Ethernet LAN Switch Question

>
> Hello,
>
> I have a hypothetical question with practical implications: Two
> computers, 'A' and 'B', are plugged into a 100baseTX switch. Computer
> 'A' has a 100baseTX interface and computer 'B' has a 10baseT card.
> When 'A' is talking to 'B' through the switch, does it send its frames
> at the slower 10 Mbit/sec rate, or does it send to the switch at the
> full 100 Mbit/sec and the switch shift it out slower to 'B'?

> Andy Ball wrote:
>

>>
>> Hello,
>>
>> I have a hypothetical question with practical implications: Two
>> computers, 'A' and 'B', are plugged into a 100baseTX switch. Computer
>> 'A' has a 100baseTX interface and computer 'B' has a 10baseT card.
>> When 'A' is talking to 'B' through the switch, does it send its frames
>> at the slower 10 Mbit/sec rate, or does it send to the switch at the
>> full 100 Mbit/sec and the switch shift it out slower to 'B'?

>
> "A" will send at the full rate. If the switch doesn't use flow control,
> the
> buffers will eventually fill and frames will be lost. However, the TCP
> protocol also has it's own flow control mechanisms, that cause it to back
> off, when switch congestion causes delays or lost frames. This will
> reduce the amount of data that "A" tries to send through the switch.

> Forgot to mention: look up IEEE 802.3x flow control. This flow control
> mechanism uses a "pause" MAC control frame to tell another device to stop
> sending for a specified period of time. However, flow control is optional,
> so not all switches use it.

JK> Forgot to mention: look up IEEE 802.3x flow control.
> This flow control mechanism uses a "pause" MAC control
> frame to tell another device to stop sending for a
> specified period of time. However, flow control is
> optional, so not all switches use it.