subrate SFP?

joel jaeggli joelja at bogus.com
Thu Aug 29 20:38:27 UTC 2013


On 8/29/13 6:08 AM, Saku Ytti wrote:
> How do people deal with situation where you need <=48 SFP/SFP+ ports, but
> you occasionally need one or two cu 10/100 ports?
arista 7050s support 100 Mb/s on their copper sfp I have leveraged that,
if you can break out the 40Gb/s ports you have as many as 64 ports of
10Gb/s. there are other switches that I've seen do this but they're not
common.

My problem is mostly around PDU/CDU management, in racks that otherwise
would be 10Gb/s only and in general I've addressed it with dedicated
switches  that support many of these devices rather than just two.
> For some reason it's becoming quite rare for SFP port to natively support
> 10M and 100M rates.
>
> Technically obviously solution to me would be subrate SFP, which presents
> itself as 1GE to host, offering 100M or 10M to client. This would obviously
> break QoS at the host as host would still think it's 1GE and SFP itself
> would need to drop+buffer. But for my applications it would be fine, the
> 10M or 100M ports are typical some MGMT access interfaces.
> I can't imagine such SFP being complex or expensive, considering we have E1
> over IP in a SFP, which includes control-plane and forwarding-plane inside
> SFP form-factor
>
> Is this demand peculiar? Could I source such SFP somewhere by showing there
> is demand?
>
> Putting 2 port switches or fibre converters with external PSU just to
> support few ports seem dirty.




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