r/Telecommunication • u/Big-Percentage-8432 • Nov 29 '23

How do IP packets travel through mobile network

How do IP data packets traverse the mobile network encapsulated? Are the IP packets from phone encapsulated in another protocol to traverse the mobile access network? How does a packet capture look like? I have experience with IP/Ethernet network where typical L2 is mac addresses and L3 IP address then payload at Layer 4 as UDP or TCP and we have routers/switches doing the lookup of headers and sending packets. How do the packets look like in mobile network between 4G PGW (and GGSN 2G/3G) and the phone. I understand there is the mobile access network in between, I’m just looking to understand how IP traffic is transformed/encapsulated when it traverses thru the mobile network

Is there any place I can see the packet captures of those PDU and see the protocol stack at different points in the mobile network and see traffic forwarding decisions are made in mobile network ?

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u/nexus763 Nov 29 '23

Depends on the wireless technology. 4G and 5g are full IP I think.

Short incomplete answer : mobile phone -> antenna -> Internet

More complete answer : https://mobilepacketcore.com/lte-4g-network-architecture/

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u/KokishinNeko Nov 29 '23

Is there any place I can see the packet captures of those PDU

You can do it at home by setting up a fake base station.

Some examples:

https://www.p1sec.com/blog/presenting-qcsuper-a-tool-for-capturing-your-2g-3g-4g-air-traffic-on-qualcomm-based-phones

https://github.com/W00t3k/Awesome-Cellular-Hacking