Information Technology Reference
In-Depth Information
Address autoconfiguration:
This capability provides for dynamic assignment of
IPv6 addresses. IPv6 hosts can automatically configure themselves, with or without a
Dynamic Host Configuration Protocol (DHCP) server. Stateful and stateless autocon-
figuration is supported.
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Flow labeling capability:
Instead of the Type of Service field in IPv4, IPv6 enables
the labeling of packets belonging to a particular traffic class for which the sender re-
quests special handling, such as quality of service (QoS) and real-time service. This
support aids specialized traffic, such as real-time voice or video.
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Security capabilities:
IPv6 includes features that support authentication and pri-
vacy. IP Security (IPsec) is a requirement.
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Maximum transmission unit (MTU) path discovery:
IPv6 eliminates the need to
fragment packets by implementing MTU path discovery before sending packets to a
destination.
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Site multihoming:
IPv6 allows multihoming by allowing hosts to have multiple IPv6
addresses and networks to have multiple IPv6 prefixes, which facilitates connection
to multiple ISPs.
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Support for mobility and multicast:
Mobile IPv6 allows for IPv6 nodes to change
its location on a network and maintain its existing connection. The Mobile node is al-
ways reachable via one permanent address.
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Eliminate the use of broadcasts:
IPv6 reduces unnecessary bandwidth by elimi-
nating the use of broadcasts, replacing it with multicasts.
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This section covers each field of the IPv6 header. The IPv6 header is simpler than the IPv4
header. Some IPv4 fields have been eliminated or changed to optional fields. The IPv6
header size is 40 bytes. The fragment offset fields and flags in IPv4 have been eliminated
from the header. IPv6 adds a flow label field for QoS mechanisms to use.
Key
To p i c
The use of 128 bits for source and destination addresses provides a significant improve-
ment over IPv4. With 128 bits, there are 3.4 * 10
38
or 34 billion billion billion billion IPv6
addresses, compared to only 4.3 billion IPv4 addresses.
IPv6 improves over IPv4 by using a fixed-length header. The IPv6 header appears in
Figure 9-1.
The following is a description of each field in the IP header:
Version:
This field is 4 bits long. It indicates the format, based on the version number,
of the IP header. These bits are set to 0110 for IPv6 packets.
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Traffic Class:
This field is 8 bits in length. It describes the class or priority of the
IPv6 packet and provides functionality similar to the IPv4 Type of Service field.
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Flow Label:
This field is 20 bits in length. It indicates a specific sequence of packets
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data (voice and video).
