User guide

EDA System Services
60 1/1551-HSC 901 35/3 Uen C 2005-12-02
IP DSLAM
Downstream traffic
Packet based queuing (4 flows)
Traffic
scheduler
Packet based queuing (1 flow)
PVC
mapping
Algorithms:
• Strict Priority
• Deficit Round Robin
• Modified Deficit Round Robin
OLP
ATM
Prioritization
VBR-rt7
6
5
0-4
CoS Flow
policing
CoS Flow
policing
CoS Flow
policing
CoS Flow
policing
Traffic
scheduler
CoS Flow
policing
Figure 43 Packet Based Queuing
The buffer for the queues can contain up to 128 Ethernet frames per End-
user. The buffer allocated to each queue is dynamic. If there is no more
available buffer and new traffic arrives, frames from the lowest priority will
be discarded in order to make place for higher priority frames.
As illustrated in Figure 43, if only one CoS flow is defined in a service, the
frames will be placed in a queue that will be emptied right away by the
traffic scheduler.
The traffic scheduler can use the following algorithms when emptying the
queues:
• Strict Priority - The queues are processed by strict priority order. As
long as there are packets in a higher priority queue, packets in a lower
priority queue will not be sent. Queue 1 is the highest priority and
queue 4 is the lowest.
• Deficit Round Robin (DRR) - The queues are serviced by weight in
terms of bytes transmitted from each queue. The weights are fully
operator configurable. The queue numbers has no importance when
DRR is used, only the weight of each queue.