 1960s.
  • Named after TCP (Transmission Control Protocol) and IP (Internet Protocol).

alt text

The 4 Layers

  • Link Layer: Decides which links (serial lines, Ethernet) to use to meet connectionless internet layer needs.
  • Internet Layer: Most important layer holding architecture together. Delivers IP packets to destinations.
  • Transport Layer: Enables peer entities to carry on a conversation (similar to OSI Transport).
  • Application Layer: Contains all higher-level protocols.
flowchart TB
    L4["4. Application<br/>HTTP, SMTP, DNS, FTP"]
    L3["3. Transport<br/>TCP, UDP"]
    L2["2. Internet<br/>IP, ICMP, ARP"]
    L1["1. Link<br/>Ethernet, Wi-Fi"]
    L4 --> L3 --> L2 --> L1
    style L4 fill:#ba68c8,color:#fff
    style L3 fill:#9c27b0,color:#fff
    style L2 fill:#7b1fa2,color:#fff
    style L1 fill:#6a4c93,color:#fff

OSI vs TCP/IP Comparison

OSI Reference Model TCP/IP Reference Model
7 layered architecture 4 layered architecture
Fixed boundaries and functionality for each layer Flexible architecture with no strict boundaries
Low Reliability High Reliability
Vertical Layer Approach Horizontal Layer Approach

Note: The Presentation and Session layers from OSI are not present in the TCP/IP model.

alt text

Protocols

HTTP and HTTPS

  • HTTP (HyperText Transfer Protocol)
    • Defines rules for transmitting info on the WWW.
    • Helps communication between web browsers and servers.
    • Stateless protocol (each command is independent).
    • Application layer protocol built on TCP.
    • Default Port: 80.
  • HTTPS (HyperText Transfer Protocol Secure)
    • Advanced, secured version of HTTP.
    • Uses SSL/TLS protocol on top of HTTP.
    • Encrypts communication and identifies network servers securely.
    • Default Port: 443.

SMTP (Simple Mail Transfer Protocol)

  • Sets rules for communication between servers to transmit emails.
  • Supports End-to-End and Store-and-Forward methods.
  • Always-listening mode.
  • Default Port: 25.

DNS (Domain Name System)

  • Decentralized, hierarchical naming system (Devices/Services directory of the Internet).
  • Translates domain names (e.g., codingismeditation.github.io) to IPs (e.g., 172.217.166.36).
  • Default Port: 53.

TCP (Transmission Control Protocol)

  • Set of rules for connecting to the Internet and transmitting data.
  • Creates a virtual network when multiple computers connect.
  • Uses three-way handshake model.
  • Reliable connection.
sequenceDiagram
    participant Client
    participant Server
    Client->>Server: SYN
    Server->>Client: SYN-ACK
    Client->>Server: ACK
    Note over Client,Server: Connection Established

UDP (User Datagram Protocol)

  • Based on Datagrams.
  • Used for multicasting and broadcasting.
  • Simple transmission without hand-shaking.
  • Less reliable than TCP.

TCP vs UDP

TCP / TCP/IP UDP
Connection-Oriented Protocol Connectionless Protocol
More Reliable Less Reliable
Slower Transmission Faster Transmission
Packet order preserved/rearranged Packet order not fixed; independent packets
Uses three-way handshake No handshake
Heavy-weight packets Light-weight packets
Error checking mechanism No error checking mechanism
Protocols: HTTP, FTP, Telnet, SMTP, HTTPS Protocols: DNS, RIP, SNMP, RTP, BOOTP, TFTP, NIP

alt text

ICMP (Internet Control Message Protocol)

  • Network layer protocol for error handling.
  • Used by network devices (routers) to diagnose issues.
  • Reports errors and tests if data reaches destination.
  • Default Port: 7.

DHCP (Dynamic Host Configuration Protocol)

  • Application layer protocol to auto-configure devices on IP networks.
  • Auto-assigns IPs, subnet masks, and DNS settings.
  • Enables use of TCP/UDP-based protocols.
  • Default Port: 67.

ARP (Address Resolution Protocol)

  • Network-level protocol.
  • alt text
  • Converts Logical Address (IP) to Physical Address (MAC).
  • Used to get MAC address of devices for local network communication.

FTP (File Transfer Protocol)

  • Application layer protocol.
  • Used to transfer files/data reliably between hosts.
  • Used to download files from remote servers.
  • Default Port: 27.

Hardware and Devices

Router vs Gateway

  • Router:
    • Connects two or more network segments.
    • Directs traffic; transfers data (packets) from source to destination.
    • Operates at Network Layer.
    • Sends data to similar networks.
  • Gateway:
    • Routes and regulates traffic.
    • Can send data between two dissimilar networks.

Hub vs Switch

Hub Switch
Operates at Physical Layer Operates at Data Link Layer
Half-Duplex transmission mode Full-Duplex transmission mode
Connects Ethernet devices Connects LAN devices
Less complex, less intelligent, cheaper Intelligent and effective
No software support for administration Administration software support present
Less speed (up to 100 MBPS) High speed (GBPS)
Less efficient (collisions possible) More efficient (avoids/reduces collisions)

MAC Address vs NIC

  • MAC (Media Access Control) Address:
    • 48-bit or 64-bit unique identifier.
    • Physical address embedded with the NIC.
    • Used at Data Link Layer.
  • NIC (Network Interface Card):
    • Hardware component enabling device connection to the network.

MAC Address vs IP Address

MAC Address IP Address
Media Access Control Address Internet Protocol Address
6 or 8-byte hexadecimal number 4 (IPv4) or 16 (IPv6) Byte address
Embedded with NIC Obtained from the network
Physical Address Logical Address
Operates at Data Link Layer Operates at Network Layer
Identifies the device Identifies device connectivity on the network

Firewall

  • Network security system monitoring incoming/outgoing traffic.
  • alt text
  • Blocks traffic based on security policies.
  • Acts as a wall between internet (public) and networking devices (private).
  • Can be hardware, software, or both.

Commands and Operations

ipconfig vs ifconfig

ipconfig ifconfig
Internet Protocol Configuration Interface Configuration
Used in Microsoft OS Used in MAC, Linux, UNIX OS
View/configure network interfaces View/configure network interfaces
TCP/IP summary, change DHCP/DNS settings

Casting Types

  • Unicasting: Message sent to a single node from source.
    • Use: Establishing new connection.
  • Anycasting: Message sent to any node from source.
    • Use: Content Delivery Systems (getting content from any server).
  • Multicasting: Message sent to a subset of nodes.
    • Use: Sending same data to multiple receivers.
  • Broadcasting: Message sent to all nodes in a network.
    • Use: DHCP and ARP in local network.

Browser Process (Entering google.com)

Steps followed when entering a URL:

  • Check Cache: Browser checks its cache for fresh content.
  • DNS Lookup:
    • If IP not in cache (browser/OS), request OS to do DNS lookup.
    • Uses UDP to get IP from DNS server.
  • TCP Connection:
    • Establish new connection between browser and server.
    • Uses three-way handshaking.
  • HTTP Request: Sent to server using TCP connection.
  • HTTP Response: Web server handles request and sends response.
  • Process Response:
    • Browser processes response.
    • Closes TCP connection or reuses it.
  • Cache & Render:
    • Browser caches data if cacheable.
    • Browser decodes and renders content.
flowchart TD
    A["Enter URL<br/>google.com"]
    B{"Content in<br/>Cache?"}
    C{"IP in Cache?"}
    D["Display<br/>Cached Content"]
    E["DNS Lookup<br/>Get IP Address"]
    F["Establish<br/>TCP Connection"]
    G["Send<br/>HTTP Request"]
    H["Receive<br/>HTTP Response"]
    I{"Cache<br/>Data?"}
    J["Cache<br/>Response"]
    K["Render &<br/>Display Page"]
    A --> B
    B -->|Yes| D
    B -->|No| C
    C -->|No| E
    C -->|Yes| F
    E --> F
    F --> G
    G --> H
    H --> I
    I -->|Yes| J
    I -->|No| K
    J --> K
    D --> K
    style A fill:#1976d2,color:#fff
    style K fill:#43a047,color:#fff

Global Connectivity Fact

  • Submarine Cables: As of 2021, there are 1.3 million kilometers of submarine optical fiber cables globally.
  • Scale: Enough to revolve around the earth more than 100 times.

Complete Networking Roadmap

flowchart TD
    START["🌐 NETWORKING<br/>Foundation"]

    START --> BASICS["Network Basics<br/>PAN|LAN|MAN|WAN|GAN"]
    BASICS --> CONN["Connection Methods<br/>VPN|Topologies"]
    CONN --> ADDRESSING["IP Addressing<br/>IPv4|Private|Loopback"]

    ADDRESSING --> MODELS["Reference Models<br/>OSI 7-Layer|TCP/IP 4-Layer"]
    MODELS --> PROTO["Protocols Layer"]

    PROTO --> APP["Application<br/>HTTP|SMTP|DNS|FTP"]
    PROTO --> TRANS["Transport<br/>TCP|UDP"]
    PROTO --> NET["Network<br/>ICMP|ARP|DHCP"]

    APP --> HW["Hardware & Devices<br/>Router|Gateway|Hub|Switch"]
    TRANS --> HW
    NET --> HW

    HW --> OPS["Operations<br/>Commands|Casting"]
    OPS --> BROWSER["Browser Process<br/>Cache→DNS→TCP→HTTP→Render"]
    BROWSER --> END["✅ Complete<br/>Network Understanding"]

    style START fill:#f39c12,color:#fff,stroke:#2c3e50,stroke-width:2px
    style BASICS fill:#34495e,color:#f39c12
    style CONN fill:#f39c12,color:#2c3e50
    style ADDRESSING fill:#34495e,color:#f39c12
    style MODELS fill:#f39c12,color:#2c3e50
    style PROTO fill:#34495e,color:#f39c12
    style APP fill:#2c3e50,color:#f39c12
    style TRANS fill:#2c3e50,color:#f39c12
    style NET fill:#2c3e50,color:#f39c12
    style HW fill:#f39c12,color:#2c3e50
    style OPS fill:#34495e,color:#f39c12
    style BROWSER fill:#f39c12,color:#2c3e50
    style END fill:#f39c12,color:#fff,stroke:#2c3e50,stroke-width:2px

The codingismeditation.github.io, authored by Kintsugi-Programmer, is less a comprehensive resource and more an Artifact of Continuous Research and Deep Inquiry into Computer Science and Software Engineering. It serves as a transparent ledger of the author's relentless pursuit of mastery, from the foundational algorithms to modern full-stack implementation.

Made with 💚 Kintsugi-Programmer