From: Saku Ytti [mailto:saku@ytti.fi]
I got quite a bit of replies from sellers selling me cuSFP, insisting they work.
So I'd like to clear up on this. For 10/100 to work on SFP slot, the PHY in the host needs to be multirate. Exception is SGMII which supposedly supports magic mode where SFP can ask it to send same bit 10 times, then SFP can discard 9/10 bits, to remain very dumb yet deliver 100M client on 1GE host.
RGMII does not support this trick and this trick does not bring you down to 10M. One box that we have right now, which can't do any of this is ME-4924.
There is absolutely no reason that you couldn't deliver 'media converter' or '2 port switch' in a SFP casing, to get that 1 10/100 port in every 4500-X or EX4550 port you need to cater some legacy. If my desire is odd (2 people have expressed off list they want same) this won't be built. But if this is somewhat common demand and missing product, we can certainly get such SFP built.
Obviously this SFP would cost bit more than normal cuSFP, as it needs to do rudimentary buffering, packet dropping and it needs to have frame parser.
Considering that Dell and HP at least are shipping brand new hardware with IPMI/BMC/iLO/whatever management ports that can only speak 100mbit when every other Ethernet interface in the box at least gigabit, having a useful way to talk to that port without having to keep separate switching hardware around would be nice. I'm not holding my breath, but you know, along with a pony, this would be nice. Jamie