#Basic_Networking

What is a Network?

We hear about the network. A network is a system where everyone can share information and work together. Such a network can also be used for computers. When a computer is connected to more than one computer, it is called a network. Networking requires at least two computers. Computers are connected to each other by special devices to exchange information.

Types of Network

Depending on the type of network, the network can be divided into three ways:-

✳️ LAN (Local Area Network)

✳️ MAN ( Metropolitan Area Network)

✳️ WAN ( Wide Area Network)

✳️ LAN (Local Area Network):- A local area network is a network consisting of multiple computers located within the same building. Usually small or medium office or organization This type of network is used. These networks are used in switches, hubs, routers, network interfaces, etc.

 ✳️ MAN ( Metropolitan Area Network):-  A network consisting of multiple local area networks is called a metropolitan area network. Data transfer speed in megabits per second such networks is used on routers, network interfaces, switches, microwave antennas, etc.

✳️ WAN ( Wide Area Network):-  Wide area network is a network consisting of a remote LAN or man. Such networks are used for routers, switches, modems, network interfaces, etc.

Basic Networking

Networking Devices:

Devices that connect directly to a network segment are called hosts. These hosts include computers, both clients and servers, printers, scanners, and various other user devices. These devices provide users with a network connection, through which users share, create and obtain information. Host devices can exist without a network, but without the network, the capabilities of the hosts are extremely limited.

There are no standardized symbols within the networking industry for hosts, but they are usually obvious enough to detect. The symbols are similar to the actual device in a way that constantly reminds them of that device. The basic function of computers on a LAN is to provide the user with a virtually unlimited set of applications. Modern software, microelectronics, and relatively little money allow you to run word processing, presentation, spreadsheet, and database programs. They also allow you to run a web browser, giving you almost instant access to information through the World Wide Web. You can send an email, edit graphics, save information in databases, play games and communicate with other computers located anywhere in the world. The list of applications increases daily.


Until now, we have referred to layer one concepts and devices. Starting with the network interface card, the discussion moves to layer two, the data link layer, of the OSI model. In terms of appearance, a network interface card (NIC or NIC) is a small printed circuit board that is placed in the expansion slot of a bus on the motherboard or peripheral device of a computer. Also called a network adapter. On notebook computers, NICs are usually the size of a PCMCIA card. Its function is to adapt the host device to the network medium.
IAS does not have any standardized symbols. It is implied that as long as there are networking devices connected to a network medium, there is some kind of NIC or a similar device even though they generally do not appear. Whenever there is a point in topology, it means that there is a NIC or an interface (port), which acts at least as part of a NIC. The symbols for the media vary. For example, the Ethernet symbol is normally a straight line with perpendicular lines projecting from it, the token ring network symbol is a circle with the hosts connected to it, and the symbol corresponding to an FDDI is two concentric circles with devices connected. The basic functions of the media consist of transporting a flow of information, in the form of bits and bytes, through a LAN. Except in the case of wireless LANs (which use the atmosphere, or space, as the medium) and the new PAN (personal area networks, which use the human body as a means of networking), in general, the means of Networking limits network signals to one cable or fiber. Networking media are considered Layer 1 components of LANs. Computer networks can be developed with several different types of media. Each medium has its advantages and disadvantages; what constitutes an advantage for one of the means (cost of category 5) may be a disadvantage for another of the means (cost of fiber optics). Some of the advantages and disadvantages are as follows:

Cable length.
Cost.
Ease of installation.
The total number of computers in the media as indicated in the popup box.

Collision:

A collision occurs when two bits from two different computers trying to communicate are simultaneously on a shared medium. In the case of copper media, the voltages of the two binary digits are added together and cause a third voltage level. This is not allowed in the binary system, which only understands two voltage levels. The bits are "destroyed".

Some technologies, such as Ethernet, handle a certain level of collisions, managing shifts to transmit on the shared medium when communication occurs between hosts. In some cases, collisions are a normal part of a network's operation. However, too much collision can slow the network down or stop it completely. Therefore, a large part of the design of a network is concerned with how to minimize and locate collisions.

There are many ways to deal with collisions. One of these ways is to detect them and simply have a set of rules to address the problem when it occurs, as in the case of Ethernet. Another way to address the problem is to prevent collisions by allowing only one computer in a shared media environment to transmit at a time. This requires the computer to have a special bit pattern called a token to transmit, as in the case of token-ring and FDDI. In general, collisions are believed to be bad as they degrade network performance. However, a certain number of collisions is a natural function of a shared media environment (that is, a collision domain).

Repeater:

One of the disadvantages of the type of cable we mainly use (UTP CAT5) is the length of the cable. The maximum length for UTP cabling on a network is 100 meters. If it is necessary to extend the network beyond this limit, a device must be added to the network. This device is called a repeater. The term repeater has been used since the earliest days of visual communication, when a person on a hill repeated the signal they had just received from the person on the hill on the left, in order to communicate the signal to the person who was located on the hill on the right. It also comes from telegraphic, telephone, microwave, and optical communications, each of which uses repeaters to boost signals over great distances, since otherwise the signals would eventually fade away or die out. The purpose of a repeater is to regenerate and re-tune network signals at the bit level to allow bits to travel farther through the media. Repeaters are devices with a single "in" port and a single "out" port. In the OSI model, repeaters are classified as Layer 1 devices, since they act only at the bit level and do not take into account any other type of information.

The Four Repeater Rule:

The Four Repeater over Ethernet rule states that there can be no more than four repeaters or repeater hubs between two computers on the network. To ensure that a 10BASE-T network with repeaters works properly, the following condition must be met: (repeater delays + cable delays + NIC delays) x 2 <maximum round trip delay. Repeater delays for 10BASE-T are typically less than 2 microseconds per repeater. Cable delays are approximately 0.55 microseconds per 100m run. The NIC delays are around 1 microsecond per NIC, and the maximum round trip delay (the 10BASE-T bit time of 0.1 microseconds times the minimum frame size of 512 bits) is 51.2 microseconds. For a UTP length of 500m connected by 4 repeaters (hubs) and 2 NIC delays, the total delay would be well below the maximum round trip delay. Repeater latency, propagation delay, and NIC latency contribute to the 4-repeater rule. If the four repeater rule is exceeded, this can lead to a violation of the maximum delay limit.


When this delay limit is exceeded, the number of late collisions increases dramatically. A late collision occurs when a collision occurs after the first 64 bytes of the frame are transmitted. Chipsets in NICs are not required to automatically retransmit when a late collision occurs. These late collision frames add a delay called the consumption delay. With increasing consumption delay and latency, network performance deteriorates. This Ethernet rule is also known as the 5-4-3-2-1 rule. Five network sections, four repeaters or hubs, three network sections that "mix" segments (with hosts), two sections are link segments (for link purposes), and a large collision domain.


Hubs:
The purpose of a hub is to regenerate and re-time the network signals. This is done at the bit level for a large number of hosts (eg 4, 8, or even 24) using a process called concentration. You will notice that this definition is very similar to that of the repeater, which is why the hub is also called a multiport repeater. The difference is the number of cables that connect to the device. The reasons hubs are used are to create a central connection point for the cabling means and to increase network reliability. Network reliability is enhanced by allowing any cable to fail without causing an interruption to the entire network. This is the difference with the bus topology, in which if a cable fails, this causes an interruption in the entire network. Hubs are considered Layer 1 devices since they only regenerate the signal and send it via a broadcast signal to all ports (network connections).


In networking, there are different classifications of hubs. The first classification corresponds to active or passive hubs. Most modern hubs are active; They take energy from a power supply to regenerate the network signals. Some hubs are called passive devices since they simply divide the signal among multiple users, which is similar to using a "Y" cable on a CD player to use more than one set of headphones. Passive hubs do not regenerate bits, so they do not extend the length of the cable, but simply allow one or more hosts to connect to the same cable segment.

Bridge:

A bridge is a layer 2 device designed to connect two LAN segments. The purpose of a bridge is to filter traffic on a LAN, so that local traffic remains local, but allows traffic that has been routed there to be connected to other parts (segments) of the LAN. You may wonder, how can the bridge detect which is the local traffic and which is not? The answer is the same that the postal service could give when asked how it knows what local mail is. Check the local address. Each networking device has a unique MAC address on the NIC, the bridge tracks which MAC addresses are located on each side of the bridge and makes its decisions based on this list of MAC addresses.

The appearance of bridges varies greatly depending on the type of bridge. Although routers and switches have adopted many of the bridge's functions, they still play a role in many networks. To understand switching and routing, you must first understand how a bridge works.


A bridge can eliminate unnecessary traffic on a busy network by dividing the network into segments and filtering traffic based on the station address. Traffic between devices in the same segment does not cross the bridge or affect other segments. This works well as long as the traffic between segments is not too heavy. Otherwise, the bridge can become a bottleneck, and can actually slow down communication

Switch:

A switch, like a bridge, is a Layer 2 device. In fact, the switch is called a multiport bridge, just as the hub is called a multiport repeater. The difference between the hub and the switch is that the switches make decisions based on the MAC addresses and the hubs do not make any decisions. Because the switches are capable of making decisions, they make the LAN much more efficient. Switches do this by "switching" data only from the port to which the corresponding host is connected. Unlike this, the hub sends data through all ports so that all hosts must-see and process (accept or reject) all data.

Router:

The router is the first device it will work with that is located in the OSI model network layer, or layer 3. By working in layer 3, this allows the router to make decisions based on groups of network addresses (classes) unlike individual MAC addresses, which is what is done at Layer 2. Routers can also connect different Layer 2 technologies such as Ethernet, Token-ring, and FDDI. However, given their ability to route packets based on Layer 3 information, routers have become the Internet backbone, running the IP protocol.


The purpose of a router is to examine incoming packets (Layer 3 data), choose the best route for them through the network, and then switch them to the appropriate outgoing port. Routers are the most important traffic regulation devices in large networks. They allow practically any type of computer to communicate with another computer anywhere in the world. Although they perform these basic functions, routers can also perform many of the other tasks that are described in the following chapters.