As far as I can tell, SCHC has the same conceptual structure as almost
all of our tunnel protocols. Which we do not call extension headers.
Sure, they are not really upper layer protocols. But (although not
described the way John Day does) we understand that "upper" can be
recursion at the same layer.
If we declare SCHC to be an extension header, I do not know how we
answer the question the next time someone asks us "is this use an upper
layer header or an extension header?" As long as we provide an ability
to answer that question, I can live with either alternative.
Yours,
Joel
On 9/7/2022 6:05 PM, Robert Moskowitz wrote:
It might be that the datagram can be interrogated for the Next Header
and that MIGHT mean an update to 8200.
AH, you can find the NH. ESP not, as it is in the encrypted part.
But it is architecturally wrong to call what ROHC or SCHC as carrying
an upper layer protocol. They carry what is in our architecture a
Transport Layer protocol, acting in many ways as part of the IP layer
itself...
Fun.
On 9/7/22 17:35, Joel Halpern wrote:
My reading of 8200 is that an extension header MUST start with a one
byte "Next Header" field. SCHC does not. Therefore, it is a carried
/ upper layer protocol, not an extension header. Much like IPv6 (in
IPv6). Or UDP (with carrying an application protocol or carrying
some routing header like GRE, LISP, ...) or ...
Yours,
Joel
PS: I grant we are not fully consistent in this regard. ESP does not
have a next-header field. (AH does). But if we are going to
pretend that some headers are extensions headers and some are not, we
should try to be consistent with the description in 8200 (and 2460).
On 9/7/2022 4:57 PM, Robert Moskowitz wrote:
On 9/7/22 16:35, Carsten Bormann wrote:
On 7. Sep 2022, at 22:04, Bob Hinden <bob.hin...@gmail.com> wrote:
To clarify my question, it only relates to if SCHC should be added
to the IPv6 Extension Header Types registry. I continue to think
that adding it to the IP Protocol Number registry is fine.
I believe the answer should be the same as for 142 (RFC 5858),
which is not in the list.
I couldn’t find out quickly what an IPv6 Extension Header Type
is(*), so maybe that is an oversight for 142.
From my limited understanding and which Protocols are listed as
Extension Header Types and which not (other than 142), it is a
Protocol that transports other Protocols.
Though with that definition, I wonder how HIP got in the list.
It is fun to open a can of worms!
Grüße, Carsten
(*) An IP protocol number, apparently.
But what specifically does it make an IPv6 Extension Header Type as
well?
The references given in the registry don’t seem to say.
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