On Orchestrating Virtual Network Functions in NFV (1503.06377v2)

Abstract: Middleboxes or network appliances like firewalls, proxies and WAN optimizers have become an integral part of today's ISP and enterprise networks. Middlebox functionalities are usually deployed on expensive and proprietary hardware that require trained personnel for deployment and maintenance. Middleboxes contribute significantly to a network's capital and operational costs. In addition, organizations often require their traffic to pass through a specific sequence of middleboxes for compliance with security and performance policies. This makes the middlebox deployment and maintenance tasks even more complicated. Network Function Virtualization (NFV) is an emerging and promising technology that is envisioned to overcome these challenges. It proposes to move packet processing from dedicated hardware middleboxes to software running on commodity servers. In NFV terminology, software middleboxes are referred to as Virtualized Network Functions (VNFs). It is a challenging problem to determine the required number and placement of VNFs that optimizes network operational costs and utilization, without violating service level agreements. We call this the VNF Orchestration Problem (VNF-OP) and provide an Integer Linear Programming (ILP) formulation with implementation in CPLEX. We also provide a dynamic programming based heuristic to solve larger instances of VNF-OP. Trace driven simulations on real-world network topologies demonstrate that the heuristic can provide solutions that are within 1.3 times of the optimal solution. Our experiments suggest that a VNF based approach can provide more than 4x reduction in the operational cost of a network.

• The paper introduces dynamic VNF orchestration using an ILP model and a near-optimal heuristic to tackle deployment inefficiencies.
• It demonstrates that the heuristic achieves solutions within 1.3 times of the optimal, significantly reducing operational expenses.
• Extensive simulations on realistic network topologies validate the model’s scalability and potential for cost savings in NFV environments.

A Discussion on Virtualized Network Functions Orchestration Optimization

The paper "On Orchestrating Virtual Network Functions in NFV" by Bari et al. addresses a key challenge in the Network Function Virtualization (NFV) paradigm— the Virtualized Network Functions Orchestration Problem (VNF-OP). This work primarily focuses on the dynamic allocation and placement of Virtual Network Functions (VNFs) as a solution to the inefficiencies associated with the static deployment of hardware middleboxes.

The paper sets the stage by delineating the drawbacks of hardware-based middleboxes, which, although integral to contemporary networks, incur substantial capital (CAPEX) and operational expenses (OPEX). These traditional setups are inflexible and vendor-specific, demanding costly hardware replacements for adding new functionalities.

In contrast, VNFs leverage commodity servers to replicate middlebox functions but with significantly reduced costs and enhanced flexibility. The orchestration of VNFs, therefore, becomes crucial to optimizing their deployment and reducing network expenses. This paper identifies the VNF-OP as the task of optimally determining the count and placement of VNFs to minimize OPEX while maintaining service quality.

Methodology and Contribution

The authors present an Integer Linear Programming (ILP) formulation of the VNF-OP to achieve optimal solutions for small-scale scenarios. To address the computational complexity involved in larger networks, the paper posits a dynamic programming-based heuristic that offers near-optimal solutions with considerable computational efficiency. This heuristic solution is shown to perform within 1.3 times the optimal solution, evaluated using realistic topologies and traffic patterns.

Key Contributions Include:

• Insight into VNF-OP: The paper formulates and quantifies the benefits of dynamic VNF orchestration, demonstrating a potential greater than fourfold reduction in operational expenditure.
• Algorithmic Solutions: An ILP model for precise solutions ready for implementation in computational environments like CPLEX. The heuristic algorithm simplifies the complexity, providing efficient near-optimal solutions suitable for real-world application.
• Numerical Validation: Extensive simulations on real-world network topologies validate the model's scalability and the heuristic's efficacy, presenting compelling evidence of cost savings compared to fixed hardware deployments.

Implications and Future Directions

From a theoretical lens, this research enriches the NFV domain by providing a structured approach to a problem critical for balancing network performance and cost. Practically, these insights have profound implications for network operators aiming to leverage NFV for reducing OPEX while maintaining service delivery standards.

Looking forward, this paper opens up prospects for merging VNFs and traditional hardware functions within a hybrid framework to address varying network demands dynamically. There remains scope to enhance resilience through backup VNF strategies and extend this orchestration framework to multi-cloud environments where VNFs can further enhance operational efficiency and service agility.

Conclusion

The paper provides a robust approach towards addressing VNF orchestration challenges, with its methodologies potentially serving as a foundation for future NFV management systems. As VNFs gain traction, the contributions of this work remain salient for network engineers and researchers dedicated to optimizing network resource utilization and cost efficiency in an NFV-enabled future.