2.1.2 Internet Addressing

2.1.2     Internet Addressing

There are 32-bit number IP address known as Internet Protocol Version 4 (IPv4) and a new 128-bit number IP address known as Internet Protocol Version 6 (IPv6). An Internet Protocol Version 4 (IPv4) is used in this thesis project and will be discussed. An IP address is divided into two parts which is network part and host part. The part of a public IP address that identifies the network is internationally controlled by the Network Information Center (NIC) located in the Stanford Research Institute in California. The part that identifies the host is controlled locally at a network level. An Internet Address is four octets long. The first few bits in the network part of the address help to interpret the address. These bits indicate the class of the address. A system need to have a public address when it wants to communicate over the internet. There are five Internet Address classes which are Class A/B/C/D/E [5].

Address Class summariesshown  in Figure 2.5. A host ID that contains all 1s is meant to broadcast the packet to all hosts specified by the network. If the network ID also contains all 1s the packet is broadcast on the local network. A host ID that contains all 0s refers to the network specified by the network ID. A source may send all 0s in the source address while trying to find out the correct IP address. The machine is then identified by its MAC address.

Figure 2.5: Address Classes [5]

There are an IP address ranges reserved for private networks within organizations as shown in Table 2.1. These addresses will not be allocated by NIC as public IP addresses for the internet. When a packet goes outside the organization, the local IP address gets translated into the public IP address purchased by the organization to avoid clash problems [5].

Class A: 10.0.0.0 to 10.255.255.255 --------- 1 Class A network Class B: 172.16.0.0 to 172.31.255.255 ------ 16 contiguous Class B networks Class C: 192.168.0.0 to 192.168.255.255 --- 255 contiguous Class C networks

Table 2.1: Private addressing

Details of reserved IP address and available IP address shown in Table 2.2.

Class	Address or Range	Status
A	0.0.0.0 1.0.0.0 through 126.0.0.0 127.0.0.0	Reserved Available Reserved
B	128.0.0.0 128.1.0.0 through 191.254.0.0 191.255.0.0	Reserved Available Reserved
C	192.0.0.0 192.0.1.0 through 223.255.254 223.255.255.0	Reserved Available Reserved
D	224.0.0.0 through 239.255.255.255	Multicast group address
E	240.0.0.0 through 255.255.255.254 255.255.255.255	Reserved Broadcast

Table 2.2: Reserved and available IP addresses [5]

Figure 2.6 shows the Subnet Address. Subnet Addressing is to add another hierarchical level called the subnet. The advantage of the subnet addressing is to allow each organization to have its own internet connection within the internet [6].

Figure 2.6: Subnet Address