Lectures notes for 2010 - KTH

TCP Header
0 7 8 15 16 23 24 31
16 bit source port 16 bit destination port
32 bit sequence number
4 bit header
length
reserved
(6 bits)
U
R
G
A
C
K
32 bit acknowledgement number
P
S
H
R
S
T
S
Y
N
F
I
N
16 bit window size
20 bytes
16 bit TCP checksum 16 bit urgent pointer
options (if any)
data (if any - padded to a multiple of 16 bits)
Figure 1: IP header (see Stevens, Vol. 1. inside cover or Forouzan figure 12.5 pg. 282)
Just as with UDP, TCP provides de/multiplexing via the 16 bit source and
destination ports.
The 4 bit header length indicates the number of 4-byte words in the TCP header
Maguire TCP Header 5: 6 of 77
maguire@kth.se 2010.03.21 Internetworking/Internetteknik