What is Internet Protocol? Definition and basics.
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In order to send somebody information over the internet, you need the correct address – just like sending a regular letter through the mail. In this case however, it is the IP address. Just as a letter receives a stamp to ensure it arrives to the correct recipient, data packets get an IP address. The difference between an IP address and a postal address is that they do not correlate with a specific location per se: instead, they are automatically or manually assigned to networked devices during the connection set up. “Internet Protocol” plays an important role in this process.
Internet Protocol: Definition and history.
Internet Protocol (IP) is a connection free protocol that is an integral part of the Internet protocol suite (a collection of around 500 network protocols) and is responsible for the addressing and fragmentation of data packets in digital networks. Together with the transport layer TCP (Transmission Control Protocol), IP makes up the basis of the internet. To be able to send a packet from sender to addressee, the Internet Protocol creates a packet structure which summarizes the sent information. So, the protocol determines how information about the source and destination of the data is described and separates this information from the informative data in the IP header. This kind of packet format is also known as an IP-Datagram.
In 1974 the Institute of Electrical and Electronics Engineers (IEEE) published a research paper by the American computer scientists Robert Kahn and Vint Cerf, who described a protocol model for a mutual packet network connection based on the internet predecessor ARPANET. In addition to the TCP transmission control protocol, the primary component of this model was the IP protocol which (aside from a special abstraction layer) allowed for communication across different physical networks. After this, more and more research networks were consolidated on the basis of “TCP/IP” protocol combination, which in 1981 was definitively specified as a standard in the RFC 971.
IPv4 and IPv6: What is behind the different version numbers?
Today, those who are concerned with the characteristics of a particular IP address e.g., one that would make computers addressable in a local network, will no doubt encounter the two variants IPv4 and IPv6. However, despite undergoing extensive changes in the past, in no way is this the fourth or sixth generation of IP protocol. IPv4 actually is the first official version of the Internet Protocol, whilst the version number relates to the fact that the fourth version of the TCP protocol is used. IPv6 is the direct successor of IPv4 – the development of IPv5 was suspended prematurely for economic reasons.
Even though there have been no further releases since IPv4 and IPv6, the Internet Protocol has been revised since its first mention in 1974 (before this it was just a part of TCP and did not exist independently). The focus was essentially on optimizing connection set-up and addressing. For example, the bit length of host addresses were increased from 16 to 32 bits, therefore extending the address space to approximately four billion possible proxies. The visionary IPv6 has 128-bit address fields and allows for about 340 sextillion (a number with 37 zeroes) different addresses, thus meeting the long term need for Internet addresses.
How IP Protocol regulates fragmentation
Whenever a data packet needs to be send via TCP/IP, the overall size is automatically checked. If the size is above the maximum transmission unit of the respective network interface, the information becomes fragmented i.e., deconstructed into smaller data blocks. The sending host (IPv6) or an intermediate router (IPv4) takes over this task. By default, the packet is composed by the recipient, who accesses the fragmentation information stored in the IP header or in the extension header. In exceptional cases, the reassembling can also be taken over by a firewall, as long as it can be configured accordingly.
Since IPv6 generally no longer provides fragmentation and no longer allows router fragmentation, the IP packet must already have a suitable size before sending. If a router reaches IPv6 datagrams that are higher than the maximum transmission unit, the router will discard them and inform the sender of an ICMPv6 type 2 “Packet Too Big” message. The data sending application can now either create smaller, non-fragmented packets, or initiate fragmentation. Subsequently, the appropriate extension header is added to the IP packet, so that the target host can also reassemble the individual fragments after reception.