Specify the Port Number for AD, DNS, DHCP, HTTP, HTTPS, SMTP, POP3 & FTP? AD- uses LDAP Udp 389 and UDP 135,DNS- 53,DHCP-67,68,HTTP-80,HTTPS-,SMTP-25,POP3-110 & FTP-20,21.

Explain the functionality of FTP Server? The FTP server is to accept incoming FTP requests. Copy or move the files that you want to make available to the FTP publishing folder for access. The default folder is drive:InetpubFtproot, where drive is the drive on which IIS is installedIn the client-server model, a file server is a computer responsible for the central storage and management of data files so that other computers on the same network can access the files. A file server allows users to share information over a network without having to physically transfer files by floppy diskette or some other external storage device.

What is Virtual Hosting? Also known as shared hosting, this form of web hosting should suffice for most everyone. Virtual hosting simple refers to the fact that your site is on one server, and that this server hosts mulitple sites. You are virtually shared - your site will not be the only one on this specific server. Very few sites would actually need the power of a dedicated server, so this option provides to be a reliable and cheap solution.

How is the Cloud Computing different from primitive Client-Server Architecture?The primitive Client-Server architecture is a one-to-one communication between only two physical machines namely Client machine and Server machine (datacenter). Whereas the cloud computing, infrastructure is similar at the client side but varies at server-side. The server-side contains a main Cloud Controller that forwards the request to its worker machines known as Nodes. These nodes are a grid computing machines that dedicate all its resources to process application. These nodes are maintained in clusters. So a cloud computing infrastructure is quite complicated on server side that processes all the requests from clients and send the result back.

What is meant by Middleware? Middleware is a distributed software needed to support interaction between clients and servers. In short, it is the software that is in the middle of the Client/Server systems and it acts as a bridge between the clients and servers. It starts with the API set on the client side that is used to invoke a service and it covers the transmission of the request over the network and the resulting response.It neither includes the software that provides the actual service - that is in the servers domain nor the user interface or the application login - that's in clients domain.

What is Subnetting? Why is it used? Used in IP Networks to break up larger networks into smaller subnetworks. It is used to reduce network traffic, Optimized network performance, and simplify management i.e. to identify and isolate network problems.

How network Gateway is different from Routers? GatewayA device connected to multiple physical TCP/IP networks capable of routing or delivering IP packets between them.

RouterIt’s a layer 3 device that connects 2 different networks and routes packets of data from one network to another. It breaks up Broadcast domain as well as Collision Domain.

What's the benefit of subnetting?Reduce the size of the routing tables. Reduce network traffic. Broadcast traffic can be isolated within a single logical network. Provide a way to secure network traffic by isolating it from the rest of the network.

What are the differences between static ip addressing and dynamic ip addressing?With static IP addressing, a computer (or other device) is configured to always use the same IP address. With dynamic addressing, the IP address can change periodically and is managed by a centralized network service

http://www.theshulers.com/whitepapers/internet_whitepaper/

Understanding Domain Name Servers and Web Addresses resolution

The machines on web don't understand the human readable domain names (eg: www.humlog.net) but

they need addresses in a format called IP address. So there must be someone sitting in between our

browser and the web server (on which the web page is hosted/stored) who translates this human

readable domain name to machine understandable IP address. This translation is called Domain Name

Resolution and it can happen in your browser or in your computer, or in your router or on the web.

Let us understand these behind-the-scenes processes.

1. All browsers have their own caches which store the most recently browsed domains and their IP

addresses. So the first step in Domain Name Resolution is for the browser to check in its cache for an

entry of the current domain name. If it finds an entry in cache, it reads the corresponding IP address

and forwards it to the machines on web, so that they can find the address and return the contents

sitting on that address. In this case the Domain Name Resolution happened in the browser's cache.

2. If the browser cannot find an entry in its cache, then the request for Domain Name Resolution goes to

the Operating system's caches. If OS finds an entry in its cache, the Domain Name Resolution

happens in the OS itself.

3. If the OS cannot find an entry in its cache, then the request for Domain Name Resolution goes to the

DNS resolver configured in the computer. A DNS resolver contains address of the DNS server which

will be used for Domain Name Resolution. Usually the DNS resolver is auto configured as part of IP

configuration by the Internet service providers.

4. DNS resolver forwards the request to the DNS server. From here on, the process of Domain Name

Resolution gets interesting.

5. A DNS server contains a mapping of domain names and their corresponding IP addresses and is

capable of querying other DNS servers on web in case, it itself doesn't contain a domain name entry.

6. Every DNS server knows the address of the root DNS server which contains a mapping of all the

top-level domains and their corresponding IP addresses. Top-level domains are the last part of your

domain name (inwww.humlog.net, its net). For querying the root DNS server, the domain name is

broken into parts starting backwards. So if the domain name is www.humlog.net, first part from

backside is 'net'. A query is made to root DNS server asking for the IP address of the DNS server

responsible for .net domains.

7. Now this DNS server, which is responsible for .net domains, is queried for the next part of the domain,

i.e. humlog. This will return the address of the name server of the website (humlog.net)

8. In the final step, the name server of website is queried for the next part, i.e. www. This will return the

IP address of the domain name 'www.humlog.net' and we can get to see the contents of the website.

Usage

TCP is used in case of

non-time critical

applications.

UDP is used for games

or applications that

require fast transmission

of data. UDP’s stateless

nature is also useful for

servers that answer

small queries from huge

numbers of clients.

Examples

HTTP, HTTPs, FTP, SMTP

Telnet etc…

DNS, DHCP, TFTP, SNMP,

RIP, VOIP etc…

Ordering of

data packets

TCP rearranges data

packets in the order

specified.

UDP has no inherent

order as all packets are

independent of each

other. If ordering is

required, it has to be

managed by the

application layer.

Speed of

transfer

The speed for TCP is

slower than UDP.

UDP is faster because

there is no error-

checking for packets.

Reliability

There is absolute

guarantee that the data

transferred remains

intact and arrives in the

same order in which it

was sent.

There is no guarantee

that the messages or

packets sent would

reach at all.

Differences between TCP and UDP :-

TCP UDP

Sequenced Unsequenced

Reliable Unreliable

Connection-oriented Connectionless

Virtual Circuit Low Overhead

Acknowledgments No Acknowledgments

Windowing flow control No Windowing of flow control

Basic Features of TCP :-

Some of the basic features of TCP are :-

Data Transfer

Reliability

Connections

Flow Control

Precedence and security

Multiplexing

How it Works :-

There are four distinct elements that uniquely identify a TCP connections. They are :-

IP address of the Sender

IP address of the receiver

TCP port of the sender

TCP port of the receiver

To establish a TCP session, the two computers participating in the session must first go

through what is known as the ” three-way handshake” . There are two scenarios

where a three-way handshake would take place, namely :-

Establishing a connection ( an active open )

Terminating a connection ( an active close)

 What are the categories of defects?

There are three main categories of defects:

1. Wrong: The requirements have been implemented incorrectly. This defect is a variance from the given specification.

2. Missing: There was a requirement given by the customer and it was not done. This is a variance from the specifications, an indication that a specification was not implemented, or a requirement of the customer was not noted properly.

3. Extra: A requirement incorporated into the product that was not given by the end customer. This is always a variance from the specification, but may be an attribute desired by the user of the product. However, it is considered a defect because it's a variance from the existing requirements.

4. Which test cases are written first: white boxes or black boxes?5. Normally black box test cases are written first and white box test cases later. In order to write

black box test cases we need the requirement document and, design or project plan. All these documents are easily available at the initial start of the project. White box test cases cannot be started in the initial phase of the project because they need more architecture clarity which is not available at the start of the project. So normally white box test cases are written after black box test cases are written. 

Black box test cases do not require system understanding but white box testing needs more

structural understanding. And structural understanding is clearer i00n the later part of project, i.e., while executing or designing. For black box testing you need to only analyze from the functional perspective which is easily available from a simple requirement document.

Explain Unit Testing, Integration Tests, System Testing and Acceptance Testing?

Unit testing - Testing performed on a single, stand-alone module or unit of code.

Integration Tests - Testing performed on groups of modules to ensure that data and control are passed properly between modules.

System testing - Testing a predetermined combination of tests that, when executed successfully meets requirements.

Acceptance testing - Testing to ensure that the system meets the needs of the organization and the end user or customer (i.e., validates that the right system was built).

Can you explain the concept of defect cascading?

Defect cascading is a defect which is caused by another defect. One defect triggers the other defect. For instance, in the accounting application shown here there is a defect which leads to negative taxation. So the negative taxation defect affects the ledger which in turn affects four other modules.

What is the difference between pilot and beta testing?

The difference between pilot and beta testing is that pilot testing is nothing but actually using the product (limited to some users) and in beta testing we do not input real data, but it's installed at the end customer to validate if the product can be used in production. 

What's the difference between System testing and Acceptance testing?

Acceptance testing checks the system against the "Requirements." It is similar to System testing in that the whole system is checked but the important difference is the change in focus:

System testing checks that the system that was specified has been delivered. Acceptance

testing checks that the system will deliver what was requested. The customer should always do Acceptance testing and not the developer.

The customer knows what is required from the system to achieve value in the business and is the only person qualified to make that judgement. This testing is more about ensuring that the software is delivered as defined by the customer. It's like getting a green light from the customer that the software meets expectations and is ready to be used.

Can you explain regression testing and confirmation testing?

Regression testing is used for regression defects. Regression defects are defects occur when the functionality which was once working normally has stopped working. This is probably because of changes made in the program or the environment. To uncover such kind of defect regression testing is conducted. 

If we fix a defect in an existing application we use confirmation testing to test if the defect is removed. It's very possible because of this defect or changes to the application that other sections of the application are affected. So to ensure that no other section is affected we can use regression testing to confirm this.

How does load testing work for websites?

Websites have software called a web server installed on the server. The user sends a request to the web server and receives a response. So, for instance, when you type www.google.com the web server senses it and sends you the home page as a response. This happens each time you click on a link, do a submit, etc. So if we want to do load testing you need to just multiply these requests and responses "N" times. This is what an automation tool does. It first captures the request and response and then just multiplies it by "N" times and sends it to the web server, which results in load simulation.

So once the tool captures the request and response, we just need to multiply the request and response with the virtual user. Virtual users are logical users which actually simulate the actual physical user by sending in the same request and response. If you want to do load testing with 10,000 users on an application it's practically impossible. But by using the load testing tool you only need to create 1000 virtual users.

Can you explain an Application boundary?

The first step in FPA is to define the boundary. There are two types of major boundaries:

1. Internal Application Boundary2. External Application Boundary

The external application boundary can be identified using the following litmus test:

1. Does it have or will it have any other interface to maintain its data, which was not developed by you?.

2. Does your program have to go through a third party API or layer? In order for your application to interact with the tax department application your code has to interact with the tax department API.

3. The best litmus test is to ask yourself if you have full access to the system. If you have full rights to make changes then it is an internal application boundary, otherwise it is an external application 

4. Can you explain boundary value analysis?5. In some projects there are scenarios where we need to do boundary value testing. For

instance, let's say for a bank application you can withdraw a maximum of 25000 and a minimum of 100. So in boundary value testing we only test the exact boundaries rather than hitting in the middle. That means we only test above the max and below the max. This covers all scenarios. The following figure shows the boundary value testing for the bank application which we just described. TC1 and TC2 are sufficient to test all conditions for the bank. TC3 and TC4 are just duplicate/redundant test cases which really do not add any value to the testing. So by applying proper boundary value fundamentals we can avoid duplicate test cases, which do not add value to the testing.

6. Can you explain exploratory testing?

Exploratory testing is also called adhoc testing, but in reality it's not completely adhoc. Ad hoc testing is an unplanned, unstructured, may be even an impulsive journey through the system with the intent of finding bugs. Exploratory testing is simultaneous learning, test design, and test execution. In other words, exploratory testing is any testing done to the extent that the tester proactively controls the design of the tests as those tests are performed and uses information gained while testing to design better tests. Exploratory testers are not merely keying in random data, but rather testing areas that their experience (or imagination) tells them are important and then going where those tests take them.

Can you explain DRE?

DRE (Defect Removal Efficiency) is a powerful metric used to measure test effectiveness. From this metric we come to know how many bugs we found from the set of bugs which we could have found. The following is the formula for calculating DRE. We need two inputs for calculating this metric: the number of bugs found during development and the number of defects detected at the end user.

But the success of DRE depends on several factors. The following are some of them:

Severity and distribution of bugs must be taken into account. Second, how do we confirm when the customer has found all the bugs. This is normally

achieved by looking at the history of the customer.