Operator interviews and anecdotal evidence suggest that
an operator’s ability to manage a network decreases as
the network becomes more complex. However, there is
currently no way to systematically quantify how complex
a network’s design is nor how complexity may impact
network management activities. In this paper, we
develop a suite of complexity models that describe the
routing design and configuration of a network in a succinct
fashion, abstracting away details of the underlying
configuration languages. Our models, and the complexity
metrics arising from them, capture the difficulty of
configuring control and data plane behaviors on routers.
They also measure the inherent complexity of the reachability
constraints that a network implements via its routing
design. Our models simplify network design and
management by facilitating comparison between alternative
designs for a network. We tested our models
on seven networks, including four university networks
and three enterprise networks. We validated the results
through interviews with the operators of five of the networks,
and we show that the metrics are predictive of the
issues operators face when reconfiguring their networks.