terminologie IT p->z

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P2P –  An abbreviation of Peer-to(2)-Peer.  This is a type of network in which each workstation has equivalent capabilities and responsibilities. This differs from client/server architectures, in which some computers are dedicated to serving the others. Peer-to-peer networks are generally simpler, but they usually do not offer the same performance under heavy loads.

Peer(s) –  A peer is another computer on the internet that is sharing the file you wish to download. Typically a peer does not have the complete file, if it did it would be called a seed. Peers are also called leeches, to distinguish them from those who have completed their download and continue to leave their BitTorrent Client running and act as a seed.

PeerGuardian – PeerGuardian is a program that acts as a firewall against known malicious sources (IP ranges of the RIAA and MPAA for example).  Using this software one can take one step in protecting oneself from the tactics employed by these organizations.

Port(s) – In TCP/IP and UDP networks, an endpoint to a logical connection. The port number identifies what type of port it is.  For example, port 80 is used for HTTP traffic.

PPPoE – An acronym for Point to Point Protocol over Ethernet.  PPPoE relies on two widely accepted standards: PPP and Ethernet.  PPPoE is a specification for connecting the users on an Ethernet to the Internet through a common broadband medium, such as a single DSL line, wireless device or cable modem.  All the users over the Ethernet share a common connection, so the Ethernet principles supporting multiple users in a LAN combine with the principles of PPP, which apply to serial connections.

Protocol – This is an agreed-upon format for transmitting data between two devices.
The protocol determines the following:

  • the type of error checking to be used
  • data compression method, if any
  • how the sending device will indicate that it has finished sending a message
  • how the receiving device will indicate that it has received a message

There are a variety of standard protocols from which programmers can choose.  Each has particular advantages and disadvantages; for example, some are simpler than others, some are more reliable, and some are faster.   From a user’s point of view, the only interesting aspect about protocols is that your computer or device must support the right ones if you want to communicate with other computers.  The protocol can be implemented either in hardware or in software.

Proxy Server –  This is a server that sits between a client application, such as a Web browser, and a real server. It intercepts all requests to the real server to see if it can fulfill the requests itself. If not, it forwards the request to the real server.
Proxy servers have two main purposes:

  • Improve Performance: Proxy servers can dramatically improve performance for groups of users.  This is because it saves the results of all requests for a certain amount of time.  Consider the case where both user X and user Y access the World Wide Web through a proxy server.  First user X requests a certain Web page, which we’ll call Page 1.  Sometime later, user Y requests the same page.  Instead of forwarding the request to the Web server where Page 1 resides, which can be a time-consuming operation, the proxy server simply returns the Page 1 that it already fetched for user X.  Since the proxy server is often on the same network as the user, this is a much faster operation.  Real proxy servers support hundreds or thousands of users.  The major online services such as Compuserve and America Online, for example, employ an array of proxy servers.
  • Filter Requests: Proxy servers can also be used to filter requests.  For example, a company might use a proxy server to prevent its employees from accessing a specific set of Web sites.

Query – This is a request for information from a database. There are three general methods for posing queries:

  • Choosing parameters from a menu: In this method, the database system presents a list of parameters from which you can choose.  This is perhaps the easiest way to pose a query because the menus guide you, but it is also the least flexible.
  • Query by example (QBE): In this method, the system presents a blank record and lets you specify the fields and values that define the query.
  • Query language: Many database systems require you to make requests for information in the form of a stylized query that must be written in a special query language.  This is the most complex method because it forces you to learn a specialized language, but it is also the most powerful.

Queue – There are a few meanings for queue.

  • In computer science, queuing refers to lining up jobs for a computer or device.  For example, if you want to print a number of documents, the operating system (or a special print spooler) queues the documents by placing them in a special area called a print buffer or print queue.  The printer then pulls the documents off the queue one at a time.  Another term for this is print spooling.  The order in which a system executes jobs on a queue depends on the priority system being used.  Most commonly, jobs are executed in the same order that they were placed on the queue, but in some schemes certain jobs are given higher priority.
  • In programming, a queue is a data structure in which elements are removed in the same order they were entered.  This is often referred to as FIFO (first in, first out).  In contrast, a stack is a data structure in which elements are removed in the reverse order from which they were entered. This is referred to as LIFO (last in, first out).
  • In the P2P community, a queue is a first in, first out order that is kept to allow only a certain amount of uploads at a time.  Also, at which downloads execute first.

Ratio –  A ratio of your amount uploaded divided by your amount downloaded.  The amounts used are for the current session only, not over the history of the file.  If you achieve a share ratio of 1.0, that would mean you’ve uploaded as much as you’ve downloaded.  The higher the number, the more you have contributed.  If you see a share ratio of ∞ (infinity), this happened because you opened a BitTorrent Client with a complete file (i.e., you seed the file.).  In this case you download nothing since you have the full file, and so anything you send will cause the ratio to reach infinity.  While share ratings are just displayed for your convenience, courtesy to others should cause you to keep this ratio as high as possible.  (Also see Credit System)

Reseed –  When there are zero seeds for a given torrent (and not enough peers to have a distributed copy), all the peers will get stuck with an incomplete file, since no one in the swarm has the missing pieces.  When this happens, someone with a complete file (a seed) must connect to the swarm so that those missing pieces can be transferred.  This is called reseeding.  Usually a request for a reseed comes with an implicit promise that the requester will leave his or her client open for some time period after finishing (to add longevity to the torrent).

RIAA – An acronym for The Recording Industry Association of America.  The RIAA is the trade group that represents the recording industry in the United States.  The RIAA has continued to participate in creating and administering technical standards for later systems of music recording and reproduction, including magnetic tape, cassette tapes, digital audio tapes, CDs, and software-based digital technologies.  The RIAA also participates in the collection, administration and distribution of music licenses and royalties.  The association is responsible for certifying gold and platinum albums and singles in the USA. For more information about sales data see list of best selling albums and list of best selling singles.  The RIAA has been at the heart of the file-sharing controversy, especially music files in the popular MP3 format uploaded onto the Internet using peer-to-peer software.  The RIAA has long contended that sharing of copyrighted music was a form of piracy, applying the well-known computing term to music.  Visit the RIAA home page for more information, as well as contact information to send hate mail.

SDSL – An acronym for Symmetric Digital Subscriber Line.  This is a technology that allows more data to be sent over existing copper telephone lines.  SDSL supports data rates up to 10 Mbps.  SDSL works by sending digital pulses in the high-frequency area of telephone wires and can not operate simultaneously with voice connections over the same wires.  SDSL requires a special SDSL modem.  SDSL is called symmetric because it supports the same data rates for upstream and downstream traffic.  A similar technology that supports different data rates for upstream and downstream data is called asymmetric digital subscriber line (ADSL).  ADSL is more popular in North America, whereas SDSL is being developed primarily in Europe.  (Also see xDSL)

Seed(er) –  A computer that has a complete copy of the specific torrent you are downloading.  Once your client finishes downloading, it will remain open until you click the Finish button.  This is known as seeding.  You can also start a BitTorrent Client with a complete file, and once BitTorrent has checked the file it will connect and seed the file to others.  It is good to continue seeding a file after you have finished downloading, to help others finish.  Also, when a new torrent is posted to a tracker, someone must seed it in order for it to be available to others.  The tracker doesn’t know anything of the actual contents of a file, so it’s important to follow through and seed a file if you upload the torrent to a tracker.

Server – A computer or device on a network that manages network resources.  For example, a file server is a computer and storage device dedicated to storing files.  Any user on the network can store files on the server.  A print server is a computer that manages one or more printers, and a network  server is a computer that manages network traffic.  A database  server is a computer system that processes database queries.   Servers are often dedicated, meaning that they perform no other tasks besides their server tasks.  On multiprocessing operating systems, however, a single computer can execute several programs at once.  A server in this case could refer to the program that is managing resources rather than the entire computer.

Share rating – (See Ratio)

Snubbed –  If the client has not received anything after a certain period (default: 60 seconds), it marks a connection as snubbed, in that the peer on the other end has chosen not to send.  The real function of keeping track of this variable is to improve download speeds.  Occasionally the client will find itself in a state where even though it is connected to many peers, it is choked by all of them.  The client uses the snubbed flag in an attempt to prevent this situation.  It notes that a peer with whom it would like to trade pieces with has not sent anything in a while, and rather than leaving it up to the optimistic choking to eventually select that peer, it instead reserves one of its upload slots for sending to that peer.  (Also see Choked)

SOCKS –  A protocol for handling TCP traffic through a proxy server.  It can be used with virtually any TCP application, including Web browsers and FTP clients.  It provides a simple firewall because it checks incoming and outgoing packets and hides the IP addresses of client applications.  There are two main versions of SOCKS — V4 and V5. V5 adds an authentication mechanism for additional security.  There are many freeware implementations of both versions.  One of the most common V5 implementations is SOCKS5.

Static – Generally refers to elements of the Internet or computer programming that are fixed and not capable of action or change.  A Web site that is static can only supply information that is written into the HTML and this information will not change unless the change is written into the source code.  When a Web browser requests the specific static Web page, a server returns the page to the browser and the user only gets whatever information is contained in the HTML code.  Similarly, a static IP, will always remain the same, regardless of if/when you disconnect.

Swarm –  The group of users that are collectively connected for a particular file.  Example, if you start a BitTorrent Client and it tells you that you’re connected to 5 peers and 1 seeds, then the swarm consists of you and those 6 other people.

T1 –  A dedicated phone connection supporting data rates of 1.544 Mbps per second.  A T-1 line actually consists of 24 individual channels, each of which supports 64Kbits per second.  Each 64Kbit/second channel can be configured to carry voice or data traffic.  Most telephone companies allow you to buy just some of these individual channels, known as fractional T-1 access.  T-1 lines are a popular leased line option for businesses connecting to the Internet and for Internet Service Providers (ISPs) connecting to the Internet backbone.  The Internet backbone itself consists of faster T-3 connections. T-1 lines are sometimes referred to as DS1 lines.

T3 –  A dedicated phone connection supporting data rates of about 43 Mbps.  A T-3 line actually consists of 672 individual channels, each of which supports 64 Kbps.  T-3 lines are used mainly by Internet Service Providers (ISPs) connecting to the Internet backbone and for the backbone itself.  T-3 lines are sometimes referred to as DS3 lines.

Tb – An abbreviation for terabit.  There are 1099511627776 bits in (1) terabit.  (Also see Terabit)

TB – An abbreviation for terabyte.  There are 1099511627776 bytes in (1) terabyte.  (Also see Terabyte)

TCP – An acronym for Transmission Control Protocol.  TCP is one of the main protocols in TCP/IP networks.  Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data.  TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.

TCP/IP – An acronym for Transmission Control Protocol / Internet Protocol.  This is the suite of communications protocols used to connect hosts on the Internet.  TCP/IP uses several protocols, the two main ones being TCP and IP.  TCP/IP is built into the UNIX operating system and is used by the Internet, making it the de facto standard for transmitting data over networks.  Even network operating systems that have their own protocols, such as Netware, also support TCP/IP.

Terabit – Used to describe data storage.  (Also see Tb)

Terabyte – Used to describe data storage.  (Also see TB)

Torrent –  A small metadata file which contains information about the data you want to download, not the data itself.  It is downloaded from a web site (BitTorrent file extension is .torrent) by clicking on a download link.  It can also be saved to your computer.  This is useful if you want to be able to re-open the torrent later on without having to find the link again.

Tracker –  Server on the Internet that coordinates the action of BitTorrent Clients.  Upon opening a torrent, you contact the tracker and receive a list of peers to connect to.  Throughout the transfer, your computer will query the tracker, telling it how much you’ve downloaded and uploaded and how much before finishing.  If a tracker is down and you try to open a torrent, you will be unable to connect.  If a tracker goes down during a torrent (you have already connected at some point and are already talking to peers), you will be able to continue transferring with those peers, but no new peers will be able to contact you.  Tracker errors are often temporary, leave the client open and continue trying.

UDP – An acronym for User Datagram Protocol.  This a connectionless protocol that, like TCP, runs on top of IP networks.  Unlike TCP/IP, UDP/IP provides very few error recovery services, offering instead a direct way to send and receive datagrams over an IP network.  It’s used primarily for broadcasting messages over a network.  In the world of BitTorrent, a UDP torrent is a torrent tracked by a tracker using the UDP ports.

Upload –  To transmit data from a computer to a bulletin board service, mainframe, or network. For example, if you use a personal computer to log on to a network and you want to send files across the network, you must upload the files from your PC to the network.  (Also see Upstream)

Upstream – A transmission from an end user to a server. An upstream transmission can be in the form of a signal being transmitted from a workstation to a server across a network, such as a LAN, or a signal being sent from a customer to a cable service provider.  (Also see Upload)

UPnP – An acronym for Universal Plug and Play.   This is a networking architecture that provides compatibility among networking equipment, software and peripherals of the 400+ vendors that are part of the Universal Plug and Play Forum.  UPnP works with wired or wireless networks and can be supported on any operating system.  UPnP boasts device-driver independence and zero-configuration networking.

URL – An acronym for Uniform Resource Locator.  This is the global address of documents and other resources on the World Wide Web.  The first part of the address indicates what protocol to use, and the second part specifies the IP address or the domain name where the resource is located.

VDSL – An acronym for Very High Speed Digital Subscriber Line.   DSL transmits data in the 13 Mbps – 55 Mbps range over short distances, usually between 1000 and 4500 feet (300 – 1500 meters), of twisted pair copper wire.  The shorter the distance, the faster the connection rate.  As the final length of cable into the home or office, VDSL connects to neighborhood Optical Network Units (ONUs), which connect to the central office’s main fiber network backbone.   This architecture will allow VDSL users to access the maximum bandwidth available through normal phone lines.  VDSL is currently going through a standards issue, so it isn’t widely deployed yet.  The VDSL alliance favors a line coding scheme based on Discrete Multitone (DMT), a multi-carrier system that is more compatible with existing ADSL technology.  The VDSL coalition favors a line coding scheme based on Quadature Amplitude Modulation (QAM), a single-carrier system that is less expensive and consumes less power.  (Also see xDSL)

WAN – An acronym for Wide-Area Network.   This is a computer  network that spans a relatively large geographical area.  Typically, a WAN consists of two or more local-area networks (LANs).  Computers connected to a wide-area network are often connected through public networks, such as the telephone system.  They can also be connected through leased lines or satellites.  The largest WAN in existence is the Internet.  (Also see LAN)

WiFi – An abbreviation of Wireless Fidelity.  This is meant to be used generically when referring of any type of 802.11 network, whether 802.11b, 802.11a, dual-band, etc.

xDSL –  This refers collectively to all types of digital subscriber lines, the two main categories being ADSL and SDSL.  Two other types of xDSL technologies are High-data-rate DSL (HDSL) and Very high DSL (VDSL).   DSL technologies use sophisticated modulation schemes to pack data onto copper wires.  They are sometimes referred to as last-mile technologies because they are used only for connections from a telephone switching station to a home or office, not between switching stations.   xDSL is similar to ISDN in as much as both operate over existing copper telephone lines (POTS) and both require the short runs to a central telephone office (usually less than 20,000 feet).  However, xDSL offers much higher speeds – up to 32 Mbps for downstream traffic, and from 32 Kbps to over 1 Mbps for upstream traffic.

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