3Com 7000 manual Glossary

GLOSSARY 131

C

call An association between two or more users or between a user and a network entity that is established by the use of network capabilities. This association may have zero or more connections.

cell An ATM Layer protocol data unit (PDU) characterized by fixed, rather than variable, length payloads.

cell delay variation A quantification of cell clumping for a connection. The cell clumping CDV (yk), is defined as the difference between a cell’s expected reference arrival time (ck) and its actual arrival time (ak). The expected reference arrival time (ck) of cell k of a specific connection is max[ck-1+T,ak]. T is the reciprocal of the negotiated peak cell rate.

cell loss ratio In a network/network element, cell loss ratio is (1-x/y), where y is the number of cells that arrive in an interval at the ingress of the network/network element; and x is the number of these y cells that leave at the egress of the network/network element.

CoreBuilder 7000 The 3Com CoreBuilder 7000/7000HD switch is a high-performance, modular ATM switch.

CLP Cell Loss Priority. A bit in the ATM cell header indicating that if there is a need to discard a cell, the cell with the CLP bit marked is to be discarded.

CLR Cell Loss Ratio. CLR is a negotiated QoS parameter and acceptable values are network specific. The objective is to minimize CLR provided the end-system adapts the traffic to the changing ATM layer transfer characteristics. The Cell Loss Ratio is defined for a connection as: Lost Cells/Total Transmitted Cells.

collision Overlapping transmission of two or more nodes onto media. All data is unusable.

connection An ATM connection consists of the concatenation of ATM Layer links in order to provide an end-to-end information transfer capability to access points.

connectionless A form of packet-switching that relies on global addresses in each communications packet rather than on predefined virtual circuits.