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||p2p (peer-to-peer) is a type of network architecture in which each node has equivalent capabilities (as opposed to client/server architecture). Often peer-to-peer architecture is implemented by giving each node both server and client capabilities.
In recent usage, peer-to-peer has come to describe applications in which users can use the Internet to exchange files with each other (directly or through a mediating server). Popular recent examples of programs for connecting to such file-sharing networks are DC++, Kazaa and WinMX.
||P2PTV (peer-to-peer TV) refers to p2p software applications designed to redistribute video stream in real time on a P2P network. The distributed video streams are typically TV channels, but may also come from other sources.
In P2PTV systems, each user is simultaneously downloading the video stream and uploading that same stream to other users, thus contributing to the overall available bandwidth.
||packet (a.k.a. datagram, transmission unit) is the unit of data that is routed between an origin and a destination on the Internet or any other packet-switched network. Any information transmitted over the Internet is divided by the TCP (Transmission Control Protocol) layer into "chunks" or packets of an efficient size for routing.
||packet injection is a computer networking term which refers to sending a packet on a network into an already established connection.
It often refers to an "injection" attack by an unauthorized party, acomplished by crafting packets using raw sockets.
||Packet loss refers to the percentage of packets sent that will be lost (out of 100%) in a data transmission. As with other metrics, carriers define a benchmark amount of packet loss for their network in a Service Level Agreement (SLA). Packet loss is an indication of congestion on a network, so the level of packet loss defined by a carrier's SLA indicates the amount of congestion the carrier expects on their network.
||PacketCable is a CableLabs-led collection of projects that define QoS-enabled, IP-based services delivery platform utilizing the DOCSIS capabilities.
PacketCable consists of several sub-projects:
PacketCable 1.0/1.5: an end-to-end architecture for the delivery of digital voice telephone service (VoIP) over a DOCSIS cable network.
PacketCable 2.0: and end-to-end architecture for the delivery of enhanced digital voice services (including video telephony), and mobility services.
PacketCable Multimedia: an application independent QoS architecture for real-time IP based services.
For more information, see packetcable.com.
||Passpoint is a WiFi roaming technology that allows wireless subscribers to establish secure connectivity to hotspots and seamlessly switch and roam between them without the need to find and authenticate on the network every time they connect.
Passpoint-capable devices can roam and connect anywhere in the world where the wireless provider covers through roaming agreements.
The Passpoint roaming standard is developed in the Wi-Fi Alliance through partnerships between mobile device manufacturers, network equipment vendors, and operators.
||PAT (Port Address Translation) a.k.a NAPT, port mapping, NAT overloading, port-level NAT, or single-address NAT.
The term refers to an extension to NAT, in which multiple client computers communicate through the same IP, and also have unique port numbers assigned to transmissions in order to distinguish between them.
In other words, NAPT/PAT extends NAT from "one-to-one" into "many-to-one" by associating unique source ports with the data flow.
||PATA (Parallel ATA) is an acronym for Parallel Advanced Technology Attachment.
It is the most common disk drive interface (hard drives, CD-ROM, etc). The name Parallel ATA (or PATA) is used to differentiate this type of older IDE interface from the newer Serial ATA (or SATA) interface.
||A patch (or a "fix") is a quick repair job for a piece of programming.
By definition, the patch is an immediate bug fix that's not necessarily the best overall solution, however offers a quick repair until the next official version of the software is released.
||PCMCIA (Personal Computer Memory Card International Association) is an organization of 500+ companies that has developed a standard for small, credit card-sized PCMCIA cards (a.k.a. PC Cards) generally used in laptops. There are three types of PCMCIA cards with different widths, but the same rectangular size (85.6 x 54 mm). Generally, PC Cards can be exchanged on the fly without rebooting your laptop.
||PDA (Personal Digital Assistant, a.k.a. handheld) refers to a small hand-held computer often used for calendar, address book and reminder-type applications, but also capable of delivering email, Web content and many Windows-type aplications in more recent models. PDAs often provide wireless communicatin capability for (inter)networking and transfer of information to desktop computers.
||Peering is an interconnect between two or more autonomous networks directly with each other to exchange traffic, often done without any charge involved, as long as the traffic between the two networks is comparable.
The Internet is made up of connections between carrier networks. These connections can be through public access points (such as Network Access Points-NAPs, or Metropolitan Area Exchanges-MAEs), or through private agreements between carriers. Public internet access points are often overcrowded and induce additional delay to traffic that passes through them, whereas private connections negotiated between carriers often provide smoother connections.
The percentage of private peering may be helpful in evaluating a carrier. The higher the percentage of private peering, the less congested the network is likely to be.
In contrast, transit is when one network agrees to carry the traffic between another network and all other networks. The transit provider receives a "transit fee" for this service, usually based on the amount of traffic in Mbps.
||peripheral - generally refers to any external device attached to a computer, such as a mouse, keyboard, printer, any USB device, etc. The term is used to indicate that the device is external to the PC case.
||phishing - the act of emailing users falsely claiming to be someone else in an attempt to scam the user into surrendering private information that can be used for identity theft.
Such email usually directs the user to visit a bogus website that mimics a legitimate enterprise (eBay, or PayPal, for example), where they can update personal information, such as passwords, credit cards, social security number, bank account numbers, pin numbers, etc.
Phishing is a variation of the word "fishing," the idea being that bait is thrown out in hope that some "fish" will be tempted into biting.
||ping (Packet Internet Groper) is a basic Internet utility program that sends a small amount of data (ICMP packet) to test connectivity between network devices. The verb ping refers to using the ping command to test whether a particular IP address exists and can accept requests.
Ping can be used to check latency: a ping response from a remote host contains RTT (round-trip-time) as well, which is a measure of the delay (latency) of packets transfered between you and that network node.
Ping can be used to find the IP address of a domain: if you ping the hostname, you will see the dot address (such as 126.96.36.199) for that domain name.
Ping can be used to identify packet loss: when you ping a host/IP address several times, if the number of packets transmitted and the number of responses received are not equal there is some packet loss present. This might not be a very accurate measurement however, since some routers are configured to give a very low priority to (consecutive) ICMP pings.
||Physical Layer Convergence Protocol
||PoE (Power over Ethernet) is a standard that allows a single ethernet cable to provide both data connection and electric power to network devices such as wireless access points and IP cameras.
There is more than one common technique to transmit power over ethernet. Only two of the total four twisted pairs in a 10Base-T and 100Base-TX Ethernet cable are used for data, so the other twp pairs are free to be used for transmitting low voltage (typically 48V DC) to power network devices.
Even in 1000Base-T Gigabit Ethernet where all 4 pairs can be used for data, power can still be transferred through the use of "phantom power"-power sent over the same wire pairs used for data. This is possible because electricity and data use different frequencies and can travel over the same cable.
The 802.3af PoE standard defines two methods of power transmission. In one method (Alternative A), power and data are sent over the same pair, in the other method (Alternative B), two wire pairs are used to transmit data, and the remaining two pairs are used for power. The fact there are two different PoE schemes isn’t obvious to the casual user because most PoE devices are made to accept power in either format.
||POP (Point of Presence) refers to a unique access point to the Internet.
||POP3 (Post Office Protocol version 3, defined in RFC 1081) is a protocol that allows network nodes to retrieve email from a server via a temporary connection.
POP3 is useful for nodes that are not permanently connected to the network (Internet), such as residential/mobile compuers, that require a Mail (POP) Server to hold their mail until they can retreive it. Sending/transfering email between nodes on the Internet is assumed to be done via some other protocol, such as SMTP.
||Port triggering allows multiple computers behind a NAT-enabled router use applications which would normally require port forwarding of the same port to each PC, without manually forwarding ports. Similar functionality may be provided by devices, which can broadcast a port to all PCs on the network.
When the router sees a connection from a local PC to an outside server, it opens a temporary port forward to that PC from the internet so servers are able to connect back to that PC on that port.
||POTS (Plain Old Telephone Service) is low-bandwidth communication, as opposed to DSL/ISDN.
POTS uses the frequencies from 300 to 3 kHz to carry voice/data and is generally restricted to ~52 Kbps (kilobits/second). Any service sharing a line with POTS must either use frequencies above 3 kHz or convert POTS to digital and interleave with other data signals.
||Powerline (a.k.a. power-line communication, or PLC) is a range of communication technologies that define network communication of data over conductor wires that are also used simultaneously for AC electric power transmission. A wide range of power-line communication technologies are needed for different applications, ranging from home automation to Internet access and home networking.
Powerline in home networking is most widely deployed under the HomePlug Powerline Alliance standard. HomePlug AV is the most current of the HomePlug specifications, and estimated 45 million HomePlug devices are deployed worldwide.
Note that the technology may require that Powerline devices are on the same electrical circuit, and surge protectors/power strips with filtering may absorb the Powerline signal.
||PPPoA (point-to-point protocol over ATM)
A standard very similar to PPPoE (point-to-point protocol over Ethernet), with some minor differences, for example a DSL modem pumping ATM is internal to the computer, rather than being an ethernet cable away. PPPoA allows for MTUs (maximum transmission units) of 1500, as opposed to PPPoE.
||PPPoE ( Point-to-Point Protocol over Ethernet ) is a method for building PPP sessions and encapsulating PPP packets inside Ethernet frames.
PPPoE is used by a number of DSL providers. It requires either routers that have built-in PPPoE support, or PPPoE software to "dial up" and establish the session. Some notable characteristics of a PPPoE connection are that it requires a username/password to connect, and adds an additional 8-byte header to packets, reducing the maximum packet size to 1492 from 1500.
See also: RFC 2516
||PPTP (Point-to-Point Tunneling Protocol - RFC 2637) is an extension to the PPP protocol designed for VPN, that allows for private "tunnels" over the public Internet.
Generally, such tunneling refers to the ability to encapsulate packets of data formatted for one network protocol in packets used by another protocol (usually transfer of TCP/IP data over a non-TCP/IP network).
PPTP uses port 1723/tcp.
||protocol is an agreed-upon format for transmitting data between two devices. The protocol determines the following:
- 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 with 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 significant aspect about protocols is that your computer or device must support the right ones if you want to communicate with other computers.
||A proxy server is an intermediate gateway that sits between a client PC and the Internet and provices forwarding/caching service, as well as security, logging and administrative control.
A caching web proxy server saves content (such as Web pages) in its local cache the first time a request is made, and then serves the pages to other local clients from cache, without the need to forward the request to the Internet. Pages are only requested from the Internet if they are not found in cache. The proxy server forwards requests acting as a client, with its own IP address, and then in turn serves the pages to local clients.
Caching proxy servers offer transparent service to clients, they can save bandwidth and improve performance, however they can also cause slowdowns when congested, as well as some problems delivering dynamic and secure content.
||PSTN (Public Switched Telephone Network) refers to the international telephone system based on copper wires carrying analog voice data.
Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital, and includes mobile as well as fixed telephones. Most switches now use digital circuits between exchanges, with analog two-wire circuits still used to connect to most telephones.
The basic digital circuit in the PSTN is a 64 kbit/s channel called Digital Signal 0 (DS0). To carry a typical phone call the audio sound is digitized at an 8 kHz sample rate using 8-bit pulse code modulation (PCM). The call is switched using a signaling protocol (Signaling System 7) between the telephone exchanges under an overall routing strategy.
||PSU (Power Supply Unit) is the component that provides power for a computer to function. The power cord from a standard electrical outlet connects to the PSU, which converts the AC current to DC and regulates voltages that the separate devices in the computer need to function. The PSU usually has a wattage rating, which indicates the maximum power output of the PSU under load. Faster computers with more components require more powerful (in terms of watts) power supplies to provide adequate power to all components.
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