What is a connection?

A connection is an open communication where there are parts that attend for messages and parts that send messages. In this type of connection the communication protocol is very important to avoid the risk to exchange incomprehensible messages.

What is switch, host, network, internet and Internet?

• Host: is a peripheral device connected to the network (pcs, smartphones, printers)

• Switch: is a device that can route information

• Network: a collection of Host/Switch

• internet: a network of network

• Internet: all the existent internet interconnected.

  

Communication Protocol

It is a set of rules that a device has to follows to communicate with other devices (send/receive messages).

In the communication protocol is also defined the information format.

Very simple example:

When we talk with others people we implicitly follow a communication protocol.

• A asks: “what time is it?” to B.

  B responds: “it’s half past three” to A.

  A responds: “thanks” to B.

• A asks: “What time is it?” to B.

  B doesn’t respond to A (because A is a very suspicious man).

  10 second passed…

  A asks: “What time is it?” to B.

  B doesn’t respond to A (because A is a very suspicious man).

  A asks: “What time is it?” to C.

  C responds: “it’s half past three” to A.

Internet structure

A network is a set of nodes (Router, Host, switch, server…) linked by links. in common language we call:

• Server : a device that delivers services.
• Router : Interconnection device that connect a network to another network (your home network to Lazio’s ISP)
• Modem : is a device that “traslates” analogical input from ISP to digital output for hosts and the revers. (MOD: mudulator, DEM: demodulator).