title: Portulaca oleracea

text: "P. oleracea" is one of very few plants able to utilize both CAM and C4 photosynthesis pathways, for a long time believed to be incompatible with each other despite biochemical similarities. "P. oleracea" will switch from C4 to CAM pathways during times of drought and there is transcription regulation and physiological evidence for C4-CAM hybrid photosynthesis during mild drought.


title: Portulaca oleracea

text: "P. oleracea" was recorded in 1753 by Carl Linnaeus in "Species Plantarum". Due to the great variability, a large number of subspecies and varieties have been described as species of their own, but according to other publications, they all fall within the range of variation of "P. oleracea". The synonyms "P. oleracea" subsp. "sativa", "P. sativa", and "P. oleracea" var. "sativa", which are more common in the literature, refer to a somewhat more robust form in cultivation with larger seeds that cannot be separated from the species. Approximately 40 cultivars of "P. oleracea" are currently grown.


title: Portulaca oleracea

text: The flowering plant more commonly known as winter purslane ("Claytonia perfoliata") is a member of the Montiaceae family and is not closely related.


title: Portulaca oleracea

text: Purslane has an extensive distribution, assumed to be mostly anthropogenic (or hemerochoric), extending from North Africa and Southern Europe through the Middle East and the Indian subcontinent to Malesia and Australasia. The species status in the Americas is uncertain. In general, it is often considered an exotic weed, but there is evidence that the species was in Crawford Lake deposits (Ontario) in 1350–1539, suggesting that it reached North America in the pre-Columbian era. Scientists suggested that the plant was already eaten by Native Americans, who spread its seeds. How it reached the Americas is currently unknown.


title: Portulaca oleracea

text: Compared to other common crops, "P. oleracea" is more tolerant of pests due to its waxy cover which protects the plant from insects and diseases. In some instances "P. oleracea" is even known to have antifungal properties. However some phytotoxic metabolites of "Drechslera indica", a fungus, can cause necrosis on purslane. "Dichotomophthora portulacae", another fungus, can cause stem rot.


title: Portulaca oleracea

text: "Schizocerella pilicornis" and "Hypurus bertrandi" are known to feed on "Portulaca oleracea". In some instances they may help control the competitiveness of "P. oleracea" to prevent weed infestation in fields where "P. oleracea" is not wanted, however they do not stop it from growing completely.


title: Portulaca oleracea

text: Raw purslane is 93% water, 3% carbohydrates, 2% protein, and contains negligible fat (table). In a 100 gram reference amount, purslane supplies 20 calories, and rich amounts (20% or more of the Daily Value, DV) of vitamin E (81% DV) and vitamin C (25% DV), with moderate content (11–19% DV) of several dietary minerals (table). Purslane is a rich source of alpha-linolenic acid, an essential omega-3 fatty acid.


title: Portulaca oleracea

text: The plant may be eaten as a leaf vegetable. William Cobbett noted that it was "eaten by Frenchmen and pigs when they can get nothing else. Both use it in salad, that is to say, raw". It has a slightly sour and salty taste and is eaten throughout much of Europe, North Africa, the Middle East, Asia, and Mexico. The stems, leaves and flower buds are all edible raw or cooked. Purslane may be used fresh as a salad, stir-fried, or cooked as spinach is, and because of its mucilaginous quality it also is suitable for soups and stews. The sour taste is due to oxalic and malic acid, the latter of which is produced through the crassulacean acid metabolism (CAM) pathway that is seen in many xerophytes (plants living in dry conditions), and is at its highest when the plant is harvested in the early morning.


title: Portulaca oleracea

text: Aboriginal Australians use the seeds of purslane to make seedcakes. Greeks, who call it () or (), use the leaves and the stems with feta cheese, tomato, onion, garlic, oregano, and olive oil. They add it in salads, boil it, or add it to casseroled chicken. In Turkey, besides being used in salads and in baked pastries, it is cooked as a vegetable similar to spinach, or is mixed with yogurt to form a tzatziki variant. In Egypt, it is also cooked like spinach as a vegetable dish, but not in salads.


title: Portulaca oleracea

text: In Kurdistan, people commonly make a kind of soup from it called palpina soup (شۆربای پەڵپینە). In the Alentejo region of Portugal, purslane is used to cook a traditional soup (sopa de beldroegas) which is topped with soaked bread, poached eggs and/or goats' cheese. In Mexico and the American Southwest, the plant is consumed as "verdolagas."


title: Portulaca oleracea

text: Soil salination on agricultural soils can cause a decrease in crop yields, and it is no longer possible to grow salt-sensitive species on that soil. Purslane has a high tolerance for salt toxicity, which makes it suitable for cropping in areas where irrigation is necessarily carried out with water having a high chloride-based salinity.


title: Portulaca oleracea

text: Purslane can remove salt from the cultivation medium under saline conditions. As an intercrop or during one growing season, it can remove 210 kg/ha of chloride and 65 kg/ha of sodium when cultivated at 6.5 dS *m, allowing growth of salt-sensitive plants on saline soils. Purslane has a positive effect on companion plants in salty conditions, such as tomatoes.


title: Portulaca oleracea

text: Archaeobotanical finds are common at many Mediterranean prehistoric sites. In historic contexts, seeds have been retrieved from a protogeometric layer in Kastanas, as well as from the Samian Heraion dating to the 7th century BC. In the 4th century BC, Theophrastus names purslane, (), as one of the several summer pot herbs that must be sown in April ("Enquiry into Plants" 7.1.2). As "Portulaca" it figures in the long list of comestibles enjoyed by the Milanese given by Bonvesin de la Riva in his "Marvels of Milan" (1288).


title: Portulaca oleracea

text: In antiquity, its healing properties were thought so reliable that Pliny the Elder advised wearing the plant as an amulet to expel all evil ("Natural History" 20.210).


title: Portulaca oleracea

text: "Verdolaga", the Spanish word for purslane, is a nickname for South American football clubs with green-white schemes in their uniforms, including Colombia's Atletico Nacional and Argentina's Ferrocarril Oeste. Afro-Colombian singer Totó la Momposina sings a song entitled “La Verdolaga”.


title: Smoking

text: Smoking is a practice in which a substance is burned and the resulting smoke is typically breathed in to be tasted and absorbed into the bloodstream. Most commonly, the substance used is the dried leaves of the tobacco plant, which have been rolled into a small rectangle of rolling paper to create a small, round cylinder called a cigarette. Smoking is primarily practised as a route of administration for recreational drug use because the combustion of the dried plant leaves vaporizes and delivers active substances into the lungs where they are rapidly absorbed into the bloodstream and reach bodily tissue. In the case of cigarette smoking, these substances are contained in a mixture of aerosol particles and gases and include the pharmacologically active alkaloid nicotine; the vaporization creates heated aerosol and gas into a form that allows inhalation and deep penetration into the lungs where absorption into the bloodstream of the active substances occurs. In some cultures, smoking is also carried out as a part of various rituals, where participants use it to help induce trance-like states that, they believe, can lead them to spiritual enlightenment.


title: Smoking

text: Smoking is one of the most common forms of recreational drug use. Tobacco smoking is the most popular form, being practised by over one billion people globally, of whom the majority are in the developing countries. Less common drugs for smoking include cannabis and opium. Some of the substances are classified as hard narcotics, like heroin, but the use of these is very limited as they are usually not commercially available. Cigarettes are primarily industrially manufactured but also can be hand-rolled from loose tobacco and rolling paper. Other smoking implements include pipes, cigars, bidis, hookahs, and bongs.


title: Smoking

text: Smoking has negative health effects, because smoke inhalation inherently poses challenges to various physiologic processes such as respiration. Smoking tobacco is among the leading causes of many diseases such as lung cancer, heart attack, COPD, erectile dysfunction, and birth defects. Diseases related to tobacco smoking have been shown to kill approximately half of long-term smokers when compared to average mortality rates faced by non-smokers. Smoking caused over five million deaths a year from 1990 to 2015. Non-smokers account for 2% of all deaths globally due to second-hand smoke. The health hazards of smoking have caused many countries to institute high taxes on tobacco products, publish advertisements to discourage use, limit advertisements that promote use, and provide help with quitting for those who do smoke.


title: Smoking

text: Smoking can be dated to as early as 5000 BCE, and has been recorded in many different cultures across the world. Early smoking evolved in association with religious ceremonies; as offerings to deities; in cleansing rituals; or to allow shamans and priests to alter their minds for purposes of divination or spiritual enlightenment. After the European exploration and conquest of the Americas, the practice of smoking tobacco quickly spread to the rest of the world. In regions like India and Sub-Saharan Africa, it merged with existing practices of smoking (mostly of cannabis). In Europe, it introduced a new type of social activity and a form of drug intake which previously had been unknown.


title: Smoking

text: Perception surrounding smoking has varied over time and from one place to another: holy and sinful, sophisticated and vulgar, a panacea and deadly health hazard. In the last decade of the 20th century, smoking came to be viewed in a decidedly negative light, especially in Western countries.


title: Smoking

text: The history of smoking dates back to as early as 5000 BCE for shamanistic rituals. Many ancient civilizations, such as the Babylonians, Indians and Chinese, burnt incense as a part of religious rituals, as did the Israelites and the later Catholic and Orthodox Christian churches. Smoking in the Americas probably had its origins in the incense-burning ceremonies of shamans but was later adopted for pleasure, or as a social tool. The smoking of tobacco, as well as various hallucinogenic drugs, was used to achieve trances and to come into contact with the spirit world.


title: Smoking

text: Substances such as cannabis, clarified butter (ghee), fish offal, dried snake skins and various pastes molded around incense sticks dates back at least 2000 years. Fumigation ("dhupa") and fire offerings ("homa") are prescribed in the Ayurveda for medical purposes, and have been practiced for at least 3,000 years while smoking, "dhumrapana" (literally "drinking smoke"), has been practiced for at least 2,000 years. Before modern times these substances have been consumed through pipes, with stems of various lengths or chillums. Archaeological findings also show the existence of pipes to smoke opium in Cyprus and Crete as soon as the Bronze Age.


title: Smoking

text: Cannabis smoking was common in the Middle East before the arrival of tobacco, and was early on a common social activity that centered around the type of water pipe called a hookah. Smoking, especially after the introduction of tobacco, was an essential component of Muslim society and culture and became integrated with important traditions such as weddings, funerals and was expressed in architecture, clothing, literature and poetry.


title: Smoking

text: Cannabis smoking was introduced to Sub-Saharan Africa through Ethiopia and the east African coast by either Indian or Arab traders in the 13th century or earlier and spread on the same trade routes as those that carried coffee, which originated in the highlands of Ethiopia. It was smoked in calabash water pipes with terracotta smoking bowls, apparently an Ethiopian invention which was later conveyed to eastern, southern and central Africa.


title: Smoking

text: Reports from the first European explorers and conquistadors to reach the Americas tell of rituals where native priests smoked themselves into such high degrees of intoxication that it is unlikely that the rituals were limited to just tobacco.


title: Smoking

text: In 1612, six years after the settlement of Jamestown, John Rolfe was credited as the first settler to successfully grow tobacco as a cash crop. The demand quickly grew as tobacco, referred to as "golden weed", revived the Virginia Company from its failed expeditions in search for gold in the Americas. In order to meet demands from the old world, tobacco was grown in succession, quickly depleting the land. This became a motivator to settle west into the unknown continent, and likewise an expansion of tobacco production. Indentured servants became the primary labor force up until Bacon's Rebellion, from which the focus turned to slavery. This trend abated following the American Revolution as slavery became regarded as unprofitable. However the practice was revived in 1794 with the invention of the cotton gin.


title: Smoking

text: A Frenchman named Jean Nicot (from whose name the word nicotine is derived) introduced tobacco to France in 1560. From France tobacco spread to England. The first report documents an English sailor in Bristol in 1556, seen "emitting smoke from his nostrils". Like tea, coffee and opium, tobacco was just one of many intoxicants that was originally used as a form of medicine. Tobacco was introduced around 1600 by French merchants in what today is modern-day The Gambia and Senegal. At the same time caravans from Morocco brought tobacco to the areas around Timbuktu and the Portuguese brought the commodity (and the plant) to southern Africa, establishing the popularity of tobacco throughout all of Africa by the 1650s.


title: Smoking

text: Soon after its introduction to the Old World, tobacco came under frequent criticism from state and religious leaders. Murad IV, sultan of the Ottoman Empire 1623–40 was among the first to attempt a smoking ban by claiming it was a threat to public morality and health. The Chongzhen Emperor of China issued an edict banning smoking two years before his death and the overthrow of the Ming dynasty. Later, the Manchu rulers of the Qing dynasty, would proclaim smoking "a more heinous crime than that even of neglecting archery". In Edo period Japan, some of the earliest tobacco plantations were scorned by the "shōgun" as being a threat to the military economy by letting valuable farmland go to waste for the use of a recreational drug instead of being used to plant food crops.


title: Smoking

text: Religious leaders have often been prominent among those who considered smoking immoral or outright blasphemous. In 1634, the Patriarch of Moscow and all Rus' forbade the sale of tobacco and sentenced men and women who flouted the ban to have their nostrils slit and their backs whipped until skin came off their backs. The Western church leader Pope Urban VII likewise condemned smoking in a papal bull of 1590. Despite many concerted efforts, restrictions and bans were almost universally ignored. When James VI and I, a staunch anti-smoker and the author of "A Counterblaste to Tobacco", tried to curb the new trend by enforcing a whopping 4000% tax increase on tobacco in 1604, it proved a failure, as London had some 7,000 tobacco sellers by the early 17th century. Later, scrupulous rulers would realise the futility of smoking bans and instead turned tobacco trade and cultivation into lucrative government monopolies.


title: Smoking

text: By the mid-17th century every major civilization had been introduced to tobacco smoking and in many cases had already assimilated it into its culture, despite the attempts of many rulers to stamp the practice out with harsh penalties or fines. Tobacco, both product, and plant followed the major trade routes to major ports and markets, and then on into the hinterlands. The English language term "smoking" was coined in the late 18th century; before then the practice was referred to as "drinking smoke".


title: Smoking

text: Tobacco and cannabis were used in Sub-Saharan Africa, much like elsewhere in the world, to confirm social relations, but also created entirely new ones. In what is today Congo, a society called Bena Diemba ("People of Cannabis") was organized in the late 19th century in Lubuko ("The Land of Friendship"). The Bena Diemba were collectivist pacifists that rejected alcohol and herbal medicines in favor of cannabis.


title: Smoking

text: The growth remained stable until the American Civil War in the 1860s, from which the primary labor force transition from slavery to sharecropping. This compounded with a change in demand, lead to the industrialization of tobacco production with the cigarette. James Albert Bonsack, a craftsman, in 1881 produced a machine to speed the production of cigarettes.


title: Smoking

text: In the 19th century, the practise of smoking opium became widespread in China. Previously, opium had only been ingested via consumption, and then only for its medicinal properties (opium was an anaesthetic). The narcotic was also outlawed in China sometime in the early 18th century due the societal issues it caused. Due to a massive trade imbalance, however, foreign merchants started to smuggle opium into China via Canton, to the chagrin of the Chinese authorities. Attempts by Chinese official Lin Zexu to eliminate the trade led to the outbreak of the First Opium War. The Chinese defeat in the First and Second Opium Wars resulted in the legalization of the importation of opium into China.


title: Smoking

text: Opium smoking later spread with Chinese immigrants and spawned many infamous opium dens in Chinatowns around South and Southeast Asia, Europe and the Americas. In the latter half of the 19th century, opium smoking became popular in the artistic community in Europe, especially Paris; artists' neighborhoods such as Montparnasse and Montmartre became virtual "opium capitals". While opium dens that catered primarily to emigrant Chinese continued to exist in Chinatowns around the world, the trend among the European artists largely abated after the outbreak of World War I. The consumption of Opium abated in China during the Cultural Revolution in the 1960s and 1970s.


title: Smoking

text: Many people have been critical about tobacco use since it gained popularity. In 1798, Dr. Benjamin Rush (early American physician, signer of the Declaration of Independence, Surgeon General under George Washington, and anti-tobacco activist) was "against the habitual use of tobacco" because he believed it (a) "led to a desire for strong drink," (b) "was injurious both to health and morals," (c) "is generally offensive to" nonsmokers, (d) "produces a want of respect for" nonsmokers, and (e) "always disposes to unkind and unjust behavior towards them."


title: Smoking

text: With the modernization of cigarette production compounded with the increased life expectancies during the 1920s, adverse health effects began to become more prevalent. In Germany, anti-smoking groups, often associated with anti-liquor groups, first published advocacy against the consumption of tobacco in the journal "Der Tabakgegner" (The Tobacco Opponent) in 1912 and 1932. In 1929, Fritz Lickint of Dresden, Germany, published a paper containing formal statistical evidence of a lung cancer–tobacco link. During the Great Depression, Adolf Hitler condemned his earlier smoking habit as a waste of money, and later with stronger assertions. This movement was further strengthened with Nazi reproductive policy as women who smoked were viewed as unsuitable to be wives and mothers in a German family.


title: Smoking

text: The movement in Nazi Germany did reach across enemy lines during the Second World War, as anti-smoking groups quickly lost popular support. By the end of the Second World War, American cigarette manufacturers quickly reentered the German black market. Illegal smuggling of tobacco became prevalent, and leaders of the Nazi anti-smoking campaign were assassinated. As part of the Marshall Plan, the United States shipped free tobacco to Germany; with 24,000 tons in 1948 and 69,000 tons in 1949. Per capita yearly cigarette consumption in post-war Germany steadily rose from 460 in 1950 to 1,523 in 1963. By the end of the 20th century, anti-smoking campaigns in Germany were unable to exceed the effectiveness of the Nazi-era climax in the years 1939–41 and German tobacco health research was described by Robert N. Proctor as "muted".


title: Smoking

text: In the UK and the US, an increase in lung cancer rates, formerly "among the rarest forms of disease", was noted by the 1930s, but its cause remained unknown and even the credibility of this increase was sometimes disputed as late as 1950. For example, in Connecticut, reported age-adjusted incidence rates of lung cancer among males increased 220% between 1935–39 and 1950–54. In the UK, the share of lung cancer among all cancer deaths in men increased from 1.5% in 1920 to 19.7% in 1947. Nevertheless, these increases were questioned as potentially caused by increased reporting and improved methods of diagnosis. Although several carcinogens were already known at the time (for example, benzo[a]pyrene was isolated from coal tar and demonstrated to be a potent carcinogen in 1933), none were known to be contained in adequate quantities in tobacco smoke. Richard Doll in 1950 published research in the British Medical Journal showing a close link between smoking and lung cancer. Four years later, in 1954 the British Doctors Study, a study of some 40 thousand doctors over 20 years, confirmed the link, based on which the government issued advice that smoking and lung cancer rates were related. In 1964 the United States Surgeon General's Report on Smoking and Health demonstrated the relationship between smoking and cancer. Further reports confirmed this link in the 1980s and concluded in 1986 that passive smoking was also harmful.


title: Smoking

text: As scientific evidence mounted in the 1980s, tobacco companies claimed contributory negligence as the adverse health effects were previously unknown or lacked substantial credibility. Health authorities sided with these claims up until 1998, from which they reversed their position. The Tobacco Master Settlement Agreement, originally between the four largest US tobacco companies and the Attorneys General of 46 states, restricted certain types of tobacco advertisement and required payments for health compensation; which later amounted to the largest civil settlement in United States history.


title: Smoking

text: From 1965 to 2006, rates of smoking in the United States have declined from 42% to 20.8%. A significant majority of those who quit were professional, affluent men. Despite this decrease in the prevalence of consumption, the average number of cigarettes consumed per person per day increased from 22 in 1954 to 30 in 1978. This paradoxical event suggests that those who quit smoked less, while those who continued to smoke moved to smoke more light cigarettes. This trend has been paralleled by many industrialized nations as rates have either leveled-off or declined. In the developing countries, however, tobacco consumption continues to rise at 3.4% in 2002. In Africa, smoking is in most areas considered to be modern, and many of the strong adverse opinions that prevail in the West receive much less attention. Today Russia leads as the top consumer of tobacco followed by Indonesia, Laos, Ukraine, Belarus, Greece, Jordan, and China.


title: Smoking

text: At the global scale, initial ideas of an international convention towards the prevention of tobacco had been initiated in the World Health Assembly (WHA) in 1996. In 1998, along with the successful election of Dr. Gro Harlem Brundtland as the Director-General, the World Health Organization set tobacco control as its leading health concern and has begun a program known as the Tobacco Free Initiative (TFI) in order to reduce rates of consumption in the developing world. However, it was not until 2003 that the Framework Convention on Tobacco Control (FCTC) was accepted in WHA and entered into force in 2005. FCTC marked a milestone as the first international treaty concerning a global health issue that aims to combat tobacco in multiple aspects including tobacco taxes, advertisement, trading, environmental affects, health influences, etc. The birth of this evidence-based and systematic approach has resulted in the reinforcement of tobacco taxes and the implementation of smoke-free laws in 128 countries that led to the decrease of smoking prevalence in developing nations.


title: Smoking

text: In the early 1980s, organized international trafficking of cocaine grew. However, overproduction and tighter legal enforcement for the illegal product caused drug dealers to convert the powder to "crack" – a solid, smokable form of cocaine that could be sold in smaller quantities to more people. This trend abated in the 1990s as increased police action coupled with a robust economy caused many potential consumers to give up or fail to take up the habit.


title: Smoking

text: Recent years shows an increase in the consumption of vaporized heroin, methamphetamine and Phencyclidine (PCP). Along with a smaller number of psychedelic drugs such as Changa, DMT, 5-Meo-DMT, and Salvia divinorum.


title: Smoking

text: The most popular type of substance that is smoked is tobacco. There are many different tobacco cultivars which are made into a wide variety of mixtures and brands. Tobacco is often sold flavored, often with various fruit aromas, something which is especially popular for use with water pipes, such as hookahs. The second most common substance that is smoked is cannabis, made from the flowers or leaves of "Cannabis sativa" or "Cannabis indica". The substance is considered illegal in most countries in the world and in the countries that tolerate public consumption, it is sometimes only pseudo-legal. Despite this, a considerable percentage of the adult population in many countries have tried it with smaller minorities doing it on a regular basis. Since cannabis is illegal or only tolerated in many jurisdictions, there is no industrial mass-production of cigarettes, meaning that the most common form of smoking is with hand-rolled cigarettes (often called joints) or with pipes. Water pipes are also fairly common; water pipes used for cannabis include designs known as bongs and bubblers, among others.


title: Smoking

text: A few other recreational drugs are smoked by smaller minorities. Most of these substances are controlled, and some are considerably more intoxicating than either tobacco or cannabis. These include crack cocaine, heroin, methamphetamine and PCP. A small number of psychedelic drugs are also smoked, including DMT, 5-Meo-DMT, and Salvia divinorum.


title: Smoking

text: Even the most primitive form of smoking requires tools of some sort to perform. This has resulted in a staggering variety of smoking tools and paraphernalia from all over the world. Whether tobacco, cannabis, opium or herbs, some form of receptacle is required along with a source of fire to light the mixture. The most common today is by far the cigarette, consisting of a mild inhalant strain of tobacco in a tightly rolled tube of paper, usually manufactured industrially and including a filter, or hand-rolled with loose tobacco. Other popular smoking tools are various pipes and cigars.


title: Smoking

text: A less common but increasingly popular alternative to smoking is vaporizers, which use hot air convection to deliver the substance without combustion, which may reduce health risks. A portable vaporization alternative appeared in 2003 with the introduction of electronic cigarettes, battery-operated, cigarette-shaped devices which produce an aerosol intended to mimic the smoke from burning tobacco, delivering nicotine to the user without some of the harmful substances released in tobacco smoke.


title: Smoking

text: Other than actual smoking equipment, many other items are associated with smoking; cigarette cases, cigar boxes, lighters, matchboxes, cigarette holders, cigar holders, ashtrays, silent butlers, pipe cleaners, tobacco cutters, match stands, pipe tampers, cigarette companions and so on. Some examples of these have become valuable collector items and particularly ornate and antique items can fetch high prices.


title: Smoking

text: Smoking is one of the leading preventable causes of deaths globally and is the cause of 15% of all deaths, 2% of which are non-smokers who die due to second-hand smoke. In the United States, about 500,000 deaths per year are attributed to smoking-related diseases and a recent study estimated that as much as 1/3 of China's male population will have significantly shortened life-spans due to smoking. Male and female smokers lose an average of 13.2 and 14.5 years of life, respectively. At least half of all lifelong smokers die earlier as a result of smoking. The risk of dying from lung cancer before age 85 is 22.1% for a male smoker and 11.9% for a female current smoker, in the absence of competing causes of death. The corresponding estimates for lifelong nonsmokers are a 1.1% probability of dying from lung cancer before age 85 for a man of European descent, and a 0.8% probability for a woman. Smoking just one cigarette a day results in a risk of coronary heart disease that is halfway between that of a heavy smoker and a non-smoker. The non-linear dose–response relationship may be explained by smoking's effect on platelet aggregation.


title: Smoking

text: Among the diseases that can be caused by smoking are vascular stenosis, lung cancer, heart attacks and chronic obstructive pulmonary disease (COPD). Smoking during pregnancy may cause ADHD to a fetus.


title: Smoking

text: Smoking is a risk factor strongly associated with periodontitis and tooth loss. The effects of smoking on periodontal tissues depend on the number of cigarettes smoked daily and the duration of the habit. A study showed that smokers had 2.7 times and former smokers 2.3 times greater probabilities to have established periodontal disease than non‐smokers, independent of age, sex and plaque index, however, the effect of tobacco on periodontal tissues seems to be more pronounced in men than in women. Studies have found that smokers had greater odds for more severe dental bone loss compared to non‐smokers , also, people who smoke and drink alcohol heavily have much higher risk of developing oral cancer (mouth and lip) compared with people who do neither. Smoking can also cause milanosis in the mouth.


title: Smoking

text: Smoking has been also associated with oral conditions including dental caries, dental implant failures, premalignant lesions, and cancer. Smoking can affect the immune-inflammatory processes which may increase the susceptibility to infections; it can alter the oral mycobiota and facilitate colonization of the oral cavity with fungi and pathogenic molds.


title: Smoking

text: Many governments are trying to deter people from smoking with anti-smoking campaigns in mass media stressing the harmful long-term effects of smoking. Passive smoking, or secondhand smoking, which affects people in the immediate vicinity of smokers, is a major reason for the enforcement of smoking bans. These are laws enforced to stop individuals from smoking in indoor public places, such as bars, pubs and restaurants, thus reducing nonsmokers' exposure to secondhand smoke. A common concern among legislators is to discourage smoking among minors and many states have passed laws against selling tobacco products to underage customers (establishing a smoking age). Many developing countries have not adopted anti-smoking policies, leading some to call for anti-smoking campaigns and further education to explain the negative effects of ETS (Environmental Tobacco Smoke) in developing countries. Tobacco advertising is also sometimes regulated to make smoking less appealing.


title: Smoking

text: Despite the many bans, European countries still hold 18 of the top 20 spots, and according to the ERC, a market research company, the heaviest smokers are from Greece, averaging 3,000 cigarettes per person in 2007. Rates of smoking have leveled off or declined in the developed world but continue to rise in developing countries. Smoking rates in the United States have dropped by half from 1965 to 2006, falling from 42% to 20.8% in adults.


title: Smoking

text: The effects of addiction on society vary considerably between different substances that can be smoked and the indirect social problems that they cause, in great part because of the differences in legislation and the enforcement of narcotics legislation around the world. Though nicotine is a highly addictive drug, its effects on cognition are not as intense or noticeable as other drugs such as cocaine, amphetamines or any of the opiates (including heroin and morphine).


title: Smoking

text: Smoking is a risk factor in Alzheimer's disease. While smoking more than 15 cigarettes per day has been shown to worsen the symptoms of Crohn's disease, smoking has been shown to actually lower the prevalence of ulcerative colitis.


title: Smoking

text: Smokers are 30-40% more likely to develop type 2 diabetes than non-smokers, and the risk increases with the number of cigarettes smoked.


title: Smoking

text: Inhaling the vaporized gas form of substances into the lungs is a quick and very effective way of delivering drugs into the bloodstream (as the gas diffuses directly into the pulmonary vein, then into the heart and from there to the brain) and affects the user within less than a second of the first inhalation. The lungs consist of several million tiny bulbs called alveoli that altogether have an area of over 70 m (about the area of a tennis court). This can be used to administer useful medical as well as recreational drugs such as aerosols, consisting of tiny droplets of a medication, or as gas produced by burning plant material with a psychoactive substance or pure forms of the substance itself. Not all drugs can be smoked, for example the sulphate derivative that is most commonly inhaled through the nose, though purer free base forms of substances can, but often require considerable skill in administering the drug properly. The method is also somewhat inefficient since not all of the smoke will be inhaled. The inhaled substances trigger chemical reactions in nerve endings in the brain due to being similar to naturally occurring substances such as endorphins and dopamine, which are associated with sensations of pleasure. The result is what is usually referred to as a "high" that ranges between the mild stimulus caused by nicotine to the intense euphoria caused by heroin, cocaine and methamphetamines.


title: Smoking

text: Inhaling smoke into the lungs, no matter the substance, has adverse effects on one's health. The incomplete combustion produced by burning plant material, like tobacco or cannabis, produces carbon monoxide, which impairs the ability of blood to carry oxygen when inhaled into the lungs. There are several other toxic compounds in tobacco that constitute serious health hazards to long-term smokers from a whole range of causes; vascular abnormalities such as stenosis, lung cancer, heart attacks, strokes, impotence, low birth weight of infants born by smoking mothers. 8% of long-term smokers develop the characteristic set of facial changes known to doctors as smoker's face.


title: Smoking

text: Tobacco smoke is a complex mixture of over 5,000 identified chemicals, of which 98 are known to have specific toxicological properties. The most important chemicals causing cancer are those that produce DNA damage since such damage appears to be the primary underlying cause of cancer. Cunningham et al. combined the microgram weight of the compound in the smoke of one cigarette with the known genotoxic effect per microgram to identify the most carcinogenic compounds in cigarette smoke. The seven most important carcinogens in tobacco smoke are shown in the table, along with DNA alterations they cause.


title: Smoking

text: Most tobacco smokers begin during adolescence or early adulthood. Smoking has elements of risk-taking and rebellion, which often appeal to young people. The presence of high-status models and peers may also encourage smoking. Because teenagers are influenced more by their peers than by adults, attempts by parents, schools, and health professionals at preventing people from trying cigarettes are not always successful.


title: Smoking

text: Smokers often report that cigarettes help relieve feelings of stress. However, the stress levels of adult smokers are slightly higher than those of nonsmokers. Adolescent smokers report increasing levels of stress as they develop regular patterns of smoking, and smoking cessation leads to reduced stress. Far from acting as an aid for mood control, nicotine dependency seems to exacerbate stress. This is confirmed in the daily mood patterns described by smokers, with normal moods during smoking and worsening moods between cigarettes. Thus, the apparent relaxant effect of smoking only reflects the reversal of the tension and irritability that develop during nicotine depletion. Dependent smokers need nicotine to remain feeling normal.


title: Smoking

text: In the mid-20th century psychologists such as Hans Eysenck developed a personality profile for the typical smoker of that period; extraversion was associated with smoking, and smokers tended to be sociable, impulsive, risk taking, and excitement-seeking individuals. Although personality and social factors may make people likely to smoke, the actual habit is a function of operant conditioning. During the early stages, smoking provides pleasurable sensations (because of its action on the dopamine system) and thus serves as a source of positive reinforcement. After an individual has smoked for many years, the avoidance of withdrawal symptoms and negative reinforcement become the key motivations. Like all addictive substances, the amount of exposure required to become dependent on nicotine can vary from person to person.


title: Smoking

text: In terms of the Big Five personality traits, research has found smoking to be correlated with lower levels of agreeableness and conscientiousness, as well as higher levels of extraversion and neuroticism.


title: Smoking

text: Education and counselling by physicians of children and adolescents has been found to be effective in decreasing the risk of tobacco use. Systematic reviews show that psychosocial interventions can help women stop smoking in late pregnancy, reducing low birthweight and preterm births. A 2016 Cochrane review showed that the combination of medication and behavioural support was more effective than minimal interventions or usual care. Another Cochrane review "suggests that neither reducing smoking to quit nor quitting abruptly results in superior quit rates; people could therefore be given a choice of how to quit, and support provided to people who would specifically like to reduce their smoking before quitting."


title: Smoking

text: Smoking, primarily of tobacco, is an activity that is practiced by some 1.1 billion people, and up to 1/3 of the adult population. The image of the smoker can vary considerably, but is very often associated, especially in fiction, with individuality and aloofness. Even so, smoking of both tobacco and cannabis can be a social activity which serves as a reinforcement of social structures and is part of the cultural rituals of many and diverse social and ethnic groups. Many smokers begin smoking in social settings and the offering and sharing of a cigarette is often an important rite of initiation or simply a good excuse to start a conversation with strangers in many settings; in bars, night clubs, at work or on the street. Lighting a cigarette is often seen as an effective way of avoiding the appearance of idleness or mere loitering. For adolescents, it can function as a first step out of childhood or as an act of rebellion against the adult world. Also, smoking can be seen as a sort of camaraderie. It has been shown that even opening a packet of cigarettes, or offering a cigarette to other people, can increase the level of dopamine (the "happy feeling") in the brain, and it is doubtless that people who smoke form relationships with fellow smokers, in a way that only proliferates the habit, particularly in countries where smoking inside public places has been made illegal. Other than recreational drug use, it can be used to construct identity and a development of self-image by associating it with personal experiences connected with smoking. The rise of the modern anti-smoking movement in the late 19th century did more than create awareness of the hazards of smoking; it provoked reactions of smokers against what was, and often still is, perceived as an assault on personal freedom and has created an identity among smokers as rebels or outcasts, apart from non-smokers:


title: Smoking

text: The importance of tobacco to soldiers was early on recognized as something that could not be ignored by commanders. By the 17th century allowances of tobacco were a standard part of the naval rations of many nations and by World War I cigarette manufacturers and governments collaborated in securing tobacco and cigarette allowances to soldiers in the field. It was asserted that regular use of tobacco while under duress would not only calm the soldiers but allow them to withstand greater hardship. Until the mid-20th century, the majority of the adult population in many Western nations were smokers and the claims of anti-smoking activists were met with much skepticism, if not outright contempt. Today the movement has considerably more weight and evidence of its claims, but a considerable proportion of the population remains steadfast smokers.


title: Smoking

text: Smoking has been accepted into culture, in various art forms, and has developed many distinct, and often conflicting or mutually exclusive, meanings depending on time, place and the practitioners of smoking. Pipe smoking, until recently one of the most common forms of smoking, is today often associated with solemn contemplation, old age and is often considered quaint and archaic. Cigarette smoking, which did not begin to become widespread until the late 19th century, has more associations of modernity and the faster pace of the industrialized world. Cigars have been, and still are, associated with masculinity, power and is an iconic image associated with the stereotypical capitalist. In fact, some evidence suggests that men with higher than average testosterone levels are more likely to smoke. Smoking in public has for a long time been something reserved for men and when done by women has been associated with promiscuity. In Japan during the Edo period, prostitutes and their clients would often approach one another under the guise of offering a smoke; the same was true for 19th-century Europe.


title: Smoking

text: The earliest depictions of smoking can be found on Classical Mayan pottery from around the 9th century. The art was primarily religious in nature and depicted deities or rulers smoking early forms of cigarettes. Soon after smoking was introduced outside of the Americas it began appearing in painting in Europe and Asia. The painters of the Dutch Golden Age were among the first to paint portraits of people smoking and still lifes of pipes and tobacco. For southern European painters of the 17th century, a pipe was much too modern to include in the preferred motifs inspired by mythology from Greek and Roman antiquity. At first smoking was considered lowly and was associated with peasants. Many early paintings were of scenes set in taverns or brothels. Later, as the Dutch Republic rose to considerable power and wealth, smoking became more common amongst the affluent and portraits of elegant gentlemen tastefully raising a pipe appeared. Smoking represented pleasure, transience and the briefness of earthly life as it, quite literally, went up in smoke. Smoking was also associated with representations of both the sense of smell and that of taste.


title: Smoking

text: In the 18th century smoking became far more sparse in painting as the elegant practice of taking snuff became popular. Smoking a pipe was again relegated to portraits of lowly commoners and country folk and the refined sniffing of shredded tobacco followed by sneezing was rare in art. When smoking appeared it was often in the exotic portraits influenced by Orientalism. Many proponents of postcolonialism controversially believe this portrayal was a means of projecting an image of European superiority over its colonies and a perception of the male dominance of a feminized Orient. Proponents believe the theme of the exotic and alien "Other" escalated in the 19th century, fueled by the rise in the popularity of ethnology during the Enlightenment.


title: Smoking

text: In the 19th century smoking was common as a symbol of simple pleasures; the pipe smoking "noble savage", solemn contemplation by Classical Roman ruins, scenes of an artists becoming one with nature while slowly toking a pipe. The newly empowered middle class also found a new dimension of smoking as a harmless pleasure enjoyed in smoking saloons and libraries. Smoking a cigarette or a cigar would also become associated with the Bohemian, someone who shunned the conservative middle class values and displayed his contempt for conservatism. But this was a pleasure that was to be confined to a male world; women smokers were associated with prostitution and smoking was not considered an activity fit for proper ladies. It was not until the start of the 20th century that smoking women would appear in paintings and photos, giving a chic and charming impression. Impressionists like Vincent van Gogh, who was a pipe smoker himself, would also begin to associate smoking with gloom and "fin-du-siècle" fatalism.


title: Smoking

text: While the symbolism of the cigarette, pipe and cigar respectively were consolidated in the late 19th century, it was not until the 20th century that artists began to use it fully; a pipe would stand for thoughtfulness and calm; the cigarette symbolized modernity, strength and youth, but also nervous anxiety; the cigar was a sign of authority, wealth and power. The decades following World War II, during the apex of smoking when the practice had still not come under fire by the growing anti-smoking movement, a cigarette casually tucked between the lips represented the young rebel, epitomized in actors like Marlon Brando and James Dean or mainstays of advertising like the Marlboro Man. It was not until the 1970s when the negative aspects of smoking began to appear, yielding the image of the unhealthy lower-class individual, reeking of cigarette smoke and lack of motivation and drive, which was especially prominent in art inspired or commissioned by anti-smoking campaigns. In his painting "Holy Smokes", artist Brian Whelan pokes fun at the smoking debate and its newly found focus on morality and guilt.


title: Smoking

text: Ever since the era of silent films, smoking has had a major part in film symbolism. In the hard-boiled "film noir" crime thrillers, cigarette smoke often frames characters and is frequently used to add an aura of mystique or nihilism. One of the forerunners of this symbolism can be seen in Fritz Lang's Weimar era "Dr Mabuse, der Spieler", 1922 ("Dr Mabuse, the Gambler"), where men mesmerized by card playing smoke cigarettes while gambling.


title: Smoking

text: Female smokers in film were also early on associated with a type of sensuous and seductive sexuality, most notably personified by German film star Marlene Dietrich. Similarly, actors like Humphrey Bogart and Audrey Hepburn have been closely identified with their smoker persona, and some of their most famous portraits and roles have involved them being haloed by a mist of cigarette smoke. Hepburn often enhanced the glamor with a cigarette holder, most notably in the film "Breakfast at Tiffany's". Smoking could also be used as a means to subvert censorship, as two cigarettes burning unattended in an ashtray were often used to suggest sexual activity.


title: Smoking

text: Since World War II, smoking has gradually become less frequent on screen as the obvious health hazards of smoking have become more widely known. With the anti-smoking movement gaining greater respect and influence, conscious attempts not to show smoking on screen are now undertaken in order to avoid encouraging smoking or giving it positive associations, particularly for family films. Smoking on screen is more common today among characters who are portrayed as anti-social or even criminal.


title: Smoking

text: According to a 2019 study, the introduction of television in the United States led to a substantial increase in smoking, in particular among 16–21-year-olds. The study suggested "that television increased the share of smokers in the population by 5–15 percentage points, generating roughly 11 million additional smokers between 1946 and 1970."


title: Smoking

text: Just as in other types of fiction, smoking has had an important place in literature and smokers are often portrayed as characters with great individuality, or outright eccentrics, something typically personified in one of the most iconic smoking literary figures of all, Sherlock Holmes. Other than being a frequent part of short stories and novels, smoking has spawned endless eulogies, praising its qualities and affirming the author's identity as a devoted smoker. Especially during the late 19th century and early 20th century, a panoply of books with titles like "Tobacco: Its History and associations" (1876), "Cigarettes in Fact and Fancy" (1906) and "Pipe and Pouch: The Smokers Own Book of Poetry" (1905) were written in the UK and the US. The titles were written by men for other men and contained general tidbits and poetic musings about the love for tobacco and all things related to it, and frequently praised the refined bachelor's life. "The Fragrant Weed: Some of the Good Things Which Have been Said or Sung about Tobacco", published in 1907, contained, among many others, the following lines from the poem "A Bachelor's Views" by Tom Hall that were typical of the attitude of many of the books:


title: Smoking

text: These works were all published in an era before the cigarette had become the dominant form of tobacco consumption and pipes, cigars, and chewing tobacco were still commonplace. Many of the books were published in novel packaging that would attract the learned smoking gentleman. "Pipe and Pouch" came in a leather bag resembling a tobacco pouch and "Cigarettes in Fact and Fancy" (1901) came bound in leather, packaged in an imitation cardboard cigar box. By the late 1920s, the publication of this type of literature largely abated and was only sporadically revived in the later 20th century.


title: Smoking

text: There have been few examples of tobacco in music in early modern times, though there are occasional signs of influence in pieces such as Johann Sebastian Bach's "Enlightening Thoughts of a Tobacco-Smoker". However, from the early 20th century and onwards smoking has been closely associated with popular music. Jazz was from early on closely intertwined with the smoking that was practiced in the venues where it was played, such as bars, dance halls, jazz clubs and even brothels. The rise of jazz coincided with the expansion of the modern tobacco industry, and in the United States also contributed to the spread of cannabis. The latter went under names like "tea", "muggles" and "reefer" in the jazz community and was so influential in the 1920s and 30s that it found its way into songs composed at the time such as Louis Armstrong's "Muggles", Larry Adler's "Smoking Reefers", and Don Redman's "Chant of The Weed". The popularity of marijuana among jazz musicians remained high until the 1940s and 50s, when it was partially replaced by the use of heroin.


title: Smoking

text: Another form of modern popular music that has been closely associated with cannabis smoking is reggae, a style of music that originated in Jamaica in the late 1950s and early 60s. Cannabis, or "ganja", is believed to have been introduced to Jamaica in the mid-19th century by Indian immigrant labor and was primarily associated with Indian workers until it was appropriated by the Rastafari movement in the middle of the 20th century. The Rastafari considered cannabis smoking to be a way to come closer to God, or Jah, an association that was greatly popularized by reggae icons such as Bob Marley and Peter Tosh in the 1960s and 70s.


title: Smoking

text: Estimates claim that smokers cost the U.S. economy $97.6 billion a year in lost productivity and that an additional $96.7 billion is spent on public and private health care combined. This is over 1% of the gross domestic product. A male smoker in the United States that smokes more than one pack a day can expect an average increase of $19,000 just in medical expenses over the course of his lifetime. A U.S. female smoker that also smokes more than a pack a day can expect an average of $25,800 additional healthcare costs over her lifetime.


title: Tim Horton

text: Miles Gilbert "Tim" Horton (January 12, 1930 – February 21, 1974) was a Canadian professional ice hockey defenceman who played 24 seasons in the National Hockey League (NHL). He played for the Toronto Maple Leafs, New York Rangers, Pittsburgh Penguins, and Buffalo Sabres. In 2017, Horton was named one of the 100 Greatest NHL Players in history. He died following a single-vehicle crash in 1974 caused by driving while intoxicated at the age of 44.


title: Tim Horton

text: Horton was born in Cochrane, Ontario, at Lady Minto Hospital, to Ethel May (née Irish) and Aaron Oakley Horton, a Canadian National Railway mechanic. He had one brother, Gerry Horton.


title: Tim Horton

text: The family moved in 1935 to Duparquet, Quebec, returning to Ontario in 1938 to Cochrane; the family moved to Sudbury in 1945.


title: Tim Horton

text: Horton grew up playing ice hockey in Cochrane, and later in a mining community near Timmins. The Toronto Maple Leafs organization signed him in 1948; he moved to Toronto to play junior hockey and attended St. Michael's College School.


title: Tim Horton

text: Two years later, he turned pro with the Toronto Maple Leafs' farm team, the Pittsburgh Hornets of the American Hockey League. He spent most of the first three seasons with Pittsburgh, playing in his first NHL game on March 26, 1950. Horton appeared in the NHL again in the fall of 1952. He remained a Leaf until 1970, winning four Stanley Cups. Horton later played for the New York Rangers, Pittsburgh Penguins and Buffalo Sabres. He was known for his extreme strength and calmness under pressure. As a hard-working and durable defenceman, he gained relatively few penalty minutes for an enforcer-type defenceman. He was also an effective puck carrier – in 1964–65 he played right wing for the Leafs. Horton appeared in seven National Hockey League All-Star Games. He was named an NHL first team All-Star three times: (1964, 1968, and 1969). He was selected to the NHL Second Team three times: (1954, 1963, 1967).


title: Tim Horton

text: Between February 11, 1961, and February 4, 1968, Horton appeared in 486 consecutive regular season games; this remains the Leafs club record for consecutive games and was the NHL record for consecutive games by a defenceman until broken by Kārlis Skrastiņš on February 8, 2007.


title: Tim Horton

text: While playing, Horton was generally acknowledged as the strongest man in the game; injuries and age were little more than minor inconveniences. Chicago Black Hawks left wing Bobby Hull declared, "There were defencemen you had to fear because they were vicious and would slam you into the boards from behind, for one, Eddie Shore. But you respected Tim Horton because he didn't need "that" type of intimidation. He used his tremendous strength and talent to keep you in check."


title: Tim Horton

text: In 1962, he scored three goals and 13 assists in 12 playoff games, setting a Leafs team record for playoff points by a defenceman. This record was tied in 1978 by Ian Turnbull (who played 13 games), but was not broken until 1994, when David Ellett registered 18 points (albeit in 18 games).


title: Tim Horton

text: In March 1970, the Maple Leafs traded Horton to the New York Rangers for future considerations; he spent the last fifteen games of the season in New York and all of the following as well. At the beginning of the 1971–72 season, he was claimed by the Pittsburgh Penguins in the intra-league draft and, at age 41, signed a one-year contract for an estimated $100,000, the largest contract at the time for the five-year-old franchise. With a broken ankle and a shoulder separation, Horton only played 44 games for the Penguins and managed just 11 points.


title: Tim Horton

text: In spite of Horton's age, 42, and considerable nearsightedness, Punch Imlach of the Buffalo Sabres, who was also the former Leafs' general manager, acquired Horton in the Intra-league draft and signed him in 1972. In 1973, his performance assisted the Sabres in their first playoff appearance. Horton later signed a contract extension in the off-season.


title: Tim Horton

text: While playing for the Leafs, Horton wore the number 7, the same number worn by King Clancy from 1930 to 1937. The team declared both Horton and Clancy honoured players at a ceremony on November 21, 1995, but did not retire the number 7 from team use; despite this, it became an honoured jersey number, abiding by Leafs honours policy. In 2016, the Leafs changed their retirement policy and, on October 15, retired the number 7 in honour of both Horton and Clancy.


title: Tim Horton

text: Horton wore number 2 in Buffalo (as Rick Martin already had the number 7). Both numbers have since been retired.


title: Tim Horton

text: In 1964, Horton opened his first Tim Horton Doughnut Shop in Hamilton, Ontario on Ottawa Street. He added a few of his culinary creations to the initial menu. By 1968, Tim Horton had become a multi-million dollar franchise system. Horton's previous business ventures included both a hamburger restaurant and Studebaker auto dealership in Toronto.


title: Tim Horton

text: Upon Horton's death in 1974, his business partner Ron Joyce bought out the Horton family's shares for $1 million and took over as sole owner of the existing chain, which had 40 stores at the time, and later expanded to nearly 4,600 stores in Canada alone by 2013. Today, Tim Hortons is a flagship of Restaurant Brands International, a conglomerate that includes Burger King and Popeyes Louisiana Kitchen. Restaurant Brands International is majority-owned by Brazilian investment firm 3G Capital.


title: Tim Horton

text: Joyce's son, Ron Joyce Jr., is married to Horton's eldest daughter, Jeri-Lynn Horton-Joyce; the couple own Tim Hortons franchises in Cobourg, Ontario.


title: Tim Horton

text: Horton was killed after losing control of his De Tomaso Pantera sports car on the Queen Elizabeth Way in St. Catharines, Ontario, in the early morning of February 21, 1974. He had played a game in Toronto the previous evening against his former team, the Maple Leafs, and was driving alone back to Buffalo, south. The Sabres had lost the game, and despite sitting out the third period and playing with a jaw and ankle injury, Horton was selected one of the game's three stars.


title: Tim Horton

text: Horton's Pantera had been given to him by Sabres' general manager Imlach as an enticement to return to the team for one more season.


title: Tim Horton

text: On his drive to Buffalo, Horton stopped at his office in Oakville, and was met there by Ron Joyce. While there, Horton phoned his brother Gerry, who recognized that Tim had been drinking and tried to persuade him not to continue driving. Joyce also offered to have Horton stay with him. Horton chose to continue his drive to Buffalo.


title: Tim Horton

text: After 4:00 a.m. EST (9:00 UTC), a woman reported to the Ontario Provincial Police in Burlington that she had observed a car travelling at high speed on the Queen Elizabeth Way. A warning was broadcast over police radio. Thirty minutes later, Constable Mike Gula observed a speeding vehicle travelling Niagara-bound on the Queen Elizabeth Way in Vineland. Gula activated his emergency lights and siren and attempted to pursue Horton's vehicle, but lost sight of it.


title: Tim Horton

text: Horton passed a curve in the road at Ontario Street and was approaching the Lake Street exit in St. Catharines when he lost control and drove into the centre grass median, where his tire caught a recessed sewer which caused the car to flip several times before it came to a stop on its roof in the Toronto-bound lanes. Not wearing a seatbelt, Horton was found from the car. He was pronounced dead at St. Catharines General Hospital.


title: Tim Horton

text: Subsequent to Horton's death, there was no official public inquiry, and his autopsy was not made public. Police would not state whether Horton was intoxicated. In 2005, Horton's autopsy was made public (with witness statements redacted), and revealed that Horton's blood alcohol level was twice the legal limit, and that a half-filled vodka bottle was amongst the crash debris. Horton was also in possession of the drugs Dexedrine, a stimulant, and Dexamyl, a stimulant-sedative; traces of amobarbital, an ingredient in Dexamyl, were found in his blood. The autopsy report found no painkillers in Horton's body, and also concluded that his car had been in good working order. There was nothing to suggest Horton was evading police, or that police were near enough to initiate a criminal pursuit. Horton was interred at York Cemetery, Toronto.


title: Tim Horton

text: Married in 1952, he was survived by his wife, the former Lori Michalek of Pittsburgh, and four daughters.


title: Tim Horton

text: Following Horton's death, Ron Joyce offered Horton's widow Lori $1 million for her shares in the chain, which included 40 stores. She accepted his offer and Joyce became sole owner. Years later, Lori became dissatisfied with Joyce's offer, and filed a lawsuit against him. In 1993, Lori lost the lawsuit; an appeal was declined in 1995. She died in 2000 at age 68.


title: Ptosis (eyelid)

text: Ptosis, also known as blepharoptosis, is a drooping or falling of the upper eyelid. The drooping may be worse after being awake longer when the individual's muscles are tired. This condition is sometimes called "lazy eye", but that term normally refers to the condition amblyopia. If severe enough and left untreated, the drooping eyelid can cause other conditions, such as amblyopia or astigmatism. This is why it is especially important for this disorder to be treated in children at a young age, before it can interfere with vision development.


title: Ptosis (eyelid)

text: Ptosis occurs due to dysfunction of the muscles that raise the eyelid or their nerve supply (oculomotor nerve for levator palpebrae superioris and sympathetic nerves for superior tarsal muscle). It can affect one eye or both eyes and is more common in the elderly, as muscles in the eyelids may begin to deteriorate. One can, however, be born with ptosis. This is due to improper development of the infant's levator muscle while still in the mother's womb. Congenital ptosis is hereditary in three main forms. Causes of congenital ptosis remain unknown. Ptosis may be caused by damage to the muscle which raises the eyelid, damage to the superior cervical sympathetic ganglion or damage to the nerve (3rd cranial nerve (oculomotor nerve)) which controls this muscle. Such damage could be a sign or symptom of an underlying disease such as diabetes mellitus, a brain tumor, a pancoast tumor (apex of lung) and diseases which may cause weakness in muscles or nerve damage, such as myasthenia gravis or oculopharyngeal muscular dystrophy. Exposure to the toxins in some snake venoms, such as that of the black mamba, may also cause this effect.


title: Ptosis (eyelid)

text: Ptosis can be caused by the aponeurosis of the levator muscle, nerve abnormalities, trauma, inflammation or lesions of the lid or orbit. Dysfunctions of the levators may occur as a result of autoimmune antibodies attacking and eliminating the neurotransmitter.


title: Ptosis (eyelid)

text: Ptosis may be due to a myogenic, neurogenic, aponeurotic, mechanical or traumatic cause, and it usually occurs isolated, but may be associated with various other conditions, like immunological, degenerative, or hereditary disorders, tumors or infections.


title: Ptosis (eyelid)

text: Acquired ptosis is most commonly caused by aponeurotic ptosis. This can occur as a result of senescence, dehiscence or disinsertion of the levator aponeurosis. Moreover, chronic inflammation or intraocular surgery can lead to the same effect. Also, wearing contact lenses for long periods of time is thought to have a certain impact on the development of this condition.


title: Ptosis (eyelid)

text: Congenital neurogenic ptosis is believed to be caused by Horner's syndrome. In this case, a mild ptosis may be associated with ipsilateral ptosis, iris and areola hypopigmentation and anhidrosis due to paresis of the superior tarsal muscle. Acquired Horner syndrome may result after trauma, neoplastic insult, or even vascular disease.


title: Ptosis (eyelid)

text: Ptosis due to trauma can ensue after an eyelid laceration with transection of the upper eyelid elevators or disruption of the neural input.


title: Ptosis (eyelid)

text: Other causes of ptosis include eyelid neoplasms, neurofibromas or the cicatrization after inflammation or surgery. Mild ptosis may occur with aging.


title: Ptosis (eyelid)

text: A drooping eyelid can be one of the first signals of a third nerve palsy due to a cerebral aneurysm, that otherwise is asymptomatic and referred to as an oculomotor nerve palsy.


title: Ptosis (eyelid)

text: Use of high doses of opioid drugs such as morphine, oxycodone, heroin, or hydrocodone can cause ptosis. Pregabalin, an anticonvulsant drug, has also been known to cause mild ptosis.


title: Ptosis (eyelid)

text: Different trauma can cause and induce many different mechanisms. For example, myogenic ptosis results from a direct injury to the levator muscle and/or Müller's muscle. On the other hand, neurogenic ptosis is caused by closed head injuries, or traumatically-introduced neurotoxin (wasp/bee/snake venom) or botulinum toxin, due to the effect of those factors on the CNIII or the sympathetic pathway. Mechanical ptosis can also occur due to scarring tissue restricting the patient's eyelid excursion or weighing down the patient's lid. Another mechanism is the disturbance of the oculomotor nerve causing the levator palpebrae to weaken, resulting in the eyelid drooping. Ptosis can also occur in a patient with brain tumors due to pressure on the third nerve, also known as the sympathetic nerve, on the brainstem.


title: Ptosis (eyelid)

text: Myasthenia gravis is a common neurogenic ptosis which could be also classified as neuromuscular ptosis because the site of pathology is at the neuromuscular junction. Studies have shown that up to 70% of myasthenia gravis patients present with ptosis, and 90% of these patients will eventually develop ptosis. In this case, ptosis can be unilateral or bilateral and its severity tends to be oscillating during the day, because of factors such as fatigue or drug effect. This particular type of ptosis is distinguished from the others with the help of a Tensilon test and blood tests. Also, specific to myasthenia gravis is the fact that coldness inhibits the activity of cholinesterase, which makes possible differentiating this type of ptosis by applying ice onto the eyelids. Patients with myasthenic ptosis are very likely to still experience a variation of the drooping of the eyelid at different hours of the day.


title: Ptosis (eyelid)

text: Ptosis caused by oculomotor palsy can be unilateral or bilateral, as the subnucleus to the levator muscle is a shared, midline structure in the brainstem. In cases in which the palsy is caused by the compression of the nerve by a tumor or aneurysm, it is highly likely to result in an abnormal ipsilateral papillary response and a larger pupil. Surgical third nerve palsy is characterized by a sudden onset of unilateral ptosis and an enlarged or sluggish pupil to the light. In this case, imaging tests such as CTs or MRIs should be considered. Medical third nerve palsy, contrary to surgical third nerve palsy, usually does not affect the pupil and it tends to slowly improve in several weeks. Surgery to correct ptosis due to medical third nerve palsy is normally considered only if the improvement of ptosis and ocular motility are unsatisfactory after half a year. Patients with third nerve palsy tend to have diminished or absent function of the levator.


title: Ptosis (eyelid)

text: When caused by Horner's syndrome, ptosis is usually accompanied by miosis and anhidrosis. In this case, the ptosis is due to the result of interruption innervations to the sympathetic, autonomic Muller's muscle rather than the somatic levator palpebrae superioris muscle. The lid position and pupil size are typically affected by this condition and the ptosis is generally mild, no more than 2 mm. The pupil might be smaller on the affected side. While 4% cocaine instilled to the eyes can confirm the diagnosis of Horner's syndrome, Hydroxyamphetamine eye drops can differentiate the location of the lesion.


title: Ptosis (eyelid)

text: Chronic progressive external ophthalmoplegia is a systemic condition which usually affects only the lid position and the external eye movement, without involving the movement of the pupil. This condition accounts for nearly 45% of myogenic ptosis cases. Most patients develop ptosis due to this disease in their adulthood. Characteristic to ptosis caused by this condition is the fact that the protective up rolling of the eyeball when the eyelids are closed is very poor.


title: Ptosis (eyelid)

text: A doctor will first perform a physical exam with questions about the patient's medical history to distinguish whether the condition may be hereditary. A slit lamp exam is performed with a high-intensity light that allows a close look at the patient's eyes. The doctor can also perform a test in which edrophonium is injected into a vein and the eyelids are monitored for resulting signs of improvement.


title: Ptosis (eyelid)

text: A visual field test, which assesses the degree to which the ptosis affects the superior vision, may be performed. Because nerve damage is among the possible causes for ptosis, the ophthalmologist will check the patient's pupil for abnormalities. The doctor will also check muscle function.


title: Ptosis (eyelid)

text: The ophthalmologist may also measure the degree of the eyelid droop by measuring the marginal reflex distance, which is the distance between the center of the pupil and the edge of the upper lid, as well as the strength and function of the patient's levator muscle. This test entails holding the frontalis muscle to measure how far the eyelid travels when the patient is gazing downward.


title: Ptosis (eyelid)

text: Through these tests, the ophthalmologist may properly diagnose ptosis and identify its classification, and a determination may be made regarding the course of treatment, which may involve surgery.


title: Ptosis (eyelid)

text: Aponeurotic and congenital ptosis may require surgical correction if severe enough to interfere with the vision or if appearance is a concern. Treatment depends on the type of ptosis, and is usually performed by an ophthalmic plastic surgeon or a reconstructive surgeon who specializes in diseases and problems of the eyelid.


title: Ptosis (eyelid)

text: If the condition occurs in a child, then the doctor will delay the surgery until the patient is 4 or 5 years old. If the patient is under the recommended age for surgery, then the doctor will test if occlusion therapy can compensate for the patient's impeded vision. The reason for delaying the surgery until the patient is at least 4–5 years of age is the necessity of delay for the frontonasal and upper face to complete their complex growth. After this complex growth is complete, the doctors will be able to obtain a more accurate measurement of the conditions. However, if the patient's vision impediment worsens or proves unresponsive to the occlusion therapy, then surgery will be needed sooner.


title: Ptosis (eyelid)

text: The frontalis sling surgery can only be done if the patient's ptosis condition is due to diseased or stretched-out muscles. The stretching-out of muscle is due to age. The frontalis sling surgery is done to either tighten or shorten the affected muscles, thereby allowing the process to raise the patient's lid's resting position. The procedure is done with the doctor using the sling to loop the material, then threading it underneath the patient's eyebrows and above the lashes. Once the sling has been tightened, this allows the patient's forehead's muscle to aid in lifting the lid. The sling can be looped in a pentagon shape, triangle (singular or double) shape. Many different types of slings in the market today include monofilament nylon, silicone rods, polyester, silk, collagen, stainless steel or polypropylene.


title: Ptosis (eyelid)

text: Frontalis sling surgery is considered the most effective surgical treatment for moderate to severe congenital ptosis. Many different materials can be used for the surgery, though it is currently unclear which material has the highest success rate.


title: Ptosis (eyelid)

text: The levator resection and advancement surgery should only be considered for patients who are experiencing a levator function less than or equal to 5 mm. The levator function is a measurement of the distance that the eyelid travels starting with the downgaze moving to the upgaze without moving the frontalis muscle. Although this procedure can be completed through two different approaches, the internal and the external, the external approach allows the surgeons to obtain a better view of the surgical site during the procedure. The surgeon will begin with an incision on the eyelid. Once the levator has been exposed, the surgeon either fold it or cut it off before suturing it to the tarsal plate. During this procedure, it is up to the surgeon to decide the height and the contour of the patient's eyelid, with input from the patient.


title: Ptosis (eyelid)

text: The Whitnall sling procedure is done with an incision from the levator to the Whitnall ligament. Then the surgeon will suture the Whitnall's ligament connecting it to the superior tarsal edge. This procedure most likely is done if the patients are concerned about cosmetic appearance. The Whitnall sling procedure is able to provide a better cosmetic result because the procedure is able to keep the Whitnall's ligament intact. This allows the support of the lacrimal gland and temporal eyelid to be maintained.


title: Ptosis (eyelid)

text: Despite the gains that the patient can obtain from the surgeries, there are risk factors. After the surgery, the patient may experience asymmetrical (uneven) eyelids. If the surgery was not done carefully, the patient may experience dry eyes owing to the eye no longer fully closing. The patient may also experience bleeding after the surgery and infections, if the surgical site is not taken care of properly. On rare occasions, the patient will experience a loss in eyelid movement.


title: Ptosis (eyelid)

text: Non-surgical modalities like the use of "crutch" glasses or ptosis crutches or special scleral contact lenses to support the eyelid may also be used.


title: Ptosis (eyelid)

text: Ptosis that is caused by a disease may improve if the disease is treated successfully, although some related diseases, such as oculopharyngeal muscular dystrophy, currently have no cures.


title: Ptosis (eyelid)

text: If the ptosis is left untreated, then patients may experience amblyopia, also known as lazy eye, which can permanently damage the patient's vision. After careful observation and planning from specialists, ptosis can be successfully treated. Treatment like surgery will allow the patient to begin experiencing improvement in vision as well as cosmetic results. In a study of patients who were previously treated for ptosis, half required additional surgery within 8 to 10 years of the first surgery. If the ptosis is not related to major health issues (such as cancerous tumours or traumatic injuries), then the condition will not shorten the patient's life expectancy.


title: Ptosis (eyelid)

text: According to ophthalmology studies done on ptosis patients, occurrence rates are as follows. The average age for females experiencing aponeurotic ptosis is 67.83 years and the corresponding male average age is 68.19. The average age for congenital ptosis is 12.27 years for females and 8.57 years for males. The average age for mechanical ptosis is 49.41 years in females and 43.30 years in males. The average age for myogenic ptosis is 53.45 for females and 43.30 for males. The average age for neurogenic ptosis is 43.6 years in females and 32.62 years in males. Lastly, the average age for traumatic ptosis is 35.12 years in females and 33.4 years in males. Ptosis was not found to have any overall gender or racial preference.


title: Ptosis (eyelid)

text: Current studies have indicated that previous methods such as occlusion therapy and surgery are considered to be the most appropriate for treating this condition. Further studies are encouraged to be able to determine the optimal surgical indications. Any discoveries on approaches with dry eye will help further the oculoplastic surgeries.


title: Ptosis (eyelid)

text: Ptosis is derived from the Greek word πτῶσις ("ptōsis", "fall"), and is defined as the "abnormal lowering or prolapse of an organ or body part".


title: Border Gateway Protocol

text: Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. BGP is classified as a path-vector routing protocol, and it makes routing decisions based on paths, network policies, or rule-sets configured by a network administrator.


title: Border Gateway Protocol

text: BGP used for routing within an autonomous system is called Interior Border Gateway Protocol, Internal BGP (iBGP). In contrast, the Internet application of the protocol is called Exterior Border Gateway Protocol, External BGP (eBGP).


title: Border Gateway Protocol

text: The Border Gateway Protocol was sketched out in 1989 by engineers on the back of "three ketchup-stained napkins", and is still known as the "three-napkin protocol". It was first described in 1989 in RFC 1105, and has been in use on the Internet since 1994. IPv6 BGP was first defined in in 1994, and it was improved to in 1998.


title: Border Gateway Protocol

text: The current version of BGP is version 4 (BGP4), which was published as RFC 4271 in 2006. RFC 4271 corrected errors, clarified ambiguities and updated the specification with common industry practices. The major enhancement was the support for Classless Inter-Domain Routing (CIDR) and use of route aggregation to decrease the size of routing tables. The new RFC allows BGP4 to carry a wide range of IPv4 and IPv6 "address families". It is also called the Multiprotocol Extensions which is Multiprotocol BGP (MP-BGP).


title: Border Gateway Protocol

text: BGP neighbors, called peers, are established by manual configuration among routers to create a TCP session on port 179. A BGP speaker sends 19-byte keep-alive messages every 30 seconds (protocol default value, tunable) to maintain the connection. Among routing protocols, BGP is unique in using TCP as its transport protocol.


title: Border Gateway Protocol

text: When BGP runs between two peers in the same autonomous system (AS), it is referred to as "Internal BGP" ("iBGP" or "Interior Border Gateway Protocol"). When it runs between different autonomous systems, it is called "External BGP" ("eBGP" or "Exterior Border Gateway Protocol"). Routers on the boundary of one AS exchanging information with another AS are called "border" or "edge routers" or simply "eBGP peers" and are typically connected directly, while "iBGP peers" can be interconnected through other intermediate routers. Other deployment topologies are also possible, such as running eBGP peering inside a VPN tunnel, allowing two remote sites to exchange routing information in a secure and isolated manner.


title: Border Gateway Protocol

text: The main difference between iBGP and eBGP peering is in the way routes that were received from one peer are typically propagated by default to other peers:


title: Border Gateway Protocol

text: These route-propagation rules effectively require that all iBGP peers inside an AS are interconnected in a full mesh with iBGP sessions.


title: Border Gateway Protocol

text: How routes are propagated can be controlled in detail via the "route-maps" mechanism. This mechanism consists of a set of rules. Each rule describes, for routes matching some given criteria, what action should be taken. The action could be to drop the route, or it could be to modify some attributes of the route before inserting it in the routing table.


title: Border Gateway Protocol

text: During the peering handshake, when OPEN messages are exchanged, BGP speakers can negotiate optional capabilities of the session, including multiprotocol extensions and various recovery modes. If the multiprotocol extensions to BGP are negotiated at the time of creation, the BGP speaker can prefix the Network Layer Reachability Information (NLRI) it advertises with an address family prefix. These families include the IPv4 (default), IPv6, IPv4/IPv6 Virtual Private Networks and multicast BGP. Increasingly, BGP is used as a generalized signaling protocol to carry information about routes that may not be part of the global Internet, such as VPNs.


title: Border Gateway Protocol

text: In order to make decisions in its operations with peers, a BGP peer uses a simple finite state machine (FSM) that consists of six states: Idle; Connect; Active; OpenSent; OpenConfirm; and Established. For each peer-to-peer session, a BGP implementation maintains a state variable that tracks which of these six states the session is in. The BGP defines the messages that each peer should exchange in order to change the session from one state to another.


title: Border Gateway Protocol

text: The first state is the Idle state. In the Idle state, BGP initializes all resources, refuses all inbound BGP connection attempts and initiates a TCP connection to the peer. The second state is Connect. In the Connect state, the router waits for the TCP connection to complete and transitions to the OpenSent state if successful. If unsuccessful, it starts the ConnectRetry timer and transitions to the Active state upon expiration. In the Active state, the router resets the ConnectRetry timer to zero and returns to the Connect state. In the OpenSent state, the router sends an Open message and waits for one in return in order to transition to the OpenConfirm state. Keepalive messages are exchanged and, upon successful receipt, the router is placed into the Established state. In the Established state, the router can send and receive: Keepalive; Update; and Notification messages to and from its peer.


title: Border Gateway Protocol

text: In the simplest arrangement, all routers within a single AS and participating in BGP routing must be configured in a full mesh: each router must be configured as a peer to every other router. This causes scaling problems, since the number of required connections grows quadratically with the number of routers involved. To alleviate the problem, BGP implements two options: route reflectors (RFC 4456) and BGP confederations (RFC 5065). The following discussion of basic update processing assumes a full iBGP mesh.


title: Border Gateway Protocol

text: A given BGP router may accept network-layer reachability information (NLRI) updates from multiple neighbors and advertise NLRI to the same, or a different set, of neighbors. The BGP process maintains several routing information base:


title: Border Gateway Protocol

text: The physical storage and structure of these conceptual tables are decided by the implementer of the BGP code. Their structure is not visible to other BGP routers, although they usually can be interrogated with management commands on the local router. It is quite common, for example, to store the codice_3, codice_4 and the codice_2 together in the same data structure, with additional information attached to the RIB entries. The additional information tells the BGP process such things as whether individual entries belong in the codice_8 for specific neighbors, whether the peer-neighbor route selection process made received policies eligible for the codice_2, and whether codice_2 entries are eligible to be submitted to the local router's routing table management process.


title: Border Gateway Protocol

text: BGP submits the routes that it considers best to the main routing table process. Depending on the implementation of that process, the BGP route is not necessarily selected. For example, a directly connected prefix, learned from the router's own hardware, is usually most preferred. As long as that directly connected route's interface is active, the BGP route to the destination will not be put into the routing table. Once the interface goes down, and there are no more preferred routes, the Loc-RIB route would be installed in the main routing table.


title: Border Gateway Protocol

text: BGP carries the information with which rules inside BGP-speaking routers can make policy decisions. Some of the information carried that is explicitly intended to be used in policy decisions are:


title: Border Gateway Protocol

text: The BGP standard specifies a number of decision factors, more than the ones that are used by any other common routing process, for selecting NLRI to go into the Loc-RIB. The first decision point for evaluating NLRI is that its next-hop attribute must be reachable (or resolvable). Another way of saying the next-hop must be reachable is that there must be an active route, already in the main routing table of the router, to the prefix in which the next-hop address is reachable.


title: Border Gateway Protocol

text: Next, for each neighbor, the BGP process applies various standard and implementation-dependent criteria to decide which routes conceptually should go into the Adj-RIB-In. The neighbor could send several possible routes to a destination, but the first level of preference is at the neighbor level. Only one route to each destination will be installed in the conceptual Adj-RIB-In. This process will also delete, from the Adj-RIB-In, any routes that are withdrawn by the neighbor.


title: Border Gateway Protocol

text: Whenever a conceptual Adj-RIB-In changes, the main BGP process decides if any of the neighbor's new routes are preferred to routes already in the Loc-RIB. If so, it replaces them. If a given route is withdrawn by a neighbor, and there is no other route to that destination, the route is removed from the Loc-RIB and no longer sent by BGP to the main routing table manager. If the router does not have a route to that destination from any non-BGP source, the withdrawn route will be removed from the main routing table.


title: Border Gateway Protocol

text: The local preference, weight, and other criteria can be manipulated by local configuration and software capabilities. Such manipulation, although commonly used, is outside the scope of the standard. For example, the "community" attribute (see below) is not directly used by the BGP selection process. The BGP neighbor process can have a rule to set local preference or another factor based on a manually programmed rule to set the attribute if the community value matches some pattern-matching criterion. If the route was learned from an external peer the per-neighbor BGP process computes a local preference value from local policy rules and then compares the local preference of all routes from the neighbor.


title: Border Gateway Protocol

text: BGP communities are attribute tags that can be applied to incoming or outgoing prefixes to achieve some common goal. While it is common to say that BGP allows an administrator to set policies on how prefixes are handled by ISPs, this is generally not possible, strictly speaking. For instance, BGP natively has no concept to allow one AS to tell another AS to restrict advertisement of a prefix to only North American peering customers. Instead, an ISP generally publishes a list of well-known or proprietary communities with a description for each one, which essentially becomes an agreement of how prefixes are to be treated.


title: Border Gateway Protocol

text: The customer simply adjusts their configuration to include the correct community or communities for each route, and the ISP is responsible for controlling who the prefix is advertised to. The end user has no technical ability to enforce correct actions being taken by the ISP, though problems in this area are generally rare and accidental.


title: Border Gateway Protocol

text: It is a common tactic for end customers to use BGP communities (usually ASN:70,80,90,100) to control the local preference the ISP assigns to advertised routes instead of using MED (the effect is similar). The community attribute is transitive, but communities applied by the customer very rarely propagated outside the next-hop AS. Not all ISPs give out their communities to the public.


title: Border Gateway Protocol

text: The BGP Extended Community Attribute was added in 2006, in order to extend the range of such attributes and to provide a community attribute structuring by means of a type field. The extended format consists of one or two octets for the type field followed by seven or six octets for the respective community attribute content. The definition of this Extended Community Attribute is documented in RFC 4360. The IANA administers the registry for BGP Extended Communities Types. The Extended Communities Attribute itself is a transitive optional BGP attribute. A bit in the type field within the attribute decides whether the encoded extended community is of a transitive or non-transitive nature. The IANA registry therefore provides different number ranges for the attribute types. Due to the extended attribute range, its usage can be manifold. RFC 4360 exemplarily defines the "Two-Octet AS Specific Extended Community", the "IPv4 Address Specific Extended Community", the "Opaque Extended Community", the "Route Target Community", and the "Route Origin Community". A number of BGP QoS drafts also use this Extended Community Attribute structure for inter-domain QoS signalling.


title: Border Gateway Protocol

text: With the introduction of 32-bit AS numbers, some issues were immediately obvious with the community attribute that only defines a 16 bits ASN field, which prevents the matching between this field and the real ASN value. Since RFC 7153, extended communities are compatible with 32-bit ASNs. RFC 8092 and RFC 8195 introduce a Large Community attribute of 12 bytes, divided in three field of 4 bytes each (AS:function:parameter).


title: Border Gateway Protocol

text: MEDs, defined in the main BGP standard, were originally intended to show to another neighbor AS the advertising AS's preference as to which of several links are preferred for inbound traffic. Another application of MEDs is to advertise the value, typically based on delay, of multiple ASs that have a presence at an IXP, that they impose to send traffic to some destination.


title: Border Gateway Protocol

text: If there is an error it is because one of the fields in the OPEN or UPDATE message does not match between the peers, e.g., BGP version mismatch, the peering router expects a different My AS, etc. The router then sends a Notification message to the peer indicating why the error occurred.


title: Border Gateway Protocol

text: An autonomous system with internal BGP (iBGP) must have all of its iBGP peers connect to each other in a full mesh (where everyone speaks to everyone directly). This full-mesh configuration requires that each router maintain a session with every other router. In large networks, this number of sessions may degrade the performance of routers, due to either a lack of memory, or high CPU process requirements.


title: Border Gateway Protocol

text: Route reflectors (RRs) reduce the number of connections required in an AS. A single router (or two for redundancy) can be made an RR: other routers in the AS need only be configured as peers to them. An RR offers an alternative to the logical full-mesh requirement of iBGP. The purpose of the RR is concentration. Multiple BGP routers can peer with a central point, the RR acting as an RR server rather than peer with every other router in a full mesh. All the other iBGP routers become RR clients.


title: Border Gateway Protocol

text: This approach, similar to OSPF's DR/BDR feature, provides large networks with added iBGP scalability. In a fully meshed iBGP network of 10 routers, 90 individual CLI statements (spread throughout all routers in the topology) are needed just to define the remote-AS of each peer: this quickly becomes a headache to manage. An RR topology can cut these 90 statements down to 18, offering a viable solution for the larger networks administered by ISPs.


title: Border Gateway Protocol

text: An RR is a single point of failure, therefore at least a second RR may be configured in order to provide redundancy. As it is an additional peer for the other 10 routers, it approximately doubles the number of CLI statements, requiring an additional statements in this case. In a BGP multipath environment the additional RR also can benefit the network by adding local routing throughput if the RRs are acting as traditional routers instead of just a dedicated RR server role.


title: Border Gateway Protocol

text: RRs and confederations both reduce the number of iBGP peers to each router and thus reduce processing overhead. RRs are a pure performance-enhancing technique, while confederations also can be used to implement more fine-grained policy.


title: Border Gateway Protocol

text: An RR and its clients form a "cluster". The "cluster ID" is then attached to every route advertised by the RR to its client or nonclient peers. A cluster ID is a cumulative, non-transitive BGP attribute, and every RR must prepend the local cluster ID to the cluster list to avoid routing loops.


title: Border Gateway Protocol

text: Confederations are sets of autonomous systems. In common practice, only one of the confederation AS numbers is seen by the Internet as a whole. Confederations are used in very large networks where a large AS can be configured to encompass smaller more manageable internal ASs.


title: Border Gateway Protocol

text: The confederated AS is composed of multiple ASs. Each confederated AS alone has iBGP fully meshed and has connections to other ASs inside the confederation. Even though these ASs have eBGP peers to ASs within the confederation, the ASs exchange routing as if they used iBGP. In this way, the confederation preserves next hop, metric, and local preference information. To the outside world, the confederation appears to be a single AS. With this solution, iBGP transit AS problems can be resolved as iBGP requires a full mesh between all BGP routers: large number of TCP sessions and unnecessary duplication of routing traffic.


title: Border Gateway Protocol

text: Confederations can be used in conjunction with route reflectors. Both confederations and route reflectors can be subject to persistent oscillation unless specific design rules, affecting both BGP and the interior routing protocol, are followed.


title: Border Gateway Protocol

text: Additionally, route reflectors and BGP confederations were not designed to ease BGP router configuration. Nevertheless, these are common tools for experienced BGP network architects. These tools may be combined, for example, as a hierarchy of route reflectors.


title: Border Gateway Protocol

text: The routing tables managed by a BGP implementation are adjusted continually to reflect actual changes in the network, such as links or routers going down and coming back up. In the network as a whole, it is normal for these changes to happen almost continuously, but for any particular router or link, changes are expected to be relatively infrequent. If a router is misconfigured or mismanaged then it may get into a rapid cycle between down and up states. This pattern of repeated withdrawal and re-announcement known as route flapping can cause excessive activity in all the other routers that know about the cycling entity, as the same route is continually injected and withdrawn from the routing tables. The BGP design is such that delivery of traffic may not function while routes are being updated. On the Internet, a BGP routing change may cause outages for several minutes.


title: Border Gateway Protocol

text: A feature known as "route flap damping" (RFC 2439) is built into many BGP implementations in an attempt to mitigate the effects of route flapping. Without damping, the excessive activity can cause a heavy processing load on routers, which may in turn delay updates on other routes, and so affect overall routing stability. With damping, a route's flapping is exponentially decayed. At the first instance when a route becomes unavailable and quickly reappears, damping does not take effect, so as to maintain the normal fail-over times of BGP. At the second occurrence, BGP shuns that prefix for a certain length of time; subsequent occurrences are timed out exponentially. After the abnormalities have ceased and a suitable length of time has passed for the offending route, prefixes can be reinstated and its slate wiped clean. Damping can also mitigate denial of service attacks; damping timings are highly customizable.