The following lines were added (+) and removed (-):
Before CIDR IP networking was classful. In 1981 three different sizes of networks were defined. Basically, due to an IP address shortage, the classful system was eventually replaced by a new system that is known as C.I.D.R. (Classless Inter-Domain Routing).Before CIDR nearly all IP networking was considered classful. In 1981 three different sizes of networks were defined. Basically, due to an IP address shortage, the classful system was eventually replaced by a new system that is known as C.I.D.R. (Classless Inter-Domain Routing). When the IP system was created the designers recognized three classes of networks and thus declaired it a classful system. It was not necessary to send the subnet mask along with the IP address. The routing protocol considered the first octet, determining the class and assuming the mask. This allowed for 4,294,967,296 possible IP addresses divided into five classes. The modern classless system makes no such assumptions about the subnet mask. With classless routing the additional information, including the subnet mask, is passed along with the IP address. .