We tend to overlook our skin, but it performs many vital functions for our bodies – including coming to our rescue in emergencies.

Since it is designed to function within very precise limits, our body is very susceptible to small temperature changes. Since abnormalities in these changes occur, the body has various mechanisms to keep its temperature constant. One of these mechanisms works by changing the amount of blood in the veins underneath the skin. When talking about body temperature, it is important to distinguish between the internal and external body temperature. The internal temperature is the temperature of the brain and internal organs, while the external body temperature is the temperature of the skin.

Normally, arteries that transport clean blood, and veins that carry dirty blood, are not connected; therefore clean and dirty blood never mix. However, as a consequence of some illnesses or birth defects, an abnormal bridge between arteries and veins may be present. This kind of condition is usually called arteriovenous shunts, or arteriovenous fistula. In these kinds of situations, blood is pumped directly from arteries to veins. In other words, clean blood flows towards dirty blood. Normally, the clean blood has to travel the body, providing oxygen and other supplements to cells, while collecting carbon dioxide and returning to the heart to be cleaned again.

An incredible network for the transportation of substances from the blood in arteries and veins has been created. If this system, known as the “capillary network,” did not exist, none of our organs could be fed, and the circulatory system would not be able to provide its vital function.

The system is necessary for two reasons. The speed of the blood in the arteries and veins is too fast for anything to be transported to the organs, and their walls are too thick to allow transportation of substances. Therefore, the blood travels from the arteries to the capillaries, and after the trading of oxygen and other substances with carbon dioxide is completed, it flows to the veins. If any kind of abnormalities exist, the blood flows directly from the arteries to the veins, therefore skipping the capillaries. As a consequence, the organs aren’t fed and the blood gathers in the veins without fulfilling its purpose. Naturally, the oxygen and nutrition balance of the organs gets messed up. The blood is pumped out of the heart with no purpose and heart failure becomes inevitable.

The capillary network has been assigned the task of communication between arteries and veins. The skins is our only organ where the blood flows directly from arteries to veins; AV shunts accomplish a very important duty in this function.

There is a network of veins underneath the skin. The number of veins in this network is so many that if they were completely filled up, they could hold up to two liters of blood in the skin. Blood is pumped to the skin for two purposes: to provide oxygen and nutrients to the cells, and to collect carbon dioxide and waste products in the cells, as is done with every organ; and to monitor the internal temperature of the body by sending blood to the skin if the temperature gets too high, similar to what radiators in cars do when the engine gets too hot.

There is also the subcutaneous fat tissue underneath the skin which acts as an insulator. The vein network mentioned above is inside this fat tissue. There is a continuous flow of blood from the capillaries that feed the skin towards this network of veins. Moreover, especially in areas where the skin is exposed – such as the hands, feet, face and ears – there is a blood flow from the small arteries towards this network of veins. Contrary to other organs in the body, blood flows directly from the arteries to the veins. If this direct blood flow did not exist, the amount of blood in the skin’s veins would be close to zero, because the amount of blood necessary for skin nutrition is very little. However when the internal temperature rises too much, the amount of blood, which is normally close to zero, can suddenly increase to as much as 30% of the blood pumped by the heart. In this case, the body’s internal temperature is being transported to the skin. This is an incredibly efficient cooling system. However, if the weather is cold, the AV shunt veins are switched off and the skin’s blood flow is decreased until close to zero, therefore maintaining internal temperature. The fat tissue underneath the skin also has a very important function, as it acts as insulation, helping maintain temperature.

Body temperature and the body’s systems work in perfect coordination with each other. We can observe a very simplified version of this system in computer based air conditioners. However, when we reflect upon the incredibly sophisticated cooling system of the human body, we come to the conclusion that no other system is as perfect as that.

The hypothalamus, which has various vital duties for the brain, was also given the very important mission of controlling the body’s temperature. There are hot and cold heat receptors in various parts of the hypothalamus. When body temperature increases, these receptors are activated. As a consequence of this warning, skin veins all over the body expand. Simultaneous with the expansion of the veins, sweat is excreted.

The hypothalamus also has the duty of suppressing the mechanisms that produce heat throughout the body. For example, trembling is stopped and general metabolism is slowed down to decrease body temperature. As metabolism slows down, the production of heat becomes minimal, and cooling takes place. In conditions where the body temperature is too cold, some hormones secreted in the hypothalamus trigger the pituitary, and then the thyroid, hormones. Since thyroid hormones are responsible for increasing metabolism, body temperature increases. However if body temperature increases above normal, the control of the hypothalamus on the thyroid is reversed, and thyroid hormones are decreased, therefore decreasing body temperature.

There is one more reason for placing so many veins in the perfect and miraculous body’s skin: except for extremely cold weather conditions, quite a large amount of blood exists in these veins that are not used for nutritional purposes. Some of our organs act as storage for blood; two of the most important ones are the spleen and liver. Another one is the skin. In the course of losing blood, or an illness that increases the need for blood, the spleen and liver shrink. As a consequence of this shrinkage, the blood inside them is sent to the heart, through veins, and distributed to the areas in need of blood. This increases the heart rate.

A similar scenario occurs in the skin. The veins responsible for cooling shrink, and the blood they contain is sent to the heart with the help of the main veins, therefore helping the heart pump. During heavy loss of blood, the blood in the skin comes to the rescue. Patients who are losing blood have incredibly cold and pale skin. This is because the blood in the skin has reduced to a minimum.

The obverse of this happens in an illness called erythromelalgia, where more blood than normal flows from the arteries to the veins in the skin. This is mostly seen in the hands, feet, nose, and ears, since AV shunts are more prevalent in these areas of the skin. The symptom of this illness is burning pain, which is triggered by heat and soothed by cool temperatures. The nutrition of the skin decreases and some substances produced because of the absence of oxygen increases redness, heat, and pain, since some of the capillaries feeding the skin shut down and all of the blood flows from arteries to veins with the AV shunts.

Our skin protects our muscles and bones, and contributes to the beautiful aesthetic of our body. It provides our sense of touch, and is therefore a means for us to experience the material world, as well as providing temperature control for our bodies. It can clearly be seen that the relationship between the skin and the veins could not have evolved by the consequence of coincidence.

“The human brain, then, is the most complicated organization of matter that we know.”
Isaac Asimov

If someone asks what you recall when you look at the following pictures, I can hear you say ‘President Obama’ and ‘Statue of Liberty’. You just see a fragment of the pictures and remember them.

So, how does it happen? This is just a simple task for the brain. It stores an image and retrieves it whenever a part of it is seen. Amazing features of the brain, especially its power to learn and make decisions, inspires computer scientists in the field of artificial intelligence.

In computer science, an artificial neuron is a simple computational model of a neuron in the brain that excludes biological properties. Artificial neural networks (ANNs) are composed of artificial neurons, and they are utilized to solve specific problems, especially those that require learning and decision-making. ANNs may not be the best solutions in various machine learning problems; however, they are accepted as strong alternatives. Although ANNs don’t claim to be so, currently they are not even close to producing a simple model of the brain. Let’s take a short journey into the world of ANNs to experience the extreme difficulty of modeling the brain.

Some Applications of ANNs

Figure 1: Overview of ALVINN structure. Images obtained from the camera installed on the vehicle are provided to the ANN, and ANN decides the steering angle.

(adapted from: http://virtuallab.kar.fei.stuba.sk/robowiki/images/e/e8/Lecture_ALVINN.pdf).

ANNs have various applications in very large spectrum of problems that require learning, such as the Autonomous Land Vehicle in a Neural Network (ALVINN). The structure of ALVINN is shown in Figure 1. The ALVINN project by Carnegie Mellon University started in 1986 and aims to make a vehicle without a driver (Mitchell, 1997). In this project, ANN learns the steering habits of a driver. A camera is mounted on the vehicle to capture the images of the road. With respect to the continuous images provided, ALVINN determines the steering level with 45 different angle positions from sharp left to sharp right. Steering is updated 15 times per second so that it allows real-time control while driving at 55 mph. The system is trained by the data obtained from a human driver in a simulator and a real vehicle. ALVINN was able to speed up to 70 mph and successfully drive at 55 mph for 90 miles.

Figure 2: Handwritten zip codes (LeCun, et al., 1989)

Another example is handwritten zip code recognition (LeCun, et al., 1989). Zip codes from US Mail written by various people with large variety of styles and sizes were used in the experiments. Figure 2 presents some examples of zip codes in the experiment database. After the ANN was trained with more than 7,000 digits in the zip codes, it was 99% successful in recognizing around 2,000 digits in new zip codes.

Learning and Decision-making in ANNs

In order to understand the challenges better, we will first examine learning and decision-making in neurons and ANNs on simple examples.

Figure 3: (a) A typical neuron (adopted from http://commons.wikimedia.org/wiki/File:Neuron_-_annotated.svg), (b) artificial neuron in computer

Figure 3(a) illustrates a typical neuron which is the constituent of brain’s complicated network structure. Each neuron receives information as signals via dendrites, then evaluates it and generates a signal that is transmitted through its axon. A neuron has many connections between its dendrites and the axons of various other neurons. Figure (b) demonstrates an artificial neuron in computer science. It is considered a function: dendrites as the inputs of the function and generated signal via the axon as the output of the function.

Let’s see an example of an artificial neuron that understands if a given produce is a red apple or not. Think about how you understand whether a produce is a red apple or not. You see the shape and the color. However, it might be an artificial one for decoration. Then you can taste it and you get the sweetness of the apple. Similarly, our neuron receives three pieces of information as the input; ‘has circular shape?’, ‘is sweet?’, and ‘has red color?’. If the output is ‘yes’, that means the neuron recognizes the produce as a red apple. Otherwise, it will be ‘no’, which means the produce is not a red apple (Figure 4). Here, the neuron’s function is defined in such a way that it only generates ‘yes’ when all the inputs are ‘yes’.

Figure 4: Example inputs and outputs for the artificial neuron.

In an artificial neuron, some of the information can be more important than the others. For instance, to have red color may be more valuable in determining the price of produce. Assume that round shape and sweetness has equal value of $1; however, having red color is $2 – twice as valuable as the other features (Figure 5).

Figure 5: Artificial neuron with different input weights. Arrow thickness indicates the importance.

So, what is the big fuss about artificial neurons if they are only functions? In fact, the main feature of artificial neurons is learning. Considering the last example above, the neuron initially does not know the importance of the dendrites, i.e. the weights of inputs are all the same. If not trained, the neuron will generate the following answers which are sometimes wrong as indicated in Table 1.

Table 1: Artificial neuron before training; highlighted answers are wrong.

In real life, a teacher trains students. For instance, the teacher asks a question and if the received answer is not correct, she provides the right answer. Students learn the right answer and use this correct information in their lives. It is similar in artificial neurons as depicted in Figure 6. When the response of the neuron is incorrect, it adjusts the importance of the dendrites with respect to the correct answer hence it answers the same question correctly next time. During the training session, the neurons will be continuously asked the values of all the produce until it learns them all.

Figure 6: The learning process of the artificial neuron.

What if the problem gets complicated? Then one artificial neuron will not be sufficient, and we will need a network of neurons; ANNs. A more complex problem, ‘learning the digits’ is indicated in Figure 7.

Figure 7: (a) Digit learning problem, (b) ANN structure that learns digits. Due to the difficulty, only the connections between the input layer and first / last neurons in the middle layer are shown.

ANN has 3 x 5 = 15 input units like receptors of an eye retina. Each input unit corresponds to one square in the digits; either filled or blank. Each input unit is connected to the dendrites of all neurons in the middle layer. The output of each cell in the middle is connected to the dendrites of all neurons in the output layer. There are 10 output neurons corresponding to the digits from 0 to 9. After the ANN is trained, it provides a correct answer to the given digit as input. When digit ‘3’ is provided to the network, the neuron labeled with number ‘3’ in Figure 7(b) is triggered and outputs ‘yes’ whereas the rest of the neurons output ‘no’.

Figure 8: Faulty digit ‘3’ with a missing black square on the top right side.

Initially, all neurons in the network have equally weighted dendrites. After a reasonable amount of training, neurons adjust their weights, and ANN is able to identify digits. Here, we have some major challenges: what does ‘reasonable amount of training’ mean? When the ANN is undertrained, it will not always answer correctly to the digits given in Figure (a). In the other case, when the ANN is overtrained, it will memorize the digits provided during the training and will not recognize the faulty ones such as the one in Figure 8.

Challenges of ANNs

Beyond the mentioned the overtraining / undertraining problems, ANNs have a bigger challenge – how to determine the structure of ANN that fits the problem? In the digit learning example, we’re lucky because the structure is provided in Figure 7(b). However, the outcome of the solution may drastically depend on the number of neurons and the connections among them which is indeed a hard problem for ANNs.

The huge capability of the brain in learning and decision making comes from the huge number of neurons – around 100 billion – and the enormous amount of connections among them – from 100 to 500 trillion. The challenge to design such a huge network requires huge computation power. With the increasing number of neurons, ANN dramatically slows down especially during the learning process. Here, our example is a simple learning task of 3×5 pixel digits compared to the brain’s acquisition capacity of hundreds of images in our daily life. 

When the number of neurons gets larger, the reliability of network also reduces. Small adjustments in weights may change the entire behavior of the network hence it is easy to lose control of ANN. In contrast, the brain has a robust system, and its fault tolerance is admirable. Although neurons die every day, this doesn’t affect its performance significantly. The training method and how to update the weights are other hard problems leading to many different approaches in the neural computation field.

We have presented some simple tasks that can be solved using a few neurons and their challenges. On the other hand, consider the thousands of problems, various and incredible amount of information we have learned, and the thousands of decisions we make. The brain is truly amazing from the computer science perspective.

Bibliography

• Hertz, J. A., Krogh, A. S., & Palmer, R. G. (1991). Introduction To The Theory Of Neural Computation. Reading, MA: Addison-Wesley.
• Hopfield, J. J. (1982). Neural networks and physical systems with emergent collective computational properties. Proceedings of the National Academy of Sciences of the USA , 79, 2554-2588.
• LeCun, Y., Boser, B., Denker, J. S., Henderson, D., Howard, R. E., Hubbard, W., et al. (1989). Backpropagation applied to handwritten zip code recognition. 1 (4), 541-551.
• Mitchell, T. M. (1997). Machine Learning. McGraw-Hill.

We vessels can be divided into three main groups in terms of structure and function. The ones with thicker walls, which bring every organ the blood they need from the heart, are the arteries. The pressure inside us is higher and we easily carry blood to the organs. The ones with thinner walls, lower pressure, and larger inner space are called veins. As a matter of fact, both arteries and veins have a three-layered structure that is very suitable for holding a fluid like blood. Since our walls are strengthened with both connective tissue and smooth muscle layers, we bear the pressure coming from the heart and help blood proceed by contracting and relaxing. Since arteries are directly subjected to the strong pressure from the heart, our walls were created in a thicker and stronger form. Since the veins return blood to the heart and thus have lower pressure, we have valves that close after blood passes, so it does not flow backward due to gravity. This is a serious challenge for the blood passing through your legs. Varicose veins might develop due to weight gain from pregnancy or obesity, which increases pressure on the legs, or to hours of standing, walking, or running on hard surfaces.

Capillaries are the most delicate blood vessels, with walls made of a single layer of epithelium, which enables us to exchange substances between blood and tissues. As blood vessels, our total length is about 120,000 kilometers. Try to imagine if a fisherman’s net were made from a rope of this length and how wide it would be! And yet, such a vast network of blood vessels is located in your body, and capillaries take blood to every part, without neglecting an area as tiny as the head of a pin.

The well-being of your organs is directly related to us. If our interiors begin to narrow, because of fatty cholesterol plaque for instance, then we begin to lose our flexibility. This means malnutrition for that organ, since a lesser amount of blood than expected can come. If a blood clot sticks to our wall and blocks the blood flow, the relevant organ may be in terrible trouble. If other arteries supply blood to that organ, then it can handle this, but if a main artery is blocked and if secondary channels do not exist or are insufficient, you experience infarction. Taking this into consideration, you need to be careful what you eat and lead a physically active life. When you get old, if sufficient blood does not pass through us in your brain, failures with brain activities appear and you go senile. As the walls of veins and arteries have a rich network of nerves, we let the suitable amount of blood flow according to the need of the organ we’re serving, under the control of the autonomous nervous system. While blood vessels that are connected to an organ not currently requiring much blood contract to reduce the amount supplied, those that are connected to currently more active organs expand. And dear Peter, the greatest blessing here is that none of these activities require any conscious effort from you; everything works smoothly without your even being aware.

This wonderful network of ours finds its value in the vital fluid we carry. If it weren’t for blood, we would have no value at all, and such a perfect means of distribution would be unnecessary. Even the duty of the heart is to make this fluid circulate throughout the body. Now, let us step aside and allow blood to have the floor.

This time, with your permission, I won’t be talking about the last two weeks that I have spent in this alien city, as I usually do. Instead, I feel obliged to reflect on your anger at the fact that your father did not use the opportunity he had during his youth to become a medical doctor. What I’m going to tell you has been said by many great thinkers in the past, but I want to bring their words up-to-date and relate them to my studies here. I hope to give you an alternative understanding of tolerance by using the idea of networks.

As commonly defined, networks are web-like maps of nodes that represent entities and links that connect the nodes and represent their interactions. Networks have become very popular these days, and are used to analyze everything from ecology and biochemistry to social infrastructures.

Try to visualize your father 30 years ago in a large network that consisted of his two brothers and three sisters, his fiance of 2 years standing, maybe a very close friend who had recently died, maybe another friend who already had had a child, along with the fear of leaving his hometown for the first time, and so on. All of us, including your father, are surrounded by such factors all the time. Perhaps your father could have overcome some of them, like his fear of loneliness or impatience, but he certainly could not have overcome all of them, because his family, surrounding events, and many other factors existed on their own and didn’t develop according to your father’s will.

Upon further reflection, however, maybe none of these factors, even the trivial ones, were ever in his grasp and thus were never under his control. Let’s think back even further. When your father was in the womb, he had only one obvious link with the world: his mother. But wait a minute, you might ask, didn’t he have other links, such as his genes, family, and birthplace? Of course, you would agree that your father had no choice in any of these crucial factors. Moreover, I don’t think that it’s hard to accept that, for example, his impatience was probably the result of his cultural make-up, genes, interactions with his family members, and other things. As you know, all of these were independent of your father’s will. Thus, your father, and indeed every person, was born into a predetermined world, one in which most choices had already been made for him. Moreover, these initial determinations had an undeniable impact upon the rest of his life and decisions.

Imagine a circle in the center of a big picture. The circle is you, and the picture represents your life, or else all of the interactions that you make during your life. As mentioned above, even in the very beginning, that circle is not unique. Now imagine a few more circles which represent your family members and hometown, and draw a line from each circle to yourself. This is you in the beginning. Without a doubt, soon some circles will fade away and other circles will appear in a continuously regenerating network. Let this little human being live in this world (morph his network, as we say) for some years and, in the end, you’ll obtain a dreadfully complex picture that is almost impossible to understand.

Nevertheless, let’s consider for a moment the evolution of this self-network. At each decision point, we make a choice that is influenced by our personal self-network, defined as a collection of those choices over which we had no control and those which we made due to our personal network at that time. This recursive definition of self, which is entirely reasonable, makes it impossible for us to judge other people’s behavior, for we can never know if such behavior is the result of free will or of the previous self-network. We find it easy to criticize students who drop out of school, or behave anti-socially, or sleep all day. But maybe they had no other option in the context of their self-network. If this is the case, criticizing them is almost like criticizing a fish because it cannot fly. It is quite possible that no alternative choices were within their reach.

The key observation lies in this: When we see a person do something that we don’t like, we don’t know and can never know how much his or her self-network has influenced that specific act. Therefore, my friend, who are we to judge other people’s acts unless we have this kind of knowledge? Given this, if we want to be true to ourselves, what other alternative do we have but to exercise complete tolerance toward others?

Before going on, however, I should stress that I am talking about tolerance for acts that don’t violate other people’s rights and freedoms. In addition, I’m talking about personal tolerance only, for obviously everyone must follow the law for the sake of society. For example, a thief should be punished according to the law. Therefore, given that there are many underlying reasons for a person’s act, we should hesitate before passing judgment, for it benefits both of us if we are tolerant. As shown above, this is not only a more pragmatic, but also a more rational approach.

The world’s great religions and great minds have said such things many times. For example, we read in the Bible: Judge not, that ye be not judged (Matthew 7:1) and Therefore thou art inexcusable, O man, whoseoever thou art that judgest… (Romans 2:1). The great Hellenistic philosopher Epictetus says: If a man drinks much wine, do not say that he drinks badly, but that he drinks much. For till you have decided what judgment prompts him, how do you know that he acts badly? 1 Even more, another Biblical verse states: Therefore judge nothing before the time, until the Lord come, who both will bring to light the hidden things of darkness, and will make manifest the counsels of the hearts: and then shall every man have praise of God. (I Corinthians 4:5). This verse supports tolerance, for it tells us that we should have comprehensive knowledge of a person before judging their acts. Such knowledge, as we all know, is possessed only by God.

An interesting result of considering individuals as nodes located in the center of a complex network occurs when we try to influence a person’s views, acts, and beliefs. In order to appreciate how difficult (if not impossible) this is, imagine the self-network of the person you want to influence, with all of his or her beliefs, memories, friends, as well as all of the nodes acquired while morphing his or her self-network.

Now imagine the fraction of nodes in that self-network that are directly related to you. I don’t think that you’ll claim to be a big part of that person’s life, unless both of you have been on intimate terms for quite a while. The proportion of the nodes that you represent in his or her self-network can be quite an accurate measure of how much influence you will have. For example, you can alter a lonely or a simple person’s beliefs in a shorter time, since in a short time you can become a large proportion of his or her self-network.

By the way, you might be amazed to hear that the English mathematician Thomas Bayes (1702-61) tried to formulate quantitatively how a person’s beliefs would change upon receiving new information that contradicts his or her previous beliefs. In a Bayesian analysis, a set of experiences (in our case, links) are seen as something that influences opinion and decision. I won’t discuss this further, however, since it’s beyond both my and this letter’s scope.

In my opinion, the reason why we almost always criticize and blame others, and constantly see faults in everybody else is because we refuse to make an honest self-criticism; that is to consider our own responsibilities, not those of other people.

Forgive me for saying this, but you want to achieve a better quality of life now; this is something for which you have to work really hard. Yet, if your father had become a doctor, you probably would already be living this better life, and so you wouldn’t have to push yourself. Hence, we can find a convenient scapegoat in your father, who, for whatever reason, didn’t set you up with such a life!

Another example, one in the future, might be that a person explains his/her beliefs in the hope of influencing someone else. Unable to convince this person, he/she blames that person for not opening their heart and really listening. Easy, isn’t it? However, remember that you can’t really influence a person if you are not a large part of his or her life.

Do you see what’s missing in this picture? Reality and, more than that, a solution. It lacks reality, for we can never hold someone absolutely responsible for anything. And why not? Because we have no way of knowing which actions were based upon free-will and which ones were the result of his or her prior self-network. By blaming others, regardless of whether we are correct in doing so or not, we not only contradict reality, we also ignore our own mistakes, closing the roads to a solution that could come from ourselves, and taking a passive position of stagnancy that, I think, won’t make a better world for ourselves or anybody else.

Before ending, I’d like to apologize if some of my words sound harsh. However, I consider you a true friend who will appreciate my openness. Even if some of my words have upset you, perhaps you’ll be patient with me. For this to be, before blaming me, stop for a moment and try to look at this situation from another perspective. Try to find some truth in my words, and try to be hard on yourself. Below are some extraordinarily beautiful lines from Nietzsche, which I think are appropriate to our discussion. He writes:

Why so hard? the kitchen coal once said to the diamond. After all, are we not close kin?

Why so soft? O my brothers, thus I ask you: are you not after all my brothers?

Why so soft, so pliant and yielding? Why is there so much denial, self-denial, in your hearts? So little destiny in your eyes?

And if you do not want to be the destined inexorable ones, how can you one day triumph with me?

And if your hardness does not wish to flash and cut through, how can you one day create with me?

For all creators are hard. And it must seem bliss to you to impress your hand on millennia as on wax, bliss to write on the will of millennia as on bronze harder than bronze, nobler than bronze. Only the noblest is altogether hard.

This new tablet, O my brothers, I place over you: become hard!2

Yes my friend, become hard, very hard on yourself; and soft, very soft towards others.

Footnotes

1 Epictetus, The Discourses of Epictetus, tr. P. E. Matheson (New York: Heritage Press, [1968]).

2 Friedrich W. Nietzsche, Thus Spoke Zarathustra, tr. Walter Kaufmann (USA: Viking Penguin, 1966), 214.

In his Models of My Life, social scientist Herbert Simon stated that science’s purpose is to find meaningful simplicity in the midst of disorderly complexity. Although the systems in nature and society seem to be very complex, we need simple theories to understand them. The key to finding these simple rules or principles, which Plato called perfect form and thing-in-itself and Kant described as a kind of untouchable essence behind physical things or systems, is mathematics.

Mathematics and social science

One of mathematics’ main challenges is its uses in social sciences. But does mathematics, which is considered rigid and restrictive and the best tool for explaining matter, have laws for human life? The latest studies in sociology, biology, and epidemiology show that such laws and meaningful patterns do exist and can be discovered. One of the great achievements of mathematics and physics in sociology is explaining the six degrees of separation (i.e., the small world) phenomenon.(1)

Almost everyone has met someone far from our home who is a friend of a friend. This is so common that it has become a clich: It’s a small world “ even though there are now more than 6 billion people. Even more surprising is the structure of social networks, the map of who knows whom, which shows that all people are closely connected.(2)

A social network is a collection of people, each of whom is acquainted with some subset of others. This can be represented as a set of points (nodes) denoting people, joined in pairs by lines (edges) denoting acquaintance, in a company, university, or even a global community. Social scientists have studied such networks, both empirically and theoretically, for at least 50 years.

A revealing experiment

One of the first and famous empirical studies was conducted in 1967 by Stanley Milgram, a Harvard psychology professor: the small world phenomenon. He asked: Starting with any two people in the world, what is the probability that they will know one another? In a large social network, although X and Z might not know each other, they might have a mutual acquaintance. Moreover, X might be linked to Z by a series of links. In other words, X knows a, who knows b, who knows c … who knows y, who knows Z. But how many intermediate acquaintance links are needed, on the average, to connect X and Z?

According to Milgram (3), this phenomenon raises the issue of a certain mathematical structure in society, one that often plays a part in discussions about history, sociology, and other disciplines. For example, during western Europe’s Dark Age, cities became isolated because inter-city communications broke down and thus severely limited the network of individual acquaintances. Thus, social disintegration was expressed in the communities’ growing isolation and people’s infrequent contact with non-local people.

Milgram asked his test subjects, chosen at random from Nebraskan and Kansan telephone directories, to get a letter to one of his Boston stockbroker friends. The letters were to be sent passing them from one person to another, but only if both parties were on a first-name basis. Since it was unlikely that the letter’s initial recipient and a Boston stockbroker would be on a first-name basis, their best strategy was to pass the letter to someone whom they felt would be socially or geographically closer to the stockbroker.

A moderate number of the letters eventually reached their destination. Milgram discovered that the average number of steps in this process was about six. This is usually considered evidence of the small world hypothesis: Most pairs of people, even in a very large population, can be connected by a short chain of intermediate acquaintances.

Milgram’s work passed into folklore and was immortalized in John Guare’s 1990 play Six Degrees of Separation, where Ouisa claims: Everybody on this planet is separated by only six other people. Six degrees of separation. Between us and everybody else on this planet. The president of the United States. A gondolier in Venice…. It’s not just the big names. It’s anyone. A native in a rain forest. A Tierra del Fuegan. An Eskimo. I am bound to everyone on this planet by a trail of six people. It’s a profound thought…. How every person is a new door, opening to other worlds.(4)

Watts and Strogatz used this model to explain the six degrees of separation in society- and nature-based networks.(5) Their model employs mathematical graph theory, which consists of nodes (people) and links (acquaintance). They modified the regular network, in which every node has short-range fixed number of connections, by adding long-range connections to the regular network to simulate the short path length between nodes. This model is now used in such areas as networks connected with biological metabolism, genomes, proteins, the Internet backbone, power grids, companies, and the stock market.

Research on social networks has helped health professionals understand how epidemics spread. Epidemiological models help them to predict how fast a disease will spread and to develop small world theory strategies to combat them, for scientists now realize that this social network property is a main cause for the outbreak of epidemics. This network offers a super-connected web of stepping stones for infectious diseases. After analyzing the social network’s structure, public health specialists can devise new vaccination strategies to slow or stop the epidemic. The small world theory also explains the rapid spread of news, rumors, fashions, and gossip.

Other types of systems show similar properties: networks of actors involved in the same movie, scientific collaboration networks of scientists who coauthor an article, and even the Internet, where millions of web pages are connected via mutual links. Recent research shows that in all of these networks, there are only a few steps between one node and any other node. The average shortest path between a network’s nodes, is 3.5 for the actor network and 9.5 for the scientific collaboration network. Despite the Internet’s more than 800 million nodes, there are, on average, only 19 steps between one web page and any other.(6)

Conclusion

The small world theory is a great success of the theory of complexity in nature and social life. It reveals an underlying dynamic of interconnectedness that expresses itself indelibly in who we are and how we think, behave, and communicate. Such close interconnectedness reveals one important fact for constructing a peaceful and beneficial world: There are no strangers, for everyone is one of our friends’ or neighbors’ friend or relative. The key element in understanding people is communication. Mutual love and good relations continue as long as we understand each other. We are loyal and faithful to the extent that we share our friends’ troubles, because ignorance only builds an impenetrable wall between us.(7)

Hasan Guclu is a doctoral student in the field of very large complex systems, such as computer networks, social networks, epidemics, and surface growth.

Footnotes

1. See, respectively, A. L. Barabasi, Linked (Perseus Publishing: 2002); D. J. Watts, Small Worlds (Princeton University Press: 1999); and M. Buchanan, Nexus (W. W. Norton: 2002).
2. D. J. Watts and S. H. Strogatz, Collective Dynamics of Small World Networks, Nature 393 (1998):440-42.
3. S. Milgram, The Individual In A Social World (Addison-Wesley: 1977).
4. J. Guare, Six Degrees of Separation: A Play (Vintage: 1990).
5. Watts and Strogatz, Collective Dynamics.
6. A. L. Barabasi, Linked.
7. F. Gulen, Pearls of Wisdom (The Fountain: 2001).

God willing, you are to be an expert hardware specialist or a good-quality programmer or a first-class network builder or a high-quality system administrator by now

But ever bear these important points in your mind: This Universe has such a Hardware Engineer who created all beings and the Earth as well; He made Sun a Power Source, Moon a System Clock. Such an Uninterrupted Power Source and such a System Clock that never goes astray and is never confused, so as to show the vast knowledge and the art of that Hardware Engineer.

This Person, at the same time, is such an Exalted Programmer who composed and assembled the gigantic Software called Life in the best way to operate on this vast globe, and has been operating it for millions of years; error-free, bug-free and devoid of any system crash. If you want to know how an Exalted Programmer He is, take a good look at yourself at the outset:

He saved your entire life code into one of your microscopic, infinitesimal cells, which you cannot see with naked eyes, and He too executes that code in that same minuscule cell of yours. Since it is obvious as clear as the daylight that the DNA is a program, and a program cannot exist without its Programmer, therefore your programming is like a mirror to that Exalted Persons Art of Programming.

Again, as he makes those cells communicate through innumerable protocols within your network which He made up of your entire cells, and since He also bestowed on you the essential hardware along with you to enable you to converse with another people in various languages and protocols, he also makes you see, talk and listen as before. And since, He prepared and enabled you to use various media such as light and sound, so that you can come to know about the things around you “ and you can discover and utilize those things, but you cannot add a new component “ hence there is such a Great Network Resource Person who knows what you need and gives your equipments as per your requirements. Your flair of networking is only a little piece bestowed on you by Him out of His infinite knowledge and a great blessing.

O my friend, do not be deceived! This beautiful World Life Software is just a trial version, as you can see; in any case you cannot save the properties and treasures that you hoarded so far. Therefore, know the Writer of this Beautiful Software of the Universe. Is it ever possible that a programmer to build up such a beautiful program, and never include an about file to introduce Himself? Therefore; see and learn the About files, which have been included by the Greatest Programmer, Hardware Expert, Network Professional and the System Administrator of this Universe, and work for acquiring the Full version of the Software. Do not forget, without skipping any of your actions, log files are being carefully saved in the background. These log files are going to be checked by that System Administrator, whose Power envelopes every being. O Man: If you are a Human, do not mix nature, coincidence, absurdity, and unbelief into these beautiful tasks; do not make it ugly, do not perform it ugly and do not be disgusting!

Useful Links: Organizations devoted to the academic study of religion and interfaith research and activities have found a home on the Internet. Have a look at:

www.conjure.com/religion.html; www.theorderoftime.-com/cyber/to/rs-file/interf.html; www.interfaithclergy.org/ links.html; http://religion.rutgers.edu/vri/academic.html, www.fefadmin.org/interfaith_links.htm; www.beliefnet. com/index/ index_102.html, and www.academicinfo.net/

Religionmeta.html. We encourage our readers to take part in their activities and online discussions.

North American Interfaith Summit: The United Religions Initiative (URI), a global network of grassroots-based interfaith groups, is holding its first North American summit, “Circles in Motion-Gifts to Share,” May 31-June 4, at Salt Lake City’s 2002 Olympic Village. Contact Kay Lindahl, URI-North America, P.O. Box 6071, Laguna Niquel, CA 92607; Tel: (949) 661-3087; Fax: (949) 496-5535; e-mail: theasc949@aol.com; or visit www.uri.org.

Interesting Books: Huston Smith, Why Religion Matters: The Fate of the Human Spirit in an Age of Disbelief; Andrew Newberg M.D. et al., Why God Won’t Go Away: Brain Science and the Biology of Belief; Gerald L. Schroeder, The Hidden Face of God: How Science Reveals the Ultimate Truth; William A. Dembski and Michael J. Behe, Intelligent Design: The Bridge Between Science & Theology; Jensine Andresen (editor) et al., Cognitive Models and Spiritual Maps: Interdisciplinary Explorations of Religious Experience; Joel Beversluis (editor), Sourcebook of the World’s Religions: An Interfaith Guide to Religion and Spirituality. -www.amazon.com.

IN SOCIETY

Interfaith Network: The United Communities of Spirit is a global interfaith network linking people of diverse faiths and beliefs who want to work with others to build a better world. In its quest to promote awareness that all people belong to the same spiritual family, it offers e-mail/web conference facilities and an extensive database that allows members to express the fine details of their personal beliefs. – http://origin.org/ucs.cfm.

Ecological Medicine: As more people realize that health and environment are interlinked, interest in ecological medicine continues to increase. Kenny Ausubel’s “The Coming Age of Ecological Medicine” (The Utne Reader, 27 July 2001) deals with this topic. In it, Carolyn Raffensperger, executive director of the Science and Environmental Health Network (SEHN), says that ecological medicine seeks to establish the conditions for health and wholeness, acknowledges that people are part of the local ecosystem, and that medical practices should not damage other species or the ecosystem. SEHN calls upon science and industry to conduct impact studies before implementing their activities. Raffensperger claims that this usually is not done, and that the results are disastrous. – www.utne.com.

The “Benefits” of Smoking: Philip Morris reports that deaths from smoking saved the Czech government at least $30 million on health care, pensions, and housing for the elderly; that smoking had a positive effect on the nation’s 1999 public finance balance (estimated at $146 million); and that smoking-related expenses of $394 million (1999) were “almost exactly balanced out by the excise duty charged by the Czech government.” Moreover, the government benefited from value added tax of $89 million, customs duty of $9 million, and income tax from tobacco businesses in the Czech Republic of $19 million. Spokesman Remi Calvet said that: “We deeply regret any impression that premature death of smokers could represent a benefit for society. Tobacco is a controversial industry, but we are still an industry and sometimes we need some economic data on our industry.” – http://washingtonpost.com.

IN SCIENCE

Free Space Optics: Researchers are studying the possibility of replacing underground cabling with free space optics, a system that uses invisible focused lasers to transmit data. Speeds of up to 1 gigabit per second, faster than any other broadband connection now available, are possible. Several problems remain to be solved, though: automatic refocusing of laser connections, ensuring a clear line of sight, and how to deal with fog and other weather conditions that could disrupt the signal. Terabeam reports successful trials in foggy Seattle. – www.popsci.com.

The “God” Particle: Europe’s CERN laboratory and the Fermi National Accelerator Laboratory near Chicago are racing to find evidence supporting the Higgs boson, a subatomic particle popularly known as the “God” particle. Researchers at CERN thought that they had found it in November 2000, but now it appears that these “may have been simply random movements by other, less interesting particles.” The Higgs boson is a theoretical particle believed to be the source of mass and weight in the uni- verse. The race continues. – www.latimes.com.

A More Accurate Clock: American scientists using sophisticated laser technology and a cooled ion of the liquid metal mercury (a mercury atom with one electron stripped off) have developed the “all-optical atomic clock.” In theory, it could be as much as 100 to 1,000 times more accurate than current cesium-based microwave atomic clocks. Applications are expected in navigation and communications technology, as well in such abstract areas as Einstein’s theory of general relativity and the plasticity of time. – http://news.cnet.com.

Stem Cell Research: A National Institutes of Health report calls for more research on how adult, fetus, and embryo stem cells can help treat juvenile diabetes, Parkinson’s, and other diseases. Stem cells from days-old embryos, most of which are obtained from fertility clinics, seem to show the most potential. They are more plentiful, easier to extract and then grow and multiply in a laboratory, and can develop into a much wider array of tissues. Opponents are trying to block research on the grounds that such cells constitute potential or actual human life. – http://washingtonpost.com.

Driver Information

The most recent applications sought to complement the driver’s ability by targeting such “hands-off, feet-off” driving systems (Fig. 1) as PATH (Partners for Advanced Transit and Highways) and PROMETHEUS (Program for European Traffic with Highest Efficiency and Unprecedented Safety).

For transportation, IT generally can be classified into four groups: Driver Information and Route Guidance, Traffic Flow and Parking Control, Public Transport and Fleet Management, and Automatic Debiting. Only the first item will be discussed in this article.

Driver Information and Route Guidance

Driver Information (DI) and Route Guidance (RG) systems help drivers navigate unfamiliar roads or find the quickest route. The information, especially that given by more advanced systems, consists of advice that drivers can accept or ignore, or a directive with which they are expected to comply. DI and RG can help them reduce or curtail poor route choice as well as excess distance and travel times. The most likely information requested is shortest recommended path, state of the road and weather conditions, unexpected incidents ahead, and the general traffic situation (to estimate travel time).

Disseminating Information

Roadside displays, consisting of fixed road signs and variable message signs, are the simplest DI systems (Fig. 2). The relevant technology is quite basic, as the goal is to give all drivers general information about existing roadway conditions. Variable message signs are used mainly on highways. In urban areas, they are particularly well-suited for providing information about roadway conditions and parking lot availability.

The second method, cellular-radio networks such as the Radio Data System-Traffic Message Channel (RDS-TMC) proposed by the European Broadcasting Union, enable digital information to be superimposed on normal VHF/FM broadcasts. Information can be filtered (drivers call up only what they need and when they need it), updated any time, and broadcast in different languages.

Also, there is no need to lay cables, as is the case with beacon-based RG techniques.

The third (and most sophisticated) method is the electronic RG system, which consists of in-vehicle units, roadside equipment, and control centers (Fig. 3 ). It is usually difficult to start installing the ground infrastructure before ensuring the wide use of onboard systems. Onboard equipment for dynamic navigation comprises a transceiver, a router with a display, a locator with sensors, dead-reckoning devices, and a map memory. The usual indicators of route selection criterion are shorter distance, minimum cost, less traffic, fewer stops, and greater safety. The result of route optimization is the recommendation of how to reach a destination from a given starting point. This can be done by calculating the optimum route for an origin-destination, and by determining the turning directions from the vehicle’s route and position.

Some Examples in Use

CARIN (CAR Information and Navigation System) is an autonomous (static) navigation system used in route planning and guidance. A simplified digital map, stored on a CD, shows the best route. It also offers verbal guidance via a speech synthesizer and gives general tourist information. Other in-vehicle equipment consists of a sensor (magnetic compass) and a navigation computer that carries out the main task. Data collection, in terms of positioning and directing, is implemented by the moving vehicle’s sensors. This information, updated every 3 seconds, is used for map-matching.

The system’s basic advantage is that it does not rely on any external sources, like expensive beacon infrastructures. The route planner algorithm determines the best route for minimizing travel time and distance. However, as CARIN cannot receive current network and traffic situation reports, it is being modernized so that it can receive external information via the car radio with the introduction of RDS-TMC. Moreover, in the future CARIN will offer a fully interactive traffic management opportunity using the European D-net telephone system.

TrafficMaster was one of the first in-vehicle information systems introduced. It was applied first to the M25 London orbital highway, and then to the whole UK highway network. Data is obtained through sensors installed on highway bridges. In case of congestion, messages (such as locations and types of traffic jams and average traffic speed) are generated and transmitted by the control center. The in-vehicle unit displays the current status of the roadway network covered by the sensors. This dissemination is performed minute-by-minute. enabling the driver to make convenient route choices.

In Euro-Scout, the driver enters a destination into a small in-vehicle computer. As the vehicle moves, the in-vehicle navigation equipment determines its position. Whenever it passes a beacon, the user receives the best route, generated by the central computer, for all destinations.

Communication is performed through a two-way infrared link. Beacons located next to the signal heads can use existing cables when they are mounted with traffic lights. Guided vehicles can measure link travel times, which are then returned to the central computer via the beacons in a so-called vehicle telegram. This information is updated continually by the center. The system, therefore, is characterized by its centralized feature: The main data process is carried out in the control office rather than in-vehicle units.

The system has been introduced in Stuttgart by installing 130 beacon heads on traffic lights. A second system of 340 beacons is located in Berlin, and a third one is in Oakland county, Michigan, with 100 beacons and 1,000 equipped vehicles. Start-up costs are high, but in-vehicle equipment costs and the cost of increasing users are low.

In comparison, SOCRATES’ start-up costs are much lower, while the costs of equipping each vehicle and adding additional users are high. This system does have some weak points, though:

The routing algorithm does not take multi-destination users into account, the system is heavily dependent of roadside infrastructure, and a breakdown in the center may cause a system-wide failure.

SOCRATES (System Of Cellular RAdio for Traffic Efficiency and Safety), a two-way communication system, is based on the Global System for Mobile Communications (GSM) cellular radio network. SOCRATES measures the travel times of all guided vehicles from point to point, and uses this information to determine the best routes. In-vehicle units, an odometer, a compass for dead reckoning, and a map pass information to and from roadside units, which are connected to the central computer over telephone lines that allow medium-range communication.

The downlink from the base station to the vehicle is operated in a broadcast mode for disseminating traffic information. The uplink to the base station allows multiple access by floating cars in order to collect travel time patterns. The system’s main disadvantage is the cost of using the mobile phone network. However, a significant benefit is that using the cellular radio requires no additional infrastructure investment because of the introduction of GSM.

The Need for Such Systems

Transport enables socioeconomic relationships to be developed and sustained. This is clear in the continuous dependence on various means of transport to move goods and people. Neglecting transport would bring society to standstill, literally and metaphorically. The introduction of the car put personal transport on the top and increased the need for more roads. The greater the demand for individual mobility, and hence roads, the more complex road transport problems become.

The number of cars per mile of road grows daily. At the same time, lack of space, budgetary priorities, and environmental considerations restrict the extent to which new road construction and increased capacity can be undertaken. But people still want to travel as smoothly as possible.

Therefore, the central idea is that traffic information and communication systems will offer effective solutions-especially where physical changes to the existing infrastructure, such as constructing new links or widening roads, are almost impossible. Closer following distances between intelligent vehicles on automated highways will eventually increase road network capacity.

The Advantages of RG Systems

The main appeal of dynamic RC systems is their ability to recommend paths based on current traffic conditions. Recent research and systems development have focused mainly on dynamic RC systems, which are superior to static systems. Dynamic RC is particularly well-suited for tackling urban congestion, and has advantages over other technological measures, such as vehicle-actuated traffic signals or a system of dynamically updated VMS.

Drivers normally reach their destination by following a route based on previous experience, maps, street signs, and radio traffic bulletins. However, studies show that drivers are unable to select the shortest route, leading to some 6 to 8 percent errors. Preventing this by even static RG could save millions of dollars per year. Driver misperceptions, due to the absence or scanty amount of information about travel time and alternative routes, as well as about specific route incidents, lead to delay and wasted mileage. In Orlando, tourists driving RC-equipped vehicles made 30 percent fewer wrong turns and shortened their travel times by 20 percent, compared to drivers who used paper maps.

Research indicates that applying dynamic RG systems shows great potential for improving travel times, safety, and environmental effects. This is based on the assumption that more drivers will opt to use the services. Other benefits could include satisfaction derived from choosing the best route and being better informed, reduction in the total distance travelled, and incident detection and warning. The real benefit will depend largely on the quality of information provided. With more computing power becoming available and increased technological advancement, more high-quality information is available to drivers.

RG not only guides vehicles through unfamiliar areas, but also increases roadway safety. For example, research indicates that 60 percent of crashes at intersections, and about 30 percent of head-on collisions, could be avoided if drivers had an additional half-second to react. Systems like automatic collision notification (not readily available yet) immediately signal for help if a vehicle’s airbag deploys. In addition, drowsy-driver warning systems keep drivers from falling asleep at the wheel.

The Shape of Things To Come

The discussion so far has focused on the present state of intelligent transport systems. In-vehicle information systems provide information on road conditions and offer advice. They also can provide information about a city’s hotels, catering, theater, cinemas, and even the entire yellow pages. In-vehicle systems can function as hand-held car locators, whether in a busy parking lot or in the remote countryside.

The future of such systems already is taking shape. Dual-purpose and hand-held in-vehicle systems can be used as personal security guards that send a discrete message to a control center when a user is in danger. They could sound an alarm to scare off potential attackers and draw attention to oneself. They also could be built into a car’s security system to prevent theft and send messages in case of an accident.

Hands-free cars are being developed to navigate the road network by the use of a button relying on in-built computers. In addition, car prototypes are being developed that do not require roads-they will fly from origin to destination. All of these require intelligent navigation through a combination of computing and communication. The merging of computing and communication is the bedrock of a revolution to unify all technologies. Journeying intelligently will be at the forefront of this revolution.

Conclusion

Applying these systems, both vehicle- or network-based, depend heavily on the society’s living standards and the country’s economic level of development. Variable message signs and TMCs are the most convenient systems for developing countries, due to their simplicity and cheapness. A typical variable message sign only costs about $200,000, while more sophisticated systems requiring computer centers, roadside equipment like beacons and in-vehicle units, are more expensive. However, in cities with high traffic levels, authorities may consider establishing electronic navigation and information systems with the cooperation of private investors and vehicle manufacturers.

People tomorrow will be more mobile than ever. To provide better transportation systems for the twenty-first century requires the integration of people, vehicles, and network, as well as the improved safety and efficiency of transport systems. Therefore, dynamic DI systems should be able to offer improved mobility for travelers, reduced travel times and operation costs, reduced transportation infrastructure costs, improved highway safety, and reduced transportation energy consumption, transport-generated pollution, and noise.

References

• Barco Visual Systems. Traffic Technology International ‘98 (Feb/ March 1998): 18.
• Benz, D. “PROMETHEUS.” High Tech Report (April 1994).
• Catling, I. “SOCRATES.” Advanced Technology for Road Transport: IVHS and ATT. Ed. I. Catling. Boston: Artech House, 1994, 65-78.
• Georg, L. and F. Steinkohl. “Driver Assistance Concepts and Systems.” Traffic Technology International ‘98 (Oct-Nov. 1997): 66
• Hypower Inc. Traffic Technology International December ‘97 – January ‘98 (1997): 10.
• Intellimotion. Research Updates in Intelligent Transportation Systems. 6(4), (1997): 1.
• Jeffery, D. “Route Guidance and In-Vehicle Information Systems.” Information Technology Applications in Transport. Eds. P. Bonsall and M. C. H. Bell. Utrecht, The Netherlands, 1986, 319-51.
• Kontron Elektronik. Traffic Technology International ‘98 (Annual Review 1998): 232.
• Little, C. “The Intelligent Vehicle Initiative.” Public Roads (Sept.- Oct. 1997): 18-25.
• Siemens. The Power of Integration; Traffic Management; Driver Information. France: Siemens Automotive S.A., 1994.

ATM is currently one of the most attractive technologies in the digital data communications field. In ATM, information is transmitted in short fixed-length blocks that are called cells (Figure 1). An ATM cell consists of a header and a data field that carries the actual information-either video, voice or data. The cell header contains a label denoting the routing address.

Not only was ATM created to overcome the difficulties in existing transfer methods but also to allow the creation of a Broadband Integrated Service Digital Network (B-ISDN).

Transmission speeds up to the physical limits (e.g., 622.05 Mbps signaling rate nowadays) are achievable with ATM. By contrast, there are limitations to the upgrading possible, with the most popular traditional Local Area Network (LAN) topologies (e.g., Ethernet and Token Ring), to higher bandwidth, which means incapacity to support current and of course future real-time applications.

Although the connection-oriented ATM was initially designed for Wide Area Networks (WANs), its unique features including flexibility, scalability, high transfer capacity and support for multimedia applications, also fired the imagination of the LAN vendors in the early 1990s. Since ATM is suitable for both LANs and WANs, historical separation of traditional LANs that are connectionless and WANs that are connection-oriented will eventually disappear. This will form a universal platform for data communications as well as replace the conventional LAN topologies. With full deployment of ATM in design, manufacturing and maintenance of the future networks, the overall costs will be relatively smaller.

The traditional LANs use a shared media-access (e.g. bus) method. That means all stations of the network have to share one transmission medium and have to contend for access. The limitations of shared media-access method are overcome by the ATM’s new approach of switching systems based on central media-access management (Figure 2). Since each user has a dedicated connection to one of the ATM switch ports, users no longer need to contend for access as opposed to the legacy LANs. Moreover ATM LAN users are provided WAN services through another port on the LAN switch. On the other side, the traditional LANs have no direct wide-area capabilities-they must depend on a separate piece of equipment to convert the LAN rates and protocols into WAN-compatible format.

Problems that arise in transmission through the current networks of voice, video and data simultaneously (or in real-time) could well be prevented by using ATM.

With its low-cost networking and technology ATM will soon provide scientist and engineers greater global freedom to exchange data, images (e.g., medical imaging applications) and models in real-time. Beyond the physical boundaries of classrooms, students (especially disabled) will be able to be part of a class and interact with others just as though they were there using high-speed and reliable ATM networks.

GLOSSARY

B-ISDN: A high-speed (above 1.544 Mbps signaling rate) network standard that grew from traditional narrowband ISDN.

Connection-oriented: A network (e.g., WANs) that establishes, either permanently or on a call-by-call basis, a specific circuit path for transmission.

Connectionless: A network (e.g., legacy LANs) in which no particular path is established for the transfer of information.

Ethernet: A LAN using 10 Mbps signaling rate.

LAN: High-speed network connecting personal computers, printers, and other data equipment within an office or campus.

Mbps: Mega bit per second

Token Ring: A LAN using 4 or 16 Mbps signaling rate.

WAN: High-speed network connecting communications equipment nationally and internationally.

References

• PARULKAR G. M.: ‘Local ATM Networks’, IEEE Network March 1993, p.S-9.
• VENIERIS I. S., ANGELOPOULOS J. D. & STASSINOPOULOS G. I.:
• ‘Efficient Use of Protocol Stacks for LAN/MAN-ATM Interworking’, IEEE Journal on Selected Areas in Communications October 1993, 11(8) p.1160-1170,.
• KIM B.G. & WANG P.: ‘ATM Network: Goals and Challenges’, Communications of the ACM February 199538 (2), pp. 39-44.
• The ATM Forum: http:/ /www.atmforum.com/