OSI Model

OSI Model

OSI Model

The OSI Model was developed to help provide a better understanding of how a network operates.  The better you understand the model the better you will understand networking.  It is composed of seven OSI layers.  Each layer is unique and supports the creation and control of data packets.  The layers start with Physical and ends with the Application.  The first three layers relate to network equipment.  For example, switches are layer 2 devices and a routers are layer 3 devices.  See the YouTube video to learn more.

The first layer is the  Physical layer and is where the data is either put onto the media or taken off the media.  The media could be the network cable or wireless.  The data is in the form of bits and is called Bits as the PDU (protocol data unit).  These bits can be voltage levels that represent binary numbers of 1 or 0.  They could also be light pules traveling on a fiber optic cable or radio wave pulses for a wireless network.

The second layer is the Data Link layer and is where framing of the data takes place.  The Frame is the PDU name at this layer.  The MAC (media access control) physical address is added or removed depending on which direction the data is traveling.  The MAC address is used by switches to switch the data to the appropriate computer or node that it is intended for in a LAN (local area network).

The third layer is the Network layer and is where the IP (internet protocol) address is added or removed and the PDU at this layer is called a Packet.  Routers operate at this level and use the IP (logical address) to route the data to the appropriate network.  Network locations are found by the routers using routing tables to locate the appropriate networks.

The fourth layer is the Transport layer and is where the data is segmented (broken into pieces) and used by the TCP protocol to ensure accurate and reliable data is transferred.  The data segments are numbers so that proper sequencing can be determined on the receiving side in order to rebuild accurate files.  The PDU name at this layer is called Segment.

The fifth layer is the Session layer and is where the session is created, maintained, and torn-down when finished.

The sixth layer is the Presentation layer and is where the data is formatted or decrypted into files that the user can understand.

The seventh layer is the Application layer and is the user interface to the network where that data is either being generated or received.

The study of Computer Repair Training and the OSI Model can help you to prepare for certification and employment is this exciting field.

Computer Technician

If you’re like most people, handling computer repairs on your own can seem like an impossible task. Software programs and hardware issues are best left to the experts to avoid any additional damages people often cause when trying to fix even a simple problem. Working with a computer technician is an easy and effective way to get any problems with your computer fixed in a quick and easy way.

A technician specializes in repairing and updating computer systems so that they can perform as well as possible. Technicians work with software, hardware, and internet to help create the best possible computer experience for you. A good tech can work with laptops, desktops, routers, wireless modems, and other devices.

Many people seek the help of a computer professional because their computer starts to perform slowly. Over time, a computer can begin to start up slowly, freeze while being used, or refuse to load certain important programs. When this happens, it’s important to work with a professional computer technician to get the problem resolved properly. When people try to repair computer issues on their own, sometimes they can cause additional damage. Because software and hardware have to be handled in a very specific way in order to get them to perform properly, it’s best to leave all repairs to an expert technician.

Working with a tech is the popular choice for many individuals and businesses that need repairs done to their computers. Having a professional on your side means that you’ll get the best possible repairs without having to problem solve or learn complicated things by yourself. Computer repair technicians have experience and expertise which allows them to solve and fix any computer problems quickly while saving you lots of time and money in the process.

If you have any questions about choosing new software or adding hardware upgrades to your laptop or desktop, working with a computer technician is a great way to make the right choices and have the installation done perfectly. You can find computer technicians who will visit your home or office, some that require you to bring your machine to their office, and others who can walk you through repairs over the phone.

The website Computer Repair Training has additional information that you might find useful.

Free Proxy Server List

The communist Chinese government has been filtering much of what the Chinese people are able to access on the

Proxy Server - YouTube

Internet.  Therefore, proxy servers have been very helpful for the Chinese to get around these government filters.  One of the best proxy servers originally setup to circumvent the government filters is UltraSurf.  It is a stand-alone program that reconfigures and redirects the Microsoft Internet Explorer’s proxy settings.  UltraSurf servers also employ a range of IP addresses which makes it harder to block.  I have provided a free proxy server list of some of the top proxies at the end of this article.

Proxy servers have been around a long time.  Microsoft developed a proxy server program to help speed up computer Internet access by caching common searches, which frees up valuable bandwidth by redirecting searches to the cache.  Proxy servers also allow filtering of IP addresses and content.  Individual IP addresses can be blocked along with words, phrases, or domain names.

Tunneling is a term used with proxy servers because proxies can easily penetrate network firewalls and filters by rerouting searches and traffic through the proxy servers.  Proxies act as a go between for all traffic that would otherwise be blocked by filters by capturing the traffic and rerouting.  This technique allows you to tunnel or pass right through a filter.  Filters block IP addresses so the proxy by using a different IP address can reroute the traffic through an unblocked IP address.  Network administrators need to be aware of the most commonly used proxies and block the ranges of IP addresses most used by the proxies.

WARNING!!! The dangers in using free proxies are that many hackers setup free proxies to steal credit cards and other personal information.  When connecting to a proxy all your data moves through their server so they are able to capture and monitor all data and content.

WARNING!!! Again use caution when using a proxy and remember all data and content can be easily captured and monitored.  So never make purchases or use credit cards, or connect to email or other accounts using ids and passwords, because your accounts and credit cards can be easily compromised.

The number one proxy on the free proxy server list is UltraSurf.  They have high performing servers and high bandwidth connections to the Internet.  Number two would be freeproxyserver.net, three is hidemyass.com, and four is turbohide.com.

Important Note: Remember use proxies at your own risk and/or peril.

The website Computer Repair Training Plus has additional information that you might find useful.