What are uses of WiMax technology?

- The WiMax technology has been used since a long time to provide assistance to the communication process.

- This area has seen major deployment of wimax technology especially in Indonesia during the calamity of tsunami in the year of 2004. 

- The WiMax technology brought in the possibilities of providing broadband access that helped a big deal in regeneration of the communication. 

- The organizations such as FEMA and FCC (federal communications commission) felt the need of wimax in their communication process. 

- The WiMax applications with high efficiency are available today.

- It is known to offer a broad base for the customers and the services had been improved by adding mobility feature to them.

- The service providers use the WiMax technology for providing various services such as mobile and Internet access, voice, video and data. 

There are other advantages of using wimax technology.  

- You get to save a lot of prospective cost and at the same time you get efficiency in services.

- It is even capable of allowing the video making, VOIP calling and data transfers at high speeds.

- The mobile community has been upgraded so much with the coming of the WiMax technology.

- However, there are three main applications offered by WiMax namely backhaul, consumer connectivity and business.

- The real augmentation has been drawn to communications through WiMax technology because of which they can benefit both from the data transmission and video apart from voice. 

- This has facilitated quick response from the applications as per the situation.  

- A temporary communication services can be deployed by a client using WiMax technology.

- It can even speed up the network according to the circumstances and events.  

- This has got us access to visitors, employees and media on a temporary basis.  

- If we are located in the range of the tower, it is quite easy for us to gain access to the equipment of the premises of for the events.

The factors that make the wimax technology so powerful are the following:

> high bandwidth

> high quality services

> security

> deployment

> full duplex consisting of DSL

> reasonable cost

For some applications, the wimax technology is used exclusively as in the following:

1. A means of connecting for the small and medium sized businesses.  - This technology has enabled these businesses to progress day by day.

- The connectivity offered by WiMax technology is good enough to attract clients.  

- It then provides them a number of services such as that of hotspots and so on.  

- Therefore, this application has gotten into spot light.

2. Backhaul

- The most important application of the WiMax technology is the range.

- This is so because using WiMax tower can be used as a means to connect with the other WiMax towers through line-of-sight communication which involves using microwave links. 

- This connectivity between two towers is called as backhaul.  

- It is capable of covering up to 3000 miles. 

- The WiMax network is even sufficient for covering remote and rural areas.

3. The nomadic broadband is another application of wimax technology which can be considered as an extended plan of wifi.

- The access points provided by WiMax technology might be less in number but they offer very high security.  

- Many companies use the WiMax base station for the development of the business.

What are advantages and limitations of Wi-Fi?

The Wi-Fi has its own set of advantages and limitations. 

Advantages of WiFi

- WiFi makes the deployment of local Area Networks or LANs quite cheap.  

- There are some areas where the cables cannot be installed such as in historical buildings and outdoor areas. 

- But these spaces do not have any problem in hosting a wireless LAN.  

- Wireless Network adapters are being built into almost all the laptops by the manufacturers.

- A basic level of service is provided at which different brands concerning and client network interfaces access points that are competing with each other can inter-operate. 

- The products that have been certified by Wi-Fi alliance show back word compatibility. 

- A standard device for WiFi will work at any place in the whole world unlike our phones. 

- The WPA2 or the WiFi protected access encryption is secure provided a condition that the pass phrase used is quite strong.  

- The new protocols use for WMM i.e., Quality of service increase the suitability of the Wi-Fi regarding its use in latency - sensitive applications. 

- WMM is a power saving mechanism that is used for extending the life of the battery. 

Limitations of WiFi

- Inconsistency of the operation and spectrum assignments poses a problem worldwide.  

- The range all the WiFi networks is limited. 

- A wireless access point typically uses a stock antenna having a range of 100 m outdoors and 25m indoors.

- The frequency band is a major factor for producing variations in the range.  

- The range of Wi-Fi with a 2.4 ghz frequency block is better when compared with the 5.0 ghz frequency block Wi-Fi. 

- Some wireless routers come with detachable antennas. 

- These antennas can be removed for improving the range. 

- In their place upgraded antennas can be fitted. 

- The benefit of these antennas is that they have high directional gain at the remote devices. 

- The local regulations limit the maximum amount of power that can be transmitted by a Wi-Fi. 

- The power consumption of Wi-Fi is quite higher than the other standards.  

- This is so because of the reach requirements of the wireless LAN applications.

- There are technologies available that provide a propagation range that is much shorter. 

- One such technology is Bluetooth and has very low power consumption.  

- Other technologies such as zigbee have low power consumption, a long range but provides low data rate. 

- The most commonly used wireless encryption standard is WEP or wired equivalent privacy. 

- Even this standard has been proven to be breakable even if correct configuration is used. 

- This problem was addressed by WPA or Wi-Fi protected access standard to some extent. 

- By default the wireless access points use the encryption free mode. 

- The wireless security is disabled because of which the LAN can be openly accessed. 

What are uses of Wifi?

- Routers sometimes act as a Wi-Fi access point incorporating a cable modem or a DSL modem.

- These routers are installed in buildings and homes for providing Internet access and other inter networking services to the devices that in turn are connected to a either through a cable or wireless. 

- Similarly, there are routers that are powered by battery and they consist of a Wi-Fi access point and a mobile Internet radio modem. 

- Today smartphones come with this as a built-in capability.  

- However, this feature is disabled by the carriers. 

- The carriers might charge extra money for this. 

- The standalone facilities are provided by Internet packs. 

- The places where there is no network access, wifi is used. 

- Using Wi-Fi, a direct communication link between two computers can be established.  

- There is no intermediate point.  

- This type of transmission is termed as ad hoc wifi transmission. 

- This network mode is now very popular with the multi-player game consoles. Examples are:

       > Nintendo DS

       > PlayStation portable

       > Digital cameras

       > Other consumer electronic devices.

- A citywide Wi-Fi plan has been implemented by a number of the cities around the world.  

- In India, the first city to do so was Mysore.  

- The first city in the world was Jerusalem.

- The first city in United States was Sunnyvale in California to offer city-wide wifi. 

- Another type of wifi implementation is campus-wide wifi.  

- A number of colleges in United States have set up this kind of wifi network.  

- The first university to have it was Carnegie Mellon University. 

- Using wifi, the local area Network can be deployed in very less cost.  

- There are places where it is not possible for the physical transmission medium such as cables to reach. 

- In such places wifi network is of crucial importance.  

- Also, wifi can be easily deployed in historical buildings and outdoor areas.  

- Now, because of the increasing popularity of the Wi-Fi, the manufacturers are developing Wireless Network adapters for most of the notebooks and laptops.  

- This eventually led to a fall in the price of the Wi-Fi chip set. 

- Today, the Wi-Fi chip set is economically feasible and is included in most of the devices.  

- There are many brands of client network interfaces and access-points that are competing with each other.  

- These interfaces are able to inter-operate at a basic level. 

- The Wi-Fi certification for the products is issued by wifi alliance. 

- This makes them backwards compatible with each other. 

- A standard Wi-Fi Device is supposed to work anywhere in the world. 

- The encryption standard that is considered secure is the WPA2 or wifi protected access.  

- But, this would work only if the pass phrase that is being used is strong enough. 

- The Wi-Fi has been made more suitable with the use of new protocols such as quality of service.  

- This has made wifi compatible with latency sensitive applications.  

- Nowadays, for extending battery life power saving mechanisms such as WMM are being used.  

- These are the major uses of wifi technology.

- The usage wifi has been limited because of its limited range. 

- Therefore, in order to cover up a large area several intermediate Wi-Fi access-points have to be set up. 

- The variations in the range can be produced by varying the frequency band.  

- Wifi with a small frequency block works better than wifi with a larger frequency block.

- Wifi with the larger frequency blocks are optionally used. 

- The power of wifi network can be harnessed by using high gain direction antennas instead of using detachable antennas.  

- Another factor limiting the performance of wifi transmission is the local regulations. 

- Wifi also requires high power to operate upon. 

- This is a cause of concern for the devices' batteries.

Explain Border Gateway Protocol (BGP)?

- BGP or Border gateway protocol is the set of rules that is implemented for making the routing decisions at the core of the internet. 

- It involves the use of the IP networks table or we can say prefixes which are used for designating the reach-ability of the network to the autonomous systems. 

- This protocol falls under the category of the path vector protocol or sometimes classified as a variant of the distance vector routing protocols. 

- The metrics of the IGP or the interior gateway protocol are not used by the border gateway protocol rather paths, rule sets or polices are used for making decisions for routing. 

- This is why the border gateway protocol is often called a reach-ability protocol rather than being termed as a routing protocol. 

- The BGP has ultimately replaced the EGP or the exterior gateway protocol. 

- This is so because it allows the full decentralization of the routing process for making transition between the ARPANET model’s core and the decentralized system that consists of a NSFNET backbone and the regional networks associated with it. 

- The present version of the BGP that is being used is the version 4. 

- The earlier versions were discarded for being obsolete. 

- The major advantage is of the classless inter-domain routing and availability of a technique called the route aggregation for making reductions in the routing size. 

- The use of the BGP has made the whole routing system a decentralized system.

- BGP is used by most of the internet service providers for establishing a route between them. 

- This is done especially when the ISPs are multi-homed. 

- That’s why even though it is not used directly by the users; it is still one of the most important protocols in networking. 

- The BGP is used internally by a number of large private IP networks. 

- For example, it is used to combine many large open shortest path first or OSPF networks where these networks do not have the capability to scale to the size by themselves. 

- BGP is also used for multi-homing a network so as to provide a better redundancy. 

- This can be either to many ISPs or to a single ISP’s multi access points. 

- Neighbors of the border gateway protocol are known as the peers. 

- They are created by manually configuring the two routers so as to establish a TCP session on the port. 

- Messages called the 19 byte keep alive messages are sent to the port periodically by the BGP speaker for maintaining the connection. 

- Among the various routing protocols, the most unique is BGP since it relies up on TCP for transporting. 

- When the protocol is implemented in the autonomous system among two peers, it is called IBGP or the internal border gateway protocol. 

- The protocol is termed as the EBGP or the external border gateway protocol when it runs between many autonomous systems.

- Border edge routers are the routers that are implemented on the boundary for exchanging information between various autonomous systems.

- BGP speakers have the capability for negotiating with the session’s option capabilities such as the multi-protocol extensions and a number of recovery modes. 

- The NLRI (network layer reach-ability information) can be prefixed by the BGP speaker if at the time of the creation itself, the multi-protocol extensions are negotiated. 

- The NLRI is advertised along with some address family prefix. 

The family consists of the following:

Ø  IPv4

Ø  IPv6

Ø  Multicast BGP

Ø  IPv4/ IPv6 virtual private networks

- These days the border gateway protocol is being commonly employed as the generalized signaling protocol whose purpose is to carry information via the routes that might not form the global internet’s part. 

Explain the concept of piggybacking?

- Piggybacking is a well known technique used in the transmission of data in the third layer of the OSI model i.e., the network layer. 

- It is employed in making a majority of the frames that are transmitted from receiver to the emitter. 

- It adds to the data frame, the confirmation that the sender sent on successful delivery of data frame. 

- This confirmation is called the ACK or acknowledge signal. 

- Practically, this ACK signal is piggybacked on the data frame rather than sending it individually by some other means. 

Principle behind Piggybacking

- The piggybacking technique should not be confused with the sliding window protocols that are also employed in the OSI model. 

- In piggybacking, an additional field for the ACK or the acknowledgement signal is incorporated in to the data frame itself. 

- There is only a difference of bit between the sliding window protocol and piggybacking.

- Whenever some data has to be sent from party to another, the data will be sent along with the field for ACK. 

The piggybacking data transfer is governed by the following three rules:

Ø  If both the data as well as the acknowledgement have to be sent by the party A, it has to include both the fields in the same frame.

Ø  If only the acknowledgement has to be sent by the party A, then it will have use a separate frame i.e., an ACK for that.

Ø  If only the data has to be by the party A, then the ACK field will be included within the data frame and thus transmitted along with it. This duplicate ACK frame is simply ignored by the receiving party B.

- The only advantage of using this technique is that it helps in improving efficiency. 

- The disadvantage is that is the service can be blocked or jammed by the receiving party if there is no data to be transmitted. 

- Enabling a receiver timeout by means of a counter the moment when the party receives the data frame can solve this problem to a great extent. 

- An ACK control frame will be sent by the receiver if the timeout occurs and still there is no data for transfer. 

- A counter called the emitter timeout is also set up by the sender which if ends without getting any confirmation from the receiver will make the sender assume that the data packet got lost in the way and therefore will have to re-transmitted.

- Piggybacking is also used in accessing the internet.

- It is used in establishment of a wireless internet connection by means of wireless internet access service of the subscriber without taking explicit permission from the subscriber. 

- However, according to the various jurisdiction laws around the world, this practice is under ethical and legal controversy. 

- In some places it is completely regulated or outlawed while at other places it is allowed.  

- A business customer who provides services related to hotspots, as of cafe and hotels, cannot be thought of using piggybacking technique via non – customers. - A number of such locations provide services for a fee. 

Explain the concepts of threads and processes in operating system?

Threads and processes are an important part of the operating systems that have features of multi–tasking and parallel programming. These come under the sole concept of ‘scheduling’. Let us try to understand these concepts with the help of an analogy.

- Consider the process to be a house and threads are its occupants. 

- Then, process is like a container having many attributes. 

- These attributes can be compared to that of a house such as number of rooms, floor space and so on. 

- Despite having so many attributes, this house is a passive thing which means it can’t perform anything on its own. 

- The active elements in this situation are the occupants of the home i.e., the threads. 

- The various attributes of the house are actually used by them. 

- Since you too live in a house you must have got an idea how it actually works and behaves. 

- You do whatever you like in the house if only you are there. 

- What if another person starts living with you? You just can’t do anything you want to do. 

- You cannot use the washroom without making sure that the other person is not there. 

- This can be related to multi – threading. 

- Just as a part of estate is occupied by the house, an amount of memory is occupied by the process. 

- Just as the occupants are allowed to freely access anything in the house, similarly the occupied memory is utilized by the threads that are a part of that process i.e., the access to memory is common. 

- If one process allocates some memory, it can be accessed by all other threads also. 

- If such a thing is happening, it has to be made sure that from all the threads, the access to the memory is synchronized. 

- If it cannot be synchronized, then it becomes clear that the memory has been allocated specifically to a thread. 

- But in actual, things are a lot more complicated because at some point of time everything has to be shared. 

- If one thread wants to use some resource that is already under use by some other thread, than that thread has to follow the concept of mutual exclusion. 

- An object known as the mutex is used by the thread for achieving exclusive access to that resource. 

- Mutex can be compared to a door lock. 

- Once a thread locks this, no other thread can use that resource until the mutex is again unlocked by that thread. 

- Mutex is one resource that a thread uses. 

- Now, suppose there are many threads waiting to use the resource when mutex is unlocked, the question that arises now is that who will be next one to use the resource. 

- This problem can be solved by either deciding on the basis of length of wait or on basis of priority. 

- Suppose there is a location that can be accessed by more than one threads simultaneously.

- You want to have only a limited number of threads using that memory location at any given point of time. 

- This problem cannot be solved by mutex but with another resource called semaphore. 

- Semaphore with a count of 1 is the resource that can only be used by one thread at a time. 

- In semaphore of greater count more threads can access it simultaneously.  

- It just depends up on how you characterize or set the lock.

What is Paging? Why it is used?

- Paging is a very important concept for the computer operating systems required for managing the memory. 

- It is essentially a memory management scheme which is used for storing as well as retrieving data from the secondary memory devices.

- Under this scheme, the data is retrieved from the secondary storage devices and handed over to the operating systems. 

- The data is in the form of blocks all having the same size. 

- These data blocks are called as the pages. 

- In paging, for a process the physical address space can be kept as non–contiguous itself. 

- Paging is a very important concept for implementing the virtual memory in the operating systems designed for contemporary and general use. 

- This allows the disk storage to be used for the data that is not able to fit in to the RAM. 

- The main functions of the paging technique are carried out when a program attempts to access the pages that have no mapping to the physical RAM. 

- This situation is commonly known as the page fault. 

- In this situation, the OS comes to take control of the error. 

- This is done in a way that is invisible to the application. 

The operating system carries out the following tasks in paging:

Ø  Locates the data address in an auxiliary storage.

Ø Obtains a vacant page frame in the physical memory to be used for storing the data.

Ø  Loads the data requested by the application in to the page frame obtained in the previous step.

Ø  Make updates to the page table for showing the new data.

Ø Gives back the execution control to the program.This maintains a transparency. it again tries to execute the instruction because of which the fault occurred.

- If space is not available on RAM for storing all the requested data, then another page from RAM cannot be removed. 

- If all of the page frames are filled up, then a page frame can be obtained from the table which contains data that will be shortly emptied. 

- A page frame is said to become dirty if it is modified since its last read operation in to the RAM. 

- In such a case it has to be written back in to its original location in the drive before it is freed. 

- If this is not done, a fault will occur which will require obtaining an empty frame and reading the contents from drive in to this page. 

- The paging systems must be efficient so as to determine which frames are to be emptied. 

- Presently many page replacement algorithms have been designed for accomplishing this task. 

- Some of the mostly used for replacement are:

Ø  LRU or least recently used

Ø  FIFO or first in first out

Ø  LFU or least frequently used.

- To further increase responsiveness, paging systems may employ various strategies to predict which pages will be needed soon. 

- Such systems will attempt to load pages into main memory preemptively, before a program references them. 

- When demand paging is used, paging takes place only when some data request and not prior to it. 

- In a demand pager, execution of a program begins with none of the pages loaded in to the RAM. 

What are main features of TestComplete?

Many of the software applications are being written as web–based applications that can be run in a browser. The measure of effectiveness with which these applications are tested varies from organization to organization. 

- Test complete automated testing tool offers the answer to this demand. 

- For tests such as regression tests, responsiveness can be generated only through automated testing tools as such. 

- Automated testing is the way to provide many benefits including repeat-ability and speed of the test execution. 

- Test automation is known to induce long term efficiency in a software system or application.

- Developers also get a rapid feedback and can carry out unlimited iterations of the tests.

- Reporting gets customized and finding defects that were missed during the manual testing becomes easy.

-  However, automation always does not prove to be advantageous.

Features of TestComplete

Test complete  testing tool comes with certain features which we shall state now:

1. Keyword testing: This tool comes with a keyword–driven test editor that is built– in and consists of many keyword operations corresponding to the appropriate automated testing actions.
2. Test record and play back: This tool records the key actions which are required to play back the test. All the actions other than the required ones are then discarded.
3. Full featured script editor: This is another built – in editor using which the test scripts can be written manually. This editor comes with some special plug – ins that provide further assistance.
4. Script debugging features: This feature lets you stop before every statement that can be executed so that you can keep a track of what is going on and make changes accordingly.
5. Access to properties and methods of the objects: The names of all the visible elements can be read by this tool including internal elements of the following applications:

a)   Delphi

b)   C++builder

c)   .net

d)   WPF

e)   Java

f)    Visual basic etc.

Also this tool enables the access to values through test scripts so that they can be verified and used in the tests.

6. Unicode support: Tool has a Unicode character set support which enables the user to test the applications that are non – ASCII and use characters such as Hebrew, greek, Arabic, katakana and so on.
7. Issue–tracking support: This tool comes with issue tracking templates which can be deployed for the creation as well as modification of the items that reside in issue – tracking systems. The tool currently provides support for the following:

a)   Microsoft visual studio 2010,2008 and 2005 team system

b)   Bugzilla

c)   Automated QA AQdev team

8. Open architecture (COM based): An open API, COM interface forms the basis for the test complete’s engine. This makes this tool independent of the source – language and enables it to read the debugger info. It can use this info during run time via debug info agent of test complete.
9. Test visualizer: This feature of test complete lets you take screen shots of the test recording as well as play back thus allowing you to make comparisons among the actual as well as the expected screens during the run time.
10. Support for plug–ins: This feature allows the third party vendors to connect with test complete via their software systems and applications.