DAN - Network Connections (Lesson)

Network Connections

Introduction

In this lesson, you will learn about the essential components that form the backbone of computer networks. You will learn how routers play a pivotal role in directing data traffic between different networks, ensuring that information reaches its intended destination across the vast expanse of the internet. You will then learn about switches, which are critical in managing connections and data flow within a single network, enabling devices to communicate efficiently and reliably. By examining the characteristics and functionalities of these central connection devices, you will gain a deeper insight into how networks are structured and how data is transmitted across both local and wide area networks.

What is a Network?

Let’s begin with a definition of “network.” It is defined as a group of two or more computers (or other devices with a Network Interface Card (NIC), such as phones, printers, etc.) connected to one another in a way that gives the computer users simultaneous access to the same data, resources, and applications. Most networks have more than two devices!

Think about it… People on the web don’t take turns logging into Hulu to watch their favorite show or wait their turn to get on Amazon to make purchases. Those websites are shared data and the devices that host them are networked so that any user, at any time, can have access.

What Do We Need to Make a Network? Presentation

LAN vs WAN

Local Area Network (LAN) consists of devices connected inside a home, office, building, or small geographic area for the local sharing of resources, such as files, printers, applications, etc. A LAN can be two connected computers or thousands of connected devices.

Most networks are Local Area Networks (LANs). For example, your school network, the wi-fi network at the coffee shop or restaurant, and your home network -- these are all intended to connect a finite group of devices within a limited geographic area.  

All devices in a Local Area Network (LAN) must have the same IP address numbering range! We will discuss this concept a bit later.

Wide Area Network (WAN) consists of devices connected across a wide geographic area. Usually, it is a collection of connected LANs. The Internet is the largest WAN, since it connects devices globally, and it is represented graphically as a cloud. Examples of WANs are large companies, such as Coca-Cola or Delta, with offices (LANs) all around the world that are connected together (WAN). Another example is cities that provide connectivity to all their municipal entities, like courts, schools, police, fire, etc. Each of those entities runs its own LAN and they all connect via the city WAN.

 

 

Digital Packets

Digital communications uses packet switching to break up the signal into pieces and send them on different paths.

Packet Routing-WAN Animation

Did you notice how packets are sent? The first packet in the animation goes in a straight path, but then the next few packets take an indirect route. This is because every millisecond the routers are estimating what is the fastest path to a destination and the conditions of these paths change quickly. A router along one path could go down or there could be a spike in traffic – it’s very much like cars and roads. Sometimes the superhighway is the fastest but sometimes you look at Google Maps and realize there’s an accident, so taking the local road will be faster. Routers keep in touch with each other so they can be up to date on current network traffic conditions.

Digital packets are like a set of postcards!

DAN_DigitalPostcards

The message is broken up into parts with each part written on a separate postcard. The postcards are numbered. Each postcard could take a different route to get to the receiver. They will probably arrive out of order. When the receiver gets the postcards, they use the numbers to put them in order and to figure out if all of them have been received. THEN they can read the entire message!

Here is an example:

DAN_MessageParts

Connection Devices

What hardware does it take to deliver data (digital packets)? To connect devices in a LAN, the choices are hub or switch. 

Hub sends the message to everybody, like yelling to everyone in your classroom. Hubs are considered “dumb” devices because they just move the signal along.

Hubs were the original central connection device but are now rarely used because there is no management of delivery. When a message comes into a port on a hub, it goes out every other port. This is known as a “broadcast” message. When several messages are trying to use the same port or cabling, they will collide, the message is dropped, and must be sent again. In situations with a lot of message traffic, the network can become very slow.

Packet Travel Path from PC1 to PC4-Hub Animation

The animation below demonstrates how a packet is delivered in a LAN of four computers connected by a hub.

  • PC1 sends a packet to PC4.  
  • The hub is a “dumb” device, so it just pushes copies of the packet out of all connected ports.
  • PC2 and PC3 look at the packet addressing and drop it because it is not addressed to them.
  • PC4 keeps the packet.

This is why most LANs today are connected by switches because they efficiently deliver the message only to the destination port. The switch sends the message only to the destination device in the LAN, like calling or texting one person, and directs the signal only to the correct device using the MAC address. Wireless Access Point (WAP) is just a switch without wires.

Packet Travel Path from PC1 to PC4-Switch Animation

The animation below demonstrates how a packet is delivered in a LAN of four computers connected by a switch.

  • PC1 sends a packet to PC4.
  • The switch is a “smart” device so it knows which port PC4 is on and only sends the packet out that port.

  • Only PC4 receives the packet.

Routers

The router sends the message only to the destination device in the LAN or in the WAN.

To connect devices between different LANs, you must have a router.  Only a router can make WAN connections. Remember, whenever a host joins a network, it gets an IP address.  If the host wants to send data to a host in another network, it needs a router, aka “gateway,” because the router is the door out of the network. When a packet is sent with a destination IP address that is outside of the local network, it is automatically sent to the IP address of the “default gateway,” the router responsible for our LAN. All IP address configurations on devices must have a setting for the default gateway so that there is somewhere to go for unknown addresses.

DAN_Router

Router Animation

This animation demonstrates how a packet is delivered between two Local Area Networks (LANs), from PC1 in the Accounting LAN to Laptop 3 in the Marketing LAN. PC1 has IP address 192.168.1.1 and Laptop 3 has IP address 172.16.2.35.

It is quite obvious these PCs are not in the same network, so they would not be able to communicate if connected by a switch or hub. The router has one port in the 192.168.1.x addressing and the other port in the 172.16.2.x addressing. This is how it is able to “route” packets between two LANs. If the router doesn’t have a port in the destination network, then it will send packets to the next router . . . and so on and so on. Routers DO exchange information about other routers so they can keep track of possible paths for messages.  They keep a kind of mental map of the routers around them.  That’s the Internet! Cool, huh?

Reflection and Wrap-up

In this lesson, you have learned about the fundamental components of computer networks, focusing on central connection devices like routers and switches. You now know that a network is a collection of interconnected devices that share data and resources. Routers are pivotal in directing data traffic between different networks, ensuring data reaches its intended destination across the internet. Switches manage connections within a single network, facilitating efficient communication between devices. The lesson also differentiated between Local Area Networks (LANs) and Wide Area Networks (WANs), with LANs being smaller and confined to a specific area, while WANs span broader geographic regions, connecting multiple LANs. Additionally, you explored how data is transmitted in the form of digital packets, learning how routers and switches handle these packets to maintain effective and efficient network communication.

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