A signal is a type of electrical or electromagnetic current that transports data from one device or network to another.
It is the key component behind virtually all:
- Communication
- Computing
- Networking
- Electronic devices
There are two types of signals: analog and digital.
If you are still perplexed, please read on.
Electrons can move through the metal conductor, and the electrons carry your network data.
Read Again! Electrons carry your data.
Metals include “copper” in twisted-pair cables and coaxial cables. Electrons can flow through the conductor and network data can travel along the cable as long as the path of the conductor is complete and unbroken. It is described as continuous. When there is a break in the conductor, electrons cannot flow along the length of the cable. Because electrons carry your network data, if electrons cannot pass through the cable, neither can the network data. Electrical current is how fast the electrons are flowing in the wire.
We need to grasp one more physical concept. It is voltage. Voltage is really electrical pressure.
Voltage is the pressure that attempts to cause electrons to flow.
The electrons are feeling a push. Consider voltage to be the force that moves electrons in a circuit, and resistance to be anything that can slow them down, such as a broken wire.
We can see voltage changes over time using an oscilloscope.
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Here’s an oscilloscope readout that shows the voltage changes in a cable over time.
An oscilloscope, as we’ve seen, allows us to see voltage changes over time. The signal on a network cable is simply the voltage change over time. This means that we can see a network signal using an oscilloscope. More importantly, it enables us to determine how clear and distinct the network signal is, as well as whether there are any extraneous voltages affecting the signal and causing network problems. Extraneous voltages are referred to as noise.
In the Oscilloscope, we see the voltage change over time, not the voltage itself.
Network Interface Cards
A network interface controller(NIC) card, also known as a network adaptor or network interface card, is a circuit board that connects a computer to a network. A network interface card (NIC) is an essential component for computer network connections, facilitating better communication between data communication equipment (DCE). Most computers and some network servers include NIC cards. On a LAN, each communicating device (node) must have at least one NIC card.
The network interface card (NIC) is essentially a computer circuit card that allows your computer to connect to a network. A network interface card (NIC) converts data into an electrical signal that can be transmitted over a network. It also receives and converts signals to data.
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The Network Interface Card, or NIC, inside the computer handles encoding. It handles and decodes digital signals and is in charge of all computer messaging ins and outs.
How Does The NIC Encode The Data?
The NIC begins by taking the message that needs to be sent across the network. The message is then converted into binary numbers, a series of 0’s and 1’s. Following that, it encodes these numbers and transmits corresponding voltage signals via an attached network cable.
In the following illustration, we tried to illustrate how data is converted to a signal, sent over an Ethernet cable, and then data is constructed from the received signal in the receiving-end.
Binary is used by computers because it is easier to implement with electronics. Electricity is easier to handle when it has two states, such as on-off, high-low, or positive-negative. We’d have to represent ten states if we had to represent ten numbers at the signal level. We’d need expensive, high-sensitivity electronics to do so. We’d also have to account for state errors and spend a significant amount of time error correcting and troubleshooting. Binary is much simpler and less expensive to use.
We can convert a signal to numbers, but what if we need text? We use something called the American Standard Code for Information Interchange (ASCII). When computers exchange text messages, they use this format.
Each binary digit is referred to as a bit in computer science, and eight bits form a byte.
Each byte must be converted to an ASCII character. To do this, we convert each byte to its decimal equivalent before looking up the corresponding ASCII in an ASCII table.
So the ASCII character represented by 01100001 is the letter a.
Another major character encoding scheme is Unicode. It allows for millions of characters.
Q: Why do we need to encode and decode signals?
If we do not encode and decode signals, they arrive as raw waveforms, which are 1’s and 0’s represented by voltages. Such waveforms are useless to us. We encode and decode signals in order to carry data on the signal. Because networking is all about sending messages, encoding and decoding are critical.
If we know how a signal’s encoded, that means we can decode it. We will discuss encoding-decoding in a later tutorial.
Mac Address
Every NIC has a hardware address known as a MAC Address, which stands for Media Access Control Address. MAC addresses are associated with network adapter hardware. The company that made your computer’s NIC burned it into a ROM chip on your NIC. The MAC address is also known as a networking hardware address, the burned-in address (BIA), or the physical address. Here’s an example of an Ethernet NIC’s MAC address: 00:0a:95:9d:68:16. The MAC address is usually a string of six two-digit or character sets separated by colons.
The structure of a MAC address is important to network hardware manufacturers. The first half of the MAC address is a special code assigned to the hardware manufacturer; the second half of the address is a number used by the manufacturer to number the devices they produce.
Dell, Belkin, Nortel, and Cisco are some well-known network adapter (NIC) manufacturers. These manufacturers all include a special number sequence in the MAC address that identifies them as the manufacturer (called the Organizationally Unique Identifier or OUI). The OUI is usually near the beginning of the address.
Consider the MAC address “00-14-22-01-23-45” of a network adapter. The first three octets of the OUI for the manufacture of this router are “00-14-22”. Here are some other well-known manufacturers’ OUI.
- Dell: 00-14-22
- Nortel: 00-04-DC
- Cisco: 00-40-96
- Belkin: 00-30-BD
Larger networking equipment manufacturers generally have multiple sets of OUIs.
Routers and multilayer switches are network nodes with multiple network interfaces. They must have a unique MAC address for each NIC in the same network. Two NICs connected to different networks, on the other hand, can share the same MAC address.
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The MAC address is assigned by the Institute of Electrical and Electronics Engineers Registration Authority. There are 2^48 or 281,474,976,710,656 possible MAC addresses. The IEEE does not expect to exhaust the address space until 2100.
How Do I Find My Computer’s MAC Address?
On a Macintosh, go to “System Preferences.” In the search entry box in
the upper right, type Ethernet ID and hit “Return.” The next window you see will show your Ethernet ID, which is really just another name for your MAC address.
On a Windows machine, go to “Start > Run”. Type cmd and you will open the command line utility. Type ipconfig/all and the MAC address will appear in the output.
If you are a Unix or Linux user, open a command prompt window and enter sudo /sbin/ifconfig -a. The MAC address will show under “hwaddr” or “ether”.
IP Address
Network devices use protocols, which are a set of guidelines or rules for network conversation, to communicate effectively. These protocols address issues such as how quickly data can be transmitted and how data will be structured when transmitted. Most protocols specify a message size limit, which means that messages must be split into separate packages and labeled with information about where the message came from and where it’s going.
Internet Protocol communicates in the same way that any other language does, by following predefined rules to pass information. Using this protocol, all devices find, send, and exchange information with other connected devices. Any computer in any location can communicate with another by speaking the same language.
An IP address is a unique address for a device on the internet or a local network.
IP addresses, in essence, are the identifiers that allow information to be sent between network devices: they contain location information and make devices available for communication. The internet requires a method to distinguish between different computers, routers, and websites. IP addresses enable this and are a critical component of how the internet operates.
IP addresses are generally expressed as a string of four numbers with a dot between each number, such as 192.158.1.38. Each number in the set can have a value ranging from 0 to 255. As a result, the full IP addressing range is 0.0.0.0 to 255.255.255.255.
IP addresses are not generated at random. The Internet Assigned Numbers Authority (IANA), a division of the Internet Corporation for Assigned Names and Numbers (ICANN), generates and assigns them mathematically. ICANN is a non-profit organization founded in the United States in 1998 to help maintain the security and usability of the internet. Every time someone registers a domain name on the internet, they go through a domain name registrar, who pays a small fee to ICANN to do so.
IP addresses are typically used behind the scenes. The procedure is as follows:
1. Your device connects to the internet indirectly by first connecting to a network that is connected to the internet, which then grants your device access to the internet.
That network will most likely be your Internet Service Provider when you are at home (ISP). It will be your company network at work.
2. Your ISP assigns an IP address to your device.
3. Your internet activity is routed through the ISP and returned to you via your IP address. Because they are providing you with internet access, it is their responsibility to assign an IP address to your device.
Your IP address, however, can change. Turning your modem or router on or off, for example, can change it. You can also contact your ISP and have them change it for you.
4. When you leave the house, for example, and take your device with you, your home IP address does not accompany you. This is because you will be using another network (Wi-Fi at a hotel, airport, or coffee shop, etc.) to access the internet and will be using a different (and temporary) IP address, assigned to you by the ISP of the hotel, airport or coffee shop.
As the process implies, there are various types of IP addresses, which we will look at in the following tutorial.
