[silly] traffic shaping works only on the LAN? True or false?



  • Hi all,
    I have not done traffic shaping up to now, but a colleague of mine have explained me something about it that causes me some doubts. Having a classic scenario, with a gateway with a LAN interface and a WAN one, I can apply traffic shaping in order to limit the bandwidth that a protocol will be using under congestion, right? Now, my colleague says that this is almost useless since the shaping is done only in the LAN side, and the WAN works at the best speed it can always. This sounds quite odd to me, but he explained with an example: if I want to see a youtube video, the video is downloaded from the gateway (WAN) at the maximum speed, is cached and then returned to the LAN client a piece at a time. This does not sound to me as traffic shaping, but like a content caching.
    Instead traffic shaping should work with queues and policies to delay outgoing packets (and therefore incoming packets) depending on the congestion of the link.
    I've tried to explained how pfsense works with the traffic shaping, but my colleague stated that a lot of commercial gateways work has he described.
    What are your comments?


  • Rebel Alliance Developer Netgate

    What you describe is closer to the truth, but I think there is a little confusion in both areas.

    Traffic shaping does not happen on the interface it enters, it happens on the interface it leaves. That is a fact of life, it's the only way shaping can happen, because that's the only place it can possibly be limited. So, downloads are limited when they leave LAN, uploads are limited when they leave WAN.

    Content is not "cached" in any way, but if some packets are dropped, which will trigger a resend, eventually the sending side will throttle itself back. Through a combination of this dropping/throttling of packets, the traffic is effectively limited.


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