Alcatel 1660SM Technical Handbook page 256

Buffer Management
Buffer Management maintains packet memory, structured into multiple queues each queue serving a
particular destination and CoS; i.e. three queues per destination.
It also maintains various queue fill level thresholds to maintain priorization between CoS, prevent any
queue from monopolizing the memory and provide triggers for load balancing.
Load balancing packets are issued after a fixed number of yellow bytes is delivered from a channel.
Upon reaching the first stress level, indicated by queue depth increasing beyond a threshold, buffer
management issues a stress signal to local policers that is increasing in queue depth.
Upon reaching a higher threshold it starts discarding the yellow packets.
Upon reaching a yet higher threshold, which indicates maximum queue occupancy, it discards all arriving
packets.
Shaping
Shaping controls the rate and the order at which packets are injected into the ring.
The total Bandwidth per destination may be determined to either wide NMS as fixed number or dynamically
changed by the load balancing mechanism.
Selection between the two modes is performed by NMS.
The bandwidth per destination is shared between the various queues in decreasing CoS order; i.e. High
packets are forwarded first, Medium next and Low last.
ADM
The ADM function maps packets into the synchronous SDH payload.
The applicable payloads are VC4–4v, VC4–5v, VC4–6v, VC4–7v, VC4–8v.
ED
02
3AL 91669 AA AA 254 / 674
674