Middleboxes No Longer Considered Harmful
Michael Walfish, Jeremy Stribling, Maxwell Krohn, Hari Balakrishnan, Robert Morris, Scott J. Shenker · 2004
Intermediate network elements, like network address translators (NATs), firewalls, and transparent caches are now commonplace. The usual reaction in the network architecture community to these so-called middleboxes is a combination of scorn (because they violate important architectural principles) and dismay (because these violations make the Internet less flexible). While we appreciate the harm these architectural violations cause, we also recognize that middleboxes have become an Internet fact of life for important reasons. In order to retain their functionality while eliminating their dangerous side-effects, we propose an extension to the Internet architecture, called the Delegation-Oriented Architecture (DOA), that not only allows, but also facilitates, the deployment of middleboxes. DOA involves two relatively modest changes to the current architecture: (a) a set of references that are carried in packets and serve as persistent host identifiers and (b) a way to resolve these references to delegates chosen by the referenced host. We illustrate this architecture with two examples: network-extension boxes and network filters.