Re: [homenet] New Version Notification for draft-barth-homenet-wifi-roaming-00.txt

Michael Thomas <mike@mtcc.com> Thu, 26 November 2015 15:29 UTC

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From: Michael Thomas <mike@mtcc.com>
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Date: Thu, 26 Nov 2015 07:28:57 -0800
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Subject: Re: [homenet] New Version Notification for draft-barth-homenet-wifi-roaming-00.txt
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On 11/26/2015 07:15 AM, Mikael Abrahamsson wrote:
> On Thu, 26 Nov 2015, Ray Hunter (v6ops) wrote:
>
>> I have read this draft and find it interesting.
>>
>> The use of host routes would seem appealing to avoid
>> 1) any need for stateful "home agent" and multiple forwarding
>> 2) renumbering of the end nodes when roaming
>> 3) relatively small number of hosts compared to the complexity of the 
>> topology
>>
>> Use of RFC7217 addresses would seem appropriate, but that assumes 
>> that DAD really is reliable at the time a node attaches to the 
>> homenet for the first time.
>
> Wouldn't it be better to adopt 
> https://tools.ietf.org/html/draft-ietf-v6ops-host-addr-availability-02 
> and just give every device its own /64 and move that around?
>
> My worry about the whole L3 approach is how long does it take to 
> re-establish packet flows after the L2 wifi handover between APs 
> compared to an L2 only solution?
>
>> What's the benefit/downside of this approach compared to having 
>> roaming nodes actively take part in the HNCP acting as "multi-homed 
>> routers" with an internal (invariant) /64 VLAN used to bind to 
>> applications?
>
> I'd say this approach adds one more layer that needs to come up before 
> packets can start flowing again, especially since it would require 
> routing protocol participation as well, I'd imagine.
>
> If 802.11 can assure L2 handover in 1 second (I don't know how long 
> the handover time is, just guessing), how much are we willing to add 
> in time because of L3 mechanisms added on top of this, before packet 
> flows are up and running again?
>

Even if it's a 1/2 second, the l2 handover is still far too long for, 
say, real time flows. Isn't this why you want to
do make-before-break if at all possible? at that point, time-to-flow is 
less of an issue, right?

Mike