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.

Sliding Window Protocols? – Part 1

- There are many types of data transmission protocols of which one type is the packet based data transmission protocols. 

- These protocols have a feature called the sliding window protocol.

- The sliding window protocols are a great help wherever the in-order delivery of the data packets demand reliability. 

- For example, the Data link layer of the TCP (transmission control protocol) model and OSI model demand such reliability and thus use window sliding protocol. 

- According to the concept of the sliding window protocols, a consecutive number which is unique is assigned to each and every portion of the transmission i.e., the packets.

- These numbers are used by the receiver for placing the packets it will receive in their correct order. 

- Also, with the help of these numbers, the missing packets can be identified and the duplicate packets can be removed. 

- One problem regarding the sliding window protocols is that it has kept no limits for the size of these numbers that are required. 

- An unlimited number of data packets can be allowed to be communicated at any instant of time if limits are placed on the number of packets involved in transmission or reception. 

- By this, we mean using the sequence numbers of fixed size. 

- By term window we refer to the transmission side. 

- It actually represents the logical boundary or limit of the number of packets that the receiver has to acknowledge. 

- The transmitter has to be informed by the receiver for each ACK (acknowledgement) packet regarding the maximum size or the window boundary of the current receiver buffer. 

- For reporting the window size of the received buffer, a 16 bit field is used in the TCP header. 

- The maximum limit or boundary of the window that we can have is 2¹⁶ i.e., 64 KB. 

- When operating in the slow start mode, the counting of the transmitter begins with a low packet count.

- Gradually, the number of packets involved increases in every transmission after the ACK packet has been received. 

- Whenever it receives an ACK packet, the window slides logically by one packet for the transmission of a new packet. 

- On reaching the window threshold, one packet is sent by the transmitter for every one packet of ACK received. 

- Suppose the limit of the window is 10 packets and the transmitter is in slow start mode. 

- Then, first one packet will be transmitted followed by another two. 

- Between these two transmissions, it will send an ACK packet also. 

- This process will continue until the limit of 10 has reached. 

- After crossing the limit, the transmission is restricted to one i.e., for every ACK packet received only one data packet is transmitted. 

- When viewed during simulation, it seems as if the window is shifting by distance of one packet whenever an ACK packet is received. 

- For avoiding the traffic congestion, the sliding window protocol works up a great deal.

- In this way the application layer would not have to worry about transmission the next set of data packets. 

- It can continue to do so since the sliding windows of the packet buffer will be implemented on both the sides i.e., the receiver’s and the sender’s side by the TCP. 

-However, the network traffic influences the window size dynamically to a great extent. 

- In order to achieve the highest possible throughput, care should be taken for not forcing the transmitter to stop the transmission before one RTT or round trip delay time by the sliding window protocol. 

- The bandwidth delay product of the links in the communication should be less than the limit of the data amount that can be sent before sending ACK packet. - If this condition is not met, the links’ effective bandwidth will be limited by the protocol. 

What are benefits of instant messaging?

Instant messaging comes with both risks and benefits. Here we focus up on its benefits.

Benefits of Instant Messaging

1. IM serves to be of great advantage in the environments that are geographically dispersed. The major benefit here is that it cut downs on the cost of expensive phone calls.
2. The communication channels can be augmented with the help of instant messaging. This will become clear from the following: suppose there is a conversation going between an external client and the team members can converse within themselves using IM for clarification of some points or plotting a strategy. Here, the IM is said to serve as a back channel.
3. IM serves as an efficient tool for clearing up the clutter on desktop and lets you respond immediately. Most of the business processes are time sensitive: problem resolution, crisis management, customer service etc. to name a few. IM is the solution for all these processes.
4. IM serves well in case of an emergency. The critical information can be rapidly disseminated to the whole company or individuals in cases such as that of health issues. Natural catastrophes, schedule changes, or network outages etc. most of the times, the network of IM services works well when most of other e – mail and phone networks are down.
5. A number of work groups can be linked through IM. Thus, it acts as a bonding between the two groups. The productivity of the ad-hoc contacts can be increased by enabling them to be quickly added to some work group.
6. IM services can also be used for routing the IMs to cell phones through the IM – to – SMS (short messaging service) gateway services. An example of such a service is find – me service.
7. Through IM services people have a quick reach to the experts if they want to survey multiple consultants or to have an instant consultation.
8. IM is a sort of self–service. People can place queries to the human resource virtual agents via person to machine IM services for obtaining information regarding enrollments or benefits. This also provides the staff with access to the data and speeds up the business processes.

More about Intant Messaging

- IM is one of the few small things that are a must for the effective communication 

- However, IM is embraced as a useful utility at workplace by some owners of small businesses. 

- IM services have been used to completely replace the traditional methods of communications or to provide support them. 

- IM is also a real – time means for communication. 

- But the text records of the IM conversations are kept by the exchange just as in the case of e–mail messages.

- This lets the IM function as a quick conference call without having the employees leave their desks. 

- It acts as a powerful means for bringing all the people on a web page common to all.  

- IM is an effective tool for conducting group chat. 

- Nowadays, such IM platforms that allow for group text chatting. 

- Plus, they also allow you to save the chat history. 

- Team members that are at some off- site locations can be connected through IM. 

- Through IM it becomes easy to stay connected and archive files.

How Instant Messaging Works?

Instant Messaging or IM is a very popular trend among all these days. A number of instant messaging services today offer features such as web conferencing, voice over IP and other video calling features. With such features both the IM features and video calling abilities can be integrated. 

About Working of Instant Messaging

- Each IM service has its own client that may be either a browser based client or some separate piece of software.

- These clients typically work with their sole company but some are designed in such a way that they support other services also. 

- There are some other third party clients that can connect with a number of major IM services. 

- Few such examples are Miranda IM, Trillian, Adium and so on.

- The IM program installed on your system connects to the IM Company via internet. 

- Here the user’s identity is verified. This process is termed as authentication. 

- After verification, the information or the ‘messages’ can be start exchanging between the users. 

- This IM program installed on your system is called the IM client. 

- When you start it up, it connects to the IM server of its company. 

- To log in to the IM service, you need to have an user ID and password. 

- Once they are verified to be correct, you are logged in. You are connected to the IM network. 

- A list of your friends who are currently online will be displayed. Your list will be changing as per who all are signing in and out. 

- People might have set different IM status such as ‘online’, ‘offline’ or ‘busy’ etc. when you type a message to your friend and hit enter; this message reaches him after traveling from your IM client through the IM server to which it is connected.

- The messages you send reach directly to your friends. 

- A pop up IM window displays your message to them. 

- As the chat progresses further, the messages travel to and fro between the two clients with very less delay of time. 

- Consider sending a file to your friend. You attach the file to the text and press enter. 

- Then your IM client will place an inquiry at the IM server to know the status of your friend. 

- If your friend is connected to internet, a direct connection to his IM client is established.

- The reason for using a direct connection is that it is much faster and efficient rather than sending files through a number of intermediate servers in case of an indirect connection. 

- Also, using a direct connection saves on bandwidth. 

- Instant messages are quite small in size and messages of a whole month may sum up to only 1 megabyte that is quite a tiny amount of space.

- This also enables instant messaging services to work equally on slow as well as fast internet connections.

How Inter-operability is supported by Instant Messaging?

- An instant messaging service can support a number of simultaneous conversations. 

- These are small applications that can cater to only small business needs. 

- But for larger organizations more sophisticated applications are required that can work in cooperation. 

- The enterprise versions of these applications provide solution to these problems.

- Some examples of larger IM applications are:

1. XMPP
2. Lotus same time
3. Microsoft office communicator and so on.

- These applications can be integrated with the workflow systems.

- These applications are also known as EAI or enterprise application integration as per certain constraints such as data storage in a specified format. 

- Several attempts have been made for creating a unified standard. 

What is meant by Instant Messaging?

Almost everyone today is familiar with the term ‘Instant messaging’ or IM in short. 

- This is a type of communication that sustains over the internet and quickly transmits the text based messages between people (i.e., senders and receivers). 

- The basic purpose of IM is to provide “real time direct written language–based online chat”. 

- It does this through push mode and other shared clients between two or more people using personal communication devices (mobiles) and personal computers. 

- A network such as the internet is used for conveying the text message for the person it is intended for. 

- IM addresses two kinds of communications namely:

1. Point – to – point communications i.e., from one person to another one person.
2. Multicast communications i.e., from one sender to a number of receivers.

- Nowadays, much enhanced modes of communication have been introduced by advanced instant messaging services. 

- Some enhancements are inclusion of video chat, audio calling and hyperlinks to other media etc. 

- The umbrella term is the online chat under which the concept of IM falls. 

- The similarity between them is that they are text based, happens in real time and offer bi – directional flow of messages. 

- The only distinction is that the IM is based up on clients. 

- The connections between the known users are facilitated by these clients only through a contact list (also known as friend list or buddy list).

- On the other hand, chat works up on web – based applications that facilitate communication between multiple users.

- A number of communication technologies that facilitates text based communication are combined together to provide the service of instant messaging. 

- The biggest feature of the IM – chats is that they take place in real time just like a phone call. 

- IM is different from the other web services such e–mail in the sense that users here perceive the “quasi – synchronicity of the communications”. 

- In IM, you can message only those people who are online at that time. 

- However, there exist some systems that allow you to message offline people, thus drawing some similarity between e–mail and IM.

- IM is cheap and effective means for efficient communication. 

- It allows immediate receipt of the message and also enables us to reply back immediately. 

- However, it is not necessary that the transaction control might support the IM. 

- In some cases there are additional features that make IM more interesting as mentioned below:

1. Enabling users to see each other via web cam.
2. Using headphones and microphones and talk for free over internet.
3. File transfers
4. Saving a text conversation for future reference.

- Instant messaging came much before the internet and first appeared on systems such as multics (multiplexed information and computing service) and CTSS or compatible time sharing system which are multi – user systems. 

- Some of the IM services such as ytalk, talk, ntalk and so on, peer – to – peer protocol.

- Some other examples of early IM services are:

1. Zephyr notification service
2. Bulletin board system or BBS
3. Freelancin round table
4. Compuserve CB simulator: this was the first dedicated online chat service

- Real time text was also a feature of these early instant messaging services.   

- AOL’s real time IM implements the modern real time text feature as an optional feature. 

- Video calling features such as web conferencing services can integrate both IM abilities and video calling.

What is Dynamic synchronous transfer mode (DTM)?

Dynamic synchronous transfer mode or the DTM is a technology developed for optical networking. The ETSI (i.e., the European telecommunications standards institute) standardized this technology in the year of 2001 marked with the following beginning specification ‘ETSI ES 201 803 – 1’. 

This is a circuit switching network technology that doubles as a time division multiplexing technology too. Actually, this technology is built up on a combination of the switching and transport.

This technology guarantees to provide QoS or quality of service for services that are involved with the streaming of videos. 

However, it might be used for packet – based services also. It is marketed for the following:

1. Professional media networks
2. Mobile TV networks
3. DTT or digital terrestrial television networks
4. Content delivery networks
5. Consumer oriented networks (for example, triple play)

What is Switching?

- Switching of the channels is specified by DTM. 

- This is what that makes it different from the other transmission techniques that we have, for example, SONET (synchronous optical networking), SDH (synchronous digital hierarchy) and so on. 

- End to end provisioning is done for the DTM channel over a network with general topology through the use of control signaling.

- DTM therefore represents a circuit switched system. 

- The switches are nothing but time space switches that guarantee the QoS property. 

- The allocation of the resources is done physically for each channel in the switch. 

- This is quite contrary to the switches that are based up on packets or cells. 

- In those kind of switches there is always a competition for resources between the packets and cells. 

- Such a competition leads to delaying and discarding of the packets and cells. - Other methods offer a shared resource allocation mechanism that draws a limit for the packet and cell switches regarding their utilization of the network in such way that the QoS is maintained at a certain level. 

- But DTM does not follow this shared allocation mechanism rather it implies that a network can be loaded up to full limit theoretically and still can guarantee the QoS. 

- Thus, here real utilization is more like a question of adaptation of the network topology as well as its link capacities considering the actual traffic matrix.

- Packet and cell based switching technologies are more suited to statistical multiplexing.

- It means whenever a packet streams in a router come at an outgoing link that is common to all of them, buffering is carried out until the resources are free on that particular link.

- In this way, it becomes possible to make use of the outgoing link to the maximum degree possible without causing many delays. 

- This also proves fitting for the best effort traffic. 

- But there are certain QoS requirements of the streaming media that cannot be ignored. 

- Streaming traffic is by nature not statistical and therefore is better maintained by end to end resource allocation.

- This category is applicable for audio and video services.

- This is not exclusive of the IP traffic gained via guaranteed QoS transport if majority of the content is audio and video. 

- Some other technologies such as that of IP and Ethernet were also adopted for the same purpose. 

- Multi protocol label switching or MPLS can be applied to the carriage network for improving the reliability as well as determinism that is required by most of the streaming media. 

- This technology is applied along with the techniques such as the forward error correction.

- Ethernet has been made supportive for audio and video transmission by improvement in technologies such as the provider backbone bridge traffic engineering. 

- The development of dynamic synchronous transfer mode took place at the royal institute of technology. 

What are the features of Eggplant testing tool? How is Eggplant run?

Eggplant is the GUI test automation tool that uses the black box approach in its testing process. The product stands out in the category of the GUI test automation tool and has even received US patent for its extra ordinary features. 

Features of Eggplant

The features of eggplant are:

1. Guided record mode: This record mode is quite sophisticated in comparison to the regular mode. It generates code by means of capturing the images thus avoiding the extra and unnecessary recording of the keyboard and mouse events.
2. Debugging
3. Code completion
4. Eggplant can be integrated very well with the other quality management software. It can be further used for augmenting the systems like the HP quality center.
5. Eggplant features an execution only mode i.e., the software testers and developers have the freedom of running the tests unattended via the command line interface of the eggplant.

 It can be used for a number of testing methodologies such as:

1. Mobile testing
2. Cross browser testing
3. Cross platform testing
4. Rich internet application testing
5. Performance testing

A free trial of eggplant software can be downloaded from the website of the company. Some additions that were made to the version 11 of the eggplant are:

1. Integration of the OCR engine
2. Sense talk scripting
3. Mac OS X lion support

The mobile version of the eggplant lets the software testers to carry out automated testing on mobile devices. Eggplant mobile provided a universal solution for testing the mobile applications across a number of mobile operating systems such as the following:

1. Android
2. iOS
3. blackberry
4. Symbian
5. Windows

- The OCR engine that was integrated in version 11 of the eggplant is a global one and also supports the latest version of the windows – windows 8. 

- The scripts developed by the eggplant are reusable. 

- The eggplant software can be made ready within an hour and you can start writing test scripts and executing them without wasting much time.

- To set up the eggplant software follow the below mentioned steps:

Ø First install the eggplant application.

Ø Now set up the system under test and install a VNC server on it.

Ø Set up a VNC connection.

ØFor a better understanding of how to use the application it is recommended that you take a tour of it.

Testing Process with Eggplant

Now we present a brief overview of the testing process with eggplant:

1. Set up your SUT and a VNC connection as mentioned previously in the article.
2. The SUT is controlled through eggplant so that you can capture images indicating the SUT interface elements. These are the elements with which you want the eggplant to have an interaction with.
3. Third stage involves generation of the scripts that guide the eggplant regarding what is to be done at the image locations that you have selected.
4. You can execute the scripts as many times as you require carrying out a particular task such as validating a process.
5. The result is generated in the suite editor and consists of detail run info and statistics that you can use for analyzing your results.

Best thing about eggplant is that even if it can be installed only on one computer (since it comes only with one computer per license), it can test any number of other computers. The scripts are created on the controller machine from where they can be executed on any other computer. This it does through the VNC (virtual network computing) server which sends the commands to the SUT. 

How do you schedule and run tests in Test Director?

In this article we shall see how the tests can be scheduled and run. 

By configuring the conditions the test director can be instructed to postpone the run of the current test till the completion of some other specified tests is over. For example, the test b is scheduled to be run only after the test a finishes with the execution and there is one more test c which is scheduled to run only if the test b passes.

Also, the tests a and b can be scheduled to be executed a day prior to the execution of the test c. the tests and their conditions are displayed by the execution flow in the form of a diagram. 

Steps to schedule tests in test Director

Follow the below mentioned steps to schedule a test run:

1. Firstly, make sure that the test module is in the view mode and if it is  not then first enable it.
2. Second step involves creation of a new test. Click on the execution flow tab in the test lab module. Choose a folder in the test sets tree and click on the ‘new test set’ option. You will get a ‘new test set’ dialog box. Type in the following details:

a)   Test set name

b)   Description

Once you are done click OK and the test set will be added to the test sets tree in the left pane by the test director.

3. Add a test that you want to add to the test set created in the previous step. Using the ‘select tests’ button  to make the test director display the test plan tree in the right pane. Then, type the name of the test to be searched for in the find box in the test plan tree and click find button. Select the searched test and add it to the test set using the ‘add tests to test set’ button.
4. Any number of tests can be added to the test set. To add the tests to the execution flow either simply drag them in to the execution flow area or double click on them.
5. Add conditions using conditions tab. When you will click on the new button a ‘new execution condition’ dialog box will pop up. Select the required test and then passed option. This will instruct the test director to execute the next test only after the successful execution of the previous test. Click OK once done with this and the condition will be added to the run schedule of by the test director in the test dialog box.
6. You can even add a dependency condition to the tests by clicking on the time dependency tab. You will get a field titled ‘run at specified time’, in that specify the date of execution and click OK. Clicking on OK will close the run schedule. The conditions will be displayed by the test director in the execution flow area.
7. Further, if required, some execution condition can also be added to the tests.
8. For rearranging the tests in a hierarchical way, click on the perform layout option. You can then view the dependencies between the tests clearly.  

How the tests are run in Test Director?

We get two options form the test director namely:

a)   Running tests manually and

b)   Automating the tests.

Follow the steps below for the manual execution of a test:

1. Click on the test lab module to display the test lab module.
2. From the test sets select the required test set.
3. From the execution grid select the required test.
4. Clicking on the run will open up a manual runner dialog box.
5. To begin the test run click on the test run. Parameter values dialog box will open up.
6. Assign the parameter values for the test.
7. Click OK and test director will show up the manual runner. The step details dialog box will open up. Perform the execution process step by step.
8. After running all the steps return to the default manual runner display. End the test run by clicking on the end of run button.