Broadband ISDN: ITU-T standards created to manage high-
bandwidth technologies such as video. BISDN presently employs ATM tech-
nology along SONET-based transmission circuits, supplying data rates
between 155Mbps and 622Mbps and beyond. See also: BRI, ISDN,
Regardless of frame content, the class of Data Link
layer communication protocols that transmits frames. Bit-oriented proto-
cols, as compared with byte-oriented, supply more efficient and trustworthy
full-duplex operation. Compare with: byte-oriented protocol.
Used in routers to put the router into bootstrap mode. Boot-
strap mode then boots the device with an operating system. The ROM can
also hold a small Cisco IOS.
A router that facilitates communication with routers in
different autonomous systems.
Typically defined within Open Shortest Path First (OSPF)
as a router that connected an area to the backbone area. However, a border
router can be a router that connects a company to the Internet as well.
See also: OSPF.
Bridge Protocol Data Unit: A Spanning Tree Protocol initializing
packet that is sent at definable intervals for the purpose of exchanging infor-
mation among bridges in networks.
Basic Rate Interface: The ISDN interface that facilitates circuit-
switched communication between video, data, and voice; it is made up of
two B channels (64Kbps each) and one D channel (16Kbps). Compare with:
PRI. See also: BISDN.
A device for connecting two segments of a network and transmit-
ting packets between them. Both segments must use identical protocols to
communicate. Bridges function at the Data Link layer, Layer 2 of the OSI
Reference Model. The purpose of a bridge is to filter, send, or flood any
incoming frame, based on the MAC address of that particular frame.
Used to find and elect the root bridge in a Layer 2 switched inter-
network. The bridge ID is a combination of the bridge priority and base
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