This is a paper that generated both broad consensus and wide disagreements from the reviewers. All of them agreed on the importance of the topic it addressed and on the fact that it was a well written and articulate treatise of the issues faced by today's network management systems. There was, however, a considerable and diverging range of opinions regarding the proposal put forth in the paper, i.e., the 4D architecture. This being said, this is definitely a paper worth reading, but one for which the reader needs to maintain a critical perspective and in a sense view the paper more as an editorial positing a new perspective and approach, than as a report documenting the success, potential or not, of a new solution. The authors explicitly articulate that much of the work remains to be done and that it faces significant challenges, but this is nevertheless worth keeping in mind. In other words, this is a paper that will get you thinking and that aspect more than the specific proposal it puts forth is probably where its main value lies. Let me briefly summarize the positive and negative sides of the paper as identified in the reviews. On the positive side, the problem that the paper identifies is, as alluded to earlier, clearly an important one. Given our increasing reliance on IP networks, there is a commensurate need for better techniques to manage them, or at least make sure that they operate well and when they don't allow us to pinpoint and fix the problems quickly. We are clearly not there, as the authors effectively illustrate, and the distributed and heterogeneous nature of IP networks is such that getting there is non-obvious and may not even be feasible without major rethinking. Spelling these issues out and clearly articulating the problems is one of the paper's strengths, as is its suggestion that a rather radical departure from how IP networks operate and are managed is needed to address this challenge. The combination of a clear and convincing exposition of the problem and of controversial viewpoint on how to address it is bound to create contention and discussions, and therefore contribute to a healthy debate on what is an important problem. This may ultimately help us craft and deploy a good solution. On the negative side, while the 4D architecture represents a novel combination of ideas and methodologies, many of its pieces echo a number of earlier attempts. As pointed out by several reviewers, systems such as SS7, the TMN architecture, or even the old SNA architecture with its use of Explicit Routes and centralized management, embody numerous previous attempts and actual systems that share many of the attributes of the 4D proposal. This naturally raises the question of why ideas that previously failed to successfully address the new environment introduced by IP networks stand a better chance in the 4D context. The authors partially address some of these issues, but the arguments are not fully convincing. This is in part because the 4D architecture is still at the conceptual level, i.e., a "research proposal" and not a solution that has been fully vetted through a complete reduction to practice, and the authors do devote a section to the disadvantages of the 4D architecture and point out that much of the work remains to be done. But the end-result is not fully successful in addressing this issue. In short, read the paper. It is on an important topic and it does a great job at spelling out the issues, and even if you ultimate disagree with what it proposes; you'll at least have a better idea for why you do.  Public review written by Roch Guérin University of Pennsylvania Today's data networks are surprisingly fragile and difficult to manage. We argue that the root of these problems lies in the complexity of the control and management planes-the software and protocols coordinating network elements-and particularly the way the decision logic and the distributed-systems issues are inexorably intertwined. We advocate a complete refactoring of the functionality and propose three key principles-network-level objectives, network-wide views, and direct control-that we believe should underlie a new architecture. Following these principles, we identify an extreme design point that we call "4D," after the architecture's four planes: decision, dissemination, discovery, and data. The 4D architecture completely separates an AS's decision logic from protocols that govern the interaction among network elements. The AS-level objectives are specified in the decision plane, and enforced through direct configuration of the state that drives how the data plane forwards packets. In the 4D architecture, the routers and switches simply forward packets at the behest of the decision plane, and collect measurement data to aid the decision plane in controlling the network. Although 4D would involve substantial changes to today's control and management planes, the format of data packets does not need to change; this eases the deployment path for the 4D architecture, while still enabling substantial innovation in network control and management. We hope that exploring an extreme design point will help focus the attention of the research and industrial communities on this crucially important and intellectually challenging area.
The authors of REF move from the consideration that today's management functions need to be mapped to the logic elements of the nodes.
A clean slate 4D approach to network control and management
CCRV
Computer Science