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

["Moses, Danny" <[e-mail]>]

Well, although the network allocates prefixes it could keep track of addresses that were constructed from those prefixes and initiate NUD on these addresses…

Personally, I don’t believe in designs that rely on MNs to volunteer to provide such information. The better approach is to have a finite lease time for prefixes (like DHCP does) and force the MN to request lease extensions – if they required.

Could that be a reasonable approach?

Danny

From: Peter McCann [mailto:[e-mail]]
Sent: Monday, December 05, 2016 21:02
To: Moses, Danny <[e-mail]>; Lorenzo Colitti <[e-mail]>
Cc: [e-mail]; [e-mail]
Subject: RE: [DMM] WGLC for draft-ietf-dmm-ondemand-mobility-08

In the prefixcost draft, we handwaved a solution that would keep soft state in the network and have the network initiate NUD when it hadn’t seen a given address being used by the MN for a while.  However, NUD only works on individual addresses not whole prefixes.  It might be good to have an explicit message from a MN that says “I am done using this prefix” but this problem is bigger than DMM.  I am not sure what is the right solution.

-Pete


From: Moses, Danny [mailto:[e-mail]]
Sent: Monday, December 05, 2016 1:01 PM
To: Peter McCann <[e-mail]<mailto:[e-mail]>>; Lorenzo Colitti <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: RE: [DMM] WGLC for draft-ietf-dmm-ondemand-mobility-08

That is correct.

Do we need a draft about freeing addresses/prefixes?

Regards,
Danny

From: dmm [mailto:[e-mail]] On Behalf Of Peter McCann
Sent: Monday, December 05, 2016 17:43
To: Lorenzo Colitti <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: Re: [DMM] WGLC for draft-ietf-dmm-ondemand-mobility-08

That may work for communicating the allocation state of the prefix to the MN, but too frequent advertisements may chew up precious wireless bandwidth.  Also, it doesn’t solve the problem of allowing the network to detect when the MN is done using the prefix.

-Pete


From: Lorenzo Colitti [mailto:[e-mail]]
Sent: Sunday, December 04, 2016 9:21 PM
To: Peter McCann <[e-mail]<mailto:[e-mail]>>
Cc: jouni.nospam <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: Re: [DMM] WGLC for draft-ietf-dmm-ondemand-mobility-08

Agreed; if we want to support this sort of mobility it needs to be possible to tell a MN that its previous prefix is no longer valid.

From a technical perspective this can be done using router advertisements, except for the 2-hour rule in RFC 4862 section 5.3.3. That rule exists to prevent DOS attacks on shared links, so I think it would be reasonable to update RFC 4862 to say that less-than-2-hour valid lifetimes are acceptable if the link provides strong guarantees that there are no other nodes on link that can mount such an attack.

On Fri, Dec 2, 2016 at 12:36 PM, Peter McCann <[e-mail]<mailto:[e-mail]>> wrote:
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]<mailto:[e-mail]>]
Sent: Friday, December 02, 2016 3:32 PM

To: Peter McCann <[e-mail]<mailto:[e-mail]>>
Cc: jouni.nospam <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[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]<mailto:[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]<mailto:[e-mail]>]
Sent: Friday, December 02, 2016 3:09 PM
To: Peter McCann <[e-mail]<mailto:[e-mail]>>
Cc: jouni.nospam <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[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]<mailto:[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]<mailto:[e-mail]>] On Behalf Of Lorenzo Colitti
Sent: Friday, December 02, 2016 12:04 PM
To: jouni.nospam <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[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]<mailto:[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]<mailto:[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]<mailto:[e-mail]>>, <[e-mail]<mailto:[e-mail]>>, <[e-mail]<mailto:[e-mail]>>
Resent-From: <[e-mail]<mailto:[e-mail]>>
Resent-To: [e-mail]<mailto:[e-mail]>, [e-mail]<mailto:[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.


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