Network Addressing & IP Addressing/IP Classes

Introduction

• All entities in a data communications network must be uniquely identified to allow data to be directed to the intended recipient. This process is known as “addressing” and the identifier allocated to a node is known as its address.
• Each node/device is usually allocated at least one address.

Definition

• Network addressing a way to put unique value as addresses to the devices used in a computer network. Thus, it identifies networking devices separately/individually or as members of a group in a network uniquely.

Characteristics

• The network addresses are normally quoted in a numeric format (either in hexadecimal, decimal, or dotted decimal form), which is easily encoded into binary for transmission across the network.
• An address is a data structure, understood by the network, used to specify the destination of a connection/ message/ packet/ process/ device/service.

Types of Network Addressing

[A] OSI Layer Addresses

• Network Addressing is performed on various layers of the OSI model. Thus, schemes used for addressing vary on the basis of the protocol used and the OSI layer. On this basis, internetwork addresses can be categorised into three types –

(a) Data Link Layer/Physical/Hardware Addresses
(b) Media Access Control (MAC)/Subnetwork addresses
(c) Network Layer/Logical/Virtual Addresses

(a) Data Link Layer Addresses

• • Data-link layer addresses sometimes also called physical or hardware addresses, that uniquely identify each physical network connection of a network device.
  • Usually data-link addresses have a pre-established and fixed relationship to a specific device.
  • End systems generally have only one physical network connection and thus, have only one data-link address.
  • Routers and other internetworking devices typically have multiple physical network connections and therefore, have multiple data-link addresses.

(b) Media Access Control (MAC) Addresses

• • Media Access Control (MAC) addresses are used to identify network entities in LANs that implement the IEEE MAC addresses of the data link layer.
  • These addresses are 48 bits(8 btyes) in length and are expressed as 12 hexadecimal digits.
  • MAC addresses are unique for each LAN interface.
  • These addresses consist of a subset of data link layer addresses. 

(c) Network Layer Addresses

• • Network addresses are sometimes called virtual or logical addresses.
  • These addresses are used to identify an entity at the network layer of the OSI model.
  • Network layer addresses are usually hierarchical addresses.

[B] Hierarchical and Flat Network Addresses

Usually Internetwork addresses may fall into two major categories

(a) Hierarchical address

• Hierarchical addresses are combination of number of subgroups and each subgroup is successively narrowing an address until it points to a ultimate final device in the network.
• When the networks use a hierarchical address structure, the network may use this address to perform the routing operation. 
• A typical example of a hierarchical addressing system is the telephone numbering scheme(+91-9334102034) in which many subgroups of number is assigned successively and each subgroup identifies the specific entity such as name of country, name of state, name of district, location/area of user or subscriber etc.

(b) Flat address

• Many networks use a flat addressing scheme in which certain numbers are organized as an index mainly, such as our roll no., that provides no indication of the location of a computer in the network. Here, the number itself says nothing about the individual.
• Examples – the MAC hardware address.
• This type of address is easily administered and assumes no specific network topology.
• Flat networks are designed to reduce the number of routers and switches on a computer network by connecting the devices to a single switch instead of separate switches.
• Flat networks are typically used in homes or small businesses where network requirements are low.
• They have poor security.

[C]Static & Dynamic IP(Network) Addresses

• To display Static & Dynamic IP of a device = Type “ipconfig /all” at DOS prompt.
• A networking device that possess an IP address which can be assigned in either of these two ways/forms: –

(i) Static IP Address 

• This address is assigned by a network administrator according to a predefined internetwork plan.
• A static address does not change/remains constant until the network administrator changes it manually.
• Typically, static IP addresses are best for businesses, which host their own websites and internet services. 

(ii) Dynamic IP Address

• This address is assigned automatically to the device when they are
  connected to a network
• This is done by means of some protocol-specific process.
• The same device normally possess different addresses each time when connected to the network.
• Dynamic IP addresses are usually fine for most consumers.