[SATLUG] OT: question about TCP headers

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


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

references:
class text - TCP/IP Illustrated Volume 1: the protocols cira 1994
web reference png image illustrating the TCP header breakdown -
http://freebie.fatpipe.org/~mjb/Drawings/TCP-Header.png

question:
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. 

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


Thanks
Todd



More information about the SATLUG mailing list