Re: NAT stops forwarding ACKs after PMTU discovery

Eric Dumazet
2013-08-19T16:00:40Z

On Mon, 2013-08-19 at 17:33 +0200, Christoph Paasch wrote:

>
> Unfortunately, they will hardly go away in the near futur. Rather the
> opposite is the case.
>
>
> If you have a public server running, I would be interested in the count of
> invalid SACK-blocks received (netstat -s | grep TCPSACKDiscard). This is an
> indication for such kind of middlebox between your server and the client,
> implying that these connections cannot benefit from TCP-FastRetransmission
> and each packet-loss will require an RTO to recover.
>

If the (random) sequence offset is small rather than completely out of
window, it's going to be hard to detect all problems.

Show us your patch ;)