Hello, Ewa. Can you catch the traffic with NFLOG target and tcpdump before enqueueing into device to investigate the original order of packets? Also, it will be useful to check the statistics of classes (tc -s -s -d class ls..). Can you share the some part of this data? 2016-04-12 16:17 GMT+03:00 Ewa Janczukowicz <janczukowicz.ewa@xxxxxxxxx>: > Hello, > > I would like to ask a question about a weird (at least for me J) HTB > behavior that I get, while prioritizing one type of traffic. > > I am working on assuring low delay for UDP traffic at the home gateway > level. At this home gateway I have two types of traffic, TCP and UDP, > and I assure differentiated treatment by using HTB. > The bandwidth I am testing equals 1Mbit/s. > > Thus, I have to types of leaf classes: > - UDP leaf class with: > - the highest priority, > - a short queue length (SFQ qdisc), > - assured rate 200kbit/s and ceil rate 1Mbit/s, > - quantum = 3 x MTU. > > - TCP leaf class with: > - lowest priority, > - default queue length (pFIFO qdisc), > - minimum assured rate (8bit/s – to force it to stay in yellow mode > most of the time) and ceil rate 1Mbit/s, > - quantum = MTU. > > In order to see how the traffic interacts, for UDP I have a stairs > type of traffic, thus I start at 0bit/s and I increase the traffic > every ten seconds by 100kbit/s. When I reach 1Mbit/s I decrease every > 10s by 100kbit/s until I reach zero. > > Alongside, I have TCP traffic, either a file upload, either a simple > iperf (without any influence on observed behavior). > > Normally, most of the time, I get an expected behavior. Thus I can see > perfectly the traffic separation and the “stairs” trend of the UDP. > Additionally, UDP traffic takes over TCP (but TCP can still send – and > the trend is the opposite of UDP, thus first decreasing, later > increasing). > > However when the UDP bitrate is already decreasing (about 30 seconds > before reaching 0), TCP traffic completely takes over for a couple of > seconds. I can’t really understand this behavior, because it seems > that UDP traffic cannot send, but it shouldn’t be in “red” mode since > its bitrate is already decreasing. > > I think it has something to do with HTB scheduling and blocking UDP > traffic for some reason. > > I hope my question is clear, but I can also provide wireshark bitrate graphs. > > I will continue to test different configurations but I will appreciate > any suggestions. > > Thank you in advance for your help. > > Ewa > -- > To unsubscribe from this list: send the line "unsubscribe lartc" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Anton. -- To unsubscribe from this list: send the line "unsubscribe lartc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
