Do telephone calls work at Layer2?

Question

We know that Wi-Fi works in both layer1 and layer2 and travel through air in layer1.

My question is when we create mobile phone call during connection establishment phase sender Mac address and destination Mac address will be used which is called layer2 Wi-Fi header?

And this process (connection establishment phase)could we tell that is it layer2 circuit switching? Because we know that all layers can have a circuit switching, except real layer 1, which has no switching, just a connection circuit.

Or only layer1 is involved during connection establishment phase?

Answer 1

First of all, as already said, the only thing in common between mobile networks and Wi-Fi is that it is wireless. Besides that, these are completely different technologies with completely different use-cases, different set of challenges, and completely different designs.

Second, Wi-Fi standard defines layer1-2 protocols, where layer2 is interoperable with Ethernet layer2. Mobile network is a network, which defines its own protocol stack, which has all 7 layers, necessary to address unique challenges of being mobile. This protocol stack is far more complicated than any IP network and it takes at least one one-semester course or one book to explain it, so I cannot pack it in one answer. There are some shared issue between Wi-Fi and cellular due to transmission on the wireless channel, but solutions are different.

do telephone calls work at layer 2?

No. Phone networks have all layers up to 7. Phone calls require all layers to work. This is true for all cellular networks and ISDN (normal wired phone network).

We know that Wi-Fi works in both layer1 and layer2 and travel through air in layer1.

Wi-Fi standard specifies layer1 and layer2 protocols...

My question is when we create mobile phone call during connection establishment phase

What connection establishment phase? There is a kinda "connection establishment phase" when your phone connects to the network and kinda "connection establishment phase" when you call someone or someone calls you.

sender Mac address and destination Mac address will be used which is called layer2 Wi-Fi header?

Neither. Mac addresses are properties of IEEE layer2 protocols - Ethernet and Wi-Fi. Cell protocols do not use Mac addresses, at least over wireless parts.

Here there are packet formats of 5G protocol. There is a media access protocol, but there are no Mac addresses.See also this question.

And this process (connection establishment phase) could we tell that is it layer2 circuit switching?

No, being connection-oriented does not imply circuit switching. Wi-Fi is connection-oriented and reliable, but it is not circuit switched. Your Wi-Fi router does not allocate you exclusive resources only because you are connected to it.

Because we know that all layers can have a circuit switching, except real layer 1, which has no switching, just a connection circuit.

Well, although it is theoretically possible, it is very rare to have a mixture of circuit switching and packet switching, i.e., circuit switching on one layer and packet switching on another layer. GPRS is probably an example of such, but it is not used anymore. UMTS has more or less two parallel stacks for phone calls and Internet. And as said by @Ron and @Zac, LTE runs calls over VoIP.

Or only layer1 is involved during connection establishment phase?

Layer1 defines how to tranfer bits over a channel. I guess you can answer your question.

Answer 2

IP phone or VoIP is an application - accordingly located in the application layer (OSI L7) - off-topic here.

If IP is used, you've got the classic network stack L7 - L4 - L3 - L2 - L1, where each layer uses the one beneath for service.

all layers can have a circuit switching, except real layer 1

Circuit switching is (more or less) the opposite of packet switching which is the predominant form of network switching today. Circuit switching establishes a dedicated channel or signal path when a connection is established. Resources for that channel are allocated and reserved for the entire connection. In packet switching, all data is broken down to small packets which are each forwarded by themselves across a stateless network (as least in theory). Packet switching is far superior in terms of efficiency and cost.

Ethernet and Wi-Fi are packet-switching networks. There may be a virtual circuit implemented in the transport layer, but not necessarily so.

Mobile telephony may use different protocol types, depending on generation. 2G (GSM) is mainly a circuit-switching network while 4G (LTE) has largely evolved to packet switching.

Answer 3

Not a GSM or Mobile network expert, but from a Networking perspective, signal transmission is Layer 2. No "connection" can be made without signal traversing the physical medium (Layer 1). That said, any modern infrastructure supporting voice transmissions is likely using at a minimum some type of label switching (e.g. MPLS) which is considered layer 2.5. So to answer your question directly, land line telephone calls on a circuit switched PBX would use exactly Layer 2. Anything else is probably implementing labels or IP to determine path selections.