shared (by multiple nodes) shapers
* Congestion management for hierarchy leaf nodes: algorithms of tail drop, head
drop, WRED, private (per node) and shared (by multiple nodes) WRED contexts
+ and PIE.
* Packet marking: IEEE 802.1q (VLAN DEI), IETF RFC 3168 (IPv4/IPv6 ECN for TCP
and SCTP), IETF RFC 2597 (IPv4 / IPv6 DSCP)
Congestion management is used to control the admission of packets into a packet
queue or group of packet queues on congestion. The congestion management
algorithms that are supported are: Tail Drop, Head Drop and Weighted Random
-Early Detection (WRED). They are made available for every leaf node in the
-hierarchy, subject to the specific implementation supporting them.
+Early Detection (WRED), Proportional Integral Controller Enhanced (PIE).
+They are made available for every leaf node in the hierarchy, subject to
+the specific implementation supporting them.
On request of writing a new packet into the current queue while the queue is
full, the Tail Drop algorithm drops the new packet while leaving the queue
unmodified, as opposed to the Head Drop* algorithm, which drops the packet
definition of WRED profiles. Any WRED profile can be used by one or several
WRED contexts (either private or shared).
+The Proportional Integral Controller Enhanced (PIE) algorithm works by proactively
+dropping packets randomly. Calculated drop probability is updated periodically,
+based on latency measured and desired and whether the queuing latency is currently
+trending up or down. Queuing latency can be obtained using direct measurement or
+on estimations calculated from the queue length and dequeue rate. The random drop
+is triggered by a packet's arrival before enqueuing into a queue.
+
Packet Marking
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