The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
Ben Laurie is a software engineer, protocol designer and cryptographer. He is a founding director of The Apache Software Foundation, a core team member of OpenSSL, a member of the Shmoo Group, a director of the Open Rights Group, Director of Security at The Bunker Secure Hosting and Founder-member of FreeBMD, Visiting Fellow at Cambridge University's Computer Laboratory, a committer at FreeBSD and Advisory Board member of WikiLeaks.org. Laurie works for Google in London on various projects focused on Certificate transparency. Ben wrote Apache-SSL, the basis of most SSL-enabled versions of the Apache HTTP Server and is a co-author of OpenPGP:SDK, he developed the MUD Gods, innovative in including online creation in its endgame. Ben has written several articles and books, many of which can be found on his home page or his blog and is interested in ideal knots and their applications. Ben Laurie on Twitter
A domain name is a label that identifies a network domain: a distinct group of computers under a central administration or authority. Within the Internet, domain names are formed by the procedures of the Domain Name System. Any name registered in the DNS is a domain name. Domain names are used in various networking contexts and for application-specific naming and addressing purposes. In general, a domain name represents an Internet Protocol resource, such as a personal computer used to access the Internet, a server computer hosting a web site, or the web site itself or any other service communicated via the Internet. In 2017, 330.6 million domain names had been registered. Domain names are organized in subordinate levels of the DNS root domain, nameless; the first-level set of domain names are the top-level domains, including the generic top-level domains, such as the prominent domains com, net and org, the country code top-level domains. Below these top-level domains in the DNS hierarchy are the second-level and third-level domain names that are open for reservation by end-users who wish to connect local area networks to the Internet, create other publicly accessible Internet resources or run web sites.
The registration of these domain names is administered by domain name registrars who sell their services to the public. A qualified domain name is a domain name, specified with all labels in the hierarchy of the DNS, having no parts omitted. Labels in the Domain Name System are case-insensitive, may therefore be written in any desired capitalization method, but most domain names are written in lowercase in technical contexts. Domain names serve to identify Internet resources, such as computers and services, with a text-based label, easier to memorize than the numerical addresses used in the Internet protocols. A domain name may represent entire collections of individual instances. Individual Internet host computers use domain names as host identifiers called host names; the term host name is used for the leaf labels in the domain name system without further subordinate domain name space. Host names appear as a component in Uniform Resource Locators for Internet resources such as web sites. Domain names are used as simple identification labels to indicate ownership or control of a resource.
Such examples are the realm identifiers used in the Session Initiation Protocol, the Domain Keys used to verify DNS domains in e-mail systems, in many other Uniform Resource Identifiers. An important function of domain names is to provide recognizable and memorizable names to numerically addressed Internet resources; this abstraction allows any resource to be moved to a different physical location in the address topology of the network, globally or locally in an intranet. Such a move requires changing the IP address of a resource and the corresponding translation of this IP address to and from its domain name. Domain names are used to establish a unique identity. Organizations can choose a domain name that corresponds to their name, helping Internet users to reach them easily. A generic domain is a name that defines a general category, rather than a specific or personal instance, for example, the name of an industry, rather than a company name; some examples of generic names are books.com, music.com, travel.info.
Companies have created brands based on generic names, such generic domain names may be valuable Domain names are simply referred to as domains and domain name registrants are referred to as domain owners, although domain name registration with a registrar does not confer any legal ownership of the domain name, only an exclusive right of use for a particular duration of time. The use of domain names in commerce may subject them to trademark law; the practice of using a simple memorable abstraction of a host's numerical address on a computer network dates back to the ARPANET era, before the advent of today's commercial Internet. In the early network, each computer on the network retrieved the hosts file from a computer at SRI, which mapped computer host names to numerical addresses; the rapid growth of the network made it impossible to maintain a centrally organized hostname registry and in 1983 the Domain Name System was introduced on the ARPANET and published by the Internet Engineering Task Force as RFC 882 and RFC 883.
Today, the Internet Corporation for Assigned Names and Numbers manages the top-level development and architecture of the Internet domain name space. It authorizes domain name registrars, through which domain names may be reassigned; the domain name space consists of a tree of domain names. Each node in the tree holds information associated with the domain name; the tree sub-divides into zones beginning at the DNS root zone. A domain name consists of one or more parts, technically called labels, that are conventionally concatenated, delimited by dots, such as example.com. The right-most label conveys the top-level domain; the hierarchy of domains descends from the right to the left label in the name. For example: the label example specifies a node example.com as a subdomain of the com domain, www is a label to create www.example.com, a subdomain of example.com. Each label may contain from 1 to 63 octets; the empty label is reserved for the root node and when qualified is expressed as the empty label terminated by a dot.
The full domain name may not e
Stream Control Transmission Protocol
The Stream Control Transmission Protocol is a computer networking communications protocol which operates at the transport layer and serves a role similar to the popular protocols TCP and UDP. It is standardized by IETF in RFC 4960. SCTP provides some of the features of both UDP and TCP: it is message-oriented like UDP and ensures reliable, in-sequence transport of messages with congestion control like TCP, it differs from those protocols by providing multi-homing and redundant paths to increase resilience and reliability. In the absence of native SCTP support in operating systems, it is possible to tunnel SCTP over UDP, as well as to map TCP API calls to SCTP calls so existing applications can use SCTP without modification; the reference implementation was released as part of FreeBSD version 7. It has since been ported; the IETF Signaling Transport working group defined the protocol in the year 2000, the IETF Transport Area working group maintains it. RFC 4960 defines the protocol. RFC 3286 provides an introduction.
SCTP applications submit their data to be transmitted in messages to the SCTP transport layer. SCTP places messages and control information into separate chunks, each identified by a chunk header; the protocol can fragment a message into a number of data chunks, but each data chunk contains data from only one user message. SCTP bundles the chunks into SCTP packets; the SCTP packet, submitted to the Internet Protocol, consists of a packet header, SCTP control chunks, followed by SCTP data chunks. One can characterize SCTP as message-oriented, meaning it transports a sequence of messages, rather than transporting an unbroken stream of bytes as does TCP; as in UDP, in SCTP a sender sends a message in one operation, that exact message is passed to the receiving application process in one operation. In contrast, TCP is a stream-oriented protocol; however TCP does not allow the receiver to know how many times the sender application called on the TCP transport passing it groups of bytes to be sent out.
At the sender, TCP appends more bytes to a queue of bytes waiting to go out over the network, rather than having to keep a queue of individual separate outbound messages which must be preserved as such. The term multi-streaming refers to the capability of SCTP to transmit several independent streams of chunks in parallel, for example transmitting web page images together with the web page text. In essence, it involves bundling several connections into a single SCTP association, operating on messages rather than bytes. TCP preserves byte order in the stream by including a byte sequence number with each segment. SCTP, on the other hand, assigns a message-id to each message sent in a stream; this allows independent ordering of messages in different streams. However, message ordering is optional in SCTP. Features of SCTP include: Reliable transmission of both ordered and unordered data streams. Multihoming support in which one or both endpoints of a connection can consist of more than one IP address, enabling transparent fail-over between redundant network paths.
Delivery of chunks within independent streams eliminates unnecessary head-of-line blocking, as opposed to TCP byte-stream delivery. Explicit partial reliability. Path selection and monitoring to select a primary data transmission path and test the connectivity of the transmission path. Validation and acknowledgment mechanisms protect against flooding attacks and provide notification of duplicated or missing data chunks. Improved error detection suitable for Ethernet jumbo frames; the designers of SCTP intended it for the transport of telephony over Internet Protocol, with the goal of duplicating some of the reliability attributes of the SS7 signaling network in IP. This IETF effort is known as SIGTRAN. In the meantime, other uses have been proposed, for example, the Diameter protocol and Reliable Server Pooling. TCP has provided the primary means to transfer data reliably across the Internet. However, TCP has imposed limitations on several applications. From RFC 4960: TCP provides both reliable data transfer and strict order-of-transmission delivery of data.
Some applications need reliable transfer without sequence maintenance, while others would be satisfied with partial ordering of the data. In both of these cases, the head-of-line blocking property of TCP causes unnecessary delay. For applications exchanging distinct records or messages, the stream-oriented nature of TCP requires the addition of explicit markers or other encoding to delineate the individual records. In order to avoid sending many small IP packets where one single larger packet would have sufficed, the TCP implementation may delay transmitting data while waiting for more data being queued by the application. If and when such a small delay is undesirable, the application must explicitly request undelayed transmission on a case-by-case basis using the push facility. SCTP on the other hand allows undelayed transmission to be configured as a default for an association, eliminating any undesired delays, but at the cost of higher transfer overhead; the limited scope of TCP sockets complicates the task of providing highly-available data transfer capability using multi-homed hosts.
TCP is vulnerable to denial-of-service attacks, such as SYN attacks. Adoption has been slowed by lack of awareness, lack of implementations (particularly in Microsoft Windows
Robert Watson (computer scientist)
Robert Nicholas Maxwell Watson is a FreeBSD developer, founder of the TrustedBSD Project. He is employed as a University Lecturer in Systems and Architecture in the Security Research Group at the University of Cambridge Computer Laboratory. Watson graduated in computer science from Carnegie Mellon University and has attained a PhD from University of Cambridge; as well as Cambridge, he has worked at the National Institutes of Health, Carnegie Mellon University, Trusted Information Systems, Network Associates, McAfee, SPARTA. He obtained a PhD in computer security from the University of Cambridge Computer Laboratory, supervised by Ross Anderson and sponsored by Google. Watson's work has been supported by DARPA, Apple Computer, the Navy, other US government agencies, his main research interests are operating system security. His main open source software contributions include his work in developing the multi-threaded and multi-processor FreeBSD network stack, the TrustedBSD project, OpenBSM, his writing has been featured in forums such as ACM's Queue Magazine, the USENIX Annual Technical Conference, BSDCon, a Slashdot interview.
He was a FreeBSD Core Team member from 2000 to 2012. Watson is coauthor of the standard textbook The Design and Implementation of the FreeBSD Operating System by Marshall Kirk McKusick
For computer file systems, fdisk is a command-line utility that provides disk partitioning functions. It is available in DOS, FlexOS, OS/2, Microsoft Windows operating systems, in certain ports of FreeBSD, NetBSD, OpenBSD, DragonFly BSD and macOS for compatibility reasons. In versions of the Windows NT operating system line from Windows 2000 onwards, fdisk is replaced by a more advanced tool called diskpart. Similar utilities exist for example, BSD disklabel. IBM introduced fdisk, Fixed Disk Setup Program version 1.00, with the March 1983 release of the IBM PC/XT, the first PC to store data on a hard disk, the IBM Personal Computer DOS version 2.0. Version 1 could be used to create one FAT12 DOS partition, delete it, change the active partition, or display partition data. Fdisk writes the master boot record; the other three were intended for other operating systems such as CP/M-86 and Xenix, which were expected to have their own partitioning utilities as fdisk did not support them. In August 1984, PC DOS 3.0 added.
In April 1987, PC DOS/fdisk 3.30 added support for extended partitions, which could hold up to 23 "logical drives" or volumes. Support for FAT16B was added with Compaq MS-DOS 3.31, became available with MS-DOS/PC DOS 4.0. Most DOS fdisk programs, including the fdisk program that came with the original Windows 95, are only capable of creating FAT partitions of types FAT12, FAT16 and FAT16B. A derivative of the MS-DOS fdisk was provided with Windows 95, Windows 98, Windows ME. Only those fdisk versions shipping with Windows 95B or are able to manipulate FAT32 partitions. Windows 2000 and do not use fdisk, they have the Logical Disk Manager feature, as well as DiskPart. Unlike the fdisk programs for other operating systems, the fdisk programs for DOS and Windows 9x/Me not only alter data in the partition table, but will overwrite many sectors of data in the partition itself. Users must be sure the correct disk/partition has been chosen before using a DOS/Windows fdisk for partitioning; the fdisk /mbr switch is undocumented but well known for repairing the master boot record.
The fdisk supplied with Windows 95 does not report the correct size of a hard disk, larger than 64 GB. An updated fdisk is available from Microsoft. Microsoft named the replacement "263044usa8" and is Version 4.72.2811.0. Signature May 23, 2000; the original Windows 98 fdisk program size is smaller than the updated one. The implementation of fdisk in FreeDOS is free software; the FreeDOS version was developed by Brian E. Reifsnyder. Paragon Technology Systems PTS-DOS 2000 Pro includes an fdisk implementation. OS/2 shipped with two partition table managers up until version 4.0. These were the GUI-based fdiskpm; the two have identical functionality, can manipulate both FAT partitions and the more advanced HPFS partitions. OS/2 versions 4.5 and higher can use the JFS filesystem as well as FAT and HPFS, replace fdisk with the Logical Volume Manager. Fdisk for Mach Operating System was written by Robert Baron, it was ported to 386BSD by Julian Elischer, the implementation is being used by FreeBSD, NetBSD and DragonFly BSD, all as of 2019, as well as the early versions of OpenBSD between 1995 and 1997 before OpenBSD 2.2.
Tobias Weingartner re-wrote fdisk in 1997 before OpenBSD 2.2, which has subsequently been forked by Apple Computer, Inc in 2002, is still used as the basis for fdisk on macOS as of 2019. For native partitions, BSD systems traditionally use BSD disklabel, fdisk partitioning is supported only on certain architectures and only in addition to the BSD disklabel. In Linux the maximum number of partitions you can have with fdisk is 60 and not more than that. IBM PC DOS 7.10 contained FORMAT32 utilities. List of disk partitioning software format cfdisk Linux Partition HOWTO. Partitioning with fdisk Linux Programmer's Manual, fdisk fdisk from utils-linux-ng blkid - command-line utility to locate/print block device attributes Using the blkid Command. FreeBSD System Manager's Manual, FDISK
Ipfirewall or ipfw is a FreeBSD IP, stateful firewall, packet filter and traffic accounting facility. Its ruleset logic is similar to many other packet filters except IPFilter. Ipfw is maintained by FreeBSD volunteer staff members, its syntax enables use of sophisticated filtering capabilities and thus enables users to satisfy advanced requirements. It can either be incorporated into the kernel. Ipfw was the built-in firewall of Mac OS X until Mac OS X 10.7 Lion in 2011 when it was replaced with the OpenBSD project's PF. Like FreeBSD, ipfw is open source, it is used in many FreeBSD-based firewall products, including m0n0wall and FreeNAS. A port of ipfw and the dummynet traffic shaper is available for Linux, OpenWrt and Microsoft Windows. Wipfw is a Windows port of an old version of ipfw. netfilter/iptables, a Linux-based descendant of ipchains NPF, a NetBSD packet filter PF, another deployed BSD firewall solution ipfw section of the FreeBSD Handbook. The dummynet project - including versions for Linux, OpenWrt and Windows wipfw Windows port of an old version of ipfw