IPv 6 Tutorial Module 1 IPv 6 Protocol

IPv 6 Tutorial Module 1: IPv 6 Protocol Structure Dan Campbell, President Millennia Systems, Inc.

Contents • IPv 4 header review • IPv 6 header construction – Version – Traffic Class – Flow Label – Payload Length – Next Header – Hop Limit – Addresses • Extension headers – Hop-by-Hop – Destination Options – Routing – Fragmentation – Authentication Header – Encapsulating Security Payload – Mobility www. Millennia. Systems. com 2

Review: The IPv 4 header consists of 15 fields (including 3 flags and the options and padding) Version – Indicates IP version 4 IPv 4 Header Ver To. S IHL Fragment Offset Fla gs Identifier TTL Total Length Protocol Header Checksum IHL = Internet Header Length, which must be specified since the options allow for varying length headers To. S = Type of Service, which allows for differentiating packets into different classes for specific forwarding treatment. Total Length – indicates the total length of the IP packet, including the header, upper layer protocols and payload Identifier – Unique identifier for the packet, seldom used Flags – Used to indicate fragmentation Fragment Offset – indicates this fragment’s position in the datagram Source Address Destination Address Options and Padding TTL = Time to Live, the packet life remaining in router hops (and initially in seconds) Protocol – The next protocol header above IP, e. g. , TCP, UDP, IPSec, etc. Header Checksum – used in checking to ensure the header was received as it was transferred and without error Addresses – 32 -bit designators for the sending (source) host and receiving (destination) host Options – Seldom used options set by sender Several of the fields initially envisioned for use either went unused, became obsolete in favor of other technologies or OSI layers, or morphed into other uses www. Millennia. Systems. com 3

Review: The IPv 4 header can vary in size IPv 4 Header Ver To. S IHL Fragment Offset Fla gs Identifier TTL Total Length Protocol Header Checksum 20 bytes Source Address Destination Address Options and Padding Header size can vary if options are used The IPv 6 header was designed to optimize the protocol and fix the header to a consistent size to expedite packet forwarding www. Millennia. Systems. com 4

IPv 6 set out to retire obsolete IPv 4 header fields IPv 4 Header Ver To. S IHL Fragment Offset Fla gs Identifier TTL Total Length Protocol Header Checksum Source Address IPv 4 header fields that were obsolete or superfluous to other protocol layers were identified for deletion or modification Destination Address Options and Padding www. Millennia. Systems. com 5

IPv 6 header is fixed to 40 bytes IPv 4 Header To. S IHL Total Length Fragment Offset Fla gs IH Identifier L Ver Internet Header Length (IHL) field is no longer needed TTL Protocol Header Checksum Source Address Destination Address Options and Padding www. Millennia. Systems. com 6

The largely unused Identification field was trashed IPv 4 Header To. S Ver Total Length Fragment Offset Fla gs Identifier r ifie TTL Protocol Header Checksum nt Ide Source Address Destination Address Options and Padding www. Millennia. Systems. com 7

The 3 -bit Flags field is no longer needed IPv 4 Header To. S Ver Total Length Fragment Offset Fla gs TTL Protocol Header Checksum Flags dealt primarily with Fragmentation, which has been moved to an optional extension header a Fl s g Source Address Destination Address Options and Padding www. Millennia. Systems. com 8

Fragmentation by routers in IPv 6 is not permitted IPv 4 Header To. S Ver Total Length Fragment Offset TTL Protocol Header Checksum Hosts must fragment packets. Fragmentation was moved to an optional extension header t en m t ag se Fr Off Source Address Destination Address Options and Padding www. Millennia. Systems. com 9

Header checksum was deemed redundant IPv 4 Header To. S Ver TTL Protocol Total Length Header Checksum Layer 2 and upper layer protocols are performing checksums, so an IP header checksum is unnecessary um ks c e Ch er d a He Source Address Destination Address Options and Padding www. Millennia. Systems. com 10

The Options field was removed IPv 4 Header To. S Ver Options forms the basis of the Extension Header concept Total Length TTL Protocol din g n sa tion Op ad d. P Source Address Destination Address Options and Padding www. Millennia. Systems. com 11

The Version field was maintained IPv 6 Header IPv 4 Header To. S Ver TTL Total Length Protocol Source Address Ver Of course, the version numbers was changed to “ 6” Destination Address www. Millennia. Systems. com 12

To. S field was kept but renamed to Traffic Class IPv 6 Header IPv 4 Header To. S Ver TTL Total Length Protocol Source Address Ver Traffic Class is functionally identical to Diff. Serv (DSCP) Destination Address www. Millennia. Systems. com 13

A new Qo. S Field called Flow Label was added IPv 6 Header IPv 4 Header To. S Ver TTL Total Length Protocol Source Address Ver Traffic Class Flow Label Flow label allows for flow identification at layer 3 and within the IP header, instead of a mix of layer 3 and 4 parameters. Destination Address www. Millennia. Systems. com 14

Total Length field changed to Payload Length IPv 6 Header IPv 4 Header To. S Ver Total Length Ver Traffic Class Flow Label Payload Length TTL Protocol Source Address Destination Address Header length is fixed to 40 bytes, thus only the payload length needs be identified www. Millennia. Systems. com 15

Protocol field was changed to Next Header IPv 6 Header IPv 4 Header To. S Ver Total Length Ver Traffic Class Payload Length TTL Flow Label Next Header Protocol Source Address Destination Address Next Header could indicate the layer 4 protocol (TCP, UDP), ICMP, another layer 3 IP protocol or an IPv 6 extension header. www. Millennia. Systems. com 16

TTL field was kept but changed to Hop Limit IPv 6 Header IPv 4 Header To. S Ver Total Length Ver Traffic Class Payload Length TTL Flow Label Next Header Hop Limit Protocol Source Address Destination Address Over time, the “time” to live field came to mean “router hop count”, thus it was changed in IPv 6 to “hop limit” www. Millennia. Systems. com 17

Source and Destination addresses are increased from 32 to 128 bits each IPv 6 Header IPv 4 Header To. S Ver Total Length Ver Traffic Class Flow Label Payload Length TTL Next Header Hop Limit Protocol Source Address (128 bits) Destination Address (128 bits) www. Millennia. Systems. com 18

IPv 6 basic header length Ver Traffic Class Flow Label Payload Length Next Header Source Address Hop Limit Always 40 bytes Destination Address Extension headers are added after the addresses, indicated by the Next Header value www. Millennia. Systems. com 19

No Next Header Ver Next Header value = 59 Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address www. Millennia. Systems. com 20

Hop-by-Hop header Ver Next Header value = 0 Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Provides information that must be examined by every node along the packet’s delivery path, unlike other headers, which are only viewed by the receiving node. Destination Address Hop-by-Hop Options Header www. Millennia. Systems. com 21

Destination Options header Ver Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address Next Header value = 60 Carries optional information that needs to be examined by only the packet’s destination node(s) Hop-by-Hop Options Header Destination Options header follows Hop-by. Hop header only when the Routing header is present. www. Millennia. Systems. com 22

Routing header Ver Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address Hop-by-Hop Options Header Next Header value = 43 Used by an IPv 6 source to list one or more intermediate nodes to be visited on the way to a packet’s destination. Provides a means to do source or policy routing. Destination Options Header Routing Header www. Millennia. Systems. com 23

Fragment header Ver Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address Hop-by-Hop Options Header Destination Options Header Next Header value = 44 Indicates that the datagram was fragmented and what position this fragment is in the overall datagram Routing Header Fragment Header www. Millennia. Systems. com 24

Authentication Header Ver Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address Hop-by-Hop Options Header Destination Options Header Routing Header Next Header value = 51 Provides authentication of the packet Fragment Header Authentication Header Same as AH in IPSec for IPv 4 www. Millennia. Systems. com 25

Encapsulating Security Payload header Ver Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address Hop-by-Hop Options Header Destination Options Header Routing Header Fragment Header ESP provides confidentiality and integrity of the packet through encryption Authentication Header Encapsulating Security Payload Header Next Header value = 50 Same as ESP in IPSec for IPv 4 www. Millennia. Systems. com 26

Mobility header Ver Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address Hop-by-Hop Options Header Fragment Header Used by mobile nodes, correspondent nodes and home agents in messaging related to the creation and management of mobile bindings Authentication Header Encapsulating Security Payload Header Next Header value = 135 Mobility Header www. Millennia. Systems. com 27

Destination Options header Ver Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address Hop-by-Hop Options Header Fragment Header Authentication Header Encapsulating Security Payload Header Destination Options header moves to the end if the Routing header is not present Mobility Header Next Header value = 60 Destination Options Header www. Millennia. Systems. com 28

Next header is TCP Ver Next Header value = 6 Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address TCP Header www. Millennia. Systems. com 29

Next header is UDP Ver Next Header value = 17 Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address UDP Header www. Millennia. Systems. com 30

Next header is ICMPv 6 Ver Next Header value = 58 Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address ICMPv 6 Header www. Millennia. Systems. com 31

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