1. Lesson 4
The IPv6 Header

2. Lesson Objectives Structure of an IPv6 packet IPv4 header IPv6 header
IPv6 extension headers
IPv6 MTU
Upper layer checksums

3. Structure of an IPv6 Packet
Header
Extension
Headers
Upper Layer
Protocol Data Unit
Payload
IPv6 Packet

4. Structure of the IPv4 Header
Version
Internet Header Length
Type of Service
Total Length
Identification
Flags
Fragment Offset
Time to Live
Protocol
Header Checksum
Source Address
Destination Address
Options
. . .

5. Structure of the IPv6 Header
Version
Traffic Class
Flow Label
Payload Length
Next Header
Hop Limit
Source Address
Destination Address

6. Values of the Next Header Field
Value Header
0 Hop-by-Hop Options Header
6 TCP
17 UDP
41 Encapsulated IPv6 Header
43 Routing Header
44 Fragment Header
50 Encapsulating Security Payload
51 Authentication Header
58 ICMPv6
59 No next header
60 Destination Options Header

7. Comparing the IPv4 and IPv6 Headers
IPv4 Header Field Change in IPv6
Version New value of 6
Internet Header Length Removed
Type of Service Traffic Class field
Total Length Payload Length field
Identification Removed to Fragment header
Fragmentation Flags Removed to Fragment header
Fragment Offset Removed to Fragment header
Time to Live Hop Limit field
Protocol Next Header field
Header Checksum Removed
Source Address Same, new 128-bit length
Destination Address Same, new 128-bit length
Options Removed (extension headers)

8. The Chain of Pointers Formed by the Next Header field
IPv6 Header
Next Header = 6 (TCP)
TCP Segment
IPv6 Header
Next Header = 43 (Routing)
Routing Header
Next Header = 6 (TCP)
TCP Segment
IPv6 Header
Next Header = 43 (Routing)
Routing Header
Next Header = 51 (AH)
Authentication Header
Next Header = 6 (TCP)
TCP Segment

9. Extension Headers Order
1. Hop-by-Hop Options header
2. Destination Options header (for intermediate destinations when the Routing header is present)
3. Routing header
4. Fragment header
5. Authentication header
6. Encapsulating Security Payload header
7. Destination Options header (for the final destination)

10. Structure of the Hop-by-Hop Options Header
Next Header
Header Extension Length
Options
. . .

11. Structure of an Option
Option Type
Option Length
Option data
. . .

12. Structure of the Pad1 Option
Option Type
= 0

13. Structure of the PadN Option
Option Type
Option Length
Option data
= 1
. . .

14. Structure of the Jumbo Payload Option
Option Type
Option Length
Jumbo Payload Length
= 194
= 4

15. Structure of the Router Alert Option
Option Type
Option Length
Router Alert Value
= 5
= 2
= 0

16. Structure of the Destination Options Header
Next Header
Header Extension Length
Options
. . .

17. Structure of the Binding Update Option
Option Type
Option Length
Flags
Reserved
Prefix Length
Sequence Number
Lifetime
Sub-Options
= 198
. . .

18. Structure of the Binding Acknowledgement Option
Option Type
Option Length
Status
Sequence Number
Lifetime
Refresh
Sub-Options
= 7
. . .

19. Structure of the Binding Request Option
Option Type
Option Length
Sub-Options
= 8
. . .

20. Structure of the Home Address Option
Option Type
Option Length
Home Address
Sub-Options
= 201
. . .

21. Structure of the Routing Header
Next Header
Header Extension Length
Routing Type
Segments Left
Routing type-specific data
. . .

22. Structure of the Routing Type 0 Header
Next Header
Header Extension Length
Routing Type
Segments Left
Reserved
Address 1
Address N
. . .
= 0

23. Structure of the Fragment Header
Next Header
Reserved
Fragment Offset
More Fragments Flag
Identification

24. IPv6 Fragmentation Process
Original IPv6 Packet
Unfragmentable part
Fragmentable part
Unfragmentable part
Fragment header
First fragment
Unfragmentable part
Fragment header
Second fragment
Unfragmentable part
Fragment header
Third fragment

25. IPv6 Reassembly Process
Unfragmentable part
Fragment header
Fragmentable part
Unfragmentable part
Fragment header
Fragmentable part
Unfragmentable part
Fragment header
Fragmentable part
Unfragmentable part
Fragmentable part
Original IPv6 Packet

26. Structure of the Authentication Header
Next Header
Payload Length
Reserved
Security Parameters Index
Sequence Number
Authentication Data
. . .

27. Structure of the ESP Header and Trailer
Security Parameters Index
Sequence Number
Payload Data
Padding
Padding Length
Next Header
Authentication Data
. . .
. . .
. . .

28. IPv6 MTU Link layer must support a 1280-byte MTU
Otherwise, link layer must use a transparent fragmentation and reassembly scheme
For configurable MTU link layers, MTU size of at least 1500 bytes
Example: Maximum Receive Unit (MRU) of a Point-to-Point Protocol (PPP) link
Path MTU Discovery process uses the ICMPv6 Packet Too Big message

29. Structure of the IPv6 Pseudo-Header
Source Address
Destination Address
Upper Layer Packet Length
Zero
Next Header
= 0

30. Review Structure of an IPv6 packet IPv4 header IPv6 header
IPv6 extension headers
IPv6 MTU
Upper layer checksums