Lesson 4 The IPv6 Header

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

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

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 . . .

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

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

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)

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

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)

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

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

Structure of the Pad1 Option Option Type = 0

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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