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SubjectTCP header bits set in reserved space
I can't seem to find this mentioned anywhere. My 2.4 machine
sets 2 bits in the TCP header between the 4 data offset bits and control
flags. Like so:

11/29-20:25:42.695096 ->
TCP TTL:63 TOS:0x0 ID:0 DF
21S***** Seq: 0x74E55D1A Ack: 0x0 Win: 0x16D0
TCP Options => MSS: 1460 SackOK TS: 1767921 0 NOP WS: 0

or hex a0c2 / binary 10100000 11000010
This packet is never ACK'd by and the only difference I
can see from one that is are these two bits. RFC793 says they must be zero.
Is 793 still current? Has anyone else seen this?


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