Francesco Lazzeri

Efficient label encoding in segment-routing enabled optical networks

The currently standardized GMPLS protocol suite for packet over optical networks relies on hierarchical instances of signaling sessions. Such sessions have to be established and maintained also in transit nodes, leading to complex and weighty control plane implementations. A novel technology called Segment Routing (SR) has been recently proposed to address these issues. SR relies on the source routing paradigm to provide traffic engineering solutions. In particular, the computed route for a given request is expressed as a segment list applied as an header to data packets at the ingress node. Specific algorithms are then required to perform the path computation and express the computed path through an effective segment list encoding (i.e., label stack), minimizing the segment list depth (SLD) (i.e., the number of labels included in the segment list). So far, no algorithms have been proposed to jointly provide path and segment list computation in SR-based networks. In this study, an efficient segment list encoding algorithm is proposed, guaranteeing optimal path computation and limited SLD in SR-based networks. The algorithm also accounts for equal-cost multiple paths and multiple constraints. The proposed algorithm is successfully applied to different network scenarios, demonstrating its flexibility in several use cases and showing effective performance in terms of segment list depth and introduced packet overhead.

Path Encoding in Segment Routing

Segment Routing (SR) is emerging as an innovative traffic engineering technique compatible with traditional MPLS data plane. SR relies on label stacking, without requiring a signaling protocol. This greatly simplifies network operations in transit nodes. However, it may introduce scalability issues at the ingress node and packet overhead. Therefore, specific algorithms are required to efficiently compute the label stack for a given path. This study proposes two algorithms for SR label stack computation of strict routes that guarantee minimum label stack depth. Then, SR scalability performance is investigated. Results show that, in most of the cases, SR uses label stacks composed of few labels and introduces a limited packet overhead. However, relevant scalability issues may arise in specific cases, e.g., large planar topologies.

Photonic network optimization via resource and LSPs concurrent allocation: A PCE+ concept

This paper proposes the concept of PCE+:a path computation element that performs a concurrent impairments aware routing and regenerator location for a WSON network using a fast analytical assessment of the optical lightpath feasibility.

WSON impact on optical network planning

WSON introducing restoration resource sharing for DWDM imposes new challenge to the network design. This paper illustrates resource and circuit planning algorithms used to accomplish an optimal WSON network design; some results are also shown.

Scalable approaches for path computation

Optimal and fast approaches for path computation are of paramount importance especially for the path computation elements (PCE) of generalized multi-protocol label switching (GMPLS) networks. To overcome the computational complexity, optimality must be traded for the execution time, enabling scalable computation. This paper considers the typical routing problems addressed by PCE and compares different optimization approaches based on integer linear programming (ILP) formulation and its relaxation, with the objective of assessing optimality and scalability of the approaches.