Revert "Increase the default TCP maximum segment size from 512 to 1460."
This reverts commit
d190343e53819e25316a2a890724404f8e48c78d.
It seems that there are systems (probably firewalls) in action which
enforce an MSS of 536.
Specifically, at research.microsoft.com, port 80, packets seem to be
simply dropped if they exceed a MSS of 536 bytes, and no ICMP
destinatino unreachable, need to fragment message is generated.
While this behavior might be questionable as well, we should not diverge
from established standards.
This default MSS value can be changed using the sysctl node
net.inet.tcp.mssdflt.
Mandated by RFC 879, RFC 1122.