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L3 consequences of WLAN offload in cellular networks (was - endless DHCPv6 thread)
From: Alexander Harrowell <a.harrowell () gmail com>
Date: Fri, 30 Dec 2011 14:15:15 +0000
In the DHCP v6 thread, there was some discussion of
mobility and its IP layer consequences. As various people
pointed out, cellular networks basically handle this in the
RAN (Radio Access Network) and therefore at layer 2,
transparently (well, as much as things ever are) for IP
purposes. It therefore shouldn't be a problem.
However, as one contributor pointed out, more and more
cellular operators are migrating traffic onto WLAN for
various reasons, notably:
1) Spectrum - it's unlicensed, i.e. free
2) Capex - the equipment is cheaper
3) Capacity - it's a cheap way of providing high speed
4) Signalling load - it gets rid of the signalling traffic
associated with detaching and attaching devices from the
core network. This is especially important in view of some
Of course much of the signalling is associated with the
Mobility Management features, and getting rid of it by
punting everything to WLAN implies that you lose the
benefits of this.
That suggests that if you're going to do this on a big
scale you need to implement Mobile IP or else keep
backhauling traffic from the WLAN access points to the
cellular core network (GAN/Iu interface), which has obvious
effects on the economics of the whole idea.
Alternatively, you can work on the assumption that the WLAN
is solely for nomadic use rather than true mobility, but a
lot of devices will prefer the WLAN whenever possible.
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who send e-mail to lists complaining about them
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- L3 consequences of WLAN offload in cellular networks (was - endless DHCPv6 thread) Alexander Harrowell (Dec 30)