User talk:Alirazasaad

Welcome to Wikimedia Commons, Alirazasaad!

First steps tutorial Our first steps tour and our frequently asked questions will help you a lot after registration. They explain how to customize the interface (for example the language), how to upload files and our basic licensing policy (Wikimedia Commons only accepts free content). You don't need technical skills in order to contribute here. Be bold when contributing and assume good faith when interacting with others. This is a wiki. Getting help More information is available at the community portal. You may ask questions at the help desk, village pump or on IRC channel #wikimedia-commons (webchat). You can also contact an administrator on their talk page. If you have a specific copyright question, ask at the copyright village pump.

Goodies, tips, and tricks Put Babel boxes on your user page so others know what languages you can speak and indicate your graphic abilities. You can find the files you have uploaded in your Uploads. Please sign your name on Talk pages by typing ~~~~. To link to an image page without embedding the image, type: [[:File:Foo.jpg]], which produces: File:Foo.jpg. You may enable gadgets (custom features) for your account. There are several tools to upload files. Have you edited Wikipedia before? This guide might be useful. Made a mistake? Do you want to have a file renamed or moved? Use the move link and wait for an authorized user to rename it. Do you want to have your recently uploaded picture removed? Tag it as {{speedy|reason here}}. For more information read the deletion guidelines.

-- Wikimedia Commons Welcome (talk) 07:36, 5 August 2017 (UTC)

address in IPv4 is 32-bits in size, which limits the address space to 4294967296 (232) IP addresses. Of this number, IPv4 reserves some addresses for special purposes such as private networks (~18 million addresses) or multicast addresses (~270 million addresses).

IPv4 addresses are usually represented in dot-decimal notation, consisting of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g., 172.16.254.1. Each part represents a group of 8 bits (octet) of the address. In some cases of technical writing, IPv4 addresses may be presented in various hexadecimal, octal, or binary representations.

Subnetting In the early stages of development of the Internet Protocol,[1] network administrators interpreted an IP address in two parts: network number portion and host number portion. The highest order octet (most significant eight bits) in an address was designated as the network number and the remaining bits were called the rest field or host identifier and were used for host numbering within a network.

This early method soon proved inadequate as additional networks developed that were independent of the existing networks already designated by a network number. In 1981, the Internet addressing specification was revised with the introduction of classful network architecture.[4]

Classful network design allowed for a larger number of individual network assignments and fine-grained subnetwork design. The first three bits of the most significant octet of an IP address were defined as the class of the address. Three classes (A, B, and C) were defined for universal unicast addressing. Depending on the class derived, the network identification was based on octet boundary segments of the entire address. Each class used successively additional octets in the network identifier, thus reducing the possible number of hosts in the higher order classes (B and C). The following table gives an overview of this now obsolete system.

Historical classful network architecture Class Leading bits Size of network number bit field Size of rest bit field Number of networks Addresses per network Start address End address A 0 8 24 128 (27) 16,777,216 (224) 0.0.0.0 127.255.255.255 B 10 16 16 16,384 (214) 65,536 (216) 128.0.0.0 191.255.255.255 C 110 24 8 2,097,152 (221) 256 (28) 192.0.0.0 223.255.255.255 Classful network design served its purpose in the startup stage of the Internet, but it lacked scalability in the face of the rapid expansion of the network in the 1990s. The class system of the address space was replaced with Classless Inter-Domain Routing (CIDR) in 1993. CIDR is based on variable-length subnet masking (VLSM) to allow allocation and routing based on arbitrary-length prefixes.

Today, remnants of classful network concepts function only in a limited scope as the default configuration parameters of some network software and hardware components (e.g. netmask), and in the technical jargon used in network administrators' discussions.

Private addresses Early network design, when global end-to-end connectivity was envisioned for communications with all Internet hosts, intended that IP addresses be uniquely assigned to a particular computer or device. However, it was found that this was not always necessary as private networks developed and public address space needed to be conserved.

Computers not connected to the Internet, such as factory machines that communicate only with each other via TCP/IP, need not have globally unique IP addresses. Three non-overlapping ranges of IPv4 addresses for private networks were reserved in RFC 1918. These addresses are not routed on the Internet and thus their use need not be coordinated with an IP address registry.

Today, when needed, such private networks typically connect to the Internet through network address translation (NAT).

IANA-reserved private IPv4 network ranges Start End No. of addresses 24-bit block (/8 prefix, 1 × A) 10.0.0.0 10.255.255.255 16777216 20-bit block (/12 prefix, 16 × B) 172.16.0.0 172.31.255.255 1048576 16-bit block (/16 prefix, 256 × C) 192.168.0.0 192.168.255.255 65536 Any user may use any of the reserved blocks. Typically, a network administrator will divide a block into subnets; for example, many home routers automatically use a default address range of 192.168.0.0 through 192.168.0.255 (192.168.0.0/24).

IPv6 addresses Main article: IPv6 address — Preceding unsigned comment was added by 45.116.232.55 (talk) 07:38, 5 August 2017 (UTC)