Computer Networks Course - Class 01

Hello welcome to the Computer Networks course. 

 

To start we need to establish which concepts we need to acquire in this first class, let's go to the topics: 

1 - What is a computer network?

2 - What makes up a computer network? 

3 - What networks have to offer? 

4 - How to classify the networks? 

5 - What types of network connections? 

6 - What are the network topologies? 

7 - How is access to the media controlled? 

8 - What is the classification of the networks? 

 

Let's bring the Wikipedia concept: 

1 - Computer network or Data network, in computing and telecommunications, is a set of two or more electronic computing devices (or processor modules or network nodes) interconnected by a digital communication system (or data link), guided by a set of rules (network protocol) to share among themselves information, services, and physical and logical resources. These can be of the type: data, printers, messages (emails), among others. Connections can be established using cable media or wireless media. 

 

2 - The components of a computer network are basically: 

I - Workstations: desktops, laptops and mobile devices in general (smartphones, tablet, etc). 

II. Means of Communication: Cables, air, electricity, etc. 

III. Network infrastructure equipment: hubs, switches, routers, etc. 

 

3 - The networks can meet some needs, such as: 

I. Allow users remote access to services and applications: email, e-commerce and Internet Banking; 

II. Allow communication between users: Chat, Voice over IP, Videoconference and file exchange; 

III. Resource Sharing: Network Printer, Storage, and remote processing (eg computational grids). We will explain some later of these concepts. 

 

4 - Networks have several classifications, let's go to some of them: 

I - Peer-to-peer networks: There is no central component in the network, there is usually an application that manages communication between network nodes in a decentralized way 

II - Client-Server Networks: There are one or several clients that request a service and a server that offers the service to several clients. 

There are also types of network connections: 

Peer-to-peer: Where each machine has a connection to every other machine that is part of the network. 

Multipoint Connection: Where all machines that are part of the network connect to a means of communication, a cable or device. 

 

5 - The types of network connections are: 

Bus: Where all machines connect to a central communication medium. 

Ring: Where all machines connect to form a ring 

Star: Where all machines connect to a central device. 

Mesh: Machines connect to each other, one machine connects to all others and this is true for all machines in the network, thus forming a mesh. 

Tree: There is a hierarchy between the devices, forming, it could be said, a branch of a starting point that is distributed to all the others. 

 

6 - There is also the concept of logical and physical topology, physics is how the devices are connected, forming a bus, star or tree, and logical topology means how the network works, considering all device configurations. For example a star network with a central hub is a physical star topology but a logical bus topology because of how the hub works. 

 

 7 - Access to the means of communication must be controlled as otherwise there are collisions, which is what occurs when two or more signals are transmitted over a cable, for example, at the same time, as the physical properties of this transmission are basically identical in frequency, length of wave and others they cannot occur at the same time in the medium so there is a way to avoid transmission collisions which is CSMA/CD (Carrier Sense Multiple Access with Collision Detection) and CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). CSMA/CD is used in ethernet networks and CSMA/CA is used in 802.11 wireless networks, they are mechanisms to detect and avoid collisions in transmissions. 

 

8 - Networks can be classified by their coverage area: 

LAN - (Local area network) in a local area or department. 

MAN - (Metropolitan area network) in a city or group of cities 

WAN - (Wide area network) in a country or continent 

PAN - (Personal area network) in the body or an area involving the body 

WLAN - Wireless LAN, is a local wireless network 

WWAN - Wireless WAN, is a wireless network with wide WAN

 

 

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