Setting up client-server communication over ns-3 emulated LTE network on single host

[Daniel Persson Proos]

I have been trying set up client-server communication over an emulated LTE-connection on a single linux host using the LENA module for a while and I have gotten stuck on the networking part. I am quite new to ns-3 and networking below transport layer in general so I have gotten a bit lost trying to figure this out. I want to use the emulated network to test the characteristics of different application layer protocols in different networking scenarios and therefore I want the client and server application to be able to connect to each other the same way they would when using real networks. Some of the protocols use TCP and some use UDP and I want to be able to use the network emulation in the same way for both. Therefore the ideal scenario for me would be for the simulation to only work on the network layer and below, so that TCP connections would be able to be established directly between the client and server, with any eventual forwarding not occurring above the networking layer. Is this possible or do I need to do forwarding on the transport layer? 

I have made forwarding of UDP packets work between a real client and server through an ns-3 emulation using TapFdNetDevices but as I described above this would not work for the case of TCP connections. Even if I rewrote this module to use TCP the tested scenario would not really be realistic since there would be three separate TCP connections (Client <--> ns-3 client, ns-3 client <--> ns-3-server, ns-3 server <--> Server), each with its own connection setup and congestion control. If forwarding were to be done at the network layer, this could all be avoided, but I cannot figure out how to do that.

I have also looked at the code for ipv4-forwarding-test.cc inside the internet module but that seems to use UDP to forward packets.

Any help I can get would be appreciated!