RFC 8200, "Internet Protocol, Version 6 (IPv6) Specification", July 2017

Errata ID: 6248
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: Jingrong Xie
Date Reported: 2020-08-06

Section 4.5 says:

      The Per-Fragment headers must consist of the IPv6 header plus any
      extension headers that must be processed by nodes en route to the
      destination, that is, all headers up to and including the Routing
      header if present, else the Hop-by-Hop Options header if present,
      else no extension headers.

It should say:

      The Per-Fragment headers must consist of the IPv6 header plus any
      extension headers that must be processed by nodes en route to the
      destination. In the recommended order of extension headers listed 
      in section 4.1, the Per-Fragment headers include all headers up to 
      and including the Routing header if present, else the Hop-by-Hop 
      Options header if present, else no extension headers. In case the
      order of extension headers is specified, the Per-Fragment headers 
      include all headers that is required to be before the Fragment Header.

Notes:

1. As specified in in section 4.1 of RFC8200, the recommended order of existing extension headers could be revised, and there have been some examples in the RFCs that do such revision: RFC7837, RFC6275 and its related RFCs, RFC3775/RFC3776/RFC4784.
2. RFC6275 requires DoH carrying a special option to be placed before Fragmentation header. This gives an example how to support Fragmentation with the order of extension headers revised.
3. As specified in section 4.8 of RFC8200, new extension headers could be defined, and there may be some new Per-fragment header(s) defined requiring en route processing with fragmentation support.

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