In this paper we present a study characterizing VLAN usage in a large-sized campus network. Despite their extensive prevalence in enterprise and campus networks, the usage of VLANs has received little systematic treatment in the research community. Our study is conducted using a whitebox approach, involving data such as router configuration files obtained from network operators, and through iterative interactions with them. Our study shows that the use of virtualization is prevalent to enable users belonging to physically disparate locations to be treated as a group. We demonstrate and characterize the performance inefficiencies resulting from virtualization. We show the inefficiencies are exacerbated by sub-optimal placement policies. We also discuss potential sources of errors that may arise with configuration of VLANs, and demonstrate their prevalence in real configurations. We believe these results are a key step towards gaining deeper insights into operational practices in enterprise and campus networks, and the design of abstractions to simplify management.

No abstract