Showing posts with label Little Tips. Show all posts
Showing posts with label Little Tips. Show all posts

Aug 15, 2011

HTTP Status codes explained

Different Types of HTTP Status Codes

What is an HTTP status code and why should you care about them, if you have a website or a blog?

Whenever you enter the address of a webpage in your browser’s address bar, the browser requests data from the server where the page is originally hosted. The web server returns the data but before the browser receives and renders the data at the clients end, an HTTP header is returned by the web server that has the status code of the given page.

In general, HTTP status codes are not meant for human visitors but both desktop and mobile browsers use this information to know more about the present condition of the webpage in question. If the page is in a healthy state, the HTTP status code returned should be a 200 OK. If the page has been moved to a new address, the HTTP status code should be 301 and so on.

There are lots of different HTTP status codes in place and the following table should explain what are the different types of HTTP header responses and their purpose in brief detail:

HTTP Status code Type Description Link Juice




Redirected
300 Redirection The server is waiting for an action from the user so that it can fetch a new resource Depends
301* Redirected The old page has permanently moved to a new web address Carried
302 Redirected The old page has temporary moved to a new location but the user should continue using the old URL later Not carried
303 Conditional redirection The user is requested to do some action (GET request) so that the current page may redirect to another resource. The GET request
is conditional. Not carried

304 Conditional redirection The user has performed some action (conditional GET request) but the current page was not modified. Not carried
305 Redirected The user can only access the requested page using a proxy. Not carried
306 Redirected The server is fetching the page from another location but it will soon fetch the page from its older source. This status code is rarely used over a 302. Not carried
Successful
200 ** Success The server has processed the webpage correctly. Carried
201 Success The server has processed the requested page and created a new page or resource during the request. Depends
202 Partial success The server has received the request for the webpage and is currently processing it. Carried
203 Partial success The server has received the request for the webpage and it is waiting for a resource from another page. Carried
204 Partial success The server processed the request for the webpage but no content has been returned due to an error. Carried
205 Partial success Same as 204 but this time the server is waiting for the user to complete a specific action. Carried
206 partial Success The server received a partial GET request from the user. Carried




Request Errors
400 Fail Wrong syntax sent by the user Not carried
401 Authentication required The page is behind a login and/or requires an authentication from the user. Not carried
403 *** Forbidden The server denied the request. Not carried
404 Page does not exist The requested page is not found on the server. Not carried
405 Not allowed The server is not allowing any request to the page for this user. Not carried
406 Not allowed The server can’t respond to the request at this time. Not carried
407 Proxy required The resource must be requested via a proxy. Not carried
408 Timed out The server timed out performing the request. Not carried
409 Conflict The user’s action has given rise to a conflict of resource. Not carried
410 # Permanently removed The page has been permanently removed from the server. Not carried




Server Errors
500 Internal Server error The server is facing issues with some internal configuration and thus unable to fulfill the request at this time Not carried
501 Not recognized The server is not equipped to understand the type of request sent Not carried
502 Bad gateway While fulfilling the current request, the server received an incorrect response from its upstream server Not carried
503 Server not available The server is facing downtime or is currently unavailable Not carried
504 Gateway timeout The server is acting as a gateway or a proxy server to another resource and didnt received a timely request from the user Not carried
505 Server does not support protocol The server is not configured to support the HTTP protocol version that is used in the request Not carried


* This is the only way to tell search engines that your old page has moved to a new location and the newer URL should be re-crawled and re-indexed. Only this server header preserves link juice and Google Pagerank but remember that if the page is part of a redirect chain, a considerable portion of the PR may be lost overtime.

** This should be normally the HTTP status code returned by a webpage if it’s static in nature and needs no GET request from the user.

*** If any of your pages return a 403 HTTP status code, it means that your web server denied the request of the page to Googlebot and human visitors. A possible case is when your web host is facing downtimes or it is blocking spiders and search bots from accessing some parts of your website, so you should be careful about it.

# This is similar to a 404 error but the standard practice is to 301 redirect the missing page to it’s newer location. If the page has no new location, it is recommended to return a 410. If you have temporarily removed the page from the server, use a 503 instead.

Apr 16, 2009

Computer Networks Interview Questions

Computer Networks Interview Questions

1. What are 10Base2, 10Base5 and 10BaseT Ethernet LANs

10Base2—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with a contiguous cable segment length of 100
meters and a maximum of 2 segments.
10Base5—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with 5 continuous segments not exceeding 100
meters per segment.
10BaseT—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling and twisted pair cabling.

2. What is the difference between an unspecified passive open and a fully specified passive open

An unspecified passive open has the server waiting for a connection request from a client. A fully specified passive open has the server waiting for a connection from a
specific client.

3. Explain the function of Transmission Control Block
A TCB is a complex data structure that contains a considerable amount of information about each connection.

4. What is a Management Information Base (MIB)

A Management Information Base is part of every SNMP-managed device. Each SNMP agent has the MIB database that contains information about the device's status, its
performance, connections, and configuration. The MIB is queried by SNMP.

5. What is anonymous FTP and why would you use it

Anonymous FTP enables users to connect to a host without using a valid login and password. Usually, anonymous FTP uses a login called anonymous or guest, with the
password usually requesting the user's ID for tracking purposes only. Anonymous FTP is used to enable a large number of users to access files on the host without having
to go to the trouble of setting up logins for them all. Anonymous FTP systems usually have strict controls over the areas an anonymous user can access.

6. What is a pseudo tty

A pseudo tty or false terminal enables external machines to connect through Telnet or rlogin. Without a pseudo tty, no connection can take place.

7. What is REX

What advantage does REX offer other similar utilities

8. What does the Mount protocol do

The Mount protocol returns a file handle and the name of the file system in which a requested file resides. The message is sent to the client from the server after reception
of a client's request.

9. What is External Data Representation

External Data Representation is a method of encoding data within an RPC message, used to ensure that the data is not system-dependent.

10. What is the Network Time Protocol ?

11. BOOTP helps a diskless workstation boot. How does it get a message to the network looking for its IP address and the location of its operating system boot files
BOOTP sends a UDP message with a subnetwork broadcast address and waits for a reply from a server that gives it the IP address. The same message might contain the
name of the machine that has the boot files on it. If the boot image location is not specified, the workstation sends another UDP message to query the server.

12. What is a DNS resource record

A resource record is an entry in a name server's database. There are several types of resource records used, including name-to-address resolution information. Resource
records are maintained as ASCII files.

13. What protocol is used by DNS name servers

DNS uses UDP for communication between servers. It is a better choice than TCP because of the improved speed a connectionless protocol offers. Of course,
transmission reliability suffers with UDP.

14. What is the difference between interior and exterior neighbor gateways

Interior gateways connect LANs of one organization, whereas exterior gateways connect the organization to the outside world.

15. What is the HELLO protocol used for

The HELLO protocol uses time instead of distance to determine optimal routing. It is an alternative to the Routing Information Protocol.

16. What are the advantages and disadvantages of the three types of routing tables

The three types of routing tables are fixed, dynamic, and fixed central. The fixed table must be manually modified every time there is a change. A dynamic table changes its information based on network traffic, reducing the amount of manual maintenance. A fixed central table lets a manager modify only one table, which is then read by other devices. The fixed central table reduces the need to update each machine's table, as with the fixed table. Usually a dynamic table causes the fewest problems for a network administrator, although the table's contents can change without the administrator being aware of the change.

17. What is a TCP connection table

18. What is source route

It is a sequence of IP addresses identifying the route a datagram must follow. A source route may optionally be included in an IP datagram header.

19. What is RIP (Routing Information Protocol)

It is a simple protocol used to exchange information between the routers.

20. What is SLIP (Serial Line Interface Protocol)

It is a very simple protocol used for transmission of IP datagrams across a serial line.

21. What is Proxy ARP

It is using a router to answer ARP requests. This will be done when the originating host believes that a destination is local, when in fact is lies beyond router.

22. What is OSPF

It is an Internet routing protocol that scales well, can route traffic along multiple paths, and uses knowledge of an Internet's topology to make accurate routing decisions.

23. What is Kerberos

It is an authentication service developed at the Massachusetts Institute of Technology. Kerberos uses encryption to prevent intruders from discovering passwords and
gaining unauthorized access to files.

24. What is a Multi-homed Host

It is a host that has a multiple network interfaces and that requires multiple IP addresses is called as a Multi-homed
Host.

25. What is NVT (Network Virtual Terminal)

It is a set of rules defining a very simple virtual terminal interaction. The NVT is used in the start of a Telnet session.

26. What is Gateway-to-Gateway protocol

It is a protocol formerly used to exchange routing information between Internet core routers.

27. What is BGP (Border Gateway Protocol)

It is a protocol used to advertise the set of networks that can be reached with in an autonomous system. BGP enables this information to be shared with the autonomous
system. This is newer than EGP (Exterior Gateway Protocol).

28. What is autonomous system

It is a collection of routers under the control of a single administrative authority and that uses a common Interior Gateway Protocol.

29. What is EGP (Exterior Gateway Protocol)

It is the protocol the routers in neighboring autonomous systems use to identify the set of networks that can be reached within or via each autonomous system.

30. What is IGP (Interior Gateway Protocol)

It is any routing protocol used within an autonomous system.

31. What is Mail Gateway

It is a system that performs a protocol translation between different electronic mail delivery protocols.

32. What is wide-mouth frog

Wide-mouth frog is the simplest known key distribution center (KDC) authentication protocol.

33. What are Digrams and Trigrams

The most common two letter combinations are called as digrams. e.g. th, in, er, re and an. The most common three letter combinations are called as trigrams. e.g. the, ing, and, and ion.

34. What is silly window syndrome

It is a problem that can ruin TCP performance. This problem occurs when data are passed to the sending TCP entity in large blocks, but an interactive application on the receiving side reads 1 byte at a time.

35. What is region

When hierarchical routing is used, the routers are divided into what we call regions, with each router knowing all the details about how to route packets to destinations within its own region, but knowing nothing about the internal structure of other regions.

36. What is multicast routing

Sending a message to a group is called multicasting, and its routing algorithm is called multicast routing.

37. What is traffic shaping

One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a uniform rate, congestion would be less common. Another open loop
method to help manage congestion is forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.

38. What is packet filter

Packet filter is a standard router equipped with some extra functionality. The extra functionality allows every incoming or outgoing packet to be inspected. Packets meeting
some criterion are forwarded normally. Those that fail the test are dropped.

39. What is virtual path

Along any transmission path from a given source to a given destination, a group of virtual circuits can be grouped together into what is called path.

40. What is virtual channel

Virtual channel is normally a connection from one source to one destination, although multicast connections are also permitted. The other name for virtual channel is virtual circuit.

41. What is logical link control

One of two sublayers of the data link layer of OSI reference model, as defined by the IEEE 802 standard. This sublayer is responsible for maintaining the link between computers when they are sending data across the physical network connection.

42. Why should you care about the OSI Reference Model

It provides a framework for discussing network operations and design.

43. What is the difference between routable and non- routable protocols

Routable protocols can work with a router and can be used to build large networks. Non-Routable protocols are designed to work on small, local networks and cannot be used with a router

44. What is MAU

In token Ring , hub is called Multistation Access Unit(MAU).

45. Explain 5-4-3 rule

In a Ethernet network, between any two points on the network, there can be no more than five network segments or four repeaters, and of those five segments only three of segments can be populated.

46. What is the difference between TFTP and FTP application layer protocols

The Trivial File Transfer Protocol (TFTP) allows a local host to obtain files from a remote host but does not provide reliability or security. It uses the fundamental packet delivery services offered by UDP. The File Transfer Protocol (FTP) is the standard mechanism provided by TCP / IP for copying a file from one host to another. It uses the services offered by TCP and so is reliable and secure. It establishes two connections (virtual circuits) between the hosts, one for data transfer and another for control information.

47. What is the range of addresses in the classes of internet addresses

Class A 0.0.0.0 - 127.255.255.255
Class B 128.0.0.0 - 191.255.255.255
Class C 192.0.0.0 - 223.255.255.255
Class D 224.0.0.0 - 239.255.255.255
Class E 240.0.0.0 - 247.255.255.255

48. What is the minimum and maximum length of the header in the TCP segment and IP datagram

The header should have a minimum length of 20 bytes and can have a maximum length of 60 bytes.

49. What is difference between ARP and RARP

The address resolution protocol (ARP) is used to associate the 32 bit IP address with the 48 bit physical address, used by a host or a router to find the physical address of another host on its network by sending a ARP query packet that includes the IP address of the receiver. The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.

50. What is ICMP

ICMP is Internet Control Message Protocol, a network layer protocol of the TCP/IP suite used by hosts and gateways to send notification of datagram problems back to the sender. It uses the echo test / reply to test whether a destination is reachable and responding. It also handles both control and error messages.

51. What are the data units at different layers of the TCP / IP protocol suite

The data unit created at the application layer is called a message, at the transport layer the data unit created is called either a segment or an user datagram, at the network layer the data unit created is called the datagram, at the data link layer the datagram is encapsulated in to a frame and finally transmitted as signals along the transmission media.

52. What is Project 802

It is a project started by IEEE to set standards that enable intercommunication between equipment from a variety of manufacturers. It is a way for specifying functions of the physical layer, the data link layer and to some extent the network layer to allow for interconnectivity of major LAN protocols.
It consists of the following: 802.1 is an internetworking standard for compatibility of different LANs and MANs across protocols. 802.2 Logical link control (LLC) is the upper sublayer of the data link layer which is non-architecture-specific, that is remains the same for all IEEE-defined LANs. Media access control (MAC) is the lower sublayer of the data link layer that contains some distinct modules each carrying proprietary information specific to the LAN product
being used. The modules are Ethernet LAN (802.3), Token ring LAN (802.4), Token bus LAN (802.5). 802.6 is distributed queue dual bus (DQDB) designed to be used in MANs.

53. What is Bandwidth

Every line has an upper limit and a lower limit on the frequency of signals it can carry. This limited range is called the bandwidth.

54. Difference between bit rate and baud rate.

Bit rate is the number of bits transmitted during one second whereas baud rate refers to the number of signal units per second that are required to represent
those bits. baud rate = bit rate / N
where N is no-of-bits represented by each signal shift.

55. What is MAC address

The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.

56. What is attenuation

The degeneration of a signal over distance on a network cable is called attenuation.

57. What is cladding

A layer of a glass surrounding the center fiber of glass inside a fiber-optic cable.

58. What is RAID

A method for providing fault tolerance by using multiple hard disk drives.

59. What is NETBIOS and NETBEUI
NETBIOS is a programming interface that allows I/O requests to be sent to and received from a remote computer and it hides the networking hardware from applications. NETBEUI is NetBIOS extended user interface. A transport protocol designed by microsoft and IBM for the use on small subnets.

60. What is redirector

Redirector is software that intercepts file or prints I/O requests and translates them into network requests. This comes under presentation layer.

61. What is Beaconing

The process that allows a network to self-repair networks problems. The stations on the network notify the other stations on the ring when they are not receiving the transmissions. Beaconing is used in Token ring and FDDI networks.

62. What is terminal emulation, in which layer it comes

Telnet is also called as terminal emulation. It belongs to application layer.

63. What is frame relay, in which layer it comes

Frame relay is a packet switching technology. It will operate in the data link layer.

64. What do you meant by "triple X" in Networks

The function of PAD (Packet Assembler Disassembler) is described in a document known as X.3. The standard protocol has been defined between the terminal and the PAD, called X.28; another standard protocol exists between hte PAD and the network, called X.29. Together, these three recommendations are often called "triple X"

65. What is SAP

Series of interface points that allow other computers to communicate with the other layers of network protocol stack.

66. What is subnet

A generic term for section of a large networks usually separated by a bridge or router.

67. What is Brouter

Hybrid devices that combine the features of both bridges and routers.

68. How Gateway is different from Routers

A gateway operates at the upper levels of the OSI model and translates information between two completely different network architectures or data formats.

69. What are the different type of networking / internetworking devices

Repeater: Also called a regenerator, it is an electronic device that operates only at physical layer. It receives the signal in the network before it becomes weak, regenerates the original bit pattern and puts the refreshed copy back in to the link.
Bridges: These operate both in the physical and data link layers of LANs of same type. They divide a larger network in to smaller segments. They contain logic that allow them to keep the traffic for each segment separate and thus are repeaters that relay a frame only the side of the segment containing the intended recipent and control congestion.
Routers: They relay packets among multiple interconnected networks (i.e. LANs of different type). They operate in the physical, data link and network layers. They contain software that enable them to determine which of the several possible paths is the best for a particular transmission. Gateways:
They relay packets among networks that have different protocols (e.g. between a LAN and a WAN). They accept a packet formatted for one protocol and convert it to a packet formatted for another protocol before forwarding it. They operate in all seven layers of the OSI model.

70. What is mesh network

A network in which there are multiple network links between computers to provide multiple paths for data to travel.

71. What is passive topology

When the computers on the network simply listen and receive the signal, they are referred to as passive because they don’t amplify the signal in any way. Example for passive topology - linear bus.

72. What are the important topologies for networks

BUS topology:
In this each computer is directly connected to primary network cable in a single line. Advantages:
Inexpensive, easy to install, simple to understand, easy to extend. STAR topology:
In this all computers are connected using a central hub.

Advantages:

Can be inexpensive, easy to install and reconfigure and easy to trouble shoot physical problems. RING topology:
In this all computers are connected in loop.
Advantages:
All computers have equal access to network media, installation can be simple, and signal does not degrade as much as in other topologies because each computer
regenerates it.

73. What are major types of networks and explain

Server-based network
Peer-to-peer network
Peer-to-peer network, computers can act as both servers sharing resources and as clients using the resources. Server-based networks provide centralized control of network resources and rely on server computers to provide security and network administration

74. What is Protocol Data Unit

The data unit in the LLC level is called the protocol data unit (PDU). The PDU contains of four fields a destination service access point (DSAP), a source service access point (SSAP), a control field and an information field. DSAP, SSAP are addresses used by the LLC to identify the protocol stacks on the receiving and sending machines that are generating and using the data. The control field specifies whether the PDU frame is a information frame (I frame) or a supervisory frame (S - frame) or a unnumbered frame (U - frame).

75. What is difference between baseband and broadband transmission

In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal. In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.

76. What are the possible ways of data exchange

(i) Simplex (ii) Half-duplex (iii) Full-duplex.

77. What are the types of Transmission media

Signals are usually transmitted over some transmission media that are broadly classified in to two categories. Guided Media:
These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light. Unguided Media:
This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony.

78. What is point-to-point protocol

A communications protocol used to connect computers to remote networking services including Internet service providers.

79. What are the two types of transmission technology available

(i) Broadcast and (ii) point-to-point

80. Difference between the communication and transmission.

Transmission is a physical movement of information and concern issues like bit polarity, synchronization, clock etc. Communication means the meaning full exchange of information between two communication media.

PC Hardware Troubleshooting Tips

PC Hardware Troubleshooting Tips

First, of course, you need to check the stupid stuff. You'd probably be amazed how many "problems" are solved by connecting the cables, or turning on the power switch that you swear you just did. Beyond that, double-check the snugness of your connections—jiggling in a new add-in card or screwing in a cable connection can (and often does) make a difference. You may even want to check the integrity of your cables and connectors. I once solved a baffling SCSI problem by noticing that one of the pins in a miniature 50-pin SCSI-II connector was bent. I had mistakenly presumed, prior to that, that a bent pin would have prevented me from making a connection at all, but it didn't. Unfortunately, as a result, I wasted several hours on something that could've taken two minutes.

Finally, whenever you install something new, whether it's more memory, a new drive, a plug-in card or what-have-you, and something doesn't work, it's more than likely because you made a mistake somewhere in the installation process. Step back through the process again, double- and triple-check your connections, and then try one more time. In the case of RAM that doesn't work or isn't recognized, it could be an incompatibility with the specific manufacturer of the RAM and your motherboard, so see if you can try a different brand before you give up hope. Finally, in some instances installing something new causes a conflict with something else--which is what the rest of this article is all about.

Driver Dilemmas

Once you're past the basics, it’s on to step two. As long as your computer boots, then there's a good chance the problem is related to missing, damaged, incompatible or improperly installed driver software, otherwise known simply as drivers. (If your PC doesn't start up, you may want to create a boot floppy disk—see "How to Create a 'Real' Windows 95 (or 98 or ME) Boot Disk" for more. In addition, you should check out the "PC Startup Troubleshooting Tips" article for more.)

Virtually every piece of hardware located inside or connected externally to your PC requires a driver to communicate and function with the operating system, applications, and other hardware components in your machine. Drivers essentially translate messages back and forth between the hardware in question and the operating system, thereby allowing your computer system to work as a unified whole (at least, in theory). The truth is, though appearances may suggest otherwise, any computer system is actually made up of a bunch of specialized pieces that don't speak the "native language" of other components and, therefore, require a great deal of translation to communicate and work effectively with them. When any of these various levels of translation break down, well, that's when you get problems.

The Device Manager is Your Friend

If you're running Windows 95, 98, or ME, your first stop after the computer finishes the startup process should be the Device Manager, a piece of operating system software that helps you manage the various pieces of your PC. You can get to the Device Manager in several different ways: the two easiest are right-clicking on the My Computer icon on your desktop and selecting Properties from the context menu that pops up when you do this, or by going to the Start menu, going up to Settings, selecting Control Panel from the list of choices and then double-clicking on the System control panel. Either way, you’ll be presented with a tabbed dialog box; click on the tab that says Device Manager, and you’re there.

The first thing to look for is a yellow exclamation point or red international no sign (you know, the circle with the slash through it) next to one of your devices. You may need to click on all the little plus signs next to each category of devices to see the full outline-like list of everything in your computer. If you see the yellow or red symbol, you know something is amiss. My first suggestion is to highlight the offending device and click on the Remove button. What this does is essentially erase the driver software associated with the device as well as references to it within the Windows 95/98/ME Registry. (The Registry tracks all the hardware and software you install, the preferences you set for each, as well as lots of other stuff). The fancy term for this is "logically" removing the device because, even though it may still be physically attached, the computer no longer has any record of its presence.

Next, you should restart your computer, let Windows' Plug-and-Play feature "find" the device again, and redo the driver installation process by either using the driver suggestions that Windows finds and makes or clicking on the Have Disk button and using the installer disks that came with the device. (If both options are possible, I’d go with the disks that came with the hardware—unless you’re sure they are an older version.) If the computer doesn’t find the device, then I would suspect the connections or the device itself. Buy another cable, unplug and re-plug the connectors, remove and then physically reinstall any new plug-in cards or do whatever you have to to ensure that the connection is solid. Once you’ve done that, you’ll find that many times, simply reinstalling the drivers solves the problem.

Other times the problem is due to an older version of a driver conflicting with something else on your system. It’s always a good idea to check for and get the latest versions of drivers that your PC needs. Check the manufacturer’s web site first and if you can’t find the driver, or drivers, there (or if the company is no longer in business), try searching for it at one of the web’s driver repositories, such as The Driver Zone, WinDrivers.Com, WinFiles, or Frank Condron's World o' Windows. If you're running Windows 98 or Windows ME, you may also be able to get a new driver for your hardware via the Windows Update feature off the Start menu.

If you find and download a new driver version, you can often update the driver by clicking on the device listing in the Device Manager, clicking on Properties, selecting the Driver Tab and then clicking on the Update Driver button. From there, depending on what version of Windows you’re using (the original Win95A, the revised Win95B, Win98, or Windows ME), you’ll either need to manually find where the file is located on your hard disk, and then select it, or the computer will attempt to find it for you. Either way, once the correct file is found, you initiate the update process by simply clicking a button.

Some driver updates force you to create new floppy disks, which you then use to update the driver. Frankly, though it’s more work initially, this is a good solution in the long run, I think, because if you ever have to completely reinstall Windows (such as, when you buy yourself a big new hard drive), you’ll generally want to have copies of your drivers on floppies anyway.

Mind your Ps and IRQs

Finally, if that still doesn’t work, you may need to futz with the dreaded IRQs, or Interrupt Requests. Most hardware devices on your computer need attention from the processor on a fairly regular basis (to check their status) and the mechanism for doing that is called Interrupt Requests (because the device politely asks the processor to interrupt what it’s doing at the time and give it some attention—well, sort of). Because of the need to maintain compatibility with older hardware, today’s PCs are still limited to 16 IRQs (numbered 0-15), which is turning out to be a fairly big problem on many newer, well-equipped computers (read one of my InfoWorld Electric "Plugged In" columns to learn more on the subject).

The general principle with IRQ troubleshooting is that two devices cannot typically share an IRQ (an important exception is with some PCI-based add-in cards), and if they try to, one or sometimes neither of the devices will work properly. If you find that you have an IRQ conflict, where two ISA cards or other non-PCI devices are trying to use the same IRQ, you’ll need to change the settings on one of the devices to an open IRQ. The problem is, not every device is able to use every IRQ, so even though you have other IRQs available, the problem device may be incapable of using one of the open IRQs. If that’s the case, you may need to move another device using one of the IRQs that the problem hardware does work with first, and then free up an IRQ for the problem hardware. So, for example, if IRQ 8 is open but you have a SCSI card that only works with IRQs 9 or 11, you may first need to move whatever’s on 11 to 8, and then set the SCSI card to IRQ 11. Unfortunately, this can sometimes lead to an infuriating puzzle game where you try to match devices with your IRQs.

To find out what IRQs are in use by your computer, double click the computer icon at the top of the Device Manager. You’ll see a new window pop up that shows which devices are using which IRQs. Unfortunately it doesn’t leave a blank for any IRQs that are not in use, so if you need to find an available IRQ you’ll have to look close, count the numbers and see if any are missing. If a number between 0 and 15 is missing, that means that particular IRQ is available.

Some older plug-in cards require you to change the IRQs by setting tiny DIP switches on the card itself, or via a dedicated configuration utility. Most newer Plug-and-Play cards can be changed via Windows 95 or Windows 98. To do so, go to the Device Manager, highlight the product in question, click on the Properties button and then go to Resources Tab. Generally, you’ll have to deselect the Use Automatic Settings button to make any changes. Most devices offer several Basic Configuration choices, which is what you should try first. These are different combinations of IRQs, memory ranges, and I/O ranges. All you typically need to worry about is the IRQ. Some devices also let you adjust these parameters individually by clicking the Change Settings button.

Thankfully, you rarely have to worry about IRQ problems if you’re using Windows 95, 98 or ME because they all do a pretty good job of automatically fixing them before they arise. In fact, this is one of their most important, yet little discussed improvements over Windows 3.1. Unfortunately, Windows 3.0 and 3.1 users still have to worry about this kind of stuff on a semi-regular basis. The problem is not unheard of under Windows 95, 98 or ME, however (I ran into it myself), which is why I’ve included it here.

The End

These tips won’t solve all the hardware problems you may run into, but they should solve a good number of them. The important thing to remember when doing any troubleshooting is that computers really are logical devices and there’s always a logical reason for why something isn’t working. Discovering what that reason is and then applying the right solution isn’t always easy (or intuitive), but if you think about the problem logically and work through it step-by-step, there’s a good chance you’ll be able to solve it on your own. And, if worse comes to worse, you can always just nuke everything and start over (see "Starting Over: Repartitioning, Reformatting and Reinstalling" for more on exactly how to do that). Good luck!

Apr 15, 2009

Share Files Using Encrypting File System

Share Files Using Encrypting File System

Encrypting File System File Sharing

Windows XP's EFS supports file sharing between multiple users on a single file. This provides an opportunity for data recovery by adding additional users to an encrypted file. Although the use of additional users cannot be enforced through policy or other means, it is a useful and easy method for enabling recovery of encrypted files by multiple users without actually using groups, and without sharing private keys between users.

Once a file has been initially encrypted, file sharing is enabled through a new button in the user interface (UI). A file must be encrypted first and then saved before additional users may be added. After selecting the Advanced Properties of an encrypted file, a user may be added by selecting the Details button. Individual users may add other users (not groups) from the local machine or from the Active Directory, provided the user has a valid certificate for EFS.

Enabling EFS file sharing

Sharing encrypted files using EFS has been supported since Windows 2000 through Win32 application program interfaces, but EFS has not been exposed in the Windows Explorer User Interface until the development of the Windows XP Professional.

How to encrypt a file for multiple users?

* Open Windows Explorer and select the file you want to encrypt
* Right-click the chosen file and select Properties from the context menu.
* Select the Advanced button to enable EFS.
* Encrypt the file by selecting the Encrypt contents to secure data check box and Click OK

* If this is the first time this file or folder has been encrypted, a dialog box will appear asking if you would like to encrypt the file only or the folder.
* Select the appropriate choice and click OK. This will return you to the original dialog box.

Note : The file is not encrypted until you click OK. Also, additional users may not be added until the file has been encrypted by the first user.
* Click OK to encrypt the file.
* Open the file properties again through the Advanced properties button and then select the Details button to add additional users. Once the Details dialog box is open, the add user option will be displayed.


Note : Additional information is available in the Encryption Details dialog box which may be useful for troubleshooting purposes.

How to add users?

* Click the Add button

# A new dialog box will be presented showing the existing users and certificates that are cached in the "Other People" certificate store of the local machine. It will also allow new users to be added from the Active Directory by clicking the Find User button.

Note : A user must have a valid EFS certificate in the Active Directory to be added.

# Click the Find User button to find new users


# The standard object picker dialog box will be displayed and a search will be conducted.

A dialog box will display users that hold valid EFS certificates in the Active Directory based on your search criteria. If no valid certificate is found for the given user, the dialog box will be displayed saying "No appropriate Certificates correspond to the selected user"
If valid certificates exist in the userCertificate attribute of the user object in the directory, they will be displayed in the certificate selection dialog box.

Note : Windows XP now performs revocation checking on all certificates for other users when they’re added to an encrypted file. For performance reasons, users that hold a private key are not checked for revocation. However, certificates that do not contain a CDP (Certificate Revocation List Distribution Point) extension (such as those from some 3rd party CAs) will not be validated for revocation status. If the revocation status check on a certificate fails, the messages stating "An internal certificate chaining error has occured" -OR- "The signature of the certificate cannot be verified." will be shown.

If the revocation status and chain building completed successfully, the user will be added to the dialog box and the file will be updated accordingly.
# Click OK to register the change and continue.

Note : Any user that can decrypt a file can also remove other users—if the user doing the decrypting also has write permission.

Note : EFS has a limit of 256K in the file header for the EFS metadata. This limits the number of individual entries for file sharing that may be added. On average, a maximum of 800 individual users may be added to an encrypted file.

How to view the certificate for information?

You can select a user certificate, and view the certificate for information to make your administrative decision. To view a certificate, just follow the instructions:

* Highlight the certificate in the dialog box and click the View Certificate button.
* Click OK to close this dialog box when finished. You will be returned to the previous dialog box within which you can choose the appropriate user to be added to the encrypted file.
* Highlight the selected user certificate that you want to use and click OK.


Noe that encyption is so easy, Always encrypt your private and crucial data.... All the best...!


Source : techarena

10 points for choosing a right Processor

10 points for choosing a right Processor

Which processor is actually the fastest and how important are Hertz when you select new computer? I will clarify concepts and answer some of the most common questions about processors.


1. What is a processor?

Processor, often called the CPU (Central Processing Unit), is the brain of the computer where it accounts for most of the calculations made. There are processors in many types of gadgets, everything from microwave ovens to cars, here we focus however on the ones we have in our computers.
Modern processors can perform billions of calculations every second and they are made up of millions of small transistors mounted on a surface in a few square centimeters.


2. What is the difference between a CPU and a GPU?

CPU is not the only circuit in a computer that handles calculations, the graphics card in the computer is also usually a self-processor that only handles graphics calculations, this is sometimes called the GPU (Graphics Processing Unit).
Even the sound card may have an advanced dedicated processor.


3. What should I choose - AMD or Intel?

Since immemorial time we have AMD and Intel's been on the performance throne and there has always been arguments for both sides. What is the fastest, most power-efficient and most affordable? In the current situation Intel leads in terms of pure performance, while AMD instead focusing on being the affordable option for the budget with a little narrower. And so it has, with few interruptions, been quite a while. Important to know is that when you select the processor, select the platform, thus moderate style and in some cases a common style, so it will be easy to switch to another processor if you would change your mind.


4. How much power, the processor?

This has been the development properly forward the last two to three years and even if you select a fast dual core processor it need not absorb very much power. In this context used TDP (Thermal Design Power) as a unit, in practice the maximum effect that the cooling device must support to the CPU so that it does not overheat. The latest and fastest Core 2 Quad models from Intel is about 65-95 watts TDP, while a simpler dual core processor in a new laptop has TDP-values of around 25-35 watts.

Ultra Low Voltage flavors draws no more than 5-6 watts TDP and the latest Atom processor from Intel, a model that will appear in the mini-computers in the year, draws as little as 2.5 watts. Now that defines Intel and AMD TDP-value in different ways so the value, unfortunately, is not comparable across different platforms.


5. How many cores do I need?

The difference between a single core and a dual core processor is quite large but it is not as obvious to go up to Quad Core. If you're running heavy applications for audio or video editing, the four cores will be preferred (if your program supports this) but if you're looking for the best gaming performance, it is usually better to put money on a fast dual core processor and a fast graphics card. Few games can use more than two cores in the current situation and usually the graphics card is the weak link in terms of performance.


6. How many gigahertz do I need?

A few years ago you could compare hertz rates between different processors and thus get a decent idea of what was the fastest but it is as simple as it no longer. AMD and Intel use different processor architectures and the factors that bus, cache and number of grains to make it properly when you choose. Here it is more important than ever to read the tests and that you select a new and fresh processor so you do not stand with an old platform that you can not upgrade.


7. How much the cache?

The cache is built into the processor itself, which means that the data does not need to detour through working memory (RAM) before being processed. This means that when the cache is used calculations are much faster than otherwise. The more cache you have in the processor the faster the work is, but it is also an expensive component that draws up the overall price. This memory is also divided into different levels, L1, L2, etc. The lower the number the closer the actual processor (and faster).


8. Will I earn something on overclocking?

Overclocking can be a cheap way to get out a little more performance from your computer while you are charged to the processor more than its actual performance. Make sure you have a big cooler and check that your CPU is overclocking friendly (read in properly before). The rule on overclocking is that drawing up the speed of the system bus, thus increasing the CPU clock frequency, but at the same time, insert the motherboard to the test. Many new motherboards have overclocking features built-in smartly that you can control directly from Windows software.


9. Can I change the processor itself?

Before you buy a new processor to your computer, it is important that you have stone eye on the new processor fits in your motherboard. Not only physically but also to the motherboard software (bios) to identify the processor. The actual change is quite simple but you have my thumb in the hand it may be worthwhile to ask someone with experience for help. It can be an expensive business if you slip with the screwdriver when you mount the cooler.

And you are thinking of changing the processor in your laptop then usually just forget. If you are lucky, processor is not soldered but only to disassemble the chassis can be a nightmare and it's not safe to bios support your new CPU and cooler whether it can handle the heat development.


10. How important are the bits?

The major advantage of 64-bit processor and 64-bit operating system is that it can use significantly more working memory, is still software support, however, very limited. If you do not need to work with a workstation that will render 3D animations or similar applications, we recommend 32 bits. To take advantage of a 64-bit processor, software must have support for it.


Source : techarena


Overclocking tutorial for newbies/beginners

Overclocking tutorial for newbies/beginners

Overclocking is about getting your computer to run faster than it actually is intended. To read further, and try some of the things I suggest is at your own risk.

If you are computer freak like myself, and not afraid to risk burning the processor, just read on. But if you are a little sore to your computer, you should probably stop here.

In any case, overclocking is to take small steps and make sure that your computer's cabinet is well chilled. If there is no proper cooling on your processor / graphics card then you are out of it.

This article is intended for beginners who want (and can afford to take risks) to address this. To go further in depth, I can recommend you to visit some expert and dedicated overclocking sites where you can find many guides to come forward.

* What is overclocking?

Overclocking is really rather simple. It's about getting your computer to run at a higher clock frequency than is intended. The benefit of overclocking is that you can buy a processor that runs at a given speed, and then put the clock rate up so it runs as fast as a much more expensive processor. The same can be done with similar way for RAM and graphics card.


* How do I get started?

Overclocking is a little dangerous, but it is not something that you threaten to break arms and legs of. To get started you should take a backup of your documents and important data. But if you are ready to bear up all things, there should not be major problems.

One of the things that will be good to have on hand is a diagnostic program that can monitor your processor temperature. I can recommend the Asus Probe, which can be downloaded for free at asus.com. It is designed for motherboards from Asus. If your motherboard is of a different manufacturer, the manufacturer has probably developed a similar piece of software that you can find on their website.


* What type of overclocking?

There are two different ways you can overclock your processor. One is called FSB-overclocking, and the other called Multiplier-overclocking. Ideally the FSB-overclocking is the easiest and most effective way to overclock, and therefore we will deal more with it.

Your processor works with two speeds. One speed is the internal, which is also the boast with you to your friends. My computer was running, for example, with 1333 MHz internally factory made. Now run it with 1450 Mhz because I have overclocked it

The second speed is the external, which the processor communicates with the rest of the system. If your computer was purchased within the last few years, the external velocity probably either 100 or 133 megahertz (MHz). Processor contact with the outside world otherwise known as the Front Side Bus (FSB) and the external velocity is just as FSB work with.


* Procedure for overclocking

If you have a backup, there is nothing wrong to go. Restart your computer and go into your bios setup.

Depending on your motherboard bios system will differ slightly from the menu items and descriptions, but I will try to describe it as well as I can.

Inside the bios, there will be a menu item called something like 'Advanced setup'. Under 'Bus Frequency" or "FSB Frequency" there should be something like 100 or 133. It allows you to change. It may be that you first have to change a default setting to manual setting.

Try to set your FSB frequency up to 5 megahertz to 138 MHz (if it was at 133 Mhz). Save your changes and your computer will now run with a relatively higher clock frequency. The internal speed of the processor is directly connected to the external velocity. The relationship between the two speeds are determined by the so-called 'multiplier', which I will come back to.. later.

If it runs stable you can try the same maneuver again and put the FSB further with 5 Mhz. You can do this until you observe that the system begins to make mistakes, and becomes unstable. When this happens, go back into bios and set the FSB down to 3-4 MHz. So would like to run the system stable.


* Where is FSB-overclocking?

FSB-overclocking works on your entire system at once, as you adjust to the whole motherboard internal communication speed. Therefore, both your processor, RAM, graphics card, etc. work faster when your FSB is overclocked. It also means that it is not necessarily your processor becoming breathless first. It could be your RAM or your PCI ports only get off. If so, you can successfully invest in additional cooling of these parts.


* What is Multiplier?

Multiplier is the factor that determines the processor's internal speed relative to FSB speed. My own computer has a FSB speed of 133 Mhz, and process variety is an AMD Athlon Thunderbird 1333Mhz. So Multipliers 10 because 133x10 = 1333 (not quite mathematically correct, but it goes )

If you raise your multiplier change only internal processor speed as the FSB speed will not change. So you will not achieve the same results with this type of overclocking. But if you already have overclocked your FSB and your RAM will not take more, the next step would be overclocking the multiplier.

However, it is not all processors that support this type of overclocking. AMD's processors will suffer a small action first, and Pentium 4 does not permit.


* What can I overclock otherwise?

One obvious thing to overclock is your graphics card. In demanding game you can revitalize your graphics card with a time overclocking. I can recommend the Power Strip, which provides an easy approach to this. The program can be downloaded here: http://www.entechtaiwan.com/ps.htm


* When I overclock, my computer will not start!

Then you probably been a little too aggressive with your overclocking. You can save the situation by going into bios and choose to load "Setup defaults". This will lower the FSB to normal and you should be able to boot (unless you burn something)


Source : techarena

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