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Virtual Multi-Topology Routing for QoS Constraints

Nicolas Huin, Sébastien Martin, Jérémie Leguay

TL;DR

This work tackles QoS-aware routing on legacy devices by extending multi-topology routing with virtual, silent topologies (vMTR) derived from a small set of real topologies through linear combinations of metrics via multipliers. It presents a polynomial-time, exact algorithm for vMTR when two real topologies are used, alongside a local-search benchmark for traditional MTR, and demonstrates that vMTR can substantially reduce the number of real topologies while maintaining or improving robustness to QoS fluctuations. The key contribution is a scalable design framework and ILP formulations that enable fewer LSAs and lighter control-plane signaling, while still satisfying per-demand end-to-end QoS constraints. Practically, this approach offers better adaptability to changing network conditions on devices without SR, potentially easing deployment of QoS-aware TE in heterogeneous networks.

Abstract

Multi-topology routing (MTR) provides an attractive alternative to segment routing for traffic engineering when network devices cannot be upgraded. However, due to a high overhead in terms of link state messages exchanged by topologies and the need to frequently update link weights to follow evolving network conditions, MTR is often limited to a small number of topologies and the satisfaction of loose QoS constraints. To overcome these limitations we propose vMTR, an MTR extension where demands are routed over virtual topologies that are silent, i.e., they do not exchange LSA messages, and that are continuously derived from a very limited set of real topologies, optimizing each a QoS parameter. In this context, we present a polynomial and exact algorithm for vMTR and, as a benchmark, a local search algorithm for MTR. We show that vMTR helps reducing drastically the number of real topologies and that it is more robust to QoS changes.

Virtual Multi-Topology Routing for QoS Constraints

TL;DR

This work tackles QoS-aware routing on legacy devices by extending multi-topology routing with virtual, silent topologies (vMTR) derived from a small set of real topologies through linear combinations of metrics via multipliers. It presents a polynomial-time, exact algorithm for vMTR when two real topologies are used, alongside a local-search benchmark for traditional MTR, and demonstrates that vMTR can substantially reduce the number of real topologies while maintaining or improving robustness to QoS fluctuations. The key contribution is a scalable design framework and ILP formulations that enable fewer LSAs and lighter control-plane signaling, while still satisfying per-demand end-to-end QoS constraints. Practically, this approach offers better adaptability to changing network conditions on devices without SR, potentially easing deployment of QoS-aware TE in heterogeneous networks.

Abstract

Multi-topology routing (MTR) provides an attractive alternative to segment routing for traffic engineering when network devices cannot be upgraded. However, due to a high overhead in terms of link state messages exchanged by topologies and the need to frequently update link weights to follow evolving network conditions, MTR is often limited to a small number of topologies and the satisfaction of loose QoS constraints. To overcome these limitations we propose vMTR, an MTR extension where demands are routed over virtual topologies that are silent, i.e., they do not exchange LSA messages, and that are continuously derived from a very limited set of real topologies, optimizing each a QoS parameter. In this context, we present a polynomial and exact algorithm for vMTR and, as a benchmark, a local search algorithm for MTR. We show that vMTR helps reducing drastically the number of real topologies and that it is more robust to QoS changes.
Paper Structure (14 sections, 1 theorem, 10 equations, 6 figures, 1 table, 2 algorithms)

This paper contains 14 sections, 1 theorem, 10 equations, 6 figures, 1 table, 2 algorithms.

Table of Contents

  1. Introduction
  2. Related work
  3. MTR and vMTR for QoS Constraints
  4. QoS satisfaction problem
  5. MTR: Multi-Topology Routing
  6. vMTR: virtual MTR
  7. Topology design problems
  8. MTR
  9. vMTR
  10. Algorithmic solutions
  11. MTR Algorithm
  12. vMTR Algorithm
  13. Performance evaluation
  14. Conclusion

Key Result

Proposition 1

For a given demand $k\in K$, a multiplier $\lambda_k$ is feasible for $k$, if

Figures (6)

  • Figure 1: System overview for vMTR.
  • Figure 2: Integer linear problem for the design of topologies in MTR.
  • Figure 3: Example of non shortest paths uniqueness with $\lambda=13$.
  • Figure 4: Example with $6$ demands. Intervals between $\lambda_{k}^{\min}$ and $\lambda_{k}^{\max}$ are represented for each demand $k$. The first multiplier $\lambda_1$ covers the green demands, the second multiplier $\lambda_2$ covers the blue demands and $\lambda_3$ covers the orange demand.
  • Figure 5: Comparison of MTR and vMTR using violin plots.
  • ...and 1 more figures

Theorems & Definitions (3)

  • Claim 1
  • Proposition 1
  • proof