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MTU to CDN's


> On Jan 18, 2018, at 8:44 PM, William Herrin <bill at herrin.us> wrote:
> 
>> Which packet?  Is there a specific CDN that does this?  Iâ??d be curious to see
>> data vs speculation.
> 
> Howdy,
> 
> Path MTU discovery (which sets the DF bit on TCP packets) is enabled
> by default on -every- operating system that's shipped for decades now.
> If you don't want it, you have to explicitly disable it. Disabling it
> for any significant quantity of traffic is considered antisocial since
> routers generally can't fragment in the hardware fast path.

Iâ??m not seeing this in a PCAP capture to at least one CDN, either from my
host or from the CDN endpoint.

I suspect youâ??re mistaken.

- Jared

PCAP: https://puck.nether.net/~jared/akamai.pcap