Ipv4 Packet Header; Simplified Ipv6 Packet Header - Cisco Nexus 7000 Series Configuration Manual

Chapter 3 Configuring IPv6
S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m .

IPv4 Packet Header

The basic IPv4 packet header has 12 fields with a total size of 20 octets (160 bits) (see
12 fields may be followed by an Options field, which is followed by a data portion that is usually the
transport-layer packet. The variable length of the Options field adds to the total size of the IPv4 packet
header. The shaded fields of the IPv4 packet header are not included in the IPv6 packet header.
Figure 3-8
Version

Simplified IPv6 Packet Header

The basic IPv6 packet header has 8 fields with a total size of 40 octets (320 bits) (see
Fragmentation is handled by the source of a packet and checksums at the data link layer and transport
layer are used. The User Datagram Protocol (UDP) checksum checks the integrity of the inner packet
and the basic IPv6 packet header and Options field are aligned to 64 bits, which can facilitate the
processing of IPv6 packets.
Table 3-2
Table 3-2
Field
Version
Traffic Class
Flow Label
Payload Length
OL-20002-02
IPv4 Packet Header Format
Hd Len Type of Service
Identification
Time to Live Protocol
Options
lists the fields in the basic IPv6 packet header.
Basic IPv6 Packet Header Fields
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
Total Length
Flags
Header Checksum
Source Address
Destination Address
Data Portion
32 bits
Description
Similar to the Version field in the IPv4 packet header, except that the
field lists number 6 for IPv6 instead of number 4 for IPv4.
Similar to the Type of Service field in the IPv4 packet header. The
Traffic Class field tags packets with a traffic class that is used in
differentiated services.
New field in the IPv6 packet header. The Flow Label field tags
packets with a specific flow that differentiates the packets at the
network layer.
Similar to the Total Length field in the IPv4 packet header. The
Payload Length field indicates the total length of the data portion of
the packet.
Information About IPv6
Figure
Fragment Offset
Padding
Figure
3-8). The
20
octets
Variable
length
3-9).
3-9