On Dec 30, 2011 9:16 AM, "Alexander Harrowell" <a.harrowell@gmail.com> wrote:

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 smartphones' behaviour.

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.

Thoughts/experiences?

The state of the industry is the support of nomadic mobility from cellular to / from Wi-Fi , there is nearly no support of mobile IP that I have seen. It is going more and more in this direction. At T-Mobile USA we have evolved our wifi calling features from fully mobile UMA / GAN to non-mobile IMS wifi calling. Cb

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On Dec 30, 2011 9:16 AM, "Alexander Harrowell" <a.harrowell@gmail.com> wrote:

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 smartphones' behaviour.

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.

Thoughts/experiences?

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