54 lines
2.1 KiB
Plaintext
54 lines
2.1 KiB
Plaintext
Hello,
|
|
|
|
This folder contains details for Test_Case3.
|
|
|
|
1. Version = 4
|
|
2. IHL = 5, which indicates 20 bytes.
|
|
3. Type Of Service (ToS) = 0,
|
|
4. Total Length = 40 bytes, which is 28 in hex.
|
|
5. Identification = 3,
|
|
6. Flags = The flags are set to zero,
|
|
7. Fragment Offset = 0 for now,
|
|
8. Time To Live (TTL) = 40s, which is 28 in hex.
|
|
9. Protocol = 6, which indicates TCP protocol is used.
|
|
10. Header Checksum = initially zero and then changed to the sum of 16 bit values of header + data.
|
|
11. Source Address = 172.168.5.3, which is aca8 0503 in hex.
|
|
12. Destination Address = 172.168.5.4, which is aca8 0504 in hex.
|
|
13. Source Port = 5555, which is 15b3 in hex.
|
|
14. Destination Port = 6666, which is 1a0a in hex.
|
|
15. Sequence Number = 0,
|
|
16. Acknowledgement Number = 0,
|
|
17. Data Offset = 5, as it indicates the number of bytes after which data starts. The number 5 represents that data starts after 20 bytes. The data offset value is scaled by 4.
|
|
18. RSV = The reserved bits are set to zero for now.
|
|
19. Flgas: set according to the packet type.
|
|
20. Window Size = 0
|
|
21. TCP Checksum = initially zero, then:
|
|
(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.
|
|
22. Urgent Pointer = 0 for now.
|
|
|
|
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] = 0x03, 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] = 0xac, Source IP,
|
|
header[13] = 0xa8, Source IP,
|
|
header[14] = 0x05, Source IP,
|
|
header[15] = 0x03, Source IP,
|
|
header[16] = 0xac, Destination IP,
|
|
header[17] = 0xa8, Destination IP,
|
|
header[18] = 0x05, Destination IP,
|
|
header[19] = 0x04, Destination IP,
|
|
|
|
The value of IP_Header_Checksum comes out to be: 2f76.
|