Skip to content
Browse files

Tried to finally address bob's concerns.

I think this needs expansion
  • Loading branch information...
1 parent 68f04e4 commit d6a9bbc841a94d48cdc3941ffed3c1f53004e0d1 Dave Taht committed
Showing with 21 additions and 5 deletions.
  1. +21 −5 fq_codel/middle.mkd
26 fq_codel/middle.mkd
@@ -70,11 +70,13 @@ and the CoDel algorithm are fairly straight forward:
At initiation, the queues are initialised so that each queue has a
separate set of CoDel state variables. By default, 1024 queues are
-created, but the current implementation supports anywhere from 2 to
-64k separate queues. Each queue maintains the state variables
-throughout its lifetime, and so acts the same as the non-fq CoDel
-variant would. Codel variants apply varying levels of hysteresis to
-queues that fall out of use to eventually reset their states.
+created. The current implementation supports one to 64k separate
+queues. With one queue FQ-CoDel behaves essentially the same as CoDel.
+Each queue maintains the state variables throughout its lifetime, and
+so acts the same as the non-fq CoDel variant would. Codel variants
+apply varying levels of hysteresis to queues that fall out of use to
+eventually reset their states.
On dequeue, FQ-CoDel selects a queue from which to dequeue by a two-tier
round-robin scheme, in which each queue is allowed to dequeue up to a
@@ -470,6 +472,20 @@ DRR. SFQ-based versions have also been produced and tested in
ns2. Other forms of Fair Queuing, such as WFQ or QFQ have not been
thoroughly explored.
+## Differences between CoDel and FQ-Codel behavior
+CoDel is a single queue system that evolves to an "ideal" drop rate
+and then optimizes around that control point.
+FQ-Codel smears bursts of competing flows over each other, so that a
+new flow gets substantial "credit" over other flows until CoDel finds
+an ideal drop rate for it as well. However, as more time passes before
+all of a new flow is delivered (as packets from it, too, are mixed
+across the other existing queue-building flows), FQ-CoDel seeks an
+ideal drop rate in more time, with less delivered packets.
+FQ-Codel "shoots" more accurately at the largest flows than CoDel.
# Resources and Additional Information
# Security Considerations

0 comments on commit d6a9bbc

Please sign in to comment.
Something went wrong with that request. Please try again.