Computer Networks and Communication Fundamentals
Computer Processes and Communication
Defining Computer Processes
A computer process is a running program responsible for performing specific predefined functions.
Transmission vs. Communication
Transmission refers to the conveyance of signals to produce a telematic phenomenon. Communication, on the other hand, concerns the transport of information.
Communication Elements
- Sender: The element responsible for providing information.
- Receiver: The element that receives information from the sender.
- Channel: The medium through which information is transmitted.
Terminals and Modulation
Types of Terminals
A simple transducer is a device that transforms the nature of a signal.
The Necessity of Modulation
Modulation is essential for several reasons:
- Ease of radiation
- Noise and interference reduction
- Frequency allocation
- Technical limitations of equipment
Network Concepts
Defining LAN
A LAN (Local Area Network) is a set of hardware and software elements that interconnects devices within a private or restricted area.
Transmission Credibility
A highly credible transmission is characterized by a very low error rate.
Network Organization of Distributed Systems
- Networked: Multiple computers are connected via data networks while maintaining their individual identities.
- Distributed: The presence of multiple computers on the network is transparent to the user.
Communication Protocols and Layered Architecture
Purpose of Communication Protocols
Communication protocols regulate aspects of communication.
Layered Hierarchical Structure
Each layer interacts with the layers above and below it. It requests services from the lower layer and returns results to the upper layer.
Interfaces Between Layers
Interfaces define the standards for interconnection between layers, specifying the services and operations provided by the lower layer to the higher layer.
Layered Network Architecture Diagram
Layer N — Protocol — Layer N
Layer N-1 — Protocol — Layer N-1
Layer 1 — Protocol — Layer 1
Network Topologies
Defining Network Topology
Network topology describes the physical or logical arrangement of nodes and connections in a network.
Influence of Network Requirements
The choice of topology depends on factors like cost and desired security level.
Basic Network Topologies
- Mesh
- Bus
- Ring
- Hybrid
Advantages of Bus Topology
- Easy addition of new nodes
- Reduced cabling compared to other topologies
Functions of the Central Node in Star Topology
- Distribution
- Computing
- Control
Drawbacks of Star Topology
- High cable usage
- Network failure if the central node fails
MAU (Multiple Access Unit)
A MAU contains an inner ring. The network appears as a star but functions as a ring. If a node disconnects, the MAU bypasses it, preventing ring breakage.
Versatility of Layered Network Design
Layered design reduces complexity and allows for technological changes or innovations in specific layers without affecting the entire architecture.
Service Access Points (SAPs)
Defining SAP
A SAP is a point through which layer entities access services and exchange information. It acts as an address or entry point, typically represented by numbers.
Types of Services Offered by a Layer
- Communication Type: Connection-oriented, connectionless
- Acknowledgment Method: Confirmed (reliable), unconfirmed (unreliable)
Additional Network Concepts
Defining Communication Protocol
A communication protocol is a set of rules defining how communication occurs between participants.
Defining Open System
An open system is one or more computers forming an autonomous whole capable of processing information and interfacing with other systems according to defined rules.
Role of the Link Layer
The link layer ensures error-free communication between computers on the same network. It organizes bits into frames and passes them to the physical layer for transmission.
Framing
Framing is the technique of grouping bits into patterns for delivery to the physical layer.
Types of Network Topology
- Ring Topology: Nodes are connected in a physical ring.
- Bus Topology: Nodes are connected to a single transmission line.
- Star Topology: Nodes are connected to a central hub.