Re: IP and Optical domains?

[Masataka Ohta <mohta () necom830 hpcl titech ac jp>]

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