Re: [DMM] WGLC for draft-ietf-dmm-ondemand-mobility-08

[Lorenzo Colitti <[e-mail]>]

Danny,

yes, there are two documents, but draft-ietf-dmm-ondemand-mobility is the
one I am objecting to at the moment.

The reason is that it describes a practice where the application gets an
IPv6 address by issuing a request to the network, and RFC 7934 explicitly
recommends against that. It doesn't matter whether the IPv6 address is
requested and granted via DHCPv6, PCO options, HTTP requests, or smoke
signals - the key point is that per RFC 7934, the network should not be
handing out individual IPv6 addresses based on explicit requests by the
host.

The best example of that practice is this text:

   In case an application
   requests one, the IP stack shall make an attempt to configure one by
   issuing a request to the network.  If the operation fails, the IP
   stack shall fail the associated socket request

but there are likely other examples elsewhere in the draft.

I would suggest rewording that text to say that the MN should pick an IP
address out of a (/64 or shorter) prefix that has the desired properties.
If there is not already a prefix assigned to it that has the desired
properties, then it should request a prefix with the desired properties.

I agree that we do not need application developers to think in terms of
prefixes, but we do need network protocol designers and implementers, and
OS implementers, to design and implement the request machinery using
prefixes and not individual IPv6 addresses.

Cheers,
Lorenzo

On Sun, Dec 4, 2016 at 1:13 AM, Moses, Danny <[e-mail]> wrote:

> Hi guys,
>
>
>
> I hope there isn’t a confusion between *draft-ietf-ondemand-mobility* and
> *draft-moses-dmm-dhcp-ondemand-mobility*.
>
>
>
> ·        Draft-ietf-ondemand-mobility defines the ability of the network
> to provide different types of session continuity services and extends the
> *Socket* interface to enable application to influence the service they
> require for the newly established IP session. It does not specify how the
> session continuity requirements are conveyed to/from the network.
>
>
>
> ·        Draft-moses-dmm-dhcp-ondemand-mobility is the draft that defines
> extensions to *DHCPv6* in order to convey session-continuity service type
> to the network.
>
>
>
> Lorenzo,
>
> I the last F2F in Seoul, you expressed your concerns that the proposed
> DHCP extensions to enabling the specification of the service type in IP
> address requests, contradict the recommendations specified in RFC 7934. As
> I mentioned in the discussion, I am committed to fix the wording in that
> draft to resolve that contradiction.
>
>
>
> But draft-ietf-ondemand-mobility discusses extensions to the Socket
> interface. Sockets are used by application developers to initiated IP
> sessions. I do not think application developers should be networking
> experts and should be aware of what is being allocated by cellular networks
> to mobile hosts (or UEs, in the 3GPP jargon…). This draft does not indicate
> that each invocation of a socket API to initiation an IP session, results
> in a request to the network. It does not get into these resolutions
> intentionally. We are separating the description of what an application
> does, to what the mobile host’s IP stack does.
>
>
>
> Therefore, I do not think we should confuse application writers with IP
> prefixes. All they need to know is how to influence the service that are
> getting, like their ability to choose between a reliable transport (TCP) or
> unreliable one (UDP).
>
>
>
> I hope you agree with this separation.
>
>
>
> Thanks and regards,
>
> Danny
>
>
>
> *From:* Peter McCann [mailto:[e-mail]]
> *Sent:* Friday, December 02, 2016 22:37
> *To:* Lorenzo Colitti <[e-mail]>
> *Cc:* jouni.nospam <[e-mail]>;
> [e-mail]; [e-mail]
> *Subject:* RE: [DMM] WGLC for draft-ietf-dmm-ondemand-mobility-08
>
>
>
> Agree, I am not arguing in favor of sharing a prefix between two or more
> MNs at the same time.  However, I think it is important to reclaim a prefix
> for use by another MN after the current MN has moved to a new attachment
> point and stopped using the prefix it got from the old attachment point.
> It is also important to refrain from advertising the prefix to another MN
> until the current MN has stopped using it.  That is the network state I am
> talking about.
>
>
>
> -Pete
>
>
>
>
>
> *From:* Lorenzo Colitti [mailto:[e-mail] <[e-mail]>]
> *Sent:* Friday, December 02, 2016 3:32 PM
> *To:* Peter McCann <[e-mail]>
> *Cc:* jouni.nospam <[e-mail]>;
> [e-mail]; [e-mail]
> *Subject:* Re: [DMM] WGLC for draft-ietf-dmm-ondemand-mobility-08
>
>
>
> On the particular case of shared links: note that they have substantial
> scalability and performance issues. In order for shared links to work you
> have to engage in DAD proxying, ND snooping, client isolation and all sorts
> of unsavoury and L2/L3 magic that does not scale. Some of these issues are
> described in RFC 7934 section 9.3. On shared links, these forces act to
> reduce the number of IP addresses per host that the network can support and
> leads to the negative consequences in section 4 of the document, which is
> why they are not recommended.
>
>
>
> For these and other reasons, on many public networks we're seeing a shift
> *away* from shared links - see, for example, draft-ietf-v6ops-unique-ipv6-prefix-per-host
> , and the current large deployments of that model in the form of Comcast
> community wifi.
>
>
>
> For many years 3GPP networks have been providing those benefits by
> providing a full /64 to every host. I would hate to lose those benefits.
>
>
>
> On Fri, Dec 2, 2016 at 12:12 PM, Peter McCann <[e-mail]>
> wrote:
>
> With a fixed access network the prefix can be assigned to the link and
> used by anyone who joins the link.
>
>
>
> With a prefix offering mobility the prefix belongs to the mobile host and
> needs to move with it.  There aren’t enough prefixes (even in IPv6) to
> assign a permanent prefix to each UE for every topological attachment point
> that it might visit or start a session from.
>
>
>
> -Pete
>
>
>
>
>
> *From:* Lorenzo Colitti [mailto:[e-mail]]
> *Sent:* Friday, December 02, 2016 3:09 PM
> *To:* Peter McCann <[e-mail]>
> *Cc:* jouni.nospam <[e-mail]>;
> [e-mail]; [e-mail]
>
>
> *Subject:* Re: [DMM] WGLC for draft-ietf-dmm-ondemand-mobility-08
>
>
>
> But you have that problem with IP addresses as well, right? I don't see
> how "assigning a prefix with certain properties" requires more state in the
> network than "assigning an IP address with certain properties".
>
>
>
> On Fri, Dec 2, 2016 at 12:00 PM, Peter McCann <[e-mail]>
> wrote:
>
> Providing any kind of mobility service for a prefix will require some
> state somewhere in the network.  It would be great to avoid an allocation
> request / response for the prefix, but the state has to be created somehow
> before the UE can use the prefix and it has to be reclaimed eventually
> after the UE stops using the prefix (which may not be until well after it
> disconnects from the current link and moves to another one).
>
>
>
> Would welcome any suggestions on how to manage this state.
>
>
>
> -Pete
>
>
>
>
>
> *From:* dmm [mailto:[e-mail]] *On Behalf Of *Lorenzo Colitti
> *Sent:* Friday, December 02, 2016 12:04 PM
> *To:* jouni.nospam <[e-mail]>
> *Cc:* [e-mail]; [e-mail]
> *Subject:* Re: [DMM] WGLC for draft-ietf-dmm-ondemand-mobility-08
>
>
>
> Hi,
>
>
>
> I like the goal of reducing network cost by allowing the use of IP
> addresses that do not require network mobility, but we should not be doing
> this by requesting IP addresses from the network, because this violates
> IPv6 address assignment best practices.
>
>
>
> Specifically, RFC 7934 recommends that a) the network should provide
> multiple addresses from each prefix and b) the network should allow the
> host to use new addresses without requiring explicit requests to the
> network. This is in conflict with at least this text in the draft, which
> says:
>
>
>
>    In case an application
>
>    requests one, the IP stack shall make an attempt to configure one by
>
>    issuing a request to the network.  If the operation fails, the IP
>
>    stack shall fail the associated socket request
>
>
>
> One way to resolve this conflict would be to say that the network must not
> assign individual addresses, but /64 (or shorter) prefixes. So if the
> device desires to use fixed IPv6 addresses, then the network should give
> the host a fixed IPv6 prefix from which the host can form as many addresses
> as it wants.
>
>
>
> I do not think we should advance this document until the conflicts are
> resolved. This document is about IPv6 address assignment to mobile nodes,
> and we should not publish a document about IPv6 address assignment that
> conflicts with best current practices on IPv6 address assignment.
>
>
>
> Regards,
>
> Lorenzo
>
>
>
> On Mon, Nov 28, 2016 at 12:56 PM, jouni.nospam <[e-mail]>
> wrote:
>
> Folks,
>
>
>
> The authors of draft-ietf-dmm-ondemand-mobility-07
> and draft-sijeon-dmm-use-cases-api-source have come up with a merged
> document draft-ietf-dmm-ondemand-mobility-08.
>
>
>
> This email starts a 2 week WGLC for draft-ietf-dmm-ondemand-mobility-08.
>
> The WGLC starts 11/28/16 and ends 12/12/16.
>
>
>
> Provide your comments, concerns and approvals to the email list (and
> hopefully also to IssueTracker).
>
>
>
> - Jouni & Dapeng
>
>
>
>
>
>
>
> Begin forwarded message:
>
>
>
> *From: *IETF Secretariat <[e-mail]>
>
> *Subject: IETF WG state changed for draft-ietf-dmm-ondemand-mobility*
>
> *Date: *November 28, 2016 at 12:51:34 PM PST
>
> *To: *<[e-mail]>, <[e-mail]>,
> <[e-mail]>
>
> *Resent-From: *<[e-mail]>
>
> *Resent-To: *[e-mail], [e-mail]
>
>
>
>
> The IETF WG state of draft-ietf-dmm-ondemand-mobility has been changed to
> "In WG Last Call" from "WG Document" by Jouni Korhonen:
>
> https://datatracker.ietf.org/doc/draft-ietf-dmm-ondemand-mobility/
>
>
> Comment:
> WGLC starts 11/28/16 and ends 12/12/16.
>
>
>
>
> _______________________________________________
> dmm mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/dmm
>
>
>
>
>
>
>
> ---------------------------------------------------------------------
> A member of the Intel Corporation group of companies
>
> This e-mail and any attachments may contain confidential material for
> the sole use of the intended recipient(s). Any review or distribution
> by others is strictly prohibited. If you are not the intended
> recipient, please contact the sender and delete all copies.
>