L23 - The 64 byte minimum(16 bytes needed for the overhead...

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The 64 byte minimum (16 bytes needed for the overhead) was reasonable for the original 10 mb/second Ethernet. But when the speed was increased to 100 mb/second, the duration of a 64 byte frame was shortened by a factor of 10. To keep the same property the network dimensions would have to shrink by a factor of 10! To keep the same property at 1 Gb/second, the network dimensions would have to shrink by a factor of 100! But 1 Gb/second Ethernet normally doesn’t use CSMA/CD.
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Recall More efficiency with larger frames. F Reducing T by a factor of 10 (100 mb/s Ethernet) increases â by a factor of 10. But it was required that the frame format limits of 46-1500 bytes of data be retained. Increased speed required other changes, such as physical layer signaling methods. At 1 Gb/s, CSMA/CD doesn’t make much sense. But the frame format was retained so higher layers would see the same format whether using 10, 100 or 1000 mb/s Ethernets.
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Gigabit ETHERNET - Standard in 1998 - 802.3z Uses switching and does away with contention. In one of the modes - full duplex - no channel sensing is needed. Main similarity is the same frame format and size limitations. Show Fig. 4-22
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Gigabit ETHERNET (continued) There also is a half-duplex mode where all are connected to a hub instead of a switch. This would require CSMA/CD, but to
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L23 - The 64 byte minimum(16 bytes needed for the overhead...

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