The TCP/IP reference model
Welcome back guys, in the previous article we had studied the ISO OSI model. In this article we gonna be taking look at the TCP/IP reference model. This is most well know and mostly used model for computer networks. I know the model you guys will be seeing soon will be not as same as you thought, but that model is pretty necessary to understand for the functionality of layers. Then later we will discuss picture in your mind “The Hybrid TCP Model”.
Early TCP Model.
As we have seen in the network model, we have seven layers in that model. But things are little simple here “actually the model is pressurized into the smaller model but still some functionalities are same”, we only have 4 layers in early TCP Model refer the following image.
Now let’s discuss every layer one by one.
Link Layer:
This is the lowest layer or layer 1 in early TCP Model. We can see from the above image that Physical Layer (layer1) and Data Link Layer (Layer 2) from the OSI model are fused together into the Link Layer of early TCP. So gradually this layer will inherits the functionality of Layer 1 and Layer 2 from OSI model. So this layer is responsible for connecting the computing devices across wired and non-wired networks. This layer is also responsible for the packet routing through the layer. More than the layer it’s simply the interface for connection.
Internet Layer:
This layer holds the architecture of all the model together because it controls all the permission for packet injection into the network. Here is small justification, we connect to secure wireless network using the valid username and password. Sometime the order of packets sent by the host can’t be maintained and may change while transmitting so if the above layers want the packet in order then they will have to arrange them by themselves.
The reason for changed order of packets is because when host send the packets, all packets will travel together will not be case all time. Some packets may need to take another path to reach its destination, in this path a packet may need to switch many network due to traffic for network fault. There is official protocol defined into the internet layer mainly known as IP (Internet Protocol) and companion to this protocol is ICMP (Internet Control Message Protocol) in order to complete its function.
Transport Layer:
Layer 3 is known as the Transport Layer, it is having the similar functionalities as in the OSI model. This layer is responsible to establish the connection between the two or more peers. In this layer two end-to-end peer connection protocols are used.
TCP(Transmission Control Protocol):
This is the secured and reliable end-to-end connection protocol, in with the data is been sent into the byte stream without making much error. The data is been fragmented and sent into the network layer. Now on the receiver’s side the fragmented packets are collected and then reassemble into the data which will make some sense. TCP also make sure that the sender not just spams the receiver if it can’t handle it such manner and so that’s the reason why this protocol is more reliable.
UDP(User Datagram Protocol):
The User Datagram Protocol is quite not reliable such as TCP in case where accuracy is mattered because like TCP this will not fragment the data and will send the all data in one shot, in such case the errors will increase. So typically this protocols are used for delivering the audio or video form of the data where minimal change in the data can be accepted.
Application Layer:
While comparing OSI and TCP model the major difference we can see is in the application model. Unlike the OSI model here Application Layer, Session Layer, and Presentation Layer, the whole thing is considered as the application layer in TCP model. The reason is because these layers do not differ to each other in large way. The Layer 4 (Application Layer) deals with the higher level protocols like SMTP, DNS, HTTP and RTP. We will discuss each of these protocols in the separate article. Despite this all other stuff are same as those in OSI model.
Ok now that’s it for early TCP/IP model now let’s look at the model that you may have in the mind.
Hybrid TCP/IP Model
As the early TCP model got older and new technologies come into the era, scientist found the need to split the Layer 1 (Link Layer) for the model. Another reason was that, new devices came into the market which work on the link layer but was having quite a bit different functionality. For examples Switch and hubs must be the part of the layer1 according to the early TCP Model, but we know that they are pretty much different. So again the new model was formed i.e. Hybrid TCP/IP model. This model inherits some features from both the early TCP model and OSI model.
Now let’s again visit the layers one-by-one but in very brief manner for our new hybrid TCP/IP model.
Physical layer: This is responsible to choose the medium for the data to be sent. E.g. Optical Fibers, copper cables.
Data Link Layer: Responsible for the fragmentation of the data and provide reliability. Because it specify the length of the packet to be sent.
Network Layer: This is responsible to connect the various network together including the network with 2 peers. Also responsible for routing the packets.
Transport Layer: Provides the reliability and abstraction for the network layer as its companion.
Application Layer: This is the final layer which uses the computer networks.
Hope now the TCP/IP model is clear to you guys , thanks for reading this article and I will see you guys in my next article.You can also read my blog on : OSI Model |What Are 7 Different Layers Of OSI Model ?
