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List of netowrking, wireless, broadband, satellite, telephony, general computing and other technical terms used throughout the site.
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Term Description
RADIUS RADIUS (Remote Access Dial-Up User Service) is an authentication standard technology, often used to protect access to wireless networks. RADIUS is a user name and password scheme that enables only approved users to access the network; it does not affect or encrypt data. The first time a user wants access to the network, secure files or internet locations, he or she must input his or her name and password and submit it over the network to the RADIUS server. The server then verifies that the individual has an account and, if so, ensures that the person uses the correct password before she or he can get on the network. RADIUS can be set up to provide different access levels or classes of access.
RADSL RADSL (Rate-Adaptive Asymmetric Digital Subscriber Line) is an ADSL implementation that automatically adjusts the connection speed according to the quality of the telephone line, allowing RADSL to function over longer distances than ordinary ADSL.
RAID RAID - Redundant Array of Independent (or Inexpensive) Disks. Type of disk storage configuration often used on servers, where several physical disks are combined into an array for better speed and/or fault tolerance.

RAID 0 (data striping) - file blocks are written to separate drives. Does not provide fault tolerance, because failure of one drive will result in data loss.
RAID 1 (data mirroring) - data is duplicated on two drives either through software or hardware. Provides faster read performance than a single drive and good fault tolerance.
RAID 2 (not used in practice) - data is split at bit level at written to multiple drives.
RAID 3 (requires 3+ drives) - data block is striped at byte level across drives and error correction codes (parity info) is recorder on another drive. Provides fault tolerance but slower writing performance.
RAID 4 - similar to Level 3 but provides faster performance because it uses blocks for striping.
RAID 5 - similar to Level 4 but improves performance by also striping parity info across multiple drives.
RAID 6 - similar to Level 5 but also uses second parity scheme for better fault tolerance.
RAID 7 - proprietary RAID design by Storage Computer Corporation. Faster than other levels because it uses multiple levels of cache and asynchronous I/O transfers.
ransomware Ransomware is a type of malicious software that is installed covertly on a victim's computer and prevents users from accessing their system or files. Typically, ransomware spreads through trojans and locks the users' files/system unless a ransom is paid.

More simple variants just lock the system and display a message demanding payment to unlock it. They are somewhat easier to unlock. More advanced variants actually encrypt files, or, in some cases the entire hard drive or the computer's Master File Table (MFT). Such variants are almost impossible to clean, as they render files inaccessible.

RARP RARP - Reverse Address Resolution Protocol (RFC 903).

RARP is a Link layer networking protocol used by a host computer to obtain its Internet Protocol (IPv4) address when it has available its link-layer address, such as an Ethernet MAC address.
RC4 RC4 is a symetric stream cipher with an arbitrary key size designed by RSA Security, Inc. in 1987. It is essentially a pseudo random number generator, with the output of it being XORed with the data stream to produce encrypted data. The source code for an RC4 algorithm (or a code that produces the same results) was posted on Usenet in 1994. It is fast, it has been extensively analyzed and proven to be secure.

The RS4 cipher is used in SSL (Secure Socket Layer), WEP (Wireless Equivalent Privacy), WPA (Wi-Fi Protected Access), TKIP, MS XBOX, Oracle SQL, Adobe Acrobat, etc.
RCPI RCPI (Received Channel Power Indicator) in 802.11 wireless networking is a measure of the received RF power in a selected channel over the preamble and the entire received frame. Note that a power level metric like RCPI generally can't comment on the quality of the link by itself.

See: IEEE 802.11k-2008
Regedit Regedit is an editor for accessing the Windows registry that is provided with the Windows operating system. It can be accessed from the Start Menu ( START > Run > type "regedit" ). Some of the changes to registry keys/values require rebooting the PC before they take effect.

It is a good idea to star the registry editor as admininstrator (right-click > Run as Administrator), as changes to some of the "hives" require elevation.

Note: Modifying some registry settings can cause serious problems and damage your operating system to a point where it needs to be reinstalled. Make backups and use the information at your own risk.

Again, it is always a good idea to backup the Windows Registry before making changes!
repeater In telecommunications, a repeater is a device that receives a signal and retransmits it, so that the signal can cover longer distances. A repeater can either retransmit it at a higher level/power, or it can simply extend the range by repeating the signal over some obstacles. If placed at the edge of a network, it can extend the coverage area.

In wireless networking, a wireless repeater (a.k.a wireless range extender) takes an existing signal from a wireless router or access point and rebroadcasts it to/from wireless clients to extend the range of the network. It differs from access points in that it is wirelessly connected to all devices on both ends of the connection.
RFC RFCs (Requests for Comments) are the official documents of the Internet Engineering Task Force (IETF) and the Internet Society that specify the details for protocols included in the TCP/IP family.

RFCs are authored by computer scientists and engineers in the form documents describing research, methods, and innovations applicable to the working of the Internet and Internet-connected systems. RFCs are submitted either for peer review or simply to convey new concepts and information. The IETF adopts some of the proposals published as RFCs as Internet standards.

IETF has published over 7000 RFCs, all of which can be viewed at, or RFC-Editor.
RFI RFI (Radio Frequency Interference) - signal interference on the radio frequency electromagnetic spectrum (from 3 KHz to 300 GHz).
RIAA RIAA (Recording Industry Association of America) is a special interest trade group formed in 1952, representing the US recording industry.

The RIAA has been at the heart of the P2P file-sharing controversy, as well as any new technology that can be used to record media content (the VCR for example). RIAA is continuously lobbying and waging an aggressive legal campaign attempting to defend the interests of its members (the larger record labels).
RIR RIR (Regional Internet Registry) is an organization overseeing the allocation and registration of Internet number resources within a particular region of the world. Resources include IP addresses (both IPv4 and IPv6) and autonomous system numbers (for use in BGP routing).

There are currently five RIRs in operation:

American Registry for Internet Numbers (ARIN) for North America and parts of the Caribbean
RIPE Network Coordination Centre (RIPE NCC) for Europe, the Middle East and Central Asia
Asia-Pacific Network Information Centre (APNIC) for Asia and the Pacific region
Latin American and Caribbean Internet Addresses Registry (LACNIC) for Latin America and parts of the Caribbean region
African Network Information Centre (AfriNIC) for Africa
RJ-11 RJ-11 (Registered Jack 11) - a standard connector that is used to connect to the telephone line, the most common telephone jack.
RJ-45 RJ-45 (Registered Jack 45) is a standard connector for the ends of a Category 5 network cable. Though it is similar in apperance to a phone plug (RJ-11), it has 8 wires rather than 6, and is slightly wider.
ROFL Rolling On Floor, Laughing
rootkit rootkit is a type of malicious software that is activated each time your system boots up. Rootkits are generally difficult to detect, since they run before the Operating System has completely booted up.
Router A router is the central switching device in a packet-switched network that directs and controls (routes) the flow of data.

A traditional router routes packets within a single address realm, while a NAT router directs datagrams between different address realms. A NAT router sits on the border between two adress realms and performs such "transparent routing" by modifying addresses in IP headers, so that when packets enter another address realm they can be valid and routed properly.

Routers are differentiated from data communications switches by the ability to perform higher-level functions necessary to the interconnection of different networks.
RPC RPC (Remote Procedure Call) is a protocol that a program can use to request a service from a program located on another computer in a network. RPC helps with interoperability because the program using RPC does not have to understand the network protocols that are supporting communication. In RPC, the requesting program is the client and the service-providing program is the server.

Two newer object-oriented methods for programs to communicate with each other, CORBA and DCOM, provide the same types of capabilities as traditional RPCs.
RSN RSN (Robust Security Network) is a WPA (Wi-Fi Protected Access) replacement built on 802.1x and the AES (Advanced Encryption Standard).
RSS RSS (Really Simple Syndication) is a popular, lightweight XML format designed for sharing headlines, and other web content between sites. It is most often used for gathering and distributing news and other web content.

RSS (Receive-side Scaling) is also a method allowing for parallelized processing of received network packets on multiple processors, while avoiding packet reordering.
RSSI RSSI (Recieved Signal Strength Indicator) is a common name for the received radio signal power level in a wireless network. It is often measured in either decibels (db), or simply numbers between 0 and 100. RSSI can be expressed as either a negative or positive value, however, in both instances smaller values closer to zero indicate a stronger signal.

Some older chipsets used RSSI from 0 to 256, or 0 to 127. Most newer chipsets use 0 to 100.
In 802.11 wireless, RSSI is being replaced by RCPI (Received Channel Power Indicator).
RTT RTT ( RoundTrip Time ) is the amount of time it takes for a packet of data to get from one designated point to another and back to the sender. RTT is usually used to measure latency.
runt In Ethernet networks, any frame shorter than the minimum 64 bytes but with a valid CRC is considered a runt.

See also: jabber
RWIN RWIN (TCP Receive Window) is a buffer that determines how much data the receiving computer is prepared to get at one time.

The sending side will only send data up to the size of the RWIN, and wait for acknowledgement before sending additional packets.

A RWIN value that's too large will result in greater loss of data if a packet is lost or damaged. A too small RWIN will be very slow, as each packet will have to be acknowledged before the next packet is sent.

RWIN is one of the most important parameters in tweaking any TCP/IP connection.
Term Description
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