IPv6 RA vs DHCPv6 - The chosen one?

Wed Dec 28 15:50:20 UTC 2011

On Wed, Dec 28, 2011 at 7:28 AM, TJ <trejrco at gmail.com> wrote:
> 2011/12/28 Masataka Ohta <mohta at necom830.hpcl.titech.ac.jp>
>
>> Valdis.Kletnieks at 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