In article <20170811163021.GK7481(a)platypus.pepperfish.net>, Rob Kendrick
On Fri, Aug 11, 2017 at 05:16:09PM +0100, Dave Higton wrote:
> If anyone reading this thread can shed any light on MTU issues, how
> to diagnose them and how to fix them, it would be very helpful.
Something that has bitten be before is where automatic path MTU
discovery does not work (and I suspect it doesn't on RISC OS), and your
ISP does not support end-to-end 1500 byte MTUs (many do not).
The solution is to set your whole LAN's MTU to 1400 or similar,
although setting it only on the RISC OS machines may be sufficient (and
not needed on VirtualAcorn because that proxies Windows's IP stack
which is full-featured and conforming) assuming the problem is only
sending large packets, not receiving them.
I find it fascinating that my ISP's web support MTU is variously 1454,
1458, 1492 and 1500. This is dependent on hardware - the last one being a
generic setting for 'none of the above routers'.
Funny how the original 'net developers opted for and MTU of around 1500.
Anyone who's had a computer for more than a few weeks ought to wonder why
it's not 1024.
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