WK1 Introduction to Networks Flashcards
What is a Network
A network is a group of connected devices.
At home, the devices connected to your network might be your laptop, cell phones, and smart devices, like your refrigerator or air conditioner. In an office, devices like workstations, printers, and servers all connect to the network.
The devices on a network can communicate with each other over network cables, or wireless connections. Networks in your home and office can communicate with networks in other locations, and the devices on them.
Device communication on a Network
Devices need to find each other on a network to establish communications. These devices will use unique addresses, or identifiers, to locate each other. The addresses will ensure that communications happens with the right device. These are called the IP and MAC addresses.
Devices can communicate on two types of networks: a local area network, also known as a LAN, and a wide area network, also known as a WAN.
LAN
A local area network, or LAN, spans a small area like an office building, a school, or a home. For example, when a personal device like your cell phone or tablet connects to the WIFI in your house, they form a LAN. The LAN then connects to the internet.
WAN
A wide area network or WAN spans a large geographical area like a city, state, or country. You can think of the internet as one big WAN.
An employee of a company in San Francisco can communicate and share resources with another employee in Dublin, Ireland over the WAN.
HUB
A hub is a network device that broadcasts information to every device on the network. Think of a hub like a radio tower that broadcasts a signal to any radio tuned to the correct frequency.
Switch
switch makes connections between specific devices on a network by sending and receiving data between them. A switch is more intelligent than a hub. It only passes data to the intended destination. This makes switches more secure than hubs, and enables them to control the flow of traffic and improve network performance.
Router
A router is a network device that connects multiple networks together.
For example, if a computer in one network wants to send information to a tablet on another network, then the information will be transferred as follows: First, the information travels from the computer to the router. Then, the router reads the destination address, and forwards the data to the intended network’s router. Finally, the receiving router directs that information to the tablet.
Modems
A modem is a device that connects your router to the internet, and brings internet access to the LAN.
For example, if a computer from one network wants to send information to a device on a network in a different geographic location, it would be transferred as follows: The computer would send information to the router, and the router would then transfer the information through the modem to the internet. The intended recipient’s modem receives the information, and transfers it to the router. Finally, the recipient’s router forwards that information to the destination device.
Virtualisation tools
Virtualization tools are pieces of software that perform network operations. Virtualization tools carry out operations that would normally be completed by a hub, switch, router, or modem, and they are offered by Cloud service providers. These tools provide opportunities for cost savings and scalability.
Network Devices
Network devices are the devices that maintain information and services for users of a network. These devices connect over wired and wireless connections. After establishing a connection to the network, the devices send data packets. The data packets provide information about the source and the destination of the data.
Devices and desktop computers
Most internet users are familiar with everyday devices, such as personal computers, laptops, mobile phones, and tablets. Each device and desktop computer has a unique MAC address and IP address, which identify it on the network, and a network interface that sends and receives data packets. These devices can connect to the network via a hard wire or a wireless connection.
Firewall
A firewall is a network security device that monitors traffic to or from your network. Firewalls can also restrict specific incoming and outgoing network traffic. The organization configures the security rules. Firewalls often reside between the secured and controlled internal network and the untrusted network resources outside the organization, such as the internet.
Servers
Servers provide a service for other devices on the network. The devices that connect to a server are called clients. Clients send requests to the server for information and services. The server performs the requests for the clients. Common examples include DNS servers that perform domain name lookups for internet sites, file servers that store and retrieve files from a database, and corporate mail servers that organize mail for a company.
Hubs and Switches
Hubs and switches both direct traffic on a local network. A hub is a device that provides a common point of connection for all devices directly connected to it. Hubs additionally repeat all information out to all ports. From a security perspective, this makes hubs vulnerable to eavesdropping. For this reason, hubs are not used as often on modern networks; most organizations use switches instead.
A switch forwards packets between devices directly connected to it. It maintains a MAC address table that matches MAC addresses of devices on the network to port numbers on the switch and forwards incoming data packets according to the destination MAC address.
Routers (more info)
Routers sit between networks and direct traffic, based on the IP address of the destination network. The IP address of the destination network is contained in the IP header. The router reads the header information and forwards the packet to the next router on the path to the destination. This continues until the packet reaches the destination network. Routers can also include a firewall feature that allows or blocks incoming traffic based on information in the transmission. This stops malicious traffic from entering the private network and damaging the local area network.
