HP 316095-B21 - StorageWorks Edge Switch 2/24 Manual page 13

Glossary
enhanced availability feature
EAF. A backup field-replaceable unit (backup FRU) that is ordered and installed to provide
redundancy and reduce disruption in case of failure.
Enterprise Systems Architecture
ESA™. A computer architecture introduced by IBM in 1988 as ESA/370. The architecture
added access registers to improve virtual memory management and increase storage from 2
gigabyte to 6 terabytes. The architecture was enhanced with the introduction of ESA/390 in
1990.
Enterprise Systems Connection
ESCON™. An IBM architecture, technology, and set of products and services introduced in
1990 that provides a dynamically connected environment using fiber-optic cables as the data
transmission medium.
Enterprise Systems Connection Director
ESCON™ Director. A device that provides connectivity capability and control for attaching
any two links to each other through the ESCON channel. Specifically, any of the hardware
devices provided for interconnecting IBM-compatible mainframe equipment through the
proprietary ESCON channel connection. IBM's model numbers for ESCON directors include
the 9031 and 9033.
E_Port
See expansion port.
error-detect time-out value
(E_D_TOV) — User-specified value that defines the time a director or switch waits for an
expected response before declaring an error condition.
error message
Software message that indicates an error was detected. See also information message and
warning message.
Ethernet
A widely implemented local area network (LAN) protocol that uses a bus or star topology and
serves as the basis for the IEEE 802.3 standard, which specifies the physical and software
layers. Baseband LAN allows multiple station access to the transmission medium at will
without prior coordination and which avoids or resolves contention.
Ethernet hub
A customer-supplied device used to LAN-connect the HAFM server and the directors it
manages.
Directors and Edge Switches Glossary 13