Why do large downloads affect ping?

  • My two sons are gamers (League of Legends, DOTA) and the three of us share an 80 megabit FiOS connection.  They complain that their ping goes way up if someone else is downloading a large file while they are in a match.  This, apparently, is very, very bad. I'm new  using pfSense and am not a network engineer. Is there anything I can learn about to help me alleviate this source of gnashing teeth?


  • You're sharing network resources, so if someone is heavy on your link, others may be shut out or at least have a degraded experience.  What you need is traffic shaping.  Hold on to your hat.

    Traffic Shaping Guide

    Note that this stuff is probably the hardest thing about pfSense to grok.  Start simple with a PRIQ shaper, and give your boy's PC/consoles priority.  You should not hear any more complaints other than your own wails of anguish as you try to figure out traffic shaping  ;)

  • Thanks for the pointer. Now I know where to start.


  • With downloads, the problem is kinda sorta fixed by traffic-shaping, but not really.

    The problem is that if you download at your maximum attainable speed, forcing your ISP to artificially limit your download speed to 80Mbit. This means they will need to create a buffer, to allow for temporary bursts of over 80Mbit, before the sender is resultingly throttled to 8Mbit or below.

    This buffer that your ISP must create is most likely the problem. It is common for buffers to queue over a 1 second of packets, causing an extra 1 second delay. To solve this you need to artificially limit your download speed below 80Mbit so that you, and not your ISP, controls the buffer.

    So, create a LAN queue (CODELQ, PRIQ, HFSC, etc. Which one is unimportant for this setup) then set the bandwidth slightly below your real-world download throughput, like 75Mbit or so, and that should be all you need to do, assuming this was the problem… :)

  • Here's a question regarding that, which shaping method would be preferrable for gaming traffic?

  • This would be better asked in a new thread instead of hijacking this one…

    There is no one best algorithm for shaping games.  The real question to ask is, how time-critical are my requirements?  If you want certain users or apps to have priority regardless of anything else, use PRIQ or CBQ.  If you need to guarantee realtime performance while best-serving other users, HFSC is better.  PRIQ is easy; HFSC is hard.

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