I would agree, but sadly WISP networks are full of 100Mbps links AND a ton of variable bandwidth ptp and ptmp links.
You will have to buffer to have any kind of meaningful throughput, otherwise Bandwidth Delay Product calculations will drive your throughout into the dirt. Buffer BLOAT is bad. Buffering is not inherently bad, and is often necessary. On Nov 7, 2016 10:35 AM, "Fred Goldstein" <f...@interisle.net> wrote: > On 11/7/2016 11:05 AM, Josh Reynolds wrote: > > Sorry, correction layer 4. TCP slow start and window sizing. > > Allowing l2 to control your drops in a willy nilly fashion though is not a > good idea... And random "pauses" on your backbone is also a poor idea. > > The idea is to smooth out the flow end to end; it's the big bursts that > cause trouble. > > I'm of the opinion that WISP networks likely need to move to deep buffer > data center switch designs, simply because of the number of variable speed > links. > > > No, I prefer the opposite. Bufferbloat is bad! The math shows that you > basically don't need a buffer bigger than 10 packets or so. But with QoS > classmarking, you may need multiple buffers. > > On Nov 7, 2016 9:53 AM, "Fred Goldstein" <f...@interisle.net> wrote: > >> On 11/7/2016 10:40 AM, Josh Reynolds wrote: >> >> Negative, layer2 flow control is an axe when you need a scalpel. Turn it >> off everywhere! >> >> Layer3 has automatic mechanisms to help handle bandwidth saturation, and >> packet loss is part of that process. Furthermore, proper ToS/DSCP queueing >> is equally important. >> >> >> Well, technically no, Layer 3 has NO mechanisms to deal with capacity. It >> was a known issue among the network working group members in 1973 and a >> known issue in 1974 when TCP v1 was written, but the team had turned over >> by 1978 when TCP/IPv4 came out, and that group forgot about it until 1986 >> when things fell apart. The temporary short-term not very good fix was in >> layer 4 (TCP Slow Start) and that doesn't even apply to all streaming, >> though many do cooperate. Of course it was "good enough", so 30 years later >> it is taken as gospel. TCP/IP is the *chabuduo *of protocol stacks. >> >> There could be issues with using flow control on the Ethernet port, but >> really flow control should have been part of every layer. Loss should >> generally be localized. >> >> On Nov 7, 2016 9:36 AM, "Judd Dare" <judd.d...@gmail.com> wrote: >> >>> So you're saying, make sure Flow Control is enabled on the ports? >>> >>> On Mon, Nov 7, 2016 at 8:22 AM, Josh Reynolds <j...@kyneticwifi.com> >>> wrote: >>> >>>> Microbursts causing buffer drops on egress ports to non-10G capable >>>> destinations. The switch wants to send data at a rate faster than the 1G >>>> devices can take it in, so it has to buffer it's data on those ports. >>>> Eventually those buffers fill up, and it taildrops traffic. TCP flow >>>> control takes over and eventually slows the transfer rate by reducing >>>> window size. It doesn't matter if its only sending 100M of data, its the >>>> RATE that it is sending the data. >>>> >>>> On Nov 7, 2016 8:58 AM, "TJ Trout" <t...@voltbb.com> wrote: >>>> >>>>> I have a 10G switch that is switching everything of mine at my NOC, >>>>> including peers, router wan, router lan, uplink to tower, etc >>>>> >>>>> During peak traffic periods ~2gbps I'm seeing 1% packet loss and >>>>> throughput will drop to 0 for just a second and resume normal for a few >>>>> minutes before dropping back to zero for just a second. doesn't seem to be >>>>> affecting the wan side of my router which connects to peers through the >>>>> same switch. Doesn't happen during the day with low periods of traffic. >>>>> >>>>> I've enabled / disabled STP, Flow control. >>>>> >>>>> I believe I've isolated it to not be a single port, possibly have a >>>>> bad switch but that seems hard to believe... >>>>> >>>>> Port isn't flapping, getting small amounts of fcs errors on receive >>>>> and lots of length errors but i think those shouldn't be a problem? >>>>> >>>>> It's an IBM G8124 10G switch >>>>> >>>>> Ideas? >>>>> >>>>> _______________________________________________ >>>>> Wireless mailing list >>>>> Wireless@wispa.org >>>>> http://lists.wispa.org/mailman/listinfo/wireless >>>>> >>>>> >>>> _______________________________________________ >>>> Wireless mailing list >>>> Wireless@wispa.org >>>> http://lists.wispa.org/mailman/listinfo/wireless >>>> >>>> >>> >>> _______________________________________________ >>> Wireless mailing list >>> Wireless@wispa.org >>> http://lists.wispa.org/mailman/listinfo/wireless >>> >>> >> >> _______________________________________________ >> Wireless mailing >> listWireless@wispa.orghttp://lists.wispa.org/mailman/listinfo/wireless >> >> -- >> Fred R. Goldstein k1io fred "at" interisle.net >> Interisle Consulting Group >> +1 617 795 2701 >> >> _______________________________________________ Wireless mailing list >> Wireless@wispa.org http://lists.wispa.org/mailman/listinfo/wireless > > _______________________________________________ > Wireless mailing > listWireless@wispa.orghttp://lists.wispa.org/mailman/listinfo/wireless > > -- > Fred R. Goldstein k1io fred "at" interisle.net > Interisle Consulting Group > +1 617 795 2701 > > > _______________________________________________ > Wireless mailing list > Wireless@wispa.org > http://lists.wispa.org/mailman/listinfo/wireless > >
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