Agilent Technologies J3919A Convergence Sublayer Indicator CSI, CRC Cyclic Redundancy Check

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.

140