fq_codel and quantum

[Nat P]

Hi all,

I'm taking a look into the newly added fq_codel class. I have a doubt, probably because I don't know exactly what is done in the kernel. It seems that, in ns-3, the m_quantum variable is always 0. In fact, with this configuration, it seems that a newly created flows at enqueue (line 188 and 189) have quantum at 0. Consequently, in Dequeue (line 220) they are transformed in "old" flows very soon.

The correct way for an user to use FqCodel is to manually set m_quantum through the method FqCoDelQueueDisc::SetQuantum (uint32_t quantum) ? If I'm not wrong (but could be) this would represent the number of dequeued bytes after which a new flows becames old.

Thank you!

Nat

[Stefano Avallone]

The quantum attribute is not null. Quoting from the documentation [1]:

"Note that the quantum, i.e., the number of bytes each queue gets to dequeue on each round of the scheduling algorithm, is set by default to the MTU size of the device (at initialisation time). The FqCoDelQueueDisc::SetQuantum () method can be used (at any time) to configure a different value."

You might want to have a look at FqCoDelQueueDisc::InitializeParams() for more details.

Bests,
Stefano

[1] https://www.nsnam.org/docs/models/html/fq-codel.html

[Nat P]

aaah! Very nice, thank you.

Nat