On the benefits of backup resource sharing in transparent and opaque networks

Transparent networks promise a cost efficient solution for future core and metro networks, due to the high cost-efficiency for switching trunk traffic. Network availability is an important performance parameter for network operators, who are incorporating protection and restoration mechanisms in the network to achieve competitive advantages. This paper will focus on the reduction in Capital Expenditures (CapEx) expected from implementing protection in transparent networks. We dimension a nationwide transparent network topology for restoration and path protection mechanisms using transparent and opaque architectures. We investigate the gain through protection sharing in relation to the number of links in a meshed network and the offered load on a population of 1000 generated 2-connected planar topologies with 14 nodes. We show that the gain in a transparent network is heavily dependent on the offered load, with almost no relative gain for low load (no required parallel line systems). We also show that, for opaque networks, this relative gain by protection sharing is independent of the traffic load and shows a small dependency on the number of links in the network. The node CapEx reduction for high load is comparable to the CapEx reduction in opaque OTN systems. This is rather surprising as in OTN systems the number of transceivers and linecards and the size of the OTN switching matrix all decrease, while in transparent networks only the degree of the ROADM (number and size of WSSs in the node) decreases while the number of transponders remains the same.