I wrote this essay and it might be useful to show anyone how to troubleshoot their network problems...

Having the Internet is a very crucial feature, for many users. When the internet drops out, the workplace can almost come to a crawl or halt. The Technician must try to upkeep the internet at all times if possible, and minimize the troubles associated with keeping users connected. An easy way at troubleshooting to see if the network will not connect, can be described in the Open Systems Interconnect (OSI) Model, which was created in the 80s to standardize how different machines with different Operating Systems (OS), would look at troubleshooting the networks. The whole picture is divided into seven layers, which are associated with connectivity and troubleshooting. To get out onto, the internet, the first four layers are dealt with, the rest are OS-dependent.

Getting onto the internet may simply not work, because the user(s) may not be plugged in. This is referred to the Physical Layer of the OSI Model and it is at the first and lowest layer, it deals only with bits. The exception is users who are using wireless radio frequencies, which do not use wires, but the scenario is the same. First, the user or technician will have to search around for a network cable, commonly the RJ-45 Jack (Diagram at end), which usually has a plug and a tab which must be firmly pressed into the computer’s Network Interface Port (NIC/NIP) (Diagram at end). Then, the user will have to search around for an end to the cable which will probably lead into a drop into the wall, in which case the technician will have to use a cable tester, and see if there is good connectivity between the drop and a repeater, hub, switch, or a router. If it doesn’t register as being good then the technician will have to either remove the cable, or send the user to another open machine to work on. For wireless fidelity (Wi-Fi) users, there may be certain obstacles blocking the signal from passing to the wireless access point. To improve this, a user may have to move to an open spot or use a wired connection. To prevent, loss of internet a user may have to always check to see if he/she is “plugged” in.

If the problem does not reside on the first layer, a user may have to go up to the next layer, which is called the data link layer of the OSI Model. Here the media access control (MAC) addressing is used. A computer does not get a Mac address, because it is already burned onto the NIC, and a user cannot change it simply, it is a flat physical address. A user can see what his/her Mac address is by going to Start then go to Run and type in cmd or command , and hit ok, and when it pops up type in getmac and it will display the Mac or physical address. There might be other address, but that is only because the IPv6 protocol uses another Mac address from a virtual tunneling device (Virtual NIC). If a physical address pops up for the user after they type in the commands, then the problem does not reside on the second layer of the OSI Model.

As the layers go up, the network or third layer is next. This is where the IP Addressing comes into play. It is a logical, meaning it isn’t burned into the NIC, and dynamic protocol (set of defined rules), so it doesn’t stay with your machine. A computer may have manual addressing or get its configuration from a Dynamic Host Configuration Protocol Server (DHCP). If a user wants to view their IP Address then they would have to repeat the steps to view their Mac, but instead of typing in getmac, a user would enter ipconfig or ipconfig /all, but ipconfig will suffice. If the IP Address which a diagram will be provided at the end starts with 169.254.x.x then the DHCP server was not found and Windows automatically assigned itself its IP Address by way of Automatic Private IP Addressing (APIPA). If one user has APIPA, and another user has gotten its IP from a DHCP, then both cannot communicate on the same network, because IP has to be the same Network address (192.168.0.x) to “talk” to each other. The user still at the Command Prompt screen can ping other computers to see if they get a reply, if they can, then the problem does not reside on the third or network layer.

The last layer that deals with internet connectivity is the fourth layer or the Transport protocol. It deals with how messages should get from one place to another, using both, the Mac and IP Addresses. The commonly used protocol is called Transmission Control Protocol (TCP). It is used in conjunction with IP (TCP/IP). There are other protocols for example Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) from Novell, and SPX is the Transport Protocol, while IPX is a logical address and belongs with the third layer. A user cannot see the transport protocol in action, because there is no command to view that is actually working. Using commands like ping and tracert in a command prompt, show that packets, which are the things being sent, show that the Transport Protocol is working. Usually, if the user has an IP address from a DHCP server, then the transport protocol is working. If a user connects to another computer on the network, then Transport protocol is working as well.

To recap, for a user to be able to connect to the internet, four things must be considered. First, the user must be plugged in, or have a usable path for Wi-Fi to the access point. Second, the user must have a physical, flat address to even be distinguished from other machines, by having a Mac Address. Third, a user must have a logical, static or dynamic IP Address. Finally, the user must have some protocol to even be able to send the message or get onto the internet to the right machine or router, which determines best path selection. If a user has all of these correct, then the last three layers, will deal on the OSes respectively.