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Update 'Test_Cases/Test_Case1/readme'

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Sana147 2023-05-08 00:18:17 +00:00
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commit d06054386c
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Test_Cases/Test_Case1/readme
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@ -5,7 +5,7 @@ The values for the header fields are:
1. Verison = 4, to indicate IPv4 version is used.
2. IHL = 5, which indicates 20 bytes.
3. Type of Service = 0,
4. Total Window size = 40, which is 28 in hex. The total windows size contains the total lenght of IP header plus data.
4. Total Length = 40, which is 28 in hex. The total windows size contains the total lenght of IP header plus data.
5. Identification = 0001,
6. Flags = All flags are set to zero,
7. Fragment Offset = For now, there is no fragment offset so, this value is set to 0.
@ -28,6 +28,32 @@ For the FIN+ACK packet, the FIN and ACK flags in the header have a value of 1.
(i) Concatenate TCP Pseudo header (Protocol, Source IP, Destination IP, Total Length) with TCP header and TCP data. This creates a big integer.
(ii) Convert this integer to binary and compute bit wise 1's complement.
The value of header comes out to be:
header = {}
header[0] = 0x45, Version, IHL
header[1] = 0x00, TOS,
header[2] = 0x00, Total Length,
header[3] = 0x28, Total Length,
header[4] = 0x00, Identification,
header[5] = 0x01, Identification,
header[6] = 0x00, Flags + Fragment Offset,
header[7] = 0x00, Flags + Fragment Offset,
header[8] = 0x28, TTL
header[9] = 0x06, Protocol
header[10] = 0x00, Header Checksum
header[11] = 0x00, Header Checksum
header[12] = 0xc8, Source IP,
header[13] = 0xcc, Source IP,
header[14] = 0x0a, Source IP,
header[15] = 0x0c, Source IP,
header[16] = 0xc8, Source IP,
header[17] = 0xcc, Source IP,
header[18] = 0x0a, Source IP,
header[19] = 0x0e, Source IP,
References:
1. https://www.thegeekstuff.com/2012/05/ip-header-checksum/
2. https://www.tutorialspoint.com/calculation-of-tcp-checksum