M. Niyazi Alpay
M. Niyazi Alpay
M. Niyazi Alpay

I've been interested in computer systems since a very young age, and I've been programming since 2005. I have knowledge in PHP, MySQL, Python, MongoDB, and Linux.



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Structure and Layers of TCP/IP

All connections made on the internet are carried out with specific protocols.

TCP-IP structure consists of four layers:

  • Application
  • Transmission
  • Internet
  • Physical Network

Application Layer

This layer contains applications to be used on the network. Applications such as FTP, DNS, DHCP are found in this layer.

Transmission Layer

This layer is where sessions are organized for communication between computers. TCP and UDP protocols are used.
TCP: Transmission Control Protocol provides controlled communication. Connection is established with mutual confirmation process. Before sending a packet to the destination computer, it checks whether the computer exists or not. If it does, a request is sent, when the request is accepted, the packet is sent, and a response is made regarding whether the packet has reached or not. This ensures reliable transmission.
UDP: Provides unreliable communication, the packet is sent to the destination computer, but it does not check whether the computer exists or not, or whether the packet has been delivered. Therefore, it is faster than TCP.

Internet Layer

Data packets are displayed in this layer according to the IP address. Data from the transmission layer is converted into internet packets here. Routing operations of packets are also performed here.
There are four protocols in this layer.

ARP: Converts IP addresses to MAC addresses.

ICMP: Provides feedback on sent control messages whether they have been delivered or not.

IGMP: Used to determine multicasting groups. Messages can be sent in three ways in a network: to all machines (broadcast message), to a group (multicast), or directly to a machine (directed).

IP: Performs addressing and routing operations of packets.

Physical Network Layer

Shows the network card, cables, etc. of the computer. This layer is responsible for sending data packets to the network and withdrawing them from the network.


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