Important Links for UGC NET Subjects

I have been in the habit of searching web links on topics I couldn't find much information in books or were too theoretical. In this process, I made a list of URLs which contain useful stuff in a good language. I am posting these URLs for all my friends who are aiming to crack the NUT errrrrrr NET :-)
I am not boasting of providing best of links but just want to say I got good help from these URLs.

All the best for December' 15 Exam!

NETWORKING:
http://www.perihel.at/2/basics/  (Very good site to learn at deep level)
http://ckp.made-it.com/ (Good link to learn OSI layer 1 & 2)
http://flylib.com/books/en/2.567.1.44/1/
http://www.differencebetween.com/category/technology/it/

Database:
http://djitz.com/guides/how-to-check-if-a-relation-is-in-bcnf-3nf-or-both/
http://www.youtube.com/watch?v=IiEAfRoHIH8&feature=endscreen&NR=1
http://www.differencebetween.com/difference-between-deferred-update-and-vs-immediate-update/
www.eecs.umich.edu/~teorey/lec.notes.pdf

OS:
http://www.personal.kent.edu/~rmuhamma/OpSystems/os.html
http://www.computerhope.com/unix/utr.htm
http://www.indiabix.com/computer-science/operating-systems-concepts/015001
http://www.chibios.org/dokuwiki/doku.php?id=chibios:articles:semaphores_mutexes
http://www1bpt.bridgeport.edu/sed/projects/cs503/Spring_2001/kode/os/deadlock.htm#
http://all-operatingsystems.blogspot.in/2009/10/multiple-choice-questions-on-operating_8948.html
http://www-ist.massey.ac.nz/csnotes/355/lectures/monitors.pdf
http://siber.cankaya.edu.tr/ozdogan/OperatingSystems/ceng328/node197.html

Automata Notes:
http://cs.union.edu/~striegnk/learn-prolog-now/html/node55.html#sec.l7.cfg
http://www.cs.uky.edu/~lewis/texts/theory/languages/cfl-prop.pdf
http://www.cs.uky.edu/~lewis/texts/theory/automata/lb-auto.pdf

http://courses.cs.vt.edu/~cs4114/
http://www.cs.cmu.edu/~eugene/teach/auto01/notes/
http://www.tenouk.com/visualcplusmfc/visualcplusmfc16.html  (Great site for learning Windows Programming)
http://www.youtube.com/watch?v=IhyEGNn-7Uo&feature=related  (Video on Turing Machine)
http://www.youtube.com/watch?v=id7k6gUkZ8Y&feature=relmfu  (Video on NP-Complete Problem)
http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT-KANPUR/compiler-desing/ui/Course_home-4.htm
http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT-%20Guwahati/afl/index.htm
http://www.bukisa.com/articles/393888_basics-of-message-handling-in-windows#ixzz1eRNPTl6O
http://www.di.uevora.pt/~lmr/syscalls.html
http://www.psexam.com/Database-Management-System-and-Design/dbms-and-design-mcq-set-3.html

Computer Organization:
http://blogs-static.maktoob.com/wp-content/blogs.dir//67186/files//2010/02/digital-electronics-introduction.pdf

Software Engg.
http://www.smartdraw.com/uml-diagram/
http://users.csc.calpoly.edu/~jdalbey/SWE/Design/STDexamples.html
http://www2.cs.unibw.de/tools/DiaGenDiaMeta/img/nsd_t.png   (It has Nassi-Shneiderman Diagrams)

Computer Graphics:
http://marintellect.com/help_topics/graphics/index.html
http://www.slideshare.net/askme/chapter-10-280485?src=related_normal&rel=2953874

Computer Organization & Microprocessor:
http://www.allaboutcircuits.com/
http://ptucse.loremate.com/sp/node/6    (Imp Q & A)
http://www.ustudy.in/node/3036 ( Learning gates & circuits)

AI/ADA:
http://www.personal.kent.edu/~rmuhamma/Algorithms/algorithm.html

C/C++/Data Structure:
https://www.securecoding.cert.org/confluence/display/seccode/STR36-C.+Do+not+specify+the+bound+of+a+character+array+initialized+with+a+string+literalhttp://www.cs.umd.edu/class/fall2006/cmsc351/notes/
http://www.youtube.com/watch?v=eWeqqVpgNPg   (Video on Trees traversals)
http://faculty.cs.niu.edu/~freedman/340/340notes/340hash.htm  (Hashing Technique)
http://www.geeksforgeeks.org/g-fact-37/ (Virtual destructor)
http://www.geeksforgeeks.org/pure-virtual-destructor-c/

Probability Theory, Permutation Combination:
http://iim-cat-questions-answers.2iim.com/quant_math_sample_problems/permutation_combination_probability/
http://homes.ieu.edu.tr/uufuktepe/m144/logic/1.htm (Propositions)
http://mathworld.wolfram.com

Option-V Unix/Windows:
http://pravin.insanitybegins.com/win32/lesson2  (6 functions for window creation)

Online Objective Tests:

http://www.careerride.com/Online-practice-test.aspx

UGC NET/SET Exam: Some Ideas for success

Friends,

I want to share some of my ideas on NET/SET preparation. I have done MCA and qualified UGC NET exam twice and SET(H.P.)-2013 exam.

The very first time I appeared in NET exam simply to know the pattern of the exam and I didn't prepare much. At that time, exam had subjective pattern. I was able to clear Paper I and Paper II but I could not clear paper III. Still, I was very happy that I cleared first 2 papers. Then, I appeared again, then again. In total 5 of my efforts, I was not able to clear Paper III. In my 4th and 5th attempt, pattern of the paper had become totally objective. Still, I was not able to clear paper III.

I had started losing my faith in myself and I decided to opt out of Dec' 13 NET Exam and preferred to sit in another exam on the same date. I believed that the same story will get repeated. But one good thing I did was that before Dec' 13 exam, Himachal Pradesh Public Service commission had announced SET/SLET exam for the state universities/colleges. I applied for the exam and had appeared in the exam on November 17, 2013. The result of the exam was announced on  March 14, 2014 and I was declared qualified! WOW!!

The success in SET gave me much needed high and faith in myself. The point here is, we throw seeds on the land without bothering about which seed will bore fruits and when. Our efforts in one direction may show result somewhere else. The time I devoted in preparation of NET helped me to crack SET exam. Further, the success in SET exam enthused me and started preparing in a more determined manner. SET is limited in scope and a bit easier than NET. But success in this exam rekindled my faith in myself that NET too is not far and can be cracked with some more planning.

And the result was that I was able to qualify December 2014 exam. For the first time, I Cracked the "hard NUT" called UGC NET.

If one is failing 3 or more times in NET, it is quite possible that one will get disappointed and will lose one's confidence. To uplift one's spirits, focusing on some other exam/objective (for time being) of your chosen career will help you to forget the stress you might have been facing due to rejection in NET. You may choose to focus on some other competition exams for computer teacher/lecturers like CTET, SET, KV schools exams etc. whichever is announced in the time frame. Believe me, these exams can be cracked more easily than NET.

Your sole objective may be NET only, but if you succeed in other exams I have mentioned, it will lift your morale and will give birth to an enthusiastic mindset which is very crucial for cracking exams like NET.

PLEASE post your ideas (If whatever I have mentioned is right or wrong)..

Some useful stuff on UNIX and Network Security

1) Secure Shell (SSH) is a UNIX-based command interface and protocol for securely getting access to a remote computer. It is a suite of three utilities - slogin, ssh, and scp - that are secure versions of the earlier UNIX utilities, rlogin, rsh, and rcp. SSH uses RSA public key cryptography for both connection and authentication. Its default encryption algorithm is IDEA (International Data Encryption Algorithm).

2) IDEA encryption algorithm was developed at ETH in Zurich, Switzerland. It uses a block cipher with a 128-bit key, and is considered to be very secure and among the best publicly known algorithms.

3) A spam cocktail (or anti-spam cocktail) is the use of several different technologies in combination to successfully identify and minimize spam. It puts each e-mail message through a series of tests that provides a numeric score showing how likely the message is to be spam. Scores are computed and the message is assigned a probability rating.

4) Non-repudiation is the assurance that someone cannot deny something. Typically, non-repudiation refers to the ability to ensure that a party to a contract or a communication cannot deny the authenticity of their signature on a document or the sending of a message that they originated.

5) Echelon is an officially unacknowledged U.S.-led global spy network that operates an automated system for the interception and relay of electronic communications. Monitored transmissions are said to include up to 3 billion communications daily, including all the telephone calls, e-mail messages, faxes, satellite transmissions, and Internet downloads of both public and private organizations and citizens worldwide. Led by the U.S. National Security Agency (NSA).

6) On UNIX systems, snort is an open source network intrusion detection system (NIDS). Snort is a packet sniffer that monitors network traffic in real time, scrutinizing each packet closely to detect a dangerous payload or suspicious anomalies. Through protocol analysis and content searching and matching, Snort detects attack methods, including denial of service, buffer overflow, CGI attacks, stealth port scans, and SMB probes.

7) Server Message Block (SMB) is a network protocol mostly used by Windows-based computers that allows systems within the same network to share files. It allows computers connected to the same network or domain to access files from other local computers as easily as if they were on the computer's local hard drive.

8 ) Greynet (or graynet)) is a term for the use of unauthorized applications on a corporate network. A greynet application is a network-based program that corporate network users download and install without permission from their company's IT department. They introduce security risks, including client code vulnerabilities and new avenues for attack, and can lead to data loss and property or identity theft.

9) Munging is the deliberate alteration of an e-mail address on a Web page to hide the address from spambot programs that examine the Internet for e-mail addresses. Such addresses are easily recognized because they contain the @ symbol. Address munges should allow a real person reading the content (as opposed to a program scanning it) to easily deduce the true e-mail address.

Here is an example of a munged address: editor at xyz dot com.

10) Traceroute is a utility that records the route (the specific gateway computers at each hop) through the Internet between your computer and a specified destination computer. It also calculates and displays the amount of time each hop took. This utility initiates the sending of a packet using Internet Control Message Protocol (ICMP), including in the packet a time limit value (known as the "time to live" (TTL) that is designed to be exceeded by the first router that receives it, which will return a Time Exceeded message. This enables traceroute to determine the time required for the hop to the first router. Increasing the time limit value, it resends the packet so that it will reach the second router in the path to the destination, which returns another Time Exceeded message, and so forth. Finally, traceroute determines when the packet has reached the destination.

11) Intrusion Detection Systems (IDS) is a passive way to monitor a network and its computers. The program keep a watch on all inbound and outbound traffic and looks for attacks. It sends an alert when it finds something unusual. It can only act on known intrusion signatures. Intrusion Detection Systems (IPS) tools perform active, in-line monitoring and can prevent attacks by known and unknown sources.

12) An IDS is not a substitute for a firewall. A firewall can stop intrusions like an IDS but is not able to monitor activity from inside the network.

13) Honey Pot Systems are decoy servers or systems setup to gather information regarding an attacker or intruder into your system. It can be setup inside, outside or in the DMZ of a firewall design or even in all of the location.

14) Port Scanning identifies open doors to a computer. There is no way to stop someone from port scanning your computer while you are on the Internet because accessing an Internet server opens a port, which opens a door to your computer. Types of port scans:
vanilla: the scanner attempts to connect to all 65,535 ports
strobe: a more focused scan looking only for known services to exploit
fragmented packets: the scanner sends packet fragments that get through simple packet filters in a firewall
UDP: the scanner looks for open UDP ports
sweep: the scanner connects to the same port on more than one machine
FTP bounce: the scanner goes through an FTP server in order to disguise the source of the scan.
stealth scan: the scanner blocks the scanned computer from recording the port scan activities.

15) Types of firewall techniques:
Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.
Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation.
Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking.
Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses.

Answer Keys for June 2013 - Computer Science

After researching different resources, I am able to compile Answer keys for June 2013 paper of Computer Science. First, I am posting keys for Paper III as this paper is tougher to clear than othet two papers. I am sure 90% of the answers I have given are correct.
1. A
2. D
3. C
4. B
5. B
6. B
7. C
8. D
9. A or B
10. D
11. C
12. --
13. D
14. D
15. --
16. A
17. A
18. B
19. C
20. D
21. D
22. B
23. C
24. A
25. --
26. A
27. B
28. C
29. D
30. A
31. B
32. A
33. C
34. D
35. D
36. --
37. --
38. B
39. C
40. B
41. C
42. D
43. --
44. B
45. A
46. C
47. B
48. A
49. B
50. A
51. C
52. A
53. A
54. D
55. A
56. --
57. A
58. B
59. --
60. D
61. B
62. A
63. B
64. C
65. B
66. D
67. --
68. D
69. C
70. C
71. B
72. C
73. C
74. --
75. --

Useful Q & A on Networking - Part 1

Q 1. What happens at every layer of the OSI model when we type "www.google.com" in the browser? 

Ans. The following sequence of steps takes place every time we type the name of a website in a browser->
1) Your PC will need to resolve "www.google.com" to an IP address. It will therefore need to send a 
query to your DNS server ( usually your ISP's DNS).

2) The PC constructs a DNS query packet with a destination IP address equal to your DNS server 
and a destination MAC address of your router (gateway).

3) The DNS query process begins to resolve the IP address of the given URL.

4) Once your PC (web browser application) receives the IP address of the destination web server, it will construct a HTTP GET request and send it to Google's web server. (As per OSI model at application layer [layer 7] application software which is client web browser now know the IP address of google.com). After that it pass that information down to presentation layer.

5) Presentation layer[ layer 6] converts that HTTP request into a standard format which is HTTP format so that the other layers can understand.and pass that information down to session layer.

6) Session layer[ layer 5] at client side creates session for www.google.com which is HTTP session so that it can be separated from other sessions.and pass that information down to transport Layer.

7) Transport Layer[ layer 4]  at client side chooses TCP for every HTTP session which is reliable connection which creates virtual connection by using three way hand-shake before sending actual data [HTTP Request]. This layer also prepares segments by adding source and destination port number. Source port is chosen by upper layer which is random number range from 1024 to 65535  and destination port number is here 80, which is well known port number used for HTTP services.

Layer 4 assign source port number to distinguish the web browser application from every other program running on computer and it also used to identify which application should receive return traffic. The destination port number is used to make sure that messages coming from web browser gets and sent to web server program running on the server and is not grabbed by other program. After preparing segment, layer 4 at client side pass that information down to network layer.

8) Network Layer [ layer 3] at client side  prepares packet by adding source and destination IP address. It also check whether destination IP address is on local network or it is on remote network. If it is on local network it checks ARP cache to find mac address of local device. If cache is empty it sends ARP message to resolve IP address into MAC address. Here the device is on remote network so client PC sends ARP to find MAC address of default gate way [192.168.1.1]. Every devices on that network segment gets that ARP request because as it layer 2 broadcast message destined for all devices on that broadcast domain but only the default gateway, which is 192.168.1.1, replies with its MAC address. Then network layer passes this information down to data link layer.

9) Data link layer[ layer 2]  prepares frame by adding source and destination MAC address of default gate way[192.168.1.1]. It also rund CRC which simply checks the data and frame header bits and add that result in to frame check sequence (FCS) field. Then, passes this information down to Physical layer.

10) Physical layer[ layer 1]: converts all this information in 1's and 0's and sends it to destination device using Ethernet cable.

11) Google's Web server will reply and start sending your application the necessary data using TCP session.

12) The application will start to draw and present the website on your screen.

At the server side, i.e. Google:

1) At Physical layer, server receives the bits. Layer 2 of server builds frames and runs CRC and checks answer with FCS field. If answer didn't match then the frame is discarded. If it matches then the destination MAC address is checked. Here, destination MAC address is right, so it checks Ethernet type field to find the protocol used at network layer (which is IP). It retrieves the packet from the frame and gives to IP at network layer.

2) Network layer checks destination IP address and in our case it matches so it checks protocol type field to find the protocol used at Layer 4 (which is TCP). Now network layer of server sends all information up to TCP at layer 4.

3) At transport layer, destination port number is checked which is well know port number 80, which is destined to web server application running on that particular server i.e. in our case www.google.com. So it passes all those information up to google web server. Google web server sends acknowledgement message to client to ensure that it has received its request. Finally, it sends the web page in the form of packet by packet over the network to client. This information gives google web page to our client web browser.