v-bring

Transport layer This is the fourth layer of the OSI model. The data unit at this layer is known as segment. The network layer deals with source-to-destination delivery of individual packets and does not recognize any relationship between them. On the other hand, the transport layer ensures that the entries message reaches in order and handles error control and flow control at the source-to destination level. Transport layer receives data from the session layer .it divides the data into segments with each segment having its own header and passes this segment to the network layer. At the receiver side, transport layer receives packets from the network layer. It detaches headers from them and then reassemblies the segments into original message and passes that massage to the session later Responsibilities of transport layer are: ☼ Service-point addressing - there may be number of programs running at the same time on a computer. For this purpose, source-to-destination delivery should also

Network Layer This is the third layer of the OSI model. The data unit at this layer is known as packet. There is no need of the network layer if the two communication devices lie on the same network. However, when the two devices are connected on different networks, network layer is essential for providing source to destination delivery of packets. Network layer receives data from transport layer. It adds header to the passes data to the data link layer. At the receiver said, network layer receives data from data link layer. It detaches header from the data and passes data to the transport layer. Responsibilities of the network layer are: ☼Logical Addressing - the data link layer provides physical addressing which is useful for a local network. When the packet is destined for a device outside the network, we require other addressing scheme to identify source and destination network layer adds header to the data that includes the logical address (IP address) of the source and destinati

Data link layer : Data link layer is the second layer of the OSI model. It handles data transfer between network and physical layers. Data unit at the data link layer is called as frame. Data link layer receives data from network layer. It adds header and trailer to the data and passes data to the physical layer. At the receiver said, data link layer receives data from the physical layer. It detaches header and trailer from the data and passes data to the network layer. Responsibilities of the data link layer are: ☼ Framing – the physical layer delivers raw bits from the source to destination. During transmission, the value of the bits can change. It is also possible that the number of bits received by the receiver may be different from the number of bits sent by the sender. To resolve this problem, the data link layer organizes the bits into manageable data units called as frames. ☼ Physical addressing – Data links layer adds header to the frame which contains the physical address o