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Data transfer rate of Ethenet interface

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kil

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i All,

I would like to know whats the data transfer rate between the Ethernet Switch (whcih has MAC and Phy) and the Processor (Which has one Mac).
Where there is MAC to MAC connection between the processor and the Ethernet S/W which supports 5 MACs AND 5 PHYs.

Processor MAC (10/100T)Ethernet is connected to the MAC of the Ethernet S/W in Rev MII mode where the TX and RX clock is at 25MHz. if all the 5 ports are transferring the data say a movie file at what rate the data is transferred to the processor or how processor will prioritize the data since it has one MAC only.

since four data bits are interfacing with the processor which is having the files accesing the processor at same time how data will be prioritized.

Regards
kil
 

skyfaye

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Since 1 of the 5 links is connected to the processor and the other 4 links is connected to something else, you have a 4:1 oversubscription to the processor link. If all the links run at 100Mbps, then the max rate to the processor link can be 400Mbps. However, the processor link can only handle no more than 100Mbps. So the processor MAC will back pressure the switch by sending pause frames to the switch. The switch will have some built-in buffering to hold the data during the back pressure time. But eventually this buffer will not be enough due to the high oversubscription rate and packets will be dropped and the source will need to retransmit this packet again.

- Hung
 

    kil

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