Hi Gert, thanks for clarifying this.
Cheers Jirka H. On 08/24/2015 11:10 PM, Gert Doering wrote: > Hi, > > On Mon, Aug 24, 2015 at 09:17:44PM +0200, Jiri Horky wrote: >> thanks for the information. I see you effectively increased the size to >> 1.2k which, as far as I know, will not work for people with dial ups. > If that wouldn't work, openvpn data transfers would not work either - but > surprisingly, they do :-) - data packets are 1500+ bytes in size, unless > specifically told (--link-mtu) to be smaller. We do cap the control channel > MTU to a smaller value to give particularily broken setups (like, 1400 MTU > *and* broken fragments) the chance to push smaller --link-mtu from the > server. > > "Dial-Up", per se, does not imply a smaller-than-1500 MTU - some folks > do that, for "performance reasons" (reducing MTU actually reduces > performance, as it increases TCP overhead, but what do I know against > glossy computer magazine advice...), but even a 574 byte MTU will still > work *if* fragmentation works. > > Which it normally does in this combination - fragmentation tends to break > if stupid NAT routers are involved, but "dialup with modem links and > 574 mtu" is usually not connected to a NAT router but modem->PC... > > But as I said - I'm waiting for feedback. > > gert >
