QOS -> Inbound Limit

Discussion in 'Tomato Firmware' started by tievolu, Oct 12, 2006.

  1. tievolu

    tievolu Network Guru Member

    I'm really enjoying messing around with this firmware. I was getting a bit bored with DD-WRT :)

    My biggest problem at the moment is getting inbound QOS/throttling to behave similarly to (or hopefully better than) DD-WRT. I think this is basically because I don't understand the details of what the Inbound Limit section actually does.

    It seems to have a positive effect for me in terms of throttling specific inbound traffic, but after playing around with it I've found it rather unpredictable.

    For example, currently I have Bittorrent traffic classified at Lowest priority. If I do not set any Inbound Limit for the Lowest classification, my download bandwidth gets completely saturated, regardless of the outbound settings, dropping http download speeds effectively down to zero (~50kbps out of a total bandwidth of 4096kbps).

    If I set the Inbound Limit for the Lowest classification to 1%, Bittorrent still works fine, consuming all idle downstream bandwidth (so it's obviously not a hard limit of 1% of total bandwidth). It also throttles back if I start a HTTP download (HTTP is classified a High priority), so that Bittorrent and HTTP get around 50% of the downstream each.

    This is a useful result for me, and effectively represents inbound QOS. Yes, I know it's not actually QOS, and the only reason it works is because inbound packets are being dropped, but the end result is a good one for me.

    However, I don't know how to set the Inbound Limits for all the other classifications. I tried setting them to sensible values (I can't remember exactly what values I entered), and the Bittorrent downstream usage on an idle line seemed then to be limited to around 10% of total bandwidth. The only way it seems to have any sort of positive effect for me is with the limit for Lowest set to 1%, and all the others set to None. Does anyone know what's going on here?

    In summary, my questions are:

    1. What exactly do the percentages mean in the drop down boxes?

    2. How does the 1% limit I imposed relate to the ~50% throttling I observe?

    3. How should these limits be set for inbound throttling of the different classifications? Should they all add up to 100% (which seems to be the rule for outbound QOS), or is there some other scheme at work here?
  2. tievolu

    tievolu Network Guru Member

    Hmmm. After playing around some more I seem to lost any inbound throttling behaviour I previously had.

    I'm also wondering how the inbound limits can have any effect on the various classifications, since the available documentation explicitly states that the QOS classifications only apply to outbound packets. Do the inbound limits actually do anything?

    Overall I love the tomato firmware - the realtime GUI is especially cool, but unless I can get similar QOS/throttling behaviour to DD-WRT, I'll have to move back to that firmware for now :(
  3. tievolu

    tievolu Network Guru Member

    Ok, I've been playing some more. The inbound limits do appear to be hard limits, and they do not appear to obey any sort of QOS classification. The only limit that seemed to have an effect was "Low", which is the default classification. Which makes sense if inbound trafiic is not being classified by the outbound QOS rules.

    So, the inbound limits don't really have the effect I want.

    However, I've found that an important setting with regard to inbound throttling is ACK prioritisation. With this turned off, I now get inbound throttling roughly according to the QOS rules - presumably this is because the ACKs are then prioritised according to classification, instead of all ACKs being prioritised equally (which is presumably what the "prioritise ACK" option does when enabled).

    So, with ACK prioritisation disabled, presumably my HTTP ACKs get a higher priority than my Bittorrent ACKs, causing the side effect of HTTP downloads throttling Bittorrent downloads to a certain extent.

    Anyway, I'm a bit happier now - this seems closer to DD-WRT's behaviour with inbound trafific (DD-WRT doesn't have an ACK prioritisation option, at least not the version I was using).
  4. PsychoD

    PsychoD Network Guru Member

    Hey man I just wanted to say thanks for your testing.

    I'm still a little green with QoS and did not manage to configure it completely according to my wishes - so I'm glad about everything anyone explains or experiments regarding QoS. Keep it up :)


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