In the last BWA conference call, if I recall correctly,
someone stated that for applications like financial transactions, FEC is often
turned off to reduce latency -- even for traffic between New York and Chicago.
Please help me understand that. Light propagation delay in
fiber is ~5 microseconds per kilometer. In contrast, FEC latency would be
sub-microsecond. Even within a data center of 300 meter span, a round-trip
through just one switch can add up to several microseconds. On the other hand,
turning off FEC may increase BER and make TCP retransmissions more likely, thus
adding to latency.
Or is it that in such links, the BER is so low that FEC ends
up being all latency and no benefit?
Thank you.
Regards,
Vipul
Vipul Bhatt
(408) 461-8521
[Re-sent, with apologies for inadvertently including a restrictive notice in the previous message.]