Virtualization, Grid & Cloud Computing - Basics

Virtualization

You maybe know a little about virtualization if you have ever use a software to allow a piece of hardware to run multiple operating system images at the same time. A large cluster of servers does not essentially constitute a grid. In order to manage those resources, virtualization is required so that resources are aggregated, and expanded or pulled back as the computational, storage, or bandwidth requirements of applications change. Virtualization can be performed at three levels:
Network virtualization is a technique of combining the existing resources in a network by splitting up the available bandwidth into channels, each of which is independent from the others, and each of which can be assigned (or reassigned) to a particular server or device in real time. The idea is that virtualization hides the factual complexity of the network by separating it into manageable parts, much like your partitioned hard drive makes it easier to manage your files.
Server virtualization uses software that allows a server to be logically partitioned so that applications have a dedicated space in which to execute. The partitions and underlying resources are constantly balanced, based on the requirements of applications running on it. The purpose is to spare the user from having to understand and manage complicated details of server resources while increasing resource sharing and utilization and maintaining the capacity to expand later.
Storage virtualization is the pooling of physical storage from multiple network storage devices into what appears to be a single storage device that is managed from a central console.

Grid Computing

When hundreds or thousands of servers are clustered and managed as a single massive computing resource, the processing power available for use is enormous. Grid computing is the act of sharing tasks over multiple computers. Tasks can range from data storage to complex calculations and can be spread over large geographical distances. Grids are often constructed with the aid of general-purpose grid software libraries known as middleware. Grids allow customers to pay only for the processing capability, storage, and network bandwidth they use.
Grid computing can be thought of as distributed and large-scale cluster computing and as a form of network-distributed parallel processing. Grid computing is similar to cluster computing, but there are a number of distinct differences. In a grid, there is no centralized management; computers in the grid are independently controlled, and can perform tasks unrelated to the grid at the operator's discretion. The computers in a grid are not required to have the same operating system or hardware. Grids are also usually loosely connected, often in a decentralized network, rather than contained in a single location, as computers in a cluster often are.

Cloud computing

If you have an e-mail account with a Web-based e-mail service like Hotmail, Yahoo! Mail or Gmail, then you've had some experience with cloud computing. Instead of running an e-mail program on your computer, you log in to a Web e-mail account. The software and storage for your account doesn't exist on your computer, it's on the service's computer cloud. Cloud computing is closely related to grid computing. Cloud computing requires that a grid already be established because the foundation of a cloud computing environment is a grid. Clouds have the same operational necessities and customer expectations as grids, with regard to security, data protection, isolation, performance, and availability. In a grid computing system, networked computers are able to access and use the resources of every other computer on the network. In cloud computing systems, that usually only applies to the back end. Rather than having a focus on platform middleware, server hardware, network and storage resources, cloud computing is the offering of services without exposing the grid and how it is managed.

User-Agent Spoofing

Sometimes, you might encounter problem of accessing a website, just because the web server doesn’t recognize or allow that web browser (client program) you used to access the site. Some of you might recall Google Chrome version earlier than 0.4.154.33 encountered problem with Windows Live Mail (a.k.a. hotmail), as the Microsoft free webmail system didn’t properly recognize this. User-Agent spoofer/switcher extension/addons allows users to access sites which lock contents to certain browsers .

Fix It For Firefox:

The User Agent Switcher addon adds a menu and a toolbar button to switch the user agent of the browser. The typical usage is to allow access to sites that restrict access based on the browser being used. To switch the user agent of the browser select a user agent in the ‘User Agent Switcher’ menu under the ‘Tools’ menu of the browser. To customize the list of user agents select ‘Edit User Agents…’ under the ‘User Agent Switcher’ menu.

Download User Agent Switcher Extension from here https://addons.mozilla.org/en-US/firefox/addon/59/

Alternate Method:
1. Open Firefox web browser, type about:config in the address bar and press ENTER.
2. You might see some text titled “Here be dragons!”, just click the only button to proceed. Now, you should see a page of Firefox settings (known as Preference). Right click on the page, select New follow by String.
3. In the New String Value dialog box, enter the preference name general.useragent.override and click OK.
4. The next dialog box appears, this time prompt for a value for the Preference name defined in previous step – enter the user agent string of your choice here:

Now, you should close all the Firefox windows. Upon reopen, the new user agent string specified in general.useragent.override should be effective. To verify it, type about: in the address bar and press enter.

Fix It For Chrome:

Chromeleon is a user agent switcher extension for Google chrome. This extension allows users to change the user agent string passed by Chrome to mock any browser they wish. This user-agent spoofer extension allows Chrome users to access sites which lock contents to certain browsers or intentionally block chrome. Also you can set a specific filtering list, so that Chromeleon will automatically switch user-agent strings based on the domain or URL specified.

Features of Chromeleon User agent Switcher extension: One click Useragent changer, Can add specific URL filter list, Add custom user agent strings

Only problem with this extension is that it does not modify HTTP headers, so sites which sniff useragents at network level could see through the spoofing.

Download Chromeleon Extension from here https://chrome.google.com/extensions/detail/aafciojnlamllgpkpdkbamkfgbofhgcj

Alternate Method:
1. Chrome browser spoofing could also be done from command line without installing the extension.
2. Create a new shortcut for chrome and add –user-agent=”custom string” to the target of this shortcut [e.g. C:\Users\XXXX\AppData\Local\Google\Chrome\Application\chrome.exe --user-agent="Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) ; .NET CLR 3.5.30729)" ].
3. Now run chrome using this shortcut.

Virtual Private Networks

VPN (Virtual Private Networks) gives enormously secure connections between private networks linked through the Internet. It allows remote computers to act as though they were on the same secure, local network. VPNs enable file sharing, video conferencing and similar network services. Virtual private networks generally don’t provide any new functionality that isn’t already offered through alternative mechanisms, but a VPN implements those services more efficiently / cheaply in most cases. The VPN can be found in workplaces and homes, where they allow employees to safely log into company networks. Telecommuters and those who travel often find a VPN a more suitable way to stay connected to the corporate intranet. No matter your current involvement with VPNs, this is a good technology to know something about. So here it goes…

Imagine thousands of islands in a huge ocean, some are very close to each other and some are very far. The regular way to travel from one island to another is to take a boat from one island to another. Of course, traveling on a boat means that you have almost no privacy. Anything you do can be seen by someone else. We can assume each island as a private LAN and the ocean is the Internet. Traveling by boat is like connecting to a other LAN through the Internet. We have no control over the wires and routers that make up the Internet.

Now suppose an island has a bridge to another island so that there is easier, more secure and direct way for people to travel between the two. It is expensive to build and maintain the bridge, even though the island you are connecting with is very close. But the need for a reliable, secure path is so great that you have to do it anyway. This is very much like having a leased line. The bridges (leased lines) are separate from the ocean (Internet), yet are able to connect the islands (LANs). Many companies have chosen this route because of the need for security and reliability in connecting their remote offices. However, if the offices are very far apart, the cost can be prohibitively high -just like trying to build a bridge that spans a great distance.

Now suppose each resident of an island has a small submarine with some amazing properties. It’s fast, It’s easy to take with you wherever you go, It’s able to completely hide you from any other boats or submarines. Although residents are traveling in the ocean along with other traffic, they could travel back and forth whenever they wanted to with privacy and security. That’s essentially how a VPN works. Each remote member of network can communicate in a secure and reliable manner using the Internet as the medium to connect to the private LAN. A VPN can grow to accommodate more users and different locations much easier than a leased line. In fact, scalability is a major advantage that VPNs have over typical leased lines. Unlike with leased lines, where the cost increases in proportion to the distances involved, the geographic locations of each office matter little in the creation of a VPN.

Advantages Of VPN
1. Allows you to be at home and access your company’s computers in the same way as if you were sitting at work.
2. Almost impossible for someone to tap or interfer with data in the VPN tunnel.
3. If you have VPN client software on a laptop, you can connect to your company from anywhere in the world.

Google Talk in Firefox Sidebar

We all are regular user of google chat service. To use this service either we use the stand-alone G- Talk desktop client or the floating AJAX version in Gmail. But i feel that Google Talk Gadget is more usable than both of them. Here, each chat session opens up as a tab (like tabs are open in Firefox browser). It can show previews of images or video and the chat client can easily be embedded inside WebPages.

Problem With It: The webpage (like the Google personalized page) where we have embedded the G-Talk gadget must be in front of us all the time.
Solution: Put the Google Talk client in the Firefox sidebar so it always stays in the foreground no matter what website you are on currently.

To add Google Talk to your Firefox sidebar follow these steps.

1. Bookmark the following URL http://talkgadget.google.com/talkgadget/client
2. Now goto Bookmarks menu, navigate to the above bookmark, right click on it and choose Properties. click the checkbox that says “Load this bookmark in the sidebar“.
3. Now go to View->Sidebar->Bookmarks and click on this bookmark. You are done now.

Most of the corporate offices, colleges block gtalk along with other messengers. With this trick, you’ll be able to access google talk, MSN, Yahoo and ICQ messengers in the offices, schools or any other places where these messengers are blocked for use.

Network Address Translation (NAT)

For a computer to communicate with other computers, it must have an IP address. With the explosion of the Internet and the increase in home networks and business networks, the number of available IP addresses is simply not enough. The obvious solution is to redesign the address format to allow for more addresses IPv6 but will take several years to implement because it requires modification of the entire infrastructure of the Internet. Network Address Translation (NAT) allows a single device, such as a router, to act as agent between the Internet (public network) and a local (private) network. This means that only a single unique IP address is required to represent an entire group of computers to outside their network.

Reasons to use NAT:
1. Shortage of IP addresses
2. Security and Administration

How NAT Works

Suppose an inside host (192.168.65.29) wants to communicate with an google server (209.85.231.104). It sends a packet to the NAT-configured router. The router reads the source IP address of the packet and checks if the packet matches the criteria specified for translation. The router has an ACL (Access Control List) that identifies the inside network as valid hosts for translation. Therefore, it translates an inside local IP address ( 192.168.65.29) into inside global IP address( 117.240.114.18). It stores this translated local to global address in the NAT table. The router then sends the packet to its destination.

When the google server responds back, the packet comes back to the router (117.240.114.18). The router looks its NAT table and finds it as previously translated IP address. Then, it translates the inside global address (117.240.114.18) to the inside local address (192.168.65.29), and the packet is forwarded to host at IP address 192.168.65.29. If it does not find a translation that match, the packet is dropped.

NOTE:
NAT is sometimes confused with proxy servers but they are different. In NAT neither one realizes that it is dealing with a third device, but in proxy server source computer knows that it is making a request to the proxy server and must be configured to do so. The destination computer thinks that the proxy server is the source computer and deals with it directly. Also, proxy servers usually work at Layer 4 (Transport) of the OSI Reference Model or higher, while NAT is a Layer 3 (Network) protocol. Working at a higher layer makes proxy servers slower than NAT devices in most cases.

Types Of NATing
Static NAT: Mapping an local IP address to a external IP address on a one-to-one basis.
Dynamic NAT: Maps an local IP address to a external IP address from a group of external IP addresses.


NAT Overloading: Maps multiple local IP addresses to a single external IP address by using different ports. Also known also as PAT (Port Address Translation).
In overloading, each computer on the local network (like 192.168.65.29, 192.168.65,101 etc.) is translated to the same IP address (117.240.114.18) but with a different port number.

NAT Overlapping: Maps an external IP address to another external IP address.

Run Torrent Behind Proxy And Firewall

Dedicated to my juniors who ask me many times that “How to run Torrent behind proxy n firewall??” or “Sir please unblock Torrent over institue lan.”

Torrents is preferred means of downloads. Use of BitTorrent is not possible on some networks (e.g. institute or office lan). In this post am going to tell you a easy solution to overcome this problem. By using a secure connection (SSH), you can bypass almost every firewall. Linux or a UNIX-based OS terminal supports SSH. For Windows, you have to download SSH clients. There are may SSH clients, but PUTTY is (probably) the best and certainly the most popular. For this hack you need a SSH account. You can try one of these free shell providers from this list . So here it goes….

Steps:

1. Run putty and In the address box, put the hostname or IP address of the server you have an SSH account on. Make sure the SSH radio button or check-box is ticked, and be sure you’re using port 22.
2. In the menu, click on Proxy tab under Connections and put your proxy settings there.
3. In the menu, click on SSH and select enable compression. this will compress the traffic thru your SSH tunnel, which not only provides a modest improvement in transfer rates, but has some minor security benefits as well. Set your preferred protocol to “2″, or “2 only”.
4. Click on the tunnels menu under SSH. At the bottom, select the dynamic button, and enter a source port. Use any port (greater than 1024 like 4567). Click the “add” button.
5. Go back to the session tab in the menu, enter in a title for this proxy, and click save.
6. Now Configure your BitTorrent client. In uTorrent go to Options > Preferences > Connection. Enter your port number (which u use earlier like 4567), socks 4 or 5 as type, and localhost in the proxy field. Socks5 is preferable to version four, and supported by our SSH tunnel, so select it. Click OK, and you should now be proxying thru the server with the SSH account.

You’re done, restart your BitTorrent client and you’re ready to go. BitTorrent over SSH tends to be a bit slower than your normal connection, but it’s a great solution when BitTorrent connections are blocked.

Customize start menu button: Windows 7

Have you ever wondered how to customize the start menu button in Windows 7? Well it is possible to spice up your copy of Windows 7 by giving a new look to the start menu button. In order to make the changes, the file explorer.exe located at C:\Windows needs to be edited. Since explorer.exe is a binary file it requires a binary editor. Resource HackerTM is a freeware utility and works on Win95, Win98, WinME, WinNT, Win2000 and WinXP, Vista and Windows7 operating systems.

Requirements

1. Resource Hacker: A Binary File Editor
2. Custom Start Menu Images: You nees three images that must be of the size 54×162 with a .bmp extension.

1st Image – For idle state
2nd Image – For mouse over
3rd Image – When button is clicked

Process:

1. Run Resource Hacker Editor.
2. Go to File menu and Open file “explorer.exe” into the Resource Hacker.
3. Go to Bitmap branch, expand 6801 option, right-click on 1033 and select Replace Resource option.
4. A new window appears. Click on Open file with new bitmap button.
5. Navigate to the customized (.bmp) image, open it and click on Replace button.
6. Repeat steps 3 to 5 above for the options 6805 and 6809 as well.
7. Now save the file. Resource Hacker will automatically create a backup file called explorer_original.exe so that you can restore it in the future if needed. Restart your computer and have fun.

Download Resource Hacker Tool from http://www.angusj.com/resourcehacker/