Network Devices

IP addressing, when started a few decades ago, used the concept of classes. This architecture is called class full IP addressing. In the mid of 1990s, a new architecture, Called classless IP addressing was introduced that will eventually supersede the original architecture. However, most of the internet is still using calssfull addressing and the migration is slow. To understand the classfull IP addressing it is important to understand classless addressing.

In classfull IP addressing, the IP address is divided into five classes A,B,C,D and E. each class is occupies some part of the whole address space, see below the table mansion the class occupation of the address space (approximate).

We can see that the class A covers the half of the address space, a serious design flow. Class B cover ¼ of the whole address space, another design flow. Class C is cover the 1/8 of the address, and class D and E each cover the 1/16 of the address space.

We can find the class of an address when the address is given in binary notation or in dotted decimal notation.

Find the class in binary notation

If the address is given in binary notation, the first bits can immediately tell us the class of the address.

Find the class in dotted decimal notation

When the address is given in dotted decimal notation, then we need to look only at the first byte to determining the class of the address. Each class has a specific range of number.

Net ID and Host ID

In classfull addressing an IP in classes A,B and C is divided into net id and host id.

Note: Class D and E are not divided into net id and host id.

At the network layer, we need to uniquely identify each device on the internet to allow global communication between all devices. This is analogous to the telephone system where each telephone subscriber has a unique telephone number. If we consider the country code and the area code as part of the identifying scheme

The UDP is process to process protocol that adds only port address, check-sum error control and length information to the data from the upper layer.

The TCP provides full transport layer services to application. TCP is a reliable stream transport protocol. The term stream in this context means connection-oriented: a connection must be established between both ends of a transmission before either can transmit data.

The application layer in TCP/IP is equivalent to the combined session, presentation and application layer in the OSI model. Many protocols are defined at this layer.

The UDP is process to process protocol that adds only port address, check-sum error control and length information to the data from the upper layer.

The TCP provides full transport layer services to application. TCP is a reliable stream transport protocol. The term stream in this context means connection-oriented: a connection must be established between both ends of a transmission before either can transmit data.

The transport layer is represented in TCP/IP by two protocols, TCP and UDP. The IP is a host-to-host protocol; UDP and TCP are transport level protocols. IP can deliver a packet form one physical device to another. UDP and TCP are responsible for delivery of a message from a process to another process (running programs) 

Physical and Data link Layer

At the physical and data link layer, TCP/IP does not define any specific protocol. It support all of the standard and proprietary protocol which LAN, MAN and WAN.

Network Layer

At the network layer TCP/IP supports the internetworking protocol which contains four supported protocols: ARP, RARP, ICMP and IGMP