1. © McLean 20061 HIGHER COMPUTER NETWORKING What You Should Know About IP Addresses You need to know that: They are structured into four octets They are divided into four classes: ABCD They have limitations IP addresses are a key part of the TCP/IP protocol and are used to address and route packets across networks.

2. © McLean 20062 HIGHER COMPUTER NETWORKING What You Should Know About IP Addresses The structure of IP addresses (IPv4) IP addresses are divided into 4 X 8-bit numbers (known as octets) e.g. 11000000 10101000 00000000 00000001 This structure is represented as xxx.xxx.xxx.xxx where each xxx is a number from 0 – 255 Numbers 0, 127, and 255 are reserved for special purposes and the remaining 253 numbers in each octet are available to be assigned to nodes on a network 32 bits provides 4, 294, 967, 296 unique possible IP addresses

3. © McLean 20063 HIGHER COMPUTER NETWORKING What You Should Know About IP Addresses The division of IP addresses into four classes The International Corporation for Assigned Names and Numbers (ICANN) assigns three major classes of addresses: A, B, and C. Class D addresses are used for multicast messaging. Address class Address range of first octet Number of networks Number of hosts on each network A1 - 12612616, 777, 214 B128 - 19116, 38465, 534 C192 - 2232, 097, 152254 D>=224N/A

4. © McLean 20064 HIGHER COMPUTER NETWORKING What You Should Know About Classes of IP Addresses Class A Owner is assigned an address in the first octet Then assigns addresses in the remaining three Therefore nearly 2 24 addresses (16.8 million!) that can be assigned to nodes within their networks Assigned to large corporations and educational institutions E.g. Apple, IBM, Hewlett Packard An example of a Class A address is 124.xxx.xxx.xxx Range of addresses: 0.0.0.0 – 127.255.255.255

5. © McLean 20065 HIGHER COMPUTER NETWORKING What You Should Know About Classes of IP Addresses Class B Owner is assigned an address in the first two octets Then assigns addresses in the remaining two Therefore nearly 2 16 addresses (65.5 thousand!) that can be assigned to nodes within their networks Assigned to medium-sized organisations E.g. Microsoft An example of a Class B address is 129.57.xxx.xxx Range of addresses = 128.0.0.0 - 191.255.255.255

6. © McLean 20066 HIGHER COMPUTER NETWORKING What You Should Know About Classes of IP Addresses Class C Owner is assigned an address in the first three octets Then assigns addresses in the remaining one Therefore nearly 2 8 addresses (256) that can be assigned to nodes within their networks Assigned to small-sized organisations E.g. Microsoft An example of a Class B address is 198.57.104.xxx Range of addresses: 192.0.0.0 – 223.255.255.255

7. © McLean 20067 HIGHER COMPUTER NETWORKING What You Should Know About Classes of IP Addresses Class D These addresses are not used for networking Used for multicast messaging where a single message is sent to each computer in a group of computers sharing a single IP address An example of a Class D address is 239.xxx.xxx.xxx Range of addresses: 224.0.0.0 – 239.255.255.255

8. © McLean 20068 HIGHER COMPUTER NETWORKING What You Should Know About Classes of IP Addresses Limitations of IP addresses Limited to 2 32 (4, 294, 967, 296) possible addresses Due to growth of networking, particularly with recent growth of wireless, available IP addresses will run out! Solution Internet Protocol version 6 (IPv6) has been developed. IP addresses will be extended to 128 bits Therefore range will increase to 0 – 2 128 This means embedded systems such as mobile phones, ATM machines, retail pos systems can be given IP addresses as well as computers on networks!