Hi David,
On Tue, Apr 07, 2020 at 03:23:17PM -0400, david@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