Subject: Extension header order in draft-leddy-6man-truncate-04

From: "C. M. Heard" <[email-masked]>
Date: Sat, 30 Jun 2018 13:08:18 -0700

Hello Ron,

It occurs to me that the proper order of headers when the "Truncation
Eligible" or "Truncated Packet" options appear should be:

      IPv6 header
      Hop-by-Hop Options header
      Destination Options header ("Truncation Eligible", "Truncated
Packet" , or note 1)

      Routing header
      Authentication header (note 2)
      Encapsulating Security Payload header (note 2)
      Destination Options header (note 3)
      Upper-Layer header

      note 1: for options to be processed by the first destination that
              appears in the IPv6 Destination Address field plus
              subsequent destinations listed in the Routing header.

      note 2: additional recommendations regarding the relative order of
              the Authentication and Encapsulating Security Payload
              headers are given in [RFC4303
<https://tools.ietf.org/html/rfc4303>].

      note 3: for options other than "Truncated Packet" that are to be

              processed only by the final destination of the packet.

My reasoning is that (a) we want "Truncation Eligible" to be processed by
the first destination if in the IPv6 header and subsequent destinations
listed in the routing header and (b) we want Truncated Packet" to be
processed before the Authentication Header (if one is present) at the final
destination. Note that case (b) is necessary since the truncated packet
will fail the AH integrity check. If AH were processed first, the
destination node would not send the desired PTB message,

Do you agree?

Mike Heard