Tcp Tutorial-5

TCP/ IP is a layered suite of protocols. All layers are equally important and with the absence of even a

single layer, data transfer would not have been possible. Each TCP/ IP layer contributes to the entire process of data transfer. An excellent example, is when you send an email. For sending mail there is a separate protocol, the SMTP protocol which belongs to the Application layer. The SMTP Application protocol like all other application layer protocols assumes that there is a reliable connection existing between the two computers. For the SMTP application protocol to do what it is designed for, i.e. to send mail, it requires the existence of all other Layers as well. The Physical Layer i.e. cables and wires is required to transport the data physically. The Transmission Control Protocol or the TCP protocol which belongs to the Transport Layer is needed to keep track of the number of packets sent and for error correction. It is this protocol that makes sure that the data reaches the other end. The TCP protocol is called by the Application Protocol to ensure error free communication between the source and desti
nation. For the TCP layer to do its work properly i.e. to ensure that the data packets reach the destination, it requires the existence of the Internet Protocol or IP. The IP protocol contains the Checksum and Source and Destination IP address.

You may wonder why do we need different protocols like TCP and IP and why not bundle them into the same Application protocol.? The TCP protocol contains commands or functions which are needed by various application protocols like FTP, SMTP and also HTTP. The TCP protocol also calls on the IP protocol, which in turn contains commands or functions which some application protocols require while others don?t. So rather than bundling the entire TCP and IP protocol set into specific application protocols, it is better to have different protocols which are called whenever required.

The Link Layer which is the Hardware or Ethernet layer is also needed for transportation of the data packets. The PPP or the Point to Point Protocol belongs to this layer. Before we go on let's get accustomed with certain TCP\IP terms. Most people get confused between datagrams and packets and think that they