Ipv4 header

The Presentation contains slides describing the details of IPv4 Header Format

1. IPv4 Header Deconstruction Pouyan Zamani

2. Sample Packet

3. Version

4. IHL (Internet Header Length) * 4 =in bytes

5. ToS (Type of Service)

6. ToS (Type of Service) 1000: Minimize delay 0100: Maximize throughput 0010: Maximize reliability 0001: Minimize monetary cost 0000: Normal service RFC 1349 > Obsolete! 11: Congestion Experienced 10: ECN Aware 01: ECN Aware 00: No ECN RFC 3168 > Newer!

7. ToS (Type of Service)

8. IP Datagram Length (Total Length)

9. IP ID (Identification)

10. Flags (3 bit)

11. Flags (3 bit) DF (Do not Fragment) : 0 means allow fragmentation; 1 means do not allow fragmentation . 0 : Reserved, must be zero. MF (More Fragments) : 0 means that this is the last fragment of the datagram; 1 means that additional fragments will follow.

12. Fragmentation Offset (13 bit) * 8 = in bytes

13. Fragmentation

14. Fragmentation

15. Fragmentation

16. Fragmentation

17. Fragmentation

18. Fragmentation

19. Fragmentation

20. Fragmentation

21. Questions About Fragments

22. Questions About Fragments

23. Questions About Fragments

24. IDS/IPS Challenges for Fragmentation

25. Ping of Death

26. Teardrop

27. TTL (Time to Live)

28. Protocol

29. Protocol ( https://www.eit.lth.se/ppplab/IPHeader.htm#Protocol ) Protocol Description Reserved 1 Internet Control Message Protocol (ICMP) 2 Internet Group Management Protocol (IGMP) 3 Gateway-to-Gateway Protocol (GGP) 4 IP (IP encapsulation) 5 Stream 6 Transmission Control Protocol (TCP) 8 Exterior Gateway Protocol (EGP) 9 Private Interior Routing Protocol 17 User Datagram Protocol (UDP)

30. Header Checksum

31. Header Checksum 4500 0073 0000 4000 4011 b861 c0a8 0001 c0a8 00c7 0035 e97c 005f 279f 1e4b 8180 4500 + 0073 + 0000 + 4000 + 4011 + c0a8 + 0001 + c0a8 + 00c7 = 2479C 2 + 479C = 479E (if another carry is generated by this addition, another 1 must be added to the sum) 479E > 1st complement (Binary) = B861

32. Header Checksum

33. Source IP

34. Destination IP

35. IP Options