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Business Data Communications

Business Data Communications. Addressing at the DLL. Data Link Layer Addresses. Must provide a unique identifier for a piece of equipment that is attached to a shared medium. Otherwise, when a frame was put on a shared medium, who could be sure that to whom it was sent?

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Business Data Communications

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  1. Business Data Communications Addressing at the DLL

  2. Data Link Layer Addresses • Must provide a unique identifier for a piece of equipment that is attached to a shared medium. • Otherwise, when a frame was put on a shared medium, who could be sure that to whom it was sent? • Every NIC has a supposedly unique address “burned into” it at the factory.

  3. Data Link Layer Addresses • Expressed in hexadecimal. • An Ethernet address example: 00-0C-00-F5-03-5AHow many bits does this address represent?

  4. Data Link Layer Addresses • To the network, the NICs are the nodes. • One could take a NIC out of one machine and put it in another. To the network, the second machine would have assumed the identify of the first. • What would happen if two NICs sharing a circuit had the same address?

  5. Data Link Layer Addresses • All the nodes sharing a circuit see all the transmissions on the circuit and examine the address in each of them. • However, only the node containing the NIC to whom the transmission was addressed actually passes the information to its upper layers. • What’s the possible security problem here?

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