Introduction to Data Communication

Study Notes

Data communication involves exchanging information represented as "data" between entities, which can be human or non-human (devices).
Two primary types of data:
- Analog data: Continuous in time and amplitude (e.g., voice, temperature).
- Digital data: Represented using binary code (1s and 0s) (e.g., documents, images).
Predominantly, data communication today deals with digital data.

LAN (Local Area Network): Covers a small geographical area such as a building.
WAN (Wide Area Network): Links widely scattered locations, often using point-to-point connections, covering distances from 10 km to over 1000 km.
MAN (Metropolitan Area Network): Serves a metropolitan area, typically owned by a service provider, with diameters ranging from 10 km to 50 km.
PAN (Personal Area Network): A network for personal devices, typically within a range of a few meters.

Point-to-point: Direct link between two devices with reserved capacity.
Bus: All stations connected to a single linear medium, with transmissions received by all.
Ring: Each device connects to two others, transmitting in one direction.
Star: All devices connect to a central hub, facilitating communication through the hub.
Tree: Multiple star networks interlinked, with devices at various hierarchical levels.
Mesh: Devices interconnected with multiple point-to-point links, allowing redundancy.

Unicast: Data sent from sender to one specific destination.
Broadcast: Data sent from sender to all network nodes.
Multicast: Data sent to a selected group of destinations, with required subscription.

Circuit Switching:
- Establishes a dedicated path for the duration of the transmission, ensuring guaranteed performance.
- Phases: connection establishment, data transfer, and disconnection.
- Common in traditional telephone networks.
Packet Switching:
- Breaks data into packets containing user data and control information.
- Packets can be buffered and routed individually, allowing for dynamic and flexible networking.
- Packet delay arises from factors like transmission, propagation, processing, and queuing.

Key performance metrics include loss, delay, and throughput:
- Loss: Occurs when packets exceed buffer capacity.
- Delay: Comprises several components: processing, queuing, transmission, and propagation delays.
- Throughput: The actual data transmitted successfully over time, often affected by network congestion and latency.

Transmission delay depends on packet length and link bandwidth.
Queuing delay results from varying packet arrival rates compared to service rates, indicating network congestion levels.