RAID:-

Acronym for redundant array of inexpensive disks, In networking and mission-critical applications, a method of using several hard disk drives (often SCSI or Integrated Drive Electronics (IDE) drives) in an array to provide fault tolerance in the event that one of more than one drive fail. Each of the different levels of RAID is designed for a specific use:

• RAID 0 : Data is striped over one or more drives, but there is no redundant drive. RAID 0 provides no fault tolerance because the loss of a hard disk means a complete loss of data. Some classification schemes omit RAID 0 for this reason.

• RAID 1 : Two hard disks of equal capacity duplicate or mirror each other's contents. One disk continuously and automatically backs up the other disk. This method is also known as disk mirroring or disk duplexing, depending on whether one or two independent hard-disk controllers are used.

• RAID 2 : Bit-interleaved data is written across several drives, and then parity and error-correction information is written to additional separate drives. The specific number of error-correction drives depends on the allocation algorithm in use.

• RAID 3 : Bit-interleaved data is written across several drives, but only one parity drive is used. If an error is detected, the data is reread to resolve the problem. The fact that data is reread in the event of an error may add a small performance penalty.

• RAID 4 : Data is written across drives by sectors rather than at the bit level, and a separate drive is used as a parity drive for error detection. Reads and writes occur independently.

• RAID 5 : Data is written across drives in sectors, and parity information is added as another sector, just as if it were ordinary data. There is not much difference in speed or quality among these levels. The appropriate level of RAID for any particular installation depends on network usage. RAID levels 1, 3, and 5 are available commercially, and levels 3 and 5 are proving popular for networks.

Read-After-Write verification:-

A method of checking that data is written to a hard disk correctly. Data is written to the disk, and then read back and compared with the original data still held in memory. If the data read from the disk matches, the data in memory is released. If the data does not match, that block on the disk is marked as bad, and another attempt is made to write the data elsewhere on the disk.

Recursion:-

In programming, the ability of a subroutine to call itself. Recursion is often used when solving problems that repeat the same processing steps. However, some limiting factor must be present; otherwise, the program will never stop running.

Reduced Instruction Set Computing:-

Abbreviated RISC, pronounced "risk." A processor that recognizes only a limited number of assembly-language instructions. RLSC chips are relatively cheap to produce and debug, because they usually contain fewer than 128 different instructions, RISC processors are commonly used in workstations, and they can be designed to run up to 70 percent faster than processors that use complex instruction set computing (CISC).

Remote Boot:-

A technique used to boot a workstation from an image file on the file server rather than   from a local drive attached directly to the workstation.

Remote Connection:-

A workstation-to-network connection, made using a modem and telephone line, that allows data to be sent or received over greater distances than those allowed by conventional cabling. Also known as remote access.

Remote-Control Program:-

A program that allows the user to link two PCs together, so that one of the computers controls the operation of the other. The connection may be over a dedicated serial or SCSI line, a local-area network (LAN), or a modern-to-modem communications link. Each computer runs a copy of the remote-control program.

Remote-control programs are particularly useful for trouble-shooting problems at computers located far from the technical support center, installing or removing demonstration software without needing to visit the customer site, training remote

users, and telecommuting. Popular remote control programs include Symantec's PcAnywhere, Microcom's Carbon Copy, Traveling Software's LapLink for Windows, and Farallon's Timbuktu.

Remote Procedure Call:-

Abbreviated RPC. A set of procedures used to implement client/server architecture in distributed programming. RPC describes how an application initiates a process on another network node and how it retrieves the appropriate result.

Remote Resources:-

Any device not attached to the local node, but available through the network.

Repeater:-

A simple hardware device that moves all packets from one local-area network (LAN) segment to another by regenerating, retiming, and amplifying the electrical signals. The main purpose of a repeater is to extend the length of the network transmission medium beyond the normal maximum cable lengths.

Requester:-

Special software loaded onto a networked workstation to manage communications between the network and the workstation. This software may also be referred to as a shell, redirector, or client, depending oh the networking system in use.

RESET ROUTER:-

A Novell NetWare server utility used to reset or recreate the routing table in the file server. Router tables are automatically reset every two minutes, so this command is not used often.

Response Time:-

The time lag between sending a request and receiving the data. Response time can be applied to a complete computer system, as in the time taken to look up a certain customer record, or to a system component, as in the time taken to access a specific cluster on disk.

RFS:-

Abbreviation for Remote File Service. A distributed file system network protocol that allows programs running on a computer-to use network^ resources as though they were local. Originally developed by AT&T, RFS has been incorporated as a part of UNIX System V Interface Definition.

Rights:-

The privileges granted to a user or a group of users by the network administrator. Rights determine the operations that users can perform on the system. For example, Novell NetWare 3.x directory system rights are supervisor, read, write, erase, create, modify, access control, and tile scan. In NetWare 4.x, NDS rights are grouped as directory rights, file rights, object rights, and property rights.

Ring Network:-

A network topology in the form of a closed loop or circle, with each node in the network connected to the next. Messages move in the direction around the system.

RJ-11:-

A commonly used modular telephone connector. RJ-11 is a four wire (two-pair) connector most often used for voice communications.

Router:-

An intelligent connecting device that can send packets to the correct local area network (LAN) segment to take them to their destination. Routes link LAN segments at the network layer of the ISO/OS1 model for computer-to-computer communications The networks connected by routers can use similar or different networking protocols. A router may be one or more of the following types:

• Central router: Acts as a network backbone, connecting many LANs together.

• Peripheral router: Connects individual LANs to either a central router or to another peripheral router.

• Local router: Operates within the limits of its LAN driver's cable-length limitations.

• Remote router: Connects beyond its device driver limitations, perhaps through a modem or remote connection.

• Internal router: Part of a network file server.

• External router: Located in a workstation on the network.

Routing Protocol: -

The protocol that enables routing by the use of a specific routing algorithm that determines the most appropriate path between the source and destination nodes.

Run-Time Version: -

A special, limited-capability release of software bundled with a single product that allows that product to run, but does not support any of the other applications capable of running in that same environment. The run-time version provides some but not all the features of the full product.