TCP/IP Protocol – part 3

See in Portuguese.

Continuing our tutorial about TCP/IP, we will see the layers in which this protocol (or protocol suite) is divided. If you missed any part of the tutorial, visit the links:

Part 1Part 2

Layers of TCP/IP

The layers are to better organize the TCP/IP protocol. They serve to define where exactly does a technology in the process. Taking again our example of the industry, imagine that the treadmill is the TCP / IP protocol. Every part of this treadmill is a layer. If there is a problem at Layer 3, for example, we know exactly where it’s thus facilitating the resolution of this problem.

Previously, the TCP/IP protocol had four layers: network, inter-network, transport and application. This model is now obsolete, thanks to the influence of the OSI Model (divided into seven layers as we will see forward), has adapted and now has 5 layers.

As lower the layer number is, further to end user are. These layers are known for low-level layers. The nearest layers of the user are called high-level layers.

The layers of the TCP/IP accepted today, starting with the lower-level layer are:

  1. Physical;
  2. Link;
  3. Network;
  4. Transport;
  5. Application.


Now look at the characteristics of each layer.

1. Physical Layer

As its name says, this refers to the hardware responsible for data traffic. They are the cables and network cards.

This layer encodes the data, ie, the transformation is performed of digital data from the computer to analog signals. Only then can transit through the broadband signal and be compatible with the cables. They are decoded back to digital on the other node. Examples of components of the physical layer: modem, RJ-45 cable, network card, Bluetooth, USB.

2. Link Layer

In this layer are all technologies and devices responsible for the transmission of data through the physical layer. This can be divided into two sublayers: LLC and MAC. In LLC there’s an interface to the upper layer, while at the MAC there’s control of media access via MAC address. Examples of items of link layer: Ethernet (wired network technology), IEEE 802.11 (Wi Fi technology), switch, Token Ring, FDDI.

3. Network Layer

Layer responsible for the technology that controls the operation of the network, such as routing of packets between networks, congestion control (bottleneck) and count the amount of transferred data (for example, so that the telephone operator can limit its traffic to 10 GB) . By example of the technologies that layer have IPv4, IPv6, ICMP (Ping), NAT.

4. Transport Layer

As the name implies is the layer responsible for the transport of data efficiently and economically. This layer must ensure that packets arrive at the destination free of errors and their sequence. Examples of technologies of this layer: NetBEUI, TCP, UDP, RIP, DCCP.

5. Application Layer

In this last layer, which is closest to the user, we have the services for applications and the connection between the network and the applications that are installed on the user’s computer.

Examples of application layer protocols: HTTP (HTTPS), SMTP, FTP, RDP, POP3 (email), IMAP (e-mail), DNS (domain addresses), Telnet.

For now, is just…

As we see in this post, all characteristics Como vimos nessa postagem, all the features that make up the TCP/IP protocol layers were presented. We’ll see in the coming posts which is the OSI Model and which differs from the proposed model for TCP/IP. Wait…

Part 1Part 2

To be continued…


Wiki (Application Layer), Tecmundo, YouTube, Clube do Hardware.

Author: Esdras Nunes.

Rede LAN Soluções em Informática.

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