Experimental Demonstration of Impairment-Aware PCE for Multi-Bit-Rate WSONs
Journal of Optical Communications and Networking (Impact Factor: 2.06). 09/2011; 3(8):610 - 619. DOI: 10.1364/JOCN.3.000610
Source: IEEE Xplore
In emerging multi-bit-rate wavelength switched optical networks (WSONs), the coexistence of lightpaths operating at different bit-rates and modulation formats (e.g., based on amplitude and phase modulation) induces relevant traffic dependent detrimental effects that need to be considered during impairment-aware routing and wavelength assignment (IA-RWA). The considerable complexity of IA-RWA computation has driven the Internet Engineering Task Force (IETF) to propose specific path computation element (PCE) architectures in support of IA-RWA for WSONs. In this paper, following the IETF indications, we expand two PCE architectures and experimentally evaluate five different PCE architectural solutions, performing either combined or separated impairment estimation and RWA, with on-line and off-line computation of impairment validated paths, and with the possible utilization of a novel PCE Protocol (PCEP) extension. Results in terms of traffic engineering performance, path computation delivery time and amount of exchanged PCEP messages are reported and discussed to highlight the benefits and application scenarios of the considered PCE architectures.
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- "In the worst-case scenario, phase modulated (D-QPSK and DP-QPSK) lightpath has OOK neighbour lightpaths on both sides. Paolucci et al. (2011) have investigated various PCE architectures and have also experimentally evaluated these solutions. Different solutions employ either, combined or separated impairment estimation, and RWA with online and offline computation of impairment-validated paths. "
ABSTRACT: In transparent mixed-line-rate (MLR) optical networks, different line rates, on different wavelengths, can coexist on the same fiber. However, along the path, signal experiences various physical layer impairments (PLIs), and its quality also degrades. A major factor that affects transmission quality is launch power of the optical signal. On one hand, power must be high enough to ensure less noise at receiver; on the other hand, it must be lower than the limit where PLIs start to distort the signal. Further, high launch power is disruptive to both, the actual lightpath and its neighbors. In this study, we investigate the problem of determining appropriate launch power for provisioning dynamic connection requests in transparent MLR networks. We propose a heuristic that determines the appropriate launch power of a lightpath. The PLI-Average (PLI-A) approach is based on the optical reach of signals, is practical, and can adapt to the needs of network operators. Results show that performances of the proposed approach are better than the existing schemes.
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- "This testbed exploited an IV tool integrated within the network management system (NMS) and accounting for impairment information provided by an optical performance monitor. More recently, in –, two impairment-aware PCE architectures suitable for multi bit-rate WSONs were presented and evaluated on a fixed ITU-grid testbed including detrimental non-linear effects among 10 Gb/s OOK and 100 Gb/s dual polarization quadrature phase shift keying (DP-QPSK). Relevant effort has been spent within the Internet Engineering Task Force (IETF) to define the PCE architecture for WSONs. "
ABSTRACT: Flexible optical networks, based on bandwidth-variable optical cross-connects (BV-OXCs) and novel flexible transponders, are expected to significantly improve the overall spectrum efficiency with respect to traditional networks where fixed frequency spacing is applied. Flexible optical networks will exploit the BV-OXC capability to dynamically configure the reserved bandwidth as a set of frequency slots. In addition, flexible transponders will be employed to dynamically configure transmission parameters, such as bit-rate and modulation format. To enable these new configuration capabilities, network operation enhancements need to be efficiently introduced and investigated. In this study, we focus for the first time on the Path Computation Element (PCE) architecture for flexible optical networks. PCE architecture and PCE communication protocol are enhanced to maximize the spectral efficiency and to provide indications also on the specific transmission parameters to configure. Experimental demonstration is provided through two different experiments, successfully showing the PCE capability to trigger dynamic rerouting with bit-rate or modulation format adaptation. In particular, the experiments demonstrate, in a real testbed, dynamic frequency slot assignment and format adaptation from DP-16QAM to DP-QPSK at 100 Gb/s, and bit-rate adaptation at DP-16QAM from 200 Gb/s to 100 Gb/s.
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ABSTRACT: The path computation element (PCE) enables optimal path computation in single-domain (G)MPLS networks. To overcome the lack of traffic engineering (TE) information in multi-domain networks and to preserve both computation optimality and domain confidentiality, the backward-recursive PCE-based computation (BRPC) procedure has been standardized. BRPC procedure is based on PCE protocol (PCEP) and enables synchronized computation of TE label-switched paths with the requested level of reliability and quality of service requirements (i.e., guaranteed bandwidth). In this paper, the problem of computing $K$ K -survivable optimal multi-domain paths by resorting to BRPC procedure is analyzed. Extensions to PCEP protocol are discussed to achieve path optimality when domain information is kept confidential. The optimality is theoretically proved, and the computational complexity is shown to be more efficient than existing approaches. The discussed extensions are experimentally validated in an MPLS network test bed based on commercial equipments and are shown to have performance comparable to standard PCEP approach.
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