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Network Addressing

IP addresses are broken into 4 octets (IPv4) separated by dots called dotted decimal notation. An octet is a byte consisting of 8 bits. The IPv4 addresses are in the following form:

Types of Addresses

There are two types of addresses:
  1. Logical Address: The logical address is what the IP (Internet Protocol) address, can also be called virtual address, is and it looks like this IP address can change and often does when you have a high speed Internet connection. It is in hierarchical fashion i-e a network part and a host part.
    • IP Version 4; Address: IPV4 uses 32 bits to define each address. IPV4 uses four 1 byte decimal numbers separated by dots.
    • IP Version 6; Address: IPV6 uses 128 bits to define address. IPV6 uses hexadecimal numbers that are separated with colons. It is better for mobile network. It has larger address space. 
  2. Physical Address: The physical address is just like mailing address it is real, it is also called MAC address (Media Access Control address) and looks like this 00-56-7E-4A-DD-8D i-e in a hexadecimal form. It is different for every technology e.g. Ethernet uses different physical addresses than other technologies available. The communicating applications (source/destination applications) must also be identifiable.

Internet Address

Consists of 4 bytes separated by periods. Example:
  • The R first bytes (R = 1, 2, 3) correspond to the network address;
  • The remaining H bytes (H = 3, 2, 1) are used for the host machine.
  • InterNIC Register: organization in charge of the allocation of the address ranges corresponding to networks.
Criteria considered:
→ Geographical area (country)
→ Organization, enterprise
→ Department
→ Host

Parts of an IP Address

There are two parts of an IP address: 
  • Network ID
  • Host ID
IP addresses divided into 5 classes. The various classes of networks specify additional or fewer octets to designate the network ID versus the host ID.

Class A: Class A addresses are specified to networks with large number of total hosts. Class A allows for 126 networks by using the first octet for the network ID. The first bit in this octet, is always set and fixed to zero. And next seven bits in the octet is all set to one, which then complete network ID. The 24 bits in the remaining octets represent the hosts ID, allowing 126 networks and approximately 17 million hosts per network. Class A network number values begin at 1 and end at 127.

Class B: Class B addresses are specified to medium to large sized of networks. Class B allows for 16,384 networks by using the first two octets for the network ID. The two bits in the first octet are always set and fixed to 1 0. The remaining 6 bits, together with the next octet, complete network ID. The 16 bits in the third and fourth octet represent host ID, allowing for approximately 65,000 hosts per network. Class B network number values begin at 128 and end at 191.

Class C: Class C addresses are used in small local area networks (LANs). Class C allows for approximately 2 million networks by using the first three octets for the network ID. In class C address three bits are always set and fixed to 1 1 0. And in the first three octets 21 bits complete the total network ID. The 8 bits of the last octet represent the host ID allowing for 254 hosts per one network. Class C network number values begin at 192 and end at 223.

Class D and E: Classes D and E are not allocated to hosts. Class D addresses are used for multicasting, and class E addresses are not available for general use: they are reserved for future purposes.

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