Mattia Cantono, Vittorio CurrI ICTON 2017 paper Th.B4.5 Flex- vs. fix-grid merit in progressive loading of networks already carrying legacy traffic Mattia Cantono, Vittorio CurrI Optcom group Dipartimento di Elettronica e Telecomunicazioni Politecnico di Torino Italy

Supposed to be defragmented motivation Total available bandwidth Allocated bandwidth Supposed to be defragmented Bandwidth available for dynamic spectral allocation Bstat Bdyn Btot Most networks are running out of spectrum New – and supposedly dynamic – traffic has to be allocated on the residual bandwidth What is the advantage of flex- vs. fix-grid given the residual bandwidth?

outline The generalized OSNR as l QoT and the LOGO control plane and the statistical network assessment process (SNAP) Residual bandwidth percentage Traffic model Fix- and fle-grid transceivers The Italian network topology Results as BP vs. Total allocated traffic Comments and conclusions

An all optical transparent network With the knoweledge of the network physical details We set the optimal power per channel and manage the network as an inverse-OSNR (IOSNR) weighted graph A E B D H C G I F Example: QoT for lightpath travelling from node A to node G through nodes C and E: where

Statistical network assessment process Start Network evolution storage J-th Traffic request Traffic model RWA algorithm description saturation i-th Monte Carlo run I > NMC i=i+1 j=j+1 NO snap-shot @ i,j YES SNAP Metrics’ evolution vs. j Static Metrics M. Cantono et al. “Potentialities and Criticalities of Flexible-Rate Transponders in DWDM networks: a Statistical Approach ,” JOCN, 2016 V. Curri et. al., “Elastic All-Optical Networks: a New Paradigm Enabled by the Physical Layer. How to Optimize Network Performances?,” JLT, 2017

Residual bandwidth percentage (RBP) Btot: C-band Allocated bandwidth Supposed to be defragmented Bandwidth available for dynamic spectral allocation Bstat Bdyn Total available bandwidth: C-band of 4000 GHz RBP=Bdyn/Btot x 100 [%] We consider three different scenarios Lightly loaded network: RPB = 25% Moderately loaded network: RBP = 50% Heavily loaded network: RBP = 75%

Traffic model Any-to-any traffic Flat probability in traffic requests Traffic requests «groomed» at RG = 20 Gbps RG = 40 Gbps RG = 100 Gbps 5000 Monte-Carlo progressive network loading up to blocking probability BP of 30% RSWA algorithm: shortest path up to kmax=50

Fix and flex grid transceivers Fix-grid fLPi+1 fLPi+2 fLPi+3 fLPi+4 Flex-grid fLPi fLPi+1 fLPi+2 fLPi+3 fLPi+4 f WDM grid: Df =37.5 GHz RS =31.25 Gbaud Coding overhead = 25% Guard-band: = 6.25 GHz Grid: Df=RS,slot =12.5 Gbaud, up to 5 slots Coding overhead = 25% fch tunable on 6.25 GHz Guard-band = 6.25 GHz Modulation Format Net Bit rate (Rb) Gbps PM-BPSK 50 PM-QPSK 100 PM-16QAM 200 PM-64QAM 300 Modulation Format Net Bit rate (Rb) Gbps Ns=1 Ns=2 Ns=3 Ns=4 Ns=5 PM-BPSK 20 40 60 80 100 PM-QPSK 120 140 280 PM-16QAM 160 240 320 400 PM-64QAM 360 480 600

The italian network topology

Results Metrics Normalized Network Traffic (T) is the total traffic loading the network normalized with respect the available bandwidth: it is indeed a specrat eexploitation efficiency Blocking probability (BP): it is the probability that a new traffic request is rejected Results are shown as BP vs. T for the different scenarios Comparisons at BP = 1% are shown as well

Blocking Probability [%] BP vs. T: fix-grid 5 10 15 20 25 30 35 0.1% 1% 10% 30% Normalized Network Traffic [Tbps/THz] Blocking Probability [%] … RBP= 25% _._RBP= 50% _ _RBP= 75% __ RG= 20G __ RG= 40G __ RG=100G

BP vs. T: flex-grid 5 10 15 20 25 30 35 0.1% 1% 10% 30% Blocking Probability [%] Normalized Network Traffic [Tbps/THz] … RBP= 25% _._RBP= 50% _ _RBP= 75% __ RG= 20G __ RG= 40G __ RG=100G

Flex vs. Fix @ bp=1% RBP=25% RBP=25% RBP=25% RBP=50% RBP=50% RBP=50% Normalized Network Traffic [Tbps/THz] Residual Bandwidth [%] RG = 20 Gbps Normalized Network Traffic [Tbps/THz] Residual Bandwidth [%] RG = 40 Gbps Residual Bandwidth [%] Normalized Network Traffic [Tbps/THz] RG = 100 Gbps RBP=25% Flex2Fix  2.5 RBP=50% RBP=75% Flex2Fix  3.3 RBP=25% Flex2Fix  2.5 RBP=50% RBP=75% RBP=25% Flex2Fix  1.3 RBP=50% RBP=75%

conclusions We showed that flex-grid is always advantageous with respect to fix-grid The relative advantage that is around 2.5 times for grooming sizes of 20 and 40 Gbps, decreases to 1.3 times for RG= 100 Gbps because of saturation effects Spread of spectral efficiency for different scenarios of RBP and RG is much smaller for flex-grid, while using fix-grid the larger RG, the better

This work was supported by CISCO Systems within a SRA contract