Communication in Computer Networks

Key Concepts

• Communication requires a common language.
• Computers need a common message format to communicate.
• Protocols are the agreed-upon rules for communication.
• TCP/IP is a set of protocols for network communication.

Network and Communication Basics

• Network: Two computers connected to share data.
• Communication: Sending messages through wired or wireless mediums.
• Messages are broken into data units for transmission.

TCP/IP Protocol Suite

• TCP (Transmission Control Protocol): Breaks messages into segments.
• IP (Internet Protocol): Routes segments to their destinations.
• UDP (User Datagram Protocol): Offers faster, less reliable transmission.
• TCP/IP allows communication across different computer manufacturers.
• OSI Model: Another network model, mostly for research purposes.

Layers of TCP/IP Model

1. Physical Layer

• Converts binary data into signals.
• Signals vary based on media: Electrical (Copper), Light (Optical Fiber), Radio (Air).
• Ethernet is a common protocol.

2. Data Link Layer

• Ethernet Frame: Data unit in this layer.
• Divided into:
  • MAC Sublayer: Adds header/trailer, handles media access.
    • Uses CSMA/CD for media access.
    • Handles collisions and retransmissions.
  • LLC Sublayer: Offers flow control and error control.

3. Network Layer

• Handles logical addressing and routing.
• Uses IP for addressing and routing packets.
• ARP Module: Resolves IP to MAC addresses within the same network.
• Path Determination: Uses protocols like OSPF, BGP to find best paths.

4. Transport Layer

• Supports flow control and error control.
• Uses TCP or UDP based on application needs.
• TCP: Reliable, connection-oriented with three phases.
  • UDP: Faster, suitable for applications that can handle less reliability.

TCP Features

• Error-free and ordered data transfer.
• Retransmission of lost data.
• Discarding duplicates.
• Congestion throttling.

5. Application Layer

• Interfaces with end-user applications.
• Provides protocols like HTTP, FTP, SMTP.
• DNS: Translates domain names to IP addresses.
• DHCP: Dynamically assigns IP addresses.

Conclusion

• Protocols like TCP/IP ensure successful communication across networks.
• Each layer in the model has specific roles and protocols.
• Understanding each layer helps in grasping network communication essentials.