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Confused, How to write resignation letter? Now I will show you, example of resignation letter. Please write comment If you have other letter.

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When a problem occurs on your network, what do you usually do first? Do you ping the network device to see whether it is up and responding? Do you dive into the network closet to determine whether the LED lights are still blinking green or switched to red? Do you contact the user who called or log into the NMS that notified to find out more about the problem?

In each situation, the most important part of troubleshooting is developing a good technique. No matter what the problem is on your network, you’ll find that having a good technique for finding that problem helps you quickly identify where the root cause exists so that you can work towards a solution.

The basis of each of these troubleshooting approaches is the seven-layer OSI Reference Model. If you’re unfamiliar with the OSI model or just rusty on the details, here’s a look at the seven layers:

Three different approaches
Network administrators who use OSI as a troubleshooting framework typically navigate the model in one of three ways: Bottom-Up, Top-Down, and Divide-and-Conquer. Depending on how the problem manifests and their experience level, they may choose one method over another for that particular problem. Each of these approaches has its utility based on the type of problem that is occurring. Let’s look at each.

Bottom-Up
The Bottom-Up approach simply means that administrators start at the bottom of the OSI model and work their way up through the various levels as they strike off potential root causes that are not causing the problem. An administrator using the Bottom-Up approach will typically start by looking at the physical layer issues, determine whether a break in network connectivity has occurred, and then work up through network interface configurations and error rates, and continue through IP and TCP/UDP errors such as routing, fragmentation, and blocked ports before looking at the individual applications experiencing the problem.

This approach works best in situations in which the network is fully down or experiencing numerous low-level errors. It also works best when the problem is particularly complex. In complex problems, the faulting application often does not provide enough debugging data to the administrator to give insight as to the problem. Thus, a network-focused approach works best.

Top-Down
The Top-Down approach is the reverse of the Bottom-Up approach in that the administrator starts at the top of the OSI model first, looking at the faulted application and attempting to track down why that application is faulted. This model works best when the network is in a known-good state and a new application or application reconfiguration is being completed on the network. The administrator can start by ensuring the application is properly configured, then work downward to ensure that full IP connectivity and appropriate ports are open for proper functionality of the application. Once all upper-level issues are resolved, a back-check on the network can be done to validate its proper functionality. As said earlier, this approach is typically used when the network itself is believed to be functioning correctly but a new network application is being introduced or an existing one is being reconfigured or repurposed.

Divide-and-Conquer
The Divide-and-Conquer approach is a fancy name for the “gut feeling” approach. It is typically used by seasoned administrators who have a good internal understanding of the network and the problems it can face. The Divide-and-Conquer approach involves an innate feeling for where the problem may occur, starting with that layer of the OSI model first, and working out from that location. This approach can also be used for trivial issues that the administrator has seen before.

Choosing an approach
Which approach you decide to use may depend on where you believe the problem lies. For example, if a user is unable to browse the Web and you think most users have a lot of problems with spyware and Internet Explorer settings, then you may want to start with the top-down approach. On the other hand, if the user mentions that he or she just connected a laptop to the network and can’t browse the Web, you might want to use the bottom-up method since there’s a good chance the user has a disconnected cable or similar problem.

Do you use a troubleshooting methodology when dealing with networking problems? If so, post your approach in this article’s discussion. How important do you think it is to have a troubleshooting methodology?

In Summary
Now you may not be a network administrator but the OSI model can help anyone troubleshoot any networking problem. I hope that this example gave you some ideas as to how you can use the OSI model, everyday, to troubleshoot your networking problems.

Ref:
techrepublic – petri – techtarget

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the OSI model is a standard theoretical model for how networking hardware, software, protocols work together

Layer 1: Physical Layer
The bulk of your documentation needs to be done at Layer 1. A full description of each device on the network is essential for inventory control, future upgrade planning, and physical security. Device, in this instance, refers to computer hardware, peripherals, routers, and switches. You should also make sure that you document network cabling and patch panels.

You may want to make use of system inventory software to simplify documenting these items, especially in larger organizations. If you want to get a flavor for what these software packages can do, check out Belarc Advisor, a free download that allows you to audit the hardware, gather operating system information, and get a list of installed application versions for one PC. Belarc and other vendors offer more robust packages that can be used by businesses to automatically gather information from hardware and software throughout your network.

You should also diagram the topology and architecture of the network using a tool such as Microsoft Visio, and this diagram should be kept up-to-date as the network changes. This diagram can help you do some pre-emptive planning and answer important questions about your network. Are hubs close to being maxed out? If just a few nodes are added to the topology, will it push you into a quick buying decision? This is valuable information for the managers of your organization, and your documentation could be the ammunition you need to get new purchases approved during planning meetings with management.

Layer 2: Data Link Layer
The Data Link Layer is responsible for the communication between the network and the physical layers. One of the primary network specifications handled at the Data Link Layer is the hardware address (also called the MAC address) of network adapter cards. Every network adapter in the world has a unique hardware address, based on the vendor of the adapter.

You should have a list of MAC addresses for each network adapter on your network. You should know what speed they are and what protocols they support. Plus, you should have statistics from a network monitoring application that shows baseline information about activity on your network.

Layer 3: Network Layer
The Network Layer defines the standards of how data is communicated across your network and between your network and other networks, including the Internet. Network Layer documentation should include information about WAN links, Internet connections, and VPN and RAS servers.

This is the layer that is responsible for converting a logical name into an IP address. So the documentation of your subnet should include a map of NetBIOS/Host names and IP addresses, DHCP scopes, gateway/router addresses, proxy server addresses, WINS and DNS server addresses, and IP addresses and information on any other network servers.

Network Layer documentation should also include policies on the naming conventions of computers and users, domain controllers, and routers/switches.

Layer 4: Transport Layer
The Transport Layer is responsible for the packets getting to their destination in the proper sequence and without errors. This is a critical layer for security, especially firewalls and screening routers. The two primary protocols that operate at this layer are TCP and UDP, and one of the main methods that firewalls use to block or allow traffic is based upon TCP and UDP port numbers. Your documentation should include a list of which port numbers your firewall(s) allows.

Layer 5: Session Layer
The Session Layer makes sure that a system can open a communications connection with a remote system and that data can flow back and forth between the systems. Examples of protocols that work at the Session Layer include Telnet, SSH, SNMP, and SSL. In terms of documentation, you should include SSL-enabled sites in security documentation, and you should have a policy about having SNMP enabled for network monitoring and management. Telnet and SSH will probably be documented as part of your remote access plan for administrators.

Layer 6: Presentation Layer
The Presentation Layer transforms data into a form understandable to the recipient. If encryption is required, it takes place here, as does decryption. The Presentation Layer also participates in encapsulation and decapsulation and encoding and decoding, such as in multimedia applications like MPEG. There really aren’t any documentation activities that relate specifically to the Presentation Layer.

Layer 7: Application Layer
The Application Layer is the interface that controls applications such as e-mail and other applications used to send or receive information. I’ll use this space to talk about application in the more traditional sense—the ones that are installed on operating systems.

The network administrator must have policies in writing from the powers-that-be that spell out what applications should be available on the network and to whom. Without this document, administrators are in a precarious position. If a user wants an application, and you withhold it with no written policy, you face appeal. If you give a user an application, and someone higher up doesn’t think you should have done so, you face reprimand. If you have policies in hand that make the decisions for you, you will have the needed consistency.

This graphic is courtesy of the Abdus Salam International Centre for Theoretical Physics. Here’s how the OSI model works: Traffic flows down from the application to the physical layer across the network using the physical medium (for example, an Ethernet cable) to the receiver’s physical layer. It then moves up through the layers to the receiver’s application.

On the left hand side is a user. On the right hand side, you could have a server. Every request AND response has to travel from the left, down every layer, to the physical layer, across the physical layer, up the layers on the right, and up to the server on the top right hand corner.

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Finally I can use a new NATMAG Them.I wish it’s better and more user friendly then  my old theme.

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Why we use FIBER OPTIC CABLE ? Fiber optic cable is quickly becoming the industry standard in computer networking, telecommunications and even home audio equipment. Fiber optic cable offers many advantages over other types of cable used to transmit audio, video and voice data.

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Apakah ada aplikasi desain yang Open Source dengan kemampuan seperti PhotoShop?

GIMP singkatan dari GNU Image Manipulation Program. Sebuah aplikasi desain open source yang memiliki kemampuan menyerupai Adobe PhotoShop atau bahkan melebihi paint bawaan windows.

GIMP Memiliki banyak kemampuan. Dapat digunakan sebagai program paint yang sederhana, expert quality photo retouching program, sistem online batch processing, sebuah produksi massa renderer gambar, konversi format gambar, dll

GIMP dapat dikembangkan dan diperluas. It is designed to be augmented with plug-ins and extensions to do just about anything. Perangkat ini dirancang untuk ditambahkan dengan plug-in dan ekstensi untuk dapat meng-handle manipulasi segala hal. Advanced scripting interface memungkinkan semuanya dari tugas sederhana hingga paling proses manipulasi gambar yang kompleks menjadi mudah & sederhana.

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Apakah ada aplikasi Open Source yang memiliki kemampuan serupa dengan Illustrator atau Corel Draw?

Sebuah aplikasi desain opensource yang berbasis vector dengan kemampuan serupa dengan Illustrator, CorelDraw, atau Xara X, dengan menggunakan standar W3C Scalable Vector Graphics (SVG) format file yaitu INKSCAPE.

Inkscape mendukung berbagai berbagai kelengkapan fitur-fitur SVG yang dilakukan dalam merancang sebuah streamline antarmuka. Sangat mudah untuk mengedit node, melakukan path operations, trace bitmaps dan banyak lagi. We also aim to maintain a thriving user and developer community by using open, community-oriented development. Inkscape juga bertujuan untuk mempertahankan yang berkembang komunitas pengguna dan pengembang dengan menggunakan Open Source.

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How we can Find out… Which browser offers the best performance on your system? Which browser is the fastest? Which browser is the popular?

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Benchmarking is the process of comparing the cost, cycle time, productivity, or quality of a specific process or method to another that is widely considered to be an industry standard or best practice. The result is often a business case for making changes in order to make improvements. The term benchmarking was first used by cobblers to measure ones feet for shoes. They would place the foot on a “bench” and mark to make the pattern for the shoes. Benchmarking is most used to measure performance using a specific indicator (cost per unit of measure, productivity per unit of measure, cycle time of x per unit of measure or defects per unit of measure) resulting in a metric of performance that is then compared to others.

Also referred to as “best practice benchmarking” or “process benchmarking”, it is a process used in management and particularly strategic management, in which organizations evaluate various aspects of their processes in relation to best practice, usually within a peer group defined for the purposes of comparison. This then allows organizations to develop plans on how to make improvements or adopt best practice, usually with the aim of increasing some aspect of performance. Benchmarking may be a one-off event, but is often treated as a continuous process in which organizations continually seek to challenge their practices.

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