# Introduction to Information Technology/Networking
## Introduction

Networking is a form of telecommunication between computers where they exchange data with a data link. One computer-network everyone is familiar with is the internet. Computer nodes or hosts can access, create, delete and alter data that is on this network. If a device can transmit information to another device, then they are considered to be networking. Networking utilizes devices such as switches, modems, routers, gateways, etc.

## Network Topology

Network Topology is a structural network layout that is either physical or logical and arranged by a pattern of connected computers, devices, nodes, and other links of a network. It has different structures of a network topology that shows how a network is created and connected a link (in different methods) to a device. Such network topology structures are bus, ring, mesh, fully connected (or complete), star, and hierarchical (tree). Computers MUST connect to a network of any topology because of information sharing and communication. Without a network, users are unable to share files, send emails, print files, creating and sharing database, etc. An example of this is a Local Area Network (LAN). Any node in the LAN has one or more links to other devices within the network, mapping these links can result in a geometric shape.

### Classification

Network topology has eight classifications: Bus, Ring, Mesh, Star, Point-to-Point, Hybrid, Tree, and Daisy Chain.

#### Bus

Each node in this topology connects to one single cable. This cable is essentially the spine of the network. Data is sent through either side of the cable and into the machines, where machines either ignore the data or accept it. This is considered inexpensive due to there being only one cable, but this can make it extremely detrimental to the company if it were to fail as it is the only wire connecting the different computing devices.

#### Ring

A ring topology is just a bus topology within a closed loop. The difference being that it goes through one side of the loop and into each node until a machine accepts the data. The nodes keep the strength of the signal in order to maintain connection. If one of the nodes were to fail it would disconnect itself from the other nodes in either direction.

#### Mesh

A mesh network has each machine distribute data among the network. Data bounces between each node to get to the machine where it needs to be. There are 2 types of Mesh topology.
Fully Connected has each machine connect to all the machines in the network. This is usually only practical for a small number of machines as the upkeep for such a network grows as the number of nodes grows. If one node were to fail, the network would be fine as there are other nodes the data could jump to in order to get to the right machine.
Partially Connected has the machines connect only to either one or two other machines. This is usually used to reduce the necessity in having all the connections a fully connected mesh network has.

### Star

This is one of the most popular network topologies. A star network consists of a central component such as a hub, switch or computer, that connects to all systems and transmits messages. These systems, also known as nodes, receive the messages or data and act as a client, whereas the central component acts as a server. One of the biggest advantages to this topology is that if a cable breaks or a computer on the network fails, the rest of the network will continue to work. Other advantages include easy installation, easy detection of errors and the ease to share. The disadvantages include expense and central component failures. Because this topology requires a lot of cabling, it is more expensive. If the central component stops working, the entire network and anything connected to it, will also stop working.
a point-to-point connection refers to a communications connection between two communication endpoints or nodes. An example is a telephone call, in which one telephone is connected with one other, and what is said by one caller can only be heard by the other. This is contrasted with a point-to-multipoint or broadcast connection, in which many nodes can receive information transmitted by one node. Other examples of point-to-point communications links are leased lines, microwave radio relay and two-way radio.

### Daisy Chain

Classified as one of the easiest "Star Based Networks" to add computers to a network. It works like the game telephone, if a message or a desired prompt is for a specific computer, it jumps down the line of the assigned computers until it reaches the one the message was intended for.

## Networking Hardware
### Network Interface Card (NIC)

The Network Interface Card, or NIC is the primary component of a computer responsible for accessing transmission data. The NIC is responsible for connecting a PC to both the internet, and the local network. To avoid conflicts inside of a local network, every PC is assigned a Media Access Control, or MAC, address. MAC addresses are usually stored within the NIC's permanent memory. To maintain the uniqueness of MAC addresses, the Institute of Electrical and Electronic Engineers(IEEE) maintains and administers addresses, ensuring no two addresses are the same.

### Wired Technologies

There are several wired technologies used to connect to a local area networks. Coaxial cables contain copper or aluminum wire surrounded by two insulating layers which are used for cable systems, office buildings, and other work sites. Coaxial cables transmission speed is between 200 million to 500 million bits per second. Twisted pair wire is common for all telecommunication. These cablings are twisted into pairs. Ordinary telephone wires consist of two pairs while wired Ethernet consist of four pairs. These cables have a transmission range from 2 million to 10 billion bits per second. An optical fiber carries high rates of data that can be up to trillions bits per second.

### Wireless Technologies

A wireless network is any type of computer network that connects to network nodes without using wires. It’s popular for its easier and faster way to link devices. For example, in a traditional workplace, using wireless devices eliminates the possibility of having the wrong things unplugged. The base of a wireless network is the access point. The access point sends out signals using radio frequencies that computers can detect and join. All wireless devices also have a LAN adapter built in that sends out and receives data through the radio signals sent by the access point.

### Network switch

A network switch is a multi-port device that connects multiple computers together to create a network. It can be used for sharing data between computers and can also act as a network bridge. The switch filters out network packets from each connected device and forwards them the their destination on the network, unlike a less advanced network hub, a network switch only forwards the data to one or more devices that specifically need the data rather than broadcasting the data to all of its ports. Other names for a network switch are switching hub, bridging hub, or Mac Bridge.

### Ethernet Hub

A Ethernet Hub (multi-port repeater) is a small rectangular electronic network hardware device that connects many computers and other network devices to form a single central switching point. Once connected through the hub, all computers and network devices communicate with each other. The number of ports that an Ethernet hub varies from four and five ports to eight and sixteen ports. Original Ethernet hubs only offered 10 Mbps speeds, newer hubs now offer 100 Mbps support which usually offer both 10 Mbps and 100 Mbps capabilities.

### Modems

The modem's purpose is to connect network points that are not specifically meant for network traffic by wire or wireless. They are mostly designed for telephone lines by a Digital Subscriber Line.

### Firewall

The computing term "Firewall" came to existence during the 1980's. This was around the time when the internet emerged as a new globally used technology. A Firewall is a hardware or software network device that is responsible for controlling network access and security. Firewalls track all incoming and outgoing traffic and block or allow traffic based on preset perimeters. With the increase prevalence of cyber attacks, firewalls are essential for any network to remain secure.
There are many different types of firewalls used to fulfill different purposes. These include but are not limited to:
Network Layer or Packet Fillers
Proxies
Application Layer

### Cables

A wired network must contain some type of medium to transfer data over. The types of media can include:
* Coaxial Cable - A cable consisting of insulated copper or aluminum. This type is most common, and used for cable television and CCTV networks.
* Power line communication - This refers to the transfer of data over electrical wires.
* Ethernet cables - Also known as a twisted pair because the individual wires are twisted into pairs. This is the most common for home networks.
* Fiber Optic - This is a strand of glass fiber that carries pulses of light to transmit data. Fiber optic cables can transfer multiple steams of data on different wavelengths of light; this increases data transfer rate. These cables do not have a high data loss rate and thus are used for long distance lines, such as under sea cables.
These cable types are organized in roughly slowest transfer speed to fastest.
Ethernet cables require a repeater (a device that cleans and reproduces the data at a higher strength) about every 100 meters. Fiber optic cables on the other hand, only require a repeater after about 10-100 kilometers. This make them suited for undersea cables such as the Transatlantic cable.

### Computer Network Diagram Symbolization

A computer network diagram is an illustration portraying the nodes and connections amongst nodes in any telecommunications network. Basic symbols and pictures are used to portray common network appliances. In certain depictions you can see lines connecting CPU's and a single switch. That switch may also be connected to a printer or fax machine and a router. The clouds you see in many pictures are used to portray the external networks connections between external and internal devices, without showing the details of the outside network. In some cases representative hypothetical devices may be pictured instead of showing every existing node. For example, if a network appliance is intended to be connected through the Internet to many mobile devices, only a single mobile device may be shown.

## IP Addressing
### IP Address

An IP address is a series of numbers separated by periods that are unique to each computing device that is connected to the Internet. Internet Protocol (IP), is a set of rules that facilitate all of the actions that happen within the connected parts of the World Wide Web. An IP address allows people to send and receive data over the Internet connections so that they reach their intended destination, thus making all two-way communications possible in the modern era. IP Address can also be static or dynamic. Dynamic IP addresses are randomly assigned to a computing device each time it connects to the internet. A Static IP address is one that never changes so that people have a convenient and reliable way that remote computers can access.
The Internet protocol is within the computing network that is a set communication protocol that is used on the internet and similar computer networks. It has been known since the beginning as TCP/IP, because they were the first networking protocols. It was also known as the Department of Defense model because it was funded by DARPA. TCP/IP, specify how data should be organized. For example, how it should be addressed, transmitted, routed, and received. There are four layers that are organized to sort every protocol. The lowest is link layer, it is the communication for data that remains within a single network. Second, the internet layer connects independent networks that provide inter networking. Third, the transport layer transmits between host-to-host. Finally, the application layer provides data exchange for applications from process-to-process.

### Private IP

A private IP address is an IP address that cannot directly contact the Internet and are usually provided by routers or other network devices. Private IP addresses are usually used because they provide a completely separate set of IP addresses that still allow access on a network without taking up any of the public IP address space.

### Public IP

Public IP address are any IP that is connected to the Internet. They are usually used by web sites, DNS servers, or network gateways. A public IP address is completely unique, and can only be assigned to one unique computing device at a time.

### Class Id

The Internet is the biggest and most compound TCP/IP network to date. The biggest problem faced by the internet is making sure that no two devices end up on having the same IP address. An institution called the Internet Assigned Number Authority, was formed to help track and administer the IP addresses to the people that needed them. They decided that the way the IP addresses are handed out would be to create a class for each of the different IP addresses. They created five classes to help them distinguish on who and what the person/company may need. Class A would consist of 1-126, Class B would consist of 128-191, Class C would be 191-223, Class D would consist of 224-239, and Class E would be 240-255. The reason why you don not see the number 127 used, is because it is used for the loop back address.

### DHCP

Dynamic Host Configuration Protocol or (DHCP) is a client/server protocol that provides an Internet Protocol (IP) host with its IP address and other related configuration information such as the subnet mask and default gateway. The DHCP protocol is controlled by the DHCP server. So if you moved your computer or got a new computer the DHCP server would give you your IP address instead of configuring it manually. DHCP will also give you other IP Addresses that are on the same subnet.