Week 2: Day 007 - TCP/IP (Continued)

Hello again! I'm back with some more informational posts to prepare for my Network+ certification. I will continue where I left off (which is at TCP/IP's transport layer.)

Let's start then; so last time I said that the Transport layer is responsible for managing important tasks such as VoIP's (Voice-Over IP) and I identified the differences between TCP and UDP. Now let's talk about TCP segments. When a packet has its IP removed, there is a container known as a "TCP segment" which checks whether the data is going to the right destination. Parts of these segments are known as "Cheksums" and "Flags" (maybe I will delve into what those are later.) The TCP and UDP protocols are then responsible for breaking down data and adding ports to data coming in from the Application layer, and that is the next layer.

So, the next layer, and last layer is known as the "Application Layer" and in comparison to the OSI model it includes the last three layers, the Session, Presentation, and Application layers. Every application must know how to control remote systems (in particular the connection based apps.) TCP/IP applications are each given a unique port number. Some of them are extremely popular for different reasons. For example, some ports are used for gaming servers which makes them popular among gaming server hosts and gamers in general. In the TCP/IP model the API (Application Program Interface) is a part of the Application layer (like the OSI model); However, by definition all applications are aware of their networks. Every TCP/IP application needs to talk to the network to function properly. This is essential for using internet browsers and playing multiplayer video games.

Finally, to summarize, the Application Layer programs generate data, the Transport Layer break the data into chunks and assign them to either the TCP or UDP protocol. The Internet Layer hands out IPs and creates IP packets. Then the Link Layer puts the IP packet into frames using MAC addresses and FCS (Frame Check Sequence). At this point the data is ready to go through ethernet or wireless.

In conclusion, the OSI Seven-Layer Model and the TCP/IP model provide great models which make it easier for people to diagnose issues. This can be used in cases such as a device that is not working properly over the network. By "easier to diagnose" I'm essentially saying troubleshooting is not difficult as it comes down to process of elimination. You look for activity on each layer, whether it's working properly or not is where you will find the base of the problem. Now I will leave you with this thought, learning these models are essential to know as it will be a tool for troubleshooting. On that bombshell, goodbye!