Manufacturing and the different phases of life

                      The thing about product process in the world and the and the age of people. This is just a comparison what i think of the worlds manufacturing ability . When i see the stuff in my house mostly, the electronic goods , I think of the manufacturing ability of the Chinese people.  And then compare the phases of the human life. I can see the tenure in the mans life of age 30-40 in which he toiling hard to earn his bread being too monotonous in his job of earning his bread.

                     When I login to the Facebook and  whats-app I see the young innovative age of people in there 20 to 30 being active about there ideas. taking on challenges and trying to make them successful.

                    Thinking of the age of 60 to 80 when the senses are falling apart I see the Japanese. Like the old they have achieved lot in there life they seen all the Ups and downs and gained all the experience in the life. Even they try level hard to make the country build it again again from the natural calamities they know the old age will take them one day but the experience keeps them calm and motivates them to lead through.

                    The Teen age 15 to 20 and you keep on fighting with yourself there is more kind of breakage them to make. the parents money is available you can spend as your wish . Like wise crude seems to be the boon to the middle east and should and they also spend it guns and weapons to hur each other. Always hostile as the  teenagers.

                    And the most calm or some what satisfied years of life are from 40 to 50. you are accustomed to the job and work before you and the things you have done with your life either you are completed doing it or you are now you cant much about it.

                   and finally the the rest of the world south Americans, Indians, and Africans since we are born till we only keep on learning from the world.finally this does not mean what age the world it is a baby of mother earth and will keep learning from each other. 

                

Next thing about Energy Production and its Byproducts

Hello
                   My thoughts regarding the use of fuel, used by mankind over a period of time. Right from staring with the Neanderthal man understands to burn fire wood for his warmth to the use of 21st century fuels like Hydrogen cell, and Uranium.
                 The sale of fuels has been a major source of income from small vendors selling wood stock to the oil exporting countries. the whole of energy landscape is ever changing. We have been burning firewood since long and till the last century we hardly knew the impact and the consequences of burning by products. this meant that we knew how useful this is on Small scale and completely lack the vision of the large scale utilization of the produce fuel.
                 This can be easily seen from the resource utilization of the fuels like crude initially without know to the harmful effects crude as fuel will cause serious constraints like harm to the environment.
this seems to be happening with the current trends suing the battery. We are slowly moving to energy storage options like battery and solar power generation, with the recent launch of the Power wall unit from the Tesla for home users to generate there own energy from the sun. Its good thing to see we reduce the carbon footprint . But this would also mean generation of the tons of waste that will be produce due to the batteries and the wasted solar panels. to be continued.........

Android 4.3 upgrades for Galxy s4

Just know updated my galaxy s4 with the the android update 4.3.
The functionality of the internet browser has improved a lot.
I was thinking that the 650 mb heavy update would take my mobile to the next level '' kitkat'.
Hope galaxy s4 is updated with new operating system soon...
Just feels exciting if new things could improcve it further...

The RAM usage fir the phone has also been decreased which means now my phone could last half an hour more...

Will be updating what more good has happen to my phone...

New functionality for reading mode seems to added what's fun in that remaind a qurey...

Plastic Product marking in injection molding.

Items to be marked 

Plastic parts should be marked. It is desirable that marking should also be made of the grade and materials,

parts if possible. However, if marking is impossible despite changes of marking locations and sizes, 

marking does not have to be performed. 

However, marking should be as visible as possible. 

(a) When the marking size or location would cause loss of function
(b) When there is not enough space
(c) When it would be difficult due to the way of manufacturing such as the opening and closing direction of
the plastic molding die

(d) When it would not be suitable for the product design


 Marking location
Following 1) - 5) below, marking should be performed on as visible locations as possible when disassembling
products manually and separating materials. Visible locations are for example a front face of a product and a convexed
area of the uneven surface. Marking should not be performed on invisible locations.
1) To be shown in locations not hidden by stickers, etc.
2) Priority should be given to the right rather than the left side for plastic parts.
3) Priority should be given to the back rather than the front for plastic parts.
4) Priority should be given to the bottom rather than the top for plastic parts.
5) For container - shaped plastic products, symbols should be placed on the outside, whenever possible.

Possible ways for mold itching the most cost effective way:
http://www.wikihow.com/Acid-Etch-Steel
this also can be used for auto motive plastic products.

The method has its advantages for.

No mold transfer from changes to be made
No high cost machining required.
Marking Locations
Following 1) - 5) below, marking should be performed on as visible locations as possible when disassembling
products manually and separating materials. Visible locations are for example a front face of a product and a con vexed
area of the uneven surface. Marking should not be performed on invisible locations.
1) To be shown in locations not hidden by stickers, etc.
2) Priority should be given to the right rather than the left side for plastic parts.
3) Priority should be given to the back rather than the front for plastic parts.
4) Priority should be given to the bottom rather than the top for plastic parts.
5) For container - shaped plastic products, symbols should be placed on the outside, whenever possible

MODERN TRENDS IN I.C. ENGINES THE BALL PISTON ENGINE

 

MODERN TRENDS IN I.C. ENGINES

THE BALL PISTON ENGINE

ABSTRACT

A  new power machine concept has been designed and analyzed for production, and proof of principle subscale tests have been performed, with positive results. The machine design concept is applicable as a compressor, pump, motor, or engine. Simplicity of design based on spherical ball pistons enables a low moving part count, high power to weight ratio, elimination of valve train and water cooling systems, and perfect dynamic balance.

The new design concept utilizes novel kinematic design to completely eliminate inertial loads that would contribute to sliding friction. Also, low leakage is maintained without piston rings by using a small clearance on the ball piston, resulting in choked flow past the ball. These features provide the potential for an engine with higher efficiency than conventional piston engines. The engine design utilizes existing recent technology to advantage, such as silicon nitride ball pistons, so a large development effort is not required.
The machine having only a small number of moving parts, the design implements a modified version of the tried and proven thermodynamic Otto cycle when used as an engine. Although the small part count is an important advantage, other advantages exist that will give future engineers new-found freedom in tailoring the combustion process. One great advantage is that the stroke magnitude and rate can be different for different strokes in the cycle (i.e., intake, compression, power, and exhaust). This provides the possibility of converting more energy to shaft power by greater expansion during the power stroke compared to the compression stroke.
Another advantage is the ability to complete any even number of strokes per revolution in a single rotor. This effectively multiplies the power output proportionally if the stroke is maintained constant. Current concentration is on 2 and 4 stroke designs, but 8 or 12 or more stroke rotors are feasible, only limited by centrifugal loads at high speeds for a given rotor size. In addition, rotors can be stacked axially to increase power.
Recently, an engineering breakthrough has enabled the virtual elimination of inertial forces that contribute to friction in the ball piston machine. Friction losses are thus low and independent of operating speed, in contrast to conventional piston engines, where friction losses increase with speed. In addition, recent simulated compressor testing has shown that remaining friction can be nearly completely eliminated by hydrodynamic action of lubricant at the ball piston.

 

 

INTRODUCTION

Efforts to develop rotary internal combustion engines have been undertaken in the past, and are continuing. One main advantage to be gained with a rotary engine is reduction of inertial loads and better dynamic balance. The Wankel rotary engine has been the most successful example to date, but sealing problems contributed to its decline. The Hanes rotary engine uses an eccentric circular rotor in a circular chamber with sliding radial vanes. This engine has never been fully tested and commercialized, and has a sealing problem similar to that of the Wankel. A more recent development, the Rand Cam engine , uses axial vanes that slide against cam surfaces to vary chamber volume. Currently under development, it remains to be seen whether the Rand Cam can overcome the sealing problems that are again similar to those of the Wankel.

In the compressor and pump arena, reduction of reciprocating mass in positive displacement machines has always been an objective, and has been achieved most effectively by lobe, gear, sliding vane, liquid ring, and screw compressors and pumps  but at the cost of hardware complexity or higher losses. Lobe, gear, and screw machines have relatively complex rotating element shapes and friction losses. Sliding vane machines have sealing and friction issues. Liquid ring compressors have fluid turbulence losses. The new design concept of the Ball Piston Engine uses a different approach that has many advantages, including low part count and simplicity of design, very low friction, low heat loss, high power to weight ratio, perfect dynamic balance, and cycle thermodynamic tailoring capability. These aspects will be discussed in more detail below.

---

THE DESIGN CONCEPT

Although the design is applicable as a compressor, pump, motor, or engine, the engine implementation will be used for concept discussion. Figure 1and Figure 2 show end and side cross section views, respectively, of a four stroke engine design.

Mode of operation - The basis of the design is ball pistons rolling on an eccentric track. The balls exert tangential force on the cylinder walls which turn the rotor. Useful power is available at the rotor output shaft. The combustion chambers are within the spinning rotor. Chamber porting for intake, compression, power, and exhaust strokes is achieved by passage of the chamber tops across an internal stator with appropriate feeds as the rotor spins.
Beginning at top dead center (TDC) at 0 degrees rotation, the stator intake passage is open to the cylinder and a fuel/air charge is pulled into the cylinder as the ball piston moves radially outward for the first 90 degrees of rotation




Then the intake passage is closed off, and the ball reverses radial direction for the next 90 degrees of rotation, during which time the new charge is compressed (compression stroke).
Just past 180 degrees rotation, the compressed charge is ignited as the cylinder port passes a small ignitor port. Combustion ensues, and the high combustion pressure pushes radially outward on the ball piston for the next 90 degrees of rotation. The ball in turn pushes tangentially on the cylinder wall because of the "slope" of the eccentric ball track, which is now allowing the ball to move radially outward. The tangential force produces useful torque on the rotor (power stroke).
At 270 degrees of rotation, the spent combustion charge is allowed to escape through the exhaust passage as the cylinder port is uncovered. Exhaust is expelled as the ball moves radially inward for the next 90 degrees of rotation (exhaust stroke). Then the cycle repeats.
Important Design Features - The basic operation of the new design is conventional for an internal combustion engine, i.e. a piston reciprocates within a cylinder, and with porting, implements the four strokes of the Otto cycle. However, there are a number of features that make this engine design favorable for high efficiency and emissions control.
The porting required for four stroke operation is achieved with no additional moving parts, and no valve train losses. The porting mechanism is achieved with simple port clocking within the rotor/internal stator bearing interface. Thus, part count is low and the hardware is simple in geometry, with only the rotor and ball pistons as moving parts.
Note that cylinder induction and mixing are aided by centrifugal and coriolis accelerations, because the cylinders are within the spinning rotor.
Sliding friction sites are minimized by the use of a rolling ball piston. Friction at conventional piston rings, piston pin, and connecting rod/crankshaft bearing are eliminated. Sliding friction still exists at the ball/cylinder wall contact, but is minimized by special material selection and working gas hydrodynamics (and possibly local lubrication). The rotor/stator bearing is of a gas or fluid hydrostatic type, so friction is very low at that site.
The use of an eccentric ball track allows tailoring of the chamber volume vs. time to optimize the cycle from a thermodynamic and chemical kinetics standpoint. The only requirement is that the ball return to the starting radius at TDC before intake. For example, the expansion/exhaust stroke length can be made different than for intake/compression for more exhaust energy recovery, or the combustion can be held at constant volume for a certain period.
Multi-cycle rotors can be implemented. Instead of 4 strokes, 8, 12 or more strokes can be traversed in a single revolution. Compressors and pumps can use any multiple of 2 strokes (intake and compression only), either in parallel or staged arrangement. Provided that inertial forces are controlled (to be discussed later), power to weight ratio can therefore be made high. Other engine configuration options are also under investigation, including a dual rotor/intercooler configuration, diesel cycles, and 2 stroke cycles. The dual rotor option is attractive because it allows the compression and expansion ratios to be widely different (on separate rotors), but there are interstage pumping and intercooling losses that must be considered.
The use of many ball pistons, which each undergo the four strokes in clocked fashion, results in smooth power delivery and small net oscillatory forces. In fact, the total ball inertia forces are automatically balanced by symmetry if the number of balls is even. Further, combustion forces can be balanced by using an eight stroke rotor or stacking rotors axially with relative clocking. Also note that a four (or higher) stroke rotor compressor would be balanced.
Novel design of the ball track has been devised that will eliminate inertial forces on each ball that contribute to friction. As the ball moves in and out radially on the eccentric track while the rotor spins, coriolis and other acceleration forces are generated on the ball radially and tangentially. Net tangential inertial forces contribute to friction at the ball/cylinder wall contact point. By changing the ball
rolling radius using a widening/narrowing dual contact track in a prescribed manner, Figure 3, the net tangential inertial forces on the ball can be eliminated. In essence, the track design results in a balance of translational and rotational ball kinetic energy to eliminate tangential force. In other words, the ball track is designed so that the ball rolls around the track in synchronization with the rotor at constant rotation rate. Due to the form of the laws of motion, it is possible to maintain this condition at all rotation rates with a fixed track design. This allows the machine to be run at any high rpm desired, until the mechanical limits of the ball piston rolling on the track are reached (Hertzian stress fatigue). Engine power theoretically increases linearly with rpm. In actuality, intake flow dynamics may limit peak power at very high rpm, but that depends on the intake passageway details.
There is another interesting by-product of the rolling ball approach. The ball spins at very high rates around its own axis, while it is radially compressed by centrifugal forces of rotation about the rotor axis. These two sources of inertial load tend to cancel out in terms of generating internal ball stresses. This allows high engine speeds to be sustained with less ball fatigue damage.
Heat loss is kept low because the engine intake can be configured to flow through the outer stator/rotor cavity. Rotor heat loss is gained by the intake charge, with less loss to the outer stator.

Technical Challenges - The main concerns for operation of the new machine are being addressed in focused subscale testing.
First, leakage through the ball piston/cylinder gap is a significant factor for engine or compressor efficiency, especially at low speeds. Calculations show that the flow is choked during combustion due to high pressure differential and small clearance area. Choking is helpful in keeping leakage to acceptable levels. Engine efficiency predictions based on simple choked flow leakage models are very favorable. Leakage tests performed in subscale testing have shown that leakage is less than the simple models predict, and dependence on ball spin, pressure, and rpm have been and are being characterized.
Second, the friction and wear at the ball piston/cylinder wall sliding interface is important. Engine performance depends on the magnitude of the effective friction coefficient, and high relative sliding speed can contribute to wear. Engine efficiency predictions based on an average friction coefficient of 0.1 or less are very favorable. Subscale tests have proven that the coefficient of friction for a









silicon nitride ball piston on polished steel with no lubrication is about 0.075 +/- 0.03, about the same as estimated.
The wear issue must be proven out mainly by testing with a full range of operating conditions. Thus far, tendency for cylinder wall plasticity has indicated that cylinder material must be of high hot strength and hardness. Large reductions in "wear-in" plastic flow were achieved by changing cylinder walls from 1018 hot rolled steel to 17-4PH hardened to about R_c 44. A material with better hot hardness, such as achievable with M2 high speed tool steel, has been subsequently selected to resist high sliding flash temperatures and completely eliminate cylinder wall plastic deformation. Low cost production options include case hardening, plating over a hot hard substrate, coatings, and other surface treatment technologies.
It is intended to design the machine for no lubrication, except that available from the working gas or fluid. This is most feasible for compressor and pump applications. However, lack of lubrication is a driving consideration in cylinder wall material selection for the engine, based on subscale testing to date with air only. Extra lubrication is a secondary design option that may be best for some applications, especially the engine, where loads are higher. Lubrication can reduce friction coefficient and wear potential and provide hydrodynamic separation at the ball piston/cylinder wall, and also can reduce leakage flow past the ball piston. However, there will be a trade off for residue build up, emissions, and maintenance.

MATERIAL SELECTION

A series of tests to characterize friction and wear of various materials in a simulated ball piston engine/compressor were performed to aid in selection of production materials. Another goal of the tests was to explore the possibility that

                                                                       

this machine could run without lubrication. If unlubricated operation was not possible, tests with instrumentation                                                                                                                                             would be used to confirm the lubricated operation of the machine and the resulting internal loads. Two types of tests were performed. Simple drag sled static coefficient of friction tests were completed to evaluate sleeve materials and coatings. The materials with the lowest friction coefficient then became the focus of operational dynamic tests using a subscale tester.

TEST SETUP   

                                                                                                                                                                      The test setup was designed to simulate the conditions of a typical ball piston compressor. The key response parameters of interest for these tests were friction, wear, and leakage.

The test setup consisted of a test cylinder suspended on load cells, an electric motor driving an eccentric circular steel drive wheel with a simple ball track on the edge, a ball piston driven by the eccentric wheel, compressed air supplied to the cylinder, and a cylinder heater. The test cylinder had a removable sleeve so various material and coating combinations could be tested. The heater was used to change the sleeve temperature to partially simulate compressor thermal conditions and to adjust the ball piston clearance. A drip lubrication system for applying oil to the drive wheel track was fabricated to perform lubricated tests. This system deposited approximately five drops of 10 weight motor oil on to the drive wheel track per minute. A photograph of the test set up is shown in Figure 1.
The configuration of the eccentric drive wheel and its position relative to the cylinder axis results in simultaneous vertical oscillation and spinning of the ball within the cylinder and oscillating mechanical leverage angle that closely approximates the actual operation of a ball piston machine. Of greatest importance, given a cylinder internal pressure via supply air, ball/cylinder wall interaction forces (including sliding friction) are closely simulated.
Dynamic and static cylinder support loads, cylinder and tank pressure, and cylinder temperature were measured via a PC-based data acquisition system. The operating friction coefficient between ball piston and sleeve was indicated by correlation with one of the load cell signals. Leakage was calculated using tank pressure drop measurements over time. Wear was visually observed on the ball and sleeve after testing.

TESTING

First, static friction tests were performed on uncoated steel, cadmium plated steel, steel coated with Alumide, steel coated with Chromide, and steel coated with TiN, TiCN, TiAlN, or TiAlCN ion deposition treatments. In addition, tests were done after polishing TiAlN and TiAlCN samples with fine grit lapping compound. The polished TiAlCN coating was selected as the best sleeve coating for sub scale testing. It exhibited the lowest friction coefficient against a silicon nitride ball, about 0.06, comparable with that of smooth plain steel. This was a welcomed result, showing that the hard ceramic-like coating did not adversely interact with the silicon nitride ceramic. Polishing was necessary to remove sputter residue that increased roughness. The tests indicated that using a highly polished surface would minimize friction coefficient in production.

Next, operational tests were performed with a wide variety of sleeves and several ball types. Mild steel, Chrome plated steel, plain M2 tool steel, and TiAlCN coated M2 tool steel sleeves were tested. Silicon nitride, Alumina, chromium steel, Teflon, and Nylon balls were used. In addition, cryogenically treated plain M2 and TiAlCN coated M2 tool steel sleeves were tried. This cryo treatment was purported to improve wear resistance.

RESULTS

First, the Teflon and Nylon balls were eliminated from consideration due to insufficient dimensional stability. They deformed enough just in storage to preclude fitting the cylinder.

Although some of the remaining materials and coatings worked better than others, none of the unlubricated tests were successful. The heat generated at the ball piston/test sleeve interface, despite reasonable Hertzian stress levels, caused "smearing" failure of the sleeve wall shortly after the tests were started. Material was actually removed from the cylinder walls and redeposited. A distinct wear pattern was visible on the sleeve and most tests were stopped because the ball seized in the sleeve on the built-up material.
Lubrication solved the problem. The silicon nitride ball ran smoothly in the M2 tool steel sleeve. Test durations of 100 minutes at 200 psi and 800 RPM and 60 minutes at 400 psi and 800 RPM were achieved with no visible wear on sleeve or ball. Figure 2 shows the sleeve bore after the test. In addition, leakage was greatly reduced.








An Alumina ball was successfully run for 10 minutes at 400 psi and 800 RPM as well in a lubricated M2 tool steel sleeve. The sleeve and ball showed minimal signs of wear. Alumina is heavier than silicon nitride, but is much less expensive, and is a viable option for compressor, pump, and motor applications.
A 20 minute test at 400 psi and 800 RPM was run with a chrome steel ball on a lubricated M2 tool steel sleeve. The test was successful but indications of wear were observed. It is likely that the lower modulus of steel caused more deformation of the ball, resulting in a wider contact area, and some cylinder wear indicated as "fogging" of the shiny M2 sleeve surface. The ball also showed fine scratching in a directional pattern, and steel removed from the ball was seen in the lube oil. It is clear that the steel ball would not be acceptable for long term operation.

After this series of tests it is clear that lubrication must be used for the design to work as a compressor or engine with conventional materials. Without lubrication of some kind, the localized heat at the rubbing contact is too great even for high temperature resistant metals and coatings. It may be possible, for compressor/motor/pump applications, to use a ball piston made of some "high-tech" self-lubricating material, such as graphite-impregnated metal or a dimensionally stable and lubricious plastic. These materials may be investigated in the future. For an engine, however, the higher temperature requirements would preclude such materials, and oil lubrication is likely to be the best approach.

It was also found that oil lubrication can greatly improve machine efficiency by virtually eliminating rubbing friction and reducing leakage. Lubrication increases mechanical efficiency from approximately 85% to approximately 97%. Most of this improvement is due to friction reduction. Results indicate that the lube oil produces a hydrodynamic bearing layer at the contact region, resulting in negligible friction coefficient. If this is true, cylinder surface hardness is no longer a great concern, and special coatings and treatments are unnecessary.
Using a stiff ceramic ball with lubrication should work well in a compressor or an engine as long as the lubrication system is properly designed. High speed engines will require a silicon nitride ball to minimize centrifugal loads at high speeds. It is likely that materials other than M2 tool steel could be used as a cylinder material with proper lubrication, such as conventional cast iron and chrome plated iron or steel.
CONCLUSIONS
Analyses based on the design assumptions showed that the ball piston engine has potential for achieving higher efficiency than piston internal combustion engines. In addition, subscale tests have shown that critical leakage and friction characteristics are consistent with design assumptions. Thus, the feasibility of this new engine concept based on ball pistons has been proven.
A new approach to kinematic design has been devised to eliminate friction contributions from inertial forces in the engine. On the other hand, conventional carburetion/induction and exhaust systems are applicable to the new engine. Some material problems were encountered in subscale testing, indicating that more detailed material selection was warranted. The material selection has been done in anticipation of additional subscale tests to extend the range of speed and duration of simulated operation. Baseline material for testing is M2 tool steel.
Shortly after cylinder material selection is verified in subscale tests, fabrication and testing of a prototype engine will be undertaken. The prototype will be used to finalize design details such as thermal design, transient operation, starting, and cylinder wall treatments with actual combustion environment.
The new design concept can be immediately applied to compressor and pump applications in parallel with further engine development. The concept holds immediate promise for high efficiency and low cost in these applications, where temperatures and loads are more benign and lower cost materials can be used.

REFERENCES

1. Dale, T.W.,"Spherical Piston Radial Action Engine", U.S. Patent #5,419,288, May 30, 1995.
2. Avallone, E.A. and Baumeister, T. III,"Marks' Standard Handbook for Mechanical Engineers", Ninth edition, McGraw-Hill, New York, 1987.
3. Richards, T.D.,"The Hanes Engine", informational report, copyright 1994.
4. Ashley, S.,"A New Spin on the Rotary Engine", Mechanical Engineering, April 1995, p80-82.
5. Bloch, H.P.,"A Practical Guide to Compressor Technology", McGraw-Hill, New York, 1996.
6. Anon.,"GAUSS Volume I, System and Graphics Manual", Aptech Systems, Inc., Maple Valley, WA, July 18, 1994.
7. Heywood, J.B.,"Internal Combustion Engine Fundamentals", Mcgraw-Hill, New York, 1988.

8.Internate

i am using the fill surface tool in solid works............
it works so awesome...........

After joining the surfaces..............

12th HSC std result for Mahrashtra state.

Maharashtra Board Class 12 HSC Results 2010

The results for the Higher Secondary Certificate (HSC) for Class XII or Std 12th held in Maharashtra will be declared on May 25th 2010 at 11AM.

Students who appeared for the Maharashtra HSC exams in 2010 will be able to check their results online after 11AM at the official Maharashtra Exam site. Maharashtra HSC results will be available at http://mahresult.nic.in/ after 11AM on Tuesday.

Students will require to have their hall ticket roll numbers in order to view their HSC exam results online. Students can also check their exam results by visiting http://results.maharashtraeducation.net/ or http://www.msbshse.ac.in/.

The HSC results will be declared for the Arts, Science and Commerce streams for students who appeared for the exams in February 2010. However, students will get their marksheets from their colleges only on May 31st after 3PM.

The online results are being declared a week earlier than the actual results is handed out in order to allow students to better plan out their future course of actions. We wish all the students best of luck for their exam results.

“NETWORK SECURITY”

ABSTRACT

 

 

Today's world is a networked world in which everyone is entering into outside world for mainly, for communication purpose. This is possible only due to the internet facility whose access is an immense source of information. Apart from being a source, we need to have secure communication channel through which the information passes. Loss of irreplaceable data is very real threat, especially for the business owners. They need to communicate with their vendors, employees, customers who are far away from each other. At this stage, Internet will be the easiest & fast source of information exchange for them. So, to keep this information safe & secure, a need felt to provide security to the Internet.

Network security is a complicated subject, historically only tackled by well-trained and experienced experts. Network, as it is vast, interconnected & complicated structure requires lot of understanding about each component, which is a part of it. So, Network Security tests our stamina about keeping the network as safe, secure as possible. As more and more people become ``wired'', an increasing number of people need to understand the basics of security in a networked world. Network Security ensures the reliability, flexibility of an network's working so as to make smooth communication through the network. Any organization, before taking Internet access, first think of firewall.

Some history of networking is included, as well as an introduction to TCP/IP and internetworking. Some points are also concerned to the types of threats, from which one should be aware of, & providing protection against it.

 

 

 

 

 

 

 

 

 

INDEX

 

1.    INTRODUCTION

2.    SECURED COMMUNICATION

3.    NEED OF SECURITY

• THREATS TO SECURITY
  

  4.    MECHANISMS OF SECURITY
  

  5.    CRYPTOGRAPHY
  

• SECRET - KEY ENCRYPTION
  
• PUBLIC - KEY ENCRYPTION
  

1. FIREWALL AND INTERNET ACCESS.
   

• FIREWALL ARCHITECTURE
  
• PACKET - LEVEL FILTERS.
  
• SECURITY AND PACKET FILTER MECHANISM.
  
• ACCESSING SERVICES THROUGH A FIREWALL.
  

  
   

1. NETWORK SECURITY TOOLS
   
2. CONCLUSION
   
3. REFERENCES
   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

INTRODUCTION

 

Network

 

A ``network'' has been defined as

``Any set of interlinking lines resembling a net, a network of roads || an
interconnected system, a network of alliances.''

This definition suits our purpose well:

A computer network is simply a system of interconnected computers.

 

Security

Security by the name itself is very important for any individual, a machine or also in a network like the locks to help tangible property secure, computers and data networks need provisions that help keep the information secure. Security in an Internet environment is both important and difficult. It is important because information has a significant value -information can be bought and sold directly or used indirectly to create new products and services that yield high profits. Security in an internet is difficult because involves understanding when and how participating users, computers, services and networks can trust one another, as well as understanding the technical details of network hardware and protocols.

As the Internet is becoming more complex day by day security administrators face the risk of being attacked by external intruders that may

• Read Access - Read or copy confidential information.
  
  • Write Access - Write to network or perhaps infect the system with the system with viruses and Trojan horses.
    
• Denial of Service - Deny authorized users normal network services.
  

A single computer can compromise the security of entire network. To guard against such threats the security of distributed system, security
policies must be adapted and security mechanisms must be employed to implement security policies.

 

 

Threats

There are four classes of Security threats to computers systems. These are

1. Leakage
   
2. Tempering
   
3. Resource stealing
   
4. Vandalism
   

Thus to guard against threats to the security of distributed system, security policies as well as security mechanisms must be employed thereby providing a secure communication link for a data transmission between interconnected host computer systems of network.

 

SECURED COMMUNICATION

Suppose two persons A & B are communicating. Both of them make sure that contents delivered are not altered by an intruder and are being transferred between them only. The following considerations below reflect these desirable properties of secure communication.

 

• SECRECY
  

Only the sender and the intended receiver should be able to understand the contents of the transmitted message. Because eavesdroppers may intercept the message been somehow "encrypted" so that an intercepted message can be "decrypted" by an interceptor. For example, A might also want the mere fact that she's communicating with B to be a secret.

 

• AUTHENTICATION
  

Here both the sender and receiver need to confirm the identity of the other party involved in the communication- to confirm that the other party is indeed who or what they claim to be.

For example - If A receives mail from B, in order to know that it has been sent by the B only A needs some authentication; likewise in network there are authentication protocols.

 

• MESSAGE INTEGRITY
  

Here the sender and receiver want to ensure that apart from authentication the content of their communication is not altered, either maliciously or by accident in transmissions.

 

NEED FOR NETWORK SECURITY

Most of the security problems are intentionally caused by malicious people trying to gain some benefit or harm some one enforcing the security administrators to keep network free from programming errors. Thus in turn involves out mastering often intelligent, dedicated and sometimes well-funded adversaries and hence need for security rises. The issue is that network security calls for protections against malicious attack by hackers and intruders, but security is also associated with controlling and authorization mechanisms and the prevention of the effects of errors and equipment failures.

All communication over Internet uses the transmission control protocol /Internet protocol (TCP/IP). TCP/IP allows information to be send from one computer to another computer through variety of intermediate computer and separate network before its destination.

The great flexibility of TCP/IP has led to its worldwide acceptance as the basic Internet and Intranet communications protocol. At the same time, the fact that TCP/IP allows information to pass through intermediate computers makes it possible for a third party to interface with communications in the following ways:

 

• Eavesdropping. Information remains intact, but its privacy is compromised .For example, someone could learn your credit card number, record a sensitive conversation, or intercept classified information.
  
• Tampering. Information in transit is changed or replaced and then sent on to the recipient. For example, someone could alter an order for goods or change a person's resume.
  
• Impersonation. Information passes to a person who poses as the indirect recipients. Impersonation can take two forms
  
  • Spoofing: - A person can pretend to be someone else.
    

    For example, a person can pretend to have the email address jdoe@mozilla.com <mailto:jdoe@mozilla.com>, or a computer can identify itself as a site called www.mozilla.com http://www.mozilla.com
    

    when it is not. This type of impersonation is known as spoofing.
    

 

• Misrepresentation: - A person or organization can misrepresent itself. For example, suppose the site www.mozilla.com http://www.mozilla.com pretends to be a furniture store when it is really just a site that takes credit-card payments but never sends any goods.
  

 

• Packet Sniffing; - A packet snifter is a program running in a network-attached device that passively receives all data link layer frames passing by network device's interface. In broadcast environment like the Ethernet LAN the packet snifter receives all frames being transmitted from all hosts on the LAN. These frames can then be passed on to application programming that extract application level data.
  

 

 

MECHANISMS FOR NETWORK SECURITY

 

Internet security problems can be divided into three broad sets.

• AUTHENTICATION MECHANISMS
  

Authentication mechanisms solve the problem of verifying identification. In centralized multi-user systems, the user's identity can be authenticated by a password check at the start of each interactive session. In distributed systems, authentication is the means by which the identities of servers and clients are reliably established. The mechanism used to achieve this is based on possession of encryption keys.

 

• PRIVACY MECHANISMS
  

Encryption can also handle the problem of privacy. If a sender and receiver both use public key encryption scheme, the sender can guarantee that the intended receiver can read a message .To do so, the sender uses the receiver's public key to encode the message and the receiver uses its private key to decode the message. Because only the intended receiver has necessary private key, no other party can decode the message.

 

• ACCESS CONTROL MECHANISMS
  

Mechanisms that control Internet access handle problem of screening of particular network or an organization from an unwanted communication. Such mechanism can help to prevent outsiders from obtaining information, changing information, or disrupting communication on an organization 's internal Internet.

 

CRYPTOGRAPHY

INTRODUCTION

"The art of devising a ciphers i.e. converting the plaintext into coded format & then decoding it" refers to cryptography. Here message to be encrypted are known as plain text & are transformed by a function parameterized by a key. The output of encryption process is known as 'cipher text' and is often transmitted by a messenger .At the receiver its decrypted with help of decryption key and the original message is retrieved.

To encrypt information we transform it in such way that it cannot understand by anyone except the intended recipient who posses the means to reverse the transformation. Computer encryption techniques fall into two main classes-

1. Secret-key method
   
2. Public-key method
   

which useful implementation security, which can be used without much impact on the method of encryption.

 

1. SECRET KEY ENCRYPTION
   

This method is used for transformation of secret information. In this method applying an agreed encryption function to the plain text with secret key encrypts a message. Decryption is achieved by applying inverse function to the cipher text using the same key, to produce the original plain text. Since the keys are kept secret, the encryption and decryption function need not be secret. Before communication can take place both the sender and receiver must acquire the secret key.

 

1. PUBLIC KEY ENCRYPTION
   

In this method each potential recipient of message makes a pair of keys, Ke & Kd and keeps the decryption key Kd a secret. The encryption key Ke can be made known publicly for use by anyone who wants to communicate. This method is based on use of any-way function to define the relation between the two keys, so that it is very hard to determine Kd from knowledge of Ke. Thus it avoids the need for transmission of secret keys between principles.

 

FIREWALLS AND INTERNET ACCESS

The Firewalls defines as "a system or group of systems that enforces an access control policy between two networks." In the context of home networks, a firewall typically takes one of two forms:

1. Software firewall - specialized software running on an individual computer,
   

or

1. Network firewall - a dedicated device designed to protect one or more computers.
   

 

 

 

A single technique has emerged as the basis for Internet access control .The technique places a block known as Internet firewall at the entrance to the part of Internet to be produced .For example, an organization can place firewall at its connection to the global Internet to protect it from unwanted access .A firewall partition has two regions , Informally referred as inside & outside.

• Firewall Architecture
  

There are lots of ways to structure your network to protect your systems using a firewall. If you have a dedicated connections to the Internet through a router, you could plug the router directly into your firewall system. Or, you could go through a hub to provide for full access servers outside your firewall.

1. Dial-up Architecture
   

You may be using a dialup service like an ISDN line. In this case you might use a third network card to provide provide a filtered DMZ. This gives you full control over your Internet services and still separates them from your regular network.

1. Single Router Architecture
   

If there is a router or cable modem between you and the Internet. If you own the router you could setup some hard filter rules in the router. If this router is owned by your ISP so you may not the have the needed controls. You can ask your ISP to put in filters.

1. Firewall with Proxy Server
   

If you need to monitor where users of your network are going and your network is small, you can intergrate a proxy server into your firewall. ISP's some times do this to create interest list of their users to resell to marketing agencies.

You can put the proxy server on your LAN as will. In this case the firewall should have rules to only allow the proxy server to connect to the Internet for the services it is providing. This way the users can get to the Internet only through the proxy.

1. Redundent Internet Configuration
   

If you are going to run a service like YAHOO or may be Slash Dot you may want to make your system by using redundant routers and firewalls. (Check out the High Availability HowTo.) By using a round-robin DNS techniques to provide access to multiple web servers from one URL and multiple ISP's, routers and firewalls using High Availability techniques you can create a 100% uptime service.

It is easy to let your network get out of hand. Keep control of every connection. It only takes a user with a modem to compromise your LAN.

 

• Packet-level filters:
  

Many commercial routers offer a mechanism tact augments normal routine and permits a manager to further control packet processing . Packet filters mechanism requires the manager to specify how the router should dispose of each datagram . When Datagram first arrives, the router passes the Datagram through its packet filter before performing any other processing . if the filter rejects the Datagram the router drops it immediately. Each router vender is free to choose the capabilities of their packet filter as well as the interface a manager use to configure the filter.

 

• Security and packet filter mechanism:
  

Packet filtering firewall consists of list of acceptance denial rules . These rules explicitly define which packets will and will not be allowed through the network interface. These rules are based on the specific network layer's source and destination addresses.

 

• Accessing service through a firewall:
  

An organization can only provide safe access to outside services through a secure computer . Instead of trying to make all computer system organizations secure,an organization usually associates one secure computer with each firewall. It is often called as bastion host.

 

 

Bastion host :

A general-purpose computer used to control access between the internal (private) network (intranet) and the Internet (or any other untrusted network). Typically, these are hosts running a flavor of the Unix operating system that has been customized in order to reduce its functionality to only what is necessary in order to support its functions. Many of the general-purpose features have been turned off, and in many cases, completely removed, in order to improve the security of the machine.

 

To permit safe access, firewall has two conceptual barriers which the figure shows. The outer barrer blocks all incoming traffic except :

 

1. Datagrams destined for services on the bastion host that the organization choose
   

to make available externally,

1. Datagrams destined for the clients on the bastion host .
   

   The inner barrier blocks the incoming traffic excepts datagrams that originate on the
   

   bastion host.
   

 

To understand how the bastion host operates ,consider the FTP service. Suppose a user in the organization needs to access an external FTP server to obtain copy of the file . Because the firewall prevents the user's computer from receiving incoming datagrams , the user cannot run FTP client software directly .Instead, the user must run the FTP clienton the bastion host. after the file has been copied to the bastion host,the user can run file transfer between the bastion host and their local computer .

 

NETWORK SECURITY TOOLS

Various Tools for the Network Security are existing in this world which can work better& provides reliable communication channel through which information can be safely transmitted from sender to the reciever. These tools are as follows:

• SATAN
  

SATAN, the System Administrator Tool for Analyzing Networks, is a network security analyzer designed by Dan Farmer and Wietse Venema. SATAN scans systems connected to the network noting the existence of well known, often exploited vulnerabilities. For each type of problem found, SATAN offers a tutorial that explains the problem and what can be done.

 

• ipacl
  

The ipacl package from Siemens. Forces all TCP and UDP packets to pass through an access control list facility. The configuration file allows packets to be accepted, rejected, conditionally accepted, and conditionally rejected based on characteristics such as source address, destination address, source port number, and destination port number. Should be portable to any system that uses System V STREAMS for its network code.

• TCP Wrappers
  

The tcp_wrapper package by Wietse Venema. Formerly called log_tcp. Allows monitoring and control over who connects to a hosts TFTP, EXEC, FTP, RSH, TELNET, RLOGIN, FINGER, and SYSTAT ports. Also includes a library so that other programs can be controlled and monitored in the same fashion.

 

Some more no. of tools are as follows:

1. Logdaemon
   
2. Portmap
   
3. Rpcbind
   
4. Sara
   
5. Scanssh
   
6. Securelib
   
7. Rpcbind
   

   
    

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CONCLUSION

 

 

Security is a very difficult topic. Everyone has a different idea of what ``security'' is, and what levels of risk are acceptable. The key for building a secure network is to define what security means to your organization . Once that has been defined, everything that goes on with the network can be evaluated with respect to that policy. Projects and systems can then be broken down into their components, and it becomes much simpler to decide whether what is proposed will conflict with your security policies and practices.

Many people pay great amounts of lip service to security, but do not want to be bothered with it when it gets in their way. It's important to build systems and networks in such a way that the user is not constantly reminded of the security system around him. Users who find security policies and systems too restrictive will find ways around them. It's important to get their feedback to understand what can be improved, and it's important to let them know why what's been done has been, the sorts of risks that are deemed unacceptable, and what has been done to minimize the organization's exposure to them.

Security is everybody's business, and only with everyone's cooperation, an intelligent policy, and consistent practices, will it be achievable.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

REFERENCES

 

 

 

1. Computer networks by Andrew Tannenbaum.
   
2. Computer networking by John Martin.
   
3. Internetworking with TCP/IP by Douglas E.Comer.
   
4. http://www.google.com