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Ethernet Lab

Ethernet Lab. Lab #3. Overview. Create Ethernet Header Bitstuff packet Search for frames in the middle of physical layer 90 byte data. Preamble. Dest Address. Src Address. Type. Body. CRC (zero). Postamble. 8 bits. 48 bits. 48 bits. 16 bits. 1-56 bytes. 32 bits. 8 bits.

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Ethernet Lab

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  1. Ethernet Lab Lab #3

  2. Overview • Create Ethernet Header • Bitstuff packet • Search for frames in the middle of physical layer 90 byte data

  3. Preamble Dest Address Src Address Type Body CRC (zero) Postamble 8 bits 48 bits 48 bits 16 bits 1-56 bytes 32 bits 8 bits 01111110 Bit stuffing 01111110 Ethernet Header Type=0, CRC=0

  4. Bit Stuffing State Machine 0 1 0 1 0 1 0 1 0 1 Insert 0

  5. Non-byte Boundaries Dst addr 0xffffffffffff, src addr 0x8000ff002311, type 0,body 0xfc,crc 0 ff,ff,ff,ff,ff,ff,80,00,ff,00,23,11,00,00,fc,00,00,00,00= 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1000 0000 0000 0000 1111 1111 0000 0000 0010 0011 0001 0001 0000 0000 0000 0000 1111 1100 0000 0000 0000 0000 0000 0000 0000 0000 1111 1011 1110 1111 1011 1110 1111 1011 1110 1111 1011 1110 1111 1011 1100 0000 0000 0000 0111 1101 1100 0000 0000 1000 1100 0100 0100 0000 0000 0000 0011 1110 1000 0000 0000 0000 0000 0000 0000 0000 000 fb,ef, be,fb, ef,be, fb,c0, 00,7d, c0,08, c4,40, 00,3e, 80,00, 00,00, 0

  6. Now with sentinels 0111 1110 1111 1011 1110 1111 1011 1110 1111 1011 1110 1111 1011 1110 1111 1011 1100 0000 0000 0000 0111 1101 1100 0000 0000 1000 1100 0100 0100 0000 0000 0000 0011 1110 1000 0000 0000 0000 0000 0000 0000 0000 0000 1111 110 7e,fb,ef, be,fb, ef,be, fb,c0, 00,7d, c0,08, c4,40, 00,3e, 80,00, 00,00, 0f,c0 Original 19 bytes, stuffed with two sentinels 23 bytes

  7. Framing • There can be more than one Ethernet packet in a 90 byte physical layer data segment • If you encounter a bit stuffing error, look for a beginning sentinel for the next packet.

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