Computer Science Department
School of Computer Science, Carnegie Mellon University


Refactoring Network Control and Management:
A Case for the 4D Architecture

Albert Greenberg, Gisli Hjalmtysson, David A. Maltz, Andy Myers,
Jennifer Rexford, Geoffrey Xie, Hong Yan, Jibin Zhan, Hui Zhang

September 2005

Keywords: Network control plane, centralized versus distributed control, decision plane, dissemination plane, routing design, routing protocols

We argue for the refactoring of the IP control plane to support network-wide objectives and control. We put forward a design that refactors functionality into a novel 4D architecture composed of four separate planes: decision, dissemination, discovery and data. All decision-making logic is moved out of routers along with current management plane functions to create a logically centralized decision plane, where network-level objectives and policies are specified and enforced by direct configuration of states on individual network elements. Pullingmuch of the control state and logic out of the routers enables both simpler protocols, which do not have to embed decision-making logic, and more powerful decision algorithms for implementing sophisticated goals. Remaining on the routers is a wafer-thin class of intrinsically distributed control functions. These support the discovery plane, consisting of elementary functions to discover topology and network state, and the dissemination plane, consisting of elementary functions to distribute explicit instructions to manipulate the data plane forwarding mechanisms.

This paper motivates the need for a new approach to network control and management, describes the 4D architecture, and sketches the design space and challenges posed by the architecture. As a first exploration of the design space and its challengs, we have constructed a working prototype that implements the 4D architecture. Through evaluation of this prototype on 9 different network topologies derived from production networks, we demonstrate that (i) the 4D architecture can achieve subsecond reconvergence times upon single link or router failures and can adequately deal with other failure scenarios including network partition; (ii) the 4D architecture is able to implement a network design intent such as a reachability matrix more robustly than currently possible; and (iii) the 4D architecture does not introduce excess overhead.

30 pages

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