Problem: Managing an enterprise or data center network is difficult because middleboxes must be placed on the path of the traffic they must filter. This is a not a problem for some companies who do not have a great need for firewalls, etc. But if you have a system with many firewalls, middleboxes are a problem. Financial institutions have multiple layers with many middleboxes. Middleboxes are placed at a chokepoint in the network. Info must pass a particular point for firewalls and load balancers.
Solution: The solution proposed by the authors takes the middleboxes out of the network path. The solution specifically routes the data through the firewall. Implicit routing causes one to route the packet through a path with the firewall. Explicit routing through the middlebox is necessary to ensure the data goes through the middlebox.
Tradeoffs: The solution uses a little extra bandwidth. But explicit routing ensures correctness. Other solutions to the bottleneck of middleboxes involve throwing resources at the problem; more middleboxes at the bottlenecks.
Future Influence: The most important contribution of this paper is that it makes the case higher-level policy control in a data center, specifically the use of indirection within a datacenter. Many data center managers are happy with what they have, but this is less of a hurdle than introducing a new architecture in the internet. Such a new proposal is possible in a datacenter because there are many new clean slates (including upgrades being a clean slate).