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5536 PRI RAS Communications Controller Users Guide 207
Excess burst size (Be) The maximum amount of uncommitted
data (in bits) in excess of Bc that a frame relay network can attempt to
deliver during a time interval Tc. This data (Be) generally is delivered
with a lower probability than Bc. The network treats Be data as discard
eligible. See also committed burst size (Bc).
Exchange identification (XID) A specific type of basic link unit that
is used to convey node and link characteristics between adjacent nodes.
XIDs are exchanged between link stations before and during link acti-
vation to establish and negotiate link and node characteristics. They are
exchanged after link activation to communicate changes in these char-
acteristics.
FCC (Federal Communication Commission) The U.S. government
agency that regulates the telephone industry.
FECN See Forward explicit congestion notification (FECN).
Firmware A computer program or software stored permanently in
flash memory, read-only memory (ROM), programmable read-only
memory (PROM), or stored semi-permanently in erasable programma-
ble read-only memory (EPROM).
Forward explicit congestion notification (FECN) A bit set by a
frame relay network to notify an interface device (DTE) that conges-
tion avoidance procedures should be initiated by the receiving device.
See also BECN.
Frame Relay A wide area networking connection to leased lines,
providing multiple permanent virtual circuits or data link connections
within the same physical access line.
Gateway Equipment that provides interconnection between two
networks with different communications protocols. Two examples are
packet assembler/disassemblers and protocol converters. Gateways
operate at the 4th through 7th layers of the Open Systems Interconnec-
tion model. Contrast with bridge, router, repeater.
HDB3 (High Density Bipolar 3) A method of digitally encoding
data on a link. A modified form of AMI used in Europe.
HDLC (High-level Data Link Control) A International standard
communications bit oriented protocol developed by the International
Standards Organization. HDLC manages synchronous, code transpar-
ent, serial information transfer over a link connection.
host name A unique name that identifies each host machine on a
network.
IEC International Electrotechnical Commission.