Agilent Technologies J3972A - Manual (Page 160)

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Convergence Sublayer
The AAL is divided into two sublayers: the convergence sublayer and the
segmentation and reassembly sublayer (SAR). These two sublayers convert
whatever user data is to be transmitted into 48-byte cell payloads while
maintaining the integrity and a certain amount of identity of the data involved.
The result of each sublayer process is a Protocol Data Unit (PDU). The CS-PDU
is variable in length and is determined by the particular AAL and the length of the
higher layer data block passed to it. The SAR-PDU is always 48 bytes long to fit
in the payload of an ATM cell.
Convergence Sublayer Indicator (CSI)
The Convergence Sublayer Indicator (CSI) is a 1-bit field in the AAL-1 cell
format that handles clock recovery.
Convergence Sublayer Protocol Data Unit (CS-PDU)
A Convergence Sublayer Protocol Data Unit (CS-PDU) is a sublayer of the AAL.
See also Convergence Sublayer.
CRC (Cyclic Redundancy Check)
A mathematical algorithm to derive the frame check sequence (FCS) in bit-
oriented link protocols or the block check characters in character-oriented
protocols.
Cross Cell PRBS
A PRBS pattern inserted in successive cell payloads, crossing payload boundaries.
CSMA/CD (Carrier Sense Multiple Access/Collision Detection)
The network access-control mechanism that is based on collisions and utilized by
Ethernet networks. On contention-based networks, like Ethernet networks, each
station must detect an idle network prior to transmitting. If more than one station
transmits simultaneously, a collision occurs, all stations are notified, and the
colliding stations try retransmitting after waiting a random amount of time.
Customer Premises Equipment (CPE)
Customer owned equipment used to terminate or process information from the
public network. For example, a T1 multiplexer or a PBX.