A computer, or data network, is a digital telecommunications network that allows nodes to share resources. In computer networks, computing devices communicate with each other using connections between nodes (data line). The latter are installed on cable carriers (such as wires or optical cables) or wireless technologies (such as Wi-Fi). The basics of building computer networks are described in detail in various textbooks. Actually, sorting it out is very simple.
Computer devices that initiate, route, and terminate data are called network nodes. They may include hosts (personal computers, telephones, servers), as well as network equipment. It can be argued that two such devices are networked when one of them can exchange information with the other, regardless of whether they have a direct connection to each other. In most cases, application-specific communication protocols are layered (that is, transferred as a payload). This extensive collection of information flows requires skilled management to ensure reliable operation. This definition provides a complete understanding of what constitutes the basics of computer networks. Wisnadul, Bosova, and many other textbook authors present this information in a simple, accessible language.
Computer networks support a huge number of applications and services, such as access to the World Wide Web, digital video and audio, sharing application servers, storage, printers and fax machines, as well as the operation of e-mail and instant messaging tools. They differ in the transmission medium used to send signals, as well as in communication protocols for organizing network traffic, network size, topology, traffic control mechanism, and so on. The most famous computer network is the Internet.
The properties
Considering the basics of computer networks, you can represent them as a branch of electrical engineering, electronics, telecommunications, computer science, information technology or computer technology, since they rely on the theoretical and practical application of the relevant disciplines.
A computer network facilitates interpersonal communication by allowing users to communicate effectively and easily in a variety of ways: via email, instant messaging, online chat, phone calls, video calls and video conferencing. It also allows the use of many network and computing resources. Users can receive and use the services provided by devices on the network, such as printing a document on a shared network printer or using a shared storage device. The network allows the exchange of files, data and other types of content, giving authorized users the ability to access information stored on other connected computers.
How to present the basics of computer networks for dummies? Distributed computing uses computing resources on the network to perform tasks. This means that a computer network can also be used by hackers to deploy computer viruses or worms on connected devices or to prevent these devices from accessing the network with a denial of service attack.
Network packet
What are the basics of data transfer in computer networks? Links to connections that do not support ckets (traditional point-to-point links) simply transmit data as a bit stream. However, most of the information in computer networks is carried in packets. A network packet is a formatted unit of data (a list of bits or bytes) carried by a packet-switched network.
Such packets are sent to their destination. Upon arrival, they are reassembled into the original message. Packets consist of two types of data: control information and user data (payload). These are the basics of data transmission networks. The evolution of computer networks continues to the present, but some components remain unchanged.
The control information provides information by which the network must deliver user data (for example, source and destination network addresses, error detection codes, and sequence information). Typically, it is in the packet headers and trailers with the payload data between them.
With packets, the throughput of the transmission medium can be better distributed among users than with circuit switching. When one user does not send packets, this link can be filled with those from other users, and therefore the load can be shared with relatively little interference (provided that the link is not overloaded). Often the route that the packet must receive over the network is not immediately available. In this case, it is queued and waits until the link becomes free. These are the basics of data transfer in computer networks.
Network topology
The physical location of the network is usually less important than the topology connecting the network nodes. These are the theoretical foundations of telecommunications. Local computer networks, like global ones, require a continuous connection.
Transmission media (often referred to in the literature as physical media) used to connect devices to form a computer network include an electric cable, optical fiber, and radio waves.
The widespread family of transmission media used in local area network (LAN) technology is collectively called Ethernet. The multimedia and protocol standards that enable communication between network devices through them are defined by IEEE 802.3. Ethernet transmits data over copper and fiber optic cables. Wireless LAN standards use radio waves or infrared signals as the transmission medium. The training manual "Fundamentals of Local Area Networks" (Sergeev) describes these standards in more detail.
Wire technology
Fiber optic cables are used to transmit light from one computer or network node to another.
Coaxial cable is widely used for cable television systems, office buildings and other workplaces for local area networks. Such cables consist of copper or aluminum wire surrounded by an insulating layer (usually a flexible material with a high dielectric constant), which is externally surrounded by a conductive layer. Isolation helps minimize interference and distortion. Transfer rates range from 200 to over 500 million bits per second.
ITU-T G.hn technology uses existing home wiring (coaxial, telephone and power lines) to create a high-speed (up to 1 gigabit / s) local area network.
Twisted pair wire is the most widely used means of communication for all telecommunications. Such cables consist of copper wires that are twisted in pairs. Conventional telephone wires are made from two insulated copper wires twisted in pairs. A computer network cable (wired Ethernet, defined by IEEE 802.3) consists of 4 pairs of copper wires that can be used for both voice and data. The modern foundations of building computer networks include this very means of connection most often.
Using two wires twisted together helps reduce crosstalk and electromagnetic induction. The transmission speed is from 2 million to 10 billion bits per second. Twisted pair cable is available in two versions:
- unshielded (UTP);
- shielded (STP).
Each form has several categories of ratings designed for use in different scenarios.
Optical fiber is fiberglass. It carries light pulses that represent data. The advantages of optical fibers over metal wires are very low transmission loss and resistance to electrical noise.
Optical fibers can simultaneously carry several wavelengths of light, which significantly increases the data transfer rate (up to trillions of bits per second). They can be used for very high speed data transmission over long distances, and are also used in the structure of submarine cables for connecting continents.
Price is the main factor that distinguishes the capabilities of wired and wireless technology. The second category wins significantly.
Wireless technology
The tutorial "Fundamentals of Local Area Networks" also affects wireless technology. They can be of several types.
Terrestrial microwave communications use terrestrial transmitters and receivers resembling satellite dishes. These microwaves are in the low gigahertz range, which limits all communications to direct line of sight. Relay stations are located at a distance of approximately 48 km from each other.
Communication satellites communicate via microwave radio waves that are not deflected by the earth's atmosphere. Satellites are located in space, usually in geosynchronous orbit, 35,400 km above the equator. These Earth’s orbital systems are capable of receiving and transmitting voice, data and television signals.
Cellular and PCS communication systems use several radio technologies. They share an area covered by several geographical areas. Each of them has a transmitter with a radio relay antenna for transferring calls from one area to the next.
Wireless LANs use high frequency radio technology similar to digital cellular and low frequency. They use spread spectrum technology to provide communication between multiple devices in a limited area. The IEEE 802.11 standard defines the general appearance of an open standard wireless radio wave known as Wi-Fi.
Network nodes
The textbook for grade 11, “Fundamentals of building computer networks” (Bosova), gives a good definition of network nodes. So, in addition to any physical transmission media, there are additional base units of the system, such as network interface controllers (NICs), hubs, bridges, switches, routers, modems, and firewalls. Any specific piece of equipment will contain several blocks and perform several functions.
Network interfaces
Defining the basics of computer networks for dummies, you can not get around and a description of the required equipment. Network Interface Controller (NIC) is a computer equipment that provides the machine with the ability to access transmission media and has the ability to process low-level network information. For example, the network adapter may have a connector for receiving a cable or antenna for wireless transmission and reception, and corresponding circuits. The adapter is responsible for the traffic addressed to the network address either for itself or for the computer as a whole.
In Ethernet, each network interface controller has a unique media access control (MAC) address, usually stored in read-only memory. To avoid address conflicts between devices, their uniqueness is maintained. The Ethernet MAC address is six octets in size. The three most significant of these are reserved for identifying NIC manufacturers. This information can be found on all thematic resources, including on Habrahabr. The basics of computer networks are very easy to understand if you study their basic elements.
Repeaters and Hubs
A repeater is an electronic device that receives a network signal, cleans it of unnecessary noise and regenerates it. The signal is retransmitted at a higher power level or on the other side of the obstruction, whereby it can cover long distances without deterioration. Most Ethernet twisted pair configurations require repeaters for cables longer than 100 meters. When using fiber optics, they can be tens or even hundreds of kilometers from each other.
A multi-port repeater is known as an Ethernet hub. Such devices operate at the physical layer of the OSI model. They need a small amount of time to regenerate the signal. This can lead to propagation delay, which affects network performance. As a result, many network architectures limit the number of repeaters that can be used per line (for example, the Ethernet 5-4-3 rule, which is part of the basics of computer networks).
Bridges
A network bridge connects and filters traffic between two network segments at the data line level to form a single network. This destroys the collision domain, but supports a single broadcast domain. Network segmentation breaks up a large, congested network into an aggregation of smaller, more efficient ones. These fundamentals of building computer networks allow their better functioning.
Bridges come in three main types:
- Local, directly connecting local area networks.
- Remote that can be used to create a wide area network (WAN) between LANs.
- Wireless that can be used to connect to a local network or to connect remote devices to it.
Switches
The Basics of Computer Networking Handbook (Olifer) offers a simple definition for various network equipment.
A network switch is a device that forwards and filters OSI level datagrams (frames) between ports based on the destination MAC address in each frame. A switch differs from a hub in that it only forwards frames to the physical ports involved in the connection. It can be considered as a multiport bridge. He tries to associate physical ports with MAC addresses by examining the source addresses of the received frames. If the destination is unknown, the switch translates to all ports except the source.
Multilevel switches can be routed based on Layer 3 addressing or additional logical layers. This term is often used to refer to elements such as routers and bridges, as well as devices that can distribute traffic based on load or application content.
Routers
A router is a gateway device that forwards packets between networks, processing the information included in a packet, or a datagram. When learning the basics of computer networking, he is often referred to as a router. Routing information is often processed along with the forwarding table. The router uses its table to determine where to forward packets. The destination in it may include a “zero” interface, into which data can enter, but there is no further processing for them, that is, packets are deleted.
Modems
The basics of computer networks (Microsoft and many others) will be incomplete without mentioning some network devices.
Modems (MOdulator-DEModulator) are used to connect network nodes through a wire that is not intended for digital network traffic or for wireless communication. One or more signals are modulated by a digital source to produce an analog signal that can be adapted for transmission. Modems are commonly used for telephone lines.
Firewalls
A firewall is a network device for managing security rules and network access. As a rule, it is configured to reject access requests from unrecognized sources, while allowing actions from recognized ones. The critical role of firewalls in the fundamentals of safe operation in computer networks is growing in parallel with the steady increase in cyber attacks.
Network structure
A network topology is the layout or organizational hierarchy of the interconnected nodes of a computer network. Different network topologies can affect bandwidth, but reliability is often more important. With many technologies, such as buses, one failure can lead to a network failure. A general rule in the basics of computer networks is this: the more relationships are established, the more reliable the network.
Tire
In this case, all nodes are connected to a common medium along one carrier. This is the layout used in the original Ethernet sample called 10BASE5 and 10BASE2. This is still considered the general topology at the data link level, although modern options use point-to-point links instead.
Star
All nodes are connected to a special central node. This is a typical scheme found in the basics of a wireless-type local area network, where each client connects to a central access point.
Ring
Each node is connected to two neighbors, and they are all connected to each other. The basics of a computer network in this case are as follows. Each node can reach another in a bunch by moving to the side. The Fiber Distributed Data Interface (FDDI) uses exactly this topology.
Cells
Each node is connected to an arbitrary number of neighbors in such a way that it is possible to establish a connection from one to another, regardless of their proximity.
Tree
Nodes are arranged hierarchically. This network resembles the crown of a living tree - nodes are connected with an increase in bandwidth to the root.
Note that the physical location of nodes in a network does not necessarily reflect its topology. The basics of programming computer networks are such that in practice several patterns can be observed simultaneously.
Overlay network
An overlay network is a virtual computer network that is built on top of another. The nodes in it are connected by virtual or logical links. Each link corresponds to a path and route in the core network. The overlay network topology may differ from the underlying topology. For example, many peer-to-peer networks are overlay. They are organized as nodes of a virtual reference system that work on top of the Internet.
Overlay networks have existed since the creation of the networks, when computer systems were connected over telephone lines using modems before any data network existed.
The most striking example of an overlay network is the Internet itself. It was originally built as an overlay on the telephone network. Even today, every Internet site can interact with almost any other through a basic network of subnets with completely different topologies and technologies. Address resolution and routing are tools that allow you to display a fully connected IP overlay network to the core network.
Another example of an overlay network is a distributed hash table that displays keys to nodes in the network. In this case, the core network is an IP network, and the overlay network is a table (actually a map) indexed by keys.
These technologies have also been proposed as a way to improve Internet routing, for example, by providing quality assurance to provide better streaming media. Previous offers, such as IntServ, DiffServ, and IP Multicast, have not been widely accepted because they require modifications to all routers on the network. The overlay network does not have control over how packets are routed in the core network between two overlay nodes, but it can control, for example, the sequence of overlay nodes whose message passes before it reaches its destination.
Communication protocols
There are other elements that are part of the basics of computer networks. A communication protocol is a set of rules for exchanging information over a network. In the protocol stack, each of them uses services below it, while the lower layer controls the hardware that sends information through the media.
The use of protocol bundles is ubiquitous today on a computer network. An important example of such a stack is HTTP, which works over TCP over IP over IEEE 802.11. This stack is used between the wireless router and the home user's personal computer when the latter browses web pages.
Communication protocols have various characteristics. They can be connection oriented or prevented, they can use circuit mode or packet switching, and can use hierarchical or flat addressing.
These are the most important fundamentals of computer networks. There are many communication protocols, and some of them are described below.
IEEE 802 is the family of IEEE standards for local and metro networks. Their complete set provides a variety of networking opportunities. Protocols have a flat addressing scheme. They work mainly on levels 1 and 2 of the OSI model.
For example, MAC bridges (IEEE 802.1D) are associated with routing Ethernet packets using the Spanning Tree. IEEE 802.1Q describes VLANs, and IEEE 802.1X defines a port-based network access control protocol that forms the basis for the authentication mechanisms used in VLANs (but it also occurs in WLANs) - this is what a home user sees when he needs to enter the "wireless key".
Ethernet, sometimes simply called a local area network, is a family of protocols used in wired local area networks that are described by a number of standards called IEEE 802.3.
Wireless LAN, also commonly known as WLAN or Wi-Fi, is probably the most well-known IEEE802 protocol for home users. It is standardized by IEEE 802.11 and has many features of wired Ethernet.
Internet Protocol Suite, also called TCP / IP, is the foundation of all modern networks. It offers services without connection, and also performs actions aimed at connecting at the level of Internet Protocol (IP). In essence, the protocol suite defines the specifications for addressing, identification, and routing for IP version 4 (IPv4) and IPv6, its next generation with significantly enhanced addressing capabilities.
SONET / SDH Synchronous optical networking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized multiplexing protocols that transmit multiple digital bitstreams through an optical fiber using lasers. Initially, they were intended for transmitting messages in circuit mode from different sources, primarily for real-time support, without compression, with circuit switching, encoded in PCM format (pulse-code modulation). However, due to protocol neutrality and transport-oriented features, SONET / SDH has also become an obvious choice for transporting asynchronous transfer mode (ATM) frames.
Asynchronous Transfer Mode (ATM) is a switching technology for telecommunication networks. It uses asynchronous time division multiplexing and encodes the data into small cells of a fixed size. It differs from other protocols, such as Internet Protocol Suite or Ethernet, which use variable-size packets or frames. ATM resembles both network and packet switching. This makes it a good choice for a network that needs to handle both traditional high-performance data traffic and low-latency real-time content such as voice and video. ATM uses a connection-oriented model in which a virtual circuit must be installed between two endpoints before the actual exchange of data begins.
Varieties of networks
A network may be characterized by its physical ability or organizational purpose. Network usage, including user authorization and access rights, varies accordingly.
Nanoscale network
Nanoscale communication network (BAN) has key components implemented at the nanoscale, including message carriers, and uses physical principles that are different from macro-modern communication mechanisms. Nanoscale communication expands communication with very small sensors and actuators, such as those found in biological systems, and also tends to work in environments that would be too rigid for classical communication.
Personal network
Personal (PAN) is a computer network used for communication between a computer and various information technology devices belonging to one user. Some examples of devices used in PAN are personal computers, printers, fax machines, telephones, PDAs, scanners, and even game consoles. PAN may include wired and wireless devices. The reach of this network typically extends up to 10 meters. A wired PAN is typically constructed using USB and FireWire, while technologies such as Bluetooth and infrared typically form a wireless PAN.
The local network
Local Area Network (LAN) is a network that connects computers and devices in a limited geographical area, such as a home, school, office building, or a nearby group of buildings. Each computer or device on the network is a host. Wired LANs are most often based on Ethernet technology. Newer standards, such as ITU-T G.hn, also provide a way to create a wired LAN using existing wiring such as coaxial cables, telephone and power lines.
The fundamentals of local area networks, as opposed to global networks (WANs), include higher data rates, a limited geographic range, and no dependence on leased lines to provide connectivity. Current Ethernet or other IEEE 802.3 LAN technologies operate at data rates up to 100 Gb / s. LAN can be connected to the global network using a router.
Home zone
A home network (HAN) is a residential local area network used for communication between digital devices typically deployed at home, usually a small number of personal computers and accessories, such as printers and mobile computing devices. An important feature is the transition of Internet access. Most often, technology is implemented through a cable television provider or digital subscriber line (DSL).
Data storage network
A storage area network (SAN) is a dedicated network that provides block-level access to consolidated storage. SANs are primarily used to create storage devices, such as disk arrays, libraries, and optical music centers, available for servers so that devices appear as locally attached to the operating system. A SAN usually has its own set of storage devices that are usually not accessible through the LAN by other devices. The cost and complexity of SANs fell in the early 2000s to levels that allowed wider adoption in both the corporate and small business environments.
Backbone network
MAN is part of a computer network infrastructure that provides a way to exchange information between different LANs or subnets. It can connect a variety of networks in the same room, in different buildings or over a wide area.
For example, a large company can implement a backbone network to connect departments located in different buildings. Equipment that connects departmental networks is the main network of the network. When designing MAN, communication efficiency and overload capability should be considered. Typically, the throughput of the backbone network is greater than that of individual networks connected to it.
Global network
A WAN is a computer network that spans a large geographic area, such as a city, country, or even intercontinental distances. It uses a communications channel that combines many types of carriers, such as telephone lines, cables, and air waves. The WAN often uses transmission media provided by regular carriers, such as telephone companies. Its technologies typically operate at the bottom three layers of the OSI reference model: physical, data link, and network. It is through it that one can clearly trace the foundations of computer systems and networks.
Private network of the enterprise
Corporate is a network that an organization creates to connect its premises (for example, production sites, head and remote offices, shops) so that they can share computer resources. It may include various components that are part of the basics of computer networks. Microsoft and other developers make the hardware with this connection in mind.
Virtual private network
A virtual private network (VPN) is an overlay network in which some connections between nodes are carried by open connections or virtual circuits in some larger network (for example, the Internet), and not through physical wires. Data link layer protocols are tunneled through a large network.
One of its common uses is secure communication over the public Internet. But at the same time, the VPN should not have explicit security features, such as authentication or content encryption. For example, a VPN can be used to separate the traffic of different user communities across a core network, thereby providing the basics of computer network security.
A VPN may have the best performance or may have a specific service level agreement (SLA) between the client and the service provider. Typically, such a network has a more complex topology than point-to-point.