255-700-025
3-15
PacketStar
™
Access Concentrator 60 User Guide
, Issue 1
Release 6.3.0
Chapter 3 System Features
AC 60 Software Features
If zero errors are detected by the AC 60 system for a user-selectable interval
of 10 seconds, 30 seconds, 1 minute, or 5 minutes (or not allowed), the
system restores the primary link.
AQueMan™
Algorithm
With ATM, predictable QoS is achieved for all applications by the
transmission of voice, video, and data using short, fixed-length cells
interleaved at guaranteed bit rates. The guaranteed bit rates are implemented
by assigning ATM Forum-established QoS classes for each type of data to be
transferred. The following attributes are considered in assigning an ATM
service class:
•
Cell transfer delay characteristics
•
Cell loss ratio
•
Type of connection required
•
Timing or synchronization of the source and destination
AQueMan
™
manages traffic while supporting ATM Forum classes of service.
This adaptive algorithm allocates bandwidth by statistically multiplexing
traffic within two sets of queues according to weighted priorities. One set of
queues addresses avoidance of cell loss, which is normally a concern for data
traffic, while the other manages cell transfer delay, which is critical to voice
and some video traffic. Within each set of queues,
AQueMan™
assigns
internal priorities even more specialized than the ATM Forum class
definitions. Generally, the lower the assigned priority number, the greater
the access to bandwidth and the less likelihood of loss.
Figure 3-2. Automatic Rerouting With Dual-Homed PVCs
Access
Concentrator
Access
Concentrator
Active PVC
Backup PVC
Active PVC
Backup PVC
ATM Network
Interrupted
Link failure
service
Continued
service