1.
Computer network
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A computer network or data network is a telecommunications network which allows nodes to share resources. In computer networks, networked computing devices exchange data with other using a data link. The connections between nodes are established using either cable media or wireless media, the best-known computer network is the Internet. Network computer devices that originate, route and terminate the data are called network nodes, nodes can include hosts such as personal computers, phones, servers as well as networking hardware. Two such devices can be said to be networked together when one device is able to exchange information with the other device, Computer networks differ in the transmission medium used to carry their signals, communications protocols to organize network traffic, the networks size, topology and organizational intent. In most cases, application-specific communications protocols are layered over other more general communications protocols and this formidable collection of information technology requires skilled network management to keep it all running reliably. The chronology of significant computer-network developments includes, In the late 1950s, in 1960, the commercial airline reservation system semi-automatic business research environment went online with two connected mainframes. Licklider developed a group he called the Intergalactic Computer Network. In 1964, researchers at Dartmouth College developed the Dartmouth Time Sharing System for distributed users of computer systems. The same year, at Massachusetts Institute of Technology, a group supported by General Electric and Bell Labs used a computer to route. Throughout the 1960s, Leonard Kleinrock, Paul Baran, and Donald Davies independently developed network systems that used packets to transfer information between computers over a network, in 1965, Thomas Marill and Lawrence G. Roberts created the first wide area network. This was an precursor to the ARPANET, of which Roberts became program manager. Also in 1965, Western Electric introduced the first widely used telephone switch that implemented true computer control, in 1972, commercial services using X.25 were deployed, and later used as an underlying infrastructure for expanding TCP/IP networks. In July 1976, Robert Metcalfe and David Boggs published their paper Ethernet, Distributed Packet Switching for Local Computer Networks, in 1979, Robert Metcalfe pursued making Ethernet an open standard. In 1976, John Murphy of Datapoint Corporation created ARCNET, a network first used to share storage devices. In 1995, the transmission speed capacity for Ethernet increased from 10 Mbit/s to 100 Mbit/s, by 1998, Ethernet supported transmission speeds of a Gigabit. Subsequently, higher speeds of up to 100 Gbit/s were added, the ability of Ethernet to scale easily is a contributing factor to its continued use. Providing access to information on shared storage devices is an important feature of many networks, a network allows sharing of files, data, and other types of information giving authorized users the ability to access information stored on other computers on the network
2.
Internet Protocol
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The Internet Protocol is the principal communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet, IP has the task of delivering packets from the source host to the destination host solely based on the IP addresses in the packet headers. For this purpose, IP defines packet structures that encapsulate the data to be delivered and it also defines addressing methods that are used to label the datagram with source and destination information. The Internet protocol suite is often referred to as TCP/IP. The first major version of IP, Internet Protocol Version 4, is the dominant protocol of the Internet and its successor is Internet Protocol Version 6. The Internet Protocol is responsible for addressing hosts and for routing datagrams from a source host to a destination host across one or more IP networks. For this purpose, the Internet Protocol defines the format of packets, each datagram has two components, a header and a payload. The IP header is tagged with the source IP address, the destination IP address, the payload is the data that is transported. This method of nesting the data payload in a packet with a header is called encapsulation, IP addressing entails the assignment of IP addresses and associated parameters to host interfaces. The address space is divided into networks and subnetworks, involving the designation of network or routing prefixes, IP routing is performed by all hosts, as well as routers, whose main function is to transport packets across network boundaries. Routers communicate with one another via specially designed routing protocols, either interior gateway protocols or exterior gateway protocols, IP routing is also common in local networks. For example, many Ethernet switches support IP multicast operations and these switches use IP addresses and Internet Group Management Protocol to control multicast routing but use MAC addresses for the actual routing. The versions currently relevant are IPv4 and IPv6, in May 1974, the Institute of Electrical and Electronic Engineers published a paper entitled A Protocol for Packet Network Intercommunication. The papers authors, Vint Cerf and Bob Kahn, described a protocol for sharing resources using packet switching among network nodes. A central control component of this model was the Transmission Control Program that incorporated both connection-oriented links and datagram services between hosts, the model became known as the Department of Defense Internet Model and Internet protocol suite, and informally as TCP/IP. IP versions 0 to 3 were experimental versions, used between 1977 and 1979, IEN26, dated February 1978 describes a version of the IP header that uses a 1-bit version field. IEN28, dated February 1978 describes IPv2, IEN41, dated June 1978 describes the first protocol to be called IPv4. The IP header is different from the modern IPv4 header, IEN44, dated June 1978 describes another version of IPv4, also with a header different from the modern IPv4 header
3.
Identification (information)
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The function of identification is to map a known quantity to an unknown entity so as to make it known. The known quantity is called the identifier and the entity is what needs identification. A basic requirement for identification is that the ID be unique, iDs may be scoped, that is, they are unique only within a particular scope. IDs may also be out of a collection of quantities such that they are unique on the collective. For data storage, identification is the capability to find, retrieve, report, change and this applies especially to information stored in databases. In database normalisation, the process of organizing the fields and tables of a database to minimize redundancy and dependency, is the central. To retrieve the data stored about an individual with the Internal Revenue Service of the United States, the SSN, then, identifies a unique individual to the IRS. No other living person has that SSN and that individual is assumed to not have more than one SSN, other data that the individuals SSN identifies with the IRS would be such things as his or her name, birthdate, and current employer. Authentication Identification Forensic profiling Profiling Unique identifier
4.
IPv4
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Internet Protocol version 4 is the fourth version of the Internet Protocol. It is one of the protocols of standards-based internetworking methods in the Internet. It still routes most Internet traffic today, despite the deployment of a successor protocol. IPv4 is described in IETF publication RFC791, replacing an earlier definition, IPv4 is a connectionless protocol for use on packet-switched networks. It operates on a best effort delivery model, in that it does not guarantee delivery and these aspects, including data integrity, are addressed by an upper layer transport protocol, such as the Transmission Control Protocol. IPv4 uses 32-bit addresses which limits the space to 4294967296 addresses. IPv4 reserves special address blocks for private networks and multicast addresses, IPv4 addresses may be represented in any notation expressing a 32-bit integer value. They are most often written in the notation, which consists of four octets of the address expressed individually in decimal numbers. For example, the quad-dotted IP address 192.0.2.235 represents the 32-bit decimal number 3221226219, which in hexadecimal format is 0xC00002EB. This may also be expressed in dotted hex format as 0xC0. 0x00. 0x02. 0xEB, or with octal byte values as 0300.0000.0002.0353. In the original design of IPv4, an IP address was divided into two parts, the identifier was the most significant octet of the address, and the host identifier was the rest of the address. The latter was called the rest field. This structure permitted a maximum of 256 network identifiers, which was found to be inadequate. To overcome this limit, the most-significant address octet was redefined in 1981 to create network classes, the revised system defined five classes. Classes A, B, and C had different bit lengths for network identification, the rest of the address was used as previously to identify a host within a network, which meant that each network class had a different capacity for addressing hosts. Class D was defined for multicast addressing and Class E was reserved for future applications, starting around 1985, methods were devised to subdivide IP networks. One method that has proved flexible is the use of the subnet mask. CIDR was designed to permit repartitioning of any address space so that smaller or larger blocks of addresses could be allocated to users, the hierarchical structure created by CIDR is managed by the Internet Assigned Numbers Authority and the regional Internet registries
5.
IPv4 address exhaustion
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IPv4 address exhaustion is the depletion of the pool of unallocated IPv4 addresses. Because there are fewer than 4.3 billion addresses available, depletion has been anticipated since the late 1980s and this depletion is one of the reasons for the development and deployment of its successor protocol, IPv6. IPv6, the technology to IPv4 which was designed to address this problem. Although the predicted depletion was already approaching its final stages as of 2008, most providers of Internet services, the top-level exhaustion occurred on 31 January 2011. Individual ISPs still had unassigned pools of IP addresses, and could recycle addresses no longer needed by their subscribers, each exhausted its pool of available addresses at different times. Internet Protocol version 4 provides 232 addresses, however, large blocks of IPv4 addresses are reserved for special uses and are unavailable for public allocation. More precisely, if a device has several interfaces, then each interface must have at least one distinct IP address assigned to it. For example, a laptop might have a network interface and a wired network interface using a network cable. Another example is a phone with a 3G network interface. All routers have to have several interfaces and typically will have several IP addresses associated with them. It is also possible that an interface can be assigned more than one IP address for various reasons, the IPv4 addressing structure provides an insufficient number of publicly routable addresses to provide a distinct address to every Internet device or service. This problem has been mitigated for some time by changes in the address allocation, the transition from classful network addressing to Classless Inter-Domain Routing delayed the exhaustion of addresses substantially. Complicating matters, IPv6-unaware NAT devices break native and 6to4 IPv6 connectivity, each of them increased the demand on the limited supply of addresses, often in ways unanticipated by the original designers of the network. New specifications of 4G devices require IPv6 addressing, always-on connections Throughout the 1990s, the predominant mode of consumer Internet access was telephone modem dial-up. By 2007, however, broadband Internet access had begun to exceed 50% penetration in many markets, broadband connections are always active, as the gateway devices are rarely turned off, so that the address uptake by Internet service providers continued at an accelerating pace. Internet demographics There are hundreds of millions of households in the developed world, in 1990, only a small fraction of these had Internet connectivity. Just 15 years later, almost half of them had persistent broadband connections, the many new Internet users in countries such as China and India are also driving address exhaustion. Many organizations continue to utilize public IP addresses for devices not accessible outside their local network, from a global address allocation viewpoint, this is inefficient in many cases, but scenarios exist where this is preferred in the organizational network implementation strategies
6.
IPv6
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IPv6 was developed by the Internet Engineering Task Force to deal with the long-anticipated problem of IPv4 address exhaustion. IPv6 is intended to replace IPv4, every device on the Internet is assigned a unique IP address for identification and location definition. With the rapid growth of the Internet after commercialization in the 1990s, by 1998, the Internet Engineering Task Force had formalized the successor protocol. IPv6 uses a 128-bit address, theoretically allowing 2128, or approximately 3. 4×1038 addresses, the actual number is slightly smaller, as multiple ranges are reserved for special use or completely excluded from use. The total number of possible IPv6 addresses is more than 7. 9×1028 times as many as IPv4, the two protocols are not designed to be interoperable, complicating the transition to IPv6. However, several IPv6 transition mechanisms have been devised to permit communication between IPv4 and IPv6 hosts, IPv6 provides other technical benefits in addition to a larger addressing space. In particular, it permits hierarchical address allocation methods that facilitate route aggregation across the Internet, the use of multicast addressing is expanded and simplified, and provides additional optimization for the delivery of services. Device mobility, security, and configuration aspects have been considered in the design of the protocol, IPv6 was first formally described in Internet standard document RFC2460, published in December 1998. In addition to offering more addresses, IPv6 also implements features not present in IPv4 and it simplifies aspects of address assignment, network renumbering, and router announcements when changing network connectivity providers. It simplifies processing of packets in routers by placing the responsibility for packet fragmentation into the end points, Network security was a design requirement of the IPv6 architecture, and included the original specification of IPsec. IPv6 does not specify interoperability features with IPv4, but essentially creates a parallel, exchanging traffic between the two networks requires translator gateways employing one of several transition mechanisms, such as NAT64, or a tunneling protocol like 6to4, 6in4, or Teredo. Internet Protocol Version 4 was the first publicly used version of the Internet Protocol and it is currently described by IETF publication RFC791, which replaced an earlier definition. IPv4 included a system that used numerical identifiers consisting of 32 bits. These addresses are typically displayed in quad-dotted notation as decimal values of four octets, each in the range 0 to 255, thus, IPv4 provides an addressing capability of 232 or approximately 4.3 billion addresses. Address exhaustion was not initially a concern in IPv4 as this version was originally presumed to be a test of DARPAs networking concepts, during the first decade of operation of the Internet, it became apparent that methods had to be developed to conserve address space. The last unassigned top-level address blocks of 16 million IPv4 addresses were allocated in February 2011 by the Internet Assigned Numbers Authority to the five regional Internet registries. However, each RIR still has available address pools and is expected to continue with standard address allocation policies until one /8 Classless Inter-Domain Routing block remains, after that, only blocks of 1024 addresses will be provided from the RIRs to a local Internet registry. This leaves African Network Information Center as the sole regional internet registry that is using the normal protocol for distributing IPv4 addresses
7.
IPv6 deployment
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Internet Protocol Version 6 is the next generation of the Internet Protocol that is in various stages of deployment on the Internet. It was designed as a replacement for the IPv4 address system, which had been in use since 1982, the rollout of IPv6 addresses commenced in mid-2000s and is ongoing. As of December 2016, Googles statistics show IPv6 availability of approximately 12% amongst its users and it is used more on weekends and adoption is uneven across countries and Internet service providers. Of all networks in the global BGP routing table,29. 2% had IPv6 protocol support, by 2011, all major operating systems in use on personal computers and server systems had production-quality IPv6 implementations. This mandates the use of IPv6 for such networks, in 2009 U. S. cellular operator Verizon released technical specifications for devices to operate on its next-generation networks. The specification mandates IPv6 operation according to the 3GPP Release 8 Specifications, in the early 2000s, governments increasingly required support for IPv6 in new equipment. The U. S. government, for example, specified in 2005 that the backbones of all federal agencies had to be upgraded to IPv6 by June 30,2008. The government of the Peoples Republic of China implemented a plan for deployment of IPv6 called the China Next Generation Internet. Major providers of Internet services, both ISPs and content providers, also began to implement IPv6 access into their products, Google publishes statistics on IPv6 adoption among Google users. A graph of IPv6 adoption since 2008 and a map of IPv6 deployment by country are available, akamai publishes by-country and by-network statistics on IPv6 adoption for traffic it sees on its global Content Distribution Network. This set of data also shows graphs for each country and network over time, a global view into the growing IPv6 routing tables can be obtained with the SixXS Ghost Route Hunter. This tool provides a list of all allocated IPv6 prefixes and marks with colors the ones that are actually being announced into the Internet BGP tables, when a prefix is announced, it means that the ISP at least can receive IPv6 packets for their prefix. Microsoft Windows has supported IPv6 since Windows 2000, and in production-ready state beginning with Windows XP, Windows Vista and later have improved IPv6 support. Mac OS X since Panther, Linux 2.6, FreeBSD, some implementations of the BitTorrent peer-to-peer file transfer protocol make use of IPv6 to avoid NAT issues common for IPv4 private networks. AnwarNet, AfriNIC has allocated range of IPv6 address space to AnwarNet, AnwarNet started IPV6 services in 2011. One of the goals was to support both IPv4 and IPv6 protocols equally. It also supports multicast routing and jumbo frames, IPv6 Now Pty Ltd introduced the first commercial-grade IPv6 tunnel broker service in Australia on April 30,2008. Also, in June 2008, IPv6Now introduced the first dual stacked web hosting service, internode is the first commercial ISP in Australia to have full IPv6 connectivity and make IPv6 available to customers
8.
Human-readable medium
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A human-readable medium or human-readable format is a representation of data or information that can be naturally read by humans. In computing, human-readable data is encoded as ASCII or Unicode text. In many jurisdictions, barcode labels used in retail shopping must also include a price on the merchandise. In addition, these representations can be compressed very effectively for transmission or storage. Human readable protocols greatly reduce the cost of debugging, various organizations have standardized the definition of human-readable and machine-readable data and how they are applied in their respective fields of application, e. g. the Universal Postal Union. Occasionally human-readable is used to describe ways of encoding an arbitrary integer into a series of English words. Compared to decimal or other compact binary-to-text encoding systems, English words are easier for humans to read, remember, and type in
9.
Classless Inter-Domain Routing
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Classless Inter-Domain Routing is a method for allocating IP addresses and IP routing. The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous addressing architecture of classful network design in the Internet and its goal was to slow the growth of routing tables on routers across the Internet, and to help slow the rapid exhaustion of IPv4 addresses. This division is used as the basis of routing between IP networks and for address allocation policies. Classful network design for IPv4 sized the network address as one or more 8-bit groups, resulting in the blocks of Class A, B, classless Inter-Domain Routing allocates address space to Internet service providers and end users on any address bit boundary, instead of on 8-bit segments. In IPv6, however, the interface identifier has a size of 64 bits by convention. It is based on the variable-length subnet masking technique with effective qualities of specifying arbitrary-length prefixes.168.2. 0/24 for IPv4, CIDR introduced an administrative process of allocating address blocks to organizations based on their actual and short-term projected needs. An IP address is interpreted as composed of two parts, a network-identifying prefix followed by a host identifier within that network, in the previous classful network architecture, IP address allocations were based on the bit boundaries of the four octets of an IP address. An address was considered to be the combination of an 8,16, or 24-bit network prefix along with a 24,16, as the initial TCP/IP network grew to become the Internet during the 1980s, the need for more flexible addressing schemes became increasingly apparent. This led to the development of subnetting and CIDR. The network class distinctions were removed, and the new system was described as being classless, with respect to the old system, an updated version of the specification was published as RFC4632 in 2006. Variable-length subnet masks are mentioned in RFC950, accordingly, techniques for grouping addresses for common operations were based on the concept of cluster addressing, first proposed by Carl-Herbert Rokitansky. CIDR notation is a representation of an IP address and its associated routing prefix. The notation is constructed from an IP address, a character. The number is the count of leading 1 bits in the routing mask, the IP address is expressed according to the standards of IPv4 or IPv6. The address may denote a single, distinct interface address or the address of an entire network. The maximum size of the network is given by the number of addresses that are possible with the remaining, the aggregation of these bits is often called the host identifier. For example,192.168.100. 14/24 represents the IPv4 address 192.168.100.14 and its associated routing prefix 192.168.100.0, or equivalently, its subnet mask 255.255.255.0, which has 24 leading 1-bits. The IPv4 block 192.168.100. 0/22 represents the 1024 IPv4 addresses from 192.168.100.0 to 192.168.103.255
10.
Internet Assigned Numbers Authority
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Following ICANNs transition to a global multistakeholder governance model, the IANA functions were transferred to Public Technical Identifiers, an affiliate of ICANN. In addition, five regional Internet registries delegate number resources to their customers, local Internet registries, Internet service providers, a local Internet registry is an organization that assigns parts of its allocation from a regional Internet registry to other customers. Most local Internet registries are also Internet service providers, IANA is broadly responsible for the allocation of globally unique names and numbers that are used in Internet protocols that are published as Request for Comments documents. These documents describe methods, behaviors, research, or innovations applicable to the working of the Internet, IANA maintains a close liaison with the Internet Engineering Task Force and RFC Editorial team in fulfilling this function. IANA is responsible for assignment of Internet numbers which are numerical identifier assigned to an Internet resource or used in the protocols of the Internet Protocol Suite. Examples include IP addresses and autonomous system numbers, IANA delegates allocations of IP address blocks to regional Internet registries. Each RIR allocates addresses for a different area of the world, collectively the RIRs have created the Number Resource Organization formed as a body to represent their collective interests and ensure that policy statements are coordinated globally. The RIRs divide their allocated address pools into smaller blocks and delegate them to Internet service providers, since the exhaustion of the Internet Protocol Version 4 address space, no further IPv4 address space is allocated by IANA. IANA administers the data in the root nameservers, which form the top of the hierarchical Domain name system tree and this task involves liaising with top-level domain operators, the root nameserver operators, and ICANNs policy making apparatus. IANA administers many parameters of IETF protocols, examples include the names of uniform resource identifier schemes and character encodings recommended for use on the Internet. This task is performed under the oversight of the Internet Architecture Board, on March 26,1972, Vint Cerf and Jon Postel at UCLA called for establishing a socket number catalog in RFC322. Network administrators were asked to submit a note or place a call, describing the function. This catalog was published as RFC433 in December 1972. In it Postel first proposed a registry of assignments of port numbers to network services, calling himself the czar of socket numbers. The first reference to the name IANA in the RFC series is in RFC1083, published in December,1988 by Postel at USC-ISI, there was widespread dissatisfaction with this concentration of power in one company, and people looked to IANA for a solution. Postel wrote up a draft on IANA and the creation of new top level domains and he was trying to institutionalize IANA. In retrospect, this would have been valuable, since he died about two years later. Jon Postel managed the IANA function from its inception on the ARPANET until his death in October 1998, by his almost 30 years of selfless service, Postel created his de facto authority to manage key parts of the Internet infrastructure
11.
Regional Internet registry
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A regional Internet registry is an organization that manages the allocation and registration of Internet number resources within a particular region of the world. Internet number resources include IP addresses and autonomous system numbers, collectively, the RIRs participate in the Number Resource Organization, formed as a body to represent their collective interests, undertake joint activities, and coordinate their activities globally. The Number Resource Organization is an organization uniting the five RIRs. AFRINIC, which was created in April 2005, joined on April 25,2005. Country code top-level domain Geolocation software Internet governance Local Internet registry National Internet registry
12.
Internet service provider
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An Internet service provider is an organization that provides services for accessing and using the Internet. Internet service providers may be organized in various forms, such as commercial, community-owned, non-profit, Internet services typically provided by ISPs include Internet access, Internet transit, domain name registration, web hosting, Usenet service, and colocation. The Internet was developed as a network between government research laboratories and participating departments of universities, by the late 1980s, a process was set in place towards public, commercial use of the Internet. The remaining restrictions were removed by 1995,4 years after the introduction of the World Wide Web, in 1989, the first ISPs were established in Australia and the United States. In Brookline, Massachusetts, The World became the first commercial ISP in the US and its first customer was served in November 1989. On 23 April 2014, the U. S, a possible solution to net neutrality concerns may be municipal broadband, according to Professor Susan Crawford, a legal and technology expert at Harvard Law School. On 10 November 2014, President Barack Obama recommended that the FCC reclassify broadband Internet service as a service in order to preserve net neutrality. On 31 January 2015, AP News reported that the FCC will present the notion of applying Title II of the Communications Act of 1934 to the internet in a vote expected on 26 February 2015. Adoption of this notion would reclassify internet service from one of information to one of the telecommunications and, according to Tom Wheeler, chairman of the FCC, the FCC is expected to enforce net neutrality in its vote, according to the New York Times. On 26 February 2015, the FCC ruled in favor of net neutrality by adopting Title II of the Communications Act of 1934 and Section 706 in the Telecommunications Act of 1996 to the Internet. The FCC Chairman, Tom Wheeler, commented, This is no more a plan to regulate the Internet than the First Amendment is a plan to free speech. They both stand for the same concept, on 12 March 2015, the FCC released the specific details of the net neutrality rules. On 13 April 2015, the FCC published the rule on its new Net Neutrality regulations. ISPs provide Internet access, employing a range of technologies to connect users to their network, available technologies have ranged from computer modems with acoustic couplers to telephone lines, to television cable, wireless Ethernet, and fiber optics. For users and small businesses, traditional options include copper wires to provide dial-up, DSL, typically asymmetric digital subscriber line, using fiber-optics to end users is called Fiber To The Home or similar names. Wireless access is another option, including cellular and satellite Internet access, a mailbox provider is an organization that provides services for hosting electronic mail domains with access to storage for mail boxes. It provides email servers to send, receive, accept, many mailbox providers are also access providers, while others are not. Internet hosting services provide email, web-hosting, or online storage services, other services include virtual server, cloud services, or physical server operation
13.
ARPANET
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The Advanced Research Projects Agency Network was an early packet switching network and the first network to implement the protocol suite TCP/IP. Both technologies became the foundation of the Internet. ARPANET was initially funded by the Advanced Research Projects Agency of the United States Department of Defense, the packet switching methodology employed in the ARPANET was based on concepts and designs by Americans Leonard Kleinrock and Paul Baran, British scientist Donald Davies, and Lawrence Roberts. The TCP/IP communications protocols were developed for ARPANET by computer scientists Robert Kahn and Vint Cerf, as the project progressed, protocols for internetworking were developed by which multiple separate networks could be joined into a network of networks. Access to the ARPANET was expanded in 1981 when the National Science Foundation funded the Computer Science Network, in 1982, the Internet protocol suite was introduced as the standard networking protocol on the ARPANET. Packet switching—today the dominant basis for data communications worldwide—was a new concept at the time of the conception of the ARPANET, such stations might be telephones or computers. The dedicated line typically comprises many intermediary lines which are assembled into a chain that stretches all the way from the station to the destination station. Thus, not only can the link be shared, much as a single post box can be used to post letters to different destinations and those ideas encompassed many of the features of the contemporary Internet. In October 1963, Licklider was appointed head of the Behavioral Sciences and Command and he convinced Ivan Sutherland and Bob Taylor that this network concept was very important and merited development, although Licklider left ARPA before any contracts were assigned for development. Taylor recalls the circumstance, For each of three terminals, I had three different sets of user commands. So, if I was talking online with someone at S. D. C. and I wanted to talk to someone I knew at Berkeley, or M. I. T. about this, I had to get up from the S. D. C. Terminal, go over and log into the terminal and get in touch with them. Its obvious what to do, If you have three terminals, there ought to be one terminal that goes anywhere you want to go. Donald Davies at the United Kingdoms National Physical Laboratory independently invented the concept in 1965. His work, presented by a colleague, initially caught the attention of ARPANET developers at a conference in Gatlinburg, Tennessee and he gave the first public demonstration, having coined the term packet switching, on 5 August 1968 and incorporated it into the NPL network in England. Larry Roberts at ARPA applied Davies concepts of packet switching for the ARPANET, the NPL network followed by ARPANET were the first two networks in the world to use packet switching, and were themselves connected together in 1973. The NPL network was using line speeds of 768 kbit/s, by mid-1968, Taylor had prepared a complete plan for a computer network, and, after ARPAs approval, a Request for Quotation was issued for 140 potential bidders. Most computer science companies regarded the ARPA–Taylor proposal as outlandish, and only twelve submitted bids to build a network, of the twelve, at years end, ARPA considered only two contractors, and awarded the contract to build the network to BBN Technologies on 7 April 1969
14.
Internet Engineering Task Force
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The Internet Engineering Task Force develops and promotes voluntary Internet standards, in particular the standards that comprise the Internet protocol suite. It is a standards organization, with no formal membership or membership requirements. All participants and managers are volunteers, though their work is funded by their employers or sponsors. Each working group has a chairperson, along with a charter that describes its focus, and what. It is open to all who want to participate, and holds discussions on a mailing list or at IETF meetings. Rough consensus is the basis for decision making. There are no formal voting procedures, because the majority of the IETFs work is done via mailing lists, meeting attendance is not required for contributors. Each working group is intended to work on its topic. In some cases, the WG will instead have its charter updated to take on new tasks as appropriate, the working groups are organized into areas by subject matter. Current areas are Applications, General, Internet, Operations and Management, Real-time Applications and Infrastructure, Routing, Security, each area is overseen by an area director, with most areas having two co-ADs. The ADs are responsible for appointing working group chairs, the area directors, together with the IETF Chair, form the Internet Engineering Steering Group, which is responsible for the overall operation of the IETF. The IETF is overseen by the Internet Architecture Board, which oversees its external relationships, the IAB is also jointly responsible for the IETF Administrative Oversight Committee, which oversees the IETF Administrative Support Activity, which provides logistical, etc. support for the IETF. The IAB also manages the Internet Research Task Force, with which the IETF has a number of cross-group relations. A Nominating Committee of ten randomly chosen volunteers who participate regularly at meetings is vested with the power to appoint, reappoint, and remove members of the IESG, IAB, IASA, and the IAOC. To date, no one has been removed by a NomCom, although people have resigned their positions. Because the IETF itself does not have members, nor is it an organization per se, IETF activities are funded by meeting fees, meeting sponsors and by the Internet Society via its organizational membership and the proceeds of the Public Interest Registry. In December 2005 the IETF Trust was established to manage the copyrighted materials produced by the IETF, the first IETF meeting was attended by 21 U. S. -government-funded researchers on 16 January 1986. It was a continuation of the work of the earlier GADS Task Force, representatives from non-governmental entities were invited to attend starting with the fourth IETF meeting in October 1986
15.
Dot-decimal notation
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Dot-decimal notation is a presentation format for numerical data. It consists of a string of numbers, each pair separated by a full stop. A common use of notation is in information technology where it is a method of writing numbers in octet-grouped base-10 numbers separated by dots. In computer networking, Internet Protocol Version 4 addresses are written using the quad-dotted notation of four decimal integers. Dot-decimal notation is a format for numerical data expressed as a string of decimal numbers each separated by a full stop. In computer networking, the term is used as a synonym of dotted quad notation, or quad-dotted notation. For example, the hexadecimal number 0xFF0000 may be expressed in dot-decimal notation as 255.0.0, object identifiers use a style of dot-decimal notation to represent an arbitrarily deep hierarchy of objects identified by decimal numbers. An Internet Protocol Version 4 address has 32 bits, for example, the address of the loopback interface, usually assigned the host name localhost, is 127.0.0.1. It consists of the four octets, written in notation,01111111,00000000,00000000. No formal specification of this textual IP address representation exists, a table in RFC790 used the dotted decimal format, zero-padding each number to three digits. A popular implementation of IP networking, originating in 4. 2BSD, in addition to the basic four-decimals format and full 32-bit addresses, it also supported intermediate syntax forms of octet. 24bits and octet. octet. 16bits. It also allowed the numbers to be written in hexadecimal and octal, by prefixing them with 0x and 0 and these features continue to be supported by software until today, even though they are seen as non-standard. For example,127.0.0. 1/8 specifies that the IP address has an 8-bit routing prefix, and therefore the subnet mask 255.0.0.0
16.
Address space
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In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity. For software programs to save and retrieve stored data, each unit of data must have an address where it can be located or else the program will be unable to find. The number of spaces available will depend on the underlying address structure. Address spaces are created by combining enough uniquely identified qualifiers to make an address unambiguous, for a persons physical address, the address space would be a combination of locations, such as a neighborhood, town, city, or country. Some elements of a space may be the same– but if any element in the address is different than addresses in said space will reference different entities. An address space usually provides a partitioning to several regions according to the structure it has. In the case of order, as for memory addresses. Some nested domains hierarchy appears in the case of directed ordered tree as for the Domain Name System or a directory structure, another common feature of address spaces are mappings and translations, often forming numerous layers. This usually means that some higher-level address must be translated to lower-level ones in some way, then, for a disk drive connected via Parallel ATA, each of them must be converted to logical cylinder-head-sector address due to the interface historical shortcomings. It is converted back to LBA by the controller and then, finally, to physical cylinder, head. The Domain Name System maps its names to network-specific addresses, which in turn may be mapped to link layer network addresses via Address Resolution Protocol, also, network address translation may occur on the edge of different IP spaces, such as a local area network and the Internet. An iconic example of virtual-to-physical address translation is virtual memory, where different pages of virtual address space map either to page file or to main memory address space. It is possible that several different virtual addresses all refer to one physical address. It is also possible that a virtual address maps to zero, one. Linear address space Name space Virtualization
17.
Hexadecimal
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In mathematics and computing, hexadecimal is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, Hexadecimal numerals are widely used by computer system designers and programmers. As each hexadecimal digit represents four binary digits, it allows a more human-friendly representation of binary-coded values, one hexadecimal digit represents a nibble, which is half of an octet or byte. For example, a byte can have values ranging from 00000000 to 11111111 in binary form. In a non-programming context, a subscript is typically used to give the radix, several notations are used to support hexadecimal representation of constants in programming languages, usually involving a prefix or suffix. The prefix 0x is used in C and related languages, where this value might be denoted as 0x2AF3, in contexts where the base is not clear, hexadecimal numbers can be ambiguous and confused with numbers expressed in other bases. There are several conventions for expressing values unambiguously, a numerical subscript can give the base explicitly,15910 is decimal 159,15916 is hexadecimal 159, which is equal to 34510. Some authors prefer a text subscript, such as 159decimal and 159hex, or 159d and 159h. example. com/name%20with%20spaces where %20 is the space character, thus ’, represents the right single quotation mark, Unicode code point number 2019 in hex,8217. In the Unicode standard, a value is represented with U+ followed by the hex value. Color references in HTML, CSS and X Window can be expressed with six hexadecimal digits prefixed with #, white, CSS allows 3-hexdigit abbreviations with one hexdigit per component, #FA3 abbreviates #FFAA33. *nix shells, AT&T assembly language and likewise the C programming language, to output an integer as hexadecimal with the printf function family, the format conversion code %X or %x is used. In Intel-derived assembly languages and Modula-2, hexadecimal is denoted with a suffixed H or h, some assembly languages use the notation HABCD. Ada and VHDL enclose hexadecimal numerals in based numeric quotes, 16#5A3#, for bit vector constants VHDL uses the notation x5A3. Verilog represents hexadecimal constants in the form 8hFF, where 8 is the number of bits in the value, the Smalltalk language uses the prefix 16r, 16r5A3 PostScript and the Bourne shell and its derivatives denote hex with prefix 16#, 16#5A3. For PostScript, binary data can be expressed as unprefixed consecutive hexadecimal pairs, in early systems when a Macintosh crashed, one or two lines of hexadecimal code would be displayed under the Sad Mac to tell the user what went wrong. Common Lisp uses the prefixes #x and #16r, setting the variables *read-base* and *print-base* to 16 can also used to switch the reader and printer of a Common Lisp system to Hexadecimal number representation for reading and printing numbers. Thus Hexadecimal numbers can be represented without the #x or #16r prefix code, MSX BASIC, QuickBASIC, FreeBASIC and Visual Basic prefix hexadecimal numbers with &H, &H5A3 BBC BASIC and Locomotive BASIC use & for hex. TI-89 and 92 series uses a 0h prefix, 0h5A3 ALGOL68 uses the prefix 16r to denote hexadecimal numbers, binary, quaternary and octal numbers can be specified similarly
18.
Octal
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The octal numeral system, or oct for short, is the base-8 number system, and uses the digits 0 to 7. Octal numerals can be made from binary numerals by grouping binary digits into groups of three. For example, the representation for decimal 74 is 1001010. Two zeroes can be added at the left,1001010, corresponding the octal digits 112, in the decimal system each decimal place is a power of ten. For example,7410 =7 ×101 +4 ×100 In the octal system each place is a power of eight. The Yuki language in California and the Pamean languages in Mexico have octal systems because the speakers count using the spaces between their fingers rather than the fingers themselves and it has been suggested that the reconstructed Proto-Indo-European word for nine might be related to the PIE word for new. Based on this, some have speculated that proto-Indo-Europeans used a number system. In 1716 King Charles XII of Sweden asked Emanuel Swedenborg to elaborate a number based on 64 instead of 10. Swedenborg however argued that for people with less intelligence than the king such a big base would be too difficult, in 1718 Swedenborg wrote a manuscript, En ny rekenkonst som om vexlas wid Thalet 8 i stelle then wanliga wid Thalet 10. The numbers 1-7 are there denoted by the l, s, n, m, t, f, u. Thus 8 = lo,16 = so,24 = no,64 = loo,512 = looo etc, numbers with consecutive consonants are pronounced with vowel sounds between in accordance with a special rule. Writing under the pseudonym Hirossa Ap-Iccim in The Gentlemans Magazine, July 1745, Hugh Jones proposed a system for British coins, weights. In 1801, James Anderson criticized the French for basing the Metric system on decimal arithmetic and he suggested base 8 for which he coined the term octal. In the mid 19th century, Alfred B. Taylor concluded that Our octonary radix is, therefore, so, for example, the number 65 would be spoken in octonary as under-un. Taylor also republished some of Swedenborgs work on octonary as an appendix to the above-cited publications, in the 2009 film Avatar, the language of the extraterrestrial Navi race employs an octal numeral system, probably due to the fact that they have four fingers on each hand. In the TV series Stargate SG-1, the Ancients, a race of beings responsible for the invention of the Stargates, in the tabletop game series Warhammer 40,000, the Tau race use an octal number system. Octal became widely used in computing systems such as the PDP-8, ICL1900. Octal was an abbreviation of binary for these machines because their word size is divisible by three
19.
Binary number
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The base-2 system is a positional notation with a radix of 2. Because of its implementation in digital electronic circuitry using logic gates. Each digit is referred to as a bit, the modern binary number system was devised by Gottfried Leibniz in 1679 and appears in his article Explication de lArithmétique Binaire. Systems related to binary numbers have appeared earlier in multiple cultures including ancient Egypt, China, Leibniz was specifically inspired by the Chinese I Ching. The scribes of ancient Egypt used two different systems for their fractions, Egyptian fractions and Horus-Eye fractions, the method used for ancient Egyptian multiplication is also closely related to binary numbers. This method can be seen in use, for instance, in the Rhind Mathematical Papyrus, the I Ching dates from the 9th century BC in China. The binary notation in the I Ching is used to interpret its quaternary divination technique and it is based on taoistic duality of yin and yang. Eight trigrams and a set of 64 hexagrams, analogous to the three-bit and six-bit binary numerals, were in use at least as early as the Zhou Dynasty of ancient China. The Song Dynasty scholar Shao Yong rearranged the hexagrams in a format that resembles modern binary numbers, the Indian scholar Pingala developed a binary system for describing prosody. He used binary numbers in the form of short and long syllables, Pingalas Hindu classic titled Chandaḥśāstra describes the formation of a matrix in order to give a unique value to each meter. The binary representations in Pingalas system increases towards the right, the residents of the island of Mangareva in French Polynesia were using a hybrid binary-decimal system before 1450. Slit drums with binary tones are used to encode messages across Africa, sets of binary combinations similar to the I Ching have also been used in traditional African divination systems such as Ifá as well as in medieval Western geomancy. The base-2 system utilized in geomancy had long been applied in sub-Saharan Africa. Leibnizs system uses 0 and 1, like the modern binary numeral system, Leibniz was first introduced to the I Ching through his contact with the French Jesuit Joachim Bouvet, who visited China in 1685 as a missionary. Leibniz saw the I Ching hexagrams as an affirmation of the universality of his own beliefs as a Christian. Binary numerals were central to Leibnizs theology and he believed that binary numbers were symbolic of the Christian idea of creatio ex nihilo or creation out of nothing. Is not easy to impart to the pagans, is the ex nihilo through Gods almighty power. In 1854, British mathematician George Boole published a paper detailing an algebraic system of logic that would become known as Boolean algebra
20.
Classful network
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A classful network is a network addressing architecture used in the Internet from 1981 until the introduction of Classless Inter-Domain Routing in 1993. The method divides the space for Internet Protocol Version 4 into five address classes by address range. Classes A, B, C are networks of three different network sizes, i. e. number of hosts for unicast addresses, the class E address range is reserved for future or experimental purposes. Under classful networking, the mask was implied by which address range the address occupied. This format was sufficient at a time only a few large networks existed, such as the ARPANET, which was assigned the network number 10. As a consequence of this architecture, the space supported only a low number of independent networks. Expansion of the network had to ensure compatibility with the address space and the Internet Protocol packet structure. The solution was to expand the definition of the number field to include more bits, allowing more networks to be designated. Since all existing network numbers at the time were smaller than 64, thus it was possible to use the most-significant bits of an address to introduce a set of address classes while preserving the existing network numbers in the first of these classes. The new addressing architecture was introduced by RFC791 in 1981 as a part of the specification of the Internet Protocol and it divided the address space into primarily three address formats, henceforth called address classes, and left a fourth range reserved to be defined later. The first class, designated as Class A, contained all addresses in which the most significant bit is zero. The network number for this class is given by the next 7 bits, therefore accommodating 128 networks in total, including the zero network, a Class B network was a network in which all addresses had the two most-significant bits set to 1 and 0. For these networks, the address was given by the next 14 bits of the address. Class C was defined with the 3 high-order bits set to 1,1, and 0, thus, for a Class C address with 8 bits available in the host field, the number of hosts is 254. Today, IP addresses are associated with a subnet mask and this was not required in a classful network because the mask was implicitly derived from the IP address itself. Any network device would inspect the first few bits of the IP address to determine the class of the address, in the following table, n indicates a bit used for the network ID. H indicates a bit used for the host ID, X indicates a bit without a specified purpose. 0 =00000000.00000000.00000000.00000000127.255.255.255 =01111111.11111111.11111111.11111111 0nnnnnnn. HHHHHHHH. HHHHHHHH. HHHHHHHH Class B128
21.
Subnetwork
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A subnetwork or subnet is a logical subdivision of an IP network. The practice of dividing a network into two or more networks is called subnetting, computers that belong to a subnet are addressed with a common, identical, most-significant bit-group in their IP address. This results in the division of an IP address into two fields, a network or routing prefix and the rest field or host identifier. The rest field is an identifier for a specific host or network interface, the routing prefix may be expressed in CIDR notation written as the first address of a network, followed by a slash character, and ending with the bit-length of the prefix. The IPv6 address specification 2001, db8, /32 is an address block with 296 addresses. For IPv4, a network may also be characterized by its subnet mask, subnet masks are also expressed in dot-decimal notation like an address. For example,255.255.255.0 is the mask for the 192.168.1. 0/24 prefix. Traffic is exchanged between subnetworks with special gateways when the routing prefixes of the address and the destination address differ. A router constitutes the logical or physical boundary between the subnets, the benefits of subnetting an existing network vary with each deployment scenario. In the address allocation architecture of the Internet using Classless Inter-Domain Routing and in large organizations and it may also enhance routing efficiency, or have advantages in network management when subnetworks are administratively controlled by different entities in a larger organization. Subnets may be arranged logically in an architecture, partitioning an organizations network address space into a tree-like routing structure. Computers participating in a such as the Internet each have at least one logical address. An address fulfills the functions of identifying the host and locating it on the network, the most common network addressing architecture is Internet Protocol version 4, but its successor, IPv6, has been increasingly deployed since approximately 2006. An IPv4 address consists of 32 bits, for readability written in a form consisting of four decimal octets separated by dots, an IPv6 address consists of 128 bits written in a hexadecimal notation and grouping 16 bits separated by colons. For the purpose of management, an IP address is divided into two logical parts, the network prefix and the host identifier or rest field. All hosts on a subnetwork have the network prefix. This routing prefix occupies the most-significant bits of the address, the number of bits allocated within a network to the internal routing prefix may vary between subnets, depending on the network architecture. While in IPv6 the prefix must consist of a set of contiguous 1-bits, in IPv4 this is not enforced, the host part is a unique local identification and is either a host number on the local network or an interface identifier
22.
Unicast
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In computer networking, unicast transmission is the sending of messages to a single network destination identified by a unique address. The term unicast is contrasted with the term broadcast which means transmitting the data to all possible destinations. Another multi-destination distribution method, multicasting, sends data only to interested destinations by using special address assignments and this failure of Unicast to cast to a single device is called a Unicast flood. Unicast messaging is used for all processes in which a private or unique resource is requested. Such applications include streaming media of many forms, internet radio stations using unicast connections may have high bandwidth costs. These terms are used by streaming content providers services. Unicast-based media servers open and provide a stream for each unique user, multicast-based servers can support a larger audience by serving content simultaneously to multiple users. IP address Multicast Broadcasting Differences Between Multicast and Unicast
23.
Network address translation
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The technique was originally used for ease of rerouting traffic in IP networks without readdressing every host. IP masquerading is a technique that hides an entire IP address space, usually consisting of private IP addresses, behind a single IP address in another, because of the popularity of this technique to conserve IPv4 address space, the term NAT has become virtually synonymous with IP masquerading. NAT implementations vary widely in their behavior in various addressing cases. The specifics of NAT behavior is not commonly documented by vendors of equipment containing implementations, the simplest type of NAT provides a one-to-one translation of IP addresses. RFC2663 refers to type of NAT as basic NAT. In this type of NAT, only the IP addresses, IP header checksum, basic NATs can be used to interconnect two IP networks that have incompatible addressing. The majority of NATs map multiple private hosts to one publicly exposed IP address, in a typical configuration, a local network uses one of the designated private IP address subnets. A router on that network has an address in that address space. The router is connected to the Internet with a public address assigned by an Internet service provider. As traffic passes from the network to the Internet, the source address in each packet is translated on the fly from a private address to the public address. The router tracks basic data about each active connection, when a reply returns to the router, it uses the connection tracking data it stored during the outbound phase to determine the private address on the internal network to which to forward the reply. One of the benefits of this is that it is a solution to the impending exhaustion of the IPv4 address space. Even large networks can be connected to the Internet with a single IP address, all IP packets have a source IP address and a destination IP address. More complex configurations are also possible, to avoid ambiguity in how to translate returned packets, further modifications to the packets are required. The vast bulk of Internet traffic is Transmission Control Protocol or User Datagram Protocol packets, RFC2663 uses the term network address and port translation for this type of NAT. Other names include port address translation, IP masquerading, NAT overload and this is the most common type of NAT and has become synonymous with the term NAT in common usage. This method enables communication through the router only when the conversation originates in the network since this establishes the translation tables. For example, a web browser in the network can browse a website outside
24.
Residential gateway
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In telecommunications networking, a residential gateway allows the connection of a local area network to a wide area network. The WAN can be a computer network, or the Internet. WAN connectivity may be provided through DSL, cable modem, a mobile phone network. The term residential gateway was originally used to distinguish the inexpensive networking devices designated for use in the home from devices used in corporate LAN environments. In recent years, however, the expensive residential gateways have gained many of the capabilities of corporate gateways. Many home LANs now are able to provide most of the functions of small corporate LANs, as a part of the carrier network, the home gateway supports remote control, detection and configuration. A modem by itself provides none of the functions of a router and it merely allows ATM or Ethernet or PPP traffic to be transmitted across telephone lines, cable wires, optical fibers, or wireless radio frequencies. On the receiving end is another modem that re-converts the transmission back into digital data packets. This allows network bridging using telephone, cable, optical, the modem also provides handshake protocols, so that the devices on each end of the connection are able to recognize each other. However, a modem generally provides few other network functions, a USB modem plugs into a single PC and allows a connection of that single PC to a WAN. If properly configured, the PC can also function as the router for a home LAN, an internal modem can be installed on a single PC, also allowing that single PC to connect to a WAN. Again, the PC can be configured to function as a router for a home LAN, a wireless access point can function in a similar fashion to a modem. It can allow a connection from a home LAN to a WAN. However, many modems now incorporate the features mentioned below and thus are appropriately described as residential gateways, may also have an internal modem, most commonly for DSL or Cable ISP. It may also provide functions such as Dynamic DNS. Most routers are self-contained components, using internally stored firmware and they are generally OS-independent, i. e. they can be accessed with any operating system. Wireless routers perform the functions as a router, but also allow connectivity for wireless devices with the LAN. Majority of the vulnerabilities were present in the web administration consoles of the routers, allowing unauthorised control either via default passwords, vendor backdoors, the Residential Gateway Home Gateway Initiative, a group of broadband providers proposing specifications for residential gateways The Residential Home Gateway on About. com
25.
IPv6 address
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An Internet Protocol Version 6 address is a numerical label that is used to identify a network interface of a computer or other network node participating in an IPv6 computer network. An IP address serves the purpose of identifying an individual network interface of a host, locating it on the network. For routing, IP addresses are present in fields of the packet header where they indicate source, IPv6 is the successor to the first addressing infrastructure of the Internet, Internet Protocol version 4. In contrast to IPv4, which defined an IP address as a 32-bit value, therefore, IPv6 has a vastly enlarged address space compared to IPv4. IPv6 addresses are classified by the primary addressing and routing methodologies common in networking, unicast addressing, anycast addressing, a unicast address identifies a single network interface. The Internet Protocol delivers packets sent to a unicast address to that specific interface, an anycast address is assigned to a group of interfaces, usually belonging to different nodes. A packet sent to an anycast address is delivered to just one of the interfaces, typically the nearest host. Anycast addresses cannot be identified easily, they have the format as unicast addresses. Almost any unicast address can be employed as an anycast address, a multicast address is also used by multiple hosts, which acquire the multicast address destination by participating in the multicast distribution protocol among the network routers. A packet that is sent to a multicast address is delivered to all interfaces that have joined the corresponding multicast group, IPv6 does not implement broadcast addressing. Broadcasts traditional role is subsumed by multicast addressing to the all-nodes link-local multicast group ff02,1, however, the use of the all-nodes group is not recommended, and most IPv6 protocols use a dedicated link-local multicast group to avoid disturbing every interface in the network. An IPv6 address consists of 128 bits, unicast and anycast addresses are typically composed of two logical parts, a 64-bit network prefix used for routing, and a 64-bit interface identifier used to identify a hosts network interface. The network prefix is contained in the most significant 64 bits of the address, the size of the routing prefix may vary, a larger prefix size means a smaller subnet id size. The bits of the subnet id field are available to the administrator to define subnets within the given network. A link-local address is based on the interface identifier. The prefix field contains the binary value 1111111010, the 54 zeroes that follow make the total network prefix the same for all link-local addresses, rendering them non-routable. Multicast addresses are formed according to several specific formatting rules, depending on the application, the prefix holds the binary value 11111111 for any multicast address. Currently,3 of the 4 flag bits in the flg field are defined, the 4-bit scope field is used to indicate where the address is valid and unique
26.
Dynamic Host Configuration Protocol
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The Dynamic Host Configuration Protocol is a standardized network protocol used on Internet Protocol networks. The DHCP is controlled by a DHCP server that dynamically distributes network configuration parameters, such as IP addresses, a router or a residential gateway can be enabled to act as a DHCP server. A DHCP server enables computers to request IP addresses and networking parameters automatically, in the absence of a DHCP server, each computer or other device on the network needs to be statically assigned to an IP address. TCP/IP defines how devices on one network communicate with devices on another network, a DHCP server can manage TCP/IP settings for devices on a network, by automatically or dynamically assigning Internet Protocol addresses to the devices. As of 2011, networks ranging in size from home networks to large campus networks, most residential network routers receive a globally unique IP address within the provider network. Within a local network, a DHCP server assigns a local IP address to each device connected to the network, the DHCP operates based on the client–server model. When a computer or other device connects to a network, the DHCP client software sends a broadcast query requesting the necessary information, any DHCP server on the network may service the request. The DHCP server manages a pool of IP addresses and information about client configuration parameters such as default gateway, domain name, the name servers, a client typically queries for this information immediately after booting, and periodically thereafter before the expiration of the information. When a DHCP client refreshes an assignment, it requests the same parameter values. On large networks that consist of links, a single DHCP server may service the entire network when aided by DHCP relay agents located on the interconnecting routers. Such agents relay messages between DHCP clients and DHCP servers located on different subnets, the request-and-grant process uses a lease concept with a controllable time period, allowing the DHCP server to reclaim IP addresses that are not renewed. Automatic allocation The DHCP server permanently assigns an IP address to a client from the range defined by the administrator. This is like dynamic allocation, but the DHCP server keeps a table of past IP address assignments, manual allocation The DHCP server issues a private IP address dependent upon each clients MAC address, based on a predefined mapping by the administrator. If no match for the clients MAC address is found, the server may or may not optionally fall back to either Dynamic or Automatic allocation, DHCP is used for Internet Protocol version 4, as well as for IPv6. While both versions serve the purpose, the details of the protocol for IPv4 and IPv6 differ sufficiently that they may be considered separate protocols. For the IPv6 operation, devices may alternatively use stateless address autoconfiguration, IPv6 hosts may also use link-local addressing to achieve operations restricted to the local network link. In 1984, the Reverse Address Resolution Protocol, defined in RFC903, was introduced to allow simple devices such as diskless workstations to dynamically obtain a suitable IP address. However, because it acted at the link layer it made implementation difficult on many server platforms
27.
Point-to-Point Protocol
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In computer networking, Point-to-Point Protocol is a data link protocol used to establish a direct connection between two nodes. It connects two routers directly without any host or any other networking device in between and it can provide connection authentication, transmission encryption, and compression. PPP is used many types of physical networks including serial cable, phone line, trunk line, cellular telephone, specialized radio links. PPP is also used over Internet access connections, Internet service providers have used PPP for customer dial-up access to the Internet, since IP packets cannot be transmitted over a modem line on their own, without some data link protocol. The only requirement for PPP is that the circuit provided be duplex, PPP was designed to work with numerous network layer protocols, including Internet Protocol, TRILL, Novells Internetwork Packet Exchange, NBF, DECnet and AppleTalk. Like SLIP, this is a full Internet connection over telephone lines via modem and it is more reliable than SLIP because it double checks to make sure that Internet packets arrive intact. PPP was designed somewhat after the original HDLC specifications, the designers of PPP included many additional features that had been seen only in proprietary data-link protocols up to that time. RFC2516 describes Point-to-Point Protocol over Ethernet as a method for transmitting PPP over Ethernet that is used with DSL. RFC2364 describes Point-to-Point Protocol over ATM as a method for transmitting PPP over ATM Adaptation Layer 5, PPP is a layered protocol that has three components, An encapsulation component that is used to transmit datagrams over the specified physical layer. A Link Control Protocol to establish, configure, and test the link as well as negotiate capabilities, one or more Network Control Protocols used to negotiate optional configuration parameters and facilities for the network layer. There is one NCP for each higher-layer protocol supported by PPP, PPP is specified in RFC1661. Link Control Protocol initiates and terminates connections gracefully, allowing hosts to negotiate connection options and it is an integral part of PPP, and is defined in the same standard specification. LCP provides automatic configuration of the interfaces at each end and for selecting optional authentication, the LCP protocol runs on top of PPP and therefore a basic PPP connection has to be established before LCP is able to configure it. RFC1994 describes Challenge-handshake authentication protocol, which is preferred for establishing connections with ISPs. Although deprecated, Password authentication protocol is still sometimes used, another option for authentication over PPP is Extensible Authentication Protocol described in RFC2284. After the link has been established, additional network configuration may take place, most commonly, the Internet Protocol Control Protocol is used, although Internetwork Packet Exchange Control Protocol and AppleTalk Control Protocol were once very popular. Internet Protocol Version 6 Control Protocol will see extended use in the future, PPP permits multiple network layer protocols to operate on the same communication link. For every network layer protocol used, a separate Network Control Protocol is provided in order to encapsulate and negotiate options for the network layer protocols
28.
Microsoft
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Its best known software products are the Microsoft Windows line of operating systems, Microsoft Office office suite, and Internet Explorer and Edge web browsers. Its flagship hardware products are the Xbox video game consoles and the Microsoft Surface tablet lineup, as of 2016, it was the worlds largest software maker by revenue, and one of the worlds most valuable companies. Microsoft was founded by Paul Allen and Bill Gates on April 4,1975, to develop and it rose to dominate the personal computer operating system market with MS-DOS in the mid-1980s, followed by Microsoft Windows. The companys 1986 initial public offering, and subsequent rise in its share price, since the 1990s, it has increasingly diversified from the operating system market and has made a number of corporate acquisitions. In May 2011, Microsoft acquired Skype Technologies for $8.5 billion, in June 2012, Microsoft entered the personal computer production market for the first time, with the launch of the Microsoft Surface, a line of tablet computers. The word Microsoft is a portmanteau of microcomputer and software, Paul Allen and Bill Gates, childhood friends with a passion for computer programming, sought to make a successful business utilizing their shared skills. In 1972 they founded their first company, named Traf-O-Data, which offered a computer that tracked and analyzed automobile traffic data. Allen went on to pursue a degree in science at Washington State University. The January 1975 issue of Popular Electronics featured Micro Instrumentation and Telemetry Systemss Altair 8800 microcomputer, Allen suggested that they could program a BASIC interpreter for the device, after a call from Gates claiming to have a working interpreter, MITS requested a demonstration. Since they didnt actually have one, Allen worked on a simulator for the Altair while Gates developed the interpreter and they officially established Microsoft on April 4,1975, with Gates as the CEO. Allen came up with the name of Micro-Soft, as recounted in a 1995 Fortune magazine article. In August 1977 the company formed an agreement with ASCII Magazine in Japan, resulting in its first international office, the company moved to a new home in Bellevue, Washington in January 1979. Microsoft entered the OS business in 1980 with its own version of Unix, however, it was MS-DOS that solidified the companys dominance. For this deal, Microsoft purchased a CP/M clone called 86-DOS from Seattle Computer Products, branding it as MS-DOS, following the release of the IBM PC in August 1981, Microsoft retained ownership of MS-DOS. Since IBM copyrighted the IBM PC BIOS, other companies had to engineer it in order for non-IBM hardware to run as IBM PC compatibles. Due to various factors, such as MS-DOSs available software selection, the company expanded into new markets with the release of the Microsoft Mouse in 1983, as well as with a publishing division named Microsoft Press. Paul Allen resigned from Microsoft in 1983 after developing Hodgkins disease, while jointly developing a new OS with IBM in 1984, OS/2, Microsoft released Microsoft Windows, a graphical extension for MS-DOS, on November 20,1985. Once Microsoft informed IBM of NT, the OS/2 partnership deteriorated, in 1990, Microsoft introduced its office suite, Microsoft Office
