动态RWA（路由与波长分配）问题是光网络中的重要问题，关系到网络的服务质量。文章提出一种改进ACO（蚁群优化）算法，通过对蚂蚁进行编组，实现组内最优解的信息素加强，且按组内最优解收敛，增强了全局信息对蚁群的指导作用，以取得更优结果。仿真结果表明，相比于传统ACO算法，该改进算法能显著降低阻塞率，提高网络的服务质量。

A quality-of-service (QoS) aware scheme, called precautionary performance monitoring, is proposed to solve the optical impairments and congestion control in coherent optical orthogonal frequency division multiplexed (CO-OFDM) networks. The centralized path computation element (PCE) extensions based on the QoS level are applied to optical performance monitoring in this letter.

Transport network paths are typically bidirectional and symmetrical. In multi-protocol label switching (MPLS) and generalized MPLS (GMPLS) mechanisms, independent labels are distributed for bidirectional paths. Thus, the requirement of the MPLS transport profile (MPLS-TP), which is a new transport technology, could not be satisfied efficiently. A novel label distribution mechanism for bidirectional paths in MPLS-TP networks is proposed. Labels distributed by the mechanism are symmetrical and can reflect the pairing relationship of the forward and backward directions of the transport path.

Path protections have become increasingly important for current mesh optical networks because fast restorations in generalized multiprotocol label switching (GMPLS) networks are uncertain. However, setting up additional disjoint paths to protect connections leads to more path setup blocking and signaling collisions. We analyze signaling collisions, path blocking and blocking probability, as well as calculate node-to-node blocking probabilities. A signaling-based path-segment protection (PSP) is proposed, which integrates segment protections and path protections as well as enhances the performance of path protections and ring protections. The setup of PSP connections causes less blocking probability than the setup of path protection connections in the simulations.

To improve the restoration performance of a multicast service of multi-protocol label switching transport profile (MPLS-TP) enabled optical network, this letter proposes a local-node initiated fast restoration (LNIFR) scheme for MPLS-TP optical multicast service. The proposed scheme allows the local node to establish a segment of fast loopback label switch path by the local node along the upstream of the failed node or link to the nearest downstream node. The fast restoration of optical multicast trees is realized through this part restoration, which focuses on failed node or link. Simulation analysis and results demonstrate that the new scheme outperforms the other schemes in terms of restoration time and success rate.

A contention resolution scheme, P-cycle auto-switching (PCAS), is proposed in wavelength-switched optical networks (WSONs) based on generalized multi-protocol label switching (GMPLS) to solve backward blocking. This system permits the preferable request and switches the other to a backup path generated by the P-cycle. Simulation results show that the PCAS scheme is effective in mitigating backward blocking, especially under concentrated load.

Current generalized multi-protocol label switching (GMPLS) standards do not include adequate models for wavelength-switched optical networks (WSON) in recovery mechanisms. In this letter, GMPLS/path computation element (PCE) extensions are applied for the restoration of the lightpaths disrupted by collision or optical impairment. A reserved de°ection routing scheme is proposed to achieve fast restoration. It uses the expanded PCE component to compute and assign the backup paths for lightpath recovery. Numerical results demonstrate that this scheme is effective and low cost.

A novel wavelength assignment scheme called the wavelength pre-assignment collision schedule (WPCS) is proposed for wavelength-routed networks. The WPCS pre-assigns the wavelength at the forward detection phase, and schedules the potential collision by priority. The potential collision is scheduled at the forward detection phase and the blocking of the wavelength assignment is reduced. Simulation is conducted with several other existing schemes. The numerical results show thatWPCS performs better than other schemes in blocking probability under various traffic conditions.