Impact of Processing-Resource Sharing on the Placement of Chained Virtual Network Functions

TL;DR

This paper examines how processing-resource sharing impacts the placement of chained Virtual Network Functions in NFV, balancing consolidation benefits against latency penalties caused by context switching and upscaling costs.

Contribution

It identifies and analyzes two types of processing-resource sharing costs affecting VNF placement, providing insights for optimizing NFV deployment under latency constraints.

Findings

Processing-resource sharing introduces context switching and upscaling costs.

These costs influence VNF placement strategies to meet latency requirements.

Evaluation shows trade-offs between consolidation and performance penalties.

Abstract

Network Function Virtualization (NFV) provides higher flexibility for network operators and reduces the complexity in network service deployment. Using NFV, Virtual Network Functions (VNF) can be located in various network nodes and chained together in a Service Function Chain (SFC) to provide a specific service. Consolidating multiple VNFs in a smaller number of locations would allow decreasing capital expenditures. However, excessive consolidation of VNFs might cause additional latency penalties due to processing-resource sharing, and this is undesirable, as SFCs are bounded by service-specific latency requirements. In this paper, we identify two different types of penalties (referred as "costs") related to the processingresource sharing among multiple VNFs: the context switching costs and the upscaling costs. Context switching costs arise when multiple CPU processes (e.g., supporting different VNFs) share the same CPU and thus repeated loading/saving of their context is required. Upscaling costs are incurred by VNFs requiring multi-core implementations, since they suffer a penalty due to the load-balancing needs among CPU cores. These costs affect how the chained VNFs are placed in the network to meet the performance requirement of the SFCs. We evaluate their impact while considering SFCs with different bandwidth and latency requirements in a scenario of VNF consolidation.