Page th IETF – Dublin, Ireland, July 2008 Performance Evaluation of PCE Architectures for Wavelength Switched Optical Networks Editors: Greg Grotto Young Huawei draft-bernstein-pce-wson-evaluation-00.txt

Page th IETF – Dublin, Ireland, July 2008 Authors Aessio Giorgetti (Scuola Superiore Sant’Anna, Pisa, Italy) F. Paolucci (Scuola Superiore Sant’Anna, Pisa, Italy) Filippo Cugini (CNIT, Pisa, Italy) L. Valcarenghi (Scuola Superiore Sant’Anna, Pisa, Italy) P. Castoldi (Scuola Superiore Sant’Anna, Pisa, Italy) G. Bernstein (editor, Grotto Networking) Y. Lee (editor, Huawei)

Page th IETF – Dublin, Ireland, July 2008 PCE Arch/Info Alternatives How much information does PCE have about wavelength availability in a WSON? –Coarse grained (based on existing GMPLS) –Detailed link wavelength status Architecture Alternatives –Routing + WA (on one PCE) –Routing (PCE) + Distributed WS (signaling) –Routing (PCE) + WA (separate PCE)

Page th IETF – Dublin, Ireland, July 2008 Simulation Network 27 Nodes, 55 Links –Either 32 or 80 channel WDM links –Key performance figure measure was blocking probability –Uniform traffic distribution, Poisson arrivals, load in Erlang’s varied

Page th IETF – Dublin, Ireland, July 2008 Simulation Experiments Fully Distributed (FD) –the PCE was assumed to reside on the originating node for the light path and only had aggregate wavelength usage (bandwidth) information. In this case a least congested route (LCR) path selection algorithm was used. R- case –a centralized PCE was assumed to compute paths (but not wavelength assignment) based on the same LCR algorithm as above. Then distributed wavelength assignment via signaling was utilized. For the purposes of blocking probability calculation this leads to similar results as the previous case. R+ case –a centralized PCE was assumed to compute paths (but not wavelength assignment) based on detailed link wavelength utilization/availability. A variant of the LCR algorithm that understood the wavelength continuity constraint was employed.

Page th IETF – Dublin, Ireland, July 2008 Simulation Experiments (cont.) Separate Routing from Wavelength Assignment (WA-K) –In this case routing (but not wavelength assignment) was performed at the ingress node based only on aggregate wavelength utilization (bandwidth). The results of this computation are then passed to a separate PCE server for wavelength assignment (WA). It was assumed that this separate WA PCE had detailed knowledge of link wavelength utilization. –An important variation of the above is when the first route computation element (in this case on the ingress node) calculates K alternative paths which are then fed to the WA PCE. Combined Routing and Wavelength Assignment (R+WA) –In this case a central PCE was responsible for both routing and wavelength assignment. This requires the PCE to have detailed link wavelength utilization information.

Page th IETF – Dublin, Ireland, July 2008 Simulation Results

Page th IETF – Dublin, Ireland, July 2008 Simulation Results (cont.) Figure 3. WA, WA-2, WA-3 and R+WA scenarios with 32 wavelengths per link, 1/u = 60s.

Page th IETF – Dublin, Ireland, July 2008 Conclusions All three PCE architectural scenarios have merit –Routing (PCE) and WA (separate PCE) architecture can be particularly useful as shown in the reduced blocking numbers for the WA-2, and WA-3 simulation experiments. –PCEP extensions should not exclude this architectural alternative. More Info –A. Giorgetti, F. Paolucci, F. Cugini, L. Valcarenghi, P. Castoldi, G. Bernstein, "Routing and Wavelength Assignment in PCE-based Wavelength Switched Optical Networks (WSONs)", To Appear ECOC 2008.