Cisco Cisco FirePOWER Appliance 7050

clears the 3-bit Reserved field in the TCP header

clears the 16-bit Urgent Pointer field if the urgent (URG) control bit is not set

clears the Urgent Pointer field and the URG control bit if there is no payload

clears the urgent control bit if the urgent pointer is not set

clears any option padding bytes

blocks a subsequent SYN that does not have the same sequence number as the original SYN

When you enable 

, the system drops the following without generating an event:

retransmitted copies of previously dropped packets

traffic that attempts to continue a previously dropped session

any packet that matches any of the following TCP stream preprocessor rules, regardless of whether 
the rules are enabled:

The Blocked Packets performance graph tracks the number of packets dropped as the result of this 
options being enabled. See 

 for 

more information.

When you enable 

 and do not specify 

any

 for 

, the system performs 

the following normalizations:

except MSS, Window Scale, Time Stamp, and any explicitly allowed options, sets all option bytes 
to No Operation (TCP Option 1)

sets the Time Stamp octets to No Operation if Time Stamp is present but invalid, or valid but not 
negotiated

drops the packet if Time Stamp is negotiated but not present

clears the Time Stamp Echo Reply (TSecr) option field if the Acknowledgement (ACK) control bit 
is not set

sets the MSS and Window Scale options to No Operation (TCP Option 1) if the Synchronization 
(SYN) control bit is not set

See 

 for more information.

The system performs the following optional normalizations when you enable 

 and select 

the corresponding option:

enabling the 

 option sets the two-byte Urgent Pointer header field to the 

payload length if the pointer is greater than the payload length

enabling the 

 option normalizes the TCP Data field to ensure consistency in 

retransmitted data and drops any segments that cannot be properly reassembled

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