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Understanding the network.pdf - Back to Home

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Figure 3.4. AARP message formats.<br />

The second role of AARPs is <strong>to</strong> assist in <strong>the</strong> address acquisition<br />

process. When <strong>the</strong> node asks Layer 2 for a <strong>network</strong> address, a random<br />

provisional address is chosen and <strong>the</strong>n checked against entries in <strong>the</strong><br />

AMT. If <strong>the</strong> address is not in its AMT, <strong>the</strong> host AARPs for it. If <strong>the</strong><br />

address is not in use, <strong>the</strong> provisional address is used and <strong>the</strong> address<br />

acquisition process continues.<br />

LocalTalk<br />

LocalTalk is <strong>the</strong> Apple Computer plug-and-play <strong>network</strong> cabling<br />

infrastructure. In its original form, LocalTalk operated over shielded<br />

twisted-pair cable using a bus <strong>to</strong>pology. The pro<strong>to</strong>col was later<br />

implemented over two-pair voice-grade twisted-pair, with a star<br />

<strong>to</strong>pology known as PhoneNet developed by <strong>the</strong> Farallon Corporation.<br />

LocalTalk operates at 230Kbps using Carrier Sense Multiple Access<br />

with Collision Avoidance (CSMA/CA) as an access control method.<br />

With CSMA/CA, <strong>the</strong> <strong>network</strong> must be clear for an interdialog gap (IDG)

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