Panasonic FP-D250 User Manual page 591

HDLC (High level Data Link Control) An ISO standard set of protocols for carrying
data over a link with error and flow control. Similar to IBM's SDLC, versions of HDLC
are under development for multipoint lines. The ITU-TS later adapted HDLC for its
Link Access Protocol used for X.25 networks. It is a bit-oriented data link control
procedure under which all data transfer takes place in frames. Each frame ends with
a frame check sequence for error detection. There is a control field at the start of
each frame that allows error detection, and data link setup and data link termination.
HDLC is, in fact, a misnomer, as it is not a high level protocol.
HLMS (Heterogeneous LAN Management Specification) Network management
specification developed by IBM and 3Com. It provides an underlying structure for
the development of network management products which can function with a variety
of network operating systems and adapter cards.
Heterogeneous networking The networking of computers from different vendors,
or the running of different operating systems.
Host processor A minicomputer or mainframe attached to a network providing
services to network users.
Hot fixing The ability to detect and mark bad sectors of a disk, then assign alternate
disk sectors during routine LAN operation. This automatically updates the original
defect map.
Hot swap The ability of a device to have parts removed after, for example, a slot-in
card or fan failure, without affecting its operation. Many of today's hubs offer hot
swapping without bringing down the network to charge a component.
Hub The center of a star topology network or cabling system. A multi-node network
topology that has a central multiplexer with many nodes feeding into and through the
multiplexer or hub. The other nodes do not usually directly interconnect. LAN hubs
are increasingly popular with the growth of structured cabling and the need for LAN
management.
Brouter or Hybrid Bridge/Router Network interconnection device with a standard
mode of operation as a router. It can support multiple OSI Layer Three routing
protocols, but also supports bridging capabilities for network traffic that cannot be
routed - non-routable traffic.
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