The AppleTalk Transport Protocol reference article from the English Wikipedia on 24-Apr-2004
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AppleTalk Transport Protocol

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The AppleTalk Transport Protocol is the original protocol that Apple Macintosh computers used to communicate with each other. This originally worked at about 115 kbit/s over AppleTalk hardware. Once the AppleTalk protocol was converted to communicate over ethernet it was called EtherTalk. Connecting an original Macintosh computer to an ethernet network requires an EtherTalk to AppleTalk bridge.