Computer Network
A computer network is a collection of interconnected devices that can communicate and share resources. Networks can be classified based on their size, topology, protocols, and purposes.
Types of Networks
1. PAN (Personal Area Network) :
- Small network, typically within a range of 10 meters.
- Examples: Bluetooth, USB connections.
2. LAN (Local Area Network):
- Covers a small geographic area, like a home, office, or building.
- Examples: Ethernet networks, Wi-Fi networks.
3. MAN (Metropolitan Area Network) :
- Spans a city or campus.
- Examples: City-wide Wi-Fi networks, cable TV networks.
4. WAN (Wide Area Network):
- Covers large geographic areas, such as countries or continents.
- Example: The Internet.
5. CAN (Campus Area Network):
- A network that spans multiple LANs but is smaller than a MAN.
- Typically found in university campuses or large business complexes.
6. SAN (Storage Area Network :
- Specialized network that provides access to consolidated, block-level data storage.
- Common in data centers.
Network Topologies
1. Bus Topology:
- All devices share a single communication line.
- Simple but prone to collisions.
2. Star Topology:
- All devices connect to a central hub or switch.
- Easy to manage but the central device is a single point of failure.
3. Ring Topology:
- Devices are connected in a circular format.
- Data travels in one or both directions.
- Failure in one device can affect the entire network.
4. Mesh Topology:
- Devices are interconnected.
- High redundancy and reliability.
- Expensive and complex to set up.
5. Tree Topology:
- Hybrid of star and bus topologies.
- Hierarchical structure with a root node and leaf nodes.
Network Protocols
1. TCP/IP (Transmission Control Protocol/Internet Protocol):
- Fundamental protocol suite for the Internet.
- Includes protocols like HTTP, FTP, SMTP, and more.
2. UDP (User Datagram Protocol):
- Used for low-latency and loss-tolerating connections.
- Examples: Streaming, online gaming.
3. HTTP/HTTPS (HyperText Transfer Protocol / Secure):
- Used for web communications.
- HTTPS is the secure version using SSL/TLS.
4. FTP (File Transfer Protocol):
- Used for transferring files between client and server.
5. SMTP (Simple Mail Transfer Protocol):
- Used for sending emails.
6. DNS (Domain Name System):
- Translates domain names to IP addresses.
Network Devices
1. Router:
- Directs data packets between different networks.
- Operates at the network layer.
2. Switch:
- Connects devices within the same network.
- Operates at the data link layer.
3. Hub:
- Simple device that connects multiple devices in a network.
- Broadcasts data to all ports.
4. Modem:
- Converts digital data to analog signals and vice versa.
- Used for Internet connectivity over phone lines.
5. Access Point:
- Provides wireless access to a wired network.
Network Security
1. Firewalls:
- Monitors and controls incoming and outgoing network traffic.
- Can be hardware-based or software-based.
2. Encryption:
- Ensures data privacy by converting information into a secure format.
- Common methods: SSL/TLS, AES.
3. VPN (Virtual Private Network):
- Securely connects remote users to a private network.
- Encrypts data over the Internet.
4. IDS/IPS (Intrusion Detection/Prevention System):
- Monitors network traffic for suspicious activity and potential threats.
Network Models
1. OSI Model (Open Systems Interconnection):
- Seven layers: Physical, Data Link, Network, Transport, Session, Presentation, Application.
- Standard framework for network communications.
2. TCP/IP Model:
- Four layers: Link, Internet, Transport, Application.
- Practical model used in real-world networking.
Common Networking Terms
- Bandwidth: Maximum rate of data transfer across a network.
- Latency: Time taken for data to travel from source to destination.
- Jitter: Variability in packet arrival time.
- Packet: Unit of data transmitted over a network.
- IP Address: Unique address assigned to each device on a network.
| TCP/IP | OSI |
|---|---|
| TCP refers to Transmission Control Protocol. | OSI refers to Open Systems Interconnection. |
| TCP/IP follows connectionless a horizontal approach. | OSI follows a vertical approach. |
| TCP/IP uses both the session and presentation layer in the application layer itself. | OSI uses different session and presentation layers. |
| The Transport layer in TCP/IP does not provide assurance delivery of packets. | In the OSI model, the transport layer provides assurance delivery of packets. |
| Protocols cannot be replaced easily in TCP/IP model. | While in the OSI model, Protocols are better covered and are easy to replace with the technology change. |
| TCP/IP model network layer only provides connectionless (IP) services. The transport layer (TCP) provides connections. | Connectionless and connection-oriented services are provided by the network layer in the OSI model. |