Does a packet sent out to 3G network have Ethernet Header?

Question

I'm capturing 3G data on my iOS device using RVI interface on my mac.
Looks like I'm succeed making capture and I can analyse RX/TX traffic.
Currently I'm streaming a UDP stream out to 3G network. So, what I want is to measure traffic and get some statistics on that stream.
What's strange for me is all required headers are presented in the captured packets besides Ethernet header. So I'm curious whether packets sent over 3G interface should have Ethernet header?

P.S. Packets contain "Raw packed data" header which actually tells "No Link information available".

Answer 1

If you mean packets between the handset (the UE in UMTS terms) and the network (Node B), then no is the answer.

The IP protocol is a layer 3 protocol (usually expressed as being 'comparable to layer 3 in the OSI model') and it can be carried by different layer 2 protocols. Probably the most common one is ethernet in regular wired networks, but between a handset and the network in a UMTS network the IP protocol is carried over a layer 2 protocol called PDCP (Packet Data Convergence Protocol).

The following Wiki article on the OSI stack gives some good example of the different protocols at the different layers:

• http://en.wikipedia.org/wiki/OSI_model (see the Examples section and look at IP which is layer 3 and Ethernet and PDCP which are layer 2 and hence can 'carry' the layer 3 protocol)

This link contains a nice diagram showing the protocol stack for the UMTS traffic between your handset and the network, and lots of other good background also (see fig 17 for your 3G scenario):

• http://www.lteandbeyond.com/2012/01/interfaces-and-their-protocol-stacks.html

Note that if your IP traffic exits the 3G carriers network and travels towards a host on the internet (for example) then it will almost certainly be carried over different layer 2 protocols at this stage of its journey and this will probably be Ethernet in many cases.