Rate Adaptation?

Unanswered Question
Oct 28th, 2008

I read that rate adaptation means that devices that use different Ethernet speeds can communicate through the switch (hubs can not).... does this mean i.e. that a PC can communicate at 10Mbps with a switch and the switch communicates at 100 with the PC (In a duplex or half-duplex scenario)?

I have this problem too.
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Joseph W. Doherty Tue, 10/28/2008 - 18:24

If you're thinking of different PCs connected to a switch, each on a different port, each can communicate at different speeds and/or duplex settings. (Another advantage of switches has been support for full duplex, hubs only supported half duplex, I believe. Also, 10/full, I also believe, was not truly a standard, so not all [older] switches supported it.)

BTW: I've seen "special" hubs that had an integrated bridge which would allow some hosts to operate at 10/half and others 100/half.

fjcardenas-1 Wed, 10/29/2008 - 06:40

So... If I have PC1 connected to SW1 @10Mbps half... PC1 can communicate with no problems with another computer (PC2) connected to the same SW1 but @100 Mbps Full?


Joseph W. Doherty Wed, 10/29/2008 - 08:17

Usually, yes. Although, when PC2 transmits to PC1, SW1 will accept the frames and normally buffer them since PC1 can only accept at 10 Mbps. Depending on the nature of the protocols being used, and how fast/often PC2 transmits, buffers on SW1 can overflow resulting in dropped frames.


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