Protokół TCP/IP

A host is a computer or a device connected to a computer network that is assigned an IP address.IP addressIP address. A router is a networking device that forwards data packets between various computer networks, i.e. mediates communication. Nowadays this division is a bit artificial – one computer can be both assigned a network address and enable communication, i.e. be a host and a router at the same time.

In the Internet Protocol (IP), every network interface of a host is assigned a unique address. The network addresses defined by Internet Protocol version 4 (IPv4) and version 6 (IPv6) are in common use in the Internet today. Internet users do not have to know IP addresses due to the DNS protocol, which converts the mnemonic addresses of hosts into their IP addresses.

An IPv4 address is a 32‑bit binary address represented as four 8‑bit groups called octets, usually presented in decimal notation for convenience.

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Ilustracja przedstawia przykład adresu IPv4 w wersji dziesiętnej i binarnej. Na górze napis An IPv4 address (dotted-decimal notation). Rozpatrywany adres w przykładzie to: 172.16.254.1. Liczba 172 odpowiada liczbie w systemie binarnym 10101100. Liczba 16 odpowiada liczbie w systemie binarnym 00010000. Liczba 254 odpowiada liczbie w systemie binarnym 11111110. Liczba 1 odpowiada liczbie w systemie binarnym 00000001. Każda liczba binarna zapisana w przykładzie odpowiada jednemu bajtowi, czyli ośmiu bitom: One byte = Eight bits. Wszystkie liczby (cały adres) to 32 bity, czyli 4 bajty: Thirty-two bits (4 x 8), or 4 bytes.

In IPv6, the successor of the IPv4 protocol, the address size was increased from 32 bits to 128 bits in connection with the shrinking resources of IPv4 addresses. An IPv6 address is usually represented as eight 16‑bit blocks presented in hexadecimal notation, separated by a colon.

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Ilustracja przedstawia przykład adresu IPv6. Na górze napis An IPv6 address (in hexadecimal). Rozpatrywany adres w przykładzie to: 2001:0DB8:AC10:FE01:0000:0000:0000:0000. Ten sam Ares możemy zapisać 2001:0DB8:AC10:FE01:: ponieważ zera można pominąć: Zeros can be omitted. Liczba w systemie szesnastkowym 2001 odpowiada liczbie w systemie binarnym 0010000000000001. Liczba w systemie szesnastkowym 0DB8 odpowiada liczbie w systemie binarnym 0000110110111000. Liczba w systemie szesnastkowym AC10 odpowiada liczbie w systemie binarnym 1010110000010000. Liczba w systemie szesnastkowym FE01 odpowiada liczbie w systemie binarnym 1111111000000001. Każdej liczbie w systemie szesnastkowym 0000 odpowiada liczba w systemie binarnym 0000000000000000.

Public addressespublic addressesPublic addresses are used in the public part of the Internet. Open‑access web services can be operated on computers that are assigned these addresses. Private addressesprivate addressesPrivate addresses can be used only in local networks. They only enable the access of computers to the Internet.

A subnet masksubnet masksubnet mask specifies how many bits of an IP addressIP addressIP address identify a network, and how many of them identify a computer connected to this network. If the bit in the subnet mask is represented by 1, then the corresponding bit in the IP address is the bit of the network address. The bits represented as zeroes in the subnet mask specify the corresponding bits in the IP address as part of the host address. Subnets masks are usually presented in decimal notation.

A gatewaygatewaygateway is the address of the network interface of a router which allows you to connect to the Internet.

Address classesaddress classesAddress classes

Networks have been divided into classes: A, B, C , D and E, depending on their size. Class A networks are huge networks with the large number of computers (255.0.0.0), class B networks are middle‑sized (255.255.0.0), while class C networks are the smallest (255.255.255.0). Class D and E addresses have been reserved for group and test transmissions. Nowadays this division is no longer used and addresses are assigned regardless of the class of a network.

A domaindomaindomain name (domain) is an string of characters in the Domain Name System (DNS) that enables to find such resources as web sites, servers or the recipients of electronic mail. The domain name consists of two parts: a main name and an ending. The main name is any available name that a user wants to use in order to easily localise their services. DomaindomainDomain names are usually associated with the proper nouns of companies or their products. The ending of a domain can be selected from the list of available generic and country code domains. The registration of domains is managed by domain name registrars, which oversee the general principles of the reservation of domain names and IP addresses.

A subdomainsubdomainsubdomain is a network address that is the part of a main domain. For example, the addresses pl.wikipedia.org and en.wikipedia.org are subdomains of the main domain wikipedia.org, which is the subdomainsubdomainsubdomain of the org domain.

Generic domainsgeneric domainsGeneric domains are used to specify the character of the operations of the domain’s owner.

Country code domainscountry code domainsCountry code domains specify the location of the domain’s owner, for instance for domains registered in Poland the country code domain is .pl.

A Uniform Resource Locator (URL) is the standardised format of addressing the resources on the Internet and local networks. In the case of referencing web pages the simplest address has the form:

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Ilustracja przedstawia dwa napisy protocol://www.host_address/resource_path oraz poniżej http://www.epodreczniki.pl/font/education/2. Fragmenty odpowiadające sobie w obu napisach są oznaczone tymi samymi kolorami: protocol odpowiada http, www.host_address odpowiada www.epodreczniki.pl oraz resource_path odpowiada font/education/2.

The number of IP addresses is limited, there are slightly over 4 billion IPv4 addresses. Will there be enough addresses for every user? Unfortunately no. Therefore subnetworks are created, whose addresses are composed of the so called private addressesprivate addressesprivate addresses, so that more users can share a public address.

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Ilustracja przedstawia dane dotyczące użytkowników cyfrowych na świecie. Na górze napis January 2018, Digital Around the World 2018. Poniżej Key statistical for the word's Internet, mobile and social media users. Niżej znajduje się pięć pisanych grafik. Pierwsza od lewej strony: Total Population (koło puste w środku), 7.593 billion, 55%. Druga od lewej strony: Internet Users (koło, w środku ikona kuli ziemskiej), 4.021 billion, 53%. Trzecia od lewej strony: Active Social Media Users (koło, w środku ikona koperty), 3.196 billion, 42%. Czwarta od lewej strony: Unique Mobile Users (koło, w środku ikona przedstawiająca smartfon), 5.135 billion, 68%. Piąta od lewej strony: Active Mobile Social Users (koło, w środku dwie ikony czatu - chmurki komiksowe), 2.958 billion, 39%. Na dole ilustracji napis based on: https://wearesocial.com/

Exercises

Glossary

Keywords

domaindomaindomain

IP addressIP addressIP address

private addressespublic addressesprivate addresses

public addressespublic addressespublic addresses