Standard Ipv6 Headers; Extension Headers; Figure 13: Ipv4 And Ipv6 Header Comparison; Configuring Ipv6 - Juniper IGP - CONFIGURATION GUIDE V11.1.X Configuration Manual

Figure 13: IPv4 and IPv6 Header Comparison

Standard IPv6 Headers

IPv6 packet headers contain many of the fields found in IPv4 packet headers; some
of these fields differ from IPv4. (See Figure 13 on page 127.)
The 40-byte IPv6 header consists of the following eight fields:
Version Indicates the version of the Internet Protocol.
Traffic class Previously the type-of-service (ToS) field in IPv4, the traffic class
field defines the class-of-service (CoS) priority of the packet. However, the
semantics for this field (for example, DiffServ code points) are identical to IPv4.
Flow label The flow label identifies all packets belonging to a specific flow (that
is, packet flows requiring a specific class of service [CoS]); routers can identify
these packets and handle them in a similar fashion.
Payload length Previously the total length field in IPv4, the payload length field
specifies the length of the IPv6 payload.
Next header Previously the protocol field in IPv4, the Next Header field indicates
the next extension header to examine.
Hop limit Previously the time-to-live (TTL) field in IPv4, the hop limit indicates
the maximum number of hops allowed.
Source address Identifies the address of the source node sending the packet.
Destination address Identifies the final destination node address for the packet.

Extension Headers

In IPv6, extension headers are used to encode optional Internet-layer information.
Extension headers are placed between the IPv6 header and the upper-layer header
in a packet.
Chapter 2: Configuring IPv6
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IPv6 Overview