- RARP (Reverse Address Resolution Protocol) The TCP/IP protocol a diskless machine uses at startup to find its IP address.
- RD running disparity
- Reconfiguration The process of physically altering the location or functionality of network or system elements. Automatic configuration describes the way sophisticated networks can readjust themselves in the event of a link or device failing, enabling the network to continue operation.
- Red Book The 1984 compilation of the ITU-TS's standards for telecommunications, including some for ISDN.
- Redirect A packet switching function that routes a call to an alternative network address if the link to the original network is not available. It is carried out by the end point switches.
- Redundancy Otherwise known as fault-tolerance, in data transmission, this refers to characters and bits that can be removed from a transmission without affecting the message. Ir data processing and data communications, it means providing backup for components: should one of them fail, the system continues to run without operation. Total redundancy is usually impractical, but financial institutions and other organizations with mission-critical applications attempt to install a high level of redundancy on the basis that downtime loses money, lives, depending on the business.
- Redirector A LAN device driver that translates operating system requests into network events and transmits them to the right protocol stack.
- Regeneration A method of boosting a digital signal. Remote bridge LAN-to-LAN bridge that links geographically distant LANs across a wide area link.
- Remote Control The Zenith Radio Corporation was the company behind the first TV remote control in 1995 nicknamed "lazy bones". (Source: Langscheidt)
- Repeater A device that extends the maximum length of cable that can be used in a single network. In fiber networks, it is an optoelectrical module that receives an optical signal and converts it into an electrical form.
- RFC (Request For Comment) Document series begun in 1969 describing the Internet suite of protocols and related experiments.
- RFI radio frequency interference
- RPC (Remote Procedure Call) A means of communication between two tasks running on separate machines linked by a LAN. One machine can request a service, typically computation, from the other, by executing a high level request known as a language procedure call. RPCs are an underlying architectural element of distributed processing and client/server computing.
- RPL (Remote Program Load) Starting a computer and loading the operating system into memory when the operating system software is provided by a server on the network.
- RIN relative intensity noise
- Ring topology A layout scheme in which the network takes the form of a closed loop with the devices attached into the ring. Every workstation is linked to two others, one on each side. All data is passed from node to node in one direction only, each PC acting as a repeater for the next one in the loop. Response time is determined by the number of stations on the ring - the more there are, the slower it works. If one PC fails, the loop is broken, though most rings have self-healing capacity to reconfigure and continue operation. IBM's Token passing ring ensures that the failed station is removed and its neighbors are then directly connected.
- Ring in and Ring out Token Ring connectors on the MSAU connecting the unit to trunk cabling. The Wrap feature is implemented at these interfaces.
- RIP (Routing Information Protocol) The protocol used by Berkeley 4BSD Unix systems to exchange routing information among a small group of computers. Implemented by the Unix program "routed", RIP is derived from an earlier protocol of the same name developed at Xerox.
- RJ11 Popular name for the standard four-wire modular connector for phone connections.
- RJ45 Popular 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.
- Rlogin (Remote Login) The service offered by Berkeley 4BSD Unix systems that allows users of one machine to connect to other Unix systems across an internet and interact as if their terminals connected to the machines directly. Although Rlogin offers essentially the same service as Telnet, it is superior because the software passes information about the user's environment to the remote machine.
- RMON (Remote Monitoring) SNMP specification for multivendor statistics-gathering by a standards-based (de facto SNMP) management station from de facto standard (RMON)-compliant devices.
- Roaming The ability of a mobile communications device to move freely from one part the whole of a network operator's system or another.
- ROFL radial overfilled launch
- Router Network interconnector device operating at OSI Network Layer (Level Three) that supports a particular Network Layer protocol and related stack, such as TCP/IP, DecNet, XNS, SNA, OSI IP, IPX. These days routers tend to support multiple protocols by a variety of methods, such as Protocol Independent Routing. A router can be used to link LANs together locally or remotely as part of a WAN. A network built using routers is often termed an internetwork.
- Routing Process of delivering a message across one or more networks via the most appropriate path.
- Routing table Information stored within a router that contains network path and status information. It is used to select the most appropriate route to forward information along.
- RS standards Laid down by the EIA, RS232c approximates to V.24/28; RS422 to V.11; RS423 to V.10 and RS449 to V.36.
- RS232-C An EIA standard which is the most common way of linking data devices together. An interface for linking DCEs and DTES, it defines the electrical characteristics of the signals from such devices. RS232 is suitable for both synchronous and asynchronous communications and specifies a 25-pin connector, traditionally the DB-25. 20 of the pins carry out routine system operation while the rest are reserved for modem testing or unallocated. For this reason it is never safe to assume that two RS232 devices will work together. Newer, more compact RS232 interfaces have nine pins only and an adapter card is needed. It is functionally similar to the ITU-TS's V.24 and V.28 standards.
- RS422 EIA recommended standard to extend the RS232 50ft limit. It is most commonly implemented on 25-pin connectors (DB-25s) and is electrically compatible with the ITU-TS V.11 standard.
- RS423 The EIA recommended standard for cable lengths that extend the RS232 50ft limit. It was introduced in tandem with RS422 but is not widely used. Electrically compatible with the ITU-TS's V.10 Recommendation.