User Manual
UMN:CLI
V8102
99
Tab.4.1
provides an overview of the IPv6 header fields.
Field
Description
Version
Version of the protocol (4 Bits)
Priority
This field replaces the Type of Service field in IPv4. This field is used by sending
nodes and forwarding routers to identify and distinguish between different classes
or priorities of IPv6 packets. (1 Byte)
Flow label
This field distinguishes packets that require the same treatment, in order to facili-
tate the handling of real-time traffic. (20 Bits)
Payload Length
This field specifies the length of data carried after the IP header. Extension headers
are considered part of the payload and are therefore included in the calculation. (2
Bytes)
Next Header
This field contains a protocol number or a value for an extension header. (1 Byte)
Hop limit
The value indicates a number of hops. Every forwarding node decrements the
number by one. (1 Byte)
Source Address
This field contains the IP address of the originator of the packet.
Destination Address
This field contains the IP address of the intended recipient of the packet.
Tab. 5.3
Overview of IPv6 Header Fields
IPv6 Addressing
A typical IPv6 address consists of three parts-the global routing prefix, the subnet ID, and
the interface ID. An IPv6 address has 128 bits, or 16 bytes. The address is divided into
eight, 16-bit hexadecimal blocks, separated by colons.
FE80 :
0000 : 0000 : 0000
: 0202 : BA3FF : FE1E : 3210
FE80 :
0 : 0 : 0
: 202 : BA3FF : FE1E : 3210
FE80
::
202 : BA3FF : FE1E : 3210
Some abbreviations are possible to make the IPv6 address easier. As above 3 examples
are same IPv6 addresses. For instance, leading zeros in a 16-bit block can be omitted.
Sequences of 16 bit blocks containing only zeros are replaced with two colons :: (not
more than once per address).
IPv6 Prefix Notation
The prefix length specifies how many left-most bits of the address specify the prefix. The
prefix is used to identify the subnet that an interface belongs to and is used by routers for
forwarding.