3Com 7000 manual

GLOSSARY 133

quality of service class makes use of explicit forward congestion indication.

Ethernet A CSMA/CD, 10 Mbps, local area data network, developed by Xerox Corporation. It is one of the most popular baseband LANs in use.

ELAN name The name assigned an ELAN (Emulated Local Area Network).

ESI End System Identifier. This identifier distinguishes multiple nodes at the same level in case the lower peer group is partitioned.

external clock Clock that comes through an RX channel into an on-board port.

external clock source The on-board port that supplies the external synchronization clock, port which is distributed to all other on-board 8-port ports. Only a single

port of this type can exist in a box. Only on-board ports can function as an external clock source port.

F

flooding This is an advertising mechanism in PNNI and ensures that each node maintains an identical topology database.

foreign address An address that does not match any of a given node’s summary addresses.

H

horizontal links A link between two logical nodes that belong to the same peer group.

header Protocol control information located at the beginning of a protocol data unit.

HEC Header Error Control. Using the fifth octet in the ATM cell header, ATM equipment may check for an error and correct the contents of the header. The check character is calculated using a CRC algorithm allowing a single bit error in the header to be corrected or multiple errors to be detected.

hello packet A type of PNNI routing packet that is exchanged between neighboring logical nodes.

I

IEEE 802.3 IEEE standard for Ethernet local area networks.