Dear friend,

I have one doubt Ethernet is analog transmission or digital transmission

Digital.

Packet ;)

What to really fry your mind... look into how little of every packet is actually data you are sending and how much is overhead. ( yes a trick question)

It's all data of one form or another....

It's all data of one form or another....Correct or it would be simple point-to-point network with no redundancy.

Perhaps how much is Payload is the more correct terminology... vs the overhead (which really IS required for it to all work). The preamble and postamble are a significant part of the size of the average data packet. That Resume document you are sending to the server across your lan will be dwarfed by the rest of the packet requirements.

It looks like the header/footer are only about 26 bytes the payload is at lest 42 bytes and at most 1500.

Unless that's changed in recent years with newer incarnations of the interface... I remember the preamble and postamble of each packet are significantly larger than 26 bytes.

Somewhere in my stuff at home I've got the original specs for the original 802.3 standard if I haven't tossed them out some time in the last 30 years.

I am relying on Wiki, so it is anyone's guess.