For Dave, the QoS update

2016 November 19
by Daniel Lakeland

I've been using Fireqos for my home network. Since switching recently to Gigabit fiber it required a lot of reconfiguring of my internal network. In the process I discovered a few things:

  1. Typical consumer level routers from even a few years ago can't even begin to handle a gigabit through their firewall. You need something with an x86 type processor or a very modern ARM based consumer router. My Buffalo router could push about 150Mbps through the firewall at most.
  2. QoS is still important at gigabit speeds. You can push a lot of data into buffers very quickly. Furthermore keeping things well paced actually allows you to go faster because acks make it back to where they're going.
  3. Don't forget the effect of crappy cables. Replace your patch cables that you have lying around that came with whatever stuff you used to have with something good. I made my own patch cables with a crimp tool and high quality Cat5e, and it improved packet loss issues that may have been an issue before as well.
  4. As Dave Taht suggested, switching from pfifo to fq_codel helped for the ssh connection class. In particular, I had been thinking of this class as mainly handling keystrokes and things for ssh sessions, but of course scp and rsync both like to push data over ssh. Because of that, I needed to put an fq_codel qdisc on the ssh class so my keystrokes would make it even when some rsync was going.
  5. Too many things have changed at once for me to know whether fq_codel would have any affect on my voip RTP queue. But I suspect not. Every 0.02 seconds it'll send a single udp packet for each call. Each packet is around 1000 bytes. There are typically 1-4 calls at most. They jump to the front of the line due to the QoS and so the queue is never going to have more than 1 or 2 packets in it. The overhead of fq_codel makes no sense when the queue never gets longer than 3 packets and never takes longer than .00002 seconds to drain. If I have any issues though, I'll revisit.

 

One Response leave one →
  1. November 20, 2016

    thx for being willing to do the experiment, challenge your assumptions and find out AND document the edge cases in your setup!

    we've been pushing fq technology to its limit with cake, recently adding de-natting and host isolation modes, so that *in theory*, all the work you just did is reduced to a single command line, that works without any classification at all, due to the 8 way set associative hash and mildly modified fq_codel algorithm.

    tc qdisc add dev whatever root cake bandwidth 940mbit besteffort triple-isolate

    If you want some diffserv classification, omit besteffort.

    For more details, see: http://www.bufferbloat.net/projects/codel/wiki/CakeTechnical

    It compiles out of tree for most kernels after 3.14.

    PS scp does try to set the background bit, btw, but I think it's borken on ipv6.

    PPS videoconferencing is really the next big thing we want to handle better.

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