1. Topic
The known TCP header is expressed in hexadecimal: 05320017 00000001 00000055 500207FF 00000000. Please answer the following questions:
(1) What is the source port number?
(2) What is the destination port number?
(3) What is the serial number?
(4) What is the confirmation number?
(5) What is the head length value?
(6) What is the type of segment?
(7) What is the window value?
2. Answer
(1) The source port number is the first 16 binary digits at the beginning, that is, the first 4 digits in hexadecimal. That is:
source port number = (05 32) 16 = (0000 0101 0011 0010) 2 = (210+28+25+24+21) 10=1024+256+32+16+2 =1330 (2) destination
port Number=(0017)16=(0000 0000 0001 0111)2=(24+22+21+1)10=16+4+2+1=23 (3) Serial number=(00000001)=1 (4)
Confirmation
number =(00000055) 16=(0000 0000 0000 0000 0000 0000 0101 0101) 2
= (26+24+22+1) 10=64+16+4+1=85
(5) The header length occupies 4 binary bits, 1 hexadecimal digit is calculated with 4B as a unit.
Because (5) 16=(5) 10=5
, the header length value=5×4=20B
(6) Because the destination port number is 23, so Access is TELNET server
(7) window value = (07FF) 16 = (0000 0111 1111 1111) 2 = (211-1) 10 = 2047
Answer:
(1) The source port number is 1330.
(2) The destination port number is 23.
(3) The serial number is 1.
(4) The confirmation value is 85.
(5) The head length value is 20B.
(6) The TELNET server is accessed.
(7) The window value is 2047.
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