Now after covering almost every aspect of the Application Layer and the Application Layer protocols, we have now here to start our discussion on the 2nd layer of the Internet stack , The Transport Layer.
Before starting with our discussion on Transport Layer, I want to give you a live scenario, that will make you clear with the working of Transport Layer and the other layers of the Internet stack.
In this example we have processes and the layers. Let me explain.
Application Layer messages = envelopes
Network Layer protocol = Postal Service
- Here you can see, that according to children, James and Steve are the mail services, but in real they are just a part of the delivery process.
Suppose James and Steve went on a holiday for 10 days. Then as their susbstitute, Angelina comes at place of James and Ashley comes at place of Steve. But now for the two bungalows, unfortunately Angelina and Ashley are not able of providing services as James and Steve. Angelina and Ashley often drops letters, lose them, which are often eaten by the dogs. Thus in the same way , services provided by the Transport Layer depends on type of protocol you use in your network.
- In this scenario, for example if the postal service cannot guarantee the maximum time taken in the delivery of the envelopes, thus there is no way that James and Steve can guarantee the maximum delays in the delivery of mails between the children. In the same way, the services provided by the Transport Layer are often subjected to the services provide by the underlying network layer. If the network layer cannot guarantee the delay in delivery of messages, then surely transport layer can never.
But still, a Transport Layer protocol guarantees certain services that are not guaranteed by the underlying Network Layer.
Overview of Transport Layer Protocol:
Logical communication means that, from an Application perspective, it is like the hosts are directly connected to each other, but in reality , the hosts may be on two opposite sides of the earth, connected by routers and links. As the physical infrastructure of the two hosts and the intermediate can be different, so for this reason , the Application processes use the logical communication of the Transport Layer to send message from one host to other and be free from the worry of the physical infrastructure used.
Different Protocols of Transport Layer:
1. Transmission Control Protocol (TCP)
TCP provides a reliable and connection-oriented service to the Application. On the other hand, UDP provides a unreliable and connection-less service to the Application. Thus, it is upto the Application Developer, which transport Layer protocol has to be used. For example: In case of HTTP, it is built over TCP.
Transmission Control Protocol (TCP):
2. TCP delivers the packet in their respective order. This means, from the source, in the order in which you will send the packet, they will reach in the same order at the destination.
User Datagram Protocol (UDP):
1. UDP provides non-reliable data delivery. It is a connection-less service provider.
2. UDP doesn’t guarantee the delivery of packets in the order they are sent.
3. Its a light protocol.
Relationship Between Network and Transport layer:
On one hand , the Transport Layer provides communication between processes, whereas on the other hand, the Network Layer provides communication between hosts. Recall the above example of two bungalows and compare it with that. I am sure, you will understand it.
Thank you for reading this article. We hope you enjoyed it.
This is all from us on basics of Basics of Transport Layer. Do you have some information to put spotlight on ?