Renaud Hartert

A Declarative and Expressive Approach to Control Forwarding Paths in Carrier-Grade Networks

SDN simplifies network management by relying on declarativity (high-level interface) and expressiveness (network flexibility). We propose a solution to support those features while preserving high robustness and scalability as needed in carrier-grade networks. Our solution is based on (i) a two-layer architecture separating connectivity and optimization tasks; and (ii) a centralized optimizer called framework, which translates high-level goals expressed almost in natural language into compliant network configurations. Our evaluation on real and synthetic topologies shows that framework improves the state of the art by (i) achieving better trade-offs for classic goals covered by previous works, (ii) supporting a larger set of goals (refined traffic engineering and service chaining), and (iii) optimizing large ISP networks in few seconds. We also quantify the gains of our implementation, running Segment Routing on top of IS-IS, over possible alternatives (RSVP-TE and OpenFlow).

Conflict Ordering Search for Scheduling Problems

We introduce a new generic scheme to guide backtrack search, called Conflict Ordering Search (COS), that reorders variables on the basis of conflicts that happen during search. Similarly to generalized Last Conflict (LC), our approach remembers the last variables on which search decisions failed. Importantly, the initial ordering behind COS is given by a specified variable ordering heuristic, but contrary to LC, once consumed, this first ordering is forgotten, which makes COS conflict-driven. Our preliminary experiments show that COS - although simple to implement and parameter-free - is competitive with specialized searches on scheduling problems. We also show that our approach fits well within a restart framework, and can be enhanced with a value ordering heuristic that selects in priority the last assigned values.

Simple and Scalable Time-Table Filtering for the Cumulative Constraint

Cumulative is an essential constraint in the CP framework, and is present in scheduling and packing applications. The lightest filtering for the cumulative constraint is time-tabling. It has been improved several times over the last decade. The best known theoretical time complexity for time-table is

Multi-objective large neighborhood search

On \log n

Expect the unexpected: Sub-second optimization for segment routing

Onlogn introduced by Ouellet and Quimper. We show a new algorithm able to run in On, by relying on range min query algorithms. This approach is more of theoretical rather than practical interest, because of the generally larger number of iterations needed to reach the fixed point. On the practical side, the recent synchronized sweep algorithm of Letort et al, with a time-complexity of

Kiwi - A Minimalist CP Solver.

On^2