Networking Devices
Hub, Switch, Bridge, Router, Brouter, Gateway, Workstation
Hub
A hub is a basic networking device that connects multiple computers in a LAN and broadcasts data to all ports.
It receives data from one computer and broadcasts it to all other connected computers.
Operates at OSI Layer 1 (Physical Layer).
Does not learn MAC addresses or perform traffic filtering.
Only one device can transmit at a time, which can cause data collisions.
Used mostly in older networks; replaced by switches in modern setups.
Switch
A switch is a smarter device than a hub. It connects devices within a LAN and forwards data intelligently based on MAC addresses.
It connects multiple devices (like computers, printers, etc.) in a Local Area Network (LAN) and sends data only to the intended recipient, not to all devices.
Operates at OSI Layer 2 (Data Link Layer).
Reduces collisions by forwarding data to the correct port.
Supports full-duplex communication, improving speed and efficiency.
Can create VLANs (Virtual LANs) for logical network segmentation.
Bridge
A bridge in networking is a device used to connect two different LANs and make them act as a single network.
A bridge connects two LAN segments and filters traffic to reduce congestion.
Operates at OSI Layer 2 (Data Link Layer).
Learns MAC addresses to forward frames selectively.
Improves traffic flow between network segments.
Less scalable than switches; typically used in small networks.
Router
A router connects different networks and routes packets based on IP addresses.
Operates at OSI Layer 3 (Network Layer).
Routes data between local networks (LAN) and the internet (WAN).
Assigns IP addresses to devices via DHCP (Dynamic Host Configuration Protocol).
Supports dynamic routing protocols such as RIP, OSPF, and BGP.
Performs NAT (Network Address Translation) to map private to public IP addresses.
Provides firewall and security features in modern routers.
Brouter (Bridge Router)
A brouter is a hybrid device that routes known protocols and bridges unknown ones.
Functions at both OSI Layer 2 and Layer 3.
Reduces the need for a separate bridge and router.
Useful in legacy systems that support multiple protocols.
Not commonly used today; replaced by modern multifunction devices.
Gateway
A gateway connects networks that use different communication protocols and acts as a translator between them.
Operates at all layers of the OSI model, especially at Layer 7 (Application Layer).
Translates protocols, data formats, and network addresses.
Examples include VoIP gateways, email gateways, and cloud service gateways.
Enables communication between heterogeneous systems (e.g., TCP/IP ↔ AppleTalk).
Workstation
A workstation is a high-performance computer used by a single user, typically connected to a network.
Acts as a client node in a client-server network.
Accesses shared resources like files, printers, and databases.
Typically more powerful than standard PCs (higher RAM, CPU, GPU specs).
Commonly used in development, design, simulation, and research environments.
Network Topology
Network topology is the arrangement of the various elements (like nodes, links, etc.) in a computer network.
- It represents both the physical and logical structure of the network.
Types of Topology:
Bus Topology
Star Topology
Ring Topology
Mesh Topology
LAN (Local Area Network)
A Local Area Network (LAN) is a network that connects computers and other devices within a limited geographical area, such as a home, school, office, or building.
It allows devices like computers, printers, and servers to communicate, share files, and access shared resources, such as the internet or networked storage.
LANs are typically fast, privately managed, and designed for users in close physical proximity.
MAN (Metropolitan Area Network)
A Metropolitan Area Network (MAN) connects computers and devices across a larger area than a LAN, but smaller than a WAN.
Typically spans a city or a large campus.
Used to connect multiple LANs within that area.
Often owned and operated by a single organization (e.g., government or large corporation).
Provides high-speed connectivity between locations within the metropolitan region.
WAN (Wide Area Network)
A Wide Area Network (WAN) is a network that spans a large geographical area, such as a city, country, or even across continents.
Used to connect multiple LANs and MANs.
Typically uses technologies like leased lines, satellite links, or fiber optic cables.
The internet is the largest example of a WAN.
Protocol
A protocol in computer networking is a standard set of rules that define how computers communicate with each other over a network.
Protocol defines the Format and the order of messages exchanged between two or more communicating entities, as well as the action taken on the transmission and/or recieipt of a message or other event.
Protocols define and control how data is:
Formatted
Transmitted & Received
Processed between devices on a computer network
What each device should do when something goes wrong
The Network Edge
The Network Edge refers to the end part of a computer network where users and devices (like computers, smartphones, servers, or sensors) connect to the Internet.
- It is the starting or ending point of data in the network — where communication with the Internet begins or ends.
- End systems are also referred to as host because they host application programs such as web browsers, server and mail
Home Access Network
Home users can connect to the Internet using different technologies, depending on:
Location
Speed requirements
Service availability
Main Types:
DSL (Digital Subscriber Line)
Cable Internet Access
FTTH (Fiber to the Home)
Dial-Up Access
Satellite Internet
DSL (Digital Subscriber Line)
Popular in the 2000s and early 2010s, but usage is decreasing.
Uses existing telephone lines (twisted-pair copper wire).
Data and phone calls can share the same line using different frequencies.
Frequency Bands:
0–4 kHz: Voice calls
4–50 kHz: Upstream data (upload)
50 kHz–1 MHz: Downstream data (download)
Key Components:
Requires a DSL modem in the home.
Connects to the Internet via DSLAM (Digital Subscriber Line Access Multiplexer) at the telephone company’s central office.
Typical Speeds:
Download: 1–25 Mbps
Upload: Lower than download speeds
Speed depends on distance to the central office.
Twisted-Pair Cables
One of the oldest and most common transmission media.
Consists of two insulated copper wires (about 1 mm thick), twisted in a helical form (like DNA).
Reduces electromagnetic interference.
Cable Internet Access
Delivered via coaxial cable used for cable TV.
A cable modem connects to the CMTS (Cable Modem Termination System) at the provider's headend.
Infrastructure:
Part of a Hybrid Fiber-Coaxial (HFC) system:
Fiber optic runs from provider to neighborhood nodes.
Coaxial cables run from node to individual homes.
CMTS Function:
Aggregates and manages traffic from multiple homes.
Connects users to the Internet backbone.
Coaxial Cable Features:
Better shielding and noise protection
Greater bandwidth over long distances
Two types:
50-ohm – Digital transmission
75-ohm – Analog transmission
Bandwidth depends on cable quality
Uses FDM (Frequency-Division Multiplexing):
Separate channels for upload and download
Modern standards: DOCSIS 3.0 / 3.1
Support speeds from hundreds of Mbps to several Gbps
Good for browsing/media; limited for high upstream tasks (e.g., conferencing, cloud backup)
FTTH (Fiber to the Home)
Delivers internet via optical fiber directly to homes.
Key Features:
Very high speeds: 100 Mbps to 1 Gbps, up to 10 Gbps
Uses Passive Optical Network (PON):
OLT (Optical Line Terminal) – At provider
Splitter – Near neighborhood
ONT (Optical Network Terminal) – At home
ONT Role:
Installed by ISP (e.g., Jio, Airtel, BSNL)
Converts optical signals to electrical Ethernet signals
Setup Example:
- ONT connects to a D-Link router via Ethernet (WAN port)
Benefits:
Symmetrical speeds (upload = download)
Low latency and high reliability
Excellent for HD/4K streaming, gaming, video calls, backups
Advantages:
Extremely high-speed and future-proof
Stable and immune to interference
Ideal for modern applications
Limitations:
High installation cost for providers
Limited availability in rural or older areas
Dial-Up Access
Connects via standard telephone line using a modem
Uses circuit-switching (dedicated line during session)
Maximum speed: 56 kbps (very slow)
Internet and phone cannot be used simultaneously
Modem converts digital to analog signals
Example Use Cases:
Still used in rural/remote areas or as backup
Not suitable for streaming or video conferencing
High latency and very low data rates
Satellite Internet
Uses geostationary satellites to provide internet.
Best for:
Remote/rural areas with no access to cable, DSL, or fiber.
Requirements:
Dish antenna
Satellite modem
Clear sky view
Data Flow:
User → Satellite → ISP ground station → Internet
Typical Speeds:
1 Mbps to 100 Mbps
Latency ~500 ms (due to 36,000 km orbit distance)
Example Providers:
HughesNet
Viasat
Starlink (LEO satellite = lower latency)
Limitations:
Affected by weather
Not ideal for real-time applications (e.g., gaming, live video)
Physical Media
Physical media are the actual materials used to transmit data signals in a network.
They carry electromagnetic signals or optical pulses
Data travels through transmitter-receiver pairs
Types of Physical Media:
Guided Media – Uses solid physical path (e.g., cables)
Unguided Media – Uses air or space (wireless)
Guided Media
1. Twisted-Pair Copper Wire
Most common and least expensive
Used in telephone lines and Ethernet LAN
Speed: 10 Mbps to 10 Gbps (depends on cable type & distance)
UTP (Unshielded Twisted Pair) is widely used
2. Coaxial Cable
Two concentric copper conductors with insulation and shielding
Used in cable TV and internet systems
Can be a shared medium for multiple devices
3. Fiber Optic Cable
Transmits data as light pulses
Speed: Gbps to Tbps
Immune to interference
Secure and used for long-distance transmission and the Internet backbone
Unguided Media
1. Terrestrial Radio
Transmits via electromagnetic waves in the air
Used in Wi-Fi, Bluetooth, cellular networks
Offers mobility and no cabling
2. Satellite Radio
- Transmits data between ground stations and satellites
Types:
Geostationary satellites (36,000 km orbit, high delay)
LEO (Low Earth Orbit) satellites (lower delay, e.g., Starlink)
Best for:
Remote or rural regions with limited wired infrastructure