Ethernet 10/100/1000

Unanswered Question
Jun 10th, 2008


I have a switch requirement for initially providing 100M ethernet with 1G uplink which needs to scale to 1000M access ports with multiple 1G uplinks or 10G.

The 1000M ports however have to be optical while the 100M copper (RJ45) so I guess what I am really looking for is an SFP based switch. It is for a 'metro-ethernet' type service.

A possible solution is the ME4900. The data sheet mentions that the 1000base-T SFP will operate at 10/100/1000 for SGMII client interfaces. I haven't come across this before but after some research I found that the SGMII interface is a 4 pair interface. Differential TX and RX data is on two of the pairs (standard 10/100M) while the other two pairs are used for differential TX and RX clocks.

Would anyone happen to know whether this will work for 100M, 2 pair interface?

To confuse the issue 10/100/1000 copper ports on the Gig Switches - the 1000M option uses 4 pairs - Is this the same as SGMII?

Look forward to hearing from you.



I have this problem too.
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didyap Mon, 06/16/2008 - 09:05

SGMII is a Same like Media Independent Interface (MII), a standard interface used to connect an Ethernet MAC-block to a PHY. It is used for Gigabit Ethernet (contrary to Ethernet 10/100 for MII). It differs from Gigabit Media Independent Interface(GMII) by its low-power and low pin count serial interface). To carry frame data and link rate information between a 10/100/1000 PHY and an Ethernet MAC, SGMII uses a differential pair for data signals and for clocking signals, with both being present in each direction (i.e., transmit and receive), giving 8 signal lines in total. But 10/100/1000 copper ports on the Gig Switches cant work as SGMII.

pbelletty Tue, 06/17/2008 - 07:40

Thanks - that is a very comprehensive answer.

Just one point the data sheet for the ME3400 mentions under the 1000base-T (RJ45) SFP

"10/100/1000BASE-T operation in host systems with SGMII interface". I find this a strange statement as it seems to imply that the 1000base-T SFP ports on the ME3400 can operate at 10/100/1000 provide the host system support SGMII.

Any idea what they mean.

URL for the data sheet is as follows:




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