Frame is aborted and the remaining bytes are not sent

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• Frame is aborted and the remaining bytes are not sent to the FIFO – a) if the destination address of the frame does not match the address in the NIC – b) if there is an error in the frame – This is done by the packet type discriminator
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SUSHMA RAWAL 23 NIC • A network interface card supports a particular protocol for orderly transmission of data – Ethernet • when a NIC is ready to send a message, it checks to see if network is busy • if another NIC is sending a message, it waits; if not, sends it • if 2 devices send messages at the same time, we have a collision • uses CSMA/CD (carrier sense multiple access with collision detection) to deal with collisions both devices stop transmitting and wait a random amount of time before attempting to transmit again.
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SUSHMA RAWAL 24 Ethernet/IEEE 802.3Frame format
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SUSHMA RAWAL 25 Address Recognition • Destination address are of three types: – 1. Individual address (unicast) – 2. Group address (multicast) – 3. Broadcast (all nodes) • The destination address (DA) field of incoming frame is compared with the addresses set in the network interface. – If the addresses do not match, the frame is aborted.
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SUSHMA RAWAL 26 Receiver CRC Check • The incoming data CRC is checked – If an incorrect CRC is detected, the frame is aborted, and the CRC error counter or alignment error counter updated • The lengths of the incoming frames are checked against the specified limits – Minimum: 64 bytes Maximum: 1518 bytes • If the frame length is outside the specified bounds, the frame is typically aborted.
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SUSHMA RAWAL 27 Errors in Receive • Frame Alignment Error • CRC Error • Long Packet when size of packet exceeds max • Runt Packet Received • Invalid symbol Error • These can be found from the Receive Status Register • Rx FIFO Overflow can give an interrupt. • RxOK indicates successful completion of packet reception – RER or Rx Error is because of bad checksum or Frame Alignment Error. RxOK or RER can generate an interrupt.
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Frame is aborted and the remaining bytes are not sent to...

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