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||NBTSTAT (NetBIOS over TCP/IP Statistics) is a Windows command-line utility, here are some useful flags for it:
-n Lists your NetBIOS names
-s Lists your current NetBIOS sessions
-? Displays help and information on flags
||NCQ (Native Command Queuing) is a hard disk drive technology that allows the individual disk to internally optimize the order in which received read/write commands are executed. This can reduce the amount of unnecessary drive head movement, improving performance and reducing drive wear.
The technology is especially effective in worlkoads where multiple simultaneous read/write requests are outstanding, most often occuring in server-type applications. NCQ has been typically used in SCSI drives, and is currently making its way into some SATA drives. While NCQ typically improves disk performance in the presense of multiple read/write requests, historically it has also been argued that it may indroduce some latency to access of sequential reads/writes induced by NCQ logic.
||NetBIOS (Network Basic Input Output System) - a networking protocol developed in the 1980s. Because a lot of legacy software was written for NetBIOS's API, it has been adapted to work over various other protocols such as IPX/SPX and TCP/IP.
NetBIOS over TokenRing or Ethernet is now referred to as NetBEUI. NetBIOS over TCP/IP is referred to as NetBT (or NBT). With Win 2K and later, NetBT is now the preferred NetBIOS transport.
||NetBT (a.k.a. NBT) - NetBIOS over TCP/IP
||netmask (also known as subnet mask, or address mask) is a technique used by the IP protocol to determine which network segment packets are destined for.
In essence, the subnet mask is a 32bit bitmask used to tell what portion of an IP address identifies the subnetwork, and what portion identifies the host. One of the most widely used netmasks for home/SOHO applications is 255.255.255.0, used for a Class C subnet, one with up to 255 host computers.
||NETSTAT (Network Statistics) is a command-line utility for displaying network statistics. Here are some of its more useful flags:
-? Displays help and information on all flags.
-a Displays all listening ports and active connections.
-n Displays addresses and port numbers in numerical form.
||NFC (Near Field Communication) is a short-range wireless standard that enables communication between compatible devices by simply bringing them close together (within 4 inches of each other). NFC uses electromagnetic induction between two loop antennas located within each other's near-field. It operates in the 13.56 MHz unlicensed radio frequency band.
NFC communication requires at least one transmitting (active) device, and another (passive or active) to receive the signal.
Active devices are able to both send and receive data, and can communicate with each other as well as with passive devices. Smartphones and some Bluetooth speakers are by far the most common implementation of active NFC devices.
Passive NFC devices are usually read-only tags that include a small unpowered NFC chip.
||NIC (Network Interface Card), also called a Network Adapter, is a device that connects your computer to a network. The most common types of NICs are Ethernet and Token Ring.
||National Institute of Standards and Technology
||NMS - Network Management System (or Station).
Also: Network Monitoring Station.
||NNTP (Network News Transfer Protocol) is a protocol that allows customers to view information on Usenet newsgroups. Many carriers have the option of setting up news feeds that are sent directly to a customer's news server or setting up access to the carrier's news server with a login and password.
||node is a connection point in a network, either end or redistribution point for data transmissions. In general, a node has the capability to recognize and process, or forward transmissions to other network nodes.
||NTP (Network Time Protocol) is an internet standard protocol, built on top of TCP/IP, that assures accurate time synchronization of computer clock times in a network to the millisecond.
Based on UTC (Coordinated Universal Time), NTP can synchronize client clocks to the U.S. Naval Observatory Master Clocks. It can run as a continuous background client program and periodically send time requests to NTP servers, then using the obtained timestamps to adjust the client's clock.
See also: RFC 1305
||OAN (Optical Access Network) refers to an Access Network made up of optical transmission links. This is in contrast with older technologies, which typically use copper links composed of twisted-pair or coaxial cables.
||OFDM (orthogonal frequency-division multiplexing) is a modulation technique used for high-speed 802.11a, 802.11g, 802.16 and WiMAX wireless communications.
It works by splitting radio signals into smaller narrowband channels, and transmitting simultaneously at different frequencies. In OFDM, priority is given to minimizing interference, or crosstalk.
See also: FDM (frequency-division multiplexing) and TDM (time-division multiplexing).
||Orthogonal Frequency-Division Multiple Access (OFDMA) is a method of encoding digital data on multiple frequencies. It is a digital modulation scheme, allowing a large number of sub-carrier signals to carry data on several parallel data streams or channels.
The technology works by splitting the radio signal into multiple smaller sub-signals that are then transmitted simultaneously at different frequencies. OFDM reduces the amount of crosstalk in signal transmissions. It also provides for assigning subsets of sub-carriers to different users, allowing for simultaneous low data rate transmission from several users on the same frequency band.
OFDMA is used by many cable and wireless technologies, such as, ADSL, MoCA home networking, Docsis 3.1, LTE and WiMAX.
||OLT (Optical Line Termination) provides the network-side interface of the Optical Access Network (OAN), and is connected to one or more Optical Network Units (ONUs).
||ONT (Optical Network Terminal) - device that terminates the fiber optic network at the customer premises.
Also called ONU (Optical Network Unit)
||ONU (Optical Network Unit) provides the user-side terminatioin and interface of the Optical Access Network (OAN). More than one ONU may be connected to the same Optical Line Termination (OLT) by means of passive or active intermediate elements.
Also called ONT (Optical Network Terminal)
||OSI (Open Systems Interconnection) defines a networking framework standardized by the International Organization for Standardization (ISO). Adherence to the standard enables any OSI-compliant system to communicate with any other OSI-compliant system for a meaningful exchange of information. The OSI model defines seven layers for implementing protocols:
2. Data Link
||On The Other Hand
||overclock - to run a CPU, or/and other components, at a speed faster than their rated ability. Overclocking is a popular technique that helps you get a little more performance from a system. The risks involved are overheating, stability issues and shorter lifespan of the components involved. In other words, (especially since you're reading the definition) you should become more familiar with all the pros and cons before attempting it.
||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 220.127.116.11) 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.
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