Computer RAM Explained!

PictureEvery computer must have Random Access Memory (RAM) in order to function. RAM for computers is different from the hard disk memory in that whereas the hard disk is the place where data is permanently stored even when the computer is turned off, RAM is where the operating system, applications and files are loaded when the computer is turned on and the end user is using it.

The number and size of programs and files that can be loaded onto the RAM for computers at the same time is directly dependent on the size of the RAM. The larger the RAM, the more programs you can run simultaneously. So when you start experiencing deterioration of speed or regular computer freezing when working on your computer, you could be experiencing a computer RAM capacity problem. If that is the case, what you need is additional computer RAM. Upgrading the RAM improves your computer’s overall performance.

If you start to use your computer to carry out tasks that require large program or that generate or manipulate bulky files such as graphic design and video editing, then more computer RAM would help alleviate the problem. Similarly, if you frequently must run several applications at a go, then installing more computer RAM is recommended. Not upgrading the RAM will see the computer respond erratically under the strain of system jobs and in worst case may crash leading to loss of important data.

The need for more RAM for computers can be better understood by looking at what happens whenever the RAM is filled to capacity with currently open programs and files. In such cases, if the end user calls yet another file or application, the computer’s processor marks out and designates a certain portion of the hard disk as virtual memory and loads the new file or application there.

The virtual memory serves as an extension of the RAM for computers. But there is one major problem – the hard disk memory is much slower than the RAM. So even though the virtual memory may shore up the capacity of the RAM, the speed of reading and writing data to the virtual memory negates any such advantage by still slowing down the computer overall especially if there are processes loaded on the RAM that are dependent on the processes or data loaded on virtual memory.

Therefore, upgrading the RAM for computers is more effective than relying or allocating additional virtual memory on the hard disk. Interdependent applications and files can be loaded simultaneously and the interdependence will have minimal impact on response time and overall computer speed.

A computer whose RAM has been upgraded can browse the internet significantly faster. The end users concern will no longer be how long the browser takes to open but rather the connection speed of their internet service. More RAM for computers also makes it easier to print large files such as high resolution images especially if the printer is a shared or network printer since the file may have to be queued on your computer’s RAM before it is released to the printer.

Introduction to Network Security

PictureIntroduction to Networking:

A basic understanding of computer networks is requisite in order to understand the principles of network security. In this section, we’ll cover some of the foundations of computer networking, then move on to an overview of some popular networks. Following that, we’ll take a more in-depth look at TCP/IP, the network protocol suite that is used to run the Internet and many intranets.

Once we’ve covered this, we’ll go back and discuss some of the threats that managers and administrators of computer networks need to confront, and then some tools that can be used to reduce the exposure to the risks of network computing.

What Is Network Security?

In answering the question What is network security?, your IT partner should explain that network security refers to any activities designed to protect your network. Specifically, these activities protect the usability, reliability, integrity, and safety of your network and data. Effective network security targets a variety of threats and stops them from entering or spreading on your network.

What Is Network Security and How Does It Protect You?

After asking what is network security? , you should ask, what are the threats to my network?

Many network security threats today are spread over the Internet. The most common include:

  • Viruses, worms, and Trojan horses
  • Spyware and adware
  • Zero-day attacks, also called zero-hour attacks
  • Hacker attacks
  • Denial of service attacks
  • Data interception and theft
  • Identity theft

How Does Network Security Work?

To understand What is network security?, it helps to understand that no single solution protects you from a variety of threats. You need multiple layers of security. If one fails, others still stand.

Network security is accomplished through hardware and software. The software must be constantly updated and managed to protect you from emerging threats.

A network security system usually consists of many components. Ideally, all components work together, which minimizes maintenance and improves security.

Network security components often include:

  • Anti-virus and anti-spyware
  • Firewall, to block unauthorized access to your network
  • Intrusion prevention systems (IPS), to identify fast-spreading threats, such as zero-day or zero-hour attacks
  • Virtual Private Networks (VPNs), to provide secure remote access.

Network security concepts:

 Network security starts with authenticating, commonly with a username and a password. Since this requires just one detail authenticating the user name —i.e. the password— this is sometimes termed one-factor authentication. With two-factor authentication, something the user ‘has’ is also used (e.g. a security token or ‘dongle’, an ATM card, or a mobile phone); and with three-factor authentication, something the user ‘is’ is also used (e.g. a fingerprint or retinal scan).

Once authenticated, a firewall enforces access policies such as what services are allowed to be accessed by the network users.[2] Though effective to prevent unauthorized access, this component may fail to check potentially harmful content such as computer worms or Trojans being transmitted over the network. Anti-virus software or an intrusion prevention system (IPS)[3] help detect and inhibit the action of such malware. An anomaly-based intrusion detection system may also monitor the network like wire shark traffic and may be logged for audit purposes and for later high-level analysis.

Security management:

Security management for networks is different for all kinds of situations. A home or small office may only require basic security while large businesses may require high-maintenance and advanced software and hardware to prevent malicious attacks from hacking and spamming.

Secure Network Devices:

It’s important to remember that the firewall is only one entry point to your network. Modems, if you allow them to answer incoming calls, can provide an easy means for an attacker to sneak around (rather than through) your front door (or, firewall). Just as castles weren’t built with moats only in the front, your network needs to be protected at all of its entry points.

Secure Modems; Dial-Back Systems:If modem access is to be provided, this should be guarded carefully. The terminal server, or network device that provides dial-up access to your network needs to be actively administered, and its logs need to be examined for strange behavior. Its passwords need to be strong — not ones that can be guessed. Accounts that aren’t actively used should be disabled. In short, it’s the easiest way to get into your network from remote: guard it carefully.

Crypto-Capable Routers:

A feature that is being built into some routers is the ability to use session encryption between specified routers. Because traffic traveling across the Internet can be seen by people in the middle who have the resources (and time) to snoop around, these are advantageous for providing connectivity between two sites, such that there can be secure routes.

Virtual Private Networks:

Given the ubiquity of the Internet, and the considerable expense in private leased lines, many organizations have been building VPNs (Virtual Private Networks). Traditionally, for an organization to provide connectivity between a main office and a satellite one, an expensive data line had to be leased in order to provide direct connectivity between the two offices. Now, a solution that is often more economical is to provide both offices connectivity to the Internet. Then, using the Internet as the medium, the two offices can communicate.

Risk Management: The Game of Security:

It’s very important to understand that in security, one simply cannot say “what’s the best firewall?” There are two extremes: absolute security and absolute access. The closest we can get to an absolutely secure machine is one unplugged from the network, power supply, locked in a safe, and thrown at the bottom of the ocean. Unfortunately, it isn’t terribly useful in this state. A machine with absolute access is extremely convenient to use: it’s simply there, and will do whatever you tell it, without questions, authorization, passwords, or any other mechanism. Unfortunately, this isn’t terribly practical, either: the Internet is a bad neighborhood now, and it isn’t long before some bonehead will tell the computer to do something like self-destruct, after which, it isn’t terribly useful to you.

This is no different from our daily lives. We constantly make decisions about what risks we’re willing to accept. When we get in a car and drive to work, there’s a certain risk that we’re taking. It’s possible that something completely out of control will cause us to become part of an accident on the highway. When we get on an airplane, we’re accepting the level of risk involved as the price of convenience. However, most people have a mental picture of what an acceptable risk is, and won’t go beyond that in most circumstances. If I happen to be upstairs at home, and want to leave for work, I’m not going to jump out the window. Yes, it would be more convenient, but the risk of injury outweighs the advantage of convenience.

Every organization needs to decide for itself where between the two extremes of total security and total access they need to be. A policy needs to articulate this, and then define how that will be enforced with practices and such. Everything that is done in the name of security, then, must enforce that policy uniformly.

Fire walls:

As we’ve seen in our discussion of the Internet and similar networks, connecting an organization to the Internet provides a two-way flow of traffic. This is clearly undesirable in many organizations, as proprietary information is often displayed freely within a corporate intranet (that is, a TCP/IP network, modeled after the Internet that only works within the organization).

In order to provide some level of separation between an organization’s intranet and the Internet, firewalls have been employed. A firewall is simply a group of components that collectively form a barrier between two networks.

A number of terms specific to firewalls and networking are going to be used throughout this section, so let’s introduce them all together.

Bastion host:

A general-purpose computer used to control access between the internal (private) network (intranet) and the Internet (or any other untrusted network). Typically, these are hosts running a flavor of the Unix operating system that has been customized in order to reduce its functionality to only what is necessary in order to support its functions. Many of the general-purpose features have been turned off, and in many cases, completely removed, in order to improve the security of the machine.

Router:

A special purpose computer for connecting networks together. Routers also handle certain functions, such as routing, or managing the traffic on the networks they connect.

Access Control List (ACL):

Many routers now have the ability to selectively perform their duties, based on a number of facts about a packet that comes to it. This includes things like origination address, destination address, destination service port, and so on. These can be employed to limit the sorts of packets that are allowed to come in and go out of a given network.

Demilitarized Zone (DMZ):

The DMZ is a critical part of a firewall: it is a network that is neither part of the untrusted network, nor part of the trusted network. But, this is a network that connects the untrusted to the trusted. The importance of a DMZ is tremendous: someone who breaks into your network from the Internet should have to get through several layers in order to successfully do so. Those layers are provided by various components within the DMZ.

Proxy:

This is the process of having one host act in behalf of another. A host that has the ability to fetch documents from the Internet might be configured as a proxy server, and host on the intranet might be configured to be proxy clients. In this situation, when a host on the intranet wishes to fetch the web page, for example, the browser will make a connection to the proxy server, and request the given URL. The proxy server will fetch the document, and return the result to the client. In this way, all hosts on the intranet are able to access resources on the Internet without having the ability to direct talk to the Internet.

Types of Firewalls:

There are three basic types of firewalls, and we’ll consider each of them:

Application Gateways:The first firewalls were application gateways, and are sometimes known as proxy gateways. These are made up of bastion hosts that run special software to act as a proxy server. This software runs at the Application Layer of our old friend the ISO/OSI Reference Model, hence the name. Clients behind the firewall must be proxitized (that is, must know how to use the proxy, and be configured to do so) in order to use Internet services. Traditionally, these have been the most secure, because they don’t allow anything to pass by default, but need to have the programs written and turned on in order to begin passing traffic.

Packet Filtering:Packet filtering is a technique whereby routers have ACLs (Access Control Lists) turned on. By default, a router will pass all traffic sent it, and will do so without any sort of restrictions. Employing ACLs is a method for enforcing your security policy with regard to what sorts of access you allow the outside world to have to your internal network, and vice versa.

There is less overhead in packet filtering than with an application gateway, because the feature of access control is performed at a lower ISO/OSI layer (typically, the transport or session layer). Due to the lower overhead and the fact that packet filtering is done with routers, which are specialized computers optimized for tasks related to networking, a packet filtering gateway is often much faster than its application layer cousins.

Hybrid Systems:

In an attempt to marry the security of the application layer gateways with the flexibility and speed of packet filtering, some vendors have created systems that use the principles of both.

In some of these systems, new connections must be authenticated and approved at the application layer. Once this has been done, the remainder of the connection is passed down to the session layer, where packet filters watch the connection to ensure that only packets that are part of an ongoing (already authenticated and approved) conversation are being passed.

Other possibilities include using both packet filtering and application layer proxies. The benefits here include providing a measure of protection against your machines that provide services to the Internet (such as a public web server), as well as provide the security of an application layer gateway to the internal network. Additionally, using this method, an attacker, in order to get to services on the internal network, will have to break through the access router, the bastion host, and the choke router.

Conclusions:

Security is a very difficult topic. Everyone has a different idea of what “security” is, and what levels of risk are acceptable. The key for building a secure network is to define what security means to your organization. Once that has been defined, everything that goes on with the network can be evaluated with respect to that policy. Projects and systems can then be broken down into their components, and it becomes much simpler to decide whether what is proposed will conflict with your security policies and practices.

Spyware Protection. Do we need it?

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Spyware is a type of malware but it is distinctively different from the regular computer viruses and hence they are not detected by the regular anti virus software. So, you need specifically designed anti spyware software to successfully remove the spywares.

Every computer and internet user needs to have a little knowledge about spyware and other malicious software. As these programs have the reputation of being quite dangerous for your computer, so it is better you take very good care of it and go for free spyware removers. This malicious stuff can create havoc to your pc, if proper step is not taken on the time, various big corporate houses, banks and other companies and lot of time and money for spyware protection.

Spyware can be installed on your computer without your knowledge, and can result in a number of computer performance issues. Spyware is designed to monitor or control your computer use. It can be used to monitor your web surfing, redirect your browser to particular websites, send pop-up ads, or record your keystrokes, which can ultimately lead to identity theft.

A virus-infected computer coupled with spyware is a very real security threat and the situation should be resolved immediately and decisively. It is good strategy to tackle the problem in a two-pronged manner. First, it is necessary to get a good anti-virus software tool that can scan your computer, detect and remove infected files.

Free Spyware removers are all over the internet, and because of the mechanics of demand and supply, their needs status have just increased ten fold over the past few years. Spyware is a big problem on the internet and the funny thing is, over 90% of people using computers at this very moment do not even know that their computer is being chocked, drawn and quartered by malicious software that is slowly eating away at system resources.

The best way to combat large inter-connected systems is to install windows anti spyware software in each workstation. This will help ease the jamming of networks etc. Many anti spyware companies of course offer free scan and free spyware remover programs. There are several thousands of these on the Internet. Many of these programs function similarly to anti-virus software.

It is also recommended that users run periodic scans to ensure that no harmful files have escaped detection. In addition, it should be kept in mind that free anti spyware or spyware removal programs do not offer antivirus protection, and a separate antivirus program is necessary if you opt for a free spyware removal program.

When choosing a free spyware scanner, make a research about it that will make you choose which of the different software will give you more benefits. Also consider knowing the security and website’s legitimacy so you can’t be fool by many bad guys who offers free tools over the internet. A free spyware scan will make your browsing a lot better.

Many people searching for an anti virus and spyware removal also searched online for anti virus protection a vast, anti virus software review, and even an antivirus software list.

How to Install a Motherboard

PictureIn this article we learn how to install a motherboard. This is your first stop in learning how to install computer components. The motherboard is attached one way or another to every device in your computer.

You will notice that the motherboard comes pre-configured with numerous slots where you can plug devices in. Additionally, there are connectors and jumpers that you will need to set to make it work properly.

Be sure to have your documentation handy at all times. For the purposes of this tutorial we will be working with the standard ATX motherboard common to most mid-tower computers.

1. Open the Case and Remove Motherboard Tray

The first step will be to open the case. The method for doing this will vary depending upon the case you have. For mid-towers, you will most likely have to remove a side panel that sits above where the motherboard will be.

Unscrew the two screws holding this panel onto your computer and slide it out. Set the screws in a safe place. If you have an older style case you may have to remove all of the screws from the back of the chassis, and slide that out.

If your case has a motherboard tray you will need to remove that as well. Some cases have removable motherboard trays meant to help you better install motherboard units correctly. These trays are quite useful and can make installing your motherboard much easier. If your case has such a tray, be sure to remove it as well.

2. Replace the ATX Connector Plate and Align Motherboard with Case

If you check all the parts that came bundled with your motherboard, you will notice that it came with its own face plate. This might seem unusual, as your computer case will have an ATX face plate already installed. The problem here has to do with potential incompatibility. Your ATX face place may have connectors arranged in a different pattern than the one that came with your case.

Therefore, it’s best to use the custom face plate that came with your motherboard. To swap out the computer case face plate, press both corners until it pops out. Snap the new plate in place, aligning the keyboard and mouse connectors to the side of the case where your power supply is installed.

3. Install Standoffs and Secure the Motherboard

The next step in knowing how to install a motherboard involves alignment. You want holes from the case to match the holes from the motherboard–however there’s more to it than that. First, locate the mounting holes in the case or tray that will match up with those of the motherboard.

Now that you’ve found the holes, it’s time to install the standoffs. Standoffs are basically brass or plastic pegs that will support the motherboard as it installed. These pegs or spacers come in different varieties; some will be brass while others will be plastic. Check which ones you have. If the standoffs are of the brass variety, you may need a hex tool of some sort in order to properly install them. Install the standoffs into the holes that you identified earlier.

With the standoffs securely installed, it’s time to secure the motherboard. Align the motherboard over your case or tray so that you can see the standoffs clearly through their matching holes on the motherboard. Then begin from the center of the motherboard to screw the motherboard to your tray or case.

After you complete that, continue clockwise, affixing the screws into the mounting holes in all of the corners of the board. As you can see, knowing how to properly install motherboard units to your PC involves more than just a few turns of the screws!

4. Installing Critical Wires and Connectors

The next step in knowing how to install computer components like your motherboard is to install critical wires and connects. Just because your motherboard is physically installed doesn’t mean it can communicate with the rest of your system.

You’ll have to connect some important wires and cables to complete the process. The first wires are the ones that hang loose from your case, like hard drive, power, reset and speaker leads. Consult your documentation to know how to plug these wires into their appropriate slots in the case.

The next cable is the one that feeds juice to your motherboard, the 20 pin ATX power lead from your power supply. Plug that in the appropriate slot in the motherboard. Some newer computers like the Pentium 4 may also include an additional 4 pin 12v connector from the power supply, which you must plug into the motherboard as well. Check that all of the critical wires are secured. If you used a removable tray you can reinsert that into the case at this time.

Conclusion

You have learned how to install a motherboard, the basic core of your computer system. As you can see, it’s not a hard process–certainly not brain surgery–but it’s important that you follow the steps in order.

Also, consult your documentation first before you begin the process. It will let you know if there are any jumpers that you need to set before attempting your install. These settings may vary depending on the type of motherboard that you purchased.

Learning to build your own computer is a thrilling experience. Knowing how to install computer components like a motherboard is all about laying the foundation.

Multi-core Architectures: Heterogeneous processors

PictureINTRODUCTION: A heterogeneous processor integrates a mix of “big” and “small” cores, and thus can potentially achieve the benefits of both. Several usages motivate this design:

Parallel processing: with a few big and many small cores, the processor can deliver higher performance at possibly the same or lower power than an iso-area homogeneous design.

Power savings: the processor uses small cores to save power. For example, it can operate in two modes: a high-power mode in which all cores are available and a low power mode in which applications only run on the small cores to save power at the cost of performance.

Accelerator: unlike the previous models, where the big cores have higher performance and even more features, in this model, the small cores implement special instructions, such as vector processing, which are unavailable on the big cores. Thus, applications can use the small cores as accelerators for these operations.

Heterogeneous Architectures:
(1)Design Space: We classify heterogeneous architectures into two types: performance asymmetry and functional asymmetry. The former refers to architectures where cores differ in performance (and power) due to different clock speeds, cache sizes, microarchitectures, and so forth. Applications run correctly on any core, but can have different performance.

(2)OS Challenges: there are two sets of challenges:

Correctness: OSes typically query processor features on the bootstrap processor (BSP) and assume the same for every core. This assumption becomes invalid for heterogeneous
processors. With instruction-based asymmetry, software can fail on one core but succeed on another. This needs to be handled properly to ensure correct execution.

Performance: Even when software runs correctly, obtaining high performance can be challenging. With performance asymmetry, an immediate challenge is how applications can share the high-performance cores fairly, especially when they belong to different users. OS scheduling should also enable consistent application performance across different

runs. Otherwise, a thread may execute on a fast core in one run but a slow one in another, causing performance variations. Scheduling is further complicated as threads can perform differently on different cores. In general, one would expect higher performance on a faster core; however,for I/O-bound applications, this may not be true. Choosing the right thread-to-core mappings can be challenging.

Supporting Performance Asymmetry

Quantifying CPU Performance: An essential component of our algorithms is to assign a
performance rating per CPU such that we can estimate performance differences if a thread is to run on different CPUs.There are various ways to obtain CPU ratings. Our design allows the OS to run a simple benchmark of its choice at boot time and set a default rating for each CPU. When the system is up, the OS or user can run complex benchmarks such as SPEC CPU* to override the default ratings if desired. The processor manufacturer can also provide CPU ratings, which the OS can use as the default. All of these approaches produce the same result, i.e., a static rating per CPU. If the rating of a CPU is X times higher than the rating of another CPU, we say this CPU is X times faster.

Faster-First Scheduling: If two CPUs are idle and a thread can run on both of them, we always run it on the faster CPU. The algorithm consists of two components:

Initial placement: When scheduling a thread for the first time after its creation, if two CPUs are idle, we always choose the faster one to run it. If none is idle, our algorithm has no effect and the OS performs its normal action,typically selecting the most lightly loaded CPU.

Dynamic migration: During execution, a faster CPU can become idle. If any thread is running on a slow CPU, we preempt it and move it to the faster CPU. Thus, if the total
number of threads is less than or equal to the number of faster CPUs, every thread can run on a faster CPU and achieve maximum performance.

Instruction-based Asymmetry :To emulate the accelerator usage model in Section 1, we
configure the small cores with a 2 GHz frequency, resulting in a 32% lower SPEC CPU2006* rating than the big cores.

Fault-and-migrate performance: We perform three experiments for the three instruction-asymmetry benchmarks.First, we run the non-SSE4.1 version by pinning it on a big core, which gives the performance of running on a homogeneous system of big cores without SSE4.1. Second, we run the SSE4.1 version without pinning. With faster-first scheduling, it starts on a big core; on an SSE4.1 instruction,it faults and migrates to a small core and later back to a big core. Thus, the benchmark migrates back and forth between the big and small cores, allowing us to evaluate overheads of fault-and-migrate. To evaluate the impact of T, we repeat this experiment with T equal to 1, 2, 4, and 8, where one tick in our system is 4 ms. Finally, to emulate a costly design of homogeneous big cores with SSE4 canada viagra.1, we  re-configure each small core to have equivalent performance to the big core. By pinning the SSE4.1 version of each benchmark to this core, we get an upper bound for any heterogeneous configuration with fault-and-migrate.

Conclusion :Heterogeneous architectures provide a cost-effective solution for improving both single-thread performance and multi-thread throughput. However, they also face significant challenges in the OS design, which traditionally assumes only homogeneous hardware. This paper presents a set of algorithms that allow the OS to effectively manage heterogeneous CPUs.

Our fault-and-migrate algorithm enables the OS to transparently support instruction-based asymmetry. Faster-first scheduling improves application performance by allowing them to utilize faster cores whenever possible. Finally, DWRR allows applications to fairly share CPU resources, enabling good individual application performance and system throughput. We have implemented these algorithms in Linux 2.6.24 and evaluated them on an actual heterogeneous platform. Our results demonstrated
that, with incremental changes, we can modify an existing OS to effectively manage heterogeneous hardware and achieve high performance for a wide range of applications.

What is Internet Architecture?

PictureThe Internet is a rather loose assemblage of individual networks; there is little in the way of overall administration. The individual networks are owned by a huge number of independent operators. Some of these are major corporations with large, high-capacity networks; others are private individuals operating tiny networks of two or three computers their homes. Between them these networks employ just about every networking technology yet invented. The great strength of the Internet is that it allows these diverse networks to act together to provide a single global network service.

The interactions between a network and its neighbours are, in essence, both simple and robust. This makes for easy extendibility and fuelled the early growth of the Internet. New participants needed only to come to an agreement with an existing operator and set up some fairly simple equipment to become full players. This was in great contrast to the situation within the world of telephone networks, where operators were mostly large and bureaucratic and where adding new interconnections required complex negotiation and configuration and, possibly, international treaties.

What is the Internet architecture?

It is by definition a meta-network, a constantly changing collection of thousands of individual networks intercommunicating with a common protocol. The Internet’s architecture is described in its name, a short from of the compound word “inter-networking”. This architecture is based in the very specification of the standard TCP/IP protocol, designed to connect any two networks which may be very different in internal hardware, software, and technical design. Once two networks are interconnected, communication with TCP/IP is enabled end-to-end, so that any node on the Internet has the near magical ability to communicate with any other no matter where they are. This openness of design has enabled the Internet architecture to grow to a global scale.

In practice, the Internet technical architecture looks a bit like a multi-dimensional river system, with small tributaries feeding medium-sized streams feeding large rivers. For example, an individual’s access to the Internet is often from home over a modem to a local Internet service provider who connects to a regional network connected to a national network. At the office, a desktop computer might be connected to a local area network with a company connection to a corporate Intranet connected to several national Internet service providers. In general, small local Internet service providers connect to medium-sized regional networks which connect to large national networks, which then connect to very large bandwidth networks on the Internet backbone.

Most Internet service providers have several redundant network cross-connections to other providers in order to ensure continuous availability. The companies running the Internet backbone operate very high bandwidth networks relied on by governments, corporations, large organizations, and other Internet service providers. Their technical infrastructure often includes global connections through underwater cables and satellite links to enable communication between countries and continents. As always, a larger scale introduces new phenomena: the number of packets flowing through the switches on the backbone is so large that it exhibits the kind of complex non-linear patterns usually found in natural, analogy systems like the flow of water or development of the rings of Saturn.

Each communication packet goes up the hierarchy of Internet networks as far as necessary to get to its destination network where local routing takes over to deliver it to the addressee. In the same way, each level in the hierarchy pays the next level for the bandwidth they use, and then the large backbone companies settle up with each other. Bandwidth is priced by large Internet service providers by several methods, such as at a fixed rate for constant availability of a certain number of megabits per second, or by a variety of use methods that amount to a cost per gigabyte. Due to economies of scale and efficiencies in management, bandwidth cost drops dramatically at the higher levels of the architecture.

Resources:

The network topology page provides information and resources on the real-time construction of the Internet network, including graphs and statistics.

The following references provide additional information about the Internet architecture:

Internet Architecture and Innovation

“Many people have a pragmatic attitude toward technology: they don’t care how it works, they just want to use it. With regard to the Internet, this attitude is dangerous. As this book shows, different ways of structuring the Internet result in very different environments for its development, production, and use. If left to themselves, network providers will continue to change the internal structure of the Internet in ways that are good for them, but not necessarily for the rest of us — individual, organizational or corporate Internet users, application developers and content providers, and even those who do not use the Internet.

If we want to protect the Internet’s usefulness, if we want to realize its full economic, social, cultural, and political potential, we need to understand the Internet’s structure and what will happen if that structure is changed.” The Internet’s remarkable growth has been fuelled by innovation. New applications continually enable new ways of using the Internet, and new physical networking technologies increase the range of networks over which the Internet can run. In this path breaking book, Barbara van Schewick argues that this explosion of innovation is not an accident, but a consequence of the Internet’s architecture – a consequence of technical choices regarding the Internet’s inner structure made early in its history. Building on insights from economics, management science, engineering, networking and law, van Schewick shows how alternative network architectures can create very different economic environments for innovation ou acheter du viagra.

The Internet’s original architecture was based on four design principles – modularity, layering, and two versions of the celebrated but often misunderstood end-to-end arguments. This design, van Schewick demonstrates fostered innovation in applications and allowed applications like e-mail, the World Wide Web, E-Bay, Google, Skype, Flickr, Blogger and Facebook to emerge.

Today, the Internet’s architecture is changing in ways that deviate from the Internet’s original design principles. These changes remove the features that fostered innovation in the past. They reduce the amount and quality of application innovation and limit users’ ability to use the Internet as they see fit. They threaten the Internet’s ability to spur economic growth, to improve democratic discourse, and to provide a decentralized environment for social and cultural interaction in which anyone can participate. While public interests suffer, network providers – who control the evolution of the network – benefit from the changes, making it highly unlikely that they will change course without government intervention.

Given this gap between network providers’ private interests and the public’s interests, van Schewick argues, we face an important choice. Leaving the evolution of the network to network providers will significantly reduce the Internet’s value to society. If no one intervenes, network providers’ interests will drive networks further away from the original design principles. With this dynamic, doing nothing will not preserve the status quo, let alone restore the innovative potential of the Internet. If the Internet’s value for society is to be preserved, policymakers will have to intervene and protect the features that were at the core of the Internet’s success. It is on all of us to make this happen.

What is Processor Cache?

 

There are various terms you might have heard as well as read with regards to some type of computer device. Certainly there are several you have no idea what they mean. This article is planning to talk aboutPicture the query ‘what is cache memory?’ You probably have often heard this before in relation to your internet browser when someone informs you to clear your cache.

The cache memory on a computer system is usually a tiny part of random access memory also called RAM that has been allocated to keep operations that happen to be carried out often. This element helps to speed up these types of processes as it does not have to search through the personal computer, making these kinds of actions operate faster.

Of course the more cache memory you have the faster your platform is going to run. By using much more of this memory you are able to store additional information. Nowadays the standard personal computer system comes with far more as compared to in years past.

Allow us to present additional technical terms and information as we continue the article on cache memory explained. This kind of memory is certainly termed SDRAM that is known as high speed static memory viagra prix en pharmacie paris. It is much quicker than the DRAM that is the system’s principal memory.

A lot of CPUs actually have something termed Level I (L1) ram memory built in them; they are usually from 8kb to 16kb and also used on Intel and Pentium processor chips. Newer computers normally will not have L1 cache memory, but rather have Level 2 (L2). L2 is in fact cache memory stored externally between processor chip and the specific DRAM.

Now in making points a little bit more complicated we can include on top of this that there is also a Level 3 (L3) cache memory. This circumstance is when the computer system has L1 and L2 constructed into the CPU processor and has an external chip that makes it L3.

You will also take note there is something termed disk cache. This is the portion of system RAM and is slower compared to the L1, L2 and L3. This can be used to read and write to the specific hard disk and is typically run by means of some type of software.

Finally there is something named peripheral cache memory. That is normally for a cd-rom drive as well as dvd-drive; it truly is much slower in contrast to L1, L2 and L3 and slower compared to the hard drive cache. That being said, these will be cached to the hard disk.

What and Why is Bandwidth Important?

PictureBandwidth is the measure of the amount of data that is transferred in particular time interval, usually in bits/sec. Bandwidth is the reason why an Internet user may experience a file or video to download faster from one website and the exact file to take longer to download from another website. Bandwidth also determines how fast a website takes to load. Here we look at why bandwidth is important to the Internet user and more importantly to a website owner.

To understand bandwidth, we first need to illustrate how the Internet works. The Internet is a global system of interconnecting computer networks which consists of millions of users, including you, me, local business, international business and academic institutions. The Internets network is linked via a collection of wires and optical networking cables and technologies. Bandwidth refers to the bunch of wires connecting servers to the network. Files are transferred from the servers through this network of fibres at various speeds. The speed at which data is transferred depends on the grade and quality of the wire. The higher the grade or quality the faster the speed.

As an Internet user you want to be able to access files, websites and downloads quickly. It is therefore important that you have access to the internet at an exceptional speed. Bandwidth is one factor that affects the speed in which your computer connects to the Internet. Your internet service providers, for example, may restrict or limit the bandwidth of your Internet connection especially during peak hours or if they have used their limit for the month. This limited bandwidth will consequently affect the rate at which you can access the internet.

Bandwidth also plays an important role for website owners when building their website and choosing a web hosting service. In today’s society, we live in a “I want everything now” world, where it has been proven that people want their information and answers immediately. For this reason, website owners need to make sure your website has access to higher bandwidth speeds to satisfy the visitors to your site and to also account for times when you may have a lot of visitors to your site at the same time viagra par jour. Most webhosting companies may offer various hosting packages and sometimes the different packages have restrictions on the amount of bandwidth provided. Others though may have enough servers and facilities to offer unlimited bandwidth and therefore are of greater advantage and value.

Overall, bandwidth has an important role to both the Internet user and the website owner. When choosing a reliable web hosting service, make sure you understand how much bandwidth you will be provided with and that this is adequate for your proposed website. If possible, finding a web hosting service with unlimited bandwidth is much more beneficial and saves you a lot of time and money in the future.

Types of Data Transmission Cables

PictureTwisted-Pair Cable A twisted pair cable consists of two copper conductors, each one with its own plastic insulation and twisted together. One wire carries the signal and other is used as ground reference. The advantage of twisting is that both wires are equally affected by external influences. So the unwanted signals are cancelled out as the receiver calculates the difference between signals in two wires.

This cable is of two types such as.
1- UTP (unshielded twisted pair)
2- STP (shielded twisted pair)

STP cable has one extra metal shield covering the insulated twisted pair conductors. But this is absent in UTP cables. The most common UTP connector is RJ45.

The unshielded twisted pair cable is classified into seven categories based on cable quality. Category 1 of cables is used in telephone lines with data rate around 0.1 Mbps. Whereas Category 5 used in LANs having 100 Mbps data rate.

Performance of twisted-pair cable is measured by comparing attenuation versus frequency. Attenuation increases with frequency above 100 kHz.
These cables are used in telephone lines to provide voice and data channels. DSL lines and Local area networks also use twisted pair cables.

Coaxial Cable
Coaxial cable (coax) carries high frequency signals than twisted-pair cables. Coax has a central core conductor of solid wire enclosed in an insulator, which is covered by an outer conductor of metal foil. This outer conductor completes the circuit. Outer conductor is also enclosed in an insulator, and the whole cable is protected by a plastic cover.

These cables are categorized by RG (radio government) ratings. RG-59 used for Cable TV, RG-58 for thin Ethernet and RG-11 for thick Ethernet. The connector used in these cables is called BNC connector; it is used to connect the end of the cable to a device.

.Though the coaxial cable has higher bandwidth, but its attenuation is much higher compare to twisted-pair cables. It is widely used in digital telephone networks where a single cable can carry data up to 600 Mbps. Cable TV networks use RG-59 coaxial cable. Traditional Ethernet LANs also use this cable.

Fiber-Optic Cable
A fiber optic cable transmits signals in the form of light. Optical fiber use reflection to guide light through a channel. It consists of two main parts: core and cladding. Core is denser compare to cladding and is made up of plastic or glass. Cladding acts as a protective cover to core. The difference in density of core and cladding is such that a beam of light moving through the core is reflected off the cladding, instead of being refracted into it.

Two modes of propagation of light are possible in optical fiber such as: multimode and single mode. Multimode fiber allows multiple beams from a light source move through the core. In multimode step-index fiber, the core density remains constant from the center to the edges. But in multimode graded-index fiber, core density gradually decreases from the center of the core to its edge. Graded-index fiber creates less distortion in the signal compare to step-index.

There are two types of connectors for fiber optic cables. The SC connector is used for cable TV, and ST connector used for connecting cable to networking devices. Attenuation in fiber optic cable is very low compare to other two types of cable. It provides very high bandwidth and immunity to electromagnetic interference. Light weight and greater immunity to tapping makes it more preferable cable.

Computer Servers for Dummies

PictureServers are defined as computers that are configured in such a way that they are able to provide specialized services to a specific client user or machine. They serve as task masters that manage a variety of services such as files, system jobs, network requests, and other various processes. Although they can be used for a myriad of purposes, servers primarily function as web hosting solutions.

The Wonder of Web Servers

Servers have become a very versatile solution for a variety of user needs. May it be file storage management, a network firewall, an email server, or simply as a web hosting solution, servers are the answer to almost every need. In fact, it would be very difficult to find any type of contemporary business or company that does not make use of some sort of server.

One of the biggest misconceptions about web servers is that they might be too complicated for the average Joe. The truth is, they are quite simple to manage and so long as a user has some level of technical knowledge, he should be good to go. In fact, setting up a server for one’s own website isn’t too much of a daunting task. Although it will still require a certain level of computer know-how, it is no Herculean feat at all. With a little research, some patience, and a whole lot of resourcefulness, one could very easily set up a personal server for one’s own site. This is also made possible by the fact that most server providers equip their users with easy-to-use tools to make the entire process much more user-friendly.

.The Basics Types of Web Servers

When it comes to the configuration of web hosting servers, they generally come in three different offerings. First is shared web hosting which is the most common type of web server today. This immense fame is brought about by both its affordability and simplicity. Websites that run on shared servers will (obviously) share the same IP address as well as make use of the same system resources.

The second web hosting option for users is dedicated servers. As its name implies, websites that make use of a dedicated server will have full rights and control of the whole system. Because of the fact that they do not share their servers with other websites, this also means that they will have exclusive access to all the resources of the system.

The Keys to Success

Because of websites’ growing need for more hard drive storage space and bandwidth, servers have become more and more of a requirement rather than an option. Each individual or business will have a different set of requirements and needs which means there is no one-size-fits-all sort of web hosting solution for everyone. However, the good thing is that it isn’t that difficult to set up a specific type of server that will fulfil the needs of one’s own website. Doing a little online research will definitely be helpful in this regard as there are a multitude of websites that provide information and tips on how to set up a server for all sorts of business website.