Network Topologies and Communication Modes

Computer Networks Fundamentals

• The computer network is a collection of autonomous computers interconnected via a single technology. Two computers are interconnected if they can exchange information.
• Early computer networks were limited to exchanging text-based information. Current networks carry voice, video, text, and graphics, connecting various devices.
• Business applications use computer networks by having company data stored on servers, and employees access it remotely using client devices.
• In a client-server model, the client device requests information, and the server device responds.
• Home applications primarily use the Internet for connectivity to remote computers.
• Peer-to-peer networks allow computers to connect and share resources without a dedicated server. Each device can act as both a client and a server in this model.
• Mobile users utilize networks for connectivity to remote computers to access information.

Uses of Computer Networks

• Early data networks were limited to exchanging character-based information between connected computer systems.
• Modern networks carry voice, video streams, text, and graphics.
• They connect a wide variety of devices, including traditional company systems.
• Home networking has become popular. Mobile devices, and social issues are also important aspects.

Home Applications

• Internet access is used to connect home users to remote computers.
• A common model is the client server model for information access
• Peer-to-peer communication is another popular method for accessing information.

Mobile Users

• Mobile users frequently use their mobile devices for internet access.
• Wired connections are not practical in many mobile situations.

Social Issues

• Social networks allow people to share views with like-minded others, which can involve problematic issues such as copyright, cookies, and spam.

Networks

• A network is a collection of devices connected by communication links.
• Devices can be computers, printers, etc.
• Networks use distributed processing where tasks are divided among multiple computers instead of a large central machine.

The Elements of Computer Networks

• Devices, medium, rules, and messages.
• Common network devices include desktop computers, laptops, servers, switches, firewalls, routers, wireless routers, etc.

Data Flow

• Communication methods between devices can be simplex, half-duplex, or full-duplex.
• Simplex is one-way communication.
• Half-duplex is two-way communication, but not simultaneously.
• Full-duplex is two-way communication simultaneously.

Network Criteria

• Performance - measured by transit time, response time, throughput, and delay.
• Reliability - Measured by the frequency of failure, the time to recover, and the robustness against disasters.
• Security - protecting data from unauthorized access, damage, and breaches.

Categories of Networks

• Connection type—point-to-point (dedicated link) and multipoint (shared channel)
• Topology—mesh, bus, star, ring, and hybrid
• Distance—personal area networks (PANs), local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs).

OSI Model

• A layered framework to design network systems that allows them to communicate with each other irrespective of architecture.
• Protocols are required for communication
• The framework is a model that allows data communication and networking to work together to move data from one device to another.

TCP/IP Protocol Suite

• A layered protocol model for internetwork communications.
• Defines four categories of functions necessary for successful communications.
• Has the same structure of the OSI model
• Built upon hardware

Addressing

• Four addressing levels in TCP/IP protocols: physical address, logical address, port address, and application-specific address.
• Physical addresses are unique to each device on a network.
• Logical addresses are independent of the underlying physical network.
• Port addresses are used to label the different processes on a computer.