Glen Kent wrote:
It says that "The IP layer and optical layer are run like two separate kingdoms," Wellingstein says. "Two separate kings manage the IP and optical networks. There is barely any resource alignment between them.
Can somebody shed more light on what it means to say that the IP and optical layers are run as independent kingdoms
The problem is not optical at all but caused by poor L3 routing protocols and operational attempts to compensate them at L2. That is, with a L3 routing protocol having 1ms of HELO intervals, all the thing to be done at L2 is to watch BER/FER above some threshold.
and why do ISPs need to over-provision?
To act against failures. But, if everything is visible at L3, over-provisioned bandwidth can be used even if there is no failure. Visible at L3 means that parallel point to point links between a pair of routers have distinct pairs of IP addresses and BGP routes should flip only upon failure of all the (or almost all the) links. A remaining, but minor, inefficiency could be mismatch of metric at L1 and L3, that is, ASPATHLEN increases for transit services are not roughly proportional to geographic distances of the transit services. Masataka Ohta