Re: [v6ops] [dhcwg] Fwd: New Version Notification for draft-link-dhc-v6only-01.txt

["Bernie Volz (volz)" <[e-mail]>]

Med:

If this option is in play, no address is "assigned" to the client as that requires the DHCPREQUEST/DHCPACK messages and the client "stops" after a DHCPOFFER if the option was returned. So, you can't use this if you want to assign an address.

I'm not sure what is being done today:
1) Are you saying there is no support for this in DHCP. If so, then this is not something that can be used to activate this support.
2) Are you saying that it works fine as is today (since the DHCP server can be configured (somehow) to return this). If so, then don't use the option (at least on the server for the pools).

I think your request is different than this ipv6-only option. So, if you feel that something is needed, feel free to write a draft (likely it would require a new option that the server is told to do this special behavior).

- Bernie

-----Original Message-----
From: [e-mail] <[e-mail]> 
Sent: Wednesday, December 11, 2019 7:49 AM
To: Bernie Volz (volz) <[e-mail]>
Cc: Jen Linkova <[e-mail]>; [e-mail]; V6 Ops List <[e-mail]>
Subject: RE: [dhcwg] Fwd: New Version Notification for draft-link-dhc-v6only-01.txt

Re-,

Please see inline. 

Cheers,
Med

> -----Message d'origine-----
> De : Bernie Volz (volz) [mailto:[e-mail]] Envoyé : mercredi 11 
> décembre 2019 12:20 À : BOUCADAIR Mohamed TGI/OLN Cc : Jen Linkova; 
> [e-mail]; V6 Ops List Objet : Re: [dhcwg] Fwd: New Version 
> Notification for draft-link-dhc- v6only-01.txt
> 
> Not sure how this is supposed to work today (is this documented somewhere)?
> Is dhcp server already assigning addresses in the special range?

[Med] DHCP servers are not used today to assign these addresses. The selection of the address is local to the host. There is no ambiguity for some IPv4aaS techniques (DS-Lite uses 192.0.0.2) but not for CLAT (192.0.0.0/29).

 If so, why
> not continue that practice and don’t honor the ipv6-only option on server.

[Med] That wouldn't work because my proposal is for the server to return the ** same ** address to all requesting hosts with ipv6-only enabled. That address will be passed to modules such as CLAT. This behavior is already required by this draft: 

   As an optional optimization an IPv6-mostly pool MAY be configured
   with a dedicated IPv4 address to be returned to IPv6-only capable
   clients.  In that case the server SHOULD specify that address as the
   client's network address and MUST NOT verify its uniqueness.
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The value I see in returning an address from this well-known range is that the host does not even need to pause, i.e., this text won't be required anymore in the draft: 

==
If the
   IPv6-only Preferred option returned by the server contains non-zero
   value the client SHOULD set the V6ONLY_WAIT timer to that value.  If
   the server returns zero value the client MUST use its own
   configuration for V6ONLY_WAIT timer.  The client SHOULD stop the DHCP
   configuration process for at least V6ONLY_WAIT seconds or until a
   network attachment event happens.  The host MAY disable IPv4 stack
   completely for V6ONLY_WAIT seconds or until the network disconnection
   event happens.
==

The host won't emit IPv4 packets "on the wire" when assigned with such address.

> 
> - Bernie
> 
> > On Dec 11, 2019, at 1:28 AM, "[e-mail]"
> <[e-mail]> wrote:
> >
> > Hi Bernie,
> >
> > Please see inline.
> >
> > Cheers,
> > Med
> >
> >> -----Message d'origine-----
> >> De : Bernie Volz (volz) [mailto:[e-mail]] Envoyé : mardi 10 
> >> décembre 2019 17:11 À : BOUCADAIR Mohamed TGI/OLN; Jen Linkova; 
> >> [e-mail] Cc : V6 Ops List Objet : RE: [dhcwg] Fwd: New 
> >> Version Notification for draft-link-dhc- v6only-01.txt
> >>
> >> Hi:
> >>
> >> Is (8):
> >>
> >>    (8) Consider returning an address from the range defined in 
> >> RFC7335 for IPv6-only hosts. Such IPv4 addresses are required 
> >> anyway for some
> IPv6-
> >> only hosts (those with a CLAT for example).
> >>
> >>    ====
> >>       The result is that 192.0.0.0/29 may be used in any system
> >>       that requires IPv4 addresses for backward compatibility with IPv4
> >>       communications in an IPv6-only network but does not emit IPv4 
> >> packets
> >>       "on the wire".
> >>    ====
> >>
> >> But RFC7335 says (in section 4):
> >>
> >>   IANA has defined a well-known range, 192.0.0.0/29, in [RFC6333],
> >>   which is dedicated for DS-Lite.  As defined in [RFC6333], this subnet
> >>   is only present between the B4 and the Address Family Transition
> >>   Router (AFTR) and never emits packets from this prefix "on the wire".
> >> <---
> >>   464XLAT has the same need for a non-routed IPv4 prefix, and this same
> >>   need may be common for other similar solutions.  It is most prudent
> >>   and effective to generalize 192.0.0.0/29 for the use of supporting
> >>   IPv4 interfaces in IPv6 transition technologies rather than reserving
> >>   a prefix for every possible solution.
> >>
> >> So, this address is only used "on the host" (not on the wire), so 
> >> why
> would
> >> there be any need for the DHCP server to assign this address?
> >
> > [Med] This is to ease remote troubleshooting of the IPv4aaS 
> > component
> (CLAT, B4) of the IPv6-only host. Controlling the IPv4 address 
> configured locally allows to make use of tools such as PROBE
> (https://tools.ietf.org/html/rfc8335) to remotely assess the status of 
> the IPv4aaS component via an IPv6 network.
> >
> >>
> >> And as the IPv6-only option means that the host never completes the 
> >> DHCPDISCOVER/OFFER/REQUEST/ACK (stops at OFFER), this work could 
> >> not be used to assign any address.
> >>
> >> - Bernie
> >>
> >> -----Original Message-----
> >> From: dhcwg <[e-mail]> On Behalf Of 
> >> [e-mail]
> >> Sent: Tuesday, December 10, 2019 5:32 AM
> >> To: Jen Linkova <[e-mail]>; [e-mail]
> >> Cc: V6 Ops List <[e-mail]>
> >> Subject: Re: [dhcwg] Fwd: New Version Notification for 
> >> draft-link-dhc- v6only-01.txt
> >>
> >> Hi Jen,
> >>
> >> Thank you for sharing this updated version. Below some points that 
> >> I do think need more clarification in the I-D:
> >>
> >> (1) The document is too NAT64 centric. The proposal may apply as 
> >> well
> for
> >> other IPv6-only deployment scenarios (typically, unmanaged 
> >> IPv6-only
> CPEs
> >> with IPv4aaS).
> >>
> >> (2) A discussion on the benefit of this extra signal compared to 
> >> relying
> on
> >> existing signals (pref64, aftr_name, map_container...). For 
> >> example, a
> host
> >> that supports the option is ready to wait at minimum 300s and 
> >> disable
> its
> >> IPv4 configuration regardless of what is happening on the IPv6 leg. 
> >> How
> is
> >> that superior to a host delaying DHCP process by xxx ms should be
> explained
> >> further.
> >>
> >> (3) How "IPv6-only preferred" mode is supposed to be set at the 
> >> host
> side:
> >>
> >> ==
> >>   A DHCP client SHOULD allow a device administrator to configure
> >>   IPv6-only preferred mode either for a specific interface (to indicate
> >>   that the device is IPv6-only capable if connected to a NAT64 network
> >>   via that interface) or for all interfaces.
> >> ==
> >>
> >> * I guess the default value when the option is supported by a host 
> >> is to disable including it in the request. The document should 
> >> include a discussion on the default behavior.
> >> * If an explicit action is needed from the user to enable including 
> >> the option, having a discussion to what extent the feature is 
> >> likely to be enabled would be needed.
> >>
> >> (4) The document is still mixing the DHCP client vs. host 
> >> behaviors. For example,
> >>
> >>   Clients not capable of operating in an IPv6-only NAT64 environment
> >>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >>   MUST NOT include the IPv6-only Preferred option in the Parameter
> >>   Request List of any DHCP packets and MUST ignore that option in
> >>   packets received from DHCP servers.
> >>
> >> does not make sense for a DHCP client.
> >>
> >> Also, how the host is able to assess/determine that it is (not) 
> >> capable
> to
> >> behave in the IPv6 mode?
> >>
> >> (5) The definition of IPv4aaS is not aligned with other RFCs: e.g.,
> RFC8585
> >> says the following:
> >>
> >>   "IPv4aaS" stands for "IPv4-as-a-Service", meaning transition
> >>   technologies for delivering IPv4 in IPv6-only connectivity.
> >>
> >> While yours is:
> >>
> >>   IPv4-as-a-Service: a deployment scenario when end hosts are expected
> >>   to operate in IPv6-only mode by default and IPv4 addresses can be
> >>   assigned to some hosts if those hosts explicitly opt-in to receiving
> >>   IPv4 addresses.
> >>
> >> (6) Do you consider a host with CLAT function as an IPv6-only host?
> >>
> >> If so, the following definition should be updated to refer to "IPv4 
> >> connectivity" rather than "IPv4" in general. This is because an 
> >> IPv4 address is required for CLAT for example.
> >>
> >> ==
> >>   IPv6-only capable host: a host which does not require IPv4 and can
> >>   operate on IPv6-only networks.
> >> ==
> >>
> >> (7) Wouldn't the following add an extra delay for applications 
> >> requiring CLAT?
> >>
> >> ==
> >> The host MAY disable IPv4 stack
> >>   completely for V6ONLY_WAIT seconds or until the network disconnection
> >>   event happens.
> >> ==
> >>
> >> (8) Consider returning an address from the range defined in RFC7335 
> >> for IPv6-only hosts. Such IPv4 addresses are required anyway for 
> >> some IPv6-
> only
> >> hosts (those with a CLAT for example).
> >>
> >> ====
> >>   The result is that 192.0.0.0/29 may be used in any system
> >>   that requires IPv4 addresses for backward compatibility with IPv4
> >>   communications in an IPv6-only network but does not emit IPv4 packets
> >>   "on the wire".
> >> ====
> >>
> >> Cheers,
> >> Med
> >>
> >>> -----Message d'origine-----
> >>> De : dhcwg [mailto:[e-mail]] De la part de Jen 
> >>> Linkova Envoyé : mardi 10 décembre 2019 01:02 À : [e-mail] 
> >>> Cc : V6 Ops List Objet : [dhcwg] Fwd: New Version Notification for
> >>> draft-link-dhc-v6only- 01.txt
> >>>
> >>> Hello,
> >>>
> >>> Thanks to everyone for very productive centi-thread on
> >>> draft-link-dhc-v6only-00 ;)
> >>> Here is the improved version, -01.
> >>>
> >>> The main changes:
> >>>
> >>> - The option is not zero length anymore. It has 4-bytes value 
> >>> which might contain V6ONLY_WAIT timer. Benefits:
> >>>    --- allows the network administrators to pilot the changes and 
> >>> rollback quickly if needed;
> >>>    --- addressed some concern about an option having zero length 
> >>> (allegedly it might confuse some clients)
> >>>
> >>> - Using a dedicated address to return to clients is now an 
> >>> optional optimisation. By default the server is expected just to 
> >>> return a random address (as usual).
> >>>
> >>> - Typos fixed (probably some new typos added though).
> >>>
> >>> The authors would like the DHC WG to consider adopting this document.
> >>>
> >>> Thank you!
> >>>
> >>> ---------- Forwarded message ---------
> >>> From: <[e-mail]>
> >>> Date: Tue, Dec 10, 2019 at 10:44 AM
> >>> Subject: New Version Notification for draft-link-dhc-v6only-01.txt
> >>> To: Tomek Mrugalski <[e-mail]>, Lorenzo Colitti 
> >>> <[e-mail]>, Jen Linkova <[e-mail]>, Michael C.
> >>> Richardson <[e-mail]>
> >>>
> >>>
> >>>
> >>> A new version of I-D, draft-link-dhc-v6only-01.txt has been 
> >>> successfully submitted by Jen Linkova and posted to the IETF 
> >>> repository.
> >>>
> >>> Name:           draft-link-dhc-v6only
> >>> Revision:       01
> >>> Title:          IPv6-Only-Preferred Option for DHCP
> >>> Document date:  2019-12-09
> >>> Group:          Individual Submission
> >>> Pages:          10
> >>> URL:
> >>> https://www.ietf.org/internet-drafts/draft-link-dhc-v6only-01.txt
> >>> Status:         https://datatracker.ietf.org/doc/draft-link-dhc-v6only/
> >>> Htmlized:       https://tools.ietf.org/html/draft-link-dhc-v6only-01
> >>> Htmlized:       https://datatracker.ietf.org/doc/html/draft-link-dhc-
> >> v6only
> >>> Diff:           https://www.ietf.org/rfcdiff?url2=draft-link-dhc-
> v6only-
> >> 01
> >>>
> >>> Abstract:
> >>>   This document specifies a DHCP option to indicate that a host
> >>>   supports an IPv6-only mode and willing to forgo obtaining an IPv4
> >>>   address if the network provides IPv6 connectivity.
> >>>
> >>>
> >>>
> >>>
> >>> Please note that it may take a couple of minutes from the time of 
> >>> submission until the htmlized version and diff are available at 
> >>> tools.ietf.org.
> >>>
> >>> The IETF Secretariat
> >>>
> >>>
> >>> --
> >>> SY, Jen Linkova aka Furry
> >>>
> >>> _______________________________________________
> >>> dhcwg mailing list
> >>> [e-mail]
> >>> https://www.ietf.org/mailman/listinfo/dhcwg
> >>
> >> _______________________________________________
> >> dhcwg mailing list
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