System and method for communication network service connectivity

1. A routing and spectrum assignment (RSA) element operative to provide physical layer impairment (PLI) aware network path selection on a Transport Software-Defined Network (T-SDN), the RSA element operative to:

receive a connection request to connect a first node with a second node of the T-SDN;

receive OSNR measurements from controllers in communication with links of the T-SDN;

receive a network utilization parameter for the T-SDN;

identify a set of n network paths that connect the first node with the second node; and,

select a network path, from a sub-set of network paths which exclude paths based on a discriminant, the network path connecting the first node with the second node based on the received OSNR measurements and the received network utilization parameter.

2. The RSA element of claim 1 , wherein the network path is selected by selectively applying network path selection methods based on the network utilization parameter.

3. The RSA element of claim 2 , wherein if the network utilization parameter is below a minimum utilization threshold level, the network path is selected by a linear path selection in which the discriminant excludes non-linear links; and, assigning the network path from the identified network paths with the highest linear OSNR.

4. The RSA element of claim 3 , wherein if the network utilization parameter is below the minimum utilization threshold level, the linear path selection comprises the RSA element is further operative to:

identify a set of n network paths through the network that connect the first node with the second node and are absent non-linear links,

select p network paths from the set of n network paths that have the highest linear OSNR levels, and,

select a network path from the sub-set of p network paths that balances the wavelength utilization between the first node and the second node of the network.

5. The RSA element of claim 2 , wherein:

the discriminant is linear OSNR; and

if the network utilization parameter is above a minimum utilization threshold level, the network path is selected by identifying a sub-set of network paths with the highest linear OSNR; and, assigning the network path from the identified sub-set of network paths based on the highest combination of linear OSNR and non-linear OSNR.

6. The RSA element of claim 5 , wherein if the network utilization parameter is above the minimum utilization threshold level, the sub-set of network paths are identified by:

performing network path and spectrum assignment operations on the set of n network paths to generate, for each network path a corresponding linear OSNR value and a non-linearity indicator indicating a level of non-linearity along that network path;

rank sorting the n network paths based on the corresponding linear OSNR values; and,

including highest ranked network paths and only one network path having a corresponding non-linearity indicator indicating the level of non-linearity along that network path is below a non-linear threshold level.

7. The RSA element of claim 2 , in which the discriminant is non-linear links such that if the network utilization parameter is above a maximum utilization threshold level, the network path is selected by identifying network paths that exclude non-linear links; and, assigning the network path from the identified network paths with the highest linear OSNR.

8. The RSA element of claim 7 , wherein the identifying network paths that exclude non-linear links comprises:

selecting a sub-set of p network paths from the set of n network paths that have no non-linear links,

performing a linear network path and spectrum assignment operation on the sub-set of p network paths to generate a corresponding set of OSNR values, and,

assigning the network path having a corresponding highest linear OSNR value from the sub-set of p network paths.

9. The RSA element of claim 1 , wherein the network utilization parameter is based on at least one of:

a network blocking probability;

a network load; and,

a network congestion metric.

10. The RSA element of claim 1 , operative to select the network path, from a sub-set of network paths which exclude paths based on a discriminant, the network path connecting the first node with the second node based on the received OSNR measurements and the received network utilization parameter by:

rank sorting the set of n network paths based on a linear OSNR value for each path to order the paths from highest OSNR to lowest OSNR;

evaluating the set of n network paths to identify a sub-set of q network paths, wherein the discriminant is OSNR, starting from the network path with the highest OSNR value until the sub-set q includes one network path with no non-linear values;

evaluating the sub-set of q network paths to obtain for each the network links, updated linear OSNR and updated non-linear OSNR values; and,

assigning the network path with the highest combination of updated linear OSNR and updated non-linear OSNR values as the network connection.

11. The RSA element of claim 10 ,

wherein the evaluating the sub-set of q network paths to obtain, for each the network links, updated linear OSNR and updated non-linear OSNR values further comprises:

evaluating, for each link of the q network paths, the updated non-linear OSNR value for that link, and performing non-linear OSNR calculations on that link if the updated non-linear OSNR value is over an OSNR threshold level.

12. The RSA element of claim 1 , operative to select the network path, from a sub-set of network paths which exclude paths based on a discriminant, the network path connecting the first node with the second node based on the received OSNR measurements and the received network utilization parameter by:

identifying a set of n network paths through the network that connect the first node with the second node and are absent non-linear links,

performing route selection by selecting a sub-set of p network paths from the set of n network paths, wherein the discriminant is OSNR, that have the best linear OSNR, and,

selecting a network path from the sub-set of p network paths that meets a number of wavelengths threshold and assigning the selected network path.

13. The RSA element of claim 12 , wherein, before the RSA element identifies the set of n network paths, the RSA element is further operative to:

evaluating a network utilization parameter of the network, wherein if the network parameter is below a minimum threshold level, the route selection comprises selecting the sub-set of p network paths from the set of n network paths that have no non-linear links, and the assignment comprises performing a linear path and wavelength assignment operation on the sub-set of p network paths to generate a corresponding set of OSNR values and assigning the network path having a corresponding highest linear OSNR value.

14. The RSA element of claim 12 , wherein the network utilization parameter comprises one of:

a network blocking probability;

a network load; and,

a network congestion metric.