TMP

IPv6 – Header Zusammenfassung

Review: The IPv4 header consists of 15 fields including 3 flags and the options and padding

Version – Indicates IP version 4

IPv4 Header IHL = Internet Header Length, which must be specified since the options allow for
varying length headers
ToS = Type of Service, which allows for differentiating packets into different classes
for specific forwarding treatment.

Ver IHL ToS Total Length

Total Length – indicates the total length of the IP packet, including the header, upper
Fragment layer protocols and payload
Identifier Flag
s Offset
Identifier – Unique identifier for the packet, seldom used

TTL Protocol Header Checksum Flags – Used to indicate fragmentation

Fragment Offset – indicates this fragment’s position in the datagram
Source Address 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.
Destination Address
Header Checksum – used in checking to ensure the header was received as it was
transferred and without error
Options and Padding
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

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Review: The IPv4 header can vary in size

IPv4 Header

Ver IHL ToS Total Length

Flag
Fragment
Identifier
s Offset

TTL Protocol Header Checksum 20 bytes
Source Address

Destination Address

Options and Padding Header size can vary if options are used

The IPv6 header was designed to optimize the protocol and fix the header to a consistent size to expedite packet forwarding

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IPv6 set out to retire obsolete IPv4 header fields

IPv4 Header

Ver IHL ToS Total Length

Fragment
Identifier
Fla
gs
Offset IPv4 header fields that were obsolete
or superfluous to other protocol
TTL Protocol Header Checksum
layers were identified for deletion or
Source Address
modification

Destination Address

Options and Padding

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IPv6 header is fixed to 40 bytes

IPv4 Header Internet Header Length (IHL) field is no

Ver IHL ToS Total Length

longer needed

Flag
Fragment
Identifier
s Offset

TTL Protocol Header Checksum

Source Address

Destination Address

Options and Padding

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The largely unused Identification field was trashed

IPv4 Header

Ver ToS Total Length

Flag
Fragment
Identifier
s Offset

TTL Protocol Header Checksum

Source Address

Destination Address

Options and Padding

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The 3-bit Flags field is no longer needed

Flags dealt primarily with Fragmentation,
IPv4 Header which has been moved to an optional
extension header

Ver ToS Total Length

Flag
Fragment
s Offset

TTL Protocol Header Checksum

Source Address

Destination Address

Options and Padding

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Fragmentation by routers in IPv6 is not permitted

Hosts must fragment packets.
IPv4 Header Fragmentation was moved to an optional
extension header

Ver ToS Total Length

Fragment
Offset

TTL Protocol Header Checksum

Source Address

Destination Address

Options and Padding

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Header checksum was deemed redundant

Layer 2 and upper layer protocols are
IPv4 Header performing checksums, so an IP header
checksum is unnecessary

Ver ToS Total Length

TTL Protocol Header Checksum

Source Address

Destination Address

Options and Padding

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The Options field was removed

Options forms the basis of the Extension
IPv4 Header Header concept

Ver ToS Total Length

TTL Protocol

Source Address

Destination Address

Options and Padding

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The Version field was maintained

IPv4 Header IPv6 Header

Ver ToS Total Length Ver

Of course, the version
TTL Protocol
numbers was changed to
Source Address
“6”

Destination Address

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ToS field was kept but renamed to Traffic Class

IPv4 Header IPv6 Header
Traffic

Ver ToS Total Length Ver

Class

Traffic Class is functionally
TTL Protocol
identical to DiffServ (DSCP)
Source Address

Destination Address

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A new QoS Field called Flow Label was added

IPv4 Header IPv6 Header
Traffic

Ver ToS Total Length Ver Flow Label

Class

Flow label allows for flow
TTL Protocol identification at layer 3 and within
the IP header, instead of a mix of
Source Address
layer 3 and 4 parameters.
Destination Address

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Total Length field changed to Payload Length

IPv4 Header IPv6 Header
Traffic

Ver ToS Total Length Ver Flow Label

Class

Payload Length

TTL Protocol

Header length is fixed to 40
Source Address
bytes, thus only the payload
Destination Address
length needs be identified

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Protocol field was changed to Next Header

IPv4 Header IPv6 Header
Traffic

Ver ToS Total Length Ver Flow Label

Class

Next Header
Payload Length

TTL Protocol

Next Header could indicate the layer 4
Source Address
protocol (TCP, UDP), ICMP, another
layer 3 IP protocol or an IPv6 extension
Destination Address
header.

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TTL field was kept but changed to Hop Limit

IPv4 Header IPv6 Header
Traffic

Ver ToS Total Length Ver Flow Label

Class

Next Header Hop
Payload Length
Limit

TTL Protocol

Over time, the “time” to live field came
Source Address
to mean “router hop count”, thus it
Destination Address
was changed in IPv6 to “hop limit”

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Source and Destination addresses are increased from 32 to 128 bits each

IPv4 Header IPv6 Header
Traffic

Ver ToS Total Length Ver Flow Label

Class

Next Header Hop
Payload Length
Limit

TTL Protocol

Source Address
Source Address (128 bits)

Destination Address

Destination Address
(128 bits)

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IPv6 basic header length

Traffic Class
Ver Flow Label

Next Header Hop
Payload Length
Limit
Always 40 bytes
Source Address

Destination Address

Extension headers are
added after the
addresses, indicated by
the Next Header value

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No Next Header

Traffic Class
Ver Flow Label

Next Header value = 59 Payload Length

Next Header Hop
Limit

Source Address

Destination Address

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Hop-by-Hop header

Traffic Class
Ver Flow Label

Next Header value = 0 Payload Length

Next Header Hop
Limit

Source Address

Destination Address

Provides information that must be examined by every Hop-by-Hop Options Header node along the packet’s delivery path, unlike other headers, which are only viewed by the receiving node.

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Destination Options header

Traffic Class
Ver Flow Label

Next Header Hop
Payload Length
Limit

Source Address

Destination Address

Next Header value = 60 Hop-by-Hop Options Header

Destination Options header
Destination Options Header
follows Hop-by-Hop header

Carries optional only when the Routing information that needs to header is present. be examined by only the packet’s destination node(s)

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Routing header

Traffic Class
Ver Flow Label

Next Header Hop
Payload Length
Limit

Source Address

Destination Address

Hop-by-Hop Options Header

Next Header value = 43 Destination Options Header

Used by an IPv6 source to Routing Header 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.

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Fragment header

Traffic Class
Ver Flow Label

Next Header Hop
Payload Length
Limit

Source Address

Destination Address

Hop-by-Hop Options Header

Destination Options Header

Next Header value = 44 Routing Header

Indicates that the datagram Fragment Header was fragmented and what position this fragment is in the overall datagram

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Authentication Header

Traffic Class
Ver Flow Label

Next Header Hop
Payload Length
Limit

Source Address

Destination Address

Hop-by-Hop Options Header

Destination Options Header

Routing Header

Next Header value = 51 Fragment Header

Provides authentication of Authentication Header Same as AH in IPSec for the packet IPv4

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Encapsulating Security Payload header

Traffic Class
Ver Flow Label

Next Header Hop
Payload Length
Limit

Source Address

Destination Address

Hop-by-Hop Options Header

Destination Options Header

Routing Header

Fragment Header

ESP provides

Next Header value = 50

confidentiality and integrity Authentication Header

of the packet through Same as ESP in IPSec for encryption Encapsulating Security Payload Header

IPv4

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Mobility header

Traffic Class
Ver Flow Label

Next Header Hop
Payload Length
Limit

Source Address

Destination Address

Hop-by-Hop Options Header

Fragment Header

Used by mobile nodes, Authentication Header correspondent nodes and home agents in Encapsulating Security Payload Header Next Header value = 135 messaging related to the creation and management Mobility Header of mobile bindings

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Destination Options header

Traffic Class
Ver Flow Label

Next Header Hop
Payload Length
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 Mobility Header

Next Header value = 60

if the Routing header is not present Destination Options Header

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Next header is TCP

Traffic Class
Ver Flow Label

Next Header value = 6 Payload Length

Next Header Hop
Limit

Source Address

Destination Address

TCP Header

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Next header is UDP

Traffic Class
Ver Flow Label

Next Header value = 17 Payload Length

Next Header Hop
Limit

Source Address

Destination Address

UDP Header

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Next header is ICMPv6

Traffic Class
Ver Flow Label

Next Header value = 58 Payload Length

Next Header Hop
Limit

Source Address

Destination Address

ICMPv6 Header

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