Transport layer

The transport layer provides the flow of data between computers, as the name suggests. The Transmission Control Protocol, TCP and the User Datagram Protocol reside in this layer. In the transport layer, the data is segmented into parts to achieve a steady flow so that the differences in connection bandwidth between the host computers does not matter in the circulation of the data through the network.

Network layer
The Network Layer helps in transporting the data between the networks. At the beginning of the segments a network header is placed, which consists of the IP addresses of the sender and the receiver terminals. This header remains constant which is just read during the process of communication. The IP or Network trailer is also present at the end of the package, which contains the checksum to validate the data that is transferred between the networks. The Network Layer is employed by the routers to handle the network addresses.



Data link Layer
The data link layer takes input bits from layer one and arranges them into data structures called frames. It uses a frame header containing the sender and receiver addresses. These values do not remain constant and change while passing through the network nodes, routers or servers.


Physical Layer
The Physical Layer consists of the electrical part of the process of communication, the binary signals or bits that are transmitted and received in the process of exchange of data during the communication. The binary signal is a combination of 1's and 0's that may be repeated.

A network topology refers to the interconnection of various nodes of a computer network. In other words, it defines the layout of the various devices that are part of the computer network.Topology is the virtual "shape" of the network, but it may not actually represent the actual physical design of the network that the various devices are connected to each other.
There are two types of network topologies: physical and logical.

A physical topology refers to the physical design of the computer network that includes the computers and other devices, their location and the various cables installed in the network.

A logical topology means the mode of flow of data in the network in contrast to its physical arrangement.

There are mainly six types of network topologies listed as under:

• bus
• star
• ring
• tree
• mesh
• hybrid