[Cerowrt-devel] SQM and PPPoE, more questions than answers...
moeller0 at gmx.de
Wed Oct 15 15:55:45 EDT 2014
On Oct 15, 2014, at 19:28 , Dave Taht <dave.taht at gmail.com> wrote:
> hmm. The pppoe LLC packets are sparse and should already be optimized
> by fq_codel, but I guess I'll go look at the construction of those
> headers. Perhaps they need to be decoded better in the flow_dissector
So when shaping on pppoe-ge00 one does not see the LLC packets at all (tested with tcpdump -i pppoe-ge00), since they are added after the shaping. (tcpdump -i ge00 does see th dllc packets) I have no idea whether pppd issues these with higher priority or not.
> I also made some comments re the recent openwrt pull request.
> SQM need not require the advanced qdiscs package, if it checks for
> availability of the other qdiscs,
Well, but how to do this, I know of no safe way, except testing availability of modules for a known set of qdiscs, but what if the qdiscs are built into a monolithic kernel? Does anyone here have a good idea of how to detect all qdiscs available to the running kernel?
> and even then nobody's proposed
> putting the new nfq_codel stuff into openwrt - as it's still rather
> inadaquately tested, and it's my hope that cake simplifies matters
> significantly when it's baked. I already have patches for sqm for it,
> but it's just not baked enough...
> Also I think exploring policing at higher ingres bandwidths is warrented…
> On Wed, Oct 15, 2014 at 6:39 AM, Sebastian Moeller <moeller0 at gmx.de> wrote:
>> Hi Edwin,
>> On Oct 15, 2014, at 14:02 , Török Edwin <edwin+ml-cerowrt at etorok.net> wrote:
>>> On 10/15/2014 03:03 AM, Sebastian Moeller wrote:
>>>> I guess it is back to the drawing board to figure out how to speed up the classification… and then revisit the PPPoE question again…
>>> FWIW I had to add this to /etc/config/network (done via luci actually):
>>> option keepalive '500 30'
>>> Otherwise it uses these default values from /etc/ppp/options, and then I hit: https://dev.openwrt.org/ticket/7793:
>>> lcp-echo-failure 5
>>> lcp-echo-interval 1
>>> The symptomps are that if I start a large download after half a minute or so pppd complains that it didn't receive reply to 5 LCP echo packets and disconnects/reconnects.
>> I have not yet seen these in the logs, but I will keep my eyes open.
>>> Sounds like the LCP echo/reply packets should get prioritized, but I don't know if it is my router that is dropping them or my ISP.
>> I think that is something we should be able to teach SQM (as long as the shaper is running on the lower ethernet interface and not the pppoe interface).
>>> When you tested PPPoE did you notice pppd dropping the connection and restarting, cause that would affect the timings for sure…
>> Nope, what I see is simply more variance in bandwidth and latency numbers and a less step slope on a right shifted ICMP CDF… I assume that the disconnect reconnects should show up as periods without any data transfer….
>> Mmmh, I will try to put the PPP service packets into the highest priority class and see whether that changes things, as well as testing your PPP options.
>> Thanks for your help
>>> Best regards,
>>> Cerowrt-devel mailing list
>>> Cerowrt-devel at lists.bufferbloat.net
>> Cerowrt-devel mailing list
>> Cerowrt-devel at lists.bufferbloat.net
> Dave Täht
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