What are Relay model and Network model?

1. Relay model
a. Relay model is a simple relay of PPP frames between Rm physical layer(RS-232, USB and BT etc.) and Um physical layer(Air Interface);
b. Relay model works as link layer bridging and there is no unframing;
c. The PPP stack is running on tethered device(laptop/smartphone etc.)

2. Network model
a. Network model is an IP layer relay between Rm and Um interfaces;
b. Network model works as network layer bridging and link layer unframing performs on both interfaces;
c. Network model creates separate PPP links over the Rm and Um links. Thus, the PPP stack is running on both the tethered device and modem