D-Link NetDefend DFL-210 User Manual page 260

TCPOPT_CC
to transport alternate checksums where permitted by ALTCHKREQ above. Normally never seen on
modern networks.
Default: StripLog
TCPOPT_CC
Determines how NetDefendOS will handle connection count options.
Default: StripLogBad
TCPOPT_OTHER
Specifies how NetDefendOS will deal with TCP options not covered by the above settings. These
options usually never appear on modern networks.
Default: StripLog
TCPSynUrg
Specifies how NetDefendOS will deal with TCP packets with SYN (Synchronize) flags and URG
(Urgent data) flags both turned on. The presence of a SYN flag indicates that a new connection is in
the process of being opened, and an URG flag means that the packet contains data requiring urgent
attention. These two flags should not be turned on in a single packet as they are used exclusively to
crash computers with poorly implemented TCP stacks.
Default: DropLog
TCPSynPsh
Specifies how NetDefendOS will deal with TCP packets with SYN and PSH (Push) flags both
turned on. The PSH flag means that the recipient stack should immediately send the information in
the packet to the destination application in the computer. These two flags should not be turned on at
the same time as it could pose a crash risk for poorly implemented TCP stacks. However, many
Macintosh computers do not implement TCP correctly, meaning that they always send out SYN
packets with the PSH flag turned on. This is why NetDefendOS normally removes the PSH flag and
allows the packet through despite the fact that the normal setting should be dropping such packets.
Default: StripSilent
TCPFinUrg
Specifies how NetDefendOS will deal with TCP packets with both FIN (Finish, close connection)
and URG flags turned on. This should normally never occur, as you do not usually attempt to close
a connection at the same time as sending "important" data. This flag combination could be used to
crash poorly implemented TCP stacks and is also used by OS Fingerprinting.
Default: DropLog
TCPUrg
Specifies how NetDefendOS will deal with TCP packets with the URG flag turned on, regardless of
any other flags. Many TCP stacks and applications deal with Urgent flags in the wrong way and can,
in the worst case scenario, cease working. Note however that some programs, such as FTP and MS
SQL Server, nearly always use the URG flag.
Default: StripLog
TCPECN
247
Chapter 13. Advanced Settings