Re: IPv4 EH proposal

[Tom Herbert <[e-mail]>]

On Fri, Sep 13, 2019 at 12:35 PM Fred Baker <[e-mail]> wrote:
>
> The funny thing, in my mind, is that I agree with both of you.
>
> I guess at least part of the question is "what does it mean to maintain IPv4?" If it means creating something that is not backwards-compatible with existing-and-deployed IPv4, such as an IPv4 Extension Header, then we're not "fixing" IPv4, we are creating yet another new protocol which we will then somehow need to put to death. If, on the other hand, it can be put into an option that a node can skip if it doesn't understand it, I don't think that is going to hurt IPv6 deployment any more than bone-headed "there is just no **** way I'm going to deploy IPv6" does. The latter is what I see in a lot of enterprise deployments.
>
Fred,

That's well said.

The problem I see is that the answer to just move to IPv6 seems to
assumed an idealized reality that doesn't exist. If we can't improve
IPv4 then people will find other ways to achieve the necessary
functionality (similar to how NAT was created?). A specific example
relating to extension headers is the proposal to hack up GRE to
effectively implement extension headers in an EtherType
(draft-weis-ippm-ioam-eth-02). I'm pretty sure everyone will agree
that this is a stunning hack and a complete abuse of EtherTypes, but
nevertheless it does seem to be plausible as solution for IOAM in
IPv4. I find it hard to believe that accepting a hack like this is a
good tradeoff for upholding the letter of the law.

I will be posting an update to the IPv4 EH draft shortly (to int-area
list). This will significantly narrow the immediate use cases and is
much less ambitious (this will only enable HBH and DO in IPv4). The
concept of using SR EH in IPv4 will be out of scope for that draft,
but presumably many of the principles could apply.

Tom

> > On Sep 9, 2019, at 9:35 PM, Stewart Bryant <[e-mail]> wrote:
> >
> > Without commenting on the specific technical proposal.
> >
> > IPv4 is still critical infrastructure in many organizations.
> >
> > We have to maintain it until its natural death. If we neglect the maintenance, or worse try to euthanise it, it will end up either explicitly or implicitly being maintained by another organization.
> >
> > We would thus be wise to actively maintain IPv4 for as long as users need us to, rather than to risk loosing control of it and its future developments.
> >
> > - Stewart
> >
> >
> > On 07/09/2019 16:01, Lee Howard wrote:
> >> IPv4 is dying. Let it go gracefully.
> >> I'm completely opposed to any extensions to the IPv4 specification. By the time the feature set is code complpete, QA'd, and ready for general release, 80% of the world will be using IPv6.
> >> Specific to this case, I have a very hard time understanding the business/engineering case where it would be optimal to implement these extensions rather than deploy IPv6, where they already exist.
> >> Lee
> >> On 9/7/19 7:32 AM, Robert Raszuk wrote:
> >>> /* Adjusting the subject to reflect the topic */
> >>>
> >>> Ok ... I looked at the new wave of mails in wrong order :)
> >>>
> >>> I like this proposal:
> >>>
> >>> https://tools.ietf.org/html/draft-herbert-ipv4-eh-01
> >>>
> >>> And have absolutely nothing against progressing it further - it looks on the surface to be more efficient then sr-mpls over IP - but how many bits are we saving needs to be calculated to state if cost of introducing new encoding justifies the additional control plane, protocol and platform efforts
> >>>
> >>> In fact if we would get to the consensus of using SRH with SID & BSID to be of fixed 20 bits it can reuse a lot of mechanism build for sr-mpls in any commercial router.
> >>>
> >>>  It is just a bit amazing that insertion of EHs into IPv4 would be less problematic that in the case of IPv6 :) Maybe due to allowed fragmentation.
> >>>
> >>> As to the host dropping packets due to unknown protocol - let's observe that SR domain would clean such EH before passing packets further.
> >>>
> >>> Many thx,
> >>> R.
> >>>
> >>>
> >>>
> >>> On Sat, Sep 7, 2019 at 1:14 PM Mark Smith <[e-mail]<mailto:[e-mail]>> wrote:
> >>>
> >>>    On Sat, 7 Sep 2019 at 19:56, Robert Raszuk <[e-mail]
> >>>    <mailto:[e-mail]>> wrote:
> >>>    >
> >>>    > > It's tempting to write up SR over IPv4
> >>>    >
> >>>    > You don't have to write anything ... it is already written and
> >>>    looks like moving fwd :)
> >>>    >
> >>>    > https://tools.ietf.org/html/draft-ietf-mpls-sr-over-ip-07
> >>>    >
> >>>
> >>>    That's tunnelling MPLS over SR over IPv4. I'm talking about native SR
> >>>    over IPv4 e.g. "SRv4".
> >>>
> >>>
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