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(C) Herbert Haas
2005/03/11
What About Gigabit Hubs?
Would limit network diameter to 20-
25 meters (Gigabit Ethernet)
Solutions
Frame Bursting
Carrier Extension
No GE-Hubs available on the market
today forget it!
No CSMA/CD defined for 10GE (!)
Remember: Hubs simulate a half-duplex coaxial cable inside, hence limiting the
total network diameter. For Gigabit Ethernet this limitation would be about 25
meters, which is rather impracticable for professional usage. Although some
countermeasures had been specified in the standard, such as frame bursting and
carrier extension, no vendor developed an GE hub as for today. Thus: Forget GE
Hubs!
The 10 GE specification does neither consider copper connections nor hubs. 10
GE can only run over fiber.
At this point please remember the initial idea in the mid 1970s: Bus, CSMA/CD,
short distances, no network nodes.
Today: Structured cabling (point-to-point or star), never CSMA/CD, WAN
capabilities, sophisticated switching devices in between.