Address resolution protocol (ARP)

a communication protocol used for discovering the link layer address, such as a MAC address, associated with a given internet layer address, typically an IPv4 address. Layer 2.

In IPv6 networks, the functionality of ARP is provided by the Neighbor Discovery Protocol.


Availability is a measure of the % of time the equipment is in an operable state. It can be measured as: Uptime / Total time (Uptime + Downtime).

Availability vs Reliability

While Availability is a measure of the % of time the equipment is in an operable state, then reliability is a measure of how long the item performs its intended function.

For example a machine is down 6 minutes every hour. This translates into an availability of 90% but a reliability of less than 1 hour.

Reliable machine has high availability. But an available machine may or may not be very reliable.

Font is: ´Understanding the Difference Between Reliability and Availability <https://reliabilityweb.com/tips/article/understanding_the_difference_between_reliability_and_availability/>´_.

Data Circuit-terminating Equipment

a device that sits between the data terminal equipment (DTE) and a data transmission circuit. Usually, the DTE device is the terminal (or computer), and the DCE is a modem.

Data terminal equipment

Terminal: converts user information (characters from keyboard) into signals. Or reconverts received signals in user informations (characterss on monitor).


A self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between this source and destination computer and the transporting network (RFC 1594)


On Switching. It is where frames leave the device from a particular port.

End devices

provides an interface between the human and the network.


On Switching. It is where a frame enters the device on a port.


porte specializzate in un networking device che connettono reti individuali (di solito, nei router)

Intermediary devices

provides connectivity and ensures data flows across the network.

LAN adapter

vedi Network interface card


tempo, incluso i ritardi, necessario perché i dati viaggino da un punto della rete ad un altro

Network media

provides a channel for messages to travel from source to destination.

Network interface card

(NIC) fornisce la connessione fisica dell’end device alla rete

physical port

connettore di un network device dove viene collegato il mezzo di trasmissione


Reliability is a measure of the probability that an item will perform its intended function for a specified interval under stated conditions. There are two commonly used measures of reliability:

  • Mean Time Between Failure (MTBF), which is defined as: total time in service / number of failures

  • Failure Rate (λ), which is defined as: number of failures / total time in service.


The user interface that allows users to request specific tasks from the computer.