So over on Unix and Linux we were chatting about how to tag questions related to traffic shaping. We thought we would check ServerFault for reference, but that led me to wonder just what exactly is going on here.

Can somebody explain the differences between , , and ? If there isn't a difference, perhaps should be the main tag and the others should be aliased to it?

I realize the technology specific tags like for linux, for BSD, etc need to stick around, but it seems like one general term for managing bits on the wire should be enough. Or am I missing something?

1 Answer 1


= Quality of Service. No deliberate traffic shaping, but ensuring certain protocols have a higher priority than others. For example, VoIP traffic will always win in an argument over bandwidth with Bit Torrent.

and to me sound like the same thing (with being the correct tag). Actually limiting the amount of traffic each segment on your network is allowed to consume. A segment could be almost anything - a user, a subnet, a VLAN, a device. Any division that exists on a network can usually be controlled. Packets that exceed this limit will be dropped regardless of the amount of traffic on the network.

So they are at least two different things in your list of 3 there.

  • I see the conceptual difference you mention, but is that born out in usage? Time for some cleanup or do the available tags need fixing first?
    – Caleb
    Commented Jun 27, 2011 at 22:06
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    @Caleb - qos and traffic shaping are both in theory and in practice quite different things, and they require different solutions. QoS is administered quite differently to traffic shaping. QoS is often a client-side protocol, and traffic shaping is a server- (or gateway-) thing. Commented Jun 27, 2011 at 22:09
  • Do rsync --bwlimit and friends fall under traffic-shaping? They're surely bandwidth-control. Commented Jun 27, 2011 at 22:16
  • @Gilles - not familiar with rsync. Feel free to post your own answer with your belief though :) Commented Jun 27, 2011 at 22:46
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    @Gilles Since Rsync bwlimit does its limiting in the app itself rather than via QOS, I'd call that use-case traffic-shaping. The entity doing the traffic management is an application well above the TCP layer. QOS is in the TCP/IP protocol stack.
    – sysadmin1138 Mod
    Commented Jun 27, 2011 at 23:28
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    @Gilles, we shouldn't let program/application options/parameters become tags, unless there is some really overwhelming reason to do so, so the apparent similarity of --bwlimit and bandwidth-control is quite irrelevant. Commented Jun 28, 2011 at 0:18
  • QoS is policy as applied to traffic (queue priority, CBR, CIR, DBR, etc). Traffic-Shaping is applying bandwidth policy to particular types of traffic. While they're very closely related, there's a different. In-App QoS or Traffic-Shaping is part of the paricular app and shouldn't be tagged as the others (unless the question related to their interaction of course).
    – Chris S
    Commented Jun 28, 2011 at 2:17
  • @Mark: My question about usage wasn't about real-world application of the technology, it was about current usage of the existing tags on ServerFault. Is this distinction useful in sorting the current questions and are the proper tags actually applied to questions? Or is everything just tagged with whatever comes to the OP's mind (including all three because they don't know the difference)?
    – Caleb
    Commented Jun 28, 2011 at 11:00
  • Bandwidth control--to me--seems like a broad term to describe any technologies to reduce and restrict bandwidth such as throttling/shaping, caching, whitelisting/blacklisting. Traffic shaping implies certain types of traffic are restricted. QoS is sort of the opposite--certain types of traffic are prioritized in the case of congestion. Maybe it would be good to see how they're being used?
    – nijave
    Commented May 8, 2017 at 16:11

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