Internet Protocol
The Internet Protocol (IP) transmits packets from one node on an IP network to another. This requires that both nodes have their own unique address: the IP address. There are two versions of IP: version 4 and version 6. In the past IP addresses (version 4) were managed using classes but now, especially with IP version 6, classless addressing is used more often.
Certain addresses are defined as for local use only. Such private networks cannot communicate with the rest of the Internet directly. The Network Address Translation (NAT) scheme is used to allow such networks access to the public Internet.
On Internet Protocol (IP) networks such as the Internet itself, data is sent in packets. Each packet carries the addresses of the source and the destinations. These addresses on IP networks are then of course called IP addresses. Every node (computer) on an IP network needs to have its own IP address.
As humans usually prefer to use names, applications such as Web browsers will need to translate those names (using DNS) into IP addresses before they can communicate with the host in question.
IP is a connectionless protocol, which means that there is no continuing connection between the end points that are communicating. Each packet that travels through the Internet is treated as an independent unit of data without any relation to any other unit of data. (The reason the packets do get put in the right order is because of TCP, the connection-oriented protocol that keeps track of the packet sequence in a message.) In the Open Systems Interconnection (OSI) communication model, IP is in layer 3, the Networking Layer.
These addresses can always be used in local networks that do not directly connect to the Internet. In fact they are not even supposed to connect to the Internet, and any node that receives messages from outside its own network with one of these addresses as the sender will discard such messages rightaway.
The reserved range of 127.0.0.0 is intended for use on a single node. Addresses in this range are called loopback addresses. Only applications on the same node can send packets to these addresses. This makes it possible, for example, to run a Webserver from the address 127.0.0.1 so changes to a Website can be tested from the Web designer's computer. Other people can never access that Webserver.
These reserved addresses are often used in conjunction with the Network Address Translation (NAT) scheme, sometimes also called "IP Masquerading" or "Network Masquerading". This means the private addresses are mapped to a single public IP address so the nodes with these private addresses can still access the Internet. This way no public IP address block needs to be allocated.
Comments (0)
Write comment
