Zte ZXR10 T1200, Руководство пользователя

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ZXR10 T600/T1200 User Manual (IPv6 Volume)
Table 1 and Table 2 are the header formats of IPv4 and IPv6 re-
spectively. (Numbers in the tables refer to bit numbers.)
T
ABLE
1 IP
V
4 H
EADER
F
ORMAT
4 - Version 4 – Header
Length 8 - Service
Type 16 - Data Packet Length
16 – Identifier 4 – Flags 12 -
Fragmented
Offset
8 – Time to Live (TTL) 8 – Trans-
mission Pro-
tocol 16 – Header Checksum
32 - Source Address
32 - Destination Address
24 – Options 8 - Padding
T
ABLE
2 IP
V
6 H
EADER
F
ORMAT
4 - Version 4 – Priority 24 – Flow Label
16 – Payload Length 8 – Next
Header 8 – HOP
Limit
128 - Source Address
128 - Destination Address
IPv6 header is simpler than IPv4 header in structure because many
fields in IPv4 header that are not frequently used are deleted from
IPv6 header, and put into its options and header extension, which
are defined more strictly.
� IPv4 contains ten fields with fixed length, two address spaces
and some options, while IPv6 contains only six fields and two
address spaces.
� Although IPv6 header occupies 40 bytes, which is 1.6 times
of IPv4 header with 24-bytes, it does not consume too much
memory capacity due to its fixed length (the length of the IPv4
header is variable).
� The following six fields are deleted from IPv4 header: header
length, type of service, identifier, flags, fragmented offsets
and header checksum.
Names and some functions of the
three fields of total length, protocol and Time to Live ( TTL )
are changed, and its optional functions is completely changed.
Apart from this, two fields are added: priority and flow label.
� IPv6 header format is greatly simplified, which effectively pares
down overhead of processing header by a router or switch. At
the same time, IPv6 enhances the support to the extension
header and options, which not only allows more efficient for-
warding, but also provides sufficient supports for future load
of new applications to networks. Each IPv6 packet can have 0,
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