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 (!)

(C) Herbert Haas 2005/03/11

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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.

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