Subject: [6gip] Higher bandwidth consequences on mobile users and their IP addressing - the /64 problem

From: Alexandre Petrescu <[email-masked]>
Date: Wed, 24 Feb 2021 11:21:08 +0100

Hi,

While discussing a /64 issue in other context I realized the following.

One of the consequences of higher bandwidth and lower latency
availability to mobile users is on IP addressing.  With 4G, 5G and
presumably 6G the end user has so much bandwidth at hand that one is
more and more tempted to use not one device but more devices in a local
area.

Such devices are the personal wearables and maybe the tablets of friends
around, or, as a person told me recently during the Texas freezing -
maybe the only way to connect to the Internet during an outage of the
in-home broadband network is this 'tethering'.  Other times such devices
are all computers in a car, or all computers in an automated public
transportation shuttle.

It should be mentioned that there is potentially an alternative to this
grouping of devices.  Rather than use a single SIM card in one
smartphone to 'tether' all devices around, as mentioned above, rather
prefer to equip each single device with its own SIM card.  This might
seem cheap to some (some dataplans go as low as 1eur/month per SIM) but
might be unreasonably expensive to others.

If it is preferred to consider the first configuration (one SIM for a
large set of computers), then there might be a problem in IP addressing.
  The problem relates to:
- the IPv6 Addressing Architecture mandates IIDs of length 64
- SLAAC with Interface IDs on Ethernet onlty work at 64
- mobile operator's assignment of /64 prefixes to a single connection
   (i.e. one SIM-authenticated connection gets one /64).
- in some simple configs all devices might be in one subnet but as the
   number of devices grows (more bandwidth implies there would be more
   devices to take advantage of it) there will be more subnets to better
   separate them.

I suspect that a consequence of higher bandwidth availability to mobile
users is that the IP addressing as listed above has some problems that
would need to be solved.

Alex