Explain OSI and TCP/IP with a neat diagram
OSI Reference Model:
The OSI model has seven layers:
The Physical Layer
- The physical layer is concerned with transmitting raw bits over a communication channel. The design issues have to do with making sure that when one side sends a 1 bit it is received by the other side as a 1 bit, not as a 0 bit.
The Data Link Layer
- The main task of the data link layer is to transform a raw transmission facility into a line that appears
free of undetected transmission errors. The sender breaks up the input data into data frame and transmit the frames sequentially. - If the service is reliable, the receiver confirms correct receipt of each frame by sending back an
acknowledgement frame. The medium access control sublayer deals how to control access to the shared channel.
The Network Layer
- The network layer controls the operation of the subnet. A key design issue is determining how packets are routed from source to destination. Routes can be based on static tables that are ‘‘wired into’’ the network and rarely changed, or more often they can be updated automatically to avoid failed components.
- Handling congestion is also the responsibility of the network layer.
The Transport Layer
- The basic function of the transport layer is to accept data from above it, split it up into smaller units if need be, pass these to the network layer, and ensure that the pieces all arrive correctly at the other end.
- The transport layer also determines what type of service to provide to the session layer, and, ultimately, to the users of the network. The transport layer is a true end-to-end layer; it carries data all the way from the source to the destination.
The Session Layer
- The session layer allows users on different machines to establish sessions between them. Sessions offer various services, including dialog control , token management (preventing two parties from attempting the same critical operation simultaneously), and synchronization.
The Presentation Layer
- The presentation layer is concerned with the syntax and semantics of the information transmitted.
- Thepresentation layer manages these abstract data structures and allows higher-level data structures (e.g., banking records) to be defined and exchanged.
The Application Layer
- The application layer contains a variety of protocols that are commonly needed by users. One widely used application protocol is HTTP (HyperText Transfer Protocol)
TCP/IP
Link Layer
- The link layer describes what links such as serial lines and classic Ethernet must do to meet the needs of this connectionless internet layer.
Internet Layer
- The internet layer is the linchpin that holds the whole architecture together.
The Transport Layer
- The layer above the internet layer in the TCP/IP model is now usually called the transport layer. Two end to- end transport protocols have been defined here. The first one, TCP (Transmission Control Protocol), is a reliable connection-oriented protocol that allows a byte stream originating on one machine to be delivered without error on any other machine in the internet.
- The second protocol in this layer, UDP (User Datagram Protocol), is an unreliable, connectionless
protocol for applications that do not want TCP’s sequencing or flow control and wish to provide their own.
The Application Layer
- On top of the transport layer is the application layer. It contains all the higher- level protocols.