diff --git a/Test_Cases/Test_Case1/readme b/Test_Cases/Test_Case1/readme index 1c2f1de..b0cf9dd 100644 --- a/Test_Cases/Test_Case1/readme +++ b/Test_Cases/Test_Case1/readme @@ -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 \ No newline at end of file