[Cerowrt-devel] SQM Question #1: How does SQM shape the ingress?
moeller0 at gmx.de
Sun Dec 29 02:23:32 EST 2013
Rich Brown <richb.hanover at gmail.com> wrote:
>As I write the SQM page, I find I have questions that I can’t answer
>myself. I’m going to post these questions separately because they’ll
>each generate their own threads of conversation.
>QUESTION #1: How does SQM shape the ingress?
>I know that fq_codel can shape the egress traffic by discarding traffic
>for an individual flow that has dwelt in its queue for too long
>(greater than the target). Other queue disciplines use other metrics
>for shaping the outbound traffic.
>But how does CeroWrt shape the inbound traffic? (I have a sense that
>the simple.qos and simplest.qos scripts are involved, but I’m not sure
>of anything beyond that.)
So ingress shaping conceptually works just as egress shaping. The shaper accepts packets at any speed from both directions but limits the speed used for transmitting them. So if your ingress natural bandwidth would be 100Mbit/s you would set the shaper to say 95Mbit/s, so the shaper will create an internal artificial bottleneck just in front of its queue, so that it can control the critical queue.
Technically, this works by creating an artificial intermediate functional block device? (IFB), moving all ingress traffic to this device and setting up classification and shaping on that device.
I hope this helps...
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