On 28/05/15 08:00, Steven Barth wrote:
As Dave has already said so well, *if* the ISP did sensible shaping/limiting then I totally agree with you it's a waste of cycles. Unfortunately it's a big if and I've seen some truly horrible behaviour, especially on slow links where I think fair q'ing and latency control are actually more important.Hi everyone, again a bit of a basic question, but what are the advantages of doing ingress shaping in SQM? To me it wastes a lot of CPU cycles (decreases forwarding performance) and you can't really "unsend" any packets from the ISP. What I mean is in 99% of cases your internal forwarding capacity is usually (much?) bigger than what the ISP sends to at any rate. What do I miss here? Some effects on TCP rate-limiting?
Your point about 'unsending' packets is well made though, and since the packet has made it this far and actually got to us it seems a shame to shoot it. ECN would appear to be the best of both worlds, mark the packet/flow that in an ideal world wouldn't have got through and so signalling the other end to back off.
Fitting smaller *managed* pipes here & there is counterintuitive but it does help at the cost of bandwidth, something I'm more than prepared to put up with for the improved latency control. But ideally fq_codel really, really needs to be implemented by the ISP.
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