IBM SAN16B-2 User Guide - Page 72
BB_credit. - system storage
UPC - 000435819895
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asynchronous transfer mode (ATM). A method of transmission in which the sending and receiving of data is controlled by control characters such as a start bit and a stop bit, instead of by a timing sequence. ATM. See asynchronous transfer mode. autonegotiation. A universal mechanism to exchange network capabilities between two Ethernet nodes. The exchange takes place at power-up (or link reset) time. It automatically establishes a link that takes advantage of the highest common denominator of the mutual capabilities of the two Ethernet nodes. The universal mechanism negotiates capabilities that include link speed, PHY types, and full duplex or half duplex. autoranging. A power supply that accommodates different input voltages and line frequencies. AW_TOV. See arbitration wait timeout value. B backup FCS switch. The switch or switches assigned as backup in case the primary fabric configuration server (FCS) switch fails. See also fabric configuration server switch and primary FCS switch. bandwidth. (1) The total transmission capacity of a cable, link, or system. Usually measured in bits per second (bps). (2) The range of transmission frequencies available to a network. See also throughput. basic input/output system (BIOS). Code that controls basic hardware operations, such as interactions with diskette drives, hard disk drives, and the keyboard. BB_credit. See buffer-to-buffer credit. beacon. When all the port light-emitting diodes (LEDs) on a switch are set to flash from one side of the switch to the other, to enable identification of an individual switch in a large fabric. A switch can be set to beacon by a CLI command or through Web Tools. beginning running disparity. The disparity at the transmitter or receiver when the special character associated with an ordered set is encoded or decoded. See also disparity. BER. See bit error rate. BIOS. See basic input/output system. BISR. Built-in self-repair. BIST. Built-in self-test. bit error rate (BER). The rate at which bits are expected to be received in error. Expressed as the ratio of error bits to total bits transmitted. See also error. blade. A component that provides application-specific services and components. A blade is typically a hot swappable hardware device. block. As applies to Fibre Channel, upper-level application data that is transferred in a single sequence. boot code. Software that initialized the system environment during the early phase of the boot-up process. For example, boot code might determine the amount of available memory and how to access it. boot flash. Flash memory that stores the boot code and boot parameters. The processor runs its first instructions from boot flash. Data is cached in random access memory (RAM). British thermal unit (Btu). The amount of heat required to raise a pound of water by 1 degree Fahrenheit. broadcast. The transmission of data from a single source to all devices in the fabric, regardless of zoning. See also multicast and unicast. Btu. See British thermal unit. buffer-to-buffer credit. The number of frames that can be transmitted to a directly-connected recipient or within an arbitrated loop. Determined by the number of receive buffers available. See also buffer-to-buffer flow control. buffer-to-buffer flow control. Management of the frame transmission rate in either a point-to-point topology or in an arbitrated loop. See also buffer-to-buffer credit. C CAM. Content addressable memory. cache. A buffer that contains frequently accessed instructions and data; it is used to reduce access time. cascade. Two or more interconnected Fibre Channel switches that can build large fabrics. Switches can be cascaded up to 239 switches, with a recommended maximum of seven inter-switch links (no path longer than eight switches). See also fabric and inter-switch link. central processing unit (CPU). The part of a computer that includes the circuits that control the interpretation and running of instructions. A CPU is the circuitry and storage that executes instructions. Traditionally, the complete processing unit was often regarded as the CPU, whereas today the CPU is often a microchip. In either case, the centrality of a processor or processing unit depends on the configuration of the system or network in which it is used. 50 SAN16B-2 Installation, Service, and User's Guide