IPv6 RA vs DHCPv6 - The chosen one?

Masataka Ohta mohta at necom830.hpcl.titech.ac.jp
Thu Dec 29 01:40:51 UTC 2011

Leo Bicknell wrote:

> Moble networks do not today, and should not in the future expose
> those handoffs to the IP layer.  Even WiFi networks are moving from
> the per-cell (AP) model you describe to a controller based
> infrastructure that seeks to avoid exposing L3 changes to the client.

The reality in Japan today is that each AP used by smart
phones to bypass traffic from 3G to the Internet is
independently provided by small shops or individuals'
households through their own Internet connectivity, there
can be no central controller.

> You do not want to get a new L3 address every 3.6 seconds.  Worse,
> if in the case of VoIP you need a cell handoff to take<  25ms or
> so, which could never happen with new L3 addresseing and then
> renegotating the session to a new L3 address.

As voice traffic is negligible, I think it is carried over
3G only.

But, if you seriously need smooth handover, you must have
2 independent WLAN receivers to simultaneously connect to
two APs operating at different channels for make-before-break
style handover. Or, another possibility is to use only a single
channel of WLAN by all the related APs (Packet Division
Multiple Access (PDMA)).

I have confirmed both approaches work combined with IP mobility
with applications of voice and video over IP.

> Moble networks are designed to provide a L1/L2 fast switching path
> back to a controller infrastructure which then provides the L3
> handoff.  This properly decouples the layers and allows normal LAN
> based timing for the L3 system.

What's happening today is migration from 3G/4G to WLAN.

						Masataka Ohta

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