255-700-019
D-1
PacketStar
™
PSAX 20 Access Concentrator User Guide
, Issue 1
Release 6.3.0
D
ATM Traffic Descriptors
Overview of This Appendix
This appendix describes how each traffic descriptor affects the ATM cell
streams under different traffic conditions. When you create a PVC, you can
select one of several traffic descriptors. The traffic descriptor specifies which
traffic parameters are used for traffic control. It also determines the number
and type of cells that are admitted into a congested queue, and whether
high-priority cells are tagged as low-priority cells when traffic exceeds the
traffic parameter thresholds.
Connections Supporting Traffic Descriptors
The traffic descriptors used in the
PacketStar
Access Concentrator system
software are selected on the user interface windows for the following types of
connections:
•
ATM-to-ATM VCC PVC connection
•
ATM-to-ATM VPC PVC connection
•
Bridge-to-ATM VCC PVC connection
•
Circuit Emulation-to-ATM VCC PVC connection
•
Frame Relay-to-ATM VCC PVC connection
•
In-band ATM PVC connection
•
VBR-to-ATM VCC PVC connection
Traffic Descriptors Supported
The traffic descriptors available for these connections types are as follows
(the values as they appear on the window are shown in parentheses):
•
Best effort (Best-effort)
This traffic descriptor allows the system to attempt to send all cells in a
“best effort” fashion, without specifying traffic parameters, similar to the
AQueMan
algorithm. The Access Concentrator might drop some or all
cells during congestion.
•
Best effort with tagging (Best-effort-tag)
This traffic descriptor allows the system to tag all CLP=0 (high priority)
cells to change them to CLP=1 (low priority) cells, and then attempt to
send all cells in a “best effort” fashion, without specifying any other traffic
parameters, similar to the
AQueMan
algorithm. The network might drop
some or all cells during congestion.