Computer Networks: Topologies, Architectures, and Protocols

Network Topologies

Network topologies refer to the layout or arrangement of different elements (links, nodes, etc.) in a computer network. The main types of network topologies include:

  1. Bus Topology: All devices share a single communication line or cable. It is easy to install but can be slow and prone to collisions as network traffic increases.

  2. Ring Topology: Each device is connected to two other devices, forming a circular pathway for signals. Data travels in one direction, reducing collision risks

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Network Media, Coding, Topology, and Ethernet Standards

Media Transmission

Wired (transmission signals via electricity):

  • Balanced (2 conductors; if there is interference, the difference is used).
  • Unbalanced (the modified signal is received).

Types of Wired Media:

  • Stranded: 4 twisted pairs.
  • UTP (Unshielded Twisted Pair) (digital): Twisted pairs.
  • FTP (Foiled Twisted Pair) (digital): 4 twisted pairs with a mesh around them.
  • STP (Shielded Twisted Pair) (digital): Shielding on each pair and all pairs.
  • Coaxial (analog & digital): Central core conductor (copper)
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ZeroMQ in Node.js: Examples & Patterns

ZeroMQ in Node.js: Practical Examples

This document provides practical examples of using ZeroMQ (zeromq) in Node.js. It covers several common messaging patterns, including Publish/Subscribe, Push/Pull, Router/Dealer, and Request/Reply. Each example is presented with corrected code and explanations.

Publish/Subscribe Pattern (Pub/Sub)

This example demonstrates a publisher sending messages on different topics, and a subscriber listening to a specific topic (“Politica”).

const zmq = require('zeromq')
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Java HashMap Implementation: Code and Explanation

Java HashMap Implementation

This document provides a detailed implementation of a HashMap in Java.

public class HashMap<K, V> implements Map<K, V> {
    private int capacidad;
    private int numElem;
    private Lista<Map.Par<K, V>>[] arrayMapa;

    public HashMap(int cap) throws IllegalArgumentException {
        if (cap < 0) {
            throw new IllegalArgumentException("NUMERO NEGATIVO");
        } else {
            this.capacidad = cap;
            this.numElem 
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Understanding IP Address Spaces and Common Ports

Understanding IP Address Spaces

Private IPv4 Address Spaces

The following table lists the private IPv4 address spaces:

Address BlockDescription
127.0.0.0/8Loopback
192.168.0.0/16Private Network
10.0.0.0/8Private Network
100.64.0.0/10Shared address space[4] carrier-grade NAT.
172.16.0.0/12Private Network (172.16.0.0–172.31.255.255)

Special Use IPv4 Addresses

These addresses are reserved for specific purposes:

Address BlockDescription
224.0.0.0/4IP multicast.[10] (Former Class D network.)
240.0.0.0/4Reserved
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Communication Channels and Technologies

Communication Channels

A communication channel routes messages from sender to receiver. Channels can be guided (e.g., copper wires, optical fiber) or unguided (e.g., air, vacuum).

Types of Communication Channels

  • Dedicated Links: Establish an exclusive channel between two interlocutors.
    • Point-to-Point: One sender and one receiver.
    • Multipoint: Multiple callers at either end.
  • Shared Networks: Callers connect to a network node to contact others.
    • Dissemination (Broadcast): Transmitter sends data to multiple
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