ISLAM

What is Islam ?

Islam is not a new religion, but the same truth that God revealed through all His prophets to every people. For a fifth of the world's population, Islam is both a religion and a complete way of life. Muslims follow a religion of peace, mercy, and forgiveness, and the majority have nothing to do with the extremely grave events which have come to be associated with their faith.

Who is Muhammad? Muhammad, was born in Makkah in the year 570, at a time when Christianity was not yet fully established in Europe. Since his father died before his birth, and his mother shortly afterwards, he was raised by his uncle from the respected tribe of Quraysh. As he grew up, he became known for his truthfulness, generosity and sincerity, so that he was sought after for his ability to arbitrate in disputes. The historians describe him as calm and meditative. Muhammad was of a deeply religious nature, and had long detested the decadence of his society. It became his habit to meditate from time to time in the Cave of Hira near the summit of Jabal al-Nur, the 'Mountain of Light' near Makkah.

What does Islam mean? The Arabic word 'Islam' simply means 'submission', and derives from a word meaning 'peace'. In a religious context it means complete submission to the will of God. 'Mohammedanism' is thus a misnomer because it suggests that Muslims worship Muhammad rather than God. 'Allah' is the Arabic name for God, which is used by Arab Muslims and Christians alike.

he History of Islam:

Pre-Islamic

The Arabian Peninsula the birthplace of Islam is one of the hottest and driest regions in the world, consisting mainly of deserts. Since ancient times tribes of the nomadic race had populated the region. Considered the descendents of Noah’s third son Shem they are called Semites. Over the centuries theses Semitic people have migrated into the Fertile Crescent and were assimilated to into existing civilizations.

In the sixth century AD, north of the Arabian Peninsula two great powers were locked in a seesaw power struggle. The Christian Byzantine kingdom, successors of the Roman Empire was to the Northwest and controlled the Mediterranean Sea, North Africa and the lands of Palestine. In the northeast lay the Zoroastrian Persian kingdom. Both the Byzantine and Persian kingdoms had client Arab tribes allied to their cause of trade and conquest.

The Arabian Peninsula became a land of refuge for those seeking escape from both of these empires. Heretic Christian sects like the Nestorians, and Jewish tribes escaping the oppressive Byzantines found refuge in the protective deserts and cities of the Peninsula.

Arabia was divided into tribes and cities. Each city had gods and goddess. Once a year the tribes and cities of Arabia would meet in the city of Mecca during an event known as the Hajj. In Mecca, the Kaba (Cube), a large cube shaped building housed 360 idols from all the tribes of Arabia. The Kaba was the center of Arabian religious life. Here all the warring tribes would put aside their differences as they circled the Kaba. From the Kaba they would proceed to the other shrines outside of Mecca during this five day religious event. The Hajj was a tradition that Arabs of the peninsula remembered going back hundreds of years.

Mohammed

It was in this world Mohammad Ibn Abdallah was born in the year 570 AD in the city of Mecca. His father died before he was born and his mother Amina died when he was 6 years old. Al-Muttalib his grandfather took charge of the youth and died 2 years later. Abu Talib his uncle adopted young Mohammed into his family and raised him as his own son. At the age of 12, young Mohammed was taken on a caravan-trading venture to Syria and experienced the world outside of Arabia for the first time. Here Islamic tradition informs us that a Christian monk named Buhaira, proclaimed Talib’s young nephew is the last prophet and warns him about the Jews. For the next 13 years little is known of his life except that he was involved in caravan trading in and out of Arabia.

At the age of 25, Mohammed marries a 40 year old wealthy, widow named Khadijah who owns trading caravans. During the next 15 years of his life he interactes with Arabs known as the Hanefites. Hanefites were Arabs who rejected idol worship and were searching for the true religion. They looked to the religion of the Jews and Christians as being close to the goal. The Hanefites abandonded their idols and would retreat to the caves of Mecca in meditation and prayer.

At age 40 Mohammed had his first vision in the year 610 AD. He was in a cave on Mt. Hera and thought he was demon possessed. He went to Khadijah and told her about the event. She consulted with her uncle Waraca, a Hanefite who converted to Christianity, who assured them Mohammed vision was from God. Waraca declared Mohammed was a prophet to the Arab peoples, Waraca died 2 years later never becoming a Muslim.

Mohammed proclaimed Allah as the one true god and rejected the idol worship of Mecca. Khadijah, his wife, was Mohammed first convert to Islam. Few listened to Mohammed’s message and animosity grew against him as he confronted the idol worshippers and preached his religion to Mecca. Abu Talib his uncle and his tribe the Hasims protected him during this early Meccan period. In 619 Khadijah and Abu Talib died. Abu Talib headed the Hasim clan, which Mohammed was a member. The new leader of the Hasim tribe his uncle Abu Lahab refused to protect Mohammed. During the next 3 years Mohammed would fear for his life. He sought refuge and protection in nearby cities from those seeking his life.

Then in 621 during the Hajj, Arab tribes from the city of Yatrob later to be called Medina, came for the annual pilgrimage. They met Mohammed and thought him to be a prophet and invited him to their city to bring peace and settle disputes between the warring tribes. Yathrob was founded by three Jewish tribes and the idea of monotheism was familiar to its Arab tribesmen. The Arabs of Medina had been told by Jewish tribesmen about the coming Messiah who would one day conquer the world including the Arabs. The Arab tribes hoped to find this individual before the Jews. Meeting Mohammed they thought he was the one.

The Hejira (Flight)

The next year the situation became intolerable for the Muslims and in in June 622 they made what has become known as the Hejira or flight. In small groups the 150 Muslims of Mecca left for the city of Medina 280 miles to the north. When word reached those of Mecca about the escape to Medina they tried to kill Mohammed. Mohammed and Abu Bakr were able to sneak out of the city and escape to Medina by another route in September 622.

In Medina the warring Arab tribes submitted to Mohammed leadership and prophet-hood. The Jewish tribes rejected his claims of prophet and ridiculed his revelations. With most of the new arrivals from Mecca without work they needed to earn a living. Ghazu or caravan raiding was a way tribes would prevent one tribe from becoming to powerful. The Muslims in Medina began to rob the caravans heading toward Mecca. This is where the Muslim doctrine of Jihad was created.

With their caravan business being threatened, Mecca responds with one thousand solders at the battle of Bedr in March 624 the Muslims fielded 300 warriors. The battle went to the Muslims. Mohammed proclaimed his victory was a sign from Allah and his status in Medina was magnified. The lack of enthusiasm by one of the Jewish tribes caused them to be expelled by the victorious Muslim army. The direction of prayer was also changed from Jerusalem to Mecca as the Jews rejected Mohammad’s prophet-hood.

Exactly one year latter Mecca amassed 3000 solders at the battle of Uhud and the Muslims fielded 1000 solders. The battle did not go as planned. The Muslims defeated by Mecca retreated to Medina. Disheartened, Muslims blamed the second Jewish tribe as conspirators against their cause. Their homes and possessions were confiscated, and they are expelled from the city in 626 AD.

The Meccans in the hope of ending the caravan raids by the Muslims assembled 10,000 solders to attack the city of Medina in the year 627. After a two weeks siege in the hot sun they are unable to penetrate the fortress like city. They returned to Mecca. After this unsuccessful attack, Mohammed and the Muslims attacked the last remaining Jewish tribe. The tribe surrendered to the mercy of Mohammed. The men were killed and the women and children were sold into slavery.

The Muslims then begin to consolidate their power with the surrounding Arab tribes and cities.

Mecca began to feel the economic impact of its trading losses and Mohammed’s power grew in the north. They reluctantly signed the 10 year Hudaybiah peace agreement with Mohammed and the Muslims in march 628. Muslims are allowed to return to Mecca and worship at the Kaba once a year. The people of Mecca would leave their city so the Muslim could come and worship.

Two years later, in January 630, Mohammed leads 10,000 warriors to Mecca and nullifies the treaty of Hudaybiah because Muslims have been killed. The city submits to Mohammed and his warriors and accepts him as prophet. Mohammed goes to the Kaba and destroys the 360 idols in the structure. From Mecca, the “Muslims” wage Jihad on the surrounding cities forcing them to accept Islam as their religion and Mohammed as their prophet.

Mohammed made his final Hajj in 632 and died unexpectedly 3 months later in June. His friend and father in law Abu Bakr (Father of Aisha) succeeded him as leader of the Muslims

After Mohammad

Abu Bakr received the title “Caliph” or successor of Mohammed. Their was a struggle for about who would succeed Mohammad, some felt Ali the husband of Fatima, Mohammed’s daughter deserved the position. Under Abu Bakr Islam's power in Arabian peninsula was completed. In 634 AD Abu Bakr died and was succeeded by Umar (Omar) the 2^nd Caliphate.

Umar advanced the Muslim armies against Syria and Palestine. In 637 A D, the armies of Byzantium lost control of Jerusalem to Islam. Uthman the 3^rd Caliph succeeded Umar. Uthman ordered a complete revision of the Quran, this would cause a mutiny. He was killed and his death was considered justified because the mutineers claimed he ceased to be a Muslim. Following Uthman’s There was a struggle between rival factions of Islam about who was the rightful successor to lead Islam.

Ali the 4^th Caliph, Mohammad’s son-in-law and husband of Fatima, succeeded Uthman everybody did not accept him as rightful Caliphate. War broke out between the rival groups, his succession was short lived, 2 years later he was killed, the Shi’a (Party of Ali) mourned the death of Ali, and his two sons (Grandsons of Mohammed). Ali is revered as a saint by the Shi’a who are dominate in Iran and Iraq. The Shi’a feel Ali was the rightful successor to Mohammed and don’t recognize the three earlier Caliphs. The Sunnis accept Ali and the first three Caliphate as legitimate.

After the defeat the Byzantines and Persian kingdoms in successive battles, the armies of Islam advanced on Europe. Within 100 years of Mohammad’s death the armies of Islam reached the city of Tours, in France. In Tours the Muslim advance was stopped.

In the Battle of Tours Charles Martel the grandfather of Charlemagne defeated the advancing Muslim armies. From Tours Muslim power in Europe retreated and in the 1489 Fredinand and Isabella of Spain defeated the last remaining forces in Spain. Later, the Ottoman Empire would retreat from the rest of Europe.

In the East, Islam was also expanding by the 13th century; Islam had reached the Pacific Ocean. The Islamic faith now spanned from the Atlantic to the Pacific. Ferdinand Magellan, in his attempt to bypass Muslim controlled areas in the Indian Ocean, found the passageway to Asia via the Atlantic Ocean. His desire was to bring Christianity to Asia, before Islam. Magellan was successful in introducing Christianity to the Philippines (Named after King Philip of Spain) Islam and Christianity met in the Philippines as the Northern Islands were converted to Christianity and the Southern parts of the Philippines and Indonesia were converted to Islam. Islam and Christianity became the two major rival religions in the world.

Islam Today

Islam today is in conflict, between western secular culture and traditional Islamic culture. The growth of Islamic Fundamentalism is an attempt to reach back to the glories of Islamic history. Many Fundamentalist (Muslim) ask themselves the question, If Islam is the religion of Allah, why are we being defeated by the West (United States) and Israel. The fundamentalist sees the problem with the failure of Islamic nations to live as the Quran commands. This view of not living the life required by Allah, as specified in the Quran and traditions and therefore being defeated by the West, is the spark of fundamentalism. Today in Islam there is a struggle between moderate and fundamentalist ideology. Understanding the books of the Islamic faith is just as important to understanding its history. The books of Islam shape both the culture and philosophy of the Muslim world

HINDUISM

Hinduism

Hinduism is also referred as Vaidika Dharma, meaning "religion of the Vedas," in the ancient Hindu scriptures. Hinduism is not strictly a religion. It is based on the practice of Dharma, the code of life. The original name of Hindu Dharma is Sanatana Dharma, or "universal religion." The underlying tenets of Hinduism cannot be easily defined. Unlike other religions, Hindu Dharma did not originate from a single person, a single book, or at a single point in time. The foundations of this oldest surviving religion were laid by ancient rishis (sages), who taught their disciples the eternal principles of life they had discovered through their meditations. Hindu Dharma is essentially a religion of principles rather than persons. Since Hinduism has no founder, anyone who practices Dharma can call himself a Hindu. Statistically, there are over 800 million Hindus, concentrated mainly in India and Nepal.

Birth of Word 'Hindu'

Hindustan was the land that existed beyond the river Indus, and those that lived there were referred as Hindus. We can see clearly that the word Hindu was originally a secular word meant to define and distinguish people of the Indian subcontinent, rather than those practicing a particular religion.If we go by these ancient traditions, there is hardly any difference between a Hindu and an Indian. Both the words were corrupt forms of the original Sanskrit word 'Sindhu' meaning river in general and the Indus river in particular. The Greeks referred to those living in the subcontinent as 'Indos' while the Muslim scholars called them 'Hindus'.
There was however one particular difference. The Greek historians who called the subcontinent as 'Indos' hardly knew much about the religious activity of the region, while the Muslim scholars had some knowledge of the native traditions though not in complete detail.But they chose to describe the natives as Hindus to contrast them with the Muslims. The Europeans who came to India from the sixteenth century onwards followed the same tradition and referred the natives as Hindus to distinguish them from the non-Muslims. More than tradition perhaps it was convenience which prompted them to use the word 'Hindu' to describe the vast majority of the non-Muslim population of India.

The 'Hindoos' of British Raj

It is interesting to note that the Hindus never referred themselves as Hindus until modern times. The earliest reference to the word 'Hindu' is said to be found in the Gaudiya Vaishnava texts of the 16th century A.D. It was only during the 18th and 19th centuries that Hindus started accepting the word to describe their religious faith which stood in stark contrast to Christianity and Islam. The British, who were till then referring the natives variously as natives, baniyans, heathens, gentoos, etc, now started referring all the non-Muslim natives as 'Hindoos'.For the educated modern Hindu of that period the word was a very convenient way to establish his identity against the British as well as the native Muslims. For some time the word 'Hinduism' was used in a restricted sense, to designate the Vedic religion or Brahminism. But with the emergence of new reform movements, which played a very crucial role in restructuring and redefining the social and religious traditions of the country, the word came to encompass the entire religious tradition that originated from the Vedas and continued through centuries.

The Hindus may come from different regions, speak different languages, belong to different economic and social strata, may oppose each other politically, may not even like each other personally due to ideological or ethical or ethnic reasons, but they do not fail to experience the bond of a religious tradition that is common to them. They know clearly that the tradition that binds them together was before them and would remain forever after them.
This in essence what Hinduism is. It is a living tradition which communicates through the hearts, minds and spirits of its millions of adherents. The word 'Hindu' is very much secular in its origin and a typical Hindu is very much secular in his out look and attitude towards all religious faiths and living traditions.Hinduism incorporates an extraordinarily diverse range of beliefs and practices which aim to deliver salvation (moksha) to its devotees.

What Is Life? is a 1944 non-fiction science book written for the lay reader by physicist Erwin Schrödinger. The book was based on a course of public lectures delivered by Schrödinger in February 1943, under the auspices of the Dublin Institute for Advanced Studies at Trinity College, Dublin. The lectures attracted an audience of about 400, who were warned "that the subject-matter was a difficult one and that the lectures could not be termed popular, even though the physicist’s most dreaded weapon, mathematical deduction, would hardly be utilized."^[1] Schrödinger's lecture focused on one important question: "how can the events in space and time which take place within the spatial boundary of a living organism be accounted for by physics and chemistry?"^[1]

In the book, Schrödinger introduced the idea of an "aperiodic crystal" that contained genetic information in its configuration of covalent chemical bonds. In the 1950s, this idea stimulated enthusiasm for discovering the genetic molecule. Although the existence of DNA had been known since 1869, its role in reproduction and its helical shape were still unknown at the time of Schrödinger's lecture. In retrospect, Schrödinger's aperiodic crystal can be viewed as a well-reasoned theoretical prediction of what biologists should have been looking for during their search for genetic material. Francis Crick, co-discoverer of the structure of DNA, credited Schrödinger's book with presenting an early theoretical description of how the storage of genetic information would work, and acknowledged the book as a source of inspiration for his initial research.^[2]

Background

The book is based on lectures delivered under the auspices of the Institute at Trinity College, Dublin, in February 1943 and published in 1944. At that time DNA was not yet accepted as the carrier of hereditary information, which only was the case after the Hershey-Chase experiment of 1952. One of the most successful branches of physics at this time was statistical physics, and quantum mechanics, a theory which is also very statistical in its nature. Schrödinger himself is one of the founding fathers of quantum mechanics.

Max Delbrück's thinking about the physical basis of life was an important influence on Schrödinger.^[3] Geneticist and 1946 Nobel-prize winner H.J. Muller had in his 1922 article "Variation due to Change in the Individual Gene"^[4] already laid out all the basic properties of the heredity molecule that Schrödinger derives from first principles in What is Life?, properties which Muller refined in his 1929 article "The Gene As The Basis of Life"^[5] and further clarified during the 1930s, long before the publication of What is Life?^{[6][verification needed]}

Content

In chapter I, Schrödinger explains that most physical laws on a large scale are due to chaos on a small scale. He calls this principle "order-from-disorder." As an example he mentionsdiffusion, which can be modeled as a highly ordered process, but which is caused by random movement of atoms or molecules. If the number of atoms is reduced, the behaviour of a system becomes more and more random. He states that life greatly depends on order and that a naive physicist may assume that the master code of a living organism has to consist of a large number of atoms.

In chapter II and III, he summarizes what was known at this time about the hereditary mechanism. Most importantly, he elaborates the important role mutations play in evolution. He concludes that the carrier of hereditary information has to be both small in size and permanent in time, contradicting the naive physicist's expectation. This contradiction cannot be resolved by classical physics.

In chapter IV, Schrödinger presents molecules, which are indeed stable even if they consist of only a few atoms, as the solution. Even though molecules were known before, their stability could not be explained by classical physics, but is due to the discrete nature of quantum mechanics. Furthermore mutations are directly linked to quantum leaps.

He continues to explain, in chapter V, that true solids, which are also permanent, are crystals. The stability of molecules and crystals is due to the same principles and a molecule might be called "the germ of a solid." On the other hand an amorphous solid, without crystalline structure, should be regarded as a liquid with a very high viscosity. Schrödinger believes the heredity material to be a molecule, which unlike a crystal does not repeat itself. He calls this an aperiodic crystal. The aperiodic nature allows to encode an almost infinite number of possibilities with a small number of atoms. He finally compares this picture with the known facts and finds it in accordance with them.

In chapter VI Schrödinger states:

...living matter, while not eluding the "laws of physics" as established up to date, is likely to involve "other laws of physics" hitherto unknown, which however, once they have been revealed, will form just as integral a part of science as the former.

He knows that this statement is open to misconception and tries to clarify it. The main principle involved with "order-from-disorder" is the second law of thermodynamics, according to which entropy only increases. Schrödinger explains that living matter evades the decay to thermodynamical equilibrium by feeding on negative entropy.

In chapter VII, he maintains that "order-from-order" is not absolutely new to physics; in fact, it is even simpler and more plausible. But nature follows "order-from-disorder", with some exceptions as the movement of the celestial bodies and the behaviour of mechanical devices such as clocks. But even those are influenced by thermal and frictional forces. The degree to which a system functions mechanically or statistically depends on the temperature. If heated, a clock ceases to function, because it melts. Conversely, if the temperature approachesabsolute zero, any system behaves more and more mechanically. Some systems approach this mechanical behaviour rather fast with room temperature already being practically equivalent to absolute zero.

Schrödinger concludes this chapter and the book with philosophical speculations on determinism, free will, and the mystery of human consciousness. He is sympathetic to the Hinduconcept of Brahman, by which each individual's consciousness is only a manifestation of a unitary consciousness pervading the universe. In the final paragraph, he points out that what is meant by "I" is not the collection of experienced events but "namely the canvas upon which they are collected." If a hypnotist succeeds in blotting out all earlier reminiscences, he writes, there would be no loss of personal existence - "Nor will there ever be."^[7]

Schrödinger's paradox

The concept of Schrödinger's paradox originates from the ideas presented in What is Life?^[8] A quick account of the Schrödinger paradox and its solution: In a world governed by thesecond law of thermodynamics, all closed systems are expected to approach a state of maximum disorder. In contrast, life approaches and maintains a highly ordered state - which seems to violate aforementioned second law. The solution to this paradox is that life is not a closed system. The increase of order inside an organism is more than paid for by an increase in disorder outside this organism. By this mechanism, the second law is obeyed, and life maintains a high order state, which it sustains by causing a net increase in disorder in the Universe.

ROUTER

A router is a device that forwards data packets across computer networks. Routers perform the data "traffic directing" functions on theInternet. A router is connected to two or more data lines from different networks. When data comes in on one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table, it directs the packet to the next network on its journey or drops the packet. A data packet is typically passed from router to router through the networks of the Internet until it gets to its destination computer unless the source IP is on a private network.^[1]

The most familiar type of routers are home and small office routers that simply pass data, such as web pages and email, between the home computers and the owner's cable or DSL modem, which connects to the Internet (ISP). However more sophisticated routers range from enterprise routers, which connect large business or ISP networks up to the powerful core routers that forward data at high speed along the

Applications

When multiple routers are used in interconnected networks, the routers exchange information about destination addresses, using a dynamic routing protocol. Each router builds up a table listing the preferred routes between any two systems on the interconnected networks. A router has interfaces for different physical types of network connections, (such as copper cables, fiber optic, or wireless transmission). It also contains firmware for different networking protocol standards. Each network interface uses this specialized computer software to enable data packets to be forwarded from one protocol transmission system to another.

Routers may also be used to connect two or more logical groups of computer devices known as subnets, each with a different sub-network address. The subnets addresses recorded in the router do not necessarily map directly to the physical interface connections.^[2] A router has two stages of operation called planes:^[3]

• Control plane: A router records a routing table listing what route should be used to forward a data packet, and through which physical interface connection. It does this using internal pre-configured addresses, called static routes.

A typical home or small office router showing the ADSL telephone line and ETHERNET network cable connections.

• Forwarding plane: The router forwards data packets between incoming and outgoing interface connections. It routes it to the correct network type using information that the packet header contains. It uses data recorded in the routing table control plane.

Routers may provide connectivity within enterprises, between enterprises and the Internet, and between internet service providers (ISPs) networks. The largest routers (such as the Cisco CRS-1 or Juniper T1600) interconnect the various ISPs, or may be used in large enterprise networks.^[4] Smaller routers usually provide connectivity for typical home and office networks. Other networking solutions may be provided by a backbone Wireless Distribution System (WDS), which avoids the costs of introducing networking cables into buildings.

[edit]Enterprise routers

All sizes of routers may be found inside enterprises.^[5] The most powerful routers are usually found in ISPs, academic and research facilities. Large businesses may also need more powerful routers to cope with ever increasing demands of intranet data traffic. A three-layer model is in common use, not all of which need be present in smaller networks.^[6]

[edit]Access

Linksys by Cisco WRT54GL SoHo Router

A screenshot of the LuCI web interface used by OpenWrt. Here it is being used to configure Dynamic DNS.

Access routers, including 'small office/home office' (SOHO) models, are located at customer sites such as branch offices that do not needhierarchical routing of their own. Typically, they are optimized for low cost. Some SOHO routers are capable of running alternative free Linux-based firmwares like Tomato, OpenWrt or DD-WRT.^[7]

[edit]Distribution

Distribution routers aggregate traffic from multiple access routers, either at the same site, or to collect the data streams from multiple sites to a major enterprise location. Distribution routers are often responsible for enforcing quality of service across a WAN, so they may have considerable memory installed, multiple WAN interface connections, and substantial onboard data processing routines. They may also provide connectivity to groups of file servers or other external networks.

[edit]Security

External networks must be carefully considered as part of the overall security strategy. Separate from the router may be a firewall or VPNhandling device, or the router may include these and other security functions. Many companies produced security-oriented routers, including Cisco Systems' PIX and ASA5500 series, Juniper's Netscreen, Watchguard's Firebox, Barracuda's variety of mail-oriented devices, and many others.

[edit]Core

In enterprises, a core router may provide a "collapsed backbone" interconnecting the distribution tier routers from multiple buildings of a campus, or large enterprise locations. They tend to be optimized for high bandwidth.^[8]

[edit]Internet connectivity and internal use

Routers intended for ISP and major enterprise connectivity usually exchange routing information using the Border Gateway Protocol (BGP).RFC 4098^[9] standard defines the types of BGP-protocol routers according to the routers' functions:

• Edge router: Also called a Provider Edge router, is placed at the edge of an ISP network. The router uses External BGP to EBGP protocol routers in other ISPs, or a large enterpriseAutonomous System.
• Subscriber edge router: Also called a Customer Edge router, is located at the edge of the subscriber's network, it also uses EBGP protocol to its provider's Autonomous System. It is typically used in an (enterprise) organization.
• Inter-provider border router: Interconnecting ISPs, is a BGP-protocol router that maintains BGP sessions with other BGP protocol routers in ISP Autonomous Systems.
• Core router: A core router resides within an Autonomous System as a back bone to carry traffic between edge routers.^[10]
• Within an ISP: In the ISPs Autonomous System, a router uses internal BGP protocol to communicate with other ISP edge routers, other intranet core routers, or the ISPs intranet provider border routers.
• "Internet backbone:" The Internet no longer has a clearly identifiable backbone, unlike its predecessor networks. See default-free zone (DFZ). The major ISPs system routers make up what could be considered to be the current Internet backbone core.^[11] ISPs operate all four types of the BGP-protocol routers described here. An ISP "core" router is used to interconnect its edge and border routers. Core routers may also have specialized functions in virtual private networks based on a combination of BGP and Multi-Protocol Label Switching protocols.^[12]
• Port forwarding: Routers are also used for port forwarding between private internet connected servers.^[5]

• Voice/Data/Fax/Video Processing Routers: Commonly referred to as access servers or gateways, these devices are used to route and process voice, data, video, and fax traffic on the internet. Since 2005, most long-distance phone calls have been processed as IP traffic (VOIP) through a voice gateway,. Voice traffic that the traditional cable networks once carried. Use of access server type routers expanded with the advent of the internet, first with dial-up access, and another resurgence with voice phone service.

[edit]Historical and technical information

Leonard Kleinrock and the first IMP.

Avaya ERS 8600 (2010)

The very first device that had fundamentally the same functionality as a router does today, was the Interface Message Processor (IMP); IMPs were the devices that made up the ARPANET, the first packet network. The idea for a router (called "gateways" at the time) initially came about through an international group of computer networking researchers called the International Network Working Group (INWG). Set up in 1972 as an informal group to consider the technical issues involved in connecting different networks, later that year it became a subcommittee of the International Federation for Information Processing.^[13]

These devices were different from most previous packet networks in two ways. First, they connected dissimilar kinds of networks, such asserial lines and local area networks. Second, they were connectionless devices, which had no role in assuring that traffic was delivered reliably, leaving that entirely to the hosts (this particular idea had been previously pioneered in the CYCLADES network).

The idea was explored in more detail, with the intention to produce a prototype system, as part of two contemporaneous programs. One was the initial DARPA-initiated program, which created the TCP/IP architecture in use today.^[14] The other was a program at Xerox PARC to explore new networking technologies, which produced the PARC Universal Packet system, due to corporate intellectual property concerns it received little attention outside Xerox for years.^[15]

Some time after early 1974 the first Xerox routers became operational. The first true IP router was developed by Virginia Strazisar at BBN, as part of that DARPA-initiated effort, during 1975-1976. By the end of 1976, three PDP-11-based routers were in service in the experimental prototype Internet.^[16]

The first multiprotocol routers were independently created by staff researchers at MIT and Stanford in 1981; the Stanford router was done byWilliam Yeager, and the MIT one by Noel Chiappa; both were also based on PDP-11s.^{[17][18][19][20]}

Virtually all networking now uses TCP/IP, but multiprotocol routers are still manufactured. They were important in the early stages of the growth of computer networking, when protocols other than TCP/IP were in use. Modern Internet routers that handle both IPv4 and IPv6 are multiprotocol, but are simpler devices than routers processing AppleTalk, DECnet, IP, and Xerox protocols.

From the mid-1970s and in the 1980s, general-purpose mini-computers served as routers. Modern high-speed routers are highly specialized computers with extra hardware added to speed both common routing functions, such as packet forwarding, and specialised functions such asIPsec encryption.

There is substantial use of Linux and Unix software based machines, running open source routing code, for research and other applications.Cisco's operating system was independently designed. Major router operating systems, such as those from Juniper Networks and Extreme Networks, are extensively modified versions of Unix software.

[edit]Forwarding

For pure Internet Protocol (IP) forwarding function, a router is designed to minimize the state information associated with individual packets. The main purpose of a router is to connect multiple networks and forward packets destined either for its own networks or other networks. A router is considered a Layer 3 device because its primary forwarding decision is based on the information in the Layer 3 IP packet, specifically the destination IP address. This process is known as routing. When each router receives a packet, it searches its routing table to find the best match between the destination IP address of the packet and one of the network addresses in the routing table. Once a match is found, the packet is encapsulated in the Layer 2 data link frame for that outgoing interface. A router does not look into the actual data contents that the packet carries, but only at the layer 3 addresses to make a forwarding decision, plus optionally other information in the header for hint on, for example, QoS. Once a packet is forwarded, the router does not retain any historical information about the packet, but the forwarding action can be collected into the statistical data, if so configured.

Forwarding decisions can involve decisions at layers other than layer 3. A function that forwards based on layer 2 information, is properly called a bridge. This function is referred to as layer 2 bridging, as the addresses it uses to forward the traffic are layer 2 addresses (e.g. MAC addresses on Ethernet).

Besides making decision as which interface a packet is forwarded to, which is handled primarily via the routing table, a router also has to manage congestion, when packets arrive at a rate higher than the router can process. Three policies commonly used in the Internet are tail drop, random early detection (RED), and weighted random early detection (WRED). Tail drop is the simplest and most easily implemented; the router simply drops packets once the length of the queue exceeds the size of the buffers in the router. RED probabilistically drops datagrams early when the queue exceeds a pre-configured portion of the buffer, until a pre-determined max, when it becomes tail drop. WRED requires a weight on the average queue size to act upon when the traffic is about to exceed the pre-configured size, so that short bursts will not trigger random drops.

Another function a router performs is to decide which packet should be processed first when multiple queues exist. This is managed through quality of service (QoS), which is critical when Voice over IP is deployed, so that delays between packets do not exceed 150ms to maintain the quality of voice conversations.

Yet another function a router performs is called policy-based routing where special rules are constructed to override the rules derived from the routing table when a packet forwarding decision is made.

These functions may be performed through the same internal paths that the packets travel inside the router. Some of the functions may be performed through an application-specific integrated circuit (ASIC) to avoid overhead caused by multiple CPU cycles, and others may have to be performed through the CPU as these packets need special attention that cannot be handled by an ASIC.

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