         1    1    1    2   !" 1    2            # A solution based on RSVPTE signaling protocol is proposed to encompass degradation due to crosstalk in alloptical networks. Simulation results show that it achieves low blocking probability and allows to design larger domains of transparency. © 2008 Optical Society of America $ : (060.4265) Networks, wavelength routing, (060.4250) Networks %  Lightpaths in transparent optical networks are affected by physical impairments and can be established only if the required optical signal quality is ensured. In [1] impairments such as ASE, polarization mode dispersion (PMD), chromatic dispersion (CD), and selfphase modulation (SPM) are accounted as optical signal quality criteria by associating them to cumulative physical parameters. Thus the optical signal quality can be estimated by accumulating the physical parameter values using GMPLS protocol extensions [2]. However, encompassing crosstalk in the distributed GMPLS control plane poses a harder challenge. Indeed, while the aforementioned impairments are independent of the network state (i.e., the active wavelength channels), crosstalkgenerated impairments heavily depend on the intranode relations between the active wavelength channels. Moreover, the crosstalk introduced by a newly set up lightpath might impact the optical signal quality of already established lightpaths. Thus, new lightpaths should be admitted not only if they have an acceptable signal quality, but also if the crosstalk they induce on the existing lightpaths is acceptable. Several studies [3][4] analyzed crosstalk in a centralized scenario, where a centralized network element is aware of the crosstalk characteristics of each optical node (i.e., adjacent channel (X adj ) and fabric port (X port ) crosstalk [3]), and of both the route (i.e., nodes and links) and the wavelength utilized by each lightpath. In this way, for each lightpath request the centralized element is able to quantify the degradation caused by crosstalk and take it into account in the routing and wavelength assignment. However, this estimation is not straightforward in distributed GMPLScontrolled transparent optical networks. The OSPFTE routing protocol floods neither the crosstalk characteristics of the optical nodes, nor the route taken by existing lightpaths, which are necessary to evaluate the crosstalk contribution of the existing lightpaths on the new ones and viceversa. An approach to overcome this issue implies the adding of worstcase crosstalk margins when computing the overall optical signal quality degradation. We will show that this solution penalizes too much the transparent domain size and the number of established lightpaths. In this paper a solution based on the RSVPTE signaling protocol is proposed. The degradation due to crosstalk is taken into account by the proposed Crosstalk Vector (XV) object, used to identify the preferred wavelengths [5], e.g. the ones with minimum added crosstalk. Simulation results show that the XV solution permits to effectively manage crosstalk degradation in GMPLScontrolled networks, significantly outperforming the approach based on worstcase margins in terms of blocking probability and allowed size of the domain of transparency. & ’!() * +   An optical signal to noise ratio (OSNR)based model is considered [2]. The modeled impairments, hereafter called linkimpairments, are represented by four physical parameters which cumulate linearly: 1/OSNR, PMD 2 , CD and the nonlinear phase shifting Φ NL accounting for SPM. CD and Φ NL are expressed as penalties to the OSNR cumulated along the path. Physical parameters are cumulated in an extended version of the RSVPTE protocol during the signaling phase of the lightpath set up [2]. The estimation of the optical signal quality is made at the destination node and it works as follows. The path is accepted if PMD is within an acceptable range [1] and if the global OSNR of the path (OSNR p ) is higher than a threshold OSNR th = OSNR min,RX + !. OSNR min,RX is the minimum OSNR acceptable at the receiver and ! are worstcase assumptions for not accounted impairments, such as non linear effects, polarizationdependent losses, and ageing, added to guarantee that no intolerable lightpath is established. If the crosstalk is not explicitly estimated, margins can be used to take the crosstalk contribution into account as well.