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Isle of Wight

The Isle of Wight (/waɪt/ WYTE) is an island, English county and unitary authority in the English Channel, 2 to 5 miles off the coast of Hampshire, across the Solent. It is the largest and second-most populous island in England. Referred to as "The Island" by residents, the Isle of Wight has resorts that have been popular holiday destinations since Victorian times. It is known for its mild climate, coastal scenery, and verdant landscape of fields, downland, and chines. The island is historically part of Hampshire. The island is designated a UNESCO Biosphere Reserve. With a land area of 380 km2, it is about half the size of Singapore.

The island has been home to the poets Algernon Charles Swinburne and Alfred, Lord Tennyson. Queen Victoria built her summer residence and final home, Osborne House, at East Cowes on the Isle. It has a maritime and industrial tradition of boat-building, sail-making, the manufacture of flying boats, hovercraft, and Britain's space rockets. The island hosts annual music festivals, including the Isle of Wight Festival, which in 1970 was the largest rock music event ever held. It has well-conserved wildlife and some of Europe's richest cliffs and quarries of dinosaur fossils.

The island has played an essential part in the defence of the ports of Southampton and Portsmouth and has been near the front line of conflicts through the ages, having faced the Spanish Armada and weathered the Battle of Britain. Being rural for most of its history, its Victorian fashionability and the growing affordability of holidays led to significant urban development during the late 19th and early 20th centuries.

The island was historically a part of Hampshire, but became a separate administrative county in 1890. It had continued to share the Lord Lieutenant of Hampshire until 1974, when it was made a ceremonial county in its own right. The island no longer has administrative links to Hampshire. However, the two counties continue to share their police force and fire and rescue service, and the island's Anglican churches belong to the Diocese of Portsmouth (originally Winchester). A combined local authority with Portsmouth and Southampton was considered as part of a regional devolution package but was subsequently rejected by the UK government in 2018.

The quickest public transport link to the mainland is the hovercraft (Hovertravel) from Ryde to Southsea. Three vehicle ferries and two catamaran services cross the Solent to Southampton, Lymington, and Portsmouth via the island's largest ferry operator, Wightlink, and the island's second-largest ferry company, Red Funnel. Tourism is the largest industry on the island.

Name
The oldest records that give a name for the Isle of Wight are from the Roman Empire. It was called Vectis or Vecta in Latin and Iktis or Ouiktis in Greek. Latin Vecta, Old English Wiht, and Old Welsh Gueid and Guith were recorded from the Anglo-Saxon period. The Domesday Book called the island Wit. The modern Welsh name is Ynys Wyth (ynys meaning island). These are all variants of the same name, possibly sharing a Celtic origin with Welsh gwaith 'work', a cognate of both Latin vectis ("lever," or literally "the act of lifting") and Old English wiht ("weight"). It may mean 'place of the division,' since the island divides the two arms of the Solent.

In Old English, inhabitants of the Isle were known as Wihtware.

Stone Age
During Pleistocene glacial periods sea levels were lower than at present, and the area that today forms the Solent was part of the valley of the now extinct Solent River. The river flowed eastward from Dorset, following the course of the modern Solent strait. The river travelled east of the Isle of Wight before flowing southwest towards the major Channel River system. At these times, extensive gravel terraces associated with the Solent River and the forerunners of the island's modern rivers were deposited. During warmer interglacial periods, silts, beach gravels, clays, and muds of marine and estuarine origin were deposited due to higher sea levels, suggesting similar marine or estuary conditions to those experienced today.

The earliest clear evidence of Lower Palaeolithic archaic human occupation on what is now the Isle of Wight is found close to Priory Bay. More than 300 acheulean handaxes have been recovered from the beach and cliff slopes, originating from a sequence of Pleistocene gravels dating approximately to MIS 11-MIS 9 (424,000–374,000 years ago). Reworked and abraded artefacts found at the site may be considerably older however, closer to 500,000 years old. The identity of the hominids who produced these tools is unknown. However, sites and fossils of the same age range in Europe are often attributed to Homo heidelbergensis or early populations of Neanderthals.

A Middle Palaeolithic Mousterian flint assemblage, consisting of 50 handaxes and debitage, has been recovered from Great Pan Farm in the Medina Valley near Newport. Gravel sequences at the site have been dated to the MIS 3 interstadial during the last glacial period (c. 50,000 years ago). These tools are associated with the late Neanderthal occupation, and evidence of late Neanderthal presence is seen across Britain at this time.

No significant evidence of Upper Palaeolithic activity exists on the Isle of Wight. This period is associated with the expansion and establishment of populations of modern human (Homo sapiens) hunter-gatherers in Europe, beginning around 45,000 years ago. However, evidence of late Upper Palaeolithic activity has been found at nearby sites on the mainland, notably Hengistbury Head in Dorset, dating to just before the onset of the Holocene and the end of the last glacial period c. 11,700 years ago. Evidence of Mesolithic hunter-gatherer occupation on the island is generally found along the river valleys, particularly along the Solent coastline of the island and in the former catchment of the western Yar. Other key terrestrial sites are found at Newtown Creek, Werrar, and Wootton-Quarr.

A submerged escarpment 11 metres below sea level off Bouldnor Cliff on the island's Solent coastline has yielded an internationally significant mesolithic archaeological site. The Bouldnor Cliff site exhibits evidence of seasonal occupation by Mesolithic hunter-gatherers dating to c. 6050 BC. Finds include flint tools, burnt flint, worked timbers, wooden platforms, and pits. The worked wood shows evidence of splitting large planks from oak trunks, interpreted as being intended for use as dug-out canoes. DNA analysis of sediments at the site yielded wheat DNA, not found in Britain until 2,000 years after the occupation at Bouldnor Cliff. It has been suggested this is evidence of wide-reaching trade in Mesolithic Europe; however, the contemporaneity of the wheat with the Mesolithic occupation has been contested. Owing to lower sea levels during the mesolithic the hunter-gatherer site was located on a river bank surrounded by wetlands and woodland. As sea levels rose throughout the early Holocene the Solent flooded, submerging the site.

From c. 6,000 years ago migrations of farming populations to Britain from northwest Europe brought the onset of the Neolithic, largely replacing and assimilating previous mesolithic hunter-gatherer populations. On the Isle of Wight neolithic occupation is attested to by flint tool finds, pottery and monuments. The Isle of Wight's neolithic communities were agriculturalists, farming livestock and crops. The Isle of Wight's most recognisable neolithic site is the Longstone at Mottistone, the remains of an early Neolithic long barrow. Initially constructed with two standing stones at the entrance, only one remains upright today. The site would have likely served as a communal tomb and ritual site for nearby farming communities. A Neolithic mortuary enclosure has also been identified on Tennyson Down near Freshwater.

Bronze Age and Iron Age
From c. 4,400 ago Britain experienced a new wave of migrations from continental Europe, linked to the Bell Beaker Culture. Bell beaker migrants are typically thought to have introduced metal-working to Britain marking the beginning of the Bronze Age. Evidence of early Bronze Age occupation on the Isle of Wight include distinctive bell beaker pots, flint tools, occupation sites and finds of bronze weapons and tools, occurring either individually or in hoard deposits such as the famous Arreton hoard. Highly visible evidence of early Bronze Age activity on the Isle of Wight comes in the form of the barrow monuments present across the island's chalk downland. It is likely these barrows were high-status burial sites, and often occur in 'cemeteries' a notable example being Five Barrows near Brook. Bronze Age Britain had large tin reserves in Cornwall and Devon areas, which was necessary to smelt bronze. At that time, the sea level was much lower, and carts of tin were brought across the Solent at low tide for export, possibly on the Ferriby Boats. Anthony Snodgrass suggests that a shortage of tin, as a part of the Bronze Age Collapse and trade disruptions in the Mediterranean around 1300 BC, forced metalworkers to seek an alternative to bronze.

From the 7th century BC, during the Late Iron Age, the Isle of Wight, like the rest of Great Britain, was occupied by the Celtic Britons, in the form of the Durotriges tribe, as attested by finds of their coins, for example, the South Wight Hoard, and the Shalfleet Hoard. The island was known as Ynys Weith in Brittonic Celtic. Southeastern Britain experienced significant immigration, which is reflected in the current residents' genetic makeup. As the Iron Age began, tin value likely dropped sharply, greatly changing the Isle of Wight's economy. Trade, however, continued, as evidenced by the local abundance of European Iron Age coins.

Roman period
Julius Caesar reported that the Belgae took the Isle of Wight in about 85 BC and recognised the culture of this general region as "Belgic" but made no reference to Vectis. The Roman historian Suetonius mentions that the island was captured by the commander Vespasian. The Romans built no towns on the island, but the remains of at least seven Roman villas have been found, indicating the prosperity of local agriculture. First-century exports were principally hides, enslaved people, hunting dogs, grain, cattle, silver, gold, and iron.

Early medieval period
There are indications that the island had vast trading links, with a port at Bouldnor,  evidence of Bronze Age tin trading, and finds of Late Iron Age coins. Starting in AD 449, the 5th and 6th centuries saw groups of Germanic-speaking peoples from Northern Europe crossing the English Channel and gradually set about conquering the region.

During the Early Middle Ages, the island was settled by Jutes as the pagan kingdom of the Wihtwara under King Arwald. In 685, it was invaded by King Cædwalla of Wessex, who tried to replace the inhabitants with his followers. Though in 686, Arwald was defeated, and the island became the last part of English lands to be converted to Christianity, Cædwalla was unsuccessful in driving the Jutes from the island. Wight was added to Wessex and became part of England under King Alfred the Great, including within the shire of Hampshire.

It suffered especially from Viking raids and was often used as a winter base by Viking raiders when they could not reach Normandy. Later, both Earl Tostig and his brother Harold Godwinson (who became King Harold II) held manors on the island.

Norman Conquest to 18th century

The Norman Conquest of 1066 created the position of Lord of the Isle of Wight; the island was given by William the Conqueror to his kinsman William FitzOsbern. Carisbrooke Priory and the fort of Carisbrooke Castle were then founded. Allegiance was sworn to FitzOsbern rather than the king; the Lordship was subsequently granted to the de Redvers family by Henry I after his succession in 1100.

For nearly 200 years the island was a semi-independent feudal fiefdom, with the de Redvers family ruling from Carisbrooke. The final private owner was the Countess Isabella de Fortibus, who, on her deathbed in 1293, was persuaded to sell it to Edward I. Subsequently, the island was under the control of the English Crown and its Lordship a royal appointment.

The island continued to be attacked from the continent: it was raided in 1374 by the fleet of Castile and in 1377 by French raiders who burned several towns, including Newtown.

Under Henry VIII, who developed the Royal Navy and its Portsmouth base, the island was fortified at Yarmouth, Cowes, East Cowes, and Sandown.

The French invasion on 21 July 1545 (famous for the sinking of the Mary Rose on the 19th) was repulsed by local militia.

During the English Civil War, King Charles I fled to the Isle of Wight, believing he would receive sympathy from Governor Robert Hammond. Still, Hammond imprisoned the king in Carisbrooke Castle.

During the Seven Years' War, the island was a staging post for British troops departing on expeditions against the French coast, such as the Raid on Rochefort. During 1759, with a planned French invasion imminent, a large force of soldiers was stationed there. The French called off their invasion following the Battle of Quiberon Bay.

19th century
In the spring of 1817, the twenty-one year old John Keats spent time in Carisbrooke and Shanklin, where he found inspiration in the countryside and coast, and worked on his long poem Endymion.

In the mid-1840s, potato blight was first found in the UK on the island, having arrived from Belgium. It was later transmitted to Ireland.

In the 1860s, what remains in real terms the most expensive ever government spending project saw fortifications built on the island and in the Solent, as well as elsewhere along the south coast, including the Palmerston Forts, The Needles Batteries, and Fort Victoria, because of fears about possible French invasion.

The future Queen Victoria spent childhood holidays on the island and became fond of it. When she became queen, she made Osborne House her winter home. Subsequently, the island became a fashionable holiday resort for many, including Alfred, Lord Tennyson, Julia Margaret Cameron, and Charles Dickens (who wrote much of David Copperfield there), as well as the French painter Berthe Morisot and members of European royalty.

Until the queen's example, the island had been rural, with most people employed in farming, fishing, or boat-building. The boom in tourism, spurred by growing wealth and leisure time and by Victoria's presence, led to the significant urban development of the island's coastal resorts. As one report summarises, "The Queen's regular presence on the island helped put the Isle of Wight 'on the map' as a Victorian holiday and wellness destination ... and her former residence Osborne House is now one of the most visited attractions on the island." While on the island, the queen used a bathing machine that could be wheeled into the water on Osborne Beach; inside the small wooden hut, she could undress and then bathe, without being visible to others. Her machine had a changing room and a WC with plumbing. The refurbished machine is now displayed at the beach.

On 14 January 1878, Alexander Graham Bell demonstrated an early version of the telephone to the queen, placing calls to Cowes, Southampton, and London. These were the first publicly-witnessed long-distance telephone calls in the UK. The queen tried the device and considered the process to be "quite extraordinary" although the sound was "rather faint". She later asked to buy the equipment that was used, but Bell offered to make "a set of telephones" specifically for her.

The world's first radio station was set up by Guglielmo Marconi in 1897, during her reign, at the Needles Battery, at the western tip of the island. A 168 ft high mast was erected near the Royal Needles Hotel as part of an experiment on communicating with ships at sea. That location is now the site of the Marconi Monument. In 1898 the first paid wireless telegram (called a "Marconigram") was sent from this station, and the island was for some time the home of the National Wireless Museum near Ryde.

Queen Victoria died at Osborne House on 22 January 1901 at 81.

20th century and later
During the Second World War, the island was frequently bombed. With its proximity to German-occupied France, the island hosted observation stations, transmitters, and the RAF radar station at Ventnor. Adolf Hitler personally suggested an invasion of the Isle of Wight as a supplementary operation for Operation Sealion, and the possibility of an invasion was incorporated into Fuhrer Directive 16. Field Marshal Alan Brooke, in charge of defending the UK during 1940, was sceptical about being able to hold the island in the face of an invasion, instead considering that British forces would retreat to the western side of the island rather than commit forces against what might be a diversionary landing. In the end no invasion of the island was carried out as German naval commanders feared any invasion force might be cut off by British naval forces, particularly Royal Navy submarines.

The island was the starting point for one of the earlier Operation Pluto pipelines to feed fuel to Europe after the Normandy landings.

The Needles Battery was used to develop and test the Black Arrow and Black Knight space rockets, which were subsequently launched from Woomera, Australia.

The Isle of Wight Festival was a large rock festival near Afton Down, West Wight, in August 1970, following two smaller concerts in 1968 and 1969. The 1970 show was one of the last public performances by Jimi Hendrix and attracted somewhere between 600,000 and 700,000 attendees. The festival was revived in 2002 in a different format and is now an annual event.

On 26 October 2020, an oil tanker, the Nave Andromeda, suspected to have been hijacked by Nigerian stowaways, was stormed southeast of the island by the Special Boat Service. Seven people believed to be Nigerians seeking UK asylum were handed over to Hampshire Police.

Governance
The island had a single Member of Parliament until 2024. The Isle of Wight constituency covered the entire island, with 138,300 permanent residents in 2011, being one of the most populated constituencies in the United Kingdom (more than 50% above the English average). In 2011 following passage of the Parliamentary Voting System and Constituencies Act, the Sixth Periodic Review of Westminster constituencies was to have changed this, but this was deferred to no earlier than October 2022 by the Electoral Registration and Administration Act 2013. Thus the single constituency remained for the 2015, 2017 and 2019 general elections. However, two separate constituencies, Isle of Wight East and Isle of Wight West were created for the island under the 2022 review, and were first contested in the 2024 general election.

The Isle of Wight is a ceremonial and non-metropolitan county. Since the abolition of its two borough councils and restructuring of the Isle of Wight County Council into the new Isle of Wight Council in 1995, it has been administered by a single tier Island Council which has the same powers as a unitary authority in England.

Elections in the constituency have traditionally been a battle between the Conservatives and the Liberal Democrats. Andrew Turner of the Conservative Party gained the seat from Peter Brand of the Lib Dems at the 2001 general election. Since 2009, Turner was embroiled in controversy over his expenses, health, and relationships with colleagues, with local Conservatives having tried but failed to remove him in the runup to the 2015 general election. He stood down prior to the 2017 snap general election, and the new Conservative Party candidate Bob Seely was elected with a majority of 21,069 votes.

At the Isle of Wight Council election of 2013, the Conservatives lost the majority which they had held since 2005 to the Island Independents, with Island Independent councillors holding 16 of the 40 seats, and a further five councillors sitting as independents outside the group. The Conservatives regained control, winning 10 more seats and taking their total to 25 at the 2017 local election, before losing 7 seats in 2021. A coalition entitled the Alliance Coalition was formed between independent, Green Party and Our Island councillors, with independent councillor Lora Peacey-Wilcox leading the council since May 2021.

There have been small regionalist movements: the Vectis National Party and the Isle of Wight Party; but they have attracted little support at elections.

Geography and environment
The Isle of Wight is situated between the Solent and the English Channel, is roughly rhomboid in shape, and covers an area of 380 km2. Slightly more than half, mainly in the west, is designated as the Isle of Wight Area of Outstanding Natural Beauty. The island has 258 km2 of farmland, 52 km2 of developed areas, and 57 mi of coastline. Its landscapes are diverse, leading to its oft-quoted description as "England in miniature". In June 2019 the whole island was designated a UNESCO Biosphere Reserve, recognising the sustainable relationships between its residents and the local environment.

West Wight is predominantly rural, with dramatic coastlines dominated by the chalk downland ridge, running across the whole island and ending in the Needles stacks. The southwestern quarter is commonly referred to as the Back of the Wight, and has a unique character. The highest point on the island is St Boniface Down in the south east, which at 241 m is a marilyn. The most notable habitats on the rest of the island are probably the soft cliffs and sea ledges, which are scenic features, important for wildlife, and internationally protected.

The island has three principal rivers. The River Medina flows north into the Solent, the Eastern Yar flows roughly northeast to Bembridge Harbour, and the Western Yar flows the short distance from Freshwater Bay to a relatively large estuary at Yarmouth. Without human intervention the sea might well have split the island into three: at the west end where a bank of pebbles separates Freshwater Bay from the marshy backwaters of the Western Yar east of Freshwater, and at the east end where a thin strip of land separates Sandown Bay from the marshy Eastern Yar basin.

The Undercliff between St Catherine's Point and Bonchurch is the largest area of landslip morphology in western Europe.

The north coast is unusual in having four high tides each day, with a double high tide every twelve and a half hours. This arises because the western Solent is narrower than the eastern; the initial tide of water flowing from the west starts to ebb before the stronger flow around the south of the island returns through the eastern Solent to create a second high water.

Geology
The Isle of Wight is made up of a variety of rock types dating from early Cretaceous (around 127 million years ago) to the middle of the Palaeogene (around 30 million years ago). The geological structure is dominated by a large monocline which causes a marked change in age of strata from the northern younger Tertiary beds to the older Cretaceous beds of the south. This gives rise to a dip of almost 90 degrees in the chalk beds, seen best at the Needles.

The northern half of the island is mainly composed of clays, with the southern half formed of the chalk of the central east–west downs, as well as Upper and Lower Greensands and Wealden strata. These strata continue west from the island across the Solent into Dorset, forming the basin of Poole Harbour (Tertiary) and the Isle of Purbeck (Cretaceous) respectively. The chalky ridges of Wight and Purbeck were a single formation before they were breached by waters from the River Frome during the last ice age, forming the Solent and turning Wight into an island. The Needles, along with Old Harry Rocks on Purbeck, represent the edges of this breach.

All the rocks found on the island are sedimentary, such as limestones, mudstones and sandstones. They are rich in fossils; many can be seen exposed on beaches as the cliffs erode. Lignitic coal is present in small quantities within seams, and can be seen on the cliffs and shore at Whitecliff Bay. Fossilised molluscs have been found there, and also on the northern coast along with fossilised crocodiles, turtles and mammal bones; the youngest date back to around 30 million years ago.

The island is one of the most important areas in Europe for dinosaur fossils. The eroding cliffs often reveal previously hidden remains, particularly along the Back of the Wight. Dinosaur bones and fossilised footprints can be seen in and on the rocks exposed around the island's beaches, especially at Yaverland and Compton Bay, from the strata of the Wessex Formation. As a result, the island has been nicknamed "Dinosaur Island" and Dinosaur Isle was established in 2001.

The area was affected by sea level changes during the repeated Quaternary glaciations. The island probably became separated from the mainland about 125,000 years ago, during the Ipswichian interglacial.

Climate
Like the rest of the UK, the island has an oceanic climate, but is somewhat milder and sunnier, which makes it a holiday destination. It also has a longer growing season. Lower Ventnor and the neighbouring Undercliff have a particular microclimate, because of their sheltered position south of the downs. The island enjoys 1,800–2,100 hours of sunshine a year. Some years have almost no snow in winter, and only a few days of hard frost. The island is in Hardiness zone 9.

Flora and Fauna
The Isle of Wight is one of the few places in England where the European red squirrel is still flourishing, as no competitive grey squirrels are to be found there. Other mammalian species on the island include the European badger, hedgehog, least weasel, red fox and stoat, with the hedgehogs proving to be quite popular amongst locals and visitors alike; in 2019, a rescue and rehabilitation group was organised to assist them, called Save Our Hedgehogs Isle of Wight. The Isle is also home to several protected species, such as the European dormouse and several rare bats, including the western barbastelle.

There are several species of deer on the island, both endemic and non-native, all of which are monitored and surveyed annually by the organisation Isle of Wight Deer Conservation. According to the British Deer Society (BDS), the Isle of Wight Biodiversity Group would like to see the island's ecosystems and flora preserved, one method being to keep the island "deer-free"; however, of the five types of deer documented, the European red deer and roe deer are truly native species, having been known to swim to the island from the mainland.

The diminutive Chinese Reeve's muntjac or barking deer—so-called due to its signature dog-like "bark" when threatened—is one of the smallest deer species on earth and is present on the island. The Asian sika (the second-largest species on the island) and Eurasian fallow deer also will journey to the island from the mainland, generally seen in very small herds, in pairs, or alone. Ultimately, all five of the deer species seen on the Isle of Wight are adept swimmers, thus any that are observed may or may not be long-term Island residents. Nonetheless, the island deer (that are present at any given time) tend to remain strategically hidden and are generally thought of as being difficult to spot, even on such a small island. Besides deer, there exists a colony of feral goats on Ventnor's downs.

The Glanville fritillary, a species of butterfly, has a distribution in the United Kingdom largely restricted to the edges of the island's crumbling cliffs.

A competition in 2002 named the pyramidal orchid as the Isle of Wight's county flower.

The occurrence of species and habitats of conservation importance in the island's waters has led to the designation of a suite of marine protected areas seeking to protect these features, including marine conservation zones (MCZ's) and special areas of conservation (SAC's). The island's marine environment also forms a component of its UNESCO Biosphere Reserve, and is part of the Western English Channel Important Marine Mammal Area (IMMA).

Settlements

 * Newport is the centrally located county town, with a population of about 25,000 and the island's main shopping area. Located next to the River Medina, Newport Quay was a busy port until the mid-19th century.
 * Ryde, the largest town with a population of about 30,000, is in the northeast. It is Victorian with the oldest seaside pier in England and miles of sandy and pebble beaches.
 * Cowes hosts the annual Cowes Week and is an international sailing centre.
 * East Cowes is famous for Osborne House, Norris Castle and as the home from 1929 to 1964 of Saunders-Roe, the historic aircraft, flying boat, rocket and hovercraft company.
 * Sandown is a popular seaside resort. It is home to the Wildheart Animal Sanctuary, formerly the Isle of Wight Zoo, the Dinosaur Isle geological museum and one of the island's two 18-hole golf courses.
 * Shanklin, just south of Sandown, attracts tourists with its high summer sunshine levels, sandy beaches, Shanklin Chine and the old village.
 * Ventnor, built on the steep slopes of St Boniface Down on the south coast of the island, leads down to a bay that attracts many tourists. Ventnor Haven is a small harbour.

Socio-economic data
The table below shows the regional gross value (in millions of pounds) added by the Isle of Wight economy, at current prices, compiled by the Office for National Statistics.

According to the 2011 census, the island's population of 138,625 lives in 61,085 households, giving an average household size of 2.27 people.

41% of households own their home outright and a further 29% own with a mortgage, so in total 70% of households are owned (compared to 68% for South East England).

Compared to South East England, the island has fewer children (19% aged 0–17 compared to 22% for the South East) and more elderly (24% aged 65+ compared to 16% for the South East), giving an average age of 44 years for an island resident compared to 40 in South East England.

Industry and agriculture
The largest industry on the island is tourism, but it also has a significant agriculture including sheep, dairy farming and arable crops. Traditional agricultural commodities are more difficult to market off the island because of transport costs, but local farmers have succeeded in exploiting some specialist markets, with the higher price of such products absorbing the transport costs. One of the most successful agricultural sectors is now the growing of crops under cover, particularly salad crops including tomatoes and cucumbers. The island has a warmer climate and a longer growing season than much of the United Kingdom. Garlic has been grown in Newchurch for many years, and is, in part, exported to France. This has led to the establishment of an annual Garlic Festival at Newchurch, which is one of the largest events of the local calendar.

A favourable climate supports two vineyards, including one of the oldest in the British Isles at Adgestone. Lavender is grown for its oil. The largest agricultural sector has been dairying, but due to low milk prices and strict legislation for UK milk producers, the dairy industry has been in decline: there were nearly 150 producers in the mid-1980s, but now just 24.

Maritime industries, especially the making of sailcloth and boat building, have long been associated with the island, although this has diminished in recent years. GKN operates what began as the British Hovercraft Corporation, a subsidiary of (and known latterly as) Westland Aircraft, although they have reduced the extent of plant and workforce and sold the main site. Previously it had been the independent company Saunders-Roe, one of the island's most notable historic firms that produced many flying boats and the world's first hovercraft.

Another manufacturing activity is in composite materials, used by boat-builders and the wind turbine manufacturer Vestas, which has a wind turbine blade factory and testing facilities in West Medina Mills and East Cowes.

Bembridge Airfield is the home of Britten-Norman, manufacturers of the Islander and Trislander aircraft. This is shortly to become the site of the European assembly line for Cirrus light aircraft. The Norman Aeroplane Company is a smaller aircraft manufacturing company operating in Sandown. There have been three other firms that built planes on the island.

In 2005, Northern Petroleum began exploratory drilling for oil at its Sandhills-2 borehole at Porchfield, but ceased operations in October that year after failing to find significant reserves.

Breweries
There are three breweries on the island. Goddards Brewery in Ryde opened in 1993. David Yates, who was head brewer of the Island Brewery, started brewing as Yates Brewery at the Inn at St Lawrence in 2000. Ventnor Brewery, which closed in 2009, was the last incarnation of Burt's Brewery, brewing since the 1840s in Ventnor. Until the 1960s most pubs were owned by Mews Brewery, situated in Newport near the old railway station, but it closed and the pubs were taken over by Strong's, and then by Whitbread. By some accounts Mews beer was apt to be rather cloudy and dark. In the 19th century they pioneered the use of screw top cans for export to British India.

Tourism and heritage
The island's heritage is a major asset that has for many years supported its tourist economy. Holidays focused on natural heritage, including wildlife and geology, are becoming an alternative to the traditional British seaside holiday, which went into decline in the second half of the 20th century due to the increased affordability of foreign holidays. The island is still an important destination for coach tours from other parts of the United Kingdom.

Tourism is still the largest industry, and most island towns and villages offer hotels, hostels and camping sites. In 1999, it hosted 2.7 million visitors, with 1.5 million staying overnight, and 1.2 million day visits; only 150,000 of these were from abroad. Between 1993 and 2000, visits increased at an average rate of 3% per year.

At the turn of the 19th century the island had ten pleasure piers, including two at Ryde and a "chain pier" at Seaview. The Victoria Pier in Cowes succeeded the earlier Royal Pier but was itself removed in 1960. The piers at Ryde, Seaview, Sandown, Shanklin and Ventnor originally served a coastal steamer service that operated from Southsea on the mainland. The piers at Seaview, Shanklin, Ventnor and Alum Bay were all destroyed by various storms during the 20th century; only the railway pier at Ryde and the piers at Sandown, Totland Bay (currently closed to the public) and Yarmouth survive.

Blackgang Chine is the oldest theme park in Britain, opened in 1843. The skeleton of a dead whale that its founder Alexander Dabell found in 1844 is still on display.

As well as its more traditional attractions, the island is often host to walking or cycling holidays through the attractive scenery. An annual walking festival has attracted considerable interest. The 70 mi Isle of Wight Coastal Path follows the coastline as far as possible, deviating onto roads where the route along the coast is impassable.

The tourist board for the island is Visit Isle of Wight, a non-profit company. It is the Destination Management Organisation for the Isle of Wight, a public and private sector partnership led by the private sector, and consists of over 1,200 companies, including the ferry operators, the local bus company, rail operator and tourism providers working together to collectively promote the island. Its income is derived from the Wight BID, a business improvement district levy fund.

A major contributor to the local economy is sailing and marine-related tourism.

Summer Camp at Camp Beaumont is an attraction at the old Bembridge School site.

Media
The main local newspaper used to be the Isle of Wight County Press, but its circulation has declined over the years, especially since it was taken over by Newsquest in July 2017. In 2018 a new free newspaper was launched, the Isle of Wight Observer. By 2023 the newcomer was distributing 18,500 copies compared to the Isle of Wight County Press's total circulation of 11,575].

On-line news websites include Island Echo, launched in May 2012, and On the Wight.

The island has a local commercial radio station and a community radio station: commercial station Isle of Wight Radio has broadcast in the medium-wave band since 1990 and on 107.0 MHz (with three smaller transmitters on 102.0 MHz) FM since 1998, as well as streaming on the Internet. Community station Vectis Radio has broadcast online since 2010, and in 2017 started broadcasting on FM 104.6. The station operates from the Riverside Centre in Newport. The island is also covered by a number of local stations on the mainland, including the BBC station BBC Radio Solent broadcast from Southampton. The island's not-for-profit community radio station Angel Radio opened in 2007. Angel Radio began broadcasting on 91.5 MHz from studios in Cowes and a transmitter near Newport.

Important broadcasting infrastructure includes Chillerton Down transmitting station with a mast that is the tallest structure on the island, and Rowridge transmitting station, which broadcasts the main television signal both locally and for most of Hampshire and parts of Dorset and West Sussex.

Language and dialect

The local accent is similar to the traditional dialect of Hampshire, featuring the dropping of some consonants and an emphasis on longer vowels. It is similar to the West Country dialects heard in South West England, but less pronounced.

The island has its own local and regional words. Some, such as nipper/nips (a young male person), are still sometimes used and shared with neighbouring areas of the mainland. A few are unique to the island, for example overner and caulkhead (see below). Others are more obscure and now used mainly for comic emphasis, such as mallishag (meaning "caterpillar"), gurt meaning "large", nammit (a mid-morning snack) and gallybagger ("scarecrow", and now the name of a local cheese).

Identity
There remains occasional confusion between the Isle of Wight as a county and its former position within Hampshire. The island was regarded and administered as a part of Hampshire until 1890, when its distinct identity was recognised with the formation of Isle of Wight County Council (see also Politics of the Isle of Wight). However, it remained a part of Hampshire until the local government reforms of 1974, when it became a full ceremonial county with its own Lord Lieutenant.

In January 2009, the first general flag for the county was accepted by the Flag Institute.

Island residents are sometimes referred to as "Vectensians", "Vectians" or, if born on the island, "caulkheads". One theory is that this last comes from the once prevalent local industry of caulking or sealing wooden boats; the term became attached to islanders either because they were so employed, or as a derisory term for perceived unintelligent labourers from elsewhere. The term "overner" is used for island residents originating from the mainland (an abbreviated form of "overlander", which is an archaic term for "outsider" still found in parts of Australia).

Residents refer to the island as "The Island", as did Jane Austen in Mansfield Park, and sometimes to the UK mainland as "North Island".

To promote the island's identity and culture, the High Sheriff, Robin Courage, founded an Isle of Wight Day; the first was held on 24 September 2016.

Sport
Sport plays a key part of culture on the Isle of Wight. Sports include golf, marathon, cycling and sailing.

Music

The island is home to the Isle of Wight Festival and until 2016, Bestival, before it was relocated to Lulworth Estate in Dorset. In 1970, the festival was headlined by Jimi Hendrix attracting an audience of 600,000, some six times the local population at the time. It is the home of the bands The Bees, Trixie's Big Red Motorbike, Level 42, and Wet Leg.

Landmarks
• Alum Bay

• Appuldurcombe House EH icon.svg

• Amazon World Zoo Zoo icon.jpg

• Bembridge Lifeboat Station

• Blackgang Chine Themepark uk icon.png

• Brading Roman Villa Museum icon (red).png

• Carisbrooke Castle EH icon.svg CL icon.svg

• Classic Boat Museum, East Cowes Museum icon (red).png

• Compton Bay

• Dimbola Lodge Museum icon (red).png

• Dinosaur Isle Museum icon (red).png

• Fort Victoria CP icon.png

• Godshill village and model village

• Isle of Wight Bus & Coach Museum Museum icon (red).png

• Isle of Wight Steam Railway HR icon.svg

• Isle of Wight Zoo, Yaverland Zoo icon.jpg

• Medina Theatre

• The Needles NTE icon.png

• Newport Roman Villa

• Osborne House EH icon.svg

• Quarr Abbey AP Icon.svg

• Robin Hill CP icon.png

• Botanic Gardens, Ventnor

• Yarmouth Castle EH icon.svg CL icon.svg

Transport
The Isle of Wight has 489 mi of roadway. It does not have a motorway, although there is a short stretch of dual carriageway towards the north of Newport near the hospital and prison.

A comprehensive bus network operated by Southern Vectis links most settlements, with Newport as its central hub.

Journeys away from the island involve a ferry journey. Car ferry and passenger catamaran services are run by Wightlink and Red Funnel, and a hovercraft passenger service (the only such remaining in the world) by Hovertravel.

The island formerly had its own railway network of over 55 mi, but only one line remains in regular use. The Island Line is part of the United Kingdom's National Rail network, running a little under 9 mi from Shanklin to Ryde Pier Head, where there is a connecting ferry service to Portsmouth Harbour station on the mainland network. The line was opened by the Isle of Wight Railway in 1864, and from 1996 to 2007 was run by the smallest train operating company on the network, Island Line Trains. It is notable for utilising old ex-London Underground rolling stock, due to the small size of its tunnels and unmodernised signalling. Branching off the Island Line at Smallbrook Junction is the heritage Isle of Wight Steam Railway, which runs for 5+1/2 mi to the outskirts of Wootton on the former line to Newport.

There are two airfields for general aviation, Isle of Wight Airport at Sandown and Bembridge Airport.

The island has over 200 mi of cycleways, many of which can be enjoyed off-road. The principal trails are:
 * The Sunshine Trail, which is a circular route linking Sandown, Shanklin, Godshill, and Wroxall of 12 mi;
 * The Red Squirrel Trail, a track between Cowes and Sandown that is 32 mi in total;
 * The Round the Island Cycle Route of 62 mi.

Prisons
The Isle of Wight is near the densely populated south of England, yet separated from the mainland. This position led to it hosting three prisons: Albany, Camp Hill and Parkhurst, all located outside Newport near the main road to Cowes. Albany and Parkhurst were among the few Category A prisons in the UK until they were downgraded in the 1990s. The downgrading of Parkhurst was precipitated by a major escape: three prisoners (two murderers and a blackmailer) escaped from the prison on 3 January 1995 for four days, before being recaptured. Parkhurst enjoyed notoriety as one of the toughest jails in the United Kingdom, and housed many notable inmates including the Yorkshire Ripper Peter Sutcliffe, New Zealand drug lord Terry Clark and the Kray twins.

Camp Hill is located adjacent but to the west of Albany and Parkhurst, on the very edge of Parkhurst Forest, having been converted first to a borstal and later to a Category C prison. It was built on the site of an army camp (both Albany and Parkhurst were barracks); there is a small estate of tree-lined roads with the former officers' quarters (now privately owned) to the south and east. Camp Hill closed as a prison in March 2013.

The management of all three prisons was merged into a single administration, under HMP Isle of Wight in April 2009.

Education
There are 69 local education authority-maintained schools on the Isle of Wight, and two independent schools. As a rural community, many of these are small and with fewer pupils than in urban areas. The Isle of Wight College is located on the outskirts of Newport.

From September 2010, there was a transition period from the three-tier system of primary, middle and high schools to the two-tier system that is usual in England. Some schools have now closed, such as Chale C.E. Primary. Others have become "federated", such as Brading C.E. Primary and St Helen's Primary. Christ the King College started as two "middle schools", Trinity Middle School and Archbishop King Catholic Middle School, but has now been converted into a dual-faith secondary school and sixth form.

Since September 2011 five new secondary schools, with an age range of 11 to 18 years, replaced the island's high schools (as a part of the previous three-tier system).

Notable people
Notable residents have included:

17th century and earlier

 * King Arwald, last pagan king in England
 * King Charles I of England, who was imprisoned at Carisbrooke Castle
 * Earl Tostig Godwinson, who supported Norwegian king Harald Hardrada's invasion
 * Actor, highwayman and conspirator Cardell "Scum" Goodman
 * Soldier and regicide of Charles I Thomas Harrison, imprisoned at Carisbrooke with John Rogers and Christopher Feake
 * Soldier Peter de Heyno
 * Philosopher and polymath Robert Hooke
 * Murderer Michal Morey

18th century

 * Marine painter Thomas Buttersworth
 * Explorer Anthony Henday
 * Radical journalist John Wilkes

19th century

 * Queen Victoria and Prince Albert (monarch and consort), who built and lived at Osborne House
 * Photographer Julia Margaret Cameron, who lived at Dimbola Lodge
 * Irish Republican Thomas Clarke
 * Naval captain Jeremiah Coghlan, who retired to Ryde
 * Writer Charles Dickens
 * Novelist Gertrude Fenton
 * Poet John Keats
 * Inventor and radio pioneer Guglielmo Marconi
 * Philosopher Karl Marx, who stayed at 1, St. Boniface Gardens, Ventnor
 * Religious writer and hymnwriter Mary Fawler Maude
 * Poet and hymnwriter Albert Midlane
 * Geologist and engineer John Milne
 * Regency architect John Nash
 * Novelist Harriet Parr
 * Early Hong Kong Government administrator William Pedder
 * New Zealand PM Henry Sewell
 * Poet Algernon Charles Swinburne
 * Poet Alfred Tennyson

20th century onwards

 * Scriptwriter Raymond Allen
 * Concert organist E. Power Biggs
 * Darts player Keegan Brown
 * Singer Helen Clare
 * Singer-songwriter Sarah Close
 * Inventor of the hovercraft Sir Christopher Cockerell
 * Presenter and actor Ray Cokes
 * Actress Bella Emberg
 * Yachtsman Uffa Fox
 * Actor Marius Goring
 * Musician Jack Green
 * Survival expert and Chief Scout Bear Grylls
 * Actress Sheila Hancock
 * Actor Melvyn Hayes
 * Singer-songwriter Lauran Hibberd
 * Folk-rock musician Robyn Hitchcock
 * Actor Geoffrey Hughes
 * Conspiracy theorist David Icke
 * Actor Jeremy Irons
 * Comedian Phill Jupitus
 * Actor Laura Michelle Kelly
 * Composer Albert Ketèlbey
 * Iranian poet Mimi Khalvati
 * Musician Mark King
 * Band Level 42
 * Yachtswoman Ellen MacArthur
 * BBC Tonight presenter Cliff Michelmore
 * Film director Anthony Minghella
 * Actor David Niven
 * YouTuber Adam Pacitti
 * Cyclist Kieran Page
 * Professor of biochemistry Samuel Victor Perry
 * Musician Frederick Riddle
 * Performance artist Nigel Rolfe
 * Heptathlete Kelly Sotherton
 * Gardener and presenter Alan Titchmarsh
 * Novelist Edward Upward
 * Band Wet Leg
 * Band Grade 2

Overseas names
The Isle of Wight has given names to many parts of former colonies, most notably Isle of Wight County in Virginia founded by settlers from the island in the 17th century. Its county seat is a town named Isle of Wight.

Other notable examples include:
 * Isle of Wight – an island off Maryland, United States
 * Dunnose Head, West Falkland
 * Ventnor, Cowes on Phillip Island, Victoria, Australia
 * Carisbrook, Victoria, Australia
 * Carisbrook, a former stadium in Dunedin, New Zealand
 * Ryde, New South Wales, Australia
 * Shanklin, Sandown, New Hampshire, United States
 * Ventnor City, New Jersey, United States
 * Gardiners Island, New York, United States shown as "Isle of Wight" on some of the older maps.

Film

 * The film Something to Hide (1972; US title: Shattered), starring Peter Finch, was filmed near Cowes.
 * The British film That'll Be the Day (1973), starring David Essex and Ringo Starr, included scenes shot in Ryde (notably Cross Street), Sandown (school), Shanklin (beach) and Wootton Bridge (fairground).
 * Mrs Brown (1997), with Dame Judi Dench and Billy Connolly, was filmed at Osborne House and Chale.
 * The film Fragile (2005), starring Calista Flockhart, is based on the Isle of Wight.
 * Victoria and Abdul (2017) starring Dame Judi Dench and Ali Fazal, began shooting principal photography at Osborne House in September 2016.

Games

 * John Worsley's Commodore 64 game Spirit of the Stones was set on the Isle of Wight.

Music

 * The Beatles' song "When I'm Sixty-Four" (1967), credited to Lennon-McCartney and sung by Paul McCartney, refers to renting a cottage on the island.

Television

 * Survivors, the BBC's 1970s post-apocalyptic sci-fi drama set after a worldwide pandemic kills off most of humanity, features an episode in which 500 survivors holed up in London are to be relocated to the Isle of Wight. Though referred to many times in the Series 2 episode "Lights of London – Part 2", the move itself is not shown (nor any footage of the island).
 * ITV's dramatisation of Dennis Potter's work Blade on the Feather (19 October 1980) was filmed on the island.
 * A 2002 Top Gear feature showed an Aston Martin being driven around Cowes, East Cowes, and along the Military Road and seawall at Freshwater Bay.
 * The setting for Free Rein was based on the Isle of Wight.
 * Portions of the 2021 drama series It's a Sin on Channel 4 were supposedly set in the Isle of Wight, the home of one of the lead characters, although they were actually filmed in Rhos-on-Sea and Bangor in north Wales.
 * The sitcom The Cockfields is set on the Isle of Wight.

Novels
Julian Barnes' novel England, England broaches the idea of replicating England in a theme park on the Isle of Wight.

Books

title: Isle of Wight


text:
Internet Control Message Protocol

The Internet Control Message Protocol (ICMP) is a supporting protocol in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational information indicating success or failure when communicating with another IP address. For example, an error is indicated when a requested service is not available or that a host or router could not be reached. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications (with the exception of some diagnostic tools like ping and traceroute).

ICMP for IPv4 is defined in. A separate ICMPv6, defined by RFC 4443, is used with IPv6.

Technical details
ICMP is part of the Internet protocol suite as defined in RFC 792. ICMP messages are typically used for diagnostic or control purposes or generated in response to errors in IP operations (as specified in RFC 1122). ICMP errors are directed to the source IP address of the originating packet.

For example, every device (such as an intermediate router) forwarding an IP datagram first decrements the time to live (TTL) field in the IP header by one. If the resulting TTL is 0, the packet is discarded and an ICMP time exceeded message is sent to the datagram's source address.

Many commonly used network utilities are based on ICMP messages. The traceroute command can be implemented by transmitting IP datagrams with specially set IP TTL header fields, and looking for ICMP time exceeded in transit and destination unreachable messages generated in response. The related ping utility is implemented using the ICMP echo request and echo reply messages.

ICMP uses the basic support of IP as if it were a higher-level protocol, however, ICMP is actually an integral part of IP. Although ICMP messages are contained within standard IP packets, ICMP messages are usually processed as a special case, distinguished from normal IP processing. In many cases, it is necessary to inspect the contents of the ICMP message and deliver the appropriate error message to the application responsible for transmitting the IP packet that prompted the ICMP message to be sent.

ICMP is a network-layer protocol; this makes it a layer 3 protocol in the seven-layer OSI model. Based on the four-layer TCP/IP model, ICMP is an internet-layer protocol, which makes it a layer 2 protocol in the Internet Standard RFC 1122 TCP/IP four-layer model or a layer 3 protocol in the modern five-layer TCP/IP protocol definitions (by Kozierok, Comer, Tanenbaum, Forouzan, Kurose, Stallings).

There is no TCP or UDP port number associated with ICMP packets as these numbers are associated with the transport layer above.

Datagram structure
The ICMP packet is encapsulated in an IPv4 packet. The packet consists of header and data sections.

Header
The ICMP header starts after the IPv4 header and is identified by its protocol number, 1. All ICMP packets have an eight-byte header and variable-sized data section. The first four bytes of the header have fixed format, while the last four bytes depend on the type and code of the ICMP packet.

 * Type : ICMP type, see.
 * Code : ICMP subtype, see.
 * Checksum : Internet checksum (RFC 1071) for error checking, calculated from the ICMP header and data with value 0 substituted for this field.
 * Rest of header : Four-byte field, contents vary based on the ICMP type and code.

Data
ICMP error messages contain a data section that includes a copy of the entire IPv4 header, plus at least the first eight bytes of data from the IPv4 packet that caused the error message. The length of ICMP error messages should not exceed 576 bytes. This data is used by the host to match the message to the appropriate process. If a higher level protocol uses port numbers, they are assumed to be in the first eight bytes of the original datagram's data.

The variable size of the ICMP packet data section has been exploited. In the "Ping of death", large or fragmented ICMP packets are used for denial-of-service attacks. ICMP data can also be used to create covert channels for communication. These channels are known as ICMP tunnels.

Control messages
Control messages are identified by the value in the type field. The code field gives additional context information for the message. Some control messages have been deprecated since the protocol was first introduced.

Source quench
Source Quench requests that the sender decrease the rate of messages sent to a router or host. This message may be generated if a router or host does not have sufficient buffer space to process the request, or may occur if the router or host buffer is approaching its limit.

Data is sent at a very high speed from a host or from several hosts at the same time to a particular router on a network. Although a router has buffering capabilities, the buffering is limited to within a specified range. The router cannot queue any more data than the capacity of the limited buffering space. Thus if the queue gets filled up, incoming data is discarded until the queue is no longer full. But as no acknowledgement mechanism is present in the network layer, the client does not know whether the data has reached the destination successfully. Hence some remedial measures should be taken by the network layer to avoid these kind of situations. These measures are referred to as source quench.

In a source quench mechanism, the router sees that the incoming data rate is much faster than the outgoing data rate, and sends an ICMP message to the clients, informing them that they should slow down their data transfer speeds or wait for a certain amount of time before attempting to send more data. When a client receives this message, it automatically slows down the outgoing data rate or waits for a sufficient amount of time, which enables the router to empty the queue. Thus the source quench ICMP message acts as flow control in the network layer.

Since research suggested that "ICMP Source Quench [was] an ineffective (and unfair) antidote for congestion", routers' creation of source quench messages was deprecated in 1995 by RFC 1812. Furthermore, forwarding of and any kind of reaction to (flow control actions) source quench messages was deprecated from 2012 by RFC 6633.

Where:
 * Type must be set to 4
 * Code must be set to 0
 * IP header and additional data is used by the sender to match the reply with the associated request

Redirect

Redirect requests data packets be sent on an alternative route. ICMP Redirect is a mechanism for routers to convey routing information to hosts. The message informs a host to update its routing information (to send packets on an alternative route). If a host tries to send data through a router (R1) and R1 sends the data on another router (R2) and a direct path from the host to R2 is available (that is, the host and R2 are on the same subnetwork), then R1 will send a redirect message to inform the host that the best route for the destination is via R2. The host should then change its route information and send packets for that destination directly to R2. The router will still send the original datagram to the intended destination. However, if the datagram contains routing information, this message will not be sent even if a better route is available. RFC 1122 states that redirects should only be sent by gateways and should not be sent by Internet hosts.

Where:
 * Type must be set to 5.
 * Code specifies the reason for the redirection, and may be one of the following:
 * {| class="wikitable"

! Code ! Description ! 0 ! 1 ! 2 ! 3
 * Redirect for Network
 * Redirect for Host
 * Redirect for Type of Service and Network
 * Redirect for Type of Service and Host
 * }
 * IP address is the 32-bit address of the gateway to which the redirection should be sent.
 * IP header and additional data is included to allow the host to match the reply with the request that caused the redirection reply.

Time exceeded
Time Exceeded is generated by a gateway to inform the source of a discarded datagram due to the time to live field reaching zero. A time exceeded message may also be sent by a host if it fails to reassemble a fragmented datagram within its time limit.

Time exceeded messages are used by the traceroute utility to identify gateways on the path between two hosts.

Where:
 * Type must be set to 11
 * Code specifies the reason for the time exceeded message, include the following:
 * {| class="wikitable"

! Code || Description ! 0 ! 1
 * Time-to-live exceeded in transit.
 * Fragment reassembly time exceeded.
 * }
 * IP header and first 64 bits of the original payload are used by the source host to match the time exceeded message to the discarded datagram. For higher-level protocols such as UDP and TCP the 64-bit payload will include the source and destination ports of the discarded packet.

Timestamp
Timestamp is used for time synchronization. The originating timestamp is set to the time (in milliseconds since midnight) the sender last touched the packet. The receive and transmit timestamps are not used.

Where:
 * Type must be set to 13
 * Code must be set to 0
 * Identifier and Sequence Number can be used by the client to match the timestamp reply with the timestamp request.
 * Originate timestamp is the number of milliseconds since midnight Universal Time (UT). If a UT reference is not available the most-significant bit can be set to indicate a non-standard time value.

Timestamp reply
Timestamp Reply replies to a Timestamp message. It consists of the originating timestamp sent by the sender of the Timestamp as well as a receive timestamp indicating when the Timestamp was received and a transmit timestamp indicating when the Timestamp reply was sent.

Where:
 * Type must be set to 14
 * Code must be set to 0
 * Identifier and Sequence number can be used by the client to match the reply with the request that caused the reply.
 * Originate timestamp is the time the sender last touched the message before sending it.
 * Receive timestamp is the time the echoer first touched it on receipt.
 * Transmit timestamp is the time the echoer last touched the message on sending it.

 * All timestamps are in units of milliseconds since midnight UT. If the time is not available in milliseconds or cannot be provided with respect to midnight UT then any time can be inserted in a timestamp provided the high order bit of the timestamp is also set to indicate this non-standard value.

The use of Timestamp and Timestamp Reply messages to synchronize the clocks of Internet nodes has largely been replaced by the UDP-based Network Time Protocol and the Precision Time Protocol.

Address mask request
Address mask request is normally sent by a host to a router in order to obtain an appropriate subnet mask.

Recipients should reply to this message with an Address mask reply message.

Where:
 * Type must be set to 17
 * Code must be set to 0
 * Address mask can be set to 0

ICMP Address Mask Request may be used as a part of reconnaissance attack to gather information on the target network, therefore ICMP Address Mask Reply is disabled by default on Cisco IOS.

Address mask reply
Address mask reply is used to reply to an address mask request message with an appropriate subnet mask.

Where:
 * Type must be set to 18
 * Code must be set to 0
 * Address mask should be set to the subnet mask

Destination unreachable
Destination unreachable is generated by the host or its inbound gateway to inform the client that the destination is unreachable for some reason. Reasons for this message may include: the physical connection to the host does not exist (distance is infinite); the indicated protocol or port is not active; the data must be fragmented but the 'don't fragment' flag is on. Unreachable TCP ports notably respond with TCP RST rather than a destination unreachable type 3 as might be expected. Destination unreachable is never reported for IP multicast transmissions.

Where:
 * Type field (bits 0–7) must be set to 3
 * Code field (bits 8–15) is used to specify the type of error, and can be any of the following:
 * {| class="wikitable"

! Code || Description ! 0 ! 1 ! 2 ! 3 ! 4 ! 5 ! 6 ! 7 ! 8 ! 9 ! 10 ! 11 ! 12 ! 13 ! 14 ! 15
 * Network unreachable error.
 * Host unreachable error.
 * Protocol unreachable error (the designated transport protocol is not supported).
 * Port unreachable error (the designated protocol is unable to inform the host of the incoming message).
 * The datagram is too big. Packet fragmentation is required but the 'don't fragment' (DF) flag is on.
 * Source route failed error.
 * Destination network unknown error.
 * Destination host unknown error.
 * Source host isolated error.
 * The destination network is administratively prohibited.
 * The destination host is administratively prohibited.
 * The network is unreachable for Type Of Service.
 * The host is unreachable for Type Of Service.
 * Communication administratively prohibited (administrative filtering prevents packet from being forwarded).
 * Host precedence violation (indicates the requested precedence is not permitted for the combination of host or network and port).
 * Precedence cutoff in effect (precedence of datagram is below the level set by the network administrators).
 * }
 * Next-hop MTU field (bits 48–63) contains the MTU of the next-hop network if a code 4 error occurs.
 * IP header and additional data is included to allow the client to match the reply with the request that caused the destination unreachable reply.

RFCs

 * , Internet Control Message Protocol
 * , Internet Standard Subnetting Procedure
 * , Something a Host Could Do with Source Quench: The Source Quench Introduced Delay (SQuID)
 * , Requirements for Internet Hosts – Communication Layers
 * , Towards Requirements for IP Routers
 * , Requirements for IP Version 4 Routers
 * , Extended ICMP to Support Multi-Part Messages

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Internet Control Message Protocol


text:
ICMP

ICMP may refer to:

Science and technology

 * International Collection of Microorganisms from Plants, a culture collection in New Zealand
 * International Congress on Mathematical Physics
 * Internet Control Message Protocol, used in computer networking
 * Ischemic cardiomyopathy, a type of heart disease

Other uses

 * The Institute of Contemporary Music Performance, in London, UK
 * International Commission on Missing Persons, an intergovernmental organization

title: ICMP


text:
Inverse limit

In mathematics, the inverse limit (also called the projective limit) is a construction that allows one to "glue together" several related objects, the precise gluing process being specified by morphisms between the objects. Thus, inverse limits can be defined in any category although their existence depends on the category that is considered. They are a special case of the concept of limit in category theory.

By working in the dual category, that is by reversing the arrows, an inverse limit becomes a direct limit or inductive limit, and a limit becomes a colimit.

Algebraic objects
We start with the definition of an inverse system (or projective system) of groups and homomorphisms. Let $$(I, \leq)$$ be a directed poset (not all authors require I to be directed). Let (Ai)i∈I be a family of groups and suppose we have a family of homomorphisms $$f_{ij}: A_j \to A_i$$ for all $$i \leq j$$ (note the order) with the following properties: Then the pair $$((A_i)_{i\in I}, (f_{ij})_{i\leq j\in I})$$ is called an inverse system of groups and morphisms over $$I$$, and the morphisms $$f_{ij}$$ are called the transition morphisms of the system.
 * 1) $$f_{ii}$$ is the identity on $$A_i$$,
 * 2) $$f_{ik} = f_{ij} \circ f_{jk} \quad \text{for all } i \leq j \leq k.$$

We define the inverse limit of the inverse system $$((A_i)_{i\in I}, (f_{ij})_{i\leq j\in I})$$ as a particular subgroup of the direct product of the $$A_i$$ 's:

 * $$A = \varprojlim_{i\in I}{A_i} = \left\{\left.\vec a \in \prod_{i\in I}A_i \;\right|\; a_i = f_{ij}(a_j) \text{ for all } i \leq j \text{ in } I\right\}.$$

The inverse limit $$A$$ comes equipped with natural projections $\pi_{i}: A → A_{i}$ which pick out the $i$th component of the direct product for each $$i$$ in $$I$$. The inverse limit and the natural projections satisfy a universal property described in the next section.

This same construction may be carried out if the $$A_i$$'s are sets, semigroups, topological spaces, rings, modules (over a fixed ring), algebras (over a fixed ring), etc., and the homomorphisms are morphisms in the corresponding category. The inverse limit will also belong to that category.

General definition
The inverse limit can be defined abstractly in an arbitrary category by means of a universal property. Let $ (X_i, f_{ij})$ be an inverse system of objects and morphisms  in a category C (same definition as above). The inverse limit of this system is an object X in C together with morphisms $\pi$i: X → Xi (called projections) satisfying πi = $$f_{ij}$$ ∘ πj for all i ≤ j. The pair (X, πi) must be universal in the sense that for any other such pair (Y, ψi) there exists a unique morphism u: Y → X such that the diagram

commutes for all i ≤ j. The inverse limit is often denoted
 * $$X = \varprojlim X_i$$

with the inverse system $(X_i, f_{ij})$ being understood.

In some categories, the inverse limit of certain inverse systems does not exist. If it does, however, it is unique in a strong sense: given any two inverse limits X and X' of an inverse system, there exists a unique isomorphism X′ → X commuting with the projection maps.

Inverse systems and inverse limits in a category C admit an alternative description in terms of functors. Any partially ordered set I can be considered as a small category where the morphisms consist of arrows i → j if and only if i ≤ j. An inverse system is then just a contravariant functor I → C. Let $$C^{I^\mathrm{op}}$$ be the category of these functors (with natural transformations as morphisms). An object X of C can be considered a trivial inverse system, where all objects are equal to X and all arrow are the identity of X. This defines a "trivial functor" from C to $$C^{I^\mathrm{op}}.$$ The inverse limit, if it exists, is defined as a right adjoint of this trivial functor.

Examples

 * The ring of p-adic integers is the inverse limit of the rings $$\mathbb{Z}/p^n\mathbb{Z}$$ (see modular arithmetic) with the index set being the natural numbers with the usual order, and the morphisms being "take remainder". That is, one considers sequences of integers $$(n_1, n_2, \dots)$$ such that each element of the sequence "projects" down to the previous ones, namely, that $$n_i\equiv n_j \mbox{ mod } p^{i}$$ whenever $$i<j.$$ The natural topology on the p-adic integers is the one implied here, namely the product topology with cylinder sets as the open sets.
 * The p-adic solenoid is the inverse limit of the topological groups $$\mathbb{R}/p^n\mathbb{Z}$$ with the index set being the natural numbers with the usual order, and the morphisms being "take remainder". That is, one considers sequences of real numbers $$(x_1, x_2, \dots)$$ such that each element of the sequence "projects" down to the previous ones, namely, that $$x_i\equiv x_j \mbox{ mod } p^{i}$$ whenever $$i<j.$$ Its elements are exactly of form $$n + r$$, where $$n$$ is a p-adic integer, and $$r\in [0, 1)$$ is the "remainder".
 * The ring $$\textstyle Rt$$ of formal power series over a commutative ring R can be thought of as the inverse limit of the rings $$\textstyle R[t]/t^nR[t]$$, indexed by the natural numbers as usually ordered, with the morphisms from $$\textstyle R[t]/t^{n+j}R[t]$$ to $$\textstyle R[t]/t^nR[t]$$ given by the natural projection.
 * Pro-finite groups are defined as inverse limits of (discrete) finite groups.
 * Let the index set I of an inverse system (Xi, $$f_{ij}$$) have a greatest element m. Then the natural projection πm: X → Xm is an isomorphism.
 * In the category of sets, every inverse system has an inverse limit, which can be constructed in an elementary manner as a subset of the product of the sets forming the inverse system. The inverse limit of any inverse system of non-empty finite sets is non-empty. This is a generalization of Kőnig's lemma in graph theory and may be proved with Tychonoff's theorem, viewing the finite sets as compact discrete spaces, and then applying the finite intersection property characterization of compactness.
 * In the category of topological spaces, every inverse system has an inverse limit. It is constructed by placing the initial topology on the underlying set-theoretic inverse limit. This is known as the limit topology.
 * The set of infinite strings is the inverse limit of the set of finite strings, and is thus endowed with the limit topology. As the original spaces are discrete, the limit space is totally disconnected. This is one way of realizing the p-adic numbers and the Cantor set (as infinite strings).

Derived functors of the inverse limit
For an abelian category C, the inverse limit functor
 * $$\varprojlim:C^I\rightarrow C$$

is left exact. If I is ordered (not simply partially ordered) and countable, and C is the category Ab of abelian groups, the Mittag-Leffler condition is a condition on the transition morphisms fij that ensures the exactness of $$\varprojlim$$. Specifically, Eilenberg constructed a functor
 * $$\varprojlim{}^1:\operatorname{Ab}^I\rightarrow\operatorname{Ab}$$

(pronounced "lim one") such that if (Ai, fij), (Bi, gij), and (Ci, hij) are three inverse systems of abelian groups, and
 * $$0\rightarrow A_i\rightarrow B_i\rightarrow C_i\rightarrow0$$

is a short exact sequence of inverse systems, then
 * $$0\rightarrow\varprojlim A_i\rightarrow\varprojlim B_i\rightarrow\varprojlim C_i\rightarrow\varprojlim{}^1A_i$$

is an exact sequence in Ab.

Mittag-Leffler condition
If the ranges of the morphisms of an inverse system of abelian groups (Ai, fij) are stationary, that is, for every k there exists j ≥ k such that for all i ≥ j :$$ f_{kj}(A_j)=f_{ki}(A_i)$$ one says that the system satisfies the Mittag-Leffler condition.

The name "Mittag-Leffler" for this condition was given by Bourbaki in their chapter on uniform structures for a similar result about inverse limits of complete Hausdorff uniform spaces. Mittag-Leffler used a similar argument in the proof of Mittag-Leffler's theorem.

The following situations are examples where the Mittag-Leffler condition is satisfied:
 * a system in which the morphisms fij are surjective
 * a system of finite-dimensional vector spaces or finite abelian groups or modules of finite length or Artinian modules.

An example where $$\varprojlim{}^1$$ is non-zero is obtained by taking I to be the non-negative integers, letting Ai = piZ, Bi = Z, and Ci = Bi / Ai = Z/piZ. Then
 * $$\varprojlim{}^1A_i=\mathbf{Z}_p/\mathbf{Z}$$

where Zp denotes the p-adic integers.

Further results
More generally, if C is an arbitrary abelian category that has enough injectives, then so does CI, and the right derived functors of the inverse limit functor can thus be defined. The nth right derived functor is denoted
 * $$R^n\varprojlim:C^I\rightarrow C.$$

In the case where C satisfies Grothendieck's axiom (AB4*), Jan-Erik Roos generalized the functor lim1 on AbI to series of functors limn such that
 * $$\varprojlim{}^n\cong R^n\varprojlim.$$

It was thought for almost 40 years that Roos had proved (in Sur les foncteurs dérivés de lim. Applications.) that lim1 Ai = 0 for (Ai, fij) an inverse system with surjective transition morphisms and I the set of non-negative integers (such inverse systems are often called "Mittag-Leffler sequences"). However, in 2002, Amnon Neeman and Pierre Deligne constructed an example of such a system in a category satisfying (AB4) (in addition to (AB4*)) with lim1 Ai ≠ 0. Roos has since shown (in "Derived functors of inverse limits revisited") that his result is correct if C has a set of generators (in addition to satisfying (AB3) and (AB4*)).

Barry Mitchell has shown (in "The cohomological dimension of a directed set") that if I has cardinality $$\aleph_d$$ (the dth infinite cardinal), then Rnlim is zero for all n ≥ d + 2. This applies to the I-indexed diagrams in the category of R-modules, with R a commutative ring; it is not necessarily true in an arbitrary abelian category (see Roos' "Derived functors of inverse limits revisited" for examples of abelian categories in which limn, on diagrams indexed by a countable set, is nonzero for n > 1).

Related concepts and generalizations
The categorical dual of an inverse limit is a direct limit (or inductive limit). More general concepts are the limits and colimits of category theory. The terminology is somewhat confusing: inverse limits are a class of limits, while direct limits are a class of colimits.

title: Inverse limit