Data networks and the TCP/IP model

What is the TCP/IP model?

The TCP/IP model, like the OSI model, is just a way to illustrate the operation of computer networks by dissecting network operations into logical layers.

1 - Network Access Layer

The network access layer combines two important functions, physical data transfer and communication in a local network with MAC addresses, which are separated into two separate layers in the OSI model ("Physical layer" and "Link layer").

Physical data transfer: The physical layer is responsible for data transfer over the physical network. For example, in a wireless home network, this means transforming the wireless signal into electronic or radio frequency signals and receiving it in the computer's wireless adapter.

The goal of physical data transfer is to convert analog to digital and to transfer bits (zeros and ones) from point A to point B using a medium such as a cable or radio waves.

Communication over a local area network using MAC addresses: Another important task of the network's data link layer is to enable communication between network devices within the local area network, from sender to receiver, using MAC addresses as the sender and receiver.

The basic layer also includes the ARP protocol, which is a kind of support protocol that enables the use of internal IP addresses in addition to MAC addresses on a local network.

2 - Internet Layer

The internet layer is responsible for routing network traffic on the Internet using the IP protocol, using IP addresses as the sender and receiver. The IP protocol also includes ICMP, which enables tools such as ping and traceroute.

3 - Transport Layer

The transport layer enables reliable data transfer between the source and destination address. The key components of the transport layer are TCP and UDP protocols.

• TCP: The TCP protocol is used to ensure that data arrives in the correct order and without errors.
• UDP: Unlike TCP, the UDP protocol does not really check anything. It just sends the data out into the world like a message in a bottle and hopes that someone receives the message.

4 - Application Layer

The application layer is the top layer of the TCP/IP model and is responsible for data communication between different applications. Important protocols in this layer that we will familiarize ourselves with in this course are:

• DNS: Protocol by which domain names (such as www.hakatemia.fi) are converted into IP addresses so that, for example, browsers can connect to them.
• DHCP: Protocol used to automatically distribute network settings (especially IP addresses) to network devices in a local area network.

In addition, in the application layer, there are numerous protocols that we will explore in more detail in other courses, such as TLS, which enables encrypted HTTPS connections, and HTTP itself, which enables the existence of websites.

We will study these different parts of the network more closely in the sections of the course. Just answer the questions and move on to the next module!

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