Some Controversial Opinions on Software-Defined Data Plane Services Fulvio Risso Dept. of Control and Computer Engineering Politecnico di Torino Torino, Italy fulvio.risso@polito.it Antonio Manzalini Telecom Italia Strategy Future Centre Torino, Italy antonio.manzalini@telecomitalia.it Mario Nemirovsky ICREA Research Professor Barcelona Supercomputing Center Barcelona, Spain mario.nemirovsky@bsc.es Abstract—Several recent proposals, namely Software Defined Networks (SDN), Network Functions Virtualization (NFV) and Network Service Chaining (NSC), aim to transform the network into a programmable platform, focusing respectively on the control plane (SDN) and on the data plane (NFV/NSC). This paper sits on the same line of the NFV/NSC proposals but with a more long-term horizon, and it presents its considerations on some controversial aspects that arise when considering the programmability of the data plane. Particularly, this paper discusses the relevance of data plane vs control plane services, the importance of the hardware platform, and the necessity to standardize northbound and southbound interfaces in future software-defined data plane services. I. I NTRODUCTION The idea of transforming the network into a programmable platform is probably one of the hottest topics in the current research domain, which originates from the impossibility to deeply change the behavior of current network devices. In fact, in most cases only the manufacturer of the network equipment has the privilege to create the software that controls the device itself, while the possibilities for any other actor (e.g., a network operator) are more limited. In fact, a network operator can only configure the software already provided by the network manufacturer (changing parameters, choosing a routing protocol instead of another, etc.) but it cannot directly install its own software on the network device, such as a routing protocol customized for its particular environment. Among the approaches that have been proposed so far toward a greater flexibility, we can cite Software-Defined Networks, Network Functions Virtualization [1] and Network Service Chaining [2]. Software-Defined Networks (SDN) rep- resent a new architectural model in which the control plane is transformed into a programmable entity and is decoupled from the data plane. Instead, Network Functions Virtualiza- tion (NFV) and the IETF Network Service Chaining (NSC) proposals can be considered fairly orthogonal to SDN and aimed at simplifying the complex data plane processing path present in network operator’s networks. Although a more in- depth discussion of SDN and NFV/NSC is left for Section II, we can summarize how SDN is more oriented to control plane programmability, while NFV/NSC focuses on data plane functions. Briefly, control plane refers to the set of functions that influence how packets are forwarded to the destination; for instance, the control plane faces the problem of managing network paths between source and destination hosts. Vice versa, data plane refers to the set of functions that can inspect, and potentially modify, the content of the packets in transit, i.e. it faces the problem of processing each single packet. This paper discusses the problem of customizing data plane services with a view limited to a single network device, and assumes that future NFV/NSC solutions will allow users to deeply change the behavior of the data path of the network, e.g., by installing and running custom applications that operate on an arbitrary portion of the network traffic. In case of such of this event, we speculate that some assumptions that may be valid for the SDN world may no longer be appropriate when deep data plane programmability comes into play. This paper presents the personal (and potentially controver- sial) opinion of the Authors on some issues related to the future software-defined data plane services, namely the importance of a programmable data vs control plane (Section III), the necessity of the network hardware to evolve (Section IV) and the necessity to define standard interfaces for future data plane services (Section V). The paper includes also an introduction to the existing SDN and NVF/NSC concepts (Section II), and a final section (Section VI) that summarizes current findings and presents some conclusive remarks. II. BACKGROUND A. Software-Defined Networks Software-Defined Networks are based on the separation between the control and the data plane of the network. The former, which is supposedly where most of the intelligence is, is transformed into an open programmable platform that can potentially host any network control application, usually provided by the network operator. This may allow different actors (e.g., network operators) to finely control the forwarding decisions taken in any portion of their network and implement the best traffic forwarding strategy according to their necessi- ties. As a consequence, SDN can enable the implementation of smart algorithms e.g., to balance traffic across different links based on several criteria such as the sender/receiver of the traffic, the application, or anything else that is considered useful for the network operator. © 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works." Risso F., Manzalini A., Nemirovsky M., "Some Controversial Opinions on Software-Defined Data Plane Services," in Proceedings of the 2013 Software Defined Networks for Future Networks and Services (SDN4FNS), Trento, IT, November 2013, DOI 10.1109/SDN4FNS.2013.6702558.