Open source doesn't just mean access to the source code. The distribution terms of open-source software must fulfill with the following criteria:
1. Free Redistribution
The license shall not restrict any party from selling or giving away the software as a component of an aggregate software distribution containing programs from several different sources. The license shall not require a royalty or other fee for such sale.
2. Source Code
The program must include source code, and must allow distribution in source code as well as compiled form. Where some form of a product is not distributed with source code, there must be a well-publicized means of obtaining the source code for no more than a reasonable reproduction cost preferably, downloading via the Internet without charge. The source code must be the preferred form in which a programmer would modify the program. Deliberately obfuscated source code is not allowed. Intermediate forms such as the output of a preprocessor or translator are not allowed.
3. Derived Works
The license must allow modifications and derived works, and must allow them to be distributed under the same terms as the license of the original software.
4. Integrity of the Author's Source Code
The license may restrict source-code from being distributed in modified form only if the license allows the distribution of "patch files" with the source code for the purpose of modifying the program at build time. The license must explicitly permit distribution of software built from modified source code. The license may require derived works to carry a different name or version number from the original software.
5. No Discrimination against Persons or Groups
The license must not discriminate against any person or group of persons.
6. No Discrimination against Fields of Endeavor
The license must not restrict anyone from making use of the program in a specific field of endeavor. For example, it may not restrict the program from being used in a business, or from being used for genetic research.
7. Distribution of License
The rights attached to the program must apply to all to whom the program is redistributed without the need for execution of an additional license by those parties.
8. License Must Not Be Specific to a Product
The rights attached to the program must not depend on the program's being part of a particular software distribution. If the program is extracted from that distribution and used or distributed within the terms of the program's license, all parties to whom the program is redistributed should have the same rights as those that are granted in conjunction with the original software distribution.
9. License Must Not Restrict Other Software
The license must not place restrictions on other software that is distributed along with the licensed software. For example, the license must not insist that all other programs distributed on the same medium must be open-source software.
10. License Must Be Technology-Neutral
No provision of the license may be predicated on any individual technology or style of interface.
Sunday, December 19, 2010
SOURCES OF OSS
The ideals and philosophy of open source is threatened by the 'marriage of convenience' of open source with the commercial world, which makes a strong case for the traditional free software movement. It is, perhaps, taking the adage 'making a case to the commercial world' too far. Eventually, there may such a blend of both the open source movement and the commercial world that we are not able to distinguish between the two. The enemy would have sneaked in unawares and made sport of all ideals and philosophies of the open source movement.
These are all valid concerns that the open source community needs to address. In closing I have a word of advise for the open source movement from my grandmother which I find appropriate - If you don't know where you're going, remember where you're coming from.
Sources
1. Wikipedia Encyclopedia
2. Open Source Initiative
3. The Free Software Foundation
4. The Apache Software Foundation
5. Richard M. Stallman in "Open Sources: Voices from the Open Source Revolution"
6. John Udell "Open Source Citizenship".
These are all valid concerns that the open source community needs to address. In closing I have a word of advise for the open source movement from my grandmother which I find appropriate - If you don't know where you're going, remember where you're coming from.
Sources
1. Wikipedia Encyclopedia
2. Open Source Initiative
3. The Free Software Foundation
4. The Apache Software Foundation
5. Richard M. Stallman in "Open Sources: Voices from the Open Source Revolution"
6. John Udell "Open Source Citizenship".
licensing of OPENSOURCE SOFTWARE
Further, any derivative work need not be free and one can charge for it as you would for proprietary software.The subtle licensing criteria between open source generally and free software is further highlighted when you consider that some licenses are not compatible. For instance, programs/source code distributed under PHP License is not compatible with GNU GPL since GNU GPL is a copyleft license. Which raises a couple of licensing issues:
(1)Why are there different criteria under different licenses for open source software? Presently, there are about 54 licenses certified by OSI as open source - a tribute to OSI's philosophy - which many now see as an unnecessary proliferation of licenses, an issue that forced OSI to admit that -"OSI's approach on the development and distribution problems involved building as many different bridges as possible between developers and the corporate world. In doing this, we accepted a proliferation of new licenses. This is a problem in that although physical bridges between communities don't interfere with each other, licenses do. Interference between different open-source licenses is now perceived as a sufficiently serious problem that OSI has become as a victim of its own earlier success."
To address the issue of proliferation, OSI plans to take all existing OSI approved licenses and group them into three tiers: (i) preferred, (ii) recommended but not preferred, and (iii) not recommended. This is likely to create more confusion. One would then ask why an OSI certified license would be OSI "not recommended" license. Would a 'not recommended' tag not be deemed as de-approval (though OSI says its not). It would be 'preferable' not to have certified such license as OSI approved in the first place.
(2) Why are some licenses not compatible with others? We may well appreciate that compatibility goes beyond the issue of license proliferation. For example, the FSF considers all versions of the Apache License incompatible with Version 2 of the GNU GPL. About version 2.0 of the Apache License, they say:
"The Apache Software License is incompatible with the GPL because it has a specific requirement that is not in the GPL: it has certain patent termination cases that the GPL does not require. (We don't think those patent termination cases are inherently a bad idea, but nonetheless they are incompatible with the GNU GPL.)"
Apache Software Foundation (ASF), which publishes the Apache License, has adequately replied to FSF's statement, stating that ASF does not share the same goals as FSF. For the time being, the controversy rages on. Compatibility is really a relationship issue; free software movement and the open source movement can be likened to two political camps within the free software community. While it can be argued that GNU GPL is not compatible with a number of licenses because the philosophy behind GNU GPL is freedom - which proponents of free software have cried themselves hoarse from the rooftops for decades now - GNU GPL itself publishes a list of free/open source software licenses that are GPL incompatible, distinguishing between non-copyleft and 'not strong copyleft'. Even, copyleft licenses like xinetd have also not been spared and was held incompatible because it places extra restrictions on redistribution of modified versions that contradict the redistribution requirements in the GPL. Don't they share the same goals? Yet the free software movement has complained that to be lumped together with open source software is restrictive for free software since open source software allegedly has a much weaker criterion than free software. Then one may ask, what is the criteria for determining compatibility with GNU GPL even for copyleft free software licenses? At least FSF is not intending to classify licenses in the same manner as OSI - for now.
(3) Don't some of these licenses support a 'one way' street attitude described by John Udell in the Open Source Citizenship where developers are encouraged to take and not give back to the community. Or it could be akin to the situation described by Stallman where commercial developers invited to the "Open Source Developers Day" meeting in August 1998 said they intend to make only a part of their work free software (or open source) since the focus of their business is on developing proprietary add-ons (software or manuals) to sell to the users of the free software. According to Stallman, those developers requested that this should be regarded as legitimate, as part of the community, because some of the money is donated to free software development. Whichever way you look at it, it is a dangerous trend for the future of open source software.
(1)Why are there different criteria under different licenses for open source software? Presently, there are about 54 licenses certified by OSI as open source - a tribute to OSI's philosophy - which many now see as an unnecessary proliferation of licenses, an issue that forced OSI to admit that -"OSI's approach on the development and distribution problems involved building as many different bridges as possible between developers and the corporate world. In doing this, we accepted a proliferation of new licenses. This is a problem in that although physical bridges between communities don't interfere with each other, licenses do. Interference between different open-source licenses is now perceived as a sufficiently serious problem that OSI has become as a victim of its own earlier success."
To address the issue of proliferation, OSI plans to take all existing OSI approved licenses and group them into three tiers: (i) preferred, (ii) recommended but not preferred, and (iii) not recommended. This is likely to create more confusion. One would then ask why an OSI certified license would be OSI "not recommended" license. Would a 'not recommended' tag not be deemed as de-approval (though OSI says its not). It would be 'preferable' not to have certified such license as OSI approved in the first place.
(2) Why are some licenses not compatible with others? We may well appreciate that compatibility goes beyond the issue of license proliferation. For example, the FSF considers all versions of the Apache License incompatible with Version 2 of the GNU GPL. About version 2.0 of the Apache License, they say:
"The Apache Software License is incompatible with the GPL because it has a specific requirement that is not in the GPL: it has certain patent termination cases that the GPL does not require. (We don't think those patent termination cases are inherently a bad idea, but nonetheless they are incompatible with the GNU GPL.)"
Apache Software Foundation (ASF), which publishes the Apache License, has adequately replied to FSF's statement, stating that ASF does not share the same goals as FSF. For the time being, the controversy rages on. Compatibility is really a relationship issue; free software movement and the open source movement can be likened to two political camps within the free software community. While it can be argued that GNU GPL is not compatible with a number of licenses because the philosophy behind GNU GPL is freedom - which proponents of free software have cried themselves hoarse from the rooftops for decades now - GNU GPL itself publishes a list of free/open source software licenses that are GPL incompatible, distinguishing between non-copyleft and 'not strong copyleft'. Even, copyleft licenses like xinetd have also not been spared and was held incompatible because it places extra restrictions on redistribution of modified versions that contradict the redistribution requirements in the GPL. Don't they share the same goals? Yet the free software movement has complained that to be lumped together with open source software is restrictive for free software since open source software allegedly has a much weaker criterion than free software. Then one may ask, what is the criteria for determining compatibility with GNU GPL even for copyleft free software licenses? At least FSF is not intending to classify licenses in the same manner as OSI - for now.
(3) Don't some of these licenses support a 'one way' street attitude described by John Udell in the Open Source Citizenship where developers are encouraged to take and not give back to the community. Or it could be akin to the situation described by Stallman where commercial developers invited to the "Open Source Developers Day" meeting in August 1998 said they intend to make only a part of their work free software (or open source) since the focus of their business is on developing proprietary add-ons (software or manuals) to sell to the users of the free software. According to Stallman, those developers requested that this should be regarded as legitimate, as part of the community, because some of the money is donated to free software development. Whichever way you look at it, it is a dangerous trend for the future of open source software.
critics for open source software
Critics of open source say that open source fosters an ambiguity of a different kind, in that it confuses the mere availability of the source code with the freedom to use, modify, and redistribute it. But open source doesn't just mean access to the source code; the use of open-source software must comply with a number of criteria including as to re-distribution, depending on the license under which it is distributed.
Different licenses require different criteria. For instance, under the GNU General Public License (GPL) published by the Free Software Foundation (FSF) for licensing free software, any work based on the program or any other derivative work must be licensed as a whole at no charge at all to all third parties under the terms of the GNU GPL, whereas an Apache License does not require derivative works to be open source. You can add your own copyright statement to modifications of a source code under Apache License and provide additional or different license terms and conditions for use, reproduction, or distribution of your modifications, or for any derivative works as a whole, provided your use, reproduction, and distribution of the work otherwise complies with conditions of the Apache License. Similarly, there is no requirement that any derivative work created under an Academic Free License (AFL) or a Berkeley Software Distribution (BSD) License, should be distributed at all, or for free if distributed.
Different licenses require different criteria. For instance, under the GNU General Public License (GPL) published by the Free Software Foundation (FSF) for licensing free software, any work based on the program or any other derivative work must be licensed as a whole at no charge at all to all third parties under the terms of the GNU GPL, whereas an Apache License does not require derivative works to be open source. You can add your own copyright statement to modifications of a source code under Apache License and provide additional or different license terms and conditions for use, reproduction, or distribution of your modifications, or for any derivative works as a whole, provided your use, reproduction, and distribution of the work otherwise complies with conditions of the Apache License. Similarly, there is no requirement that any derivative work created under an Academic Free License (AFL) or a Berkeley Software Distribution (BSD) License, should be distributed at all, or for free if distributed.
open source software asfects
The Wikipedia Encyclopedia describes open source as "practices in production and development that promote access to the end product's sources." Before the label open source was coined, developers and producers used a variety of phrases to describe the concept. In fact, earlier researchers used a process which is similar to open standards to develop telecommunication network protocols. Characterized by contemporary open source work, this collaborative process led to the birth of the Internet in 1969. Its application to software gained popularity with the emergence of the Internet. It is said that the open source label came out of a strategy session held at Palo Alto, California, in reaction to Netscape's announcement that it planned to release the source code for its browser Navigator.
The politically correct version is that to clarify a potential confusion caused by the ambiguity of the word "free", so that the perception of free software is not anti-commercial, the label open source (contributed by Chris Peterson) stuck. The official version is that it was to shed the confrontational attitude that had been associated with free software in the past and sell the idea on pragmatic, business case grounds to the commercial world. Whatever it may be, Netscape listened and released their code as open source under the name of Mozilla. That was the beginning of the contemporary open source movement, whose main champion today allegedly is the Open Source Initiative ("OSI") which makes and continues to make a case for the open source software to the commercial world. Consequently, we have seen the application of the open source philosophy in other fields inlcuding biotechnology. Linus Torvalds, a finnish software engineer who initiated the development of the Linux kernel went as far as saying "the future is open source everything".
According to the OSI, the case for open source software is simple - free access to read, redistribute and modify the source code of a piece of software results in a rapid evolutionary process that produces better software. Advocates of open source argue that when programmers can read, redistribute, and modify the source code for a piece of software, the software evolves. People improve it, people adapt it, people fix bugs. And this can happen at a speed that, if one is used to the slow pace of conventional software development, seems astonishing.
However, evangelists of free software have been at pains to clarify that open source software is not synonymous with free software. The philosophy of the open source movement is based on practicality and not ethical considerations while free software is based on freedom, not price. Borrowing from Richard M. Stallman, "free software" and "open source" describe the same category of software, more or less, but say different things about the software, and about values. While the two are not synonymous, both have a common enemy - proprietary software.
The politically correct version is that to clarify a potential confusion caused by the ambiguity of the word "free", so that the perception of free software is not anti-commercial, the label open source (contributed by Chris Peterson) stuck. The official version is that it was to shed the confrontational attitude that had been associated with free software in the past and sell the idea on pragmatic, business case grounds to the commercial world. Whatever it may be, Netscape listened and released their code as open source under the name of Mozilla. That was the beginning of the contemporary open source movement, whose main champion today allegedly is the Open Source Initiative ("OSI") which makes and continues to make a case for the open source software to the commercial world. Consequently, we have seen the application of the open source philosophy in other fields inlcuding biotechnology. Linus Torvalds, a finnish software engineer who initiated the development of the Linux kernel went as far as saying "the future is open source everything".
According to the OSI, the case for open source software is simple - free access to read, redistribute and modify the source code of a piece of software results in a rapid evolutionary process that produces better software. Advocates of open source argue that when programmers can read, redistribute, and modify the source code for a piece of software, the software evolves. People improve it, people adapt it, people fix bugs. And this can happen at a speed that, if one is used to the slow pace of conventional software development, seems astonishing.
However, evangelists of free software have been at pains to clarify that open source software is not synonymous with free software. The philosophy of the open source movement is based on practicality and not ethical considerations while free software is based on freedom, not price. Borrowing from Richard M. Stallman, "free software" and "open source" describe the same category of software, more or less, but say different things about the software, and about values. While the two are not synonymous, both have a common enemy - proprietary software.
Tuesday, November 9, 2010
important computer networking 2 marks
UNIT I
Data communications
1. Explain ISO/OSI reference model.
_ Physical layer
_ Data link layer
_ Network layer
_ Transport layer
_ Session layer
_ Presentation layer
_ Application layer
2. Explain the topologies of the network.
_ Mesh topology
_ Star topology
_ Tree topology
_ Bus topology
_ Ring topology
3. Explain the categories of networks.
_ Local Area Network(LAN)
_ Metropolitan Area Network(MAN)
_ Wide Area Network(WAN)
4. Explain coaxial cable & fiber optics.
_ Coaxial cable
_ Coaxial cable standards
_ Coaxial cable connectors
_ Fiber optics
_ Propagation modes
_ Fiber sizes
_ Cable composition
_ Light sources for optical cable
_ Fiber optic connectors
_ Advantages & disadvantages of optical fiber
5. Explain line coding (digital to digital conversion).
_ Unipolar
_ DC component
_ Synchronization
_ Polar
_ Non return to zero(NRZ)
_ NRZ-L
_ NRZ-I
_ Return to zero
_ Biphase
_ Manchester
_ Differential Manchester
_ Bipolar
_ Alternate Mark Inversion(AMI)
_ Bipolar 8-zero substitution(B8ZS)
_ High-Density Bipolar 3(HDB3)
UNIT II
Data link layer
1. Explain error detection and error correction techniques.
_ Types of errors
_ Single bit error
_ Burst error
_ Error detection
_ Vertical redundancy check(VRC)
_ Longitudinal redundancy check(LRC)
_ Cyclic redundancy check(CRC)
_ Checksum
_ Error correction
_ Single-bit error correction
_ Hamming code
_ Burst error correction
2. Explain error control mechanism.
_ Stop and wait ARQ
_ Sliding window ARQ
_ Go back-n
_ Selective-reject
3. Explain the flow control mechanism
_ Stop and wait
_ Sliding window.
4. Explain the timers and time registers in FDDI.
Time registers
_ Synchronous allocation(SA)
_ Target token rotation time(TTRT)
_ Absolute maximum time(AMT)
_ Timers
_ Token rotation timer(TRT)
_ Token holding timer(THT)
5. Explain about Ethernet.
_ Access method :CSMA/CD
_ Addressing
_ Electrical specification
_ Frame format
_ Implementation:
_ 10 base 5 :Thick Ethernet
_ 10 base 2 :Thin Ethernet
_ 10 base T :Twisted-pair Ethernet
_ 1 base 5 :Star LAN
6. Explain the frame format for token ring and token bus.
_ Access method: Token passing
_ Priority and reservation
_ Time limits
_ Monitor stations
7. Explain about HDLC.
_ Station types:
_ Primary station
_ Secondary station
_ Configurations:
_ Unbalanced configuration
_ Symmetrical configuration
_ Balanced configuration
_ Modes of communication:
_ Normal Response Mode(NRM)
_ Asynchronous Response Mode(ARM)
_ Asynchronous Balanced Mode(ABM)
_ Frames :
_ Flag field
_ Address field
_ Control field
_ Information field
_ FCS field
UNIT III
Network layer
1. Explain the two approaches of packet switching techniques.
_ Datagram approach
_ Virtual circuit approach
_ Switched virtual circuit(SVC)
_ Permanent virtual circuit(PVC)
_ Circuit – switched connection versus virtual – circuit connection
_ Path versus route
_ Dedicated versus shared
2. Explain IP addressing method.
_ Internetwork protocol (IP)
_ Datagram
_ Addressing
_ Classes
_ Dotted decimal notation
_ A sample internet
3. Define routing & explain distance vector routing and link state routing.
_ Distance vector routing
_ Sharing information
_ Routing table
_ Creating the table
_ Updating the table
_ Updating algorithm
_ Link state routing
_ Information sharing
_ Packet cost
_ Link state packet
_ Getting information about neighbors
_ Initialization
_ Link state database
4. Define bridge and explain the type of bridges.
_ Bridges
_ Types of bridges
_ Simple bridge
_ Multiport bridge
_ Transparent bridge
5. Explain subnetting
_ Subnetting
_ Three levels of hierarchy
_ Masking
_ Masks without subnetting
_ Masks with subnetting
_ Finding the subnetwork address
_ Boundary level masking
_ Non-boundary level masking
6. Write short notes about repeaters, routers and gateways.
_ Repeaters
_ Routers
_ Routing concepts
_ Least-cost routing
_ Non adaptive routing
_ Adaptive routing
_ Packet lifetime
_ Gateways
UNIT IV
Transport layer
1. Explain the duties of transport layer.
End to end delivery
Addressing
Reliable delivery
• Error control
• Sequence control
• Loss control
• Duplication control
Flow control
Multiplexing
2. Explain socket in detail.
• Introduction
• Explanation
• program
3. Explain UDP & TCP.
_ User Datagram Protocol(UDP)
_ Source port address
_ Destination port address
_ Total length
_ Checksum
_ Transmission Control Protocol(TCP)
_ Source port address
_ Destination port address
_ Sequence number
_ Acknowledgement number
_ Header length
_ Reserved
_ Control
_ Window size
_ Check sum
_ Urgent pointer
_ Options and padding
4. Explain about congestion control.
_ Congestion avoidance
_ BECN
_ FECN
_ Four situations
_ Discarding
5. Explain leaky bucket and token bucket algorithm
_ Leaky bucket algorithm
_ Leaky bucket
_ Switch controlling the output rate
_ Flowchart
UNIT V
Application Layer
1. Explain the functions of SMTP.
• System for sending messages to other computer users based on e-mail
addresses. SMTP provides mail exchange between users on the same
or different computers.
• User Agent
• Mail Transfer Agent
• Multipurpose Internet Mail Extensions
• Post Office Protocol
2. Write short notes on FTP.
• Transfer a file from one system to another.
• TCP connections
• Basic model of FTP
3. Explain about HTTP.
• HTTP transactions
• HTTP messages
• URL
4. Explain the WWW in detail.
• Hypertext & Hypermedia
• Browser Architecture
• Categories of Web Documents
• HTML
• CGI
• Java
5. Explain the type of encryption/decryption method.
Conventional Methods:
• Character-Level Encryption: Substitutional & Transpositional
• Bit-Level Encryption: Encoding/Decoding, Permutation, Substitution,
Product, Exclusive-Or & Rotation
Public key Methods
6. Explain about RSA algorithm.
• Public key Encryption technique.
• Encryption algorithm
• Decryption algorithm
• Security in RSA
7. Explain about secret key encryption algorithm.
• Data Encryption Standard
• Algorithm
• Sub key generation
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