Re: “DHCPv6, SLAAC, Static Day X - 17 year interoperability issue” 2nd issue

[Ca By <[e-mail]>]

On Mon, Nov 9, 2020 at 6:45 PM Mark Andrews <[e-mail]> wrote:

>
>
> > On 10 Nov 2020, at 12:53, Ca By <[e-mail]> wrote:
> >
> >
> >
> > On Mon, Nov 9, 2020 at 4:36 PM Gyan Mishra <[e-mail]>
> wrote:
> >
> > This may have gotten lost in all the threads so starting a new thread.
> The issue is interoperability related issue between the 3 IPv6 addressing
> options that had been broken for 17 years.
> >
> > Problem Statement:
> >
> > The main point I am trying to make is that static address configuration
> and DHCPV6 stateful RFC 8415, you can have any prefix length prefix.
>  SLAAC with A flag set requires a  64 bit IID and that stems from RFC 4291
> modified EUI64 mac based IID generation.  However, now with random IID
> generation schemes with RFC 4941 privacy extension and RFC 7217 stable IID
> you can generate any length IID.
> >
> > The operational issue with SLAAC not supporting any prefix length in PIO
> and requirement for the 64 bit boundary is that in a deployment scenario
> where you would like to deploy longer prefix length subnets with a mix of
> server hosts with static address and mix of client hosts with managed
> address M=1 that get their 128 bit address from the DHCPv6 server pool, the
> fear has always been that if a device came up on the subnet that only
> supports SLAAC it would not work due to the SLAAC A flag set and 64 bit IID
> requirement.  In that case the SLAAC host would not be able to communicate
> with any of the devices with a longer prefix including the router.
> >
> > So that fear of interoperability of SLAAC hosts not being able to
> support longer prefix lengths has prevented operators from being able to
> deploy subnets with longer prefix lengths, as it’s hard to predict that all
> hosts will be able to support static or stateful and so you may end up in a
> situation where a device type may only support SLAAC so then you are in
> trouble deploying longer prefix lengths.
> >
> > Due to the SLAAC 64 bit IID restrictions it has prevented operators from
> deploying “host” subnets with >64 bit prefix lengths.
> >
> > f you go to the “root” of the problem the root is the original IPv6
> specification RFC 1884 dated 1995, RFC 2373 dated 1998, RFC 3513 dated 2003
> and now the present RFC 4291 dated 2006.  As soon EUI64 mac based IID
> become not recommendedR and obsolete the standard should have immediately
> updated RFC 4291 as the dependency on fixed IID is no longer as now random
> IID generation schema starting with RFC 4941 privacy extension dated 2007
> soon became standard for all OS vendors and later RFC 7217 stable IID
> became an alternative option to provide a “random” IID.
> >
> > Once random IID became mainstream in all Host Operating Systems it was
> at that moment that the standard should have changed to update RFC 4291 to
> permanently remove in all RFCs any mention of 64 bit boundary.
> >
> > So this change if I do the math is now 13 years past due.  Even if you
> gave a few years for host operating systems to adopt the new standard which
> I believe back then was fairly quickly the standard should have changed
> eliminating the 64 bit boundary.
> >
> > Think of all the problems “Day 17 years” this has caused and even now
> all of these threads.
> >
> > This is clearly an IETF standards issue and needs to be fixed.
> >
> > We can’t pass the blame to operators to dole out shorter prefixes or
> support PD.  The IETF really needs to take onus end fix the broken standard.
> >
> > Not going to happen for PDP as their are technical issue related to the
> Mobile Network Gateway to support PD.   I will try to dig up the exact
> reason but the network element is very different then a BNG broadband
> gateway which supports most all L3 features.
> >
> > As far as 3GPP operators they are following the well documented RIPE-690
> which only requires allocation of /64.  The main reason mobile operators
> are not making shorter prefix a standard is that is overkill from their
> perspective as you may have many mobile
> >
> > No
> >
> > handsets in a household and there  is no reason for everyone at a single
> location to have shorter prefixes per PDP.  When you are at honme you use
> your wired broadband and when are away from home on the road on 3GPP on PDP
> is when the segmentation comes into play to subdivide the /64 prefix to
> downstream devices but in a household is only needed to be provided by one
> of the devices.
> > Bottom line is from a 3GPP provider standpoint it does not make sense to
> provide a shorter prefix and I don’t think that will ever change even with
> 5G PDP.
> >
> > I am 3gpp network operator.  None of the above thinking has entered my
> head.
> >
> > I have never read any ripe docs, so you cant say i am beholden to them.
> >
> > 3gpp operators only provide /64 because that is all that the standards
> allow for without dhcpv6. No other reason, please avoid creating narratives
> to explain what is clearly documented in the standards.
> >
> > https://tools.ietf.org/html/rfc6459#section-5.3
>
> What’s not explained is why operators haven’t deployed DHCPv6 servers.
> One is already allocating /64 per customer just increase the prefix to a
> /48 and use the first /64 for the downstream link.  A stub DHCPv6 server
> can look for the Prefix Delegation and Prefix Exclude Option in the request
> and if present return a delegation to the already allocated /48 carving out
> the downstream /64.  You don’t need much more.
>
> Are people really incapable of working out minimal implementations?  Or
> are they just not bothering to ask their vendors for them?  Its been 8
> years since RFC 6459 was published.
>


I feel like i have answered this question several time in the last 48
hours. Your answer in a word is: inertia. Set aside your pitch fork. I am
explaining the world as i see it

The force required to break the current stasis is more than i have, if i
must use dhcpv6.  Again, many years of proof.

But i believe that i, and other similar mobile operators can get < 64 size
prefix in customers hands and homes with a tweak of the 3gpp spec to allow
RA < 64 and a UE mechanism to break that prefix into many 64s

> Fixed 5G broadband which is a wired broadband replacement will follow
RIPE-690 guidelines and will allocation much shorter prefixes as with
network slicing and other capabilities with 5G offers the requirements
exist for shorter prefixes.  Not so much for PDP.
> r

>
> >
> >
> > I am rolling out 5G broadband using 64share, so your above is not
> correct, at least for me.  Why? No dhcp servers in network.
> >
> > Maybe you can tell us about how vz is deploying ipv6 here ?
> >
> >
> https://www.google.com/amp/s/www.rcrwireless.com/20200612/5g/verizon-expanding-enhancing-5g-fixed-wireless-service/amp
> >
> >
> >
> >
> >
> https://www.ripe.net/publications/docs/ripe-690#4-2-4--considerations-for-cellular-operators
> >
> > 4.2.4. Considerations for Cellular Operators
> >
> > There is a clear exception to the rule described above when assigning
> prefixes in a cellular network. In this case, a /64 will need to be
> provided for each PDP context for cellular phones, whereas for LTE
> modems/routers, i.e. in the case of broadband by means of cellular access,
> it will still be necessary to choose a /48 or /56 in accordance with the
> aforementioned considerations.
> >
> >
> >
> > RFC 3177 for a default /48 allocation which is obsoleted by 6177 which
> takes a step back and is now not making any recommendations and is putting
> the onus on operators to figure it out and do what they feel is best which
> would definitely not be one size fits all approach.
> >
> > Please read the summary section in RFC 6177 below
> >
> > 5.  Summary
> >
> >
> >    The exact choice of how much address space to assign end sites is an
> >    issue for the operational community.  The recommendation in
> > RFC 3177
> >
> >    [
> > RFC3177
> > ] to assign /48s as a default is not a requirement of the
> >    IPv6 architecture; anything of length /64 or shorter works from a
> >    standards perspective.  However, there are important operational
> >    considerations as well, some of which are important if users are to
> >    share in the key benefit of IPv6: expanding the usable address space
> >    of the Internet.  The IETF recommends that any policy on IPv6 address
> >    assignment policy to end sites take into consideration the following:
> >
> >
> > Thanks
> >
> > Gyan
> >
> >
> > Sent from my iPhone
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> --
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: [phone]              INTERNET: [e-mail]
>
>