The newer modem supports the bonding of more download channels (8 vs. 4 for the 6120) and is also used in conjunction with telephony (whereas I have a pure Internet subscription without telephony). Anyway, all of that should not matter as you also indicate: both can handle the respective up- and download speeds with ease. Yes, both she and I have the same subscription (minus the telephony): 60 Mb down and 4 Mb up. We also only live 25 kilometres apart (small country:-)) The uplink speed is mostly consistent around 3.76 megabit. I've never caught our cable company going lower than 3.50 megabit in the upload direction and I've done a lot of speedtests. The only limit I have been able to observe is in the download direction when their network is really busy. I guess I will have to venture into traffic shaping. (I'll probably loose a lot of sleep setting this up lol). Is there any way to determine the buffer size reliably? On Sat, Feb 9, 2013 at 7:15 PM, Jonathan Morton wrote: > Latency caused by bufferbloat always appears at the bottleneck device. > Usually that is the modem, and you've given no alternative that it could > plausibly be. The modems you mention are slightly different model numbers, > but that can hide substantial differences in internal configuration. > > For a typical drop-tail queue, the induced latency under load is the size > of the buffer divided by the speed of the link draining it. Assuming both > modems have a 4Mbit uplink, 550ms is consistent with a 256KB buffer, and > 220ms is consistent with a 48KB buffer - neither of which would seem > excessively large to a modem builder who hasn't heard of bufferbloat. > However with a shared cable infrastructure, it is possible that the uplink > is constrained by other users on the same segment, which will skew this > calculation. > > To cure it without modifying the modem, you need to move the bottleneck to > a point where you can control the buffer. You do this by introducing > traffic shaping at slightly below the advertised modem uplink speed on one > of your own machines and directing all upstream traffic through it. > > - Jonathan Morton > On Feb 9, 2013 7:27 PM, "Forums1000" wrote: > >> Hi Jonathan and Dave >> >> My entire LAN-network is gigabit. My cable subscription is 60 megabit >> down and 4 megabit up. >> Now, both my routers' WAN-port and the cable modems' LAN port are also >> gigabit. The router can route LAN to WAN and the other way around (with NAT >> and connection tracking enabled) in excess of 100 megabit. >> >> Now my cable modem is a Motorola Surfboard SV6120E and hers is a Motorola >> Surfboard CV6181E. My upload lag is 550ms and hers is only 220ms. Moreover, >> at her place there are Powerplugs in the path limiting her download to 30 >> megabit instead of 60 megabit. Yet, the upload lag is much lower than mine. >> There, it also did not matter where I ran Natalyzr, the result was always >> 220ms of bufferbload. >> >> Could this still be only the modem? >> >> >> On Sat, Feb 9, 2013 at 10:52 AM, Forums1000 wrote: >> >>> Hi everyone, >>> >>> Can anyone give some tips on how to diagnose the sources of bufferbloat? >>> According to the Netalyzr test at http://netalyzr.icsi.berkeley.edu/, I >>> have 550ms of upload bufferbloat. I tried all kinds of stuff on my Windows >>> 7 laptop: >>> >>> - For the Intel(R) 82567LF Gigabit Network Connection, I put receive and >>> transmit buffers to the lowest value of 80 (80 bytes? 80 packets? I don't >>> know). I also disabled interrupt moderation. >>> Result? Still 550ms. >>> - Then I connected my laptop directly to my cable modem, bypassing my >>> Mikrotik 450G router. Result? Still 550ms of bufferbloat. >>> - Then I put a 100 megabit switch between the cable modem an the laptop >>> (as both cable modem and Intel NIC are gigabit). Result? Still 550ms of >>> upload bufferbloat. >>> >>> I'm out of ideas now. It seems I can't do anything at all to lower >>> bufferbloat. Or the Netalyzr test is broken?:-) >>> >>> many thanks for your advice, >>> Jeroen >>> >>> >> >> _______________________________________________ >> Bloat mailing list >> Bloat@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/bloat >> >>