IBM OPTIONS ATM OC-3c, User Manual

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2 G
LOSSARY
Byte
An Octet or 8 bits of data.
Cell
Basic ATM transmission unit. It is a 53-byte packet,
consisting of a 5-byte header and a 48-byte payload.
User traffic is segmented into cells at the source and
reassembled at the destination.
Cell Header
The 5-byte ATM cell header contains control
information regarding the destination path and flow
control.
More specifically it contains the following fields: GFG,
VPI, VCI, PTI, CLP and HEC.
CLP
Cell Loss Priority — A 1-bit field in the ATM cell
header that corresponds to the loss priority of a cell.
Lower priority (CLP = 1) cells can be discarded under
congestion situations.
connectionless
Communications service where packets are
transferred from source to destination without the
need for a pre-established connection.
connection oriented
Communications service where an initial connection
between the end points (source and destination) must
be set up prior to data transmission. ATM and Frame
Relay are Connection Oriented.
E.164
An 8-byte address format. In ATM it is typically used
in public networks and it is provided by the
telecommunication carriers, while 20-byte NSAP
(Network Service Access Point) format addresses are
used within private networks.
EFCI
Explicit Forward Congestion Indication — A 1-bit field
in the PTI that contains information about whether
congestion at an intermediate node has been
experienced. The EFCI bit is set when a threshold (for
example, buffer contents) has been exceeded.
ELAN
Emulated LAN — See LAN Emulation .
firewall
Isolation of LAN segments from each other to protect
data resources and help manage traffic.
Flash EPROM
EPROM (Erasable Programmable Read-Only Memory)
technology providing non-volatile storage that can be
electrically erased in the circuit and reprogrammed;
developed by Intel and licensed to other
semi-conductor companies.
Flow Control
A method used in networking for congestion
avoidance and traffic regulation.