OSI Refference model: Layer one questions!

[warcrow]

When we're reffering to the Physical Layer of the OSI Refference model, I understand that we're reffering to the physical hardware/wiring. But I have some questions for you guys:

1) A Packet of information is an electrical impulse, or several? I'm guessing a packet of information consists of maybe hundreds or thousands of electrical impulses considering a packet has about that same amount of 0 and 1's.

2) If you have any diagrams reffering to this specific event or events, it would be helpful (this does not include the OSI refference model, I already got that).

Thanks in advanced guys! :beer:

 

[CTho9305]

Depends on the specific hardware. Modern ethernet uses Manchester Encoding. A packet is many bytes, a byte is many bits, and on ethernet, each bit is one edge of the manchester encoded signal.

 

[warcrow]

Hrm, maybe I didnt make myself clear.


A packet of information is physically what?

 

[CTho9305]

An electric field on a conductor.

 

[AbsolutDealage]

Well, I guess you could extend it out to a more generalized statement. The packet is a series of impulses (electrical or otherwise) that can be encoded on to a medium, and then decoded on the other end and passed back down the layers.

In terms of ethernet, this is a manchester encoded signal represented as a series of electrical impulses on a wire. The impulses are physically represented as voltage levels (either high or low) on specific lines within the cable. The production of these signals involves placing the correct voltage level that corresponds to the current bit of the encoded signal on to the line. The interpretation of the signal on the recieving end would involve inspecting that wire to determine the voltage level, watching for transitions between the two, and then queueing up the bits so that they can be decoded back into the original packet data.