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QOS on sbc controller?

Discussion in '3CX Phone System - General' started by viraltechnology, Dec 14, 2017.

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  1. viraltechnology

    Mar 22, 2015
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    I saw a walk though posted how to tag the traffic from the sbc with higher priority. I have a couple of questions. A. If you have no qos policy in the network (all dumb switches) is this worthwhile? I mean we can't enforce qos across the wan.

    B. Installing the required app to make the iptables doesn't write over any already in use iptables rules does it?

    Thoughts / experience requested.
  2. lneblett

    lneblett Well-Known Member

    Sep 7, 2010
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    The question posed is problematic to answer as the traffic load is an unknown as is the traffic load destined for the Internet. However, let's ask it in a different manner - Is there any harm in tagging for QoS?

    First, QoS is typically implemented whenever the impacted device is reaching saturation. When the device approaches saturation, it will begin to spawn the QoS queues in an effort to maintain the packet delivery of those with higher levels at the expense of lower tagged packets, even if it means that it has to drop some lower level packets.

    So, if your network and Internet connection are adequate at all times to handle the load, then QoS will buy you nothing. On the other hand, as your switches do not support QoS, and assuming your router does, then it may be a question of if there is a need to have QoS implemented such that as packets arrive at the router and should there be the possibility that saturation might come about, would you not want the router to at least prioritize the voice packets to the WAN as best it could? You are correct in that once the packets reach the Internet (as it currently stands with net neutrality) that all packets are peer, but the delivery to the Internet as your packets traverse your firewall is still under your control.

    So, the bottom line is that if all is fine now and there is no concern about congestion in the future, then there is no need. It only adds additional data for the tagging that will never be acted upon. If there is any hint of congestion, then presumably it will get worse as your needs grow, so QoS will not hurt and it may save you from future issues.
    viraltechnology likes this.

    DSXDATA New Member

    Oct 20, 2015
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    The medical profession has a term called "hunting Zebras" - Zebras look like horses but are rare and unique. Once a medical student learns about a zebra, they tend to look for them. In our world, these are called edge conditions. Like the medical profession, network engineers can sometimes get distracted by the science and tools to deal with edge conditions.

    I like the approach of waiting until the edge condition manifests and then adjust accordingly and minimalistically. There are unintended consequences to most every policy and traffic rule that gets applied - not to mention the difficulty of identifying causation when the rule-set grows.

    K-I-S-S :rolleyes:
    Stop hovering to collapse... Click to collapse... Hover to expand... Click to expand...
    NickD_3CX and viraltechnology like this.
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