TCP IP Layers – Five layer network model

TCP/IP forms the core mechanism of a conceptual networking model that collectively forms the internet protocol suite. It is responsible for the communication that takes place on the network. In general, TCP/IP has five different layers. Those are:

  • Application Layer
  • Transport Layer
  • Internet Layer
  • Data Link Layer
  • Physical Layer

Each of these layers supports a relevant set of protocols that perform unique functions. Notably, contrary to the OSI model that has 7 layers – the TCP/IP model performs all the functions using fewer layers.  Its two protocols namely, TCP and IP are main driving force of the modern internet and network paradigm and are responsible for providing a flexible networking functionality, thence streamlining the connectivity of many devices having distinctive architectures.

In TCP/IP, a secure connectivity is ensured by safeguarding the end to end node verification i.e. from source to destination. It helps in a secure data transfer. Dynamic routing is another excellent feature that the TCP/IP model offers. It aids in selecting the shortest and secured path of data packets to their destination. Dynamic routing helps disperse those data packets over a dynamically selected path that remains unknown till the last point, hence providing a much needed data security feature.

We’ve talked about the pros of TCP/IP but it has a few cons too. Not worrying though. Firstly, it’s not very convenient to change the protocol, if required. Secondly, there isn’t too much documentation provided regarding the functionalities of different layers as in the OSI model. So there’s always an element of doubt over what layer does what specifically.

Now, let’s highlight some basic functionality of different layers in a TCP/IP model:

  1. Physical Layer: Situated at the bottom of the TCP/IP model, this layer is responsible for controlling the data bits in a network. It facilitates the host to host communication. It also specifies the data rate, topology of a network, among other things such as mode and medium of transferring data i.e. whether it’s full duplex, half duplex, simplex, over a wired or wireless connection respectively. The protocols used in this layer differ with respect to different networks so it doesn’t specify any particular protocol to be used in it.
  2. Data Link Layer: This layer creates data frames by appending header information of the data packets to be able to deliver it to a correct destination. It is done by adding a physical address to data packets so as to help transfer it over a desired route.
  3. Internet Layer: This layer creates data packets or data-grams by addressing them logically to an IP address. It then routes the data packets with the help of assigned IP addresses using the routers. It is an important layer that specifies different protocols for a logical data transfer over the network. IP, ICMP, ARP, RARP are some of the protocols used in this layer.
  4. Transport Layer: This layer processes data received from the above layers to create data segments. The transport layer then transfers the data by establishing a connection with the layers underneath it. In general, this layer is responsible for the end to end data transmission without any errors, and by controlling the flow rate of data. TCP and UDP are the two protocols used in this layer.
  5. Application Layer: This is a last layer of the TCP/IP model that handles the functionality of network connections, data encryption, decryption, translation, and data synchronization. It provides a mechanism to carry out communication between network services and the computer system application programs for the end users – for services such as internet browsing, ftp transfers, emails, etc. It uses top level protocols such as FTP, Telnet, HTTP, HTTPS, DHCP, SMTP, SNMP, among others.

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