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Friday, February 19, 2010

Human Body Facts


Body Facts

  • In one day, a human sheds 10 billion skin flakes. This amounts to approximately two kilograms in a year.

  • Every square inch of the human body has about 19,000,000 skin cells.

  • Approximately 25% of all scald burns to children are from hot tap water and is associated with more deaths than with any other liquid.

  • Forty-one percent of women apply body and hand moisturizer at least three times a day.

  • Every hour one billion cells in the body must be replaced.

  • The world record for the number of body piercing on one individual is 702, which is held by Canadian Brent Moffat.

  • The small intestine in the human body is about 2 inches around, and 22 feet long.

  • The human body makes anywhere from 1 to 3 pints of saliva every 24 hours.

  • The human body has approximately 37,000 miles of capillaries.

  • The aorta, which is largest artery located in the body, is about the diameter of a garden hose.

  • The adult human body requires about 88 pounds of oxygen daily.

  • It is very common for babies in New Zealand to sleep on sheepskins. This is to help them gain weight faster, and retain their body heat.

  • An average women has 17 square feet of skin. When a women is in her ninth month of pregnancy she has 18.5 square feet of skin.

  • The width of your armspan stretched out is the length of your whole body.

  • 41% of women apply body or hand moisturizer a minimum three times a day.

  • A human's small intestine is 6 meters long.

  • There are as many hairs per square inch on your body as a chimpanzee. You don't see all of them because most are too fine and light to be noticed.

  • Every hour one billion cells in the body must be replaced.

  • Dead cells in the body ultimately go to the kidneys for excretion.

  • By walking an extra 20 minutes every day, an average person will burn off seven pounds of body fat in an year.

  • The human body is 75% water.
Heart Facts

  • Women hearts beat faster than men.

  • Three years after a person quits smoking, there chance of having a heart attack is the same as someone who has never smoked before.

  • The human heart weighs less than a pound.

  • The human heart can create enough pressure that it could squirt blood at a distance of thirty feet.

  • The first open heart surgery was performed by Dr. Daniel Hall Williams in 1893.

  • Scientists have discovered that the longer the ring finger is in boys the less chance they have of having a heart attack.

  • The right lung of a human is larger than the left one. This is because of the space and placement of the heart.

  • The human heart beast roughly 35 million times a year.

  • Olive oil can help in lowering cholesterol levels and decreasing the risk of heart complications.

  • In a lifetime, the heart pumps about one million barrels of blood.

  • In 1967, the first successful heart transplant was performed in Cape Town, South Africa.

  • People that suffer from gum disease are twice as likely to have a stroke or heart attack.

  • Most heart attacks occur between the hours of 8 and 9 AM.

  • The human heart beast roughly 35 million times a year.

  • At one time it was thought that the heart controlled a person's emotions.
Brain Facts

  • Women are twice as likely to be diagnosed with depression than men in the United States.

  • The human brain has about 100,000,000,000 (100 billion) neurons.

  • From all the oxygen that a human breathes, twenty percent goes to the brain.

  • People who ride on roller coasters have a higher chance of having a blood clot in the brain.

  • Once a human reaches the age of 35, he/she will start losing approximately 7,000 brain cells a day. The cells will never be replaced.

  • It is not possible to tickle yourself. The cerebellum, a part of the brain, warns the rest of the brain that you are about to tickle yourself. Since your brain knows this, it ignores the resulting sensation.

  • A women from Berlin Germany has had 3,110 gallstones taken out of her gall bladder.

  • In America, the most common mental illness is Anxiety Disorders.

  • Your brain is 80% water.

  • Your brain is move active and thinks more at night than during the day.
Bones Facts

  • The smallest bone in the human body is the stapes bone which is located in the ear.

  • There are 54 bones in your hands including the wrists.

  • The only bone fully grown at birth is located in the ear.

  • The human face is made up of 14 bones.

  • The chances of getting a cavity is higher if candy is eaten slowly throughout the day compared to eating it all at once and then brushing your teeth.

  • If an identical twin grows up without having a certain tooth, the other twin will most likely also grow up with that tooth missing.

  • Humans are born with 300 bones in their body, however when a person reaches adulthood they only have 206 bones. This occurs because many of them join together to make a single bone.

  • Gardening is said to be one of the best exercises for maintaining healthy bones.

  • Enamel is hardest substance in the human body.

  • Although the outsides of a bone are hard, they are generally light and soft inside. They are about 75% water.

  • Adult human bones account for 14% of the body's total weight.

  • In 2000 babies are born with a tooth that is already visible.

  • Fingernails grow nearly 4 times faster than toenails!

  • Your thigh bone is stronger than concrete.

  • The strongest bone in your body is the femur (thighbone), and it's hollow!                             
Blood Facts

  • Two million red blood cells die every second.

  • There are approximately 100,000 miles of blood vessels in the human body.

  • Seven percent of a humans body weight is made up of blood.

  • In the early nineteenth century some advertisements claimed that riding the carousel was good for the circulation of blood.

  • Each day 400 gallons of recycled blood are pumped through the kidneys.

  • By donating just one pint of blood, four lives can be saved.

  • Blood is such a good stain that Native Americans used it for paint.

  • The kidneys filter over 400 gallons of blood each day.

  • The average life span of a single red blood cell is 120 days.

  • Blood accounts for about 8% of a human's body weight.

  • A woman has approximately 4.5 liters of blood in her body, while men have 5.6 liters.

  • Your blood takes a very long trip through your body. If you could stretch out all of a human's blood vessels, they would be about 60,000 miles long. That's enough to go around the world twice.

  • Half your body’s red blood cells are replaced every seven days.

  • If all the blood vessels in your body were laid end to end, they would reach about 60,000 miles.
Eyes Facts

  • We should never put anything in or near our eyes, unless we have a reason to use eye drops. We would only do that if our doctor or parent told us to use them.

  • Blinking helps to wash tears over our eyeballs. That keeps them clean and moist. Also, if something is about to hit our eye, we will blink automatically.

  • Our body has some natural protection for our eyes. Our eyelashes help to keep dirt out of our eyes. Our eyebrows are made to keep sweat from running into our eyes.

  • Our eyes are very important to us, and we must protect them. We don't want dirt, sand, splinters or even fingers to get in our eyes. We don't want our eyes to get scratched or poked. That could damage our sight!

  • The study of the iris of the eye is called iridology.

  • The shark cornea has been used in eye surgery, since its cornea is similar to a human cornea.

  • The number one cause of blindness in adults in the United States is diabetes.

  • The eyeball of a human weighs approximately 28 grams.

  • The eye of a human can distinguish 500 shades of the gray.

  • The cornea is the only living tissue in the human body that does not contain any blood vessels.

  • The conjunctiva is a membrane that covers the human eye.

  • Sailors once thought that wearing a gold earring would improve their eyesight.

  • Research has indicated that a tie that is on too tight cam increase the risk of glaucoma in men.

  • People generally read 25% slower from a computer screen compared to paper.

  • Men are able to read fine print better than women can.

  • In the United States, approximately 25,000 eye injuries occur that result in the person becoming totally blind.

  • All babies are colour blind when they are born.

  • A human eyeball weighs an ounce.

  • If the lens in our eye doesn't work quite right, we can get glasses to help us see. Glasses have lenses in them that work with our eye's own lens to help us see better.

  • Babies' eyes do not produce tears until the baby is approximately six to eight weeks old.

  • The reason why your nose gets runny when you are crying is because the tears from the eyes drain into the nose.

  • The most common injury caused by cosmetics is to the eye by a mascara wand.

  • Some people start to sneeze if they are exposed to sunlight or have a light shined into their eye.

  • The highest recorded speed of a sneeze is 165 km per hour.

  • It is impossible to sneeze with your eyes open.

  • The space between your eyebrows is called the Glabella.

  • Inside our eye, at the back, is a part called the "retina." On the retina are cells called "rods" and "cones." These rods and cones help us to see colors and light.

  • Just behind the pupil is a lens. It is round and flat. It is thicker toward the middle.

  • Over the front of our eye is a clear covering called the "conjunctiva."

  • The white part of our eye is called the "sclera." At the front, the sclera becomes clear and is called the "cornea."

  • Around the pupil is a colored muscle called the "iris." Our eyes may be BLUE, BROWN, GREEN, GRAY OR BLACK, because that is the color of the iris.

  • Our eyes have many parts. The black part on the front of our eye is called the "pupil." It is really a little hole that opens into the back part of our eyes.

  • Your eyes blinks over 10,000,000 times a year!
Mouth Facts

  • In a month, a fingernail grows an eighth of an inch.

  • People whose mouth has a narrow roof are more likely to snore. This is because they have less oxygen going through their nose.

  • While sleeping, one man in eight snores, and one in ten grinds his teeth.

  • It takes food seven seconds to go from the mouth to the stomach via the esophagus.
Tongue Facts

  • Close to fifty percent of the bacteria in the mouth lives on the surface of our tongue.

  • There are approximately 9,000 taste buds on the tongue.

  • Your tongue has 3,000 taste buds.

  • 85% of the population can curl their tongue into a tube.                                                              
Hair Facts

  • On average, a man spends about five months of his life shaving.

  • On average, a hair strand's life span is five and a half years.

  • On average redheads have 90,000 hairs. People with black hair have about 110,000 hairs.

  • Next to bone marrow, hair is the fastest growing tissue in the human body.

  • In a lifetime, an average man will shave 20,000 times.

  • Humans have about the same number of hair follicles as a chimpanzee has.

  • Hair will fall out faster on a person that is on a crash diet.

  • The average human head weighs about eight pounds.

  • The reason why some people get a cowlick is because the growth of their hair is in a spiral pattern, which causes the hair to either stand straight up, or goes to a certain angle.

  • The reason why hair turns gray as we age is because the pigment cells in the hair follicle start to die, which is responsible for producing "melanin" which gives the hair colour.

  • The big toe is the foot reflexology pressure point for the head.

  • The loss of eyelashes is referred to as madarosis.

  • The longest human beard on record is 17.5 feet, held by Hans N. Langseth who was born in Norway in 1846.

  • The fastest growing tissue in the human body is hair.

  • The average human scalp has 100,000 hairs.

  • Hair and fingernails are made from the same substance, keratin.

  • Hair is made from the same substance as fingernails.

  • Eyebrow hair lasts between 3-5 months before it sheds.

  • The first hair dryer was a vacuum cleaner that was used for drying hair.

  • A Russian man who wore a beard during the time of Peter the Great had to pay a special tax.

  • Everyday approximately 35 meters of hair fiber is produced on the scalp of an adult.

  • Brylcreem, which was created in 1929, was the first man's hair product.

  • Ancient Egyptians used to think having facial hair was an indication of personal neglect.

  • A survey done by Clairol 10 years ago came up with 46% of men stating that it was okay to color their hair. Now 66% of men admit to coloring their hair.

  • A lifespan of an eyelash is approximately 150 days.
Diseases Facts

  • People that use mobile phones are 2.5 time more likely to develop cancer in areas of the brain that are adjacent to the ear they use to talk on the mobile phone.

  • Over 90% of diseases are caused or complicated by stress.

  • Over 436,000 U.S. Troops were exposed to depleted uranium during the first Gulf war.

  • On average, 90% of the people that have the disease Lupus are female.

  • Many cancer patients that are treated with chemotherapy lose their hair. For some when the hair grows back, it can grow back a different colour, or be curly or straight.

  • Diabetes is the fourth leading cause of death in the U.S., accounting for about 180,000 deaths per year.

  • Chances of a women getting breast cancer are increased by excessive use of alcohol.

  • A popular superstition is that if you put a piece of bread in a baby's crib, it will keep away diseases.

  • A person that is struck by lightning has a greater chance of developing motor neurons disease.

  • Every year in the U.S., there are 178,000 new cases of lung cancer.

  • Every three minutes a woman is diagnosed with breast cancer.

  • Asthma affects one in fifteen children under the age of eighteen.

  • Every eleven minutes in the U.S., a woman dies of breast cancer.

  • Due to eating habits in the USA, one in three children born in the year 2000 have a chance of getting type II diabetes.

  • The oldest known disease in the world is leprosy.

  • The number one cause of rabies in the United States are bats.

  • Coughing can cause air to move through your windpipe faster than the speed of sound — over a thousand feet per second!

  • A headache and inflammatory pain can be reduced by eating 20 tart cherries.

  • The incidents of immune system diseases has increased over 200% in the last five years.

  • The flu pandemic of 1918 killed over 20 million people.

  • Each year in America there are about 300,000 deaths that can be attributed to obesity.

  • Every three days a human stomach gets a new lining.

  • The first owner of the Marlboro Company, Wayne McLaren, died of lung cancer.

  • Soldiers disease is a term for morphine addiction. The Civil War produced over 400,000 morphine addicts.

  • Rocky Mountain spotted fever is a disease caused by ticks.

  • A person afflicted with hexadectylism has six fingers or six toes on one or both hands and feet.

  • A study indicates that smokers are likely to die on average six and a half years earlier than non-smokers.

  • A person who smokes a pack of cigarettes a day will on average lose two teeth every ten years.

  • Lady Peseshet is known to be the world's first known female physician. She practiced during the time of the pyramids, which was the fourth dynasty.

  • The DNA of humans is closer to a rat than a cat.

  • Teenage suicide is the second cause of death in the state of Wisconsin.

  • Teenage cosmetic surgeries nearly doubled in the USA between 1996 and 1998.

  • Studies indicate that weightlifters working out in blue gyms can handle heavier weights.

  • Studies indicate that listening to music is good for digestion.

  • Studies indicate that epileptic patients that listen to Mozart's Piano Sonata can dramatically decrease their chance of a seizure.

  • Lack of sleep can affect your immune system and reduce your ability to fight infections.

  • It takes about three hours for food to be broken down in the human stomach.

  • Over 40 million Americans have chronic bad breath.

  • Carbon monoxide can kill a person in less than 15 minutes.

  • Fourteen people die each day from asthma in the United States.

  • Every day the human stomach produces about 2 liters of hydrochloric acid.

  • Nearly half of all Americans suffer from symptoms of burnout.In humans, the epidermal layer of skin, which consists of many layers of skin regenerates every 27 days.

  • Native Americans used to use pumpkin seeds for medicine.

  • In ancient Egypt, doctors used jolts from the electric catfish to reduce the pain of arthritis.

  • The lining of the a person's stomach is replaced every 36 hours.

  • The purpose of tonsils is to destroy foreign substances that are swallowed or breathed in.

  • In the United States, poisoning is the fourth leading cause of death among children.

  • The risk of cardiovascular disease is twice as high in women that snore regularly compared to women who do not snore.

  • The stomach of an adult can hold 1.5 liters of material.

  • The stomach can break down goat's milk faster than the milk of a cow.

  • The smoke that is produced by a fire kills more people than a burn does because of carbon monoxide and other dangerous gases.

  • It has been medically been proven that laughter is an effective pain killer.

  • Influenza caused over twenty-one million deaths in 1918.

  • In a year, there are 60,000 trampoline injuries that occur in the U.S.

  • Even if you eat food standing on your head, the food will still end up in your stomach.

  • A person infected with the SARS virus, has a 95-98% chance of recovery.

  • 3000 children die every day in Africa because of malaria.                                                           
Pregnancy Facts

  • The world's first test tube twins are Stephen and Amanda Mays born June 5, 1981.

  • Some people drink the urine of pregnant women to build up their immune system.

  • The first known contraceptive was crocodile dung, used by Egyptians in 2000 B.C.

  • Every day, over 1,300 babies are born prematurely in the USA.

  • During pregnancy, the average woman's uterus expands up to five hundred times its normal size.

  • Changing a cat's litter box can be dangerous to pregnant women, as cat feces sometimes carry a parasite that can cause harm to the developing baby.

  • A pregnant woman's dental health can affect her unborn child.

  • May babies are on avearge 200 grams heavier than babies born in other months.

  • When a women is pregnant, her senses are all heightened.

  • Studies show that couples that smoke during the time of conception have a higher chance of having a girl compared to couples that do not smoke.
Other Human Body Facts

  • The Gastric Flu can cause projectile vomiting.

  • The Dutch people are known to be the tallest people in Europe.

  • Studies have shown that the scent of Rosemary can help in better mental performance and make individuals feel more alert.

  • Some brands of toothpaste contain glycerin or glycerol, which is also an ingredient in antifreeze.

  • Soaking beans for twelve hours in water before they are cooked can reduce flatulence caused by beans.

  • Scientists say that babies that are breastfed are more likely to be slimmer as adults than those that are not breastfed.

  • Scientists have determined that having guilty feelings may actually damage your immune system
    Research has indicated that approximately eleven minutes are cut off the life of an average male smoker from each cigarette smoked.

  • People have the tendency to chew the food on the side that they most often use their hand.

  • Over 600,000 people died as a result of the Spanish influenza epidemic.

  • Only one out of every three people wash their hands when leaving a public bathroom.

  • One ragweed plant can release as many as a million grains of pollen in one day.

  • One out of 20 people have an extra rib.

  • One average, men spend 60 hours a year shaving.

  • On average, falling asleep while driving results in 550 accidents per day in the United States.

  • On average, a person has two million sweat glands.

  • On average, Americans spend 33% of their life sleeping.

  • On average a person passes gas 14 times a day.

  • On average 1,668 gallons of water are used by each person in the United States daily.

  • Nerve impulses for muscle position travel at a speed of up to 390 feet per second.

  • Nerve cells can travel as fast as 120 meters per second.

  • Mummy powder was once thought to be a cure for all remedies. English men used to carry the powder with them in a tiny bag wherever they went.

  • Men in their early twenties shave an average of four times a week.

  • Medical research has found substances in mistletoe that can slow down tumor growth.

  • Medical reports show that about 18% of the population are prone to sleepwalking.

  • Manicuring the nails has been done by people for more than 4,000 years.

  • Left-handed people are better at sports that require good spatial judgment and fast reaction, compared to right-handed individuals.

  • Ironically, when doctors in Los Angeles, California went on strike in 1976, the daily number of deaths in the city dropped 18%.

  • In the United States, 8.5 million cosmetic surgical and non-surgical procedures were done in the year 2001.

  • People with darker skin will not wrinkle as fast as people with lighter skin.

  • People with allergies can lower allergy reactions by laughing.

  • People who meet their calcium need reduce their risk of developing kidney stones.

  • People that smoke have 10 times as many wrinkles as a person that does not smoke.

  • People still cut the cheese shortly after death.

  • People over the age of fifty will start to lose their dislike for foods that taste bitter.

  • People of Ancient China believed that swinging your arms could cure a headache.

  • The average weight of a newborn baby is 7 lbs. 6 oz. For a triplet baby it is 3 lbs. 12 oz.

  • The average person spends two weeks of their life kissing.

  • The average person falls asleep in about 12 to 14 minutes.

  • There are approximately one hundred million people in the United States that have a chronic illness.

  • There are approximately 60 muscles in the face.

  • There are 50% more males that are left handed compared to females.

  • There are 400 species of bacteria in the human colon.

  • There are 10 million bacteria at the place where you rest your hands at a desk.

  • In a lifetime, an average human produces 10,000 gallons of saliva.

  • In a lifetime, an average driver will release approximately 912 pints of wind inside a car.

  • In Canada, men are three times more likely than women to have seen a doctor in the last year.

  • In 1832, in Paisley, Scotland the first municipal water filtration works was opened.

  • Humans breathe in and out approximately one litre of air in ten seconds.

  • Girls have more tastebud than boys.

  • From the age of thirty, humans gradually begin to shrink in size.

  • Flu shots only work about 70% of the time.

  • Gases that build up in your large intestine cause flatulence. It usually takes about 30 to 45 minutes for these gases to pass through your system.

  • Fat is important for the development of children and normal growth.

  • Every day, the average person swallows about a quart of snot.

  • Eighty percent of 10 year old girls in the USA go on a diet.

  • Air is passed through the nose at a speed of 100 miles per hour when a person sneezes.

  • About twenty-five percent of the population sneeze when they are exposed to light.

  • A yawn usually lasts for approximately six seconds.

  • Children who are breast fed tend to have an IQ seven points higher than children who are not.

  • Children grow faster in the springtime than any other season during the year.

  • Eating chocolate three times a month helps people live longer as opposed to people who overeat chocolate or do not eat chocolate at all.

  • Constipation is caused when too much water is absorbed in the large intestine and poops become dry.

  • A ear trumpet was used before the hearing aid was invented by people who had difficulty hearing.

  • The average human dream lasts only 2 to 3 seconds.

  • The average person has at least seven dreams a night.

  • Bile produced by the liver is responsible for making your feces a brownish, green colour.

  • It takes more muscles to frown than it does to smile.

  • By the time you are 70 you will have easily drunk over 12,000 gallons of water.

  • A man named Charles Osborne had the hiccups for approximately sixty-nine years.

  • The average person walks the equivalent of twice around the world in a lifetime.

  • The average person laughs about 15 times a day.

  • The vocabulary of the average person consists of 5,000 to 6,000 words.

  • About 10% of the world's population is left-handed.

Pendrivelinux

Pendrivelinux is a Portable Linux Operating system that you can bring with you on a USB hard drive, flash pendrive, thumb drive, flash drive, ipod, phone or other mobile device. The 2009 version is available using coLinux to run in Windows. 

Tuesday, November 3, 2009

ANSWERS TO SELECTED QUESTION

1. What are the two types of transmission technology available? Explain in detail.

There are basically two types of transmission technologies available :

1. Broadcast: In this type every host sends the packet/message to all the hosts. The message has a source address and a destination address. Destination address helps the host to identify whether the message is indeed for them or somebody else. The source address allows them to identify from whom the message has come.

2. Point to Point: Point-to-point networks consist of many connections between individual pairs of machines. To go from the source to the destination, a packet on this type of network may have to first visit one or more intermediate machines. Often multiple routes, of different lengths are possible, so routing algorithms play an important role in point-to-point networks.

2. What Is a MAC Address? Explain in detail.

MAC address

The Media Access Control address (MAC address) is a unique identifier assigned to most network adapters or network interface cards (NICs) by the manufacturer for identification, and used in the Media Access Control protocol sublayer. If assigned by the manufacturer, a MAC address usually encodes the manufacturer's registered identification number. It may also be known as an Ethernet Hardware Address (EHA), hardware address, adapter address, or physical address.

They uniquely identify an adapter on a LAN. MAC addresses are 12-digit hexadecimal numbers (48 bits in length). By convention, MAC addresses are usually written in one of the following two formats:

MM:MM:MM:SS:SS:SS

MM-MM-MM-SS-SS-SS

The first half of a MAC address contains the ID number of the adapter manufacturer. These IDs are regulated by an Internet standards body (see sidebar). The second half of a MAC address represents the serial number assigned to the adapter by the manufacturer. In the example,

00:A0:C9:14:C8:29

The prefix 00A0C9 indicates the manufacturer is Intel Corporation.

Why MAC Addresses?

Recall that TCP/IP and other mainstream networking architectures generally adopt the OSI model. In this model, network functionality is subdivided into layers. MAC addresses function at the data link layer (layer 2 in the OSI model). They allow computers to uniquely identify themselves on a network at this relatively low level.

3. What is the difference between bit rate and baud rate?

The bit rate and baud rate are dependent and inter-related. But the simplest explanation is that a Bit Rate is how many data bits are transmitted per second. A baud Rate is the measurement of the number of times per second a signal in a communications channel changes.

Bit rates measure of the number of data bits (that's 0's and 1's) transmitted in one second in a communication channel. A figure of 2400 bits per second means 2400 zeros or ones can be transmitted in one second, hence the abbreviation "bps". Individual characters (for example letters or numbers) which are also referred to as bytes are composed of several bits.

A baud rate, by definition, means the number of times a signal in a communications channel changes state or varies. For example, a 2400 baud rate means that the channel can change states up to 2400 times per second. The term "change state", means that it can change from 0 to 1 or from 1 to 0 up to X (in this case, 2400) times per second. It also refers to the actual state of the connection, such as voltage, frequency or phase level).

The main difference of the two is that one change of state can transmit one bit - or slightly more or less than one bit, that depends on the modulation technique used. So the bit bate (bps) and baud rate (baud per second) have this connection:

bps = baud per second x the number of bit per baud.

4. What is the difference between baseband and broadband transmission?

In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal.

In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.

Baseband transmission

1) Uses digital signaling

2) No frequency-division multiplexing

3) Bi-directional transmission

4) Signal travels over short distances

Broadband transmission

1) Uses analog signaling

2) Unidirectional transmission

3) Frequency-division multiplexing is possible

4) Signal can travel over long distances before being attenuated

5.What is the difference between node, host, terminal, system and hub?

Hub: A network hub or repeater hub is a networking device that is used to connect several devices for a single network segment.

Fig. A HUB

It is a device for connecting multiple twisted pair or fiber optic Ethernet devices together and thus making them act as a single network segment. Hubs work at the physical layer (layer 1) of the OSI model. The device is thus a form of multiport repeater. Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it detects acollision.

Node: It can be any device connected to a network for example in a LAN, computers and printers can be called as nodes.

Host: It can be any end system connected to a network, for example it may be a computer, home security system, cell phone, printer, etc.,

Terminal: A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system.

System: The system includes not only the computer, but also any software and peripheral devices that are necessary to make the computer function. Every computer system, for example, requires an operating system.

6. What are the major types of networks? Explain.

Different types of (private) networks are distinguished based on their size (in terms of the number of machines), their data transfer speed, and their reach. Private networks are networks that belong to a single organisation. There are usually said to be three categories of networks:

LAN (local area network)

MAN (metropolitan area network)

WAN (wide area network)

LAN

LAN stands for Local Area Network. It's a group of computers which all belong to the same organization, and which are linked within a small geographic area using a network, and often the same technology (the most widespread being Ethernet).

A local area network is a network in its simplest form. Data transfer speeds over a local area network can reach up to 10 Mbps (such as for an Ethernet network) and 1 Gbps (as with FDDI or Gigabit Ethernet). A local area network can reach as many as 100, or even 1000, users.

By expanding the definition of a LAN to the services that it provides, two different operating modes can be defined:

In a "peer-to-peer" network, in which communication is carried out from one computer to another, without a central computer, and where each computer has the same role.

in a "client/server" environment, in which a central computer provides network services to users.

MAN

MANs (Metropolitan Area Networks) connect multiple geographically nearby LANs to one another (over an area of up to a few dozen kilometres) at high speeds. Thus, a MAN lets two remote nodes communicate as if they were part of the same local area network.

A MAN is made from switches or routers connected to one another with high-speed links (usually fibre optic cables).

WANs

WAN

A WAN (Wide Area Network or extended network) connects multiple LANs to one another over great geographic distances.

The speed available on a WAN varies depending on the cost of the connections (which increases with distance) and may be low.

WANs operate using routers, which can "choose" the most appropriate path for data to take to reach a network node. The most well-known WAN is the Internet.

7. Why should we care about the OSI Reference Model? What is the main purpose for creating this OSI model? Why it is a layered model?

We should care about this model because this was the 1st model to be created for internet standard. So this is an internet standard model and all the standards made after this model follow all the rules of this model too.

Main purpose for creating this model was to send data from one terminal to another terminal without any loss in the transmitted data.

It is a layered model because every layer is used for some specific work and it is not possible for one layer to handle all the tasks of transmitting data.

8. What is an email client? What is difference between email client and web mail?

Email Client:

Email clients download your emails onto your computer. Using a specialized email program such as Outlook Express or Apple Mail has the advantage of giving you complete control over your email; every email you receive is placed on your computer and you can keep as many large file attachments as you want.

Webmail:

If you host with Needmore Designs you have a limited amount of space available for your web mailbox. For daily use you will want to use an email client. Nevertheless you might find that you want to check your email while traveling.

Checking your email through our webmail is similar to using Hotmail or YAHOO! Mail. You never actually copy your messages to your computer; in fact you are looking at them through your web browser on somebody else's computer. When you are not online you are not able to see your email.

9. If a person is accessing his corporate network from home. How is the connection established and how does the data flow from internet to intranet?

If aperson wants to access his corporate network from home he have to establish a VPN (virtual private network):

He will require the following in case if want to connect by wireless technology:

· A notebook PC, Pocket PCs, or Tablet PC equipped with wireless WAN access cards or with built-in support for wireless WANs

· A wireless WAN card and WAN connectivity provider


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Step 1:

Set up VPN tunnelling into your corporate resources

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Step 3

Ensure secure wireless email transmission

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Step 5

Get a cost-effective data roaming plan

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Step 2:

Deliver wireless connectivity through your VPN

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Step 4

Choose a wireless service provider

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Step 6

Equip your computer or handheld for wireless WAN access

10. What is difference between dial-up internet connection and broadband connection?

The fundamental difference between dialup and broadband connections is the manner in which the connection is made from PC to the Internet.

A dialup service connects to the Internet through a phone line with a maximum speed of 56kbps.

Broadband refers to a connection that has capacity to transmit large amount of data at high speed. Presently a connection having download speeds of 256kbps or more is classified as broadband.

Broadband comes in a number of forms - depending how the data is delivered - for example via cable, satellite and most commonly using a telephone line where as a dialup service always connects to the Internet through a phone line.

While using a dialup connection, we need to pay for a local call every time we dial the Internet. In addition phone line is engaged while we are on the Internet. With a broadband connection, phone line (if existing phone line is used) can still be used while using the Internet and both the phone and the Internet work simultaneously and no dialup costs are incurred. Telecommunication systems were originally built to carry analogue signals. In a dial up connection, modems are used to translate digital into analogue signals and communicating with Internet.

Dialup connection speeds make it more difficult to view certain types of media, such as video, and it can take much longer to download and open emial attachments, play online games and so on.

In an broadband system, digital data does not have to be converted into analogue. it uses a different part of the line's frequency spectrum, offers much wider bandwidth 9more lanes) and does not interfere with the use of the line for voice transmission. When connected to the Internet, such a connection allows surfing or downloading much faster than a dial-up connection. Dialup connection users a built-in modem to connect and does not require a special router, whereas broadband requires a special router or modem.

In terms of security for attack, dialup is more secured then broadband, Broadband users need to use a firewall to keep the computer "invisible" to the outside.