Hsmda Buffer Utilization Controls - Alcatel-Lucent 7450 Quality Of Service Manual

HSMDA QoS Model

HSMDA Buffer Utilization Controls

The HSMDA has 1 million ingress and 1 million egress 168-byte buffers available for packet
queuing purposes. The average of approximately six buffers per queue when all 163,480 are
active. Certain queues need more than 6 buffers while other queues require very shallow
buffering based on the type of traffic the queue is servicing and the scheduling priority of the
queue. To facilitate management of the available buffer space, the HSMDA supports a
hierarchical buffer pool scheme and a per queue set of RED slopes. The buffer pools allow
proper sharing of the buffer space while the slopes within each queue set limits on how many
buffers each queue may consume.
HSMDA Buffer Pools
Two types of queues are created on the HSMDA; provisioned service or subscriber queues
and system created queues. System queues are transparent to the user and perform functions
like discard bypass. Since system queues are critical to the operation of the system, normal
service or subscriber queue activity will not cause buffer starvation on the system queues.
Buffer utilization is separated based on the scheduling class, ensuring that activity on one set
of class queues does not impact buffer availability for other class queues.
The pooled buffer management capabilities in the HSMDA include:
Identifying Queue Groups as Provisioned or System
All queues are contained in a set of eight queues called a queue group. Two sets of 20,480
queue groups exist on the HSMDA, one set for ingress and the other for egress. The queue
groups are defined as either provisioned (service or subscriber) or reserved for system use.
The HSMDA uses a two 20,480 bit-wide tables to allow the system to define each queue
group as either provisioned or system reserved separately for ingress and egress. The queue
group id mapping table represented in
(provisioned) or pool group S (system). For ingress and egress, the first 20,000 table entries
(0 to 19,999) is set to group P and the remaining 480 (20,000 to 20,479) is set to group S.
768
• Identifying which queue groups consume provisioning buffers and which consume
system reserved buffers.
• Setting the total provisioning buffers available per port for each scheduling class.
• Setting the total system reserved buffers available per port for each scheduling class.
• 32 aggregation buffer pools used for managing buffers available per class and per
type (provisioned/system).
Figure 46 places queue groups in pool group P
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