[c-nsp] Downsides of combining P and PE functions into a single box

[Pavel Lunin]

Folks, let me make a tiny semi-philosophical summarization on this :)

Any layer of hierarchy in packet networks gives you another chance to
benefit from statistical multiplexing (trick, because of which packet
switching rules). The more flows from individual users/subscribers you
aggregate in a single link/box, the less dispersion of their insensitivity
and the denser you pack the packets on a line (the more it's like TDM), thus
the bigger the benefits. In addition if your core serves users from
different time-zones, its efficiency will be even higher because of the
'natural TDM' human biology creates.

However you won't earn anything if the streams are already well packed
(someone has already skimmed the cream off). As Mark has mentioned, there is
no point in selling switched vll/vpn/anything to customers who fully fill
their last-miles of capacity close to that of your core-links. Well, at
least if the number of such customers is statistically significant. This is
what L1 multiplexing is invented for.

P. S. The thread made me remember my PSTN contract which explicitly states I
can't load my last-mile line higher than .1 erlang :)