IBM SAN16B-2 User Guide - Page 80

primitive signal. A part of an ordered set that indicates events. See also ordered set. principal switch. The switch that assumes the responsibility to assign domain IDs. The role of principal switch is negotiated after a "build fabric" event. private device. A device that supports arbitrated loop protocol and can interpret 8-bit addresses, but cannot log into the fabric. private loop. An arbitrated loop that does not include a participating fabric loop port (FL_port). private key. The secret half of a key pair. private loop direct attach (PLDA). A subset of fibre channel standards for the operation of peripheral devices. private NL_port. A node loop port (NL_port) that communicates only with other private NL_ports in the same loop and does not log into the fabric. protocol. A defined method and a set of standards for communication. public device. A device that supports arbitrated loop protocol, can interpret 8-bit addresses, and can log into the fabric. public loop. An arbitrated loop that includes a participating fabric loop port (FL_port), and can contain both public and private node loop ports (NL_ports). public NL_port. A node loop port (NL_port) that logs into the fabric, can function within either a public or private loop, and can communicate with either private or public NL_ports. Q quad. A group of four adjacent ports that share a common pool of frame buffers. QuickLoop. (1) A software feature that makes it possible to allow private devices within loops to communicate with public and private devices across the fabric through the creation of a larger loop. (2) The arbitrated loop created using this software. A QuickLoop can contain a number of devices or looplets; all devices in the same QuickLoop share a single arbitrated loop physical address (AL_PA) space. QuickLoop mode. A hardware translative mode that allows private devices to communicate with other private devices across the fabric. See also hardware translative mode and standard translative mode. 58 SAN16B-2 Installation, Service, and User's Guide R RAID. See redundant array of independent disks. RAM. See random access memory. random access memory (RAM). A temporary storage location in which the central processing unit (CPU) stores and executes its processes. R_A_TOV. See resource allocation timeout value. read only memory (ROM). Memory in which stored data cannot be changed by the user except under special conditions. receiver ready (R_RDY). A primitive signal indicating that the port is ready to receive a frame. redundant array of independent disks (RAID). A collection of disk drives that appear as a single volume to the server and are fault tolerant through mirroring or parity checking. registered state change notification (RSCN). A switch function that allows notification of fabric changes to be sent from the switch to specified nodes. remote fabric. A fabric that spans across wide area networks (WANs) by using protocol translation (a process also known as tunneling) such as fibre channel over asynchronous transfer mode (ATM) or fibre channel over Internet protocol (IP). remote switch. A optional feature for long distance fabrics, requireing a Fibre Channel to ATM or SONET gateway. request rate. The rate at which requests arrive at a servicing entity. See also service rate. resilience. A fabric's ability to adapt to or tolerate a failure of a component within the fabric. resilient core. A single fabric that uses two or more switches as a core to interconnect multiple edge switches. Synonymous with dual-core fabric. resource allocation timeout value (R_A_TOV). Used to time out operations that depend on the maximum possible time that a frame can be delayed in a fabric and still be delivered. This value is adjustable in one microsecond increments from 10-120 seconds. resource recover timeout value (RR_TOV). The minimum time a target device in a loop waits after a loop initialization primitive (LIP) before logging out a small computer systems interface (SCSI) initiator. See also error detect timeout value and resource allocation timeout value. RLS probing. Read link status of the arbitrated loop physical addresses (AL_PAs).