Re: [Int-area] New Version Notification for draft-herbert-ipv4-eh-03.txt

[Tom Herbert <[e-mail]>]

On Thu, Mar 21, 2024 at 2:36 PM Brian E Carpenter
<[e-mail]> wrote:
>
> On 22-Mar-24 09:04, Tom Herbert wrote:
> > On Thu, Mar 21, 2024 at 12:46 PM Templin (US), Fred L
> > <Fred.L.Templin=[e-mail]> wrote:
> >>
> >> Brian,
> >>
> >>> Why should the IETF spend effort on upgrading IPv4 capabilities at this point?
> >>
> >> For air/land/sea/space mobile Internetworking, we expect to engage steady-state IP
> >> fragmentation over some paths, but IPv4 will still be in the picture for a long time to
> >> come and IPv4 fragmentation has known limitations (e.g., RFC4963). IPv4 fragmentation
> >> using the IPv6 Fragment Header (adapted for IPv4) would address many of the issues.
> >>
> >> This is just to name one example. Another example is adapting IPv6 HBH options to
> >> carry IP parcels and Advanced Jumbos in IPv4 packets for operation over networks
> >> where IPv4 will still be used for the long term.
> >>
> >> IPv4 is going to be around for a long time in many networks, so making it work
> >> more like IPv6 seems like a useful improvement.
> >
> > Yes, we still have IPv4 users that need the capabilities. If everyone
> > were on IPv6 we wouldn't need this.
>
> So this proposal hinders IPv6 adoption. I think it would lead to an
> "interesting" IETF Last Call discussion.

Hi Brian,

Well I knew going in this would be provocative :-)

Actually, I believe this accelerates IPv6 adoption. We're essentially
unifying portions IPv4 and IPv6 so that makes a complete transition
that much easier. If people adopt the hacky alternatives I mentioned
then it's likely they'll just propagate those into IPv6 (that's
another effect we've seen, some people "adopt" IPv6 but still treat it
like IPv4).  Besides, we've been working on IPv6 for what, thirty
years, I really doubt *this* is the thing that will get the blame for
how long adoption is taking :-).

>
> >
> > To be a little more direct, one purpose of the draft is to nullify a
> > persistent argument against using extension headers: "They don't work
> > with IPv4".
>
> I was told in Seattle in March 1994 that the Internet was opaque to
> new IPv4 options - that's the main reason I stopped work on
> https://datatracker.ietf.org/doc/draft-carpenter-aeiou/, in fact.
> I understand that you've bypassed that problem in the ipv4-eh
> design, but surely the deployment problem here will be worse than
> it is for IPv6 extension headers - IPv4 middleboxes and firewalls
> are much more widely deployed than they were in 1994.
>
> > We've seen the same story play out in a number of proposals. It goes
> > like this: "We want to annotate packets with ancillary network layer
> > information like extension headers are designed for, but we still have
> > a large number of users still on IPv4 and so using extension headers
> > is a showstopper." Unfortunately, all the alternatives for getting
> > similar functionality in IPv4 have proven to be essentially hacks
> > (like having intermediate devices parse UDP payloads, or somehow use
> > VLAN as metadata and turn Ethernet into an E2E protocol). And of
> > course, IP options are "not an option"...
>
> Right. But there you've implicitly accepted the limited domain
> model, which many in the IETF consider heresy.

Sure, but there's also many in IETF that realize the practicality of
the limited domain model in real world deployment.

Tom

>
>     Brian
>
> >
> > Tom
> >
> >>
> >> Fred
> >>
> >>> -----Original Message-----
> >>> From: Int-area <[e-mail]> On Behalf Of Brian E Carpenter
> >>> Sent: Thursday, March 21, 2024 11:59 AM
> >>> To: [e-mail]
> >>> Subject: Re: [Int-area] [EXTERNAL] Re: New Version Notification for draft-herbert-ipv4-eh-03.txt
> >>>
> >>> EXT email: be mindful of links/attachments.
> >>>
> >>>
> >>>
> >>> On 22-Mar-24 03:53, Robinson, Herbie wrote:
> >>>> I would say that, in theory, that’s not a show stopper, but in practice it is a lot of work to implement – enough to suggest that you
> >>> wouldn’t get enough implementations to make it useable.
> >>>
> >>> I'll say it because nobody else has (recently).
> >>>
> >>> Why should the IETF spend effort on upgrading IPv4 capabilities at this point?
> >>>
> >>>      Brian
> >>>
> >>>>
> >>>> *From:* Int-area <[e-mail]> *On Behalf Of *[e-mail]
> >>>> *Sent:* Thursday, March 21, 2024 10:46 AM
> >>>> *To:* Toerless Eckert <[e-mail]>
> >>>> *Cc:* int-area <[e-mail]>
> >>>> *Subject:* [EXTERNAL] Re: [Int-area] New Version Notification for draft-herbert-ipv4-eh-03.txt
> >>>>
> >>>> *[**EXTERNAL SENDER**: This email originated from outside of Stratus Technologies. Do not click links or open attachments unless you
> >>> recognize the sender and know the content is safe.]***
> >>>>
> >>>> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
> >>> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> >>> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> >>> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> >>> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> >>> -----------------------------------------------------------------------------------------------------------------------------------------------
> >>>>
> >>>> On Mar 20, 2024, at 9:35 PM, Toerless Eckert <[e-mail] <mailto:[e-mail]>> wrote:
> >>>>
> >>>>      On Wed, Mar 20, 2024 at 09:20:24PM -0700, Tom Herbert wrote:
> >>>>
> >>>>              In other words, Destination Option Headers do not have fundamentally distinct
> >>>>              processing requirements on the destination host examining it than any other
> >>>>              possible protocol header (e.g.: UDP, TCP), or at least we could not find such a description
> >>>>              for any such guiding rules or treatment differences in RFC8200.
> >>>>
> >>>>
> >>>>          Yes, that's mostly how all the IP protocols are implemented.
> >>>>          Processing of an encapsulated  protocol isn't completely independent,
> >>>>          for instance the pseudo header for the TCP and UDP checksum is
> >>>>          different for IPv4 and IPv6.
> >>>>
> >>>>
> >>>>      Right. But it seems unrelated to whether or not a header is an extension header,
> >>>>      TCP and UDP not being extension headers for example.
> >>>>
> >>>> I haven’t seen it mentioned yet (apologies if so), but there is a big difference between extension headers and encapsulated protocols.
> >>>>
> >>>> Extension headers - no matter how many - can each refer back to the base header. Same for the first encapsulated protocol.
> >>>>
> >>>> E.g.:
> >>>>
> >>>> IP1 IP2 IP3 TCP….TCP uses a pseudo header based on IP3
> >>>>
> >>>> But:
> >>>>
> >>>> IPv6a EHb EHc TCP…TCP uses a pseudo header based on IPv6a; each of the EH’s can also refer back to IPv6a
> >>>>
> >>>> I see NO way to do this with any mechanism for IPv4 except options (whose space is limited). There’s no way to redefine protocol
> >>> processing to ensure that information can be “Carried” forward across EHs.
> >>>>
> >>>> This seems like a show-stopper; has it been addressed?
> >>>>
> >>>> Joe
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> Int-area mailing list
> >>>> [e-mail]
> >>>> https://www.ietf.org/mailman/listinfo/int-area
> >>> _______________________________________________
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