>2018-02-13 21:21 GMT+01:00 George Neuner <[hidden email]>:
>> On Tue, 14 Nov 2017 12:09:31 +0100, Durumdara <[hidden email]>
>> >*I disabled my firewall at home - the [keepalive] problem vanished!!!*
>> What firewall are you using? Windows own firewall doesn't interfere
>> with keepalive packets. Most commercial SOHO firewalls won't either.
>Normal Windows Firewall (Defender). An ASUS test notebook works. The DELL
>So something is different in the FW on DELL. With manually defined (faster)
>keepalive it's working.
Keepalive is part of the TCP protocol - it's an ACK that repeats the
last used packet sequence number. Under normal circumstances, the
sequence number is incremented (modulo rollover) for each new packet.
Keepalive is recognized as a deliberate and particular breaking of the
Windows firewall has no settings pertaining to keepalive separate from
the operating system. Once you have permitted TCP connections to the
port or program, if any keepalive packets are sent, the firewall must
allow them through.
[Of course, both sides must agree on the keepalive settings for it to
work, but that is a different issue.]
It may be that your firewall is f'd up. The firewall doe perform
"stateful inspection" of open TCP connections - essentially looking
for protocol mistakes that may indicate intrusion hacks or replayed
connections. It could be that the SI module is losing synchronization
when the connection goes idle.
[Back in the day, there were a number of SOHO NAT routers that had
this and other problems with their stateful inspection code.]