Re: IPv6 RA vs DHCPv6 - The chosen one?

[Cameron Byrne <cb.list6 () gmail com>]

On Wed, Dec 28, 2011 at 7:28 AM, TJ <trejrco () gmail com> wrote:
> 2011/12/28 Masataka Ohta <mohta () necom830 hpcl titech ac jp>
>
> > Valdis.Kletnieks () vt edu wrote:
>
>
> > <SNIP>
> >
> > > > In this case, the following statement in RFC1883:
> > > > >    If the minimum time for rebooting the node is known (often more than
> > > > >    6 seconds),
> > > > is the wrong assumption which made RA annoying.
> > >
> > > Oddly enough, a lot of us are running on networks where assuming this
> > about end
> > > user gear is perfectly reasonable.
> >
> > That is because, as I wrote already in the previous mail,
> >
> > >       Network configuration was mostly stationary
> >
> > For example, IPv6 might work well, if most of your end users
> > are not moving rapidly between small mobile cells.
> >
> > However, assuming you change the cells every 100m in average
> > and you are moving at 100km/h, you must change the cells every
> > 3.6 seconds in average, which means you must be able to change
> > the cells frequently, which means each cell change take a lot
> > less than 3.6 seconds.
>
> To me, that sounds like an argument in favor of SLAAC.  SLAAC is noticeably
> faster in my experience than DHCP (v4 or v6).  Also, RAs can be sent in the
> ms range - for environments that expect that type of attachment-point-churn
> ...
>
> Also:
> Isn't 100m an arbitrarily tight range for a cel tower?
> And for cellular, isn't the real churn happening more at the Layer2 side
> ... no L3/IPv6/IPv4 interaction?

Correct.  Cellular network mobility at the cell site level is all L1
and L2 magic.  GSM / UTMS / LTE will never engage in SLAAC churn as a
result of a normal mobility event.

> > > We haven't seen many consumer-grade
> > > Windows, Macs, or Linux boxes that are able to reboot in much under 6
> > seconds.
> >
> > IPv6 is wrongly architected, not because it assumes nodes are
> > able to reboot in much under 6 seconds, but because it assumes
> > new configurations necessary only at boot time.
>
> Boot time, or anytime a change in network attachment point is detected ...
> is that not sufficient?
>
>
> > Yes, I know you can do it with careful tuning and throwing SSDs and other
> > > hardware at it - doesn't mean it's common.
> >
> > Obviously, the IPv6 committee and you are assuming computers
> > of immobile main frame computers or, at least, immobile
> > workstations.
> >
> > However, in the real world, commonly available mobile phones
> > are IP capable computers which wake up from dormant state
> > within a second and needs handover often within a second.
>
> Again, if we are arguing about simple speed of address attainment - SLAAC
> wins.
>
>
>
> >                                                 Masataka Ohta
>
>
> /TJ