Wide-Area Networks - CCIE Routing and Switching Exam Certification Guide - page 249

QoS Components Table 5-14

Name of Component Description

AAL The ATM adaptation layer identifies traffic categories based on end-to-end

timing relationships, bit arrival rate, and connection or connectionless
operation.

Ingress Policing Prevents the originating device from sending cells faster than the VC can

transport them. UPC prevents the network from becoming congested.

FGCRA Frame Based Generic Cell Rate Algorithm.

If a cell is discarded, PPD ensures that all subsequent cells in the frame are
discarded, except the last cell.
If the first cell of a frame must be discarded, EPD allows the entire frame,
including the last cell, to be discarded.

ATM Cell Format Table 5-15

Name of Field Description

GFC The generic flow control field is not currently used and is always set to the

value 0000.

VPI The virtual path identifier identifies a virtual path connection.

VCI The virtual channel identifier, along with the VPI, uniquely identifies a cell as

belonging to a specific virtual connection.

PTI The payload type identifier identifies the cell as user data or a management cell.

The PTI contains the EFCI bit and the end of frame bit.

CLP The cell loss priority bit identifies the cell as being high or low priority.

HEC The header error control field does error checking on the cell header.