IPv4 (Internet Protocol version 4), in former times simply IP, is the fourth version of the Internet Protocols (IP). It was the first version of the Internet Protocols, which was world-wide spread and used and forms an important technical basis of the Internets. One defined in RFC 791 in the year 1981 by Jon Postel.

Address format

IPv4 uses 32-Bit-Adressen, therefore maximally 4.294.967.296 clear addresses are possible. IPv4-Adressen are written usually decimally in 4 blocks: for example 207.142.131.235. For each block 8-bits are summarized; thus a range of values from 0 to 255 results for each block. During the advancement IPv6 128-Bit-Adressen are used. It is not yet very much common however today (2006).

A IP address is divided into a network part and a host (address) part. Computers are in the same IP net, if the network part of their address is equal actual that a condition that these computers can communicate directly with one another. In the same net no host address may be doubly assigned.

Needed for communication between different nets rout. The responsible administrator for each participating equipment assigns the address part differently. In nets with many participants the assignment of the address part is often transferred by a DHCP server in such a way specified. The network address assigns the owner or planner of the network. In the Internet the IANA is responsible for the assignment of the network addresses.

A typical network separates the 32-Bit into a 24-Bit network and 8-bits an address part (in former times class C addresses). The exact allocation between power pack and address part is indicated in form of the Subnetmask (e.g. 255.255.255.0). An alternative notation is e.g. 192.68.0.0 /16; it means the "“16"” that the left 16 bits are equal to 1.

Net classes

In former times there were firmly prescribed organizations for network classes with a firm length. This organization proved however as too inflexible, so that one changed over since 1993 bit-variable to accomplish it in the Classless inter+ Domain Routing procedure. Nowadays one cannot speak strictly speaking no more of class A/B/C networks, however it remained received generally linguistic usage and many networkable operating systems to determine the standard net mask on the basis the old classification.

The maximum number of too assigned host addresses in a net is

2Anzahl bit of the host address - 2

Two host addresses are always omitted - the first address (for example 192.168.0.0) designates the net, which is last address (for example 192.168.0.255) for the Broadcast reserved. (All participants are addressed.)

More to it: Net class.

Special network addresses

Some classes of network addresses are reserved for special purposes. RFC 3330

Local one/private network addresses

IP addresses for local of networks become detailed in the article Private_IP-Adressebehandelt

Examples

Example: (/24 (in former times class C net))

Example: (Classless)

Package length

A IP package consists of a header and the actual data. The data division contains usually further minutes, usually TCP, a UDP or an ICMP. The maximum length of the data amounts to 65515 bytes (216-1-minimale header length). Normally the transmitter limits the package length to that of the underlying medium with Ethernet amounts to the MTU in such a way specified (maximum transfer unit) 1518 bytes, whereby 18 bytes are occupied by Ethernet themselves. For IP (header and data) only 1500 bytes are thus available. Therefore the length of IP packages is often determined at 1500 bytes.

Other networks can limit the package length further. In this case IP offers the option to fragment IP packages. Each package receives an identification (the fragment ID) from the transmitter. Rout can a long package divide, because the goal network does not transfer packages of this length. The receiver can identify and again join the fragments on the basis the identification and the transmitter address.

Articles in category "IPv4"

We found here 28 articles.

Related Websites

We found here 3 related websites.

• INTERNET PROTOCOL V4 ADDRESS SPACE (last updated 19 January 2006 ...
  Originally, all the IPv4 address spaces was managed directly by the IANA. ... [RFC3330] IANA, "Category: Informational Special-Use IPv4 Addresses", ...


• IPv4 - Wikipedia, the free encyclopedia
  Internet Protocol version 4 is version 4 of the Internet Protocol (IP) and it ... For example, the IPv4 address for www.wikipedia.org is 207.142.131.235 in ...


• IPv4 - Wikipedia, the free encyclopedia
  For example, the IPv4 address for www.wikipedia.org is 207.142.131.235 in the ... As of 2004, predictions for the exhaustion of the IPv4 address space range ...