It doesn&#x27;t matter the MTU setting on your end for WAN and ISP &#x2F; interlink grade networks is meaningless they don&#x27;t use Ethernet,  FDDI frame size is 4500 (ATM is about double that) bytes (minus what ever overhead, but usually 4200 and change) ISP&#x2F;WAN routers don&#x27;t care about how many mbit&#x2F;s they transfer but how many packets they route at per given unit of time, as packets get packed into a single frame the smaller the packet the more packets they can transfer each frame.<p>Also from a more high level point of view if you think about it the small packets are the most critical ones and they are at least as far as responsiveness goes DNS is limited to 512bytes over UDP, TCP 3-way handshake packets are tiny and those are the packets that need to get to and back from their destination as fast as possible, delays in data transfers means slower speeds, delays of handshakes mean that your application can fail or hang.
Other important traffic such as VOIP[0] also uses very small packet sizes for this same reason most critical services need to transfer very little data (per given unit of time) but need to update data as frequently as possible to provide the illusion of real time and to mask the latency, same goes for other things like online&#x2F;multi-player gaming and so on and on and on.
Pretty much if you want your service to be as responsive as possible limit your packet size to the smallest size possible and increase your PPS this will ensure that your packets get quicker to their destination.
[0]VOIP Packet Sizes <a href="http:&#x2F;&#x2F;www.cisco.com&#x2F;c&#x2F;en&#x2F;us&#x2F;support&#x2F;docs&#x2F;voice&#x2F;voice-quality&#x2F;7934-bwidth-consume.html" rel="nofollow">http:&#x2F;&#x2F;www.cisco.com&#x2F;c&#x2F;en&#x2F;us&#x2F;support&#x2F;docs&#x2F;voice&#x2F;voice-qualit...</a><p>The only time you would want to use large packets is pretty much when you can have a buffer, this means that you need to handle less packets per second which lowers CPU consumption (across the entire path) so video streaming and such can use pretty much as large of an MTU as they want unless they start getting fragments.