Glossary - R

RAM

Random Access Memory (hardware, memory)
The most common computer memory, the contents of which can be altered at any time.
Random Access Memory is the temporary memory a computer uses to store data and process information. The more RAM a computer has, the more data a computer can manipulate. The contents of RAM are cleared when you turn off the computer.
Any memory in which data can be written/read to/from arbitrary locations: generally semiconductor memory (Static RAM retains data as long as the memory receives power; dynamic RAM requires all memory locations to be accesses (refreshed) periodically; and Non-Volatile memory retains data even without power).
"Random" as opposed to "sequential" refers to the fact that any randomly chosen bit of information can be accessed immediately and therefore rapidly. Most RAM is organized in a rectangular array of word lines and bit lines. Any code in the process of execution, and as much as possible of the data which that code requires, are stored in RAM.
Until the late 1960's, the RAM in most computers was in the form of arrays of small ferrite "cores". A bit was encoded by the direction of magnetization of a core (that's the origin of the term "core dump"). The first great success of MOS technology was the rapid take-over of the core memory market by SRAM. SRAM, DRAM and SDRAM are still the overwhelmingly dominant forms of central RAM.

RBOC

Regional Bell Operating Company
One of the seven local service telephone companies that resulted from the break-up of AT&T in 1984.

RD

Routing Domain (routing)

RDI

Remote Defect Indication (ATM)
(UNI Fault Management) One of the OAM function types used for fault management. See also AIS, CC.

RDF

Rate Decrease Factor
A factor by which a source should decrease its transmission rate if there is congestion. See also RIF.

RED

Random Early Detection
A technique to avoid network congestion during peak traffic loads by holding lower-priority traffic in order to serve higher--priority traffic first. RED works well with RSVP to ensure consistent QoS across the network.

Renater (network, Internet)

French ISP for Education and Research.

Repeater (network)

A hardware device that regenerates LAN signals to extend the length, topology or interconnectivity of the network, or converts signals between media at the same time. See also hub.

Reverse Engineering

The process of analysing an existing system to identify its components and their interrelationships and create representations of the system in another form or at a higher level of abstraction. Reverse engineering is usually undertaken in order to redesign the system for better maintainability or to produce a copy of a system without access to the design from which it was originally produced.
For example, one might take the executable code of a computer program, run it to study how it behaved with different input and then attempt to write a program oneself which behaved identially (or better). An integrated circuit might also be reverse engineered by an unscrupulous company wishing to make unlicensed copies of a popular chip.

RFC

Request for Comment
The development of TCP/IP standards, procedures and specifications is done via the mechanism of RFCs. These are documents that progress through several development stages, under the control of the IETF, until they are finalized or discarded.

RFI

Request for Information (network)
A document prepared by a potential user of products and/or services to solicit information from a provider regarding that provider's products, capabilities, prices, and services. An RFI is generally less restrictive than an RFP and the responses are not binding on the responder.

Radio Frequency Interference (physical level)

RFP

Request for Procurement/Pricing (network)
A document prepared by a potential user of products and/or services to solicit information from a provider regarding that provider's products, capabilities, prices, and services. An RFP is generally more focused than an RFI and the responder may be bound by any information in the response, including pricing.

RGB

Red, Green, Blue (graphics)
The three colours of light which can be mixed to produce any other colour. Coloured images are often stored as a sequence of RGB triplets or as separate red, green and blue overlays though this is not the only possible representation (see CMYK and HSV). These colours correspond to the three "guns" in a colour cathode ray tube and to the colour receptors in the human eye.
Often used as a synonym for colour, as in "RGB monitor" as opposed to monochrome (black and white).

RIF

Rate Increase Factor
A factor by which a source can increase its transmission rate if the RM cell indicates no congestion. This can result in a Additive Cell Rate (ACR). See also RDF.

Ring Topology

A LAN topology that connects each node in a ring to create a circle; each node acts as a repeater to regenerate the signal; each node must be able to recognize its address since each signal passes through every node on the ring.

RIP

Routing Information Protocol (protocol, routing, network layer)

RIPE (network, Internet)

A collaboration between European networks which use the TCP/IP protocol suite.

RISC

Reduced Instruction Set Computer (processor, hardware)

RJ - RJ numbers

Registered Jack numbers
numbers applied to types of connectors often used in UTP wiring. Examples: RJ11, RJ45. Borrowed from voice telecommunications industry.

RJ11

Name for the standard four-wire modular connector for phone connections.
Jack and/or connector typically used with copper cable having two twisted pairs, usually unshielded twisted pair category 3 (UTP 3) or category 5 (UTP 5). Used for telephony, 10Base-T and 100Base-Tx Ethernet LAN, and Token Ring LANs.

RJ45

Registered Jack
Name for the eight-pin modular connector in the 10BaseT standard for UTP connections to workstations or smart wiring hubs. The actual connector is described in ISO standard 8877. They are inexpensive and easy to install onto UTP cable.

RM

Resource Management (ATM)
The management of critical network resources, such as bandwidth and buffers, at the node level. A special ATM cell with the PTI field set to 6 and containing a series of fields in the 48-byte payload. Transmitted every nth cell to regulate and control traffic flow on a given ABR-based virtual circuit.

RNIS

French ISDN.

ROM

Read Only Memory (hardware, memory)

Router (network)

A device (or interface) which forwards traffic between networks. The forwarding decision is based on network layer information and routing tables, often constructed by routing protocols. The router provides more functionality than a bridge for example network management capabilities such as load balancing, partitioning of the network, user statistics, communication priority, and troubleshooting tools that allow network managers to detect and correct problems.

Routing

1. The assignment of a path by which a message will reach its destination.
2. The forwarding of a message unit along a particular path as determined by the parameters carried in the message.
3. Routing may also include the translation of messages between LAN segments that use different LLC protocols. See LLS, Bridging, Routing table.

• Dynamic: The establishment of a path through a network at the time the path is required based on information present in a connection request or in the message being transmitted.
• Static: The establishment of a path through a network in advance of any traffic demands via the use of pre-defined routes.

Routing Table

The information in any given network node that is used to determine the route of a received message so that it may be transmitted on the proper next segment of the path to its destination.

RPA

Remote Passphrase Authentification (network)

RPC

Remote Procedure Call (operating system, unix, network, Internet)
A TCP/IP mechanism that provides a standard for initiating and controlling processes on remote or distributed computer systems.
See IETF, RFC.

RS-232 (communications, standard)

The most common asynchronous serial line standard. RS-232 is the EIA equivalent of ITU-T V.24 and V.28. RS-232 specifies the gender and pin use of connectors, but not their physical type. RS-423 specifies the electrical signals. 25-way D-type connectors are common but often only three wires are connected - one ground (pin seven) and one for data in each direction. The other pins are mostly related to hardware handshaking between sender and receiver and to carrier detection on modems, inoperative circuits, busy conditions etc. The standard classifies equipment as either Data Communications Equipment (DCE) or Data Terminal Equipment (DTE). A DCE RS-232 interface should have a female connector and should transmit on pin two and receive on pin three. DTE should have a male connector and should should transmit on pin three (TD) and receive on pin two (RD). Originally DCE was a modem and DTE was either a computer or a terminal. The terminal and computer were connected (via RS-232) to two modems, which were connected via a telephone line. The above arrangement allows a computer or terminal to be connected to a modem with a straight-through (2-2, 3-3) cable. It is not uncommon though to find equipment with the wrong sex connector and/or with pins two and three the wrong way round, requiring the insertion of a cable or adaptor wired as a gender mender or null modem. Such a cable is also required when connecting a computer directly to a terminal or to another computer when not using modems.

RSA (security, cryptography, company)

Rivest, Shamir, Adleman
A public-key cryptographic system which may be used for encryption and authentication. It was invented in 1977 and named for its inventors: Ron Rivest, Adi Shamir, and Leonard Adleman. This is the cryptography system of RSA Data Security, Inc. The RSA algorithm was first described in the paper: [R. Rivest, A. Shamir, L. Adleman, "A Method for Obtaining Digital Signatures and Public-key Cryptosystems". CACM 21,2; 1978]

RSVP

Resource ReSerVation Protocol (network, Internet)
A draft Internet standard, protocol developed for supporting different QoS classes in IP applications (such as videoconference, multimedia). This protocol will allow internetworking devices to communicate with each other and reserve resources from end to end for an application.

RTFM

Read The F*cking Manual (network, Internet)
This acronym is often used when someone asks a simple or common question.

RTS

Request To Send (physical layer)

RTSC

Read The Source Code (network, Internet)
This acronym is often used when a software developer asks a question about undocumented code.

RTT

Round-Trip Time (ATM)
Round-trip time between a source and a device, such as a switch, and it is usually measured in number of cells (which depends on the buffering capabilities of the device). It is used as a window in flow control.

RWM

Read-Write Memory (hardware, memory)
Usually called by the in-principle more ambiguous term RAM.

Rx (network, communications)

Receiver (network, hardware)
A terminal device that includes a detector and signal processing electronics.

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