1.2 HEADER FORMAT

In the case where greater than one extension header is employed within the same packet, those headers should be listed in the following sequence: IPv6 header, Hop-by-Hop Options header, Destination Options header, Routing header, Fragment header, Authentication header, Encapsulating, Security Payload header, Destination Options header, and the Upper-Layer header.

It is important to note that each extension header needs to appear only one time, with the exception that the Destination Options header needs to appear no more than two times the first time prior to a Routing header and one time prior to the Upper-Layer header.

Under the condition that the Upper-Layer header is an additional IPv6 header (e.g., IPv6 being tunneled over or encapsulated within IPv6) it can be succeeded by its own extension headers. The same ordering methods must approve each header.

IPv6 nodes need both to accept and try to operate on extension headers in any given order which occurs any number of times within the same packet. However, there is the exception of the Hop-by-Hop Options header that is restrained from materializing just after an IPv6 header.