[SATLUG] OT: question about TCP headers

redpill toddwbucy at grandecom.net
Tue Jan 26 22:12:05 CST 2010

I am currently taking Kolars TCP/IP class at SAC and this question
relates to a non-graded lab. 

class text - TCP/IP Illustrated Volume 1: the protocols cira 1994
web reference png image illustrating the TCP header breakdown -

the text notes that there are 6 reserved bits between the header length
and the flags (page 225).  The image noted above has shown 4 bits
reserved between the length and the flags.  2 additional flags are added
on the png file that are not listed in the book: C 0x80 Reduced (CWR)
and E 0x40 ECN Echo (ECE).  Which one is correct?  I was shown this file
by a classmate and I need to confirm its accuracy. 

you will win my vote for uber geek of the year if you can give me the
RFC's that may clarify this issue.


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