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.
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.
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?
It depends on applications.
If mobile devices act as clients to 3G servers, what is important
is not IP addresses but 3G IDs, which must be authenticated even
if the mobile devices use WLAN.
On the other hand, if mobile devices act as servers to clients
in the Internet, fixed IP addresses, not necessarily IETF
standard mobile IP, are required.
Application developers with their own IP address spaces may
bundle services for fixed IP addresses with their applications
requiring fixed IP addresses. The applications may use, to
maintain the fixed IP addresses, their own protocols at the
application layer, or IETF standard mobile IP at the IP layer.
