Computer Networks Comprehensive Revision

Important Points:

• Network: A telecommunications network that connects autonomous devices for data exchange between data devices.

• Resource Sharing: Use of the network to share hardware and software resources.

• Network Goals:

  • Communication
  • Resource Sharing
  • Centralized Database
  • Cost-efficiency
  • Reliability

Transmission Modes:

• Simplex: Data flows in only one direction.
• Half-Duplex: Data can flow in both directions but only one direction at a time.
• Full-Duplex: Data flows in both directions simultaneously.

Topology:

Mesh Topology: Every device is connected to every other device. Star Topology: Network devices are connected through a central hub. Bus Topology: Devices are connected along a central line. Ring Topology: Devices are connected in a ring.

Network Model:

OSI Model: 7-layer model:

• Physical Layer
• Data Link Layer
• Network Layer
• Transport Layer
• Session Layer
• Presentation Layer
• Application Layer

Data Link Layer:

Framing, Physical Addressing, Access Control, Flow Control, Error Control.

IP and Network Layer:

IPv4: 32-bit addressing. IPv6: 128-bit addressing. Routing: Sending IP packets on the correct path.

Transport Layer:

TCP: Connection-oriented, reliable. UDP: Connectionless, fast but unreliable.

Application Layer Services:

Email: SMTP, POP3, IMAP. Web: HTTP, HTTPS. File Transfer: FTP, TFTP.

Security and Other Protocols:

Cryptography: Encryption for data security. Cryptographic Protocols: DES, AES, RSA. Data Compression: Lossy and Lossless.

Other Topics:

Firewall: Filters security protocols. Repeater: Boosts signal. Hub: Multiport device. Bridge: Connects two networks. Router: Forwards packets. Gateway: Application layer connection.