1. Ethernet Physical Layer

2. PROCESS OF SENDING AND RECEIVING PACKETS Network/OS software executes a routine to send the frame to the network interface controller card (NIC) over the internal bus NIC prepares frame format for transmission and signals the transceiver of the desire to send. Transceiver waits for quiet time and then transmits. If it encounters a collision, it informs the NIC which makes the decision when it is time to alert the OS that something has gone wrong.

3. PROCESS OF SENDING AND RECEIVING PACKETS Receiving transceiver looks at frames for its own address. When it sees one, it sends the frame to the NIC. NIC error checks the frame and if OK notifies the OS of a frame arrival. If OS is able to, it copies the data from the NIC to an OS buffer. (fromShay text)

4. KEYS TO OPERATION Collisions are recognized early before collision kills too much. Retransmissions have no guarantee of success. Practically it works well. Broadcasts address exist. Ever interface has a unique ethernet address built into the board.

5. Works because of time for collisions versus time for transmission propagation delay : frame transmission: example: 4 collisions followed by transmission

6. HARDWARE SPECIFICATIONS 10BASE550 ohm cable, 10mm diam500m10Mbps 10BASE250 ohm cable, 5mm diam185m10Mbps 10BROAD36 75 ohm coax3600m10Mbps 10BASETtwisted pair100m10Mbps 10BASE5twisted pair250m1Mbps

7. Hubs and Switches STANDARD –Physical Star –Logical Bus –Repeat transmission on all links SWITCHED –Not repeated on all links –Effectively segments transmission –Allows for multiple transmission!

8. FRAME FORMAT LENGTH:64-1500 bytes ERROR CONTROL: CRC ADDRESS LEN: 2 or 6 bytes (unique for each interface card)