# An Availability-Enhanced Service Function Chain Placement Scheme in Network Function Virtualization

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## Abstract

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## 1. Introduction

- We formulate the problem of service function chain placement as an integer linear programing (ILP) optimization problem with the objective of minimizing end-to-end delay of an SFC.
- We propose a heuristic algorithm to improve availability by distributing VNFs on multiple substrate nodes on the basis of a layered graph approach.
- We carry out simulation to evaluate the performance of the availability-enhanced scheme in terms of availability, end-to-end delay, and computation time cost on different topologies.

## 2. Related Work

## 3. Layered Graph System Model and Problem Formulation

#### 3.1. Problem Formulation

#### 3.2. Layered Graph System Model

- Create $t$ copies of substrate network graph $G$. The network topology of each copy is the same as $G$’s topology. We denote ${G}^{0}$ as the original substrate network graph and ${G}^{i}$ as the $i$th copy network graph.
- Connect substrate nodes in neighboring network graphs ${G}^{i-1}$ and ${G}^{i}$ vertically if they can host $i$th VNF of the SFC.
- The original substrate graph ${G}^{0}$, $t$ copies of substrate network graphs ${G}^{1}~{G}^{t}$, and edges between these layered networks compose a new graph, denoted as ${G}^{whole}$.
- Find a shortest path between the ingress node in ${G}^{0}$ and the egress node in ${G}^{whole}$. Each transition node on the shortest path connecting $i-1$ and $i$ layers is the selected substrate node to host the $i$th VNF of the SFC.

#### 3.3. Availability Issues

## 4. Availability-Enhanced SFC Placement Scheme

Algorithm 1 Node selection: | |

Algorithm 2 Layered graph based routing: | |

## 5. Evaluation and Analysis

#### 5.1. Simulation Setup

#### 5.2. Performance of Availability

#### 5.3. Performance of End-To-End Latency of SFC

#### 5.4. Performance of Computation Time

## 6. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 2.**Layered graph approach for deployment of two virtual network functions (VNFs) in a service function chain (SFC).

**Figure 6.**Performance of average end-to-end latency of SFC (100 nodes, edge connection probability 0.5).

**Figure 7.**Performance of computation time of proposed algorithm (100 nodes, edge connection probability 0.5).

**Figure 8.**Performance of computation time of proposed algorithm (50 nodes, edge connection probability 0.5).

**Table 1.**Number of times availability requirements were not met (probability of edge connection 1.0).

Number of VNFs | 50 Nodes | 60 Nodes | 70 Nodes | 80 Nodes | 90 Nodes | 100 Nodes |
---|---|---|---|---|---|---|

5 VNFs | 0 | 0 | 0 | 0 | 0 | 0 |

10 VNFs | 0 | 1 | 0 | 0 | 0 | 0 |

15 VNFs | 1 | 1 | 0 | 1 | 1 | 0 |

20 VNFs | 2 | 1 | 0 | 1 | 1 | 1 |

**Table 2.**Number of times availability requirements were not met (probability of edge connection 0.5).

Number of VNFs | 50 Nodes | 60 Nodes | 70 Nodes | 80 Nodes | 90 Nodes | 100 Nodes |
---|---|---|---|---|---|---|

5 VNFs | 0 | 0 | 0 | 0 | 0 | 0 |

10 VNFs | 0 | 0 | 0 | 1 | 0 | 1 |

15 VNFs | 1 | 0 | 1 | 1 | 1 | 0 |

20 VNFs | 2 | 2 | 1 | 1 | 1 | 1 |

**Table 3.**Number of times availability requirements were not met (probability of edge connection 0.1).

Number of VNFs | 50 Nodes | 60 Nodes | 70 Nodes | 80 Nodes | 90 Nodes | 100 Nodes |
---|---|---|---|---|---|---|

5 VNFs | 0 | 0 | 1 | 0 | 0 | 0 |

10 VNFs | 1 | 1 | 0 | 1 | 0 | 1 |

15 VNFs | 1 | 0 | 1 | 0 | 0 | 1 |

20 VNFs | 2 | 2 | 1 | 1 | 1 | 1 |

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**MDPI and ACS Style**

Xu, Y.; Kafle, V.P.
An Availability-Enhanced Service Function Chain Placement Scheme in Network Function Virtualization. *J. Sens. Actuator Netw.* **2019**, *8*, 34.
https://doi.org/10.3390/jsan8020034

**AMA Style**

Xu Y, Kafle VP.
An Availability-Enhanced Service Function Chain Placement Scheme in Network Function Virtualization. *Journal of Sensor and Actuator Networks*. 2019; 8(2):34.
https://doi.org/10.3390/jsan8020034

**Chicago/Turabian Style**

Xu, Yansen, and Ved P. Kafle.
2019. "An Availability-Enhanced Service Function Chain Placement Scheme in Network Function Virtualization" *Journal of Sensor and Actuator Networks* 8, no. 2: 34.
https://doi.org/10.3390/jsan8020034