Topic 9:Write a paragraph about network communications layer.

Nowadays,The data transference is very popular that can’t lack with the computer users. The data are transferred from source to destination through seven network communication layer.

The first, the physical layer en code the packets into the medium that will carry out them. This layer converts the message into bits. The data link layer recalculates the checksum ,confirms arrival ,and logs in the packets.the network layer recount incoming packet for sercurity and billing purposes .the transport layer recalcucates the checksum and reassembles the message segments. The session layer hold the parts of the message until the message is complete and send it to the next layer .the presentation layer expand and decrypts the message .the aplication layer converts the bits into readable characters ,and directs the data to the correct aplication .