After a brief and conceptual introduction of computer network, the teacher gave us more detailed knowledge of it in recent weeks.
There are many things that I newly learn, but OSI Seven-Layer Model and Protocols impressed me most, not only because they are significant basis in computer network but also for they confused me a lot when I was firstly exposed to them.
In order to make the communication process through network clearer, the layer models are brought out. There are 7 layers in the layer models – Application, Presentation, Session, Transport, Network, Data Link and Physical. Each of them has particular function during the communication, and it is shown as below,
I easily confuse them with each other. For example, I sometimes might mistake Data Link layer as Network layer at the beginning for they have some similar function (such as both adding a header to the transmitted data). However, after several lessons, I have almost understood them and can distinguish them by now.
Protocols are rules that govern the communications. There are many protocols, such as, HTTP, TCP, UDP, IP, etc. I was suddenly enlightened after that lesson when the teacher talked about the protocols.
In the past, I was puzzled why each address of the webpage has “http:” in the front of it. But I haven known now that it represents the Hyper Text Transport Protocol (HTTP). I also got some knowledge of other protocols. For instance, TCP is connection oriented and error free while UDP is connectionless and only tries its best while transmitting data (which means not error free).
Computer network is complicated and abstract, but if I go deeper into it, I can find more interesting things. In fact, I am still feeling confused about many of the protocols, and I hope I could make them completely clear after the following few weeks!
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