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Harald Welte laforge at osmocom.orgHi David,
On Tue, Apr 07, 2020 at 03:23:17PM -0400, david at ispsupplies.com wrote:
> The reason this is something people want is that the UE in bridge mode can
> offer a public IP to a router behind the UE.
Normally I would have assumed that the router has a LTE modem/interface
built-in, and hence the IP address of the PDP/PDN connection is local to
the router.
If you want to implement a UE that doesn't terminate the IP of the PDP/PDN connection,
I would argue that this is a feature that can be implemented entirely on the UE
side, without any need from the network side.
Fundamentally, the point is that a 3GPP cellular network (before 5G)
provides a point-to-point IP interface. There are no Ethernet frames, no
MAC addresses, no broadcast domain, netmask, default gateway, etc.
A point-to-point interface only has a local and a remote IP address.
Think of the good old days of SLIP/PPP over dialup modems.
Sure, you can invent all kinds of hacks like running a local DHCP server
on the UE that hands out a single lease (which is the address allocated
by the P-GW/GGSN), but they are probably even more ugly hacks than to
implement stateless bi-directional 1:1 address translation in the UE.
In any case, I still don't see what the EPC could or should do in any of
this.
Regards,
Harald
--
- Harald Welte <laforge at osmocom.org> http://laforge.gnumonks.org/
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