D-Link NetDefendOS User Manual page 855

Chapter 13: Advanced Settings
TCP Option ALTCHKREQ
Determines how NetDefendOS will handle alternate checksum request options. These options
were initially intended to be used in negotiating for the use of better checksums in TCP.
However, these are not understood by any today's standard systems. As NetDefendOS cannot
understand checksum algorithms other than the standard algorithm, these options can never be
accepted. The ALTCHKREQ option is normally never seen on modern networks.
Note that this TCP option is obsoleted by RFC 6247 and only some network equipment will make
use of it.
Default: StripLog
TCP Option ALTCHKDATA
Determines how NetDefendOS will handle alternate checksum data options. These options are
used to transport alternate checksums where permitted by ALTCHKREQ above. Normally never
seen on modern networks.
Note that this TCP option is obsoleted by RFC 6247 and only some network equipment will make
use of it.
Default: StripLog
TCP Option CC
Determines how NetDefendOS will handle connection count options.
Note that this TCP option is obsoleted by RFC 6247 and only some network equipment will make
use of it.
Default: StripLogBad
TCP Option 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
TCP SYN/URG
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
TCP SYN/PSH
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.
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