[148036] in North American Network Operators' Group
L3 consequences of WLAN offload in cellular networks (was - endless
daemon@ATHENA.MIT.EDU (Alexander Harrowell)
Fri Dec 30 09:17:55 2011
From: Alexander Harrowell <a.harrowell@gmail.com>
To: NANOG list <nanog@nanog.org>
Date: Fri, 30 Dec 2011 14:15:15 +0000
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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In the DHCP v6 thread, there was some discussion of=20
mobility and its IP layer consequences. As various people=20
pointed out, cellular networks basically handle this in the=20
RAN (Radio Access Network) and therefore at layer 2,=20
transparently (well, as much as things ever are) for IP=20
purposes. It therefore shouldn't be a problem.=20
However, as one contributor pointed out, more and more=20
cellular operators are migrating traffic onto WLAN for=20
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=20
associated with detaching and attaching devices from the=20
core network. This is especially important in view of some=20
smartphones' behaviour.
Of course much of the signalling is associated with the=20
Mobility Management features, and getting rid of it by=20
punting everything to WLAN implies that you lose the=20
benefits of this.
That suggests that if you're going to do this on a big=20
scale you need to implement Mobile IP or else keep=20
backhauling traffic from the WLAN access points to the=20
cellular core network (GAN/Iu interface), which has obvious=20
effects on the economics of the whole idea.
Alternatively, you can work on the assumption that the WLAN=20
is solely for nomadic use rather than true mobility, but a=20
lot of devices will prefer the WLAN whenever possible.
Thoughts/experiences?
=2D-=20
The only thing worse than e-mail disclaimers...is people=20
who send e-mail to lists complaining about them
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