ICMP Bits
In as in case that, it is carried through the mapping by means of ARP and the message are sent by means of the protocol of net. Protocol IP defines the basic unit of transmission, that is package IP. In this package the excellent information for the sending of this package until the destination are placed. A datagrama IP consists of a heading and an area of data. Heading occupies a fixed area of 20 bytes and an area of changeable size (corresponding to the field options). The number of nets establishing connection itself it the Internet from 1988 increased, causing the aggravation of the problem of availability of addresses in the Internet, especially the wastefulness of addresses in classrooms C and B. In such a way, searched alternative to increase the number of available addresses of net without affecting the functioning of the existing systems.
The best joined alternative was to flexibilizar the concept of classrooms – where the division between net and host only occurs to each 8 bits. The joined solution was to use the net identification and host in addressing IP of changeable form, being able to use any amount of multiple bits and of 8 bits in agreement did not occur previously. An additional identification, the mask, identifies in an address IP, that portion of bits is used to identify the net and that portion of bits for host. Protocol ICMP is a protocol auxiliary to the IP, that loads information of control and diagnosis, informing imperfections as TTL of package IP died, errors of spalling, intermediate roteadores congested and others. A message ICMP is encapsulated in protocol IP. Although encapsulated inside of package IP, protocol ICMP is not considered a protocol of higher level. In a station and a roteador, the constant information in the table of routes can be gotten of diverse forms.