IPv6 RA vs DHCPv6 - The chosen one?

Masataka Ohta mohta at necom830.hpcl.titech.ac.jp
Wed Dec 28 19:15:50 CST 2011


TJ wrote:

>> 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).

RA initiated DHCPv6 is slower than RA, of course.

Note that RA initiated DHCPv6 is even required to suffer
from DAD delay.

> Also, RAs can be sent in the ms range

Only when you are using mobile IPv6 and there still remains
delay caused by DAD.

> Also:
> Isn't 100m an arbitrarily tight range for a cel tower?

Cell size must shrink as bandwidth requirements of mobile
devices increase.

> And for cellular, isn't the real churn happening more at the Layer2 side
> ... no L3/IPv6/IPv4 interaction?

Because of large amount of traffic caused by smart phones,
mobile providers, at least those in Japan, are trying to
bypass traffic from 3G to WLAN/Internet with IPv4 L3.

> Boot time, or anytime a change in network attachment point is detected ...
> is that not sufficient?

It is wrong to assume intervals between changes 6 seconds.

In general, ND is wrong to specify link specific timings
assuming infrequent changes.

						Masataka Ohta



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